UNITED STATES DEPARTMENT OF THE INTERIOR, OscAR L. Chapman, Secretary
FISH AND WILDLIFE SERVICE, Albert M. Day, Director

AN ANNOTATED BIBLIOGRAPHY ON THE
BIOLOGY OF PACIFIC TUNAS

By Bell M. Shimada

FISHERY BULLETIN 58

From Fishery Bulletin of the Fish and Wildlife Service

VOLUME 52

UNITED STATES GOVERNMENT PRINTING OFFICE - WASHINGTON : 1951

For sale by the Superintendent of Documents, U. S. Government Printing Office, Washington 25, D. C.

Price 30 cents

CONTENTS

Page

Introduction 1

Annotated bibliography 3

Abbreviations used 25

Index by subjects 28

7^^-c':o

AN ANNOTATED BIBLIOGRAPHY ON THE BIOLOGY OF PACIFIC TUNAS

By Bell M. Shimada, Fishery Research Biologist

Studies were begun in 1948 by the Pacific
Oceanic Fishery Investigations of the U. S. Fish
and Wildlife Service to gather fundamental data
on the life histories, ecologj', and behavior of the
various species of Pacific tunas. Early in the
planning of the research program conducted from
the Hawaiian Islands, it was recognized that re-
view ajid systematic compilation of the literature
on these subjects were essential to the effective
guidance of the projected research. The principal
reference work available was the bibliography of
the tunas prepared some '20 years ago by Genevieve
Corwin (see Corwin 1930, in the Bibliogi-aphy,
p. 5). To meet the needs of the workers in the
Investigations, and to assist tuna researchers in
general, the preparation of this bibliography was
undertaken.

The bibliography deals chiefly with the black
skipjacks or little tunnies {Euthynnua aUefteratufi,
E. Uneatus, and E. yaito) , the oceanic or common
skipjack {Katsuwonus pelamis), the albacore
{Thvnmbs genno), the bluefin or black tunas
{ThimnuK viaccoyi^ T. oiicntalis, and T. tJiyn-
nus), the big-eyed tunas (Parathunnus meiachi
and P. ,siii), the yellowfin tuna {Neothunnus
jnacroptei'us), and the frigate mackerels of the
genus Auxis. Synonymous and related species
reported from the Pacific Ocean are included.
Waters contiguous to the Indo-Australian Archi-
pelago have been considei-ed as a part of the Pa-
cific Ocean proper, inasmuch as many of the
important studies of tuna sjjecies occurring in the
Pacific Ocean were based on data gathered in that
region.

In the review of the literature, some preliminary
work was done at Stanford University, Palo Alto,
and at the California Academy of Sciences, San
Francisco, California. The libraries of the Beniice
Pauahi Bishop Museum, the University of Hawaii,
and the Territoi-ial Board of Agriculture and For-
estry in Honolulu, and private collections of staff
members of the Investigations were particularly

productive of material. The Japanese references
were gathered by a reconnaissance team in Japan
from November 1948 to July 1949 investigating
the results of Japanese tuna research. Search of
private and public libraries in and about Tokyo
supplied much material that has not hitherto been
generally available outside Japan. Some refer-
ences found in Corwin's bibliography could not be
examined at first hand: these are included here,
as given hy Corwin, with a notation to show their
source.

The general style used by Corwin has been fol-
lowed in cataloging and annotating the material.
The arrangement of the references is by authors
listed alphabetically. Entry is made only under
the senior author's name if there is more than one
author; the abbreviation "et al." is used with the
senior author's name to show collaboration of more
than three authors. Each authors works are
listed chronologically by year of publication, and
those published in the same year are given in
alphabetical sequence. Generally, pagination is
given only for the parts of the publication falling
within the scope of the bibliography.

Appropriate notations in the bibliography dis-
tinguish those papers published only in Japanese,
those published in Japan but written in English,
and those jjublished in Japanese with an English
abstract. Translations were made of Japanese
titles when English equivalents were not given.

Brief annotations of the publications are in-
cluded except for those that could not be consulted
and for those whose titles give a clear indication
of the contents. The .scientific nomenclature used
by each author is followed in the annotations;
appropriate cross references to synonymous names
regarded as having priority appear in the Index.
Where both vernacular and scientific names of the
tuna were given, the scientific nomenclature is
retained.

The preparation of the Index presented consid-
erable difficulty owing to the confused state of the

FISHERY BULLETIN OF THE FISH AKD WILDLIFE SERVICE

taxonomy of the various species of tuna. As the
relationsliips of the tuna species of the Pacific, and
for that matter the world in general, have not been
clearly defined, specific names of questionable
validity have been arbitrarily indexed as separate
entries. For example, Neothunnus itosibi is re-
garded by some workers as a form distinct from
Neothunnus 7nacropterus, while others consider
the two to be synonymous. References to Neo-
thunnus ifosihi and Neothunnus jnacropte/iis,
therefore, have been treated separately. Syno-
nyms which are generally accepted as applying to
one given species, such as Euthynnus pelamis for
Katsuioonus pelamis, have been indexed under the
name which is believed to have priority, with
appropriate cross reference under the synonymous
name. The same procedure was used in indexing
names which differ slightly in spelling. Again,
it should be pointed out that the indexing of these
scientific names is to a large degree arbitrary, and
is not an attempt to clarify the systematics of the
tunas.

A list of abbreviations of the various publica-
tions cited and of the English translations of titles
of Japanese periodicals as used in the bibliography
is included.

Acknowledgment is made of the valuable assist-
ance and advice given the author by various indi-
viduals and organizations. Especially is credit
due the Fisheries Division, Natural Resources
Section, General Headquarters, Supreme Com-
mander for the Allied Powers, under W. C. Her-
rington, Drs. K. Kuronuma and Y. Hiyama, and
other Japanese scientists, and Dr. J. G. F. Harden-
burg of Batavia, Java, for their generous cooper-
ation. The author is also indebted to the library
staffs of Stanford University, the California
Academy of Sciences, University of Hawaii, and
the Bernice Pauahi Bishop Museum, and to Ver-
non Brock of the Division of Fish and Game,
Board of Agriculture and Forestry, Territory of
Hawaii, and staff members of the Pacific Oceanic
Fishery Investigations, who contributed mate-
rially to the preparation of this bibliography.

ANNOTATED BIBLIOGRAPHY

Explanation of symbols

[C] = references listed by Corwin (see Corwin 1930, p. 5) that could not be verified.

[J] —published in Japanese only.
[JE] = published in Japan but written in English.
[ Je] = written in Japanese with English abstract.

[P] = accession to the library of the Pacific Oceanic Fishery Investigations.

[For an explanation of the abbreviation see Itst, p. 25]

Abe, Tokihaku.
1939. A list of the fishes of the Palao Islands. Palao
Trop. Biol. Sta. Studies, No. 4, p. .jGT. [JE] [P]
Ocrmo macroplcrus, Kafstiiconus pelamys, Thuimus
thynnics: recorded; distribution.

AlKAWA, HiROAKI.

193.3. Fisliery conditions on the Pacific Coast for skip-
jack, tuna, and sauries. Proc. Sci. Fish. Assoc., vol.

5, No. 4, pp. 3.J4-369. [J] [P]

Alhacore, big-eyed tuna, black tuna, skipjack, yel-
lowfin tuna : fishing conditions correlated with sur-
face water temperature.

1937. Notes on the shoal of bonito along the Pacific
Coast of Japan. Bull. Japanese Soc. Sci. Fish., vol.

6, No. 1, pp. 13-21. [Je] [P]

Age analysis and size composition of skipjack
catches; stock and population relationships; use
of condition factor in separating migratory and
nonmigratory fish.
AiKAWA, Hlkoaki, and Masao Kato.

1938. Age determination of fish. I. BuU. Japanese Soc.
Sci. Fish., vol. 7, No. 2, pp. 79-88. [Je] [P]

Germo genno, Katsinconus vagans, Neothunnus
macroptenis, Tliunnus oricnfalis: age analysis using
vertebrae ; age composition of commercial catch ;
calculated length and weight groups ; body condi-
tion; growth rate; morpliometric data.
Anonymous.

1938. Status of the investigation of tuna longline fish-
ing grounds in the South China Sea. Formosa Fish.
Mag., No. 279, pp. 10-19. [J]

Alhacore, yellowfin tuna : body temperatures ; dis-
tribution ; length-weight data ; sexual maturity ;
stomach contents ; figured.

1939. Marked fish. Semi-Ann. Rpt. Oceanogr. Invest.,
No. &5, p. 137. [J]

Skipjack : Japan ; release records of tagged fish.
1941. Pacific skipjack indigenous to Sulu Sea. South
Sea Fish., vol. 7, No. 5, p. 5.5. [J] [P]
Distributional note.
-VSANO, N.\gao.

1939. Food of the alhacore, Germo germo (LacSpMe).
South Sea Fish. News, vol. 3, No. 7, pp. 10-11. [J] [P]
South Seas; stomach contents; AuxU sp. recorded
as food.

Ban, Yoshinori.
1941. Search for southern tuna fishing grounds. South
Sea Fish., vol. 7, No. 9, pp. 10-21. [J] [P]

Yellowfin tuna; South Seas; fishing conditions
correlated with oceanography ; stomach contents :
age analysis ; sexual maturity.
Barnhart, Percy.

1936. Marine fishes of Southern California. Univ. Cali-
fornia Press, Berkeley, pp. 36-37.

Auxis thazard, Katstnrotiiis pelamis, Germo ala-
liinga, Neothuniuis macroptcrits, Thiinnus thynnus:
description ; distribution ; English common names ;
figures.
Bennett, Fbedebick Debell.

1840. Narrative of a whaling voyage around the globe,
from the year 1833 to 1S36. Vol. 2, pp. 278-282.
London.

Scomber germo: description ; anatomy of reproduc-
tive system; food; enemies. Scomber pelamys:
description ; parasites.
Berg, Leo S.

1947. Classification of fishes both recent and fossil.
J. W. Edwards Co., Ann Arbor, pp. 491-492.

Anatomy and classification of Thunniformes
(Plecostei).
Bleekeb, Pieter.

1844. Bijdragen tot de geiieeskundige topographic van
Batavia. Generisch overzicht der fauna. Nat.
Geneesk. Arch. Neerland's Indie, vol. 1, p. 5.53.

Tliynnus: recorded.

1845. Bijdragen tot de geneeskundige topographic van
Batavia. Generisch overzicht der Fauna. Nat.
Geneesk. Arch. Neerland's Indie, vol. 2, p. 516.

Aiixis taso: recorded.
1850. Bijdrage tot de kennis der ichthyologische fauna
van Midden-en Oost-Java, met besehrijving van eenige
nieuwe species. Verb. Batavia Genoot. Kunst.
Wetens., vol. 23, p. 8.

Attxis taso: recorded.
1852. Bijdrage tot de kennis der makreelachtige vlsschen
van den Soenda-Moluksdien Archipel. Verb. Batavia
Genoot. Kunst. Wetens., vol. 24, pp. 36-37, 89.

Thynnus macroptenis, T. thunnina, and T. tonggol:

recorded from Dutch East Indies ; description and

synonymy of T. tonggol.

3

FISHEKT BULLErmsr OF THE> FISH AND "WILDLIFE SERVICE

Bleekeb, Pietek — Continued
ISd-t. Faunae ichthyologicae japonicae sjjecies novae.
Nat. Tijdschr. Nederlandsch-Indie, vol. 6, pp. 408-409.
Aiixis tapeinosoma : recorded and described.

1855. Vijfde bijdrage tot de kennis der ichthyologische
fauna van Ternate. Nat. Tijd.schr. Nederlandsch-
Indle, vol. 8, pp. 301-302.

Aiixis thyniiokles: recorded; description; compared
with A. tapeinosoma, A. taso, and A. vulgaris.

1856. Beschrijvingen van nieuwe en weinig bekende
vischsoorten van Amboina, versameld op eene reis
door den Molukschen Arcbipel, gedaan in bet gevolg
van den Gouverneur-Generaal Duyuiaer van Tvrist in
September en October 18.55. Act. Soc. Sci. Indo-
Neerlandicae, vol. 1, pp. 41-42.

Thyniuis prlnmys: recorded; description: syn-
onymy.
1S57. Nieuwe nalezingen op de ichthyologle van Japan.
Verb. Batavia Genoot. Kunst. Wetens., vol. 26, p. 98.

Auxis taiieinosoma: recorded.
1860a. Achtste bijdrage tot de kennis der vischfauna
van Sumatra. Vis.sehen van Benkoelen, Priaman,
Tandjong, Palembang, en Djambi. Act. Soc. Sci. Indo-
Neerlandicae, vol. 8, p. 29.

Thimnus pelamys, T. thunnina: recorded from the

Dutch East Indies.
ISGOb. Dertiende bijdrage tot de kennis der vischfauna
van Celebes. Visschen van Bonthain, Badjoa, Sindjal,
Lagoesi en Pompenoea. Act. Soc. Sci. Indo-Neer-
landicae, vol. 8, p. 38. [C]

Thnnmts tliunnina: recorded from Dutch East

Indies.
1861a. lets over de vischfauna van bet eiland Pinang.
Versl. Akad. Amsterdam, vol. 12, p. 74.

Thynnus a /finis: recorded from Dutch East Indies.
ISClb. Mededeeling omtrent visch.soorten, nieuw voor de
kennis der fauna van Singapoera. Versl. Akad. Am-
sterdam, vol. 12, p. 52. [C]

Thynnus tliunnina. T. totif/f/ol: recorded from

Singapore.

1862. Sixi&me m^moire sur la faune ichthyulogique de
rile Batjan. Versl. Akad. Amsterdam, vol. 14, p. 109.

Pelamys macroptenis, P. pelamys. Thynnus tliun-
nina: recorded from Dutch East Indies.

1863. Onzieme notice sur la fauna ichtbyologique de
I'ile de Ternate. Nederlandsch Tijdschr. Dierk., vol.
1, p. 235.

Auxis thynnoides : recorded.
1865a. :finum6ration des esp^ces de poissons actuelle-
ment connues de I'ile d'Amboine. Nederlandsch
Tijdschr. Dierk., vol. 2, p. 285.
Auxis thynnoides, Pelamys marropterus. P. pelamys,
P. tliunnina: recorded.
1865b. Sixieme notice sur la faune ichtbyologique de
Slam. Nederlandsch Tijdschr. Dierk., vol. 2, p. 173.
[C]
Thynnus thiinnina: recorded.
1878. Quatrifeme memoire sur la fauna ichtbyologique
de la Nouvelle-Guinfe. Arch. N^erlandaises Sci. Nat.,
vol. 13, p. 50.

Auxis taso: recorded.

Bleeker. Pieter — Continued

1870. Enumeration des especes de poissons actuelle-
ment connvies du Japon et description de trois especes
Inddites. Versl. Akad. Amsterdam, vol. 18, p. 15. [C]
Pelamys sihi Blkr. and Thynnus sibi Schl. com-
pared.
Boeseman, M.
1947. Revision of the fishes collected by Burger and von
Siebold in Japan. Zool. Meded., vol. 28, pp. 91-94.
Thynnus macroptcrus, T. orientalis, T. pelamys, T.
sibi, T. thunina: description; synonymy.

BONHAM, KELSHAW.

1946. Measurements of some pelagic commercial fishes
of Hawaii. Copeia, No. 2, pp. 81-84.

Katsuwonus pelamis: length-weight data and re-
lationship; length frequencies of Neothunnus mac-
ropterus; lengths of Euthynnus yaitn.
Brock, Vernon E.

1938. A new tuna record from Washington. Copeia,
No. 2, p. 98.

Thunnus thynnus: recorded.

1939. Occurrence of albacore, Oermo alalvnga, in mid-
Pacific. Copeia, No. 1, p. 47.

1943. Contribution to the biology of the albacore
(Oermo alalunga) of the Oregon coast and other
parts of the North Pacific. Stanford Ichth. Bull., vol.
2, No. 6, pp. 199-248.

Age and size composition; growth; spawning; sex

ratio; length-frequency data; population analysis.

1949. A preliminary reiiort on Paratliii units sibi in

Hawaiian waters and a key to the tunas and tuna-like

fi.shes of Hawaii. Pacific Sci., vol. 3, No. 3, pp. 271-

277.

P. sibi: description ; morphometric data ; feeding
habits. Auxis thazard, Euthynnus yaito, Qeinio
alaliiniia. Katsuwonus pelamis, Kishinoella rara,
Neothunnus macroptcrus, Parathunnus sibi, Thun-
nus orientalis, T. thynnus: key.
Cantor, Theodore.

1850. Catalogue of Malayan fishes. Jour. Asiatic Soc.
Bengal, vol. IS, pt. 2, pp. lOSS-1090.

Thynnus affinis: description; distribution; com-
pared with T. pelamys.
Castelnau, Count P. de.

1872. Contribution to the ichthyology of Australia.
Proc. Zool. Acclim. Soc. Victoria, vol. 1, pp. 104-105.
Thunnus macroyii: description.
Chabanaud, Paul M.

1926. Inventaire de la faune ichtyologique de I'lndo-
chine. Note Serv. Oceanogr. Pech. Indochine, No. 1,
p. 22.

thunnus thiinnina: listed.
Chapman, Wilbert M.

1946. Observations on tuna-like fishes in the tropical
Pacific. California Fish and Game, vol. 32, No. 4, pp.
165-170.

Euthynnus alletteratus, Katsuwonus pelamis, Neo-
thunnus macroptcrus: recorded; food of N. macrop-
tcrus noted.

BIBLIOGRAPHY ON PACIFIC TtJNAS

Che\'et, Pierke.
l!)32a. Inventaire de la fauna ichtyologique de I'lndo-
chine. Deuxi&me liste. Note Serv. Oceanogr. POch.
Indochine, No. 19, p. 26.
Euthynnus yaito: listed.
1932b. Poi.ssons des canipagnes du "de LanessMii"' (192.')-
1929). Trav. lust. Oceanogr. Indochine, 4'' Mem.,
pp. 11,'5-11,5.

Euthynnus i/aito: synonymy: distribution; descrip-
tion; Indo-Chinese common names; figure of speci-
men and scales.
1934. Revision synonymique de I'oeuvre ichtyologique
de G. Tirant. Note Serv. Oceanogr. Pech. Indochine,
No. 7, p. 46.

Thynnus thunnina listed by Tirant renamed
Euthynnus yaito.

Cnin.\ Prefecti RAi. Fisheries Experiment Station,
Katsuura Branch.

1930. Investigation of skip.lack fishing grounds. Prog.
Rpt. Chiba Pref. Fish. Expt. Sta. for 1934, pp. 1-12.

[J] [P]
Japan ; albacore and skipjaclc fishing conditions
correlated with water temperature.

1937. Investigation of skipjack fishing grounds. Prog.
Rpt. Chiba Pref. Fish. Expt. Sta., Katsuura Br. fr)r
193.^), pp. 1-9. [J] [P]

Japan ; skipjack catch correlated with water tem-
perature.

1938. The skipjack fishery. Prog. Rpt. Chiba Pref. Fish.
Expt. Sta., Katsuura Br. for 1936, pp. 2-11. [J] [P]

Japan ; skipjack catch correlated with water tem-
jierature.
1941. The skipjack fishery. Prog. Rpt. Chiba Pref. Fish.
Expt. Sta., Katsuura Br. for 193S. pp. 22-25. [J] [P]
Japan ; albacore and skipjack fl.shing conditions cor-
related with water temperature.

Cnti, Tuanting T.

1931. Index piscium sinensium. Biol. Bull. St. John's
Univ.,No. 1, pp. 107-108.

Auxis rorhei, Neothunnus nmcropterus: synonymy;
distribution.

Clark, Frances Naomi.

1929. A racial comparison of Californian, Hawaiian and
Japanese albacore (Oermo germo). California Fish
and Game, vol. 1.1, No. 4, pp. 3.51-.353. San Francisco.
Population studies based on comparisons of body
proportions, counts of raeristic characters, and sex-
ual maturity.

Clemens, W. A., and G. V. Wilby.

1946. Fishes of the Pacific Coa.st of Canada. Fi.sh. Res.
Bd. Canada, Bull. No. 4S, pp. 164-167.

Katsuwonus pdawis, Tliunnus alnlunga: descrip-
tion; distriliution ; food; records of capture in
Canadian Pacific waters ; figured.

Conn, John N.

1919. Scientific problems of the fisheries of the north
Pacific. Bull. Scripps Inst., No. 9, p. 4.5. [C]
Genno germo, Thunnus alalunga: migration.

Cooper, James Graham.

1863. On new genera and species of Californian fishes.
Proc. California Acad. Sci., vol. 3, pp. 7i>-77.
Orcynus pacificus: described as a new species; dis-
tribution ; figured.

CoRwiN, Genevieve A.

1930. A bibliography of the tunas. California Div. Fish
and Game, Fish Bull. No. 22, pp. 1-103.

("owAN, Ian M.

19.38. Some fish records from the coast ol' BritLsh Colum-
bia. Copeia, No. 2, p. 97.
Oermo nlalunga: recorded.

Craig, Joe Allen.

1929. List of common and scientific names of fishes.
California Div. Fish and Game. Fish I'.ull. No. 1."),
pp. 11-12.

Euthynnus pilumis, Oermo germo, yrollinnnus eiitn-
linae, Thunnus saliens: listed.

Cuvier, Georges, and Achiixes Valenciennes.

1831. Histoire naturelle des poissons. Vol. 8, pp. 85, 96,
107. Paris.

8eon)t)er taso, Thynmis paeificus. T. pelamys: de-
scription ; records of capture ; figure of T. pelamys.

DeJong, J. K.

1940. A preliminary investigation of the spawning hab-
its of some fishes of the Java Sea. Treubia. vol. 17.
No. 4, pp. 325-326.
Euthynnus aVitterntus: frequencies of egg diameter
measurements ; resorption of eggs noted.

Delsman, H. C.

1931. Fisli eggs and larvae from the Java Sea. Treubia.
vol. 13, Nos. .3-1, pp. 407-409.

Eggs and larvae believed to be those of Sconihrr
(Delsman, Treubia, vol. 8, Nos. 3-4, pp. 395-399)
reidentified as Thynmis thunnina.

Delsman, H. C, and J. G. F. Hardenburg.

1934. De Indische zeevischen en zeevisscherij. Blblio.
Nederlandsch Indische Nat. Ver., No. 6, pp. .330-343.
Euthjinnus alletteratiis, E. pelamys, Neothunnus
maeropterus, N. rarus: description; distribution:
key ; Malayan common names ; spawning of E. allet-
teratus and description of eggs and larvae; spawn-
ing of N. ranis and description of eggs; food of /.'.
pelamys; E. aHetteratus and .V. maeropterus figured.

Dill. D. B.

1921. .\ chemical study of certain Pacific coast fishes.
Jour. Biol. Chem., vol. 48, pp. 76, 81. [C]

Oermo alalunga, O. maeropterus, Thunnus thinniiis:
chemical analysis.

Domantay, Jose S.

1940. Tuna fishing in Southern Mindanao. Philippine
Jour. Sci.. vol. 73. No. 4. pp. 42.3-4.35.

Auxis thazard, Euthynnus yaito, Katsuwonus pela-
mis, Neothunnus itosihi. N. maeropterus, I'arathun-
nus sibi: distribution; figured.

6

FISHERY BULLEfTIN OF THE FISH AND WILDLIFE SERVICE

EcKLES, Howard H.

1949a. Fishery exploration in the Hawaiian Islands
(August to October 1948, liy the vessel Oregon of the
Pacific Exploration Company). Com. Fish. Rev., voL
11, No. 6, pp. 1-9.
Euthi/nnus yaito. Kaisuwonus pelamis, Neothunnus
macroiitenis : recorded; K. pelamis and N. macrop-
terus figured.
1949b. Observations on juvenile oceanic skipjack {Knt-
suiroiins pelamis) from Hawaiian waters and
sierra mackerel from the Eastern Pacific. U. S. Fish
and Wildlife Serv. Fish. Bull., vol. 51, No. 48, pp.
24.5-250.

Kntsiiwonus pelamis: anatomy, descriptions, fig-
ures, and records of capture of juveniles ; spawning ;
juveniles noted in stomachs of adults.

ElGENMANN, CaRL H.

1892. The fishes of San Diego, California. Proc. U. S.
Natl. Mus., vol. 15, No. 897, pp. 130, 147.

Gyninosnrda pelamys, Oreiinus alnlntuia: recorded;
seasonal occurrence of Euthynnus pelamis and O.
alalonga.

ElGENMANN, CARL H., and Rosa S. Eigenmann.

1890. Additions to the fauna of San Diego. Proc. Cali-
fornia Acad. Sci., 2 Ser., vol. 3, p. 8.

Euthynnus pelamys: recorded; description.

1891. A catalogue of the fishes of the Pacific coast of
America north of Cerros Island. Ann. New York
Acad. Sci., 1891-1892, vol. 6, p. 352.

Euthynnus pelamys, Germo alalongn: recorded.

E\'ERMANN, Barton W., and Alvin Seale.

1907. Fishes of the Philippine Islands. Bull. U. S. Bur.
Fish., vol. 26, p. 61.

Oymnosarda pelamis: listed; synonymy.

Fish, Marie Poland.

1948. Sonic fishes of the Pacific. Woods Hole Oceanogr.
Inst. Tech. Rpt., No. 2, pp. 87-91.

Aums thazard, Euthynnus, Oermo alalunga, Kat-
sttivonus pelamis, Ncothnnnns macropterus, Thun-
nns thj/nnns: distribution; English common names;
synonymy of K. pelamis, G. alalunga, T. thynnvs;
air bladders of G. alalunga, N. macropterus and T.
thynnus described; Japanese common names of
Euthynnus and T. thynnus; vertical distribution
of Parathnnnus mebachi noted.

Fitch, ,Iohn E.

1950. Notes on some Pacific fishes. California Fish and
Game, vol. 36, No. 2, p. 65.

Stomach contents of Neothunnus maeroptenis.

Food and Agriculture Organization, United Nations.

1949. Recommended scientific and common names of im-
portant food fishes. A. Scombriformes. Fish. Div.,
FAO, UN, 98 pp.

Auxis thasard, Euthynnus alletcratus. Genno ala-
lunga, Katsuwonus pelamis, Neothunnus macrop-
terus, Thunnus thynnus: distribution; synonymy;
world-wide common names and recommended
nomenclature.

Formosa Government-General Fisheries Experiment
Station.

1930. Northern oceanographic conditions and skipjack
fishing. Prog. Rpt. Formosa Govt. -Gen. Fish. Expt.
Sta. for 1928, Oceanogr. Sec, pp. 67-70. [J] [P]

Formosa; fishing conditions correlated with water
temperature, specific gravity, and currents.

1931. Northern oceanographic conditions and skipjack
fishing. Prog. Rpt. Formosa Govt.-Gen. Fish. Expt.
Sta. for 1929, Oceanogr. Sec, pp. 28-30. [J] [P]

Formosa ; fishing conditions correlated with water
temperature, specific gi-avity, and currents.

1932. Northern oceanographic conditions and skipjack
fishing. Prog. Rpt. Formosa Govt.-Gen. Fish. Expt.
Sta. for 1930, Oceanogr. Sec, pp. 10-11. [J] [P]

Formosa ; fishing conditions correlated with water
temperature, specific gravity, and currents.
1933a. Experimental fishing and investigation in south-
ern waters by the Shonan Maru. Prog. Rpt. Formosa
Govt.-Gen. Fish. Expt. Sta. for 1931, Fish. Sec, pp.
1-.50. [J] [P]

Yellowfln tuna : Indo-Pacific region ; length-weight
data ; fishing conditions in relation to oceanography
and weather ; catch per unit of effort ; distribution ;
stomach contents.
1933b. Oceanographic conditions and skipjack fishing in
northern Formosa. Prog. Rpt. Formosa Govt.-Gen.
Fish. Expt. Sta. for 1931, Oceanogr. Sec, pp. 13-15.
[J] [P]
Fishing conditions correlated with currents, surface
water temperature, and specific gravity.
1934. Oceanographic conditions and skipjack fishing in
northern Formosa. Prog. Rpt. Formosa Govt.-Gen.
Fish. Expt. Sta. for 1932, Oceanogr. Sec, pp. 10-12.
[J] [P]
Fishing conditions correlated with currents, surface
water temperature, and specific gravity.
Fowler, Henry W.

1904a. A collection of fishes from Sumatra. Jour. Acad.
Nat. Sci. Phila., 2 Ser., vol. 12, p. .506.
Germo germon: figured.
1904b. New, rare, or little-known Scombroids. Proc.
Acad. Nat. Sci. Phila., vol. 56, pp. 761-763.

Germo germon, Pelamys affine: description; syn-
onymy.
1923a. New or little-known Hawaiian fishes. Bernice P.
Bishop Mus. Occas. Papers, vol. 8, No. 7, pp. 376-392.
Germo macropterus, Thunnus thynnus: recorded.
192.3b. Records of West Coast fishes. Proc Acad. Nat.
Sci. Phila., vol. 75, p. 289.

Germo alalunga, Thunnus thynnus: recorded from
California.

1927. Fishes of the tropical central Pacific. Bull. Ber-
nice P. Bisliop Mus., No. 38, pp. 10-11.

Germo sibi: figured; description.

1928. The fishes of Oceania. Mem. Bernice P. Bishop
Mus., vol. 10. pp. 132-134.

Auxis thasiird, Euthynnus aUctteratus, E. pelamis,
Germo alhacorrs. G. alalunga, G. macropterus, G.
sibi, Thunnus thynnus: description; synonymy;
figures of E. alletteratus and G. sibi.

BIBLIOGRAPHY ON PACIFIC TUNAS

Fowler, Henry W. — Continued

1920. Notes on Japaiipse and Chinese fishes. Proc. Acad.
Nat. Sci. Pliila., vol. si, p. 590.

Gcimo sibi, Tliinnius thyntuis: seen in Japan.
1031. The fishes of Oceania - Supplement 1. Mem. Her-
nice P. Bishop Mns., vol. 11, No. 5, p. 325.

Eiithynnus allrttcratiis, E. pelamis, Onmo ahilunr/a,

O. nidcrontcnix, O. x'bi, Thunniis thiiiniiis: listed;

s.vnonymy of G. mncroptcrux.

1033. Description of a new lon.i,'-finned tmia {Semathun-

nus giiildi) from Tahiti. Proc. Acad. Nat. Sei. Phila.,

vol. ST), pp. 163-161.

De.scriptions of new genus Semafhiinnus and new
species, Scmathunnus guildi; Scmathunnux distin-
guished from Ncofhiinniis.

1934. The fishes of Oceania — Supplement 2. Mem. Ber-
niee P. Bishop Mus., vol. 11. No. 6, p. 400.

Eittliynnus peldinis, Semntlnitinus ijuildi, .S. itosili,
Thunnus orientalis, T. thynnus: listed; synonymy.

1935. The fishes of the George Vanderbilt South Pacific
Expedition, 1937. Acad. Nat. Sci. Phila., Monogr.
No. 2, pp. 31-33, 2.53, 277.

Aiixis thnxard, Eulhynuiis. Unentim. E. pclamis:
description; synonymy. A. thaznrd, Euihynnus
allctterafus, E. lineatus, E. pelamis, Qrrmo ala-
longa. Neofhunmis maoropterus. Pai-atlinnnus sibi,
Thunnus thynnus: recorded from Pacific.
1944. Results of the Fifth George Vanderbilt Expedition

(1041). Acad. Nat. Sci. Phila., Monogr. No. 6, pp.

349, 373-374, 378, 408.

Auxis thnznrd. Euthynuus lineatus, Katsuwonus
pelamis, Thunnus thynnus: records of capture;
synonymy. Pacific records of A. thazard, Euthyn-
ntis allettcratus, E. lineatus, Oermo alalunga, K.
pelamis, Neothunnus argentirittatus, and Thunnus
thynnus; description of T. thytinus; figure of E.
lineatus.
1949. The fishes of Oceania-Supplement 8. Mem. Ber-

nice P. Bishop Mus., vol. 12, No. 2, pp. 73-74.
Auxis thazard, Euthynnus wallisi, Katsuwonus
vagans, Neothunnus maoropterus, Parathunnus sibi:
listed ; synonymy.
Fowler, Henry W., and Stanley C. Ball.

1925. Fishes of Hawaii, Johnston Island, and Wake

Island. Bull. Bernice P. Bishop Mus., No. 26, p. 11.
Euthynnus alletteratus: listed.

Fraser-Brunner, a.

1949. On the fishes of the genus Euthynnus. Ann. and
Mag. Nat. Hist., vol. 2, No. 20, pp. 622-628.

Euthynnus afflnis afflnis, E. afflnis lineatus, E.
nffinis yaito: classification; distribution; figured;
key ; synonymy,
mw. The fishes of the family Scombridae. Ann. and
Mag. Nat. Hist., vol. 3, No. 26, pp. 131-163.
Allothunnus fallai, Auxis thazard, Euthynnus
afflnis, E. pelamis, Thunnus alalunga, T. albacora,
T. obestis, T. thynnus, T. tonggnl. T. zacalles:
classification ; description ; distribution ; key ; fig-
ured ; synonymy.

Fu.JiTA, K.. and Y. Wakita.
1915. A list of fishes from Kishu. Proc. Sei. Fish.
Assoc, vol. 1, No. 1, pp. 25-37. [J]

Auxis hira, A. niaru, Euthynnus yaito, Katsuwonus
pelamis, Thunnus alalunga, T. macroptcrus, T.
orientalis: listed ; Japanese common names.

FUKUDA, M., and S. Iizuka.

1940a. Experimental tima fishing. Prog. Rpt. Kuma-
moto Pref. Fisli Expt. Sta. for 1938, pp. 15-20. [J]

[P]

Big-eyed tuna, black tuna : Uyukyu Islands, catch in

relation to water temperature.
1940b. Skipjack tagging experiment. Prog. Rjit. Kuma-
moto Pref. Fish. Expt. Sta. for 1938, p. 21. [J] [P]

Japan : release records of tagged skipjack.

Gilbert, Charles H., and Edwin C. Starks.

1904. The fishes of Panama Bay. Mem. California.
Acad. Sci., vol. 4, p. 206.

Germo alalunga, Thunnus tliynnus: recorded.

GoDSiL, Harry C.

1938. Tuna tagging. California Fish and Game, vol. 24,
pp. 245-250.

Skipjack, yellowfin tuna : tagging methods and
release records.

1948. A preliminary population study of the yellowfin
tuna and the albacore. California Div. Fish and
Game, Fish Bull. No. 70, 90 pp.

Xcothunnus macropterus, Thunnus gcrmo: morpho-
metric data ; population relationships of Japanese,
Hawaiian, and California fish analyzetl ; methods
of taking morphometric measurements described.

1949. A progress report on the tuna investigations.
California Fish and Game, vol. 35, No. 1, pp. .5-9.

Albacore, yellowfin tuna : summary of population
studies based on morphometrical analysis.

GoDsiL, Harry C, and R. D. Byers.

1944. A systematic study of the Pacific tunas. C^ilifor-
nia Div. Fish and Game, Fish Bull. No. 60, 131 ppv
Kafsuiconus pelamis, Neothunnus macropterus.
Parnthunnus mehiiehi, Thunnus germo, T. thynnus:
proportional measurements; methods of measure-
ment ; internal anatomy ; key ; figures ; description ;
classification ; counts of meristic characters ;
anatomical differences between species listed ; pop-
ulation relationships discussed for all except P.
mebaehi.

GoDSiL, Harry C, and E. C. Greenhoou.

1948. Some observations on the tunas of the Hawaiian
region. California Div. Fish and Game. Bur. Mar.
Fi.sh., 8 pp. (Mimeographed.)

Albacore, black skipjack, skipjack, yellowfin tuna :
distribution.

Graham, David H.

1938. Fishes of Otago Harbour and adjacent seas with
additions to previous records. Trans. Roy. Soc. New
Zealand, vol. 68, pt. 3, p. 414.
Auxis thasard: listed.

8

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Griffin, L. T.

1927. Additions to the fish fauna of New Zealand.
Trans. New Zealand Inst., vol. 58, pp. 140-141.

Germo germo: recorded; synonymy; description;
figured.
GiJNTHER, Albert.
1860. Catalogue of the Acanthopterygian fishes in the
collection of the British Museum. Vol. 2, pp. 363-366,
369. London.

Axixis rochei, A. tapcinoxnimi. Thynnus afflnis. T.
parifirim, T. pchimiis, T. thiinnina, T. ionggnl: de-
scription; distribution; synonymy.
1876. Die Fische der Siidsee. .Tour. JIus. GodefCmy, vol.
2, pp. 1.50-152.

Thynnus germo, T. pclamyn. T. thunnina. T. thyn-
nus: synonymy; description; distribution; T. germo
and T. thunnina figured.
1889. Report on the pelagic fishes collected by H. M. S.
Challenger during the years 187.3-76. Vol. 31, pt. 78,
p. 17. London.

Juveniles provisionally identified as Thynnus thun-
nina described and figured.
HjVKADA, Isokichi.

1928. A new species of Aeanthocephala from the Japa-
nese bonito, Euthynnus vagans. Japanese Jour. Zool.,
vol. 2, No. 1, pp. 1-4. [J]

Parasites.
Hart, J. L., and H. J. Holuster.

1947. Notes on the albacore fishery. Prog. Rpt. Pacific
Coast Sta., Fish. Res. Bd. Canada, No. 71, pp. 3-4.

Albacore catch correlated with water temperature
anil area ; stomach contents.
Hart, J. L.. et al.

1948. Accumulated data on albacore (Thnnnus ala-
lunga). Pacific Biol. Sta., Ilsh. Res. Bd. Canada, Circ.
No. 12, 8 pp.

Stomach contents ; size composition ; catch corre-
lated with area, water temperature, and season.
Hasegawa, Kiichi.

1937. Progress report of experimental tuna fishing in
the waters ad.1acent to Woleai. South Sea Fish. News,
No. 1, pp. 3-7. [J] [P]
Tunas : distribution.
H.iTAi. Shinkishi, et al.

1941. A symposium on the Investigation of skipjack and
tuna spawning grounds. South Sea Sci., vol. 4,
No. 1, pp. 64-75. [J] [P]

Skip.iack : Japan, Indo-Pacific region. South Seas ;
eggs ; juveniles ; food ; migration ; sexual maturity ;
probable spawning areas and seasons ; method of
differentiating between male and female skipjack.
Black tuna: Jaiian, Philippine region; probable
spawning areas and season; sexual maturity; de-
scription of eggs. YcUowfin tuna: sexual maturity
and probable spawning season in Indo-Pacific region.
Big-eyed tuna : juveniles recorded from South Seas.
Herald, Eaul S.

1949. Pipefishes and seahorses as food for tuna. Cali-
fornia Fish and Game, vol. 35, No. 4, p. .';29.

Euthynnus yaito, yellowfln tuna: stomach contents,

Herre, Albert W.

1932. A check list of fishes recorded from Tahiti. Jour.
Pan-Pacific Res. Inst., vol. 7, No. 1, p. 3.

Euthynnus alletcraius, E. iwlnniix, Ncnihunnus ma-
croptenis: listed.
19.33. A check list of fishes from Dumaguote, Oriental
Negros, P. I., and its immediate vicinity. Jour. Pan-
Pacific Res. Inst., voL 8, No. 4, p. 7.
Euthynnus yaito, Katsmvonus pelamis: listed.

1935. A check list of the fishes of the Pelew Islands.
Mid-Pacific Mag., vol. 47, No. 2, p. 104.

Katsnirnnios prlnmis, Neothnnnus mncropterua:
listed.

1936. Fishes of the Crane Pacific Expedition. Field
Mus. Nat. Hist., Zool. Ser., vol. 21, pp. 105-107.

Katsuiconus pelamis, NcotJiunnus macropterus,
Thunnus thynnus: distribution; synonymy: obser-
vations of N. macroptcnis fin lengths noted.
1940. Distribution of the mackerpl-like fishes in the

western Pacific north of the equator. Proc. Sixth

Pacific Sci. Cong., vol. 3, pp. 211-215.

Auxis thazard, Euthynnus allcterata. E. yaito,
Oermo alalunga, KntsnioonHS pelamis, Neothunnus
macropterus, N. rarns. Parathunntts siii, Thunnus
thynnus: distribution.

Herre, Albert W., and Agustin F. Umall.

1948. English and local common names of Philippine

fishes. U. S. Fish and Wildlife Serv., Circ. 14, 128 pp.

Auxis thaxard, Etithynnus yaito. Germo ahiiunga,

Eatsuioonus pela)nis, Neothunnus macropterus:

listed.

HiGASHi, Hideo.

1940a. Utilization of fishery byproducts from the South

Seas (3). South Sea Fish., vol. 6. No. 7, pp. 13-20.

tJ] [P]

Big-eyed tuna, black tuna, skipjack, yellowfin tuna :

ratio of viscera weight to body weight.

1940b. Utilization of fishery byproducts from the South

Seas (7). South Sea Fish., vol. 6, No. 12, pp. 10-13.

[J] [P]

Skipjack ; ratio of viscera weight to body weight ;

proportional measurements of various body parts.

1941a. Utilization of fishery byproducts from the South

Seas (8). South Sea Fish., vol. 7, No. 1, pp. 33-37.

[J] [P]
Skipjack : length-weight data ; proportional meas-
urements of various body parts ; liver figured.
1941b. Utilization of fisliery liyproducts from the South
Seas (10). South Sea Fish,, vol. 7, No. 3. pp. 32-39.

[J] [P]

Katxuu-onus r'agans, Neothunnus macropterus: pro-
portional measurements of various body parts ; ag ,
analysis. I

1941c. Utilization of fi.shery byproducts from the South
Seas (14). South Sea Fish., vol. 7, No. 8, pp. 30-43.

[J] [P] I

Big-eyed tuna, yellowfin tuna : length-weight data ; i
proportional measurements of various body parts ;
livers figured.

BIBLIOGRAPHY ON PACIFIC TUXAS

9

llKiAsni, Hideo — Continued
1942. Record of experimer.ts on flslies of the South
Seas. South Sen Fish., vol. S, No. 11, pii. i:?-27.

[J] [P]
Kutxiiiconiis vagans, Ncothiinniis macroptcni.i,
Parathunniis siii: len.sth-weight data; proportional
measurements of various body parts.

Hic.AsHi, HiDKo, and Ma,s.\o Hirai.
1!)48. The nicotinic acid content of flsh. Contrib. Cent,
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[Jk]
Sldpjack, yellowfln tuna : nicotinic acid content of
various body parts.

Hii.ur.nRAND, Samuki, F.

1940. A descriptive catalog of the shore fishes of Peru.
U. S. Natl. Mus., Bull. 189, pp. 361-372.
Eiithynnus alleterata, Katsuwomtg pclamis, Tlnin-
tiiis iiiacroptenis: classification; description; syn-
onymy; distribution; food; key. Thininiis (jermo,
2'. thynnus: key; occurrences recorded.

HiBATStJKA, HiTosHi, and Kaku.ji Imaizumi.

19.34. Experimental fishing and investigation in south-
ern venters. Prog. Rpt. Formosa Govt. -Gen. Fish.
Expt. Sta. for WSC'. Fish. Sec, pp. 97^164. [.I] [P]
Yellowfln tuna : Indo-Pacific region ; length-weight
data: fishing eoiulitions in relation to oceanography
and weather; catch per unit of effort; distribution.
HiBATsuKA, HiTosni, and Kiyoji Ito,

1934. Rep<irt on experimental tuna fishing in the Celebes
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for 1934, pp. 1-2S. [J] [P]

Yellowfin tuna ; length-weight data ; fishing condi-
tions in relation to oceanography and weather;
catch per unit of effort; distribution.
HiRATstrivA, HiTosHi, and Seiichi Mobxta.

193."). Correlation between length and weight of yellow-
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IPl

IIol.DEl;, CHART.es FliKDERICK.

1912. The fishes of the Pacific coast. Pp. l.'5-42. New
York.

Thininus ahilmif/fi, T. macriiptvnix, T. iiidciildtus,
T. tJiynnus: distribution ; figures of all except '/'.
macropterus.

HuBBS, Carl L.

1916. A second record of the scombroid fish Gcrmo
tiiacroptcriis fr(mi the coast of California. Copeia,
No. 38, p. 93.
1928. A check-list of the marine fishes of Oregon and
Washington. Jour. Pan-Pacific Res. Inst., vol. 3, No. 3,
p. 12.

Gcrmo alalungn : Oregon; recorded.

Ietiisa, Satoru.
19.39. Catch of tunny in the seas south of Kyushu. Bull,
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'J'Inniinis oriotl'tlis: catches correlated with water
temperature.

IKEBE, KENZO.

19.39. On the age of yellowfln tuna talcen in Palau
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[J] [P]
Length-weight data ; body condition : sexual ma-
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1940a. Age and measurements of tunas in Palau waters.
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Big-eyed tuna, yellowfin tuna : length-weight data ;
age analysis of yellowfin tuna based on size groups.
19401). Measurements of yellowfin tuna taken south of
the Marshall Islands. South Sea Fish. News, vol. 4,
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Length-weight (lata ; age analysis ba.sed on size
groups.
1940e. Measurements of albacore and yellowfin tuna
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Length-weight data ; age analysis.
1940d. Investigation of tunas in I'alau waters. South
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Catch of yellowfin tuna correlated with currents.
1941a. Measurements of yellowfin tuna from the Equa-
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Length-weight and ago data ; a.ge composition of
catches noted.
1941b. A contribution to the study of tuna spawning
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South Seas ; probable tuna spawning grounds ;

length-weight and age data of Immature yellowfin

tuna.

1942. Report of the investigation of tuna fishing in tlie

Timor, Arafura, and Banda Seas. South Sea Fi.sh.,

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Big-eyed tuna, yellowfin tuna; fishing conditions
correlated with oceanography.
iKEBE. Kenzo, and Takeshi Matsimoto.

1937. Progress report on exiierimental skipjack fishing
near Yap. South Sea Fisli. News. No. 4, pp. .3-9.

[J] [P]

Skipjack : length-weight data ; sex and body condi-
tion recorded.
Imaizumi, Kakuji.

1937. An account of the investigation of tuna fishing
grotnids in the East Philippine Sea. Formosa Fish.
Mag.. No. 271, pp. 0-23. [J] [P]

Albacore, big-eyed tuna, yellowfin tuna: catch per
unit of effort; distribution; sexual maturity of
yellowfln tuna.

IMAMI'RA. YUTAIvA.

1949. The skipjack fishery. Text Fish., vol. 6. pp. 17-
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Aiixis hira, A. mam, Euthijnniis yaito: Japan;
description; distribution; ha'bits. KatsuHonus
pchimiH: Japan; anatomy; description; distribu-
tion ; migration ; spav.ning areas and season ; food ;
populations; habits; natural enemies; fishing con-
ditions in relation to oceanography.

10

FISHERY BULLErriN OF THE FISH ANI> WTLDLIFE SEEVICB

INANAMI, YOSHITUKI.

1940a. Relationship of viscera weight to body weight in
yellowfin tuna. South Sea Fish. News, vol. 4, No. 2,
pp. 2-7. [J] [P]
1940b. Tuna fishing conditions and currents along the
eastern coast of the Palau Islands. South Sea Fish.
News, vol. 4, No. 2, pp. 7-10. [J] [P]

Big-eyed tuna, yellowfin tuna : fishing conditions
correlated with currents.
1940c. Oceanography and fishing conditions in central
Palau waters. South Sea Fish. News, vol. 4, No. 3,
pp. 5-7. [J] [P]

Big-eyed tuna, yellowfin tuna : fishing conditions
correlated with currents and water color.
1941. Oceanographlc changes and fishing conditions in
Palau waters. South Sea Fish. News, vol. 5, No. 2,
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Skipjack, yellowfin tuna : fishing conditions corre-
lated with water temperature, currents, salinity.
1942a. Oceanographlc conditions and yellowfin tuna
fishing grounds in South Sea Island waters. South
Sea Fish. News, vol. 6, No. 1, pp. 2-5. [J] [P]

Location of fishing grounds correlated with cur-
rents, transparency, water color, and water tem-
perature.
1942b. Skiiijaek fishing conditions in Saipan, Truk, and
Ponape. South Sea Fish. News, vol. 6, No. 1, pp. 5-7.

[J] [P]

Seasonal fluctuations in commercial catch ; size
composition.
1942c. Small skipjack caught at Truk. South Sea Fish.
News, vol. 6, No. 1, p. 7. [J] [P]

Records and measurements of juveniles.
1942d. Report of grounds fished by tuna boats ojier-
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Albacore, big-eyed tuna, skipjack, yellowfin tuna :
fishing conditions correlated with water tempera-
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Japanese Bureau of Fishemes.

193.3. Report of the southern fisheries investigation for

1931. Bur. Fish., Min. Agr. and For., Japanese Imp.
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1934. Report of the southern fisheries investigation for

1932. Bur. Fish., Min. Agr. and For., Japanese Imp.
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Big-eyed tuna, yellowfin tuna : Indo-Pacific region ;
distribution ; catch correlated with water tempera-
ture and transparency ; stomach contents of yellow-
fin tuna.

1935. Report of the southern fisheries investigation for

1933. Bur. Fish., Min. Agr. and For., Japanese Imp.
Govt., 298 pp. [J]

19.39. Results of encouragement given to the exploitation
of albacore fishing grounds during 1938. Bur. Fish.,
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[J] [P]
Albacore : mid-Pacific region : morphometric data ;
stomach contents ; catch correlated with water tem-
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eyed tuna : catch correlated with water tempera-
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Japanese Bttkeat: of Fisheries — Continued

1940. Results of encouragement given to the exploitation
of albacore fishing gi-ounds during 1939. Bur. Fish.,
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Albacore : mid-Pacific region ; morphometric data ;
Stomach contents ; catch correlated with water tem-
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effort ; distribution.
1942. Results of encouragement given to the exploitation
of albacore fishing grounds during 1940. Bur. Fish.,
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Jenkins, Glivter P.

1903. Report on collections of fishes made in the Ha-
waiian Islands with descriptions of new species. Bull.
U. S. Fish. Comm. for 1902, vol. 22, p. 441.

Auxis thaxard, Ginnnosarda alletterata, G. pelamis;
listed ; synonymy.

Jordan, Davto Starr.
1885. A list of the fishes known from the Pacific coast
of tropical America, from the Tropic of Cancer to
Panama. Proc. U. S. Natl. Mus., vol. 8, No. 24, p. 373.
Orcynus alalonga: recorded.
1923. A classification of fishes including families and
genera as far as known. Stanford Univ. Publ., Univ.
Ser., Biol. Sci., vol. 3, No. 2, pp. 179-180.
Classification and synonymy of Thunnidae.

Jordan, David Starr, and Barton Warren Eveemann.
1896. A check-list of the fishes and fish-like vertebrates
of North and Middle America. Rpt. U. S. Fish Comm.
for 1895, p. 340.
Auxis tliaxard, Ocrmo ahilunga, Gymnosarda pela-
mis, Thynnus thynnus: distribution; English com-
mon names ; synonymy.
1905. The aquatic resources of the Hawaiian Islands.
I. The shore fishes of the Hawaiian I.slands, with a
general account of the fish fauna. Bull. U. S. Fish
Comm. for 1903, vol. 23, pt. 1, pp. 171-175.
Atixis thaxard, Germo gcrmo, Oyiunosarda allet-
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onymy; Hawaiian common names for all except
A. thasard.
1926a. A check-list of the fishes of Hawaii. Jour. Pan-
Pacific Res. Inst., vol. 1, No. 1, p. 8.

KulhynvKS yaito, Germo germo, KisliinoeUa rara,

Ncothminus macroptenis, Neothunnus n. sp., Para-

thiinnus sibi, Thunnus oricntalis: recorded.

1926b. A review of the giant mackerel-like fishes,

tunnies, spearfishes, and swordfishes. Occas. Papers

California Acad. Sci., No. 12, pp. 8-25.

Germo germo, KisliinoeUa rara, K. zacalles n. sp..
Neothunnus catalinae n. sp., JV. itosibi n. sp., N. ma-
eropteriis, N. tonggol, Purathunniis sibi, Thunnus
maccoyii, T. orientalis, T. phiUipsi n. sp., and T.
saliens n. sp. : keys ; description ; distribution ; syn-
onymy of G. germo, P. sibi, T. maccoyii, T. orien-
talis; Japanese common names of ^. rara, N. itosibi,
N. macropterus ; figures of G. germo, K. zacalles, N.
catalinae, N. itosibi, N. macropterus, P. sibi, T.
phillipsi, T. saliens.

BIBLIOGRAPHY ON PACIFIC TITN-AS

11

Jordan, David Starr, and Chari.es Henry Gii3ERt.

1881a. Descriptions of two new sijecies of scopelid
fishes (Sudis ringens and Myctophum crciiuUire) from
Santa Barbara Channel, California. Proc. U. S. Natl.
Mus., vol. .3, p. 273.

Specimens fonnd in food of Orcynus alalonga.
1881b. List of the fishes of the Pacific coast of the
United States, with a table showing the distribution
of the six-cies. Proc. U. S. Natl. Mus., vol. 3, p. 456.
Orri/niiK alnloniia : recorded.
1882. Notes on the fishes of the Pacific coast of the
United States. Proc. U. S. Natl. Mus., vol. 4, p. 45.
Orcynus alalonga: distribution; synonymy; habits;
food.
Jordan, David Starr, and Carl Leavitf Hubbs.

1925. Record of fishes obtained by David Starr Jordan
in Japan, 1922. Mem. Carnegie Mus., vol. 10, No. 2,
pp. 21.5-221.

Aiixis hira, A. tapcinosoma, EutJiynniis yaito,
Oenno germo, Kalsuwotiiis vagans. Kisliinoella
ram, Xcothunnus macroptcnis, Parathnnnus sibi,
Thunnus oi'ientalis: recorded; descriptions of A.
hira, A. tapcitioaoma, G. gcnno, K. rara. N. marrop-
tenig, P. sibi and T. orientalis; synonymy of A.
tapcinosoma, E. yaito, Gf. germo, N. niacropterus,
P. sibi, and T. orientalis; Japanese common names
of all but A. hira and E. yaito; key to Katsuwonidae
and Thunnidae.
Jordan, David Starr, and Eric Knight Jordan.

1922. A list of the fishes of Hawaii, with notes and
descriptions of new species. Mem. Carnegie Mus., vol.
10, No. 1, pp. 31-33.
Aiixis thazard, Euthynnus allctcratus, E. pclamis,
Germo alalunga, O. aryentivittatus, G. macroptcnis,
O. sibi, Thinniiis orientalis, T. thynniis: listed;
descriptions of G. alalunga, O. macropicrits, O. sibi,
and T. orientalis ; Hawaiian common names of E.
alleteratus, E. pelamis, and G. macropterus.
.Jordan, David Starr, and Charles Metz.

1913. A catalog of the fishes known from the waters of
Korea. Mem. Carnegie Mus., vol. 6, No. 2, p. 26.
Anxis thazard: Japanese common names; distribu-
tion.
Jordan, David Starr, and Alvin Seale.

1906. The fishes of Samoa. Bull. U. S. Bur. Fish., vol.
25, p. 228.

Auxis thazard, Germo germo, O. macropterus,
Oymnosarda ullctcrata, G. pelamis: distribution.
Jordan, David Starr, and J. O. Snybeb.

1900. A list of fishes collected in Japan by Kelnosuke
Otaki, and by the United States Steamer .\lbatross,
with descriptions of fourteen new species. Proc.
U. S. Natl. Mus., vol. 22, p. .352.

Axixis thazard and Thunnus schligelt: listed.

1901. A preliminary check list of the fishes of Japan.
Annot. 2yool. Jap., vol. 3, pts. 2 and 3, p. 64.

Avxis tapcinosoma, Germo macropterus, (1. sibi,
Oymnosarda afflnis, Q. allctcrata, Thunnus schle-
geli: listed ; Japanese common names.

Jordan, David Starr, and Edwin Chapin Stabks.

1007. Notes on fishes from the island of Santa Catalina,
southern California. I'roc. U. S. Natl. Mus., vol. 32,
pp. 69-70.

Germo macropterus: records; synonymy; descrip-
tion; figured. O-ymnosarda pelamis: distribution.

JORnAN, David Starr, S. Tan.\IvA, and J. O. Snyder.
1913. A catalojme of the fishes of Japan. Jour. Coll.
Sci., Imp. Univ. Tokyo, vol. 33, art. 1, pp. 119-121.
Auxis thasard, Euthynnus alleteratus, E. vagans,
Thunnus alalunga, T. macropterus, T. thynnus:
synonymy ; distribution ; Japanese common names ;
A. thazard and E. alleteratus figured.

Kaooshima Pbefectural Fisheries Experiment Station.

1925. Experimental skipjack fishing. Prog. Ept. Kago-

shima Pref. Fish. Expt. Sta. for 1923, pp. 1-37. [J]

[P]

Ryukyu Islands ; skipjack fishing conditions corre-
lated with water temperature; length-weight, girth
data.
1926a. Experimental skipjack fishing. Prog. Rpt. Kago-
shima Pref. Fish. Expt. Sta. for 1924, pp. 1-51. [J]

[P]
Ryukyu Islands; skipjack fishing conditions corre-
lated with water temperatures ; length-weight and
girth data ; records and de.seriptions of scombroid
juveniles (also reported in Kishinouye, 1926).
1926b. Experimental longline fishing for tuna. Prog.

Rpt. Kagoshima Pref. Fish. Expt. Sta. for 1924,

pp. 52-66. [J] [P]

Big-eyed tuna, skipjack, yellowfin tuna : Ryukyu
Islands ; catches correlated with water tempera-
ture.
1927a. Experimental longline fishing for tuna. Prog.

Rpt. Kagoshima Pref. Fish. Sta. for 1925, pp. 38-53.

[J] [P]
Albacore, big-eyed tuna, black tuna, yellowfin tuna :
Ryukyu Islands ; catches correlated with water
temperature.
1927b. Experimental skipjack fishing. Prog. Rpt. Kago-
shima Pref. Fish. Expt. Sta. for 1925, pp. 1-38. [J]

[P]
Ryukyu Islands ; skipjack fishing conditions corre-
lated with water temijerature and currents ; length-
weight and girth data ; records and descriptions
of scomliroid juveniles (also reported in Kish-
inouye 1926).
1928a. Experimental skipjack fishing. Prog. Rpt. Kago-
shima Pref. Fish. Expt. Sta. for 1926, pp. 1-22. [J]

[P]
Ryukyu Islands ; skipjack catch correlated with

water temperature and currents; length-weight and

girth data ; release reccu'ds of tagged fish.

1928b. Experimental longline fishing for tuna. I'rog.

Rpt. Kagoshima Pref. Fish. Expt. Sta. for 1926, pp.

22-37. [J] [P]
Albacore, big-eyed tuna, black tuna, yellowfin tuna :
Ryukyu Islands; catches correlated with water
temperature.

12

FISHEKY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Kagoshima Pkefectural Fisheries Experiment Sta-
tion — Continued
1929a. Experimental sliipjack fishing. Prog. Rpt. Kago-
shima I'ref. Fish. Expt. Sta. for 1927, pp. 1-20. [J]

[P]

Ryuliyu Islands ; skipjack catch correlated with

water temperature; length-weight and girth data.
1929b. Experimental longline fishing for tuna. Prog.
Rpt. Kagoshima Pref. Fish. Expt. Sta. for 1927, pp.
20-34. [J] [P]

Big-eyed tuna, yellowfin tuna : Ryukyu Islands ;

catches correlated with water temperature.
1930a. Experimental skipjack fishing. Prog. Rpt. Kago-
shima Pref. Fish. Expt. Sta. for 1928, pp. 1-18.

[J] [P]

Ryukyu Islands; skipjack catch correlated with

water temperature.
1930b. Experimental longline fishing for tuna. Prog.
Rpt. Kagoshima Pref. Fish. Expt. Sta. for 1928, pp.
18-31. [J] [P]

Albacore, big-eyed tuna, yellowfin tuna : Ryukyu

Islands ; catches correlated with water temperature.

1930c. Experimental fishing l)y small motor vessels :

Experimental longline fishing for albacore. Prog. Rpt.

Kagoshima Pref. Fish. Expt. Sta. for 1928, pp. 54-60.

[J] [P]
Albacore, big-eyed tuna, black tuna, yellowfin tuna :
Ryukyu Lslands ; catches correlated with water
temperature.
1931a. Experimental skipjack fishing. Prog. Rpt. Kago-
shima Pref. Fish. Expt. Sta. for 1929, pp. 1-lG.

[J] [P]
Ryukyu Islands ; skipjack catch correlated with wa-
ter temperature.
1931b. Experimental longline fishing for tuna. Prog.
Rpt. Kagosliima Pref. Fish. Expt. Sta. for 1929, pp.
16-.30. [.I] [P]

Albacore, big-eyed tuna, yellowfin tuna : Ryukyu
Islands ; catches correlated with water temperature.
1932a. Experimental skipjack fishing. Prog. Rpt. Kago-
shima Pref. Fish. Expt. Sta. for 1930, pp. 1-20.

[J] [P]
llyukyu Islands ; skipjack fishing conditions corre-
lated with water temperature.
19.32b. Experimental longline fl.shing for tuna. Prog.

Rpt. Kagoshima Pref. Fish. Expt. Sta. for 1930, pp.

21-28. [J] [P]

Albacore, big-eyed tuna, black tuna, yellowfin tuna :
Ryukyu Islands ; catches correlated with water
temperature.
1932c. Exiierimental longline fl.shing for albacore and

pole and line fishing for mackerel. Prog. Rpt. Kago-

.shima Pref. Fish. Expt. Sta. for 1930, pp. 54-59.

[J] [P]
Ryukyu Islands ; albacore catch correlated with wa-
ter temperature.

Kagoshima Pretectural Fisheries Experiment Sta-
tion — Cont inued
1933a. Investigation of skipjack fishing. Prog. Rpt.
Kagoshima Pref. Fish. Expt. Sta. for 1931, pp. 1-16.
[J] [P]
Ryukyu Islands, Philippine region ; skipjack fishing
conditions correlated with water temperature.
1933b. Experimental longline fishing for tuna. Prog.
Rpt. Kagoshima Pref. Fish. Expt. Sta. for 1931, pp.
16-23. [J] [P]

Albacore, big-eyed tuna, yellowfin tuna : R.Mikyu
Islands ; catches correlated with water tempera-
ture.

19.35. Investigation of skipjack fishing. Prog. Rpt.
Kagoshima Pref. Fish. Expt. Sta. for 1933, pp. 1-12.
[J] [P]
Ryukyu Islands ; skipjack fishing conditions corre-
lated with water temperature.
1936a. Investigation of skipjack fishing. Prog. Rpt.
Kagoshima Pref. FLsh. Expt. Sta. for 1934, pp. 1-16.
[J] [P]
Ryukyu Islands ; skipjack fi.shing conditions corre-
lated with water temperature ; length-weight data.
1936b. Investigation of the migration of important
fishes. Prog. Rpt. Kagoshima Pref. Fish. Expt. Sta.
for 1934, pp. 86-87. [J] [P]

Ryukyu Islands ; release records of tagged skipjack.
1937. Investigation of skipjack fishing. Prog. Rpt.
Kagoshima Pref. Pish. Expt. Sta. for 1935, pp. 1-8.
[J] [P]
Ryukyu Islands; skipjack catch correlated with
water temperature ; length-weight data ; size com-
position of catch.
1938a. Investigation of skipjack fishing. Prog. Rpt.
Kagoshima Pref. Fish. Expt. Sta. for 1936, pp. 1^.
[J] [P]
Ryukyu Islands ; skipjack length-weight data.
193Sh. Investigation of the migration of important
fishes. Prog. Rpt. Kagoshima Pref. Fish. Expt. Sta.
for 1936, p. 89. [J] [P]

Ryukyu Islands ; release records of tagged skipjack.
1939a. Investigation of skipjack fishing. Prog. Rpt.
Kagoshima Pref. Fisli. Expt. Sta. for 1937, pp. 1-3.
[J] [P]
Ryukyu Islands ; skipjack length-weight data.
1939b. Investigation of the migration of important
fishes. Prog. Rpt. Kagoshima Pref. Fish. Expt. Sta.
for 1937, p. 69. [J] [P]

Ryukyu Islands ; release records of tagged skipjack.
1940a. Experimental .skipjack fishing. Prog. Rpt.
Kagoshima Pref. Fish. Expt. Sta. for 1938, pp. 1-3.
[J] [P]
Ryukyu Islands; skipjack length-weight data.
1940b. Investigation of the migration of important
fishes. Prog. Rpt. Kagoshima Pref. Fish. Expt. Sta.
for 1938, p. 43. [J] [P]

Ryukyu Islands; release records of tagged skipjack.

BIBLIOGRAPHY ON PAaFIC TUNAS

13

Kaooshima Prefectural Fisheries Experiment Sta-
tion — Continued
1941. Investigation of skipjaclc fishin;^. I'ro^:. Kpt.
Kagoshima Pref. Fish. Expt. Sta. for 1939, pp. 1-3.
[J] [P]
Ryuk.vu Islands ; skipjack length-weight data.
Kaxamura, Ma.sami, and Kakuji Imaizumi.

1935. Report on pxp<>rimental fishinir by tlio Shonan
Maru in 1935 : Report of exijerimenlal longline fl.shing
for tuna in eastern Formosan waters. Formosa
Govt.-Gen. Fish. Expt. Sta. Publ., No. 3, pp. 165-202.
[J] [P]
Big-eyed tuna, yellowfln tuna : length-weight data ;
body temperatures : sexual maturity ; catch per
unit of effort ; fishing conditions in relation to
oceanography and weather ; distribution.
KANAMfBA. Masami, and Hauuo Yazaki.

1940a. Report on experimental fishing by the Shonan
Maru in 1937 : Investigation of tuna longline fishing
grounds in the East Philippine Sea. Formosa Govt.-
Gen. Fish. Expt. Sta. Publ., No. 21, pp. 1-G5. [J] [P]
Albacore, big-eyed tuna, skipjack, yellowfin tuna :
catch iJer unit of effort: distribution of yellowfln,
big-eyed tuna, and skipjack : yellowfln tuna : stom-
ach contents ; body temperature and relation to
water temperature ; length-weight data : body con-
dition; age analysis; sexual maturity; flsliing con-
ditions in relation to oceanography and weather.
1940b. Report of tlie investigation of fishing grounds by
the Shonan Maru in 1937: Investigation of tuna long-
line fishing grounds in the South China Sea. Formosa
Govt.-Gen. Fish. Expt. Sta. Publ., No. 21, pp. 67-117.
[J] [P]
Albacore, skipjack, yellowfin tuna : distribution ;
catch per unit of effort : fishing conditions in rela-
tion to oceanograpliy and weather : albacore, yel-
lowfln tuna: stomach contents; body temperature;
length-weight data; body condition; age analysis;
sexual maturity.
Kato, Genji.

1940. An account of longline flshing for tuna. South
Sea Fish. News. vol. 4, No. 7, pp. S-10. [J] [P]
Sexual maturity of yellowfln tuna noted.
Kawamira. Hyozo.
1939. Observations on oceanography and fisliing condi-
tions in Palau waters. South Sea Fish. News, vol. 3,
No. 1, pp. 2-6. [.T] [P]

Fishing conditions for yellowfin tuna and skipjack
correlated with oceanography.
Kawana, Takeshi.

1934. Tuna fishing in relation to oceanographic condi-
tion.s. Prog. Rpt. Hokkaido Fish. Expt. Sta., vol. 31,
pp. 1-180. [J] [P]

Tln)}iiiiis orioitalis: Japan; flshing conditions cor-
related with astronomical and oceanographic fac-
tors ; tagging ; size composilion of commercial catch.
1937. The catch of tunny. Tliutinus oricntiilis T. and S.,
off Kushiro, Hokkaido, in relation to the vertical
difference in water temperature. Bull. Japanese Soc.
Sci. Fish., vol. 6, No. 2, pp. 73-74. [Je] ll'J

KiDA. Takeo.

193(>. On the surface temperature of water in the tunny

flshing grounds off Kushiro and Urakawa in summer.

Bull. Japanese Soc. Sci. Fish., vol. 5, No. 2, pp. 87-90.

[Je]

Thjinnus thj/'inii'i: fishing conditions correlated

with water temperature ; size composition of

schools ; habits.

KiMfltA, Kl.NOSUKE.

1932. Growth curves of blue-fin tuna and yellow-fin tuna
based on the catches near Sigedera, on the west coast
of I'rov. Idu. Bull. Japanese Soc. Sci. Fi.sh., vol. 1,
No. 1. pp. 1-4. [Je] [PJ

Ncotliiinntis inacroptrnis, T h u ii n u n orioitalis:
growth rates determined from size groujis.
1935. Statistical analy.sis of the catch by keddle nets,
along the coast of Surugu Bay. Rec. Oceanogr. Works,
vol. 7, No. 1, pp. 1-.3G. [JE]

Growth of Ncothiinnus macroptcnis ; age and size
groups of Thunnus orient a! if.
1941. Skipjack fishing. Fish. Technol. Lect. .Ser., No. 4,
36 pp. [J]

Pacific Ocean ; distribution ; migration ; catch corre-
lated with water temperature : age and size composi-
tion of commercial catches.
1942a. Tuna and spearfish fishing conditions. Fish.
Technol. Lect. Ser., No. 5, 122 pp. [J]

Albacore, big-eyed tuna, yellowfin tuna : Japan,
Indo-Pacific region. South Seas : fishing conditions
correlated with water temperature; age and size
composition of albacore and yellowfin tuna.
1942b. Oceanic resources : Offshore fisheries. Sci. Sea,
vol. 2, No. 3, pp. 142-147. [J] [P]

Albacore, black tuna, skipjack : Pacific Ocean ; dis-
tribution : migration ; distribution of big-eyed tuna
and yellowfin tuna.
1949. Atlas of skipjack fishing grounds — with data on
the albacore grounds. Kuroshio Publ. Co., Tokyo,
44 pp. [J]

Japan ; catches of albacore and skipjack correlated
with surface water temperature.
KiMuitA, KiNosuKE, aud Kazimi Ishii.

1933. Statistical analy.sis of the catch at the north-
eastern end of Surugu Bay. Bull. Japanese Soc. Sci.
Fish., vol. 2, No. 2, pp. 69-79. [Je]

Catches of yellowfin tuna correlated with water
temperature.

KlSHINOUYE, KaMAKICIII.

1895. Food of tunas and bonitos. Zool. Mag., vol. 7,
p. 111. [J]

191,5a. Studies on the mackerels, cybiids, and t\uias.
Proc. Sci. Fish. Assoc, vol. 1, No. 1, pp. 1-24. [J] [P]
Auxis hira n. sp., A. maru n. sp., Eiithi/iiiiiis yaito
n. sp., Katsmconus pelamys n. sp., Thunnus ala-
lunga, T. macroptcnis, T. mebachi a. sp., T. oricn-
talis. T. rarus n, sp, : internal anatomy ; classifica-
tion ; description ; distribution ; keys ; Japanese com-
mon names; figures; spawning of T. orioitalis and
A. maru; food and habits of tunas in general.

14

FISHEKT BULLErriN OF THE FISH ANiD WILDLIFE SERVICE

KisHiNOUYE, Kamakichi — Continued

1915b. Anatomical aspects of darli muscle. Proc. Sci.
Fish. Assoc, vol. 1, No. 2, pp. 12S-136. [J] [P]
Albacore, big-eyed tuna, black skipjack, black tuna,
frigate mackerel, Ncoihunntis rariis, skipjack, yel-
lowfin tuna : anatomy and vascular system of lat-
eral musculature described ; figured in part for all
except big-eyed tuna and N. rams.
1917a. A new order of tbe Teleostomi. Proc. Sci. Fish.
Assoc, vol. 2, No. 2, pp. 1-4. [J] [P]

Classification; description of internal anatomy of
order Plecostei and families Tliunnidae and
Katsuwonidae.
1917b. The food of tunas. Proc Sci. Fish. Assoc, vol.
2, No. 1, pp. 106-108. [J] [P]

Albacore, big-eyed tuna, skipjack, yellowfin tvina :

stomach contents ; juvenile albacore, big-eyed tuna,

skipjack, and Auxis inaru recorded from stomachs

of adults.

191S. Amount of blood in the dark muscle and other

muscles of the Plecostei. Proc Sci. Fish. Assoc, vol.

2, No. 3, pp. 259-260. [J] [P]

Blood content of dark lateral muscle of big-eyed
tuna and skipjack compared.
1919a. Studies on the Plecostei. Proc. Sci. Fish. Assoc,
vol. 2, No. 4, pp. 269-274. [J] [P]

Evolution of various tuna species based on internal
anatomy ; vascular system and anatomy of lateral
musculature of Thunnidae and Katsuwonidae ; and
vascular plexuses of albacore, big-eyed tuna, black
skipjack, black tuna, frigate mackerel, skipjack,
and yellowfin tuna figured.
1919b. The larval and juvenile stages of the Plecostei.
Proc. Sci. Fish. Assoc, vol. 3, No. 2, pp. 49-53. [J]

[P]

Black skipjack, black tuna, skipjack : western
Pacific ; juveniles recorded and described ; markings
of young Scombroid fishes mentioned ; Liitken's
"albacore" juveniles and Giinther"s "black skip-
jack" juvenile described and figured.

1919c. Black skipjack from Mexico. Proc Sci. Fish.
Assoc, vol. .3, No. 2, p. 113. [J] [P]

Eiithjfniius lineatus: Mexico; recorded and de-
scribed as a new species.

1921. Tunas of the American coast. Proc Sci. Fish.
Assoc, vol. 3, No. 3, p. 2.39. [J] [P]
Anatomical differences between American bluefln
tuna and .Japane.se black tuna noted.

1922a. Air bladders of Thunnidae. Proc. Sci. Fish.
Assoc, vol. 3, No. 4, p. 304. [J] [P]

Albacore, big-eyed tuna, yellowfin tuna : air-blad-
ders described ; recorded and described for black
tuna.

1922b. Carangid-like markings of skipjack. Proc. Sci.
Fish. Assoc, vol. 3, No. 4, pp. 304-305. [J] [P]

Unusual markings on one specimen recorded and
described.

1922c. Black skipjack also found in Japan Sea. Proc
Sci. Fish. Assoc, vol. 3, No. 4, p. 305. [J] [P]
Distribution record.

KisHiNOUYE, Kamakichi — Continued

1923. Contributions to the comparative study of the so-
called Scombroid fishes. Jour. Coll. Agr., Imp. Univ.
Tokyo, vol. 8, No. 3, pp. 293^75. [P]

Au.ris hira, A. mam, Euthynnns lineatus, E. yaito,
Katsitioonus pelamis, Neothunnus macropterus, N.
rams, Paratliunnus mcbachi, Thinnuis ffcrnio, T.
orientalis: anatomy; bibliogi-aphy : classification;
description ; distribution ; figures ; food ; habits ;
keys ; Japanese common names ; synonymy ; growth
of N. macropterus, T. germo, T. orientalis; enemies
of T. orientalis; migration of K. pelamis, T. germo,
T. orientalis ; i>arasites of E. yaito, K. pelamis, N.
macropterus, P. niebnchi; spawning of E. yaito, K.
pelamis, N. macropterus, T. orientalis; young of
.4. mam, E. yaito, K. pelamis, T. germo, T. orientalis.

1924. Observations on skipjack fishing grounds. Proc.
Sci. Fish. Assoc, vol. 4, No. 2, pp. 87-92. [J] [P]

Auxis maru, Euthynnus yaito, Katsuwonus pelamis,
INeothunnus macropterus: Ryukyu Islands; rec-
ords and descriptions of juveniles.
1926. An outline of studies of the Plecostei (tuna and

skipjack) in 1925. Proc. Sci. Fish. Assoc, vol. 4,

No. 3, pp. 125-137. [J] [P]
Auxis sp., Katsuwonus pelamis, INeothunnus ma-
cropterus, "iParathunnus meiachi: Ryukyu Islands ;
juveniles recorded, described, and figured.

KiTAHAKA, T.

1897. Seombridae of Japan. Jour. Imp. Fish. Bur.,
Tokyo, vol. 6, pp. 1-3. [C]
Tliynnus germo, T. m.acropterus, T. pelaniys, T. .<sihi,
T. thunnina, T. thynnus: figures.

KOCHI PREFECTtni.\L FISHERIES EXPERIMENT STATION.

1923a. Oceiinographic observations and search for skip-
jack fishing grounds. Prog. Rpt. Kochi Pref. Fish.
Expt. Sta. for 1921, pp. 1-i. [J] [P]

Japan ; skipjack fishing conditions correlated with
oceanographic factors.
192.3b. Oceanographic observations and search for tuna
fishing grounds. Prog. Rpt. Kochi Pref. Fish. Expt.
Sta. for 1921, pp. 5-15. [J] [P]
Albacore, big-eyed tuna, yellowfin tuna : Japan ; mi-
gration ; vertical distribution.
1924. Oceanographic observations and search for tuna
fishing grounds. Prog. Rpt. Kochi Pref. Fish. Expt.
Sta. for 1922, pp. 39-49. [J] [P]
Albacore, big-eyed tuna, black tuna, yellowfin tuna :
Japan ; migi-ation ; vertical distribution.
KoDAMA, Masaharu, Kiyoshi Iizuka, and Toshi Harada.
1934. Weight ratio of various body parts and analyses
of the normal constituents of fresh flesh of important
South Sea fish. Prog. Rpt. Formosa Govt. -Gen. Fish.
Expt. Sta. for 1932, Technol. Sec, pp. 1-6 [J] [P]
Skipjack and tuna examined.

KUMAMOTO PrEFECTURAL FISHERIES EXPERIMENT STATION.

1946. Experimental pole and line fishing for skipjack.

Prog. Rpt. Kumamoto Pref. Fish. Expt. Sta. for 1942,

1943, 1944, pp. 3-5. [J] [P]

Ryukyu Islands ; skipjack fishing conditions corre-
lated with water temperature.

BIBLIOGRAPHY ON PACIFIC TUNAS

15

KUNfATA, T., BTT AL.

1!I41. Illustrated atlas of edible marine animals and
plants of the South Seas. Nissan Fish. Kes. Sta.,
Odawara, pp. 62-G5. [J]

Ktitfiuiconus V a g a n s, Xeothuntius macroittnus,
Parathunnus mehachi: distribution; English and
Japanese common names ; fisures : Dutch and Ma-
layan common names of li. macroptcrus and P.
mehachi

KfROXUMA, KATSUZO.

1940. A young of ocean sunfish, Mola nioln. taken from
the stomach of Germo yprmo, and a specimen of
Masturus Janccolatus as the second record from Jap-
anese waters. Bull. Biogeog. Soe. Japan, vol. 10, No.
2, pp. 2ij-28. [JE]

Stomach contents of Oermo germo noted.

IjACEPfeDE. Bernard Gebmaine Etienne.

1829. Histolre naturelle des poissons. Tome III. In:
Oeuvres du C!omte de Lac^iiede. Vol. 7, pp. 278, 285-
320. Paris. [C]

Lesson, Ren^ Pkimev{:re.

1S30. Voyage autour du monde, exfcut^ par order du
roi, sur la corvette de sa majeste. "La Cocinille",
pendant les ann^es 1S22, 1823, 1824, 1825. Zoologie,
vol. 2, pt. 1, pp. 162-166. Paris. [C]

Thynnus varans: description ; distribution ; figuied.

Lord, Clive.

1927. A list of the fi.shes of Tasmania. Jour. I'an-Pacific
Res. Inst., vol. 2, No. 4, p. 15.
Auxis thaeard, Tliunmis maceoyi: listed.

Lutken, Christian Frederick.

1880. Spolia Atlantica. Vidensk. Selskr. Skr.. 5 Ser.,
vol. 5, No. 11, pp. 460-483, 59.5-597 (Fi-ench resume).

Classification and synonymy of Orcytius spp. and
TInnuius spp. ; juveniles of O. germo described and
figured.

Macleat, William.

1881. Descriptive catalogue of Australian fishes, vol. 1,
pp. 191-192. Sydney. [C]

Thynnus affiinx, T. maceoyi, T. priamti.i: descrip-
tion ; distribution.

Manter, Harold W.

1940. Digenetic treraatodes of fishes from the Galapagos
Islands and the neighbouring Pacific. A. Hancock
Pacific Exised., vol. 2, No. 14, p. 448.

Oymnosarda aUctterata and G. peUimis listed as
hosts.

Marr, John C.

1948. Observations on the spawning of oceanic skipjack
(Kdtxiiwoniis prhimis) and yellowfin tuna (Nrothun-
niix marropirr)i.f) in the Northern Marshall Islands.
U. S. Fi.sh and Wildlife Serv. Fish. Bull., vol. 51, No.
44, pp. 201-206.

Kdimtironug pcla/inis: Marshall Islands; records

and descriptions of juveniles ; ova measurements.

K. pelamis, Ncothuniiiis macroptcrus: spawning;

length, sex. maturity data.

920179°— 51 2

Mark, John C, and Milner B. Schaefee.

1949. Definitions of body dimensions used in describ-
ing tuna.s. U. S. Fish and Wildlife Serv. Fi.sh. Bull.,
vol. 51, No. 47, pp. 241-244.
Martin, Claro.

193S. Tuna fishing and long-line fishing in Davao Gulf,
Philippines. Philippine Jour. Sci., vol. 67. No. 2. p.
189.
Katsutvonus pelamis, Neolhunnus iiosibi, N. mac-
ropterus: listed in commercial catch.
.Marikawa, Hisatoshi.
1939. Fisheries of the South Sea Islands: Natural food
of skipjack and tunas. South Sea Fish., vol. 5, No.
7, pp. 12-14. [J] [P]

Yellowfin tuna: stomach contents; juveniles of
Auxis Ihasard, Katsuwonus pelamis, and Parathun-
nus sibi mentioned as food of tunas.

MaTSIBARA. KlTOMATStl.

1943. Southern fishes. Formosa Fish. Mag., No. 334, pp.
11-14. [J] [P]

Albacore, big-eyed tuna, black tuna, yellowfin tuna :
South Seas ; distribution ; yellowfin tuna : descrip-
tion : skipjack : distribution ; migration ; sexual ma-
turity in Indo-Pacific region ; size difference between
South Seas and Japanese skipjack.
Matsui, Kizo.

1942a. Growth, water and fat content of the brain of
skipjack and tuna. South Sea Sci., vol. 5, No. 1, pp.
106-116. [J] [P]

Skipjack and yellowfin tuna.
194211. On the gonads of skipjack from the adjacent
waters of Palau. South Sea Sci., vol. 5, No. 1, pp.
117-122. [J] [P]

Gonad weight used as a criterion of sexual matu-
rity : gonads figured.
Matsusioto, Takeshi.

1937. An investigation of the skipjack fishery in the
waters of Woleai Island. South Sea Fish. News, No.
3, pp. 2-4. [J] [P]

Release of tagged skipjack recorded; migration.
McCt'i.i.ocH, Alan R.

1922. Check list of the fishes and fish-like animals of
New South Wales. Part III. Australian Zool., vol. 2,
pt. 3, pp. 104-105.

Auxis ramjiayi. A. thaeard, Eufhynnus alletterata,
E. pelamis, Thunnus germo, T. maceoyi: listed;
synonymy; key; figures of A. thazard, E. pelamis,
and T. maceoyi.

Meek. Seth E., and Samuel F. Hildf.brand.

1923. The marine fishes of Panama. Part I. Publ.
Field Mus. Nat. Hist., vol. 15, No. 215. pp. 314-316.

Auxis thazard, Germo alalunga, Gymnosarda alle-
terata, O. pelamis, Thunnus thynnus: description;
distribution; key: synonymy.
Metz, Charles Wilson.

1912. The fishes of Laguna Beach, Calif. I. Ann. Kpt.
Laguna Marine Lab., vol. 1, p. .32. [C]
Germo alalunga, Thunnus thunnus: recorded.

16

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

MiE Prepectural Fisheries Experiment Station.

1930a. Investigation of skipjacli fishing grounils and
guidance in fishing. Prog. Rpt. Mie Pref. Fish. Expt.
Sta. for 1027, pp. 1-15. [J] [P]
Japan ; skipjaclv fishing conditions correlated with
water temperatures and specific gravity.
1930b. Skipjack fishing and oceanographic conditions.
Prog. Rpt. Mie Pref. Fish. Expt. Sta. for 1927. pp.
15-17. [J] [P]

Japan ; skipjack fishing conditions correlated witli
water temperature and specific gravity.
19.30c. Investigation of tuna fishing grounds and guid-
ance in fishing. Prog. Rpt. Mie Pi'ef. Fish. Expt. Sta.
for 1927, pp. 18-33. [J] [P]

All)acore, big-eyed tuna, black tuna, yellowfln tuna :
Japan ; fishing conditions correlated with water
temperature and specific gravity.
1930d. Investigation of skipjack fishing grounds and
guidance in fishing. Prog. Rpt. Mie Pref. Fish. Expt.
Sta. for 1928, pp. 1-18. [J] [P]
Japan ; skipjack fishing conditions correlated with
water temperature and specific gravity.
1930e. Investigation of tuna fishing grounds and guid-
ance in fishing. Prog. Rpt. Mie Pref. Fish. Expt. Sta.
for 1928, pp. 19-33. [J] [P]

Albacore, big-eyed tuna, black tuna, yellowfin tuna :
Japan ; fishing conditions correlated with water
temperature and specific gravity.
MiGiTA, M., and K. Arak.\wa.

1948. Melanophorhormone of fishes. Contrib. Cent.
Fish. Expt. Sta. Japan (1946-1948), No. 39, pp. 241-
244. [Je]

Frigate mackerel, skipjack, Thiiniius orient alls,
yellowfin tuna : melanophorhormone content of
pituitary glands tabulated ; proportional weights of
various parts of T. oricntalis brain ; brain of yellow-
fin tuna figured.
Mine, Tatsdzo, and Satoku Iehisa.

1940. Appearances of the groups of Tlmnnus oricntalis
(T. and S.) in the seas south of Kyushu. Bull. Japa-
nese Soc. Sci. Fish., vol. 8, No. G, pp. 292-294. [Je] [P]
Size composition of commercial catch.

MiYAMA, YOSHIMICHI, and ISAMU OSAKABE.

1938. On the character of the fats obtained from the
various bodily parts of fishes. Bull. Japanese Soc.
Sci. Fish., vol. 7, No. 2, pp. lO.j-106. [Je] [P]

Kutsiiwoniis vaijnitn. Pardthunnus sibi, Thininiis
orientalis: chemical analysis of fats.
194f). Note on the vitamin oil contained in the liver of
fishes. Bull. Japanese Soc. Sci. Flsli., vol. 9, No. 1,
pp. 16-20. [Je] [P]

Big-eyed tuna, black tuna, skipjack, yellowfin tuna :
chemical analysis of liver and liver oil.
MiTAMA, YOSHIMICHI, KuMAN Saruya, and Takayoshi
Hasegawa.

1939. On the characters of the fats obtained from vari-
ous body parts of fi.sh. III. Bull. Japanese Soc. Sci.
Fish., vol. 8, No. 4, pp. 18.5-186. [ Je] [P]

Tlmnnus macroptcrus: South Seas; chemical analy-
sis of various body parts ; length-weight data, sex,
and stomach contents of specimens recorded.

Miyauchi, Saichi.

1915. Chemical studies of the dark lateral muscle. Proc.
Sci. Fish. Assoc, vol. 1, No. 1, pp. 38-49. [J]
Albacore, big-eyed tuna, black skipjack, black tuna,
skipjack: chemical analyses of flesh and dark
muscle.

Mori, Tamezo.

1928. A catalogue of the fishes of Korea. Jour. Pan-
Pacific Res. Inst., vol. 3. Xo. 3, p. 5. [Je]
Auxis thazard, Thminiis orientalis: listed.

Nakamura, Hiroshi.

1935. t'ber intersexualitiit bei Katsiiironus pelnmis
(Linn.). Trans. Nat. Hist. Soc. Formosa, vol. 25,
No. 141, pp. 197-198. [J]

Example of hermaphroditism recorded and de-
scribed.

1936. On the food habits of yellowfin tuna, Neofhnmuis
macroptcrus (Schlegel), from the Celebes Sea. Trans.
Nat. Hist. Soc. Formosa, vol. 2S, No. 148, pp. 1-8.
[J] [P]

Analyses of stomach contents ; length-weight data.
1938. Preliminary report on the habits of tlie black tuna,

Thumuis orientalis ( Schlegel ) . Zool. Mag., vol. 50, No.

5, pp. 279-281, pis. 1-8. [J] [P]

Description and figure of matui-e egg; gonads fig-
ured : distribution ; sexual maturity ; spawning
areas and season.
1939a. Notes on the differences between Neothunnus

macroptcrus and Neothunnus itosiii. Formosa Fi.sh.

Mag., No. 288, pp. 27-.32. [J] [P]

Neothunnus macroptcrus: classification; niorpho-
metric data ; synonymy ; Neothunnus compared with
Semathiinnus.
1939b. Report on the investigation of Thunnidae in

Formosan waters. Formosa Govt.-Gen. Fish. Expt.

Sta. Publ., No. 13, pp. 1-15. [Je] [P]
Auxis hira, A. maru, Eiitlii/nnus yaito: classifica-
tion; Japanese common names; synonymy. Katsu-
wonus pclaniis, Kishinoclla rara, Neothunnus
macroptcrus, Parathunnus mchachi, TItunnus germo,
T. 0)v'e«<a/is; classification ; description; distribu-
tion; synonymy; Japanese common names; figures
of all except N. macroptcrus, P. mehacM, and T.
germo. N. macroptcrus: spawning; morphometric
data ; compared externally with N. itosihi and Sema-
thiinnus gitildi. K. rara compared externally with
K. xacalles; spawning of 2'. orientalis.
1941. On the body temperatures of s(mie species of

Thunnidae and Istiophoridae. Proc. Sci. Fish. Assoc.,

vol. 8, No. 3, 4, pp. 25G-263. [J] [P]

Yellowfin tuna : Formosa ; body temperatures cor-
related with water temperatures.
1943. Tunas and spearfishes. Sci. Sea., vol. 3, No. 10,

pp. 445^59. [J]

Neothunnus macroptcrus, N. rarus, Parathunnus
mebaohi, Thunnus germo, T. orientalis: classifica-
tion ; distribution ; food ; Japanese common names ;
migration ; spawning.

BIBUOGRAPHY ON PACIFIC TUXAS

17

NAKAMfRA. HlROSHI — CoiltilUlod

1940. Tunas and tuna fishing. Takeuehi Bookstore.
Tokyo, April, 194',), lis pp. (JJ [I']

Oermo gcrmo, Ncathunnui macroptcni.i. .Y. ninis,
Paratliunnus mcbachi, I'hunnus oricntalis: bibli-
ography ; anatomy ; classification ; description ;
distribution; food; habits; keys; figures; Japanese
common names ; synonymy ; migration of G. gcrmo
and T. oricntnlia ; spawning of .V. macropicrux,
T. orientalis; description of T. orioitalis eggs; O.
ffcrmo, y. macrupti rus, P. mehachi; catch per unit
of effort ; fishing conditions in relation to ocean-
ography.

Nakamiira Research Stafi-.

1940. Report of the investigation of skipjack and tuna
resources. Cent. Fish. Expt. Sta. Rpt., No. 1 (for
1947), 7 pp. [J]

Katsuwonus pclamis: Japan; morphometrie data;
counts of meristic characters ; size composition
and sex ratio of commercial catch ; sexual maturity ;
stomach contents ; gonad weights ; egg counts.

Nichols, John Treu.dwell. and Francesca R. LaJIonte.
1041. Yellowfin, Allison's and related tunas. Ichth.

Contrib. Internatl. Game Fish Assoc, vol. 1, No. 3,

pp. 27-32.

Neothunmis albacora, X. alUsoni, N. catalinae, N.
rarus; classification; description: English common
names ; key ; synonymy ; provisional subspecies,
\cothiinnus aJbnrara athncora, N. alhacora ma-
cropterus, N. alUsoni allisani, N. allisoni itosibi,
and A'', rarus zacalles, proposed.

Nichols, John Teeadwell, and Robeet Cttshman
Murphy.
1922. On a collection of marine fishes from Peru. Bull.
American Mus. Nat. Hist., vol. 46, art. 0, pp. 503, 507.
Gcrmo arrjcntirittattis: Peruvian common name;
description.
1944. A collection of fishes from the Panama Bight,
Pacific Ocean. Bull. American Mus. Nat. Hist., vol.
83, art. 4, p. 240.

Katsuwonus pdumis: listed.

OiTA Prefectural Fi.siieries Experiment Station.
1925. Experimental tuna fishing. Prog. Rpt. Oita Pref.
Fish. Expt. Sta. for 1924, pp. 37-106. [J] [P]
Albacore, big-eyed tuna, skipjack, yellowfin tuna :
Ryukyu Islands: morphometrie data.
1927a. Experimental tuna fishing. Prog. Rpt. Oita Pref.
Fii?h. Expt. Sta. for 1925, pp. 1-56. [J] [P]
Albacore, big-eyed tuna, black tuna, yellowfin tuna :
Ryukyu Islands ; morphometrie data ; body tem-
peratures correlated with water temperature.
1927b. Exijerimental longline fishing for tuna. Prog.
Rpt. Oita Pref. Fish. Expt. Sta. for 1926, pp. 1-54.
[Jl [P]
Big-eyed tuna, yellowfin tuna: Ryukyu Islands;
morphometrie data.

Oita Prefectur.^l Fisheries Experiment Statio.v — Con.
1030. Report of experimental tuna fishing in the Kantfi
region. Prog. Rpt. oita Pref. Fish. Expt. Sta. for
1927. pp. 1-10. [J] [I'l

Big-eyed tuna, black tuna, yellowfin tuna : central
Japan : morphometrie data ; body temperatures cor-
related with water temperatures : fishing conditions
in relation to oceanography and weather.

Okada, Yakhiro, and Iviyomatsu Matsiib.^ra.

1038. Keys to the fislies and fish-like animals of Japan.
The Sauseido Co. Ltd.. Tokyo, pp. 140-l.-)(). [J]
Aiixis him, A. tnpcinosontn. Euthiinnux aUcttcnitun,
E. i/aito, Gcrmo pcrxio, Katsvwonus var/aiis, Kislii-
noella vara, Neothii7i>iiis itosibi, N. macroptcnis,
I'aratliunnus sibi, 'Jltunniis orientalis: classifica-
tion ; description ; distribution ; key ; Japanese com-
mon names.

Oka.moto, Gorozo.

1940. On the composition of shoals of "katsuo" Euthyn-
nus vagans (Lesson) in the northeastern Japanese
waters as anal.yzed by the body weight. Bull. Japa-
nese Soc. Sci. Fish., vol. 9, No. 3, pp. 100-102. [Je]
[P]
Size and age composition.

Okinawa Prefectur-ivl Fisheries Experiment Station.
1931. Investigation of the maturity of skipjack. Prog.
Rpt. Okinawa Pref. Fish. Expt. Sta. for 19.30. pp. 106-
107. [J] [P]

Skipjack length-weight data ; gonad weight and
maturity.
1940a. Experimental skipjack fishing. Prog. Rpt. Oki-
nawa Pref. P'ish. Expt. Sta. for 1939, pp. 3-5. [J]
[P]
Ryukyu Islands: skipjack catch correlated with air
and water temperatures.
1940b. Experimental tuna fishing. Prog. Rpt. Okinawa
Pref. Fish. Expt. Sta. for 19.30, pp. 6-8. [J] [P]
Bi.sr-eyed tuna, black tuna: Bonin Islands; catches
correlated with water temperature.
1943. Exijerimental skipjack fishing. Prog. Rpt. Oki-
nawa Pref. Fish. Expt. Sta. for 1941, pp. 4-14. [J]
[P]
Ryukyu Islands : distribution of skipjack : catch
correlated with air and water temperatures.

Okuda, Tuzuru.

191S. Some studies in marine chemistry. I'roe. Sci.
Fish. Assoc, vol. 2, No. 3, pp. 19,3-204, [J] [P]
Chemical analysis of dark muscle of frigate mack-
erel and skipjack.

Okuma, Yasvmichi, Kakt-ji iMAizr.Mi, and Juko Maki.

19.35. Investigation of South Sea fisheries by the Shonan

Maru : Investigation of tuna fishing grounds. Prog.

Rpt. Formosa Govt.-Gen. Fish. Expt. Sta. for 1933,

Fish. Sec, pp. 120-123. [J] [P]

Yellowfin tuna: Iiido-Pacific region; distribution;
stomach contents; length-weight data; sexual ma-
turity; fishing conditions in relation to oceanog-
raphy and weather ; catch per unit of effort.

18

FISHERY BULLETIN OF THE FISH ANiD WILDLIFE SERVICE

Omori. Kageyu, and Takeshi Fujimoto.
1940. Experimental longllne fishing for tuna. Prog.
Rpt. Nagasaki Pref. Fish. Expt. Sta. for 1938, pp.
175-214. [J] [P]

Big-eyed tuna, black tuna: .Japan; catches corre-
lated with water temperature and specific gravity.
O.MORI, Kageyu, and Mas^nobu Fukuda.

1938. Experimental longllne fishing for tuna. Prog.
Rpt. Nagasaki Pref. Fish. Expt. Sta. for 1936, pp.
47-^8. [J] [P]

Big-eyed tuna, bhick tuna: Japan; catches corre-
lated with water tempfrature and si>eclfic gravity.

1940. Experimental longllne fisliiiig for tuna. Prog.
Kpt. Nagasaki Pref. Fish. Expt. Sta. for 1937, pp. 45-
92. [J] [P]

Big-eyed tuna, black tuna: Japan; catches eoiTe-
lated with water temperature and specific gravity.

Onodera, Matsuji.

1941. The relation of freshness and condition factor of
Palau Islands skipjack to the ratio of finished prod-
ucts. South Sea Fish. News, vol. 5, No. 2, pp. 7-17.

[J] [P]

Skipjack length-weight data ; body condition of

fish.

Otaki, Keinosuke, Tsunenobu Fujita, and Tadashi

HlGFRASHI.

1903. Fishes of Japan; an account principally of eco-
nomic species. 1903-1904. Tokyo. [C]
Thunnus sohlegeli: Japan; figured.
Oya. Takeo, and Totoo Takahashi.

1936. On the growth accelerating substance in the liver
of the marine animals. Bull. Japanese Soc. Sci. Fish.,
vol. 5, No. 3, pp. 192-194. [Je] [P]
Growth hormones in skipjack livers.

Phillipps, W. J.

1927a. A check-list of the fishes of New Zealand. Jour.
Pan-Paciflc Res. Inst., vol. 2, No. 1, p. 14.
Eiithniniiig jH'lamis, Germo germon: listed.
1927b. Bibliography of New Zealand fishes. New Zea-
land Mar. Dept. Fish. Bull., No. 1, pp. 45-46.

Ocrino germo, Ealsuwonns pelamis, Thunmis phil-
lippsi: listed; classification; synonymy; New Zea-
land and Maori common names.
Phillips, W. J., and E. R. Hougkinson.

1922. Further notes on the edible fishes of New Zealand.

New Zealand Jour. Sci. Technol., vol. 5, No. 2, p. 93.

Oermo. germo, Gyiiinosarda pelamis: recorded.

Powell, A. W. B.

1937. Slarine fishes new to New Zealand ; including the
description of a new species of Halieutaea. Trans.
Roy. Soc. New Zealand, vol. 67. pt. 1, p. 80.
Neothunnns itosibi: recorded ; synonymy ; descrip-
tion ; figured.
Reeves, Cora D.

1928. A catalogue of the fishes of Northeastern China
and Korea. Jour. Pan-Pacific Res. Inst., vol. 2, No. 3,
p. 8.

Auxis tapeinogoma, A. thazurd, Katsuivoniis vagans,
Neothunnus niaeropterus, Thunnus oricntalis: listed.

Richardson, John.

1S40. Report on ichthyology of the seas of China and
Japan. Rpt. British Assoc. Adv. Sci., 15th meeting,
pp. 267-268.

Thynnus macroptenis, T. orientalis, T. pelamys, T.
sibi, T. tJninniiia: synonymy; distribution.

RoEDEL, Phil M.

1948a. Common marine fishes of California. California
Dlv. Fish and Game, Fish Bull. No. 68, pp. 59-63.
Kaf sine onus peJamis, Neothunnus niaeropterus,
Thunnus germo, T. thijnnus: classificatiou ; descrip-
tion; distribution; English common names; key;
figures; anatomical differences between I'arathun-
nus nicbachi and T. germo and between P. mebachi
and N. macropterus noted.
1948b. Occurrence of the black skipjack {Euthpnnus
lineatus) off southern California. California Fish
and Game, vol. 34, No. 1, p. 38.

Roughly, T. C.

1916. Fishes of Australia and their technology. Tech.
Edue. Ser., Technol. Mus. Sydney, No. 21, pp. 10, 162,
164-165.

Germo germo, Gymnosarda pelamis: distribution.
Thunnus maccoyi : classification; description; dis-
tribution; habits; figure.

Samson, V. J.

1940. Notes on the occurrence of albacore Oermo al-
alunga in the North Pacific. Copeia, No. 4, p. 271.

Sasaki, Takeo.

1939a. The relationship between oceanograpluc condi-
tions and skipjack fishing grounds in Northeastern
waters. Miyagl Pref. Fish. Expt. Sta., March, 1939,
12 pp. [J] [P]

Skipjack fishing conditions correlated with water
temperature ; migration ; size composition of schools.
1939b. The relationship between oceanographic condi-
tions and albacore fishing grounds east of Cape No-
jima. Miyagi Pref. Fish. Expt. Sta., April 1939, 14 pp.

[J] [P]

Albacore fishing conditions correlated with water
temperature ; migration ; size composition of schools.

SCAGEL, 11. F.

1949. Report on the investigation of albacore. Pacific
Biol. Sta., Fish. Res. Bd. Canada, Circ. No. 17, 23 pp.
Thunnus aUilunga: Northwest Pacific; catch corre-
lated with oceanographic conditions ; size composi-
tion of commercial catch; .stomach contents: tag-
ging; body temperatures.

SCHAEFER, MiLNER B.

194Sa. Morphometrlc characteristics and relative
growth of yellowfin tunas (Neothunnus maeropterus)
from Central America. Pacific Sci., vol. 2, No. 2, pp.
114-120.

Morphometrlc data; length-weight relationship:
growth ; classification based on variations in dorsal
and anal fin length discussed.

BIBLIOGRAPHY ON PACIFIC TUNAS

19

ScHAEFEB, MiLNER B. — Continued

1948b. Size composition of catches of yellowfln tuna
{Ncothunntts macroiiterus) from Central America,
and ttieir signiflcancp in the determination of growth,
age, and schoolini; liabits. U. S. Fish and Wldlife
Serv. Fisli. Bull., vol. 51, No. 44, pp. 107-200.

Size composition of commercial catch ; sexual ma-
turity ; age ; growth ; schooling habits ; length-
frequency data from mixed school of skipjaclc and
yellowfln tuna.
194,Sc. Spawning of Pacific tunas and its implications
to the welfare of the Pacific tuna fisheries. Trans.
Tliirteenth North Amer. Wildlife Conf.. pp. 3Clj-.S71.
Au.iiti sp., i:utli!iiinus Uncntiis, E. i/nito, Kntmi-
icniiKS pclaniix, ?i'eoihunnus macropteriis. Thiinnus
gerino: Pacific Ocean; distribution: review of rec-
ords and observations on spawning and juveniles ;
management problem.
ScHAF.FER. MiLNER B., and .7. C. Mark.

194^ia. Spawning of yellowfln tuna (Ncothminiis mn-
croptei-Kx) and sliipjaek {Kutsiiicoiuif! pdamis) in
the Pacific Ocean off Central America, with descrip-
tions of juveniles. U. S. Fish and Wildlife Serv. Fish.
Bull., vol. 51, No. 44, pp. 187-195.

\cof)iiiiituis macropterus: size composition in com-
mercial catch: sexual maturity; spawning. Katsu-
woniis pelamis: sexual maturity; .spawning; rec-
ords of capture, descriptions, and figures of N.
macropterus and K. pehimis juveniles.
1948b. Juvenile Eiiih!i))nus liiieatus and Atixix tluiznrd
from the Pacific Ocean off Central America. Pacific
Sci.. vol. 2, No. 4, pp. 262-271.
Anatomy, counts of meristic characters, descrip-
tion, figures, and records of capture of juveniles.
Schmidt, P.

1930. A check-list of the fishes of the Riu-Kiu Islands.
Jour. Pan-Pacific Res. Inst., vol. 5, No. 4, p. 3.
EHthynnus allcteratus: listed.
ScHMiTT, Waldo L.. and Leonard P. Schultz.
1940. List of the fishes taken on the Presidential Cruise
of 1938. Smithsn. Misc. Collect., vol. 98, No. 25, p. 3.
Eiithynnus aUcttcratus, E. lineatiis: listed and com-
pared.
ScHULTZ, Leonard P.
1949. .\ further contribution to the ichthyology of
Venezuela. Proc. U. S. Natl. Mus., vol. 99, pp. 1-211.
Tliiiiiniis thi/iniiix: listed; synonymy; English and
Venezuelan common names.
SCHULTz, Leox.\ed p., and Allan C. DeLacy.

1936. A catalogue of the fishes of Washington and
Oregon with distrilnitional records and a bibliog-
raphy. Mid-Pacific Mag., vol. 49, No. 1, pp. 70-71.
(Icnno alali(iif/n. ThioiniDs thynntis: synonymy;
distributional records.
Se.\le, Alvin.

1940. Report on fishes from Allan Hancock Expp<Utions
in the California .\cademy of Sciences. A. Hancock
Pa(ifi<' Kxped., vol. 9. No. 1. pp. 17-18.

EiitlniniiHs lincdtiis, Katsiiii-oinis prlawis, Neo-
thinniK.f macropterus: description; records of
capture.

Ser\e.ntt, D. L.
1941. Tlie Australian tunas. Council Sci. and Indust.
Res., Australia, Pamphlet No. 104, pp. 1-48.

Anris tltnxiinl, EiitliynnuK ntlctteratus, Katsuiconus
pelairus, Kishinoclla toiiiK/ol, Neothunnus macrop-
teruK, Thunnus gcniio. T. maccoiji: distribution,
description, key, figures, Australian common
names ; size groups, migi-atiou, and spawning of T.
maceoyi; length-weight relationship, and internal
and external differences of K. tonyijol and T. mac-
coy! compared; livers (if K. toiif/yot and T. maceoyi
figured.
1942a. Notes on the economics of the northern tuna
{Kishiiioelln tonyyol). Jour. Council Sci. and In-
dust. Res., Australia, vol. 15. No. 2, pp. 94-100.

Distribution; feeding habits; stomach contents;
spawning.
1942b. The tuna Ki-ihinoclla toiiyfjol Bleeker in Aus-
tralia. Jour. Council Sci. and Indust. Res., Australia,
vol. 15, No. 2, pp. 101-112.

Distribution ; description ; ratios of various body
proiiortions ; internal anatomy ; synonymy ; com-
pared with Kishinoella zacallcs, Neothunnus rams,
TJuninus nicoJsoni, Thynnus tongyol ; figures of T.
tono'jol and Kixhinoettn tonygol; cranium of K.
tonggol figured.

1947. A report on commercial tuna trolling tests in
southeastern Australia. Jour. Council Sci. and In-
dust. Res., Australia, vol. 20, No. 1, pp. 1-16.

KatKuironus pelamis, Thunnus germo, T. maccoyii:
recorded in catch ; catch per unit of effort, and
size composition of T. maccoyii.

1948. AJIothuntius fallai a new genus and species of tuna
from New Zealand. Rec. Canterbury Mus., vol. 5,
No. 3, pp. 131-135.

Classification ; description ; morphometric measure-
ments ; internal anatomy of type specimen ; records
of specimens and occurrences ; compared with
Katsuwonidae ; type specimen, liver, gill rakers
figured.
Shapiro, Sidney.
194Sa. The Japanese tuna fislieries. SCAP Nat. Re-
sources Sec. Rpt. No. 104, 00 pp.

Katsuiconus pelamis, Neothunnus macropterus,
Thunnus germo, T. orirntalis: liibliography ; classi-
fication ; description ; distribution ; migration ;
food; habits; fishing conditions correlated with
oceanography ; figures ; Japanese common names.
1948b. Aquatic resources of the Ryukyu area. SCAP
Nat. Resoui-ces Sec. Rpt. No. 117. 54 pp.
Au^vis hira, A. tapeinosoma, Euthynnns yaito, Kat-
suwonus pelamis, Neothunnus macropterus, Para-
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bibliography ; distribution ; Ryukyuan conmion
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SnlMAMfR.^, Kanae.

■1927. On the correlation between skipjack catch and
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No. 12, pp. 196-198. [J] [P]

20

riSHEKT BULLETIN OF THE FISH AND WILDLIFE SERVICE

SHI^rIzu, Wataru.
1947. Seasonal changes in the composition of tuna flesh.
Bull. Japanese Soc. Sci. Fish., vol. 13, No. 1, pp.
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Chemical analysis of black tuna flesh.

Shizuoka Peefectural Fisheries Experiment Station.

1936. Investigation of skipjack fishing. Prog. Rpt.
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[J] [P]
Skipjack catch correlated with water temperature.

1937. Investigation of skipjack fishing. Prog. Rpt.
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[J] [P]
Skipjack catch correlated with water temperature.

Smith, Osgood R., and Milner B. Schaefer.

1949. Fishery exploration in the western Pacific (.Janu-
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Big-eyed tuna, Eiitluiiinus yaito, KatsuH-onns pcla-
mis, yellowfin tuna : Hawaiian, Line, former Japa-
nese mandated islands; occurrence recorded; E.
yaito, K. pelamis figured.

Smith, Robert O.

1947. Survey of the fisheries of the former Japanese
mandated islands. U. S. Fish and Wildlife Serv., Fish.
Leaf. 273, pp. 89-95.
Katiiiiwonus pelamis. Neothminus macropterus,
Thnniu(s f/ertno: Hawaiian and Micronesian com-
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Snyder, John Otterdein.

1904. A catalogue of the shore fishes collected by the
steamer Albatross about the Hawaiian Islands in
1902. Bull. U. S. Fish Comm. for 1902, vol. 22, p. 523.
Germo sibi: recorded.

Society for the Promotion of Oceanic Fisheries.
1936. Tunas. Ocean. Fish., No. 4, pp. 1-62. [J] [P]
Albacore : differences in quality of flesh of summer
and winter fish correlated with sexual maturity,
body condition, season ; chemical analysis of fiesh ;
spawning : migration : location of fishing grounds
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compared with Thiinnus ihuntms; .spawning.

Soldatov, V. K.

1929. A check list of fishes recorded from Russian Pa-
cific waters. Jour. Pan-Pacific Res. Inst., vol. 4, No. 1,
p. 5.

Auxis thazard, Tliunnus thynnus: listed.

Soldatov, V. K., and G. J. LiNDRtniG.

1930. A review of the fishes of the seas of the Far East.
Bull. Pacific Sci. Fish. Inst., vol. 5, pp. 103-109.

Auxis Itira, A. mnru, Ocrmo alahiiifin. Kritsincoinia
pelamis, Jfeothunnus macropterus, Thunnus thyn-
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synonymy; keys to Parathunnus and Kishinoella;
Thunnus thynnus figured.

South Seas Government-General Fisheries Experiment
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1937a. Investigation of the fisheries of the Mariana
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1937b. Investigation of the fisheries of the Jlarshall
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I>istribution of tunas.
19.37c. Survey of fishing grounds and channels in Patau
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Skipjack fishing conditions correlated with oeeano-
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1938. Report of oceanographical investigations. South
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1941a. Experimental tuna fishing in waters adjacent to
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Distribution of tunas.
1941b. Investigation of tuna fishing in waters adjacent
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Indo-Pacific region ; yellowfin tuna catch correlated
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1941c. Investigation of skipjack fishing in the central
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Release of tagged skipjack recorded.
1941d. Investigation of skipjack fishing in Tap waters.
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Skipjack length-weight data ; body condition.
1942. Report of a survey of the tuna fishery in Palau
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1943a. Investigation of albacore fishing in the central
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Length-weight, body depth data for albacore and
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1943b. Report of the investigation of tuna fishing in
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Skipjack, yellowfin tuna : fishing conditions corre-
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Starks, Edwin Chapin.
1918. The mackerel and mackerel-like fishes of Cali-
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BIBUOGRAPHY ON PACIFIC TUNAS

21

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22

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Taranetz, a. R.

1937. Handbook for identification of fishes of Soviet
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Auxis hira, A. inaru, Oermc alalunga, Katsuwonus
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tliunnina; figures of all except T. orientaUs; T.
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Thompson, William F., and Elmer Hiogins.

1919. Notes from the State Fisheries Laboratory. Cali-
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Auxis thazard noted in commercial catch ; distribu-
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1944. Hawaiian fishes. Tongg Publ. Co., Honolulu, pp.
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Auxis thaxard, Euthynnus allettcrntus, E. pelanii^,
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Hawaiian common names of E. aUetteratus, E.
peJamis, N. macropterus, T. thynnus; Japanese
common names of N. macropterus, 8. itosibi, T.
orientaUs, T. thynnus; European common names
of G. alalunga, T. thynnus; habits, food, enemies of
E. pelamis; food, enemies, reproduction of T.
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TiRANT, Gilbert.

1929. Note sur les poissons de la Basse-Cochinchine et
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TOMINAGA, SEIJIRO.

1943. Bonitos. Sci. Sea, vol. 3, No. 10, pp. 460-465. [J]
Frigate mackerels, black skipjack : description ;
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Tomitama, Tetsuo.

1933. The chemical composition of tunny liver oiL Bull.
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Toyama, Yuzo, et al.

1941. Studies on fish in Japan as a source of insulin.
Bull. Japanese Soc. Sci. Fish., vol. 10, No. 4.

Oermo germo, Katsuwonus vagans, Neothunnus
7nacroptems, Parathunnus sibi: yields of insulin
tabulated.
Tube, J. A.

1948. Whale sharks and devil rays in North Borneo.
Copeia, No. 3, p. 222.
Euthynnus macroptera: recorded.

UCHIDA, KEITAEO.

1923. On the jumping and flight of fishes and other
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Euthynnus vagans, Thunnus thynnus: jumping be-
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Uda, Michitaka.

1932. On the body weights of some scombroid fishes of
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Thunnus thynnus: probable causes of seasonal
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1935a. On the estimation of favourable temperature for
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Oermo macropterus, Parathunnus sibi, Thunmis
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1935b. The results of simultaneous oceanographical in-
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1936. Locality of fishing centre and shoals of "katuwo"
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BIBLIOGRAPHY OX PACIFIC TUNAS

23

Uda. Michitaka— Continued

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1937. Fishing of Oermo genno (Lac^i^^de) in relation
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1934. Local variations in the composition of various

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1940. The Acanthocephala collected by the Allan Han-
cock Pacific Expedition, 1934. A. Hancock Pacific
Exped., vol. 2, No. 15, p. 512.

Euthynnus altettcratus and Katsuwonus pelamis
listed as hosts.

Wade, Charles B.
1940. Notes on the Philippine frigate mackerels, family
Thunuidae, Genus Auxis. U. S. Fish and Wildlife
Serv. Fish. Bull., vol. 51, No. 46, pp. 22&-240.
Auxis tapcinosoma, A. thaxard: classification; de-
scription; key; synonymy; distribution; moi-pho-
metric measurements; counts of meristic charac-
ters; figures; records, descriptions, and figures of
juveniles.

Waite, Edgar R.

1907. A basic list of the fishes of New Zealand. Rec.
Canterbury Mus., vol. 1, No. 1, p. 24.
Oymnosarda pelamis: synonymy.
1921. Illustrated catalogue of the fishes of South Aus-
tralia. Rec. South Australian Mus., vol 2 No 1 p
143.

Tliunnus thynnus: listed; synonymy.

24

FISHERY BUXiLETIN OF THE FISH AJSTiD WILDLIFE SERVICE

Waitk, Edgar R. — Continued
192S. A catalogue of the marine fishes of South Aus-
tralia. Jour. Pan-Patiflc Res. lust., vol. 3, No. 1,
p. 8.

Thunnus maccori: listed.

Walford, Lionel A.

1931. Handbdolj of common commercial and game fishes
of California. California Dlv. Fish and Game, Fish
Bull. No. 28, pp. 74-77.

Germo alalunya, Kat silicon us pclaiiiis, Ncothiinniis
macropterus, Thunnus thynnus: classification; Eng-
lish common names : description ; distribution ;
figures ; ke.v.
1037. Marine game fishes of the Pacific Coast — Alaska
to the Equator. Univ. California Press, Berkeley, pp.
1-20, 2(>-30.

Euthjinnus Uncutus, Gcnno alaUinya, Katsxnconus
pelamis, Neothunnus macropterus, Thunnus thyn-
nus: description; distribution; food; spawning;
key ; English common names ; figures. Auxis
tha~ard: description ; distribution ; English common
names; figure; key. Migration of G. nJatunga, K.
pelamis and N. macropterus ; enemies of T. thyn-
nus; N. macropterus compared with Allison's tuna.
Wataxabe, Hajime.

1030. Investigation of albacore. Prog. Rpt. Shizuoka
Pref. Fish. Espt. Sta. for 10.36-38, pp. 22-23. [J] [P]
Albacore : mid-Pacific ; stomach contents ; sexual
maturity ; body proportions of males and females
compared ; morphometric data ; probable spawning
season, area, number of eggs.
Watanaee, Hakuo.

1940. Fishing conditions south of the Mar.shall Islands.
South Sea Fisli., vol. 6, No. 4, p. 22. [J] [P]
Big-eyed tuna, yellowfin tuna : length-weight data.
Wataxabe, N.

1041. Measurements on the bodily density, body temper-
ature and swimming-velocity of "katsuwo", Euthyn-
nus vaguns (Lesson). Bull. Japanese Soc. Sci.
Fish., vol. 11, No. 4, pp. 14C-14S. [Je]
Weber, Max.

1913. Die Fische der Siboga-Expedition. P. 401.
Leiilen.

Thynnus thunnina: Indo-Australian Archipelago;
synonymy ; recorded.

Welsh, James P.

1040. Range extension of the file fish Monocnnthus
mehDiocepIialus. Pacific Sci., vol. 3. No. 1, p. lOO.
Hawaii ; specimens recovered from Euthynnus
yaito.
Whitehead, S. S.

1920. Tuna season. California Div. Fish and Game,
Fi.sh Bull. No. 1.5, p. 48.

Albacore, bluefin tuna, skipjack, yellowfin tuna :
distribution and seasonal occurrence.
1931. Fishing methods for the bluefin tuna I Thunnus
thynnus) and an analysis of the catches. California
Div. Fish and Game, Fish Bull. No. 33, 32 pp.

Classification; distribution; figure; migraticm;
spawning; catch per unit of effort.
Whitley, Gilbert P.

1928. A check-list of the fishes of the Santa Cruz Archi-
pelago, Melanesia. Jour. Pan-Pacific Res. Inst., vol. 3,
No. 1, p. 12.

Neothunnus macropterus: listed.
1937. The Middleton and Elizabeth Reefs, South Pacific
Ocean. Australian Zool., vol. 8, pt. 4, pp. 229-231.
Wanderer wallisi proposed as new genus and
species ; synonymy ; description ; food ; compared
with E. yaito and E. allitfcratus.

1947. New sharks and fishes from Western Australia.
Australian Zool., vol. 11, pt. 2, pp. 129-150.

Euthynnus alleteratus, Katsuiconus pelamis, Kishi-
noclla tonggol, Neothunnus macropterus, Thunnus
maccoyi: recorded; Australian common names.
Yabe, Hiroshi. and Tokumi Mow.

1948. Report of .skipjack investigations for 1947. Cent.
Pish. Expt. Sta. Rpt., No. 30. [P]

Ryukyu Islands ; length-weight data ; stomach con-
tents ; catch correlated with water temperature ;
size composition of commercial catch ; age anal-
ysis ; spawning season ; maturation of gonads ; esti-
mated number of eggs ; past records of juveniles
captured in Ryukyu waters.
Yamamoto, Shokichi.

1940. Views on increasing the commercial value of dried

fish sticks from the South Seas. South Sea F^sh.,

vol. 3, No. 11, pp. 21-35. [J] [P]

Skipjack : Japan, Formosa, South Seas ; propor-
tional weights of various body parts compared.

ABBREVIATIONS USED

A. Hancock Pacific Exped. — Allan Hancock Pacific Ex-
peditions. Los Angeles.
Acad. Nat. Sci. Phila., Monogr. — Academy of Natural

Sciences of Philadelpliia, Monographs. Philadelphia.
Act. Soc. Sci. Indii-Nocrlandicae — Acta Societatis Scien-

tariiiin Indo-Ncerlandicae. Batavia.
Ann. and Mag. Nat. Hist. — The Annals and Magazine of

Natural History- Ix)ndon.
Ann. New York Acad. Sci. — Annals of the New York

Academy of Sciences. New York.
Ann. Rpt. Laguna Mar. Lab. — ^Annual Report of the

Laguna Marine Lalioratory. Claremont, California.
Annot. Zool. Jap. — Annotationes Zoologicae Japonenses.

Tokyo.
Arch. Neerlandaises Sci. Nat. — Archives Neerlandaises

des Sciences Exactes et Naturelles. Haarlem.
Australian Zool. — The Australian Zoologist. Sydney.

Bernice P. Bishop Mus. Occas. Papers — Bernice Pauahi
Bishop Jluseum. Occasional Papers. Honolulu.

Biblio. Nederlandsch Indische Nat. Ver. — Bibliotheek van
de Nederlandsch Indische Natuurhistorische Vereenig-
ing. Batavia.

Biol. Bull. St. John's Univ.— Biological Bulletin of St.
John's University. Shanghai.

Bull. American Mus. Nat. Hist. — Bulletin of the American
JInseura of Natural Historj. New York.

Bull. Bernice P. Bishop Mus. — Bulletin. Bernice Pauahi
Bishop Museum. Honolulu.

Bull. Biogeog. Soc. Japan — Bulletin of the Biogeographical
Society of Japan. Tokyo.

Bull. U. S. Bur. Fish.— Bulletin of tlie Bureau of Fish-
eries. United States Department of Commerce and
Lahor. Washington.

Bull. Japanese Soc. Sci. Fish. — Bulletin of the Japanese
Society of Scientific Fisheries. Tokyo.

Bull. Pacific Sci. Fish. Inst. — Bulletins of the Pacific
Scientific Fisheries Institute. Vladivostok.

Bull. Pacific Sci. Inst. Fish, and Oceanogr. — Bulletin of
the Pacific Scientific Institute of Fisheries and Ocean-
ograjihy. Vladivostok.

Bull. Scripps Inst. — Bulletin. Scripps Institution for
Biological Research. Berkeley.

Bull. So. Calif. Acad. Sci.— Bulletin of tlie Southern Cali-
fornia Academy of Sciences. Los Angeles.

Bull. U. S. Fish Comm.— Bulletin of the United States
Fi.sh Commission. Washington.

Bur. Fish., Min. .\gr. and For., Japanese Imp. Govt. —
Bureau of Fisheries. Ministi-y of Agriculture and For-
estry. Japanese Imperial Government. [Suisankyoku.
Norinsho. Dai Nippon Teikoku Seifu.] Tokyo.

California Div. Fish and Game, Bur. .Mar. Fish. — Cali-
fornia Division of Fish and Game, Bureau of Marine
Fisheries. San Francisco.

California I>iv. Fisli and Game, Fish Bull. — California
Division of Fish and Game. Fish Bulletin. Sacramento.

Cent. Fish. Expt. Sta. Rpt. — Central Fisheries Experiment
Station Reports. [Suisan Shikenjo Chosa HOkoku.]
Tokyo.

Com. Fish. Rev. — Commercial Fisheries Review. Fish
and Wildlife Sei-vice. United States Department of the
Interior. Washington.

Coiieia — Copeia. New York.

Council Sci. and Indust. Res., Australia, Pamphlet — Coun-
cil for Scientific and Industrial Research. Common-
wealth of Australia. Pamphlet. Melbourne.

Dept. Fish., New South Wales — Department of Fisheries,
New South Wales. Sydney.

Field Mus. Nat. Hist., Zool. Ser. — Field Museum of Natural
History, Zoological Series. Chicago.

Fish. Div., FAO, UN.— Fisheries Division. The Food and
Agriculture Organization of the United Nations. Wash-
ington.

Fish. Invest. (Suppl. Rpt.), Imp. FLsh. Expt. Sta. — Fishery
Investigation (Supplementary Report). Imperial Fish-
eries Experiment Station. Tokyo.

Fish. Res. Bd. Canada, Bull. — Fisheries Re.search Board of
Canada, Bulletin. Vancouver.

Fish. Technol. Lect. Series — Fisheries Technology Lecture
Series. [Suisan Seizo Kogaku Koza.] Tokyo.

Formosa Fish. Mag. — Formosa Fisheries Magazine. [Tai-
wan Suisan Zasshi.] Taihoku.

Formosa Govt.-Gen. Fish. Expt. Sta. Publ. — Formosa Gov-
ernment-General Fisheries Experiment Station. Publi-
cations. [Taiwan Sotokufu Suisan Shikenjo Shuppan.]
Kiirun.

Iclith. Contrlb. Internatl. Game Fish Assoc. — Ichthyologi-
cal Contriliutions of the International Game Fish Asso-
ciation. New York.

Japanese Jour. Zool. — Japane.se Journal of Zoology.

Tokyo.
Jour. Acad. Nat. Sci. Phila. — Journal of the Academy of

Natural Sciences of Philadelphia. Philadelphia.
Jour. Asiatic Soc. Bengal — Journal of the Asiatic Society

of Bengal. Calcutta.
Jour. Biol. Chem. — Journal of Biological Chemistry. New

York.
Jour. Coll. Agr., Imp. Univ. Tokyo — Journal of the Collesre

of Agriculture. Imperial University of Tokyo. Tokyo.
Jour. Coll. Sci., Imp. Univ. Tolcyo — Journal of the College

of Science. Imperial University of Tokyo. Tokyo.
Jour. Council Sci. and Indust. Res., Australia — Journal of

the Council for Scientific and Industrial Research.

Commonwealth of .\ustralia. Meltiourne.
Jour. Fac. Sci., Imp. Univ. Tokyo — Journal of the Faculty

of Science, Imperial University of Tokyo. Tokyo.

25

26

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Jour. Imp. Fish. Bur. Tokyo — Journal of the Imperial
Fisheries Bureau. Tokyo.

Jour. Imp. Fish. Expt. Sta. — Journal of the Imperial Fish-
eries Experiment Station. Tok.vo.

Jour. Mus. Godeffroy — Journal des Museum Godeffroy.
Hamburg.

Jour. Pan-Pacific Res. Inst. — Journal of the Pan-Pacific
Research Institution. Honolulu.

Mem. Bernice P. Bishop Mus. — Jlemoirs of the Bernice
Pauahi Bishop Museum. Honolulu.

Mem. California Acad. Sci. — Memoirs of the California
Academy of Sciences. San FrancLsco.

Mem. Carnegie Mus. — Memoirs of the Carnegie Museum.
Pittsburgh.

Mid-Pacific Mag. — Mid-Pacific Magazine. Honolulu.

Miyagl Pref. Fish. Expt. Sta. — Miyagi Prefe<.tural Fish-
eries Experiment Station. [Miyagi-ken Suisan Shi-
kenjo. Watanoha.

Nat. Genee.sk. Arch. Neerland's Indie — Natuur en Genee-
skundig Archief voor Neerland's-Indie. Batavia.

Nat. Ti,idschr. Nederlandsch-Indie — Natuurkundig Tijd-
schrift voor Nederlandsch-Indie. Batavia.

Nederlundsch Tijdschr. Dierk. — Nederlandsch Tijdschrift
voor de DIerkunde. Amsterdam.

New Zealand Jour. Sci. Technol. — New Zealand Journal
of Science and Technology. Wellington.

New Zealand Mar. Dept. Fish. Bull. — New Zealand Marine
Department Fisheries Bulletin. Wellington.

Nissan Fish. Res. Sta. Odawara — Nissan Fisheries Re-
search Station. [Nissan Suisan Kenkyujo.] Odawara.

Note Serv. OciSanogr. Peches Indochine — Notes. Service
OcSanographique des Peches de ITndochine. Station
Maritime de Cauda. Saigon.

Occas. Pap. California Acad. Sci. — Occasional Papers of

the California Academy of Sciences. San Francisco.
Ocean. Fish. — Oceanic Fisheries. [Kaiyo Gyogyo.] Tokyo.

Pacific Biol. Sta., Fish. Res. Bd. Canada, Circ. — Pacific
Biological Stations, Fisheries Research Board of Can-
ada. Vancouver.

Pacific Sci. — Pacific Science. Honolulu.

Palao Trop. Biol. Sta. Studies— Palao Tropical Biological
Station Studies. Tokyo.

Philippine Jour. Sci. — Philippine Journal of Science.
Manila.

Proc. Acad. Nat. Sci. Phila. — Proceedings of the Academy
of Natural Sciences of Philadelphia. Philadelphia.

Proc. California Acad. Sci. — Proceedings of the California
Academy of Sciences. San Francisco.

I'roc. Sci. Fish. Assoc. — Proceedings of the Scientific Fish-
eries Association. Tokyo.

I'roc. Sixth Pacific Sci. Cong. — Proceedings of the Sixth
Pacific Science Congress. Berkeley and Los Angeles.

Proc. U. S. Natl. Mus. — Proceedings of the United States
National Museum. Washington.

Proc. Zool. Acclim. Soc. Victoria — Proceedings of the
Zoological and Acclimation Society of Victoria. Vic-
toria.

Prog. Rpt. Chiha Pref. Fish. Expt. Sta. — Progress Reports
of the Chiba Prefectural Fisheries Experiment Station.
[Chiba-ken Suisan Shikenjo Jigyd Hokoku.] Tateyama.

Prog. Rpt. Chiba Pref. Fish. Expt. Sta., Katsuura Br.—
Progress Reports of the Chiba Prefectural Fisheries
Experiment Station, Katsuura Branch. [Chiba-ken
Suisan Shikenjo Katsuura Bunjo Jigyo Hokoku.]
Katsuura.

Prog. Rpt. Formosa Govt.-Gen. Fish. Expt. Sta. — Progress
Reports of the Formosa Government-General Fisheries
Experiment Station [Taiwan Sotokufu Suisan Shi-
kenjo ; Jigyo Hokoku ; Shiken Hokoku ; Suisan Shiken
Hokoku.] Kiirun.

Prog. Rpt. Hokkaido Fish. Expt. Sta. — Progress Reports
of the Hokkaido Fisheries Experiment Station. [Hok-
kaido Suisan Shikenjo Suisan Chosa Hokoku.] Yoichi.

Prog. Rpt. Kagoshima Pref. Fish. Expt. Sta. — Progress
Reports of the Kagoshima Prefectural Fisheries Experi-
ment Station. [Kagoshima-ken Suisan Shikenjo Jigyo
Hokoku.] Kagoshima.

Prog. Rpt. Kochi Pref. Fish. Expt. Sta. — Progress Reports
of the Kdchi Prefectural Fisheries Experiment Station.
[Kochi-ken Suisan Sliikenjo Jigyo Hokoku.] Susaki.

Prog. Rpt. Kumamoto Pref. Fish. Expt. Sta. — Progress
Reports of the Kumamoto Prefectural Fisheries Experi-
ment Station. [Kumamoto-ken Suisan Shikenjo Jigyo
Hokoku.] Kumamoto.

Prog. Kpt. Mie Pref. Fish. Expt. Sta.— Progress Reports
of the Mie Prefectural Fisheries Experiment Station.
[Jlie-kon Suisan Shikenjo Jigyd Hokoku.] Tsu.

Prog. Rpt. Nagasaki Pref. Fish. Expt. Sta. — Progress Re-
ports of the Nagasaki Prefectural Fisheries Experiment
Station. [Nagasaki-ken Suisan Shikenjo Jigyo Ho-
koku.] Nagasaki.

Prog. Rpt. Oita Pref. Fish. Expt. Sta. — Progress Reports
of the Oita Prefectural Fisheries Experiment Station.
[Oita-ken Suisan Shikenjo GyOmu Hokoku.] Oita.

Prog. Rpt. Okinawa Pref. Fish. Expt. Sta.— Progress Re-
ports of the Okinawa Prefectural Fisheries Experiment
Station. [Okinawa-ken Suisan Shikenjo: Jigyd Ho-
koku; Seiseki ; Seiseki Gaiyd.] Naha.

Prog. Rpt. Pacific Coast Sta., Fish. Res. Bd. Canada— Re-
ports of the Pacific Coast Stations, Fisheries Research
Board of Canada. Vancouver.

Prog. Rpt. Shizuoka Pref. Fish. Expt. Sta. — Progress Re-
ports of the Shizouka Prefectural Fisheries Experiment
Station. [Shizuoka-ken Suisan Shikenjo Jigyd Ho-
koku.] Sliimizu.

Prog. Rpt. South Seas Govt.-(Jen. Fish. Expt. Sta.— Prog-
ress Reports of the South Seas Government-General
Fisheries Experiment Station. [Nanyd-chd Suisan
Shikenjo Jigyd Hokoku.] Patau.

Prog. Rpt. Taihoku Prov. Fi.sh. Expt. Sta.— Progress Re-
ports of the Tailioku Province Fisheries Experiment
Station. [Taihoku-shii Suisau Shikenjo Gydmu Hd-
koku.] Taihoku.

Prog. Rpt. Takao Prov. Fish. Expt. Sta. — Progress Reports
of the Takao Province Fisheries Experiment Station.
[Takao-shfi Suisan Shiken Chdsa Hokoku.] Takao.

Publ. Field Mus. Nat. Hist. — Puljlications. Field Museum
of Natural History. Chicago.

BIBLIOGRAPHY ON PACIFIC TUNASI

27

Rec. Canterbury Mnscuin — Records of the C;inlerliui-y -Mu-
seum. Christcliuieh.

Rec. Oceanogr. Works — Records of Oceauographic Works
in Japan. Tokyo.

Rec. So. Australian Mus. — Records of the South Australian
Museum. Adelaide.

Rpt. British Assoc. Adv. Sci. — Report of the Briti.sh As-
sociation for the Advancement of Science. London.

Rpt. U. S. Fish Conim. — Report of the Commissioner.
United States Commission of Fish -and Fisheries.
Washington.

SCAP Nat. Resources See. Rpt. — Supreme Commander for

the Allied Powers. General Headquarters. Natural

Resources Section. Reports. Tokyo.
Sci. Sea — Science of the Sea. [Kaiyo no Kagaku.]
Sea and Sky — Sea and Sky. [Umi to Sora.] Kobe.
Semi-Ann. Rpt. Oceanogr. Invest. — Semi-Annual Report

of Oceaniigraphical Investigations. Tokyo.
Smithsn. Misc. Collect. — Smithsonian Miscellaneous Col-
lections. Washington.
Soc. Prom. Ocean. Fish. — Society for the Promotion of

Oceanic Fisheries. [Kaiyo Gyogyo Kyokai.] Tok.vo.
South Sea Fish. — South Sea Fisheries. [Nanyo Suisau.]

Tokyo.
South Sea Fish. News — South Sea Fisheries News.

fNanyo Suisan JohO.] Patau.
South Sea Sci. — South Sea Science. [Kagaku Nanyo.]

Palau.
Stanford Ichth. Bull.— Stanford Ichthyological Bulletin.

Stanford.
Stanford Univ. Publ., Univ. Ser., Biol. Sci.— Stanford

University Publications, University Series, Biological

Sciences. Stanford.

Tecli. Educ. Ser. Technol. Mus., Sydney — Technical Edu-
cation Series. Technological Museum. Sydney.

Text Fish.— The Text of the Fisheiy. Tokyo.

Trans. Nat. Hist. Soc. Formosa — Transactions of the
Natural History Society of Formosa. [Taiwan Haku-
butsu Gakkai Kaiho.] Taihoku.

Trans. New Zealand Inst. — ^Transactions and Proceedings

of Ihe New Zealand Institute. Wellington.
Trans. Roy. Soc. New Zealand — Transactions and Proceed.

ings of the Royal Society of New Zealand. Dunedin.
Trans. Thirteenth No. Amer. Wildlife Conf. — Transactions

of the Thirteenth North American Wildlife Conference.

Washington.
Trav. Inst. Oceanogr. Indochine — Travaux de I'lnstitut

Oceanographique de I'Indochine. Saigon.
Treubia — Treubia. Buitenzorg.

U. S. Fish and Wildlife Serv., Circ- United States Depart-
ment of the Interior, Fish and Wildlife Service, Circu-
lar. Washington.

U. S. Fish and Wildlife Serv. Fish. Bull.— United States
Department of the Interior. Fishery Bulletin of the
Fish and Wildlife Service. Washington.

U. S. Fi.sh and Wildlife Serv., Fish. Leaf.— United States
Department of the Interior. Fish and Wildlife Service,
Fishery Leaflet. Washington.

U. S. Natl. Mus. Bull. — United States Naticmal Museum.
Bulletin. Washington.

Univ. California Publ. Zool. — University of California
Publications in Zoology. Berkeley.

Verb. Batavia Genoot. Kunst. Wetene. — ^Verhandelingen
van het Bataviaasch Genootschap van Kunsten en
Wetenschappen. Batavia.

Versl. Akad. Amsterdam — Verslagen van de Gewone
Vergaderingen der Wis en Natuurkundige Afdeeling.
Koninklijke Academic van Wetenschappen. Amsterdam.

Vidensk. Selskr. Skr. — Kongelige Danske Videnskabernes
Selskab. Copenhagen.

Woods Hole Oceanogr. Inst. Tech. Rpt. — Woods Hole
Oceauographic Institution. Technical Report. Woods
Hole.

Zool. Mag. — Zoological Magazine. [Dobutsugaku Zasshi.]

Tokyo.
Zool. Meded. — Zoologische Mededeelingen. Leiden.

INDEX BY SUBJECTS

Age

Aikawa, 1937.
Aikawa and Kato, 1938.
Ban, 1041.
Bi-ock, 1943.
Higashi, 1941b.

Ikebe, 1939, 1940a, 1940b, 1940c, 1941a, 1941b.
Kanamura and Yazaki, 1940a, 1940b.
Kimura, 1935, 1941, 1942a.
Okamoto, 1940.
Schuefer, 1948b.
Tauchi, 1940a, 1940b, 1940e.
Uno, 193Cb.
Tabe and Mori, 1948.
Albacore. See Tlmnnus germo.
Allison's tuna. See Neothunnus alHsoni.
Alloihunnus fallai
Anatomy

Serventy, 1948.
Classification

Fraser-Brunner, 1950.

Serventy, 1948.
Compared with Katsuwonidae

Serventy, 1948.
Description

Fraser-Brunner, 1950.

Serventy, 1948.
Distribution

Fra.ser-Brunner, 1950.

Serventy, 1948.
Figured

Fraser-Brunner, 1950.

Serventy, 1948.
Keys

Fraser-Brunner, 1950.
Measurement data

Serventy, 1948.
Synonymy

Fraser-Brunner, 1950.
Anatomy
Air bladder

Fish, 1948.

Kishinouye, 1922a.
And evolution

Kishinouye, 1919a.
Brain

Matsul, 1942a.

Migita and Arakawa, 1948.
Digestive system

Suyehiro, 19.36, 1938, 1941, 1942.
External and internal

Berg, 1947.

Eckles, 1949b.

Godsil and Byers, 1944.

Imamura, 1949.

28

Anatomy — Continued

External and internal — Continued

Kishinouye, 1915a, 191ub, 1917a, 1918, 1921, 1923.

Nakauiura, 1949.

Roedel, 1948b.

Schaefer and Marr, 194Sb.

Serventy, 1942b, 1948.

Takahashi, 1924.
Figured

Godsil and Byers, 1944.

Higashi, 1941a, 1941c.

Kishinouye, 1915b, 1919a, 1923.

Matsul, 1942b.

Migita and Arakawa, 1948.

Nakamura, 1938.

Serventy, 1941, 19421), 1948.

Suyehiro, 1942.
Reproductive system

Bennett, 1840.

Matsui, 1942b.

Nakamura, 1938.

Nakamura Res. Staff, 1949.

Okinawa Pref. Fish. Expt. Sta., 1931.
Astronomical phenomena correlated with filshing
Kawana, 1934.

Takao Prov. Fish. Expt. Sta., 1927.
Auxis
Anatomy

Kishinouye, 1915b, 1919a.
As food of tunas

Asano, 1939.
Chemical analysis

Okuda, 1918.
Common names

Tominaga, 1943.
Description

Tominaga, 1943.
Distribution

Schaefer, 1948c.

Tominaga, 1943.
Food

Tominaga, 1943.
Habits

T<miinaga, 1943.
Honnones

Migita and Arakawa, 1948.
Reproduction

Schaefer, 1948c.
Young

Kishinouye, 1926.

Schaefer, 1948c.
Auxis hira
Anatomy

Kishinouye, 1915a, 1923.

BIBLIOGRAPHY ON PACIFIC TUNAS

29

A axis hira — Continued
Classification

Kishinouye, lOina, 1923.

Nakaniura, 193'JI).

Olinda and Jlatsubaia, 1938.

Soldatov and Liudbers, 1930.

Taranetz, 1937.
Common names

Fujita and Wakiya, 1915.

Kishinouye, 19ir)a, 1923.

Nakamnra, 19;!91).

Okada and Mafsuliara, 1938.

Shapiro, 194Sb.
De.scription

Imamura, 1949.

Jordan and Hiibbs, 1925.

Kishinouye, 1915a, 1923.

Okada and Matsubara, 19.38.

Soldatov and Lindlierg. 1930.
Distribution

Fujita and Wakiya, 1915.

Imamura, 1949.

Jordan and Hubbs, 1925.

Kishinouye, 1915a, 1923.

Okada and Matsubara, 1938.

Shapiro, 194Sb.

Soldatov and Lindberg, 1930.

Tanaka, 1931.

Taranetz, 1937.
Figured

Kishinouye, 1915a, 1923.
Food

Kishinouye, 1923.
Habits

Imamura, 1949.

Kishinouye, 1923.
Keys

Kisliinouye, 1915a, 1923.

Okada and Matsubara, 1938.

Soldatov and Lindberg, 1930.

Taranetz, 1937.
Synonymy

Kishinouye, 1923.

Nakamura, 1939b.

Soldatov and Lindberg, 1930.

Tanaka, 1931.

Auxi.i maru
Anatomy

Kishinouye, 1915a, 1923.
Classification

Kishinouye, 191.5a, 1923.

Nakamura, 1939b.

Soldatov and Lindberg, 1930.

Taranetz, 1937.
Common names

Fujita and Wakiya. 1915.

Kishinouye, 1915a, 1923.

Nakamura, 1939b.

Aiixis maru — Continued
Description

Imamura, 1949.
Kishinouye, 191.".a, 1923.
Soldatov and Lindberg, 1930.
Distribution
Fujita and Wakiya, 1915.
Imamura, 1949.
Kishinouye, 191.-.a, 1923.
Soldatov and Lindberg, 1930.
Taranetz, 1937.
Figured

Kishinouye, 1915a, 1923.
Food

Kishinouye, 1923.
Habits

Imamura, 1949.
Kishinou.ve, 1923.
Keys

Kishinouye, 1915a, 1923.
Soldatov and Lindberg, 1930.
Taranetz, 1937.
Reproduction

Kishinouye, 1915a.
Synonymy
Kishinouye, 1923.
Nakamura, 1939b.
Soldatov and Liuillierg, 1930.
Young as food of tunas
Kishinouye, 1917b, 1923, 1924.
Auxis ramsayi
Distribution

McCulloch, 1922.
Keys

McCulloch, 1922.
Synonymy
McCulloch, 1922.
Atiwis rochei
Description

Giinther, 1860.
Distribution
Chu, 1931.
Giinther, 1860.
Synonymy
Chu, 1931.
Gunther, 1860.
Auxis tfiijcinosomti
Classification
Okada and Matsubara, 1938.
Wade, 1949.
Common names

Jordan and Hubbs, 1925.
Jordan and Snyder, 1!)01.
Okada and Matsubara. 1938.
Shapiro, 194.Sb.
Compared with Au.ri.s thyniioides

Bleeker, 1855.
Description
Bleeker. 1854.
Gunther, 1860.

30

FISHDRT BULLETIN OF THE FISH AKD WILDLIFE SERVICE

Auxis tapeinosoma — Continued
Description — Continued

Jordan and Hubbs, 1925.

Okada and Matsubara, 1938.

Wade, 1949.
Distribution

Bleelier. 18.54, 18.57.

Giinther, 1860.

Jordan and Hubbs, 1025.

Jordan and Snyder, 1001.

Okada and Matsubara, 1938.

Reeves, 1928.

Shapiro, 1948^

Wade, 1949.
Figured

Wade, 1949.
Keys

Okada and Matsubara, 1938.

Wade, 1940.
Measurement data

Wade, 1949.
Meristic characters

Wade, 1949.
Synonymy

Giinther, 1860.

Jordan and Hubbs, 1925.

Wade, 1949.
Young

Wade, 1949.
Auxis taso

Compared with Auwis thynnoides

Bleeker, 1855.
Description

Cuvier and Valenciennes, 1831.
Distribution

Bleeker, 1845, 1850, 1878.

Auxis thazard
Anatomy

Schaefer and Marr, 1948b.
As food of tunas

Marukawa, 1939.
Classification

Fraser-Brunner, 1950.
Common names

Barnhart, 1936.

FAO, 1949.

Fish, 1948.

Herre and Umali, 1948.

Jordan and Evermann, 1896.

Jordan and Metz, 1913.

Jordan, Tanaka, and Snyder, 1913.

Serventy, 1941.

Tinker, 1944.

Ulrey and Greeley, 1928.

Walford, 1937.
Description

Barnhart, 1936.

Cuvier and Valenciennes, 1831.

Fowler, 1928, 1938.

Fraser-Brunner, 10.50.

Auxis thazard — Continued
Description — Continued

Jordan and Evermann, 1905.

Meek and Hildebrand, 1023.

Schaefer and Marr, 1948b.

Serventy, 1941.

Tinker, 1944.

Wade, 1949.

Walford, 1937.
Distribution

Barnhart, 1936.

Domantay, 1940.

FAO, 1949.

Fish, 1948.

Fowler, 1928, 1938, 1944, 1949.

Fraser-Brunner, 1950.

Graham, 1038.

Herre, 1040.

Jenkins, 1003.

Jordan and Evermann, 1896, 1905.

Jordan and Jordan, 1022.

Jordan and Metz, 1013.

Jordan and Seale, 1906.

Jordan and Snyder, 1000.

Jordan, Tanaka, and Snyder, 1913.

Lord, 1927.

McCuUoch, 1922.

Meek and Hildebrand, 1923.

Mori, 1928.

Reeves, 1928.

Schaefer and Marr, 1948b.

Serventy, 1041.

Soldatov, 1929.

Stead, 1008.

Thompson and Higgins, 1919.

Tinker, 1944.

Ulrey, 1029.

Ulrey and Greeley, 1928.

Wade, 1049.

Walford, 1937.
Figured

Barnhart, 1936.

Domantay, 1940.

Fraser-Brunner, 1930.

Jordan and Evermann, 1905.

Jordan, Tanaka, and Snyder, 1913.

McCuUoch, 1922.

Schaefer and Marr, 1948b.

Serventy, 1041.

Tinker, 1044.

Wade, 1949.

Walford, 1037.
Keys

Brock, 1949.

Fraser-Brunner, 1950.

McCuUoch, 1922.

Meek and Hildebrand, 1923.

Serventy, 1941.

Wade, 1949.

Walford, 1037.

BIBLIOGRAPHY ON PACIFIC TUNAS

31

.1 »./-i.s thaznrd — Cnntimioa
Measurement data

Wade, 1949.
Meristic characters

Schaefer and Marr, 1948b.

Wade, 1949.
Synonymy

FAO, 1949.

Fowler, 192S, 19;'.S, 1944, 1949.

Fraser-Brunner, 1950.

Jenkins, 1903.

Jordan and Everniann, 1S96, 1905.

Jordan, Tanaka, and Snyder, 1913.

McCulloch, 1922.

Meek and HiUlebrand, 1923.

Ulrey and Greeley, 1928.

Wade, 1949.
Young

Schaefer and Marr. 1948b.

Wade, 1949.
Toung as food of tunas

Marukawa, 1939.
Anxis thyniw.ides

Compared with Aii.iix taiidnosoma

Bleeker, 18.55.
Compared with Auxis tnso

Bleeker, 1855.
Compared with Auxis mlgaris

Bleeker, 1855.
Description

Bleeker, 18.".5.
Distribution

Bleeker, 1855, 1863, lS65a.
Avxis vulgaris

Compared with Auxis thiiinioides

Bleeker, 1855.

Bibliography

Corwin, 19.30.

Kishinouye, 1923.

Nakamura, 1949.

Shapiro, 194Sa, 194Sb.
Big-eyed tuna. See Painthunnns spp.
Black tuna. See ThinniHS oricntalis.
Bluefin tuna. See TIiiiidiiis thiiiinus.
Body condition

Aikawa, 1937.

Aikawa an<l Kato, 1938.

Ikebe, 1939.

Ikebe and Matsumoto, 1937.

Kanamura and Yazaki. 194()a, 1940b.

Onodera, 1941.

Soc. Prom. Ocean. Fish., 1936.

South Seas Govt.-Gen. Fish. Expt. Sta., 1941d.

Suyehiro, 1936, 1938.
Body temperature

.Vnonynious, 19.38.

Kananuira and Imaizunii. 19.35.

Kanamura and Yazaki, 1940a, 1940b.
929179°— 51 3

Body liMiiiieralure — Continued

Nakamura, 1941.

Oita Pref. Fish. E.xpt. Sta., 1927a, 1930.

Scagel, 1949.

Uda, 1941.

Watanabe, N., 1941.
Bonito. See KutsKirnnus pclamia.

Cateli per unit of I'flfort

Formosa Govt.-Gen. Fish. Expt. Sta., 1933a.

Hiratsuka and Imaizumi, 1934.

Hiratsuka and Ito, 19.34.

Imaizumi, 1937.

Japanese Bur. Fish., 1939. 1940.

Kanamura and Imaizumi, 19:',.".

Kanamura and Yazaki, I'.iKia, 1940b.

Nakamura, 1949.

Okuma, Imaizumi, and Maki, 1935.

Serventy, 1947.

Whitehead, 1931.
Characters, meristic. See Morphometries.
Chemical analysis

Dill, 1921.

Higashi and Hirai, 1948.

Kodama, lizuka, and Harada, 1934.

Miyama and Osakabe, 19.38, 1940.

Miyama, Saruya, and Hasegawa, 1939.

Miyauchi, 1915.

Okuda, 1918.

Shimizu, 1947.

Soc. Prom. Ocean. Fish., 1936.

Tomiyama, 1933.
Classification

Berg, 1947.

Fraser-Brunner, 1949, 1950.

Godsil and Byers, 1944.

HiUlebrand, 1946.

Jordan, 1923.

Kishinouye, 1915a, 1917a, 1923.

Lacepede, 1829.

Liitken, ISSO.

Nakamura, 19.39a, 19.39b, 1943, 1949.

Okada and Matsubara, 1938.

Phillipps, 1927b.

Roedel, 194Sb.

Roughly, 1916.

Schaefer, 194Sa.

Serventy, 1948.

Shapiro, 1948a.

Soldatov and Lindberg, 19.30.

Takahashi, 1924, 1926.

Taranetz, 1937.

Wade, 1949.

Walford, 1931.

Whitehead, 1931.

Whitley, 1937.
Color, water. See Water color, also Oceanographic con-
ditions.
Condition, body. See Body condition.
Contents, stomach. .See Food.

32

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Currents. See also Oceanographic conditions.
Correlated with fishing

Formosa Govt.-Gen. Fish. Expt. Sta., 1930, 1931, 1932,

laSSb, 1934.
Ikebe, 19-lOd.

Inanami, 1940b, 1940e, 1941.

Kagosliima Pref. Pish. Expt. Sta., 1927b, 1928a.
South Seas Govt.-Gen. Fish. Expt. Sta., 1942, 1943b.

Distribution
Abe, 1939.

Anonymous, 1938, 1941.
Barnhart, 1936.
Bleeker, 1844, 184.5, 1850, 1852, 1854, 1855, 1856, 1857,

1860a, 1860b, 1861a, 1861b, 1862, 1863, 1865a, 1865b,

1878, 1879.
Brock, 1938, 1939.
Cantor, 1850.
Chabanaud, 1926.
Chapman, 1946.
Chevey, 1932a, 1932b.
Chu, 1931.

Clemens and Wilby, 1946.
Cooper, 1803.
Cowan, 1938.

Cuvier and Valenciennes, 1831.
Delsman and Hardenburg, 1934
Doniantay, 1940.
Eckles, 1949a, 1949b.
Eigenmann, 1892.

Eigenmann and Eigenmann, 1890, 1891.
Evermann and Seale, 1907.
FAO, 1949.
Fish, 1948.
Fowler, 1904a, 1923a, 1923b, 1927, 1928, 1929, 1931, 1934,

1938, 1944, 1949.
Fowler and Ball, 1925.
Praser-Brunner, 1949, 19.50
Fujita and Wakiya, 1915.
Gilbert and Starks, 1904.
Godsil and Greenhood, 1948.
Graham, 1938.
Griffin, 1927.
Giinther, 1860, 1876.
Hasegawa, 1937.

Herre, 1932, 1933, 1935, 1936, 1940.
Hildebrand, 1946.
Hiratsuka and Imaiziimi, 1934.
Hiratsuka and Ito, 1934.
Holder, 1912.
Hubbs, 1916, 1928
Imaizumi, 1937.
Imamura, 1949.

Japanese Bur. Fish., 1934, 1939, 1940.
Jenkins, 1903.
Jordan, 1885.

Jordan and Evermann, 1896, 1905, 1926a, 1926b.
Jordan and Gilbert, 1881a, 1882.
Jordan and Hubbs, 1925.
Jordan and Jordan, 1922.

Distribution — Continued
Jordan and Metz, 1913.
Jordan and Seale, 1906.
Jordan and Snyder, 1900, 1901.
Jordan and Starks, 1907.
Jordan, Tanaka, and Snyder, 1913.
Kanamura and Imaizumi, 1935.
Kanamura and Yazaki, 1940a, 1940b.
Kimura, 1941, 1942b.
Kishinouye, 1915a, 1919c, 1922c, 1923.
Kochi Pref. Fish. Expt. Sea., 1923b, 1924.
Kumata et al., 1941.
lesson, 1830.
Lord, 1927.
Macleay, 1881.
Martin, 1938.
Matsubara, 1943.
McCulloch, 1922.
Meek and Hildebrand, 1923.
Metz, 1912.
Mori, 1928.

Nakamura, 1938, 1939b, 1943. 1949.
Nichols and Murphy, 1922, 1944.
Okada and Matsubara, 1938.
Okinawa Pref. Fish. Expt. Sta., 1943.
Okuma, Imaizumi, and Maki, 19.35.
Phillipps, 1927a, 1927b.
Phillipps and Hodgkinson, 1922.
Powell, 1937.
Reeves, 1928.
Richardson, 1846.
Roedel, 194Sa, 1948b.
Roughly, 1916.
Samson, 1940.
Schaefer, 1948c.
Schmidt, 19.30.
Schmitt and Schultz, 1940.
Schultz, 1949.
Schultz and DeLacy, 1936.
Seale, 1940.

Serventy, 1941, 1942a, 1942b, 1947, 1948.
Shapiro, 1948a, 1948b.
Smith and Schaefer, 1949.
Snyder, 1904.
Soldatov, 1929.
Soldatov and Lindberg, 1930.
South Seas Govt.-Gen. Fish. Expt. Sta., 1937a, 1937b,

1941a.
Starks, 1918.
Starks and Morris, 1907.
Stead, 1906, 1908.

Takao Prov. Fish. Expt. Sta., 1927.
Tanaka, 1912, 1931.
Taranetz, 1937.
Thomi>son and Higgins, 1919.
Tinker, 1944.
Tirant, 1929.
Tominaga, 1943.
Tubb, 1948.
Ulrey, 1929.

BIBLIOGRAPHY ON PACIFIC TUNAS

33

Distribution — Continued

Ulrey and Greeley, 1928.

Wade, 1949.

Waite, 1907, 1921, 1928.

Walford. 1931, 1937.

Weber, 1913.

Whitphead. 1929, 1931.

Whitley, 1928, 1937, 1947.
Distribution correlated with water temperature

Tal<ayama and Ando, 1934.

Takayama, Ideda, and Ando, 1934.

Uda, 19,H5a, 1935b, 193G, 1940b.

EfXKS

De.Jong, 1940.

Delsnian, 19,31.

Del.sman and Hardenburg, 1934.

Hatai et al., 1941.

Marr, 1948.

Nakannira, 1938, 1949.

Nakamura Res. Staff, 1949.

Watanabe, H., 19.39.

Yabe and Mori, 1948.
Enemies

Bennett, 1840.

Iiuaniura, 1949.

Ki.shinouye, 1923.

Tinker, 1944.

Walford, 1937.

Eiithynnus

Common names

Fisli, 1948.
Distribution
Fish, 1948.

Euthimnus alleterata. See Eutlnjnnus nlletfrratiis.

Euthynnus alleteratiis. See Euthynniis aUctteratus.

Euthjiiintis aUctteratus
Classification

Hildebrand, 1946.

Okadn and Matsubara, 1938.
Common names

Del.sman and Hardenburg, 1934.

FAO, 1949.

Jordan and Evermann, 1905.

Jordan and Jordan, 1922.

Jordan and Snyder, 1901.

Jordan. Tanaka, and Snyder, 1913.

Okada and Matsubara, 1938.

Serventy, 1941.

Tinker, 1944.

Whitley, 1947.
Compared with Euthynnus lineatu-s

Sclimitt and Sehultz, 1940.
Compared with Xlediterraneaii Thynmis thunnina

Teniminck and Schlegel. Is.'iO.
Compared with Thynnus petamys

Cantor, 18.TO.
Compared with M'audcrer wallisi

Wliitley, 1937.

Euthynnus aUctteratus — Continued
Description

Boesemau, 1947.

Cantor, 18.50.

Delsnian and Hardenburg, 19,34.

Fowler, 1904b, 1928.

Giinther. 18G0, 1S7C.

Hildebrand, 194G.

Jordan and Evermann, 1905.

Macleay, 1881.

Meek and Hildebrand, 1923.

Okada and Matsuliara, 1938.

Sen-enty, 1941.

Tinker, 1944.
Distriliution

Bleeker, 1852, 1860a, 1860b, 1861a, lS61b, 1862, 1865a,
lS65b.

Cantor, 1S50.

Chabanaud, 1926.

Chapman, 1946.

Delsman and Hardenburg, 1934.

FAO, 1949.

Fowler, 1928, 1931, 19.38. 1944.

Fowler and Ball, 1925.

Giinther, 1860, 1876.

Herre, 19.32, 1940.

Hildebrand, 1946.

Jenkins, 1903.

Jordan and Evermann, 1905.

Jordan and .Tordan. 1922.

Jordan and Seale, 1906.

Jordan and Snyder, 1901.

Jordan, Tanaka, and Snyder, 1913.

Macleay, 1881.

McCulloch, 1922.

Meek and Hildebrand, 1923.

Okada and Matsubara, 1938.

Riehardson, 1S40.

Schmidt, 19.30.

Schmitt and Schultz, 1940.

Serventy. 1941.

Stead. 1908.

Tanaka, 1931.

Tinker, 1944.

Tirant, 1929.

Weber. 1913.

Whitley, 1947.
Eggs

DeJong, 1940.

Delsman, 1931.

Delsman and Hardenburg, 1934.
Figured

Delsman and Hardenburg, 1934.

Fowler, 1928.

Giinther, 1876.

Jordan and Evermann. 190.">.

Jordan, Tanaka. ,uid Siiyiler. 1913.

Kitahara, 1897.

Serventy, 1941.

Temminck and Schlegel. ISiiO.

Tinker, 1944.

34

FISHERY BULLETIN OF THE FISH AKD WILDLIFE SERVICE

Eiithynnus aJlcttrrntiis — Continued
Food

Hildebrand, 1!>46.
Keys

Delsman and Hardenburg, 1934.

Hildebraud, 194G.

McOulIoch, 1022.

Meek and Hildebrand, 1923.

Okada and Matsubaia, 1938.

Serventy, 1941.
Parasites

Manter, 1940.

Van Cleave, 1940.
Reproduction

Delsman and Hardenburg, 1934.
Synonymy

Boeseman, 1947.

Cbevey, 1934.

FAO, 1949.

Fowler, 1904b, 1928.

Giinther, 1860. 1876.

Hildebrand, 1946.

Jenkins, 1903.

Jordan and Evermann, 1905.

Jordan, Tanaka, and Snyder, 1913.

McCulloch, 1922.

Meek and Hildebrand, 1923.

Richardson, 1846.

Tanaka, 1931.

Weber, 1913.
Young

Delsman, 1931.

Delsman and Hardenburg, 1934.

Giinther, 1889.
Etithi/nnus allittcratus. See Eiitlii/nniis alletteratus.
Eiiflnjtni'us Uneatus
Anatomy

Kisbinouye, 1923.

Schaefer and Marr, 1948b.
Classification

Fraser-Brunner, 1949.

Kisbinouye, 1923.
Common names

Kisbinouye, 1923.

Walford, 1937.
Compared with Eiithiinnus alletteratus

Sehmitt and Schultz, 1940.
Description

Fowler, 1938.

Kisbinouye, 1919c, 1923.

Schaefer and Marr, 1948b.

Seale, 1940.

Walford, 1937.
Distribution

Fowler, 1938, 1944.

Fra-ser-Brunner, 1949.

KLsbinouye, 1919c, 1923.

Roedel, 194.8a.

Schaefer, 1948c.

Schaefer and Marr, 1948b.

Eiitliynnus lincatus — Continued
Description — Continued

Sehmitt and Schultz, 1940.

Seale, 1940.

Walford, 1937.
Figured

Fowler, 1944.

Fraser-Brunner, 1949.

KLsbinouye, 1923.

Schaefer and Marr, 1948b.

Walford, 1937.
Pood

Kisbinouye, 1923.

Walford, 1937.
Habits

Ki.shinouye, 1923.
Keys

Fraser-Brunner, 1949.

Kisbinouye, 1923.

Walford, 1937.
MerLstic characters

Schaefer and Marr, 1948b.
Reproduction

Schaefer, 1948c.

Walford, 1937.
Synonymy

Fowler, 1938, 1944.

Fraser-Brunner, 1949.

Kisbinouye, 1923.
Young

Schaefer, 1948e.

Schaefer and Marr, 1948b.
Enthyiiniis macroptera
Distriltution

Tubb, 1948.
Euthynnus pelamis. See Kntsuwomis prlamis.
Euthynnus pelamys. See Kntsiiironus iiehnnis.
Euthynnvs vagans. See Katsuwonus pelamis.
Euthynnus wallisi
Distribution

Fowler, 1949.
Synonymy

Fowler, 1949.
Euthynnus yaito
Anatomy

Kisbinouye, 191.5a, 191.5b, 1919a, 1923.
Chemical analysis

Miyauchi, 1915.
Classification

Fraser-Brunner, 1949.

Kisbinouye, 1915a, 1923.

Nakamura, 1939b.

Okada and Matsubara, 1938.
Common names

Cbevey, 1932a.

Fujita and Wakiya, 1915.

Herre and Uniali, 1948.

Kisbinouye, 1915a, 1923.

Nakamura. 1939b.

Okada and Matsubara, 1938.

BIBLIOGRAPHY ON PACIFIC TUNAS

35

EiitJniinuis i/aito — Continued
Couimon names — Continued

Shapiro, 19-J8b.

Toniinaga, 1943.
Compared with Wanderer icallisi

Whitley, 1937.
De.scription

Clievey, ]!»32a.

Kishinouye, 1915a, 1923.

Oliada and Matsubara, 1938.

Tominaga, 1943.
Di.stributlon

Chevey, 1932a, 1932b.

Domantay, 1940.

Eckles, 1949a.

Fraser-Brnnner, 1949.

Fnjita and Wakiya, 1915.

Godsil and Greenhood, 1948.

Herre, 1933, 1940.

Jordan and Everniann, 1926a.

Jordan and Hubbs, 1925.

Kishinou.ve, 1915a, 1922c, 1923.

Okada and Matsubara, 1938.

Sphaefer, 194Sc.

Shapiro, 194Sb.

Smith and Schaefer, 1949.

Tominaga, 1943.
Figured

Chevey, 1932a.

Domantay, 1940.

Fraser-Brunner, 19^9.

Kishinouye, 1915a, 1923.

Smith and Schaefer, 1949.
Food

Herald, 1949.

Kishinouye, 1923.

Tominaga, 1943.

Welsh, 1949.
Habits

Kishinouye, 1923.

Tominaga, 1943.
Keys

Brock, 1949.

Fraser-Brunner, 1949.

Kishinouye, 1915a, 1923.

Okada and Matsubara, 1938.
Measurement data

Bonham, 1946.
Parasites

Kishinouye, 1923.
Reproduction

Kishinouye, 1923.

Schaefer, 1948c.
Synonymy

Chevey, 1932a, 19.34.

Fraser-Brunner, 1949.

Jordan and Hubbs, 1925.

Kishinouye, 1923.

Nakamura, 1939b.

EiitliiDDiiix i/ailo — Continued
Young
Kishinouye, 1919b, 1923, 1924.
Schaefer, 1948c.
Euthynux alletteratus. Set- Euthynnus allettcratus.
Evolution
Based on internal anatomy
Kishinouye, 1919a.
Exploitation rates

Tauchl. 1940a, 1940b, 1940c.

Fishing conditions

Correlated with area

Hart and Hollister, 1947.
Hart et al., 1948.

Correlated with astronomical phenomena. See Astro-
nomical phenomena.

Correlated with oceanography. See Oceanographic
conditions.

Correlated with .season
Hart et al., 1948.
Inanami, 1942b.
Whitehead, 1929.
Fishing grounds

Location correlated with oceanography. See Oceano-
graphic conditions.
Food

Anonymous, 1938.

Asano, 1939.

Ban, 1941.

Bennett, 1840.

Chapman, 1946.

Clemens and Wilby, 1946.

Delsman and Hardenburg, 1934.

Eckles, 1949b.

Fitch, 19.50.

Formosa Govt.-Gen. Fish. Expt. Sta., 1933a.

Hart and Hollister, 1947.

Hart et al., 1948.

Hatai et al., 1941.

Herald, 1949.

Hildebrand, 1946.

Imamura, 1949.

Japanese Bur. Fish., 1934, 1939, 1940.

Jordan and (3illiert, ISSlb, 18S2.

Kanamura and Yazaki, 1940a, 1940b.

Kishinouye, 1895, 1915a, 1917b, 192:j.

Kuronuma, 1940.

Marukawa, 19.39.

Miyama, Sartiya, and Hasegawa, 1939.

Nakamura, 1936, 1943. 1949.

Nakamura Res. Staff, 1949.

Okuma, Imaizuml, and Maki, 1935.

Scagel. 1949.

Serventy. 1942a.

Shapiro, 1948a.

Starks, 1918.

Starks and Morris, 1907.

Su.veliiro. 1936, 19.38. 1942.

Taihoku I'rov. Fish. Expt. Sta., 1928, 1929.

36

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Food — Continued
Tinker. 1044.
Tominasa, 1043.
Walford, 1037.
Watanabe, H., 1939.
Welsh, 1949.
Whitley, 1937.
Tabe and Mori, 1948.

Oermo alalunga. See Thuniuis germo.

Germo alntniign. See Thunnus gcrnio.

Germo albacores. See Neotlmnnus itosiU.

Germo argentiviftafus. See Neothioinus argentivittaUis.

Germo germo. See Thnnntis germo.

Germo germon. See Thunnus germo.

Germo macroptenis. See Neothvv»us macroiiterus.

Germo sibi. See Parathtinniis sibi.

Gravity, specific. See Specific gravity, also Oceanographic

conditions.
Growth

Aikawa and Kato, 1938.

Brock, 1943.

Kimura, 1932, 1935.

Kishiuouye, 1923.

Schaefer, 194Sa, in4Sb.
GymnosarcLa afflnis. See Kafsuironns pelamis.
Giimnosarda alletterata. See Euthynnns allettcratus.
Gymnosarda pelamis. See Kcitsuwonus pelamis.

Habits

Brock, 1949.

Iniamnra, 1949.

Jordan and Gilbert, 1882.

Kida, 1936.

Kishinouye, 191.5a, 1923.

jS'akannira, 1049.

Roughly, 1016.

Schaefer, 1048b.

Sei-venty, 1042a.

Shapiro, 1948a.

Tinker. 1944.

Tominasa, 1943.

Ucbida, 1923.

Uda, in.3.5h. 1040a.

Uda and Tsukushi, 1934.
Hermaphroditism

Nakamura, 1935.
Hormones

Jligita and Arakawa, 1948.

Oya and Takahn.shi. 1936.

Toyama et al., 1041.

Juveniles. See Young.

Katsuwonidae
Anatomy

Kishinouye, 1017a, 1919a
Classification

Kishinouye, 1017a.
Compared with AHothunnns fallal

Serventy, 1948.

Katsuwonidae — Continued
Keys

Jordan and Hubbs, 1925.
Katsuiconus pelamis
Age

Aikawa, 1937.
Aikawa and Kato, 1938.
Higashi, 1941b.
Kimura, 1941.
Okamoto, 1940.
Yabe and Mori, 1948.
Anatomy

Eckles, 1949b.
Godsil and Byers, 1944.
Higashi, 1041a.
Imamura, 1049.

Kishinouye, 1015a, 1015b, 1918, 1919a, 1923.
Matsui, 1942a. 1942b.
Suyehiro, 1936, 1038, 1941, 1942.
Body condition
Aikawa, 19.37.
Aikawa and Kato. 1038.
Ikebe and Jlatsumoto, 1037.
Onodera, 1041.

South Seas Govt.-Gen. Fish. Expt. Sta., 1941d.
Suyehiro, 1036, 1038.
Body temperature
Uda, 1041.
Watanabe, N., 1941.
Catch per unit of effort

Kanamura and Yazaki. 1940a, 1940b.
Chemical analysis
Hijrashi and Hirai, 1948.

Kodama, liziika, and Harada, 1934.

Miyania and Osakabe, 1938, 1940.

Miyauchi, 1015.

Okuda, 1918.
Classification

Fraser-Brunner, 19.30.

Godsil and Byers. 1944.

Hildebrand, 1946.

Kishinouye, 101.5a, 1023.

Nakamura, 1939b.

Okada and Matsubara, 1038.

Phillipps, 1027b.

Eoedel, 1948b.

Shapiro, 104Sa.

Soldatov and Llndberg, 1030.

Taranetz, 1037.

Walford, 1031.
Common names

Barnhart, 1036.

Craig, 1929.

Delsman and Hardenburg, 1934.

FAO, 1940.

Fish, 1948.

Fujita and Wakiya, 1915.

Herre and Umali, 1048.

Jordan and Everniann, 1806, 1005.

Jordan and Hubbs, 1925.

BIBLIOGRAPHY ON PACIFIC TUNAS

37

Katsuwonus pelamis — Continued
Common names — Continued

Jordan and Jordan, 1022.

Jordan and Snyder, liiOl.

Jordan, Tanalia, and Snyder, 1913.

Kisliinouye, 191oa, 1923.

Kiunata et al., 1941.

Naknmura, 1939b.

Okada and Matsuhara, 1938.

Phillipps, 1927b.

Roeilel, 194Sb.

Serventy, 1941.

Sliapiro, 1948a, 1948b.

Smith, 1947.

Starks and Morris, 1907.

Taiiaka, 1912.

Tinker, 1944.

Toniinaga, 1943.

Ulrey and Greeley, 1928.

Walford, 1931. 1937.

Whitley, 1947.
Compared with Thynnus afflnis

Cantor, ISoO.
Description

Barnhart, 1936.

Bennett, 1840.

Bleeker, 1856.

Boeseman, 1947.

Clemens and Wilby, 1946.

( 'uvier and Valenciennes, 1934.

Di'lsuian and Hardenburg, 1934.

Eigeumann and Eigenmann, 1890.

Fouler, 1028, 1938.

Fraser-Brunuer, 1050.

Godsil and Byers, 1944.

Giinther, 1860, 1876.

Hildebrand, 1046.

Inianiura, 1940.

Jordan and Evermann, 1905.

Kishinouye, 1915a, 1922b, 1923.

Le.sson, 1830.

Macleay, 1881.

Meek and Hildebrand, 1023.

Nakamura, 1930b.

Okada and Matsubara, 1938.

Roedel, 194Sb.

Seale, 1940.

Serventy, 1041.

Shapiro, 1948a.

Soldatov and Lindberg, 1930.

Stead, 190(!.

Tanaka, 1012.

Temminck and Schlegel, 1&50.

Tinker, 1044.

Toiniiiaga, 1043.

Walford, 1931, 1937.
Distribution

Abe, 1939.

Anonymous, 1941.

Barnhart, 1936.

Katsuwonus pelamis — Continued
Distribution — Continued

Bleeker, 1856, 1860a, 1862, 1865a.

Chapman, 1046.

Clemens and Wilby, 1046.

Cuvier and Valenciennes, 1831.

Del.snian and Hardenburg, 1934.

Doniantay, 1040.

Eekles, 1940a.

Eigenmann, 1892.

Eigenmann and Eigenmann, 1890, 1891.

Evermann and Seale, 1907.

FAO, 1949.

Fi.sh, 1948.

Fowler, 1928, 1931, 1934, 1938, 1944, 1949.

Fraser-Brunner, 19.50.

Fujita and Wakiya, 1915.

Godsil and Greenhood, 1948.

Gunther, 1860, 1876.

Herre, 1932, 1033, 1935, 1936, 1940.

Hildebrand, 1946.

Imamura, 1949.

Jenkins, 1903.

Jordan and Evermann, 1896, 1905.

Jordan and Hubbs. 1025.

Jordan and Jordan, 1922.

Jordan and Seale, 1006.

Jordan and Snyder, 1001.

Jordan and Starks, 1907.

Jordan, Tanaka, and Snyder, 1913.

Kanamura and Yazaki, 1040a, 1040b.

Kimura, 1041, 1942b.

Kishinouye, 1015a, 1023.

Kumata et al., 1041.

Lesson, 1830.

Macleay, 1881.

Martin, 1038.

Matsubara, 1943.

McCulloch, 1022.

Meek and Hildebrand, 1923.

Nakamura, 1939b.

Nichols and Murphy, 1944.

Okada and Matsubara, 1938.

Okinawa Pref. Fish. Expt. Sta., 1943.

Phillipps, 1027a, 1927b.

Phillipi)s and Hodgkinson, 1022.

Reeves, 1928.

Richardson, 1846.

Roedel, 1948b.

Roughly, 1916.

Schaefer, 1948c.

Seale, 1940.

Serventy, 1041, 1947.

Shapiro, 194Sa, 1948b.

Smith and Schaefer. 1940.

Soldatov and Lindberg, 1930.

South Seas Govt.-Gen. Fish. Expt. Sta., 1937a.

Starks and Morris, 1907.

Stead, 1906, 1908.

Tanaka, 1912, 1931.

38

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Katsuivonus pelamis — Continued
Distribution — Continued

Taranetz, 1937.

Tinker, 1944.

Tominaga, 1943.

Ulrey, 1929.

Ulrey and Greeley, 1928.

Waite, 1907.

Walford, 1931, 1937.

Whitehead, 1929.

Whitley, 1947.
Distribution correlated with water temperature

Takayama, Ikeda, and Ando, 1934.

Uda, 1935b, 1936, 1940b.
Egss

Hatai et al., 1941.

Marr, 1948.

Nakanmra Re.s. Staff, 1949.

Yabe and Mori, 1948.
Enemies

Imaraura, 1949.

Tinker, 1944.
Figured

Barnhart, 1936.

Clemens and Wilby, 1946.

Cuvier and Valenciennes, 1831.

Domantay, 1940.

Eckles, 1949a.

Fraser-Brunner, 1950.

Godsil and Byers, 1944.

Jordan and Evermann, 1905.

Kishinouye, 1915a, 1923.

Kitahara, 1897.

Kumata et al., 1941.

Lesson, 1830.

McCulloch, 1922.

Nakamura, 19.39b.

Roedel, 1948b.

Serventy, 1941.

Shapiro, 1948a.

Smith and Schaefer, 1949.

Tanaka, 1912.

Temminck and Schlegel, 1850.

Tinker, 1944.

Walford, 1931, 1937.
Fishing conditions correlated with oceanography

Aikawa, 19.33.

Chiba Pref. Fish. Expt. Stn., Katsuura Br., 1936, 1937,
1938, 1941.

Formosa Govt.-Gen. Fish. Expt. Sta., 1930, 1931, 1932,
1933b, 1934.

Imamura, 1949.

Inanami, 1941, 1942d.

Kagoshima Pref. Fish. Expt. Sta.. 1025, 1926a, 1926b,
1927b, 1928a, 1929a. 1930ii, 1931a, 1932a, 1933a, 1935,
1936a, 1937.

Kanamura and Yazaki, 1940b.

Kawamura, 1939.

Kimura, 1941, 1949.

Kochi Pref. Fish. Expt. Sta., 1923a.

Katsiiironus pcUimis — Continued

Fishing conditions correlated with oceanography — Con.

Kumamoto Pref. Fish. Expt. Sta., 1946.

Mie Pref. Fish. Expt. Sta., 1930a, 1930b, 1930d.

Okinawa Pref. Fish. Expt. Sta., 1940a, 1943.

Sasaki, 1939a.

Shapiro, 1948a.

Shimamura, 1927.

Shizuoka Pref. Fish. Expt. Sta., 1936, 1937.

South Seas Govt.-Gen. Fish. Expt. Sta., Iii37c, 1938.
1942, 1943b.

Taihoku Prov. Fish. Expt. Sta., 1927a, 1927b, 1929,
1932.

Takayama, Ikeda, and Ando, 1934.

Uda, 1935b, 1938, 1939, 1940c.

Uehara, 1941.

Yabe and Mori, 1948.
Fishing conditions correlated with weather

Kanamura and Yazaki, 1940b.

Okinawa Pref. Fish. Expt. Sta., 1940a, 1943.

Taihoku Prov. Fish. Expt. Sta., 1927a, 1927b.

Uda and Watanabe, 1938.
Food

Clemens and Wilby, 1946.

Delsman and Hardenburg, 1934.

Eckles, 1949b.

Hatai et al., 1941.

Hildcbrand, 1946.

Imamura, 1949.

Kishinouye, 1917b, 192.3.

Nakamura Res. Staff, 1949.

Shapiro, 1948a.

Suyehiro, 1936, 1938, 1942.

Taihoku Prov. Fish. Expt. Sta., 1928, 1929.

Tinker, 1944.

Tominaga, 1943.

Walford, 1937.

Yabe and Mori, 1948.
Growth

Aikawa and Kato, 1938.
Habits

Imamura, 1949.

Kishinouye, 1923.

Shapiro, 1948a.

Tinker, 1944.

Tominaga, 1943.

Uchida, 1923.

Uda, 1935b, 1940a.

Uda and Tsukushi, 19.34.
Hermaphroditism

Nakamura, 1935.
Hormones

Miglta and Arakawa, 1948.

Oya and Takahashi, 1936.

Toyama et al., 1941.
Keys

Brock, 1949.

Delsman and Hardenburg, 1934.

Fraser-Brunner, 1950.

Godsil and Byers, 1944.

BIBLIOGRAPHY OX PACIFIC TUNAS

39

Katsuwonus pelamis — Continued
Keys — Cimtin\UMl

HiMebratKl. 104f).

Kishinoiiye. lOlya, 1923.

MtCull(Hh, lft22.

Meek and Hildebraiul. 1923.

Okaila an.-i Mat.subara, 1938,

Roedel, 1948b.

Serventy, 1941.

Soldatov and Lindber^', 1930.

Tai-iUietz, 1937.

Walford, 1931, 1937.
Length-weiglit relation

Bonham, 1946.
Measurement data

Aikawa and Kato, 1938.

Bonham, 1946.

Godsil and Byers. 1944.

Higashi, 1940a, 1040b, 1941a, 1941b, 1942.

Ikebe and Matsumoto. 1937.

Kagoshima Pref. Fish. Expt. Sta., 192.">, 1926a, 192Tb,
192Sa, 1929a, 1936a, 1937, 1938a, 1939a, 1940a, 1941.

Kodama, liziika, and Harada, 1934.

Marr, 1948.

Nakamura Res. Staff, 1949.

Oita Pref. Fish. E.xpt. Sta., 1925.

Okianwa Pref. Fish. Expt. Sta., 1931.

Onod'ra, 1941.

Schaefer, 1948b.

South Seas Govt.-Gen. Fish. Expt. Sta., 1941d.

Suyehiro, 1936, 193S.

Expt. Sta., 1928, 1929.

Fish.

Taihnku Prov.

Uda, 1941.

Watanabe. N., 1941.

Yabe and Mori, 1948.

Yamamoto, 1940.
Meristic characters

Codsil and Byers, 1944.

Nakamura Res. Staff, 1949.
Migration

Hatai et al., 1941.

Imamura, 1949.

Kiniura, 1941, 1942b.

Kishinouye, 1923.

Mats\ibara, 1943.

Matsumoto, 1937.

Sasaki, 19.39a.

Shapiro. 194Sa, 1948b.

Tominaga, 1943.

Uda, 1936.

Walford, 1937.
Parasites

Bennett, 1840.

Haraila, 1928.

Kishinouye, 1923.

Manter, 1940.

Van Cleave, 1940.
Populations
Aikawa, 1937.
Godsil and Byers, 1944.

Katsuiconus pelamis — Continued
Populations — Continued
Imamura, 1949.
Tauchi, 1941.
Tominaga, 1943.

Uda and Tsukuslii, 1934.
Reproduction

Eckles, 1949b.

Hatai et al., 1941.

Imamura, 1949.

Kishinouye, 1923.

Marr, 1948.

Schaefer, 1948c.

Schaefer and Marr, 1948a.

Shapiro, 194Sb.

Walford, 1937.

Yabe and Mori, 1948.
Sex ratio

Ikebe and Matsumoto. 1937.

Marr, 1948.

Nakamura Res. Staff, 1949.
Sexual dimorphi.sm

Hatai et al., 1941.
Sexual maturity

Hatai et al., 1941.

Marr, 194S.

Matsuliara. 1943.

Matsui, 1942b.

Nakamura Res. Staff, 1949.

Okinawa Pref. Fish. Expt. Sta., 1931.

Schaefer and Marr, 1948a.

Yabe and Mori, 1948.
Size composition

Aikawa, 1937.

Aikawa and Kato, 1938.

Inanami, 1942b.

Kagoshima Pref. Fish. Expt. Sta., 1937.

Kimura, 1941.

Nakamura Res. Staff, 1949.

Okamoto, 1940.

Sasaki, 1939a.

Uda, 193.5b.

Uda and Tsukushi, 1934.

Yabe and Mori, 1948.
Swinuuing velocity

Watanabe, N., 1941.
Synonymy

Bleeker, 1856.

Boeseman, 1947.

Everniann and Seale, 1907.

F.VO, 1949.

Fish. 1948.

Fowler, 1928, 1934, 1944, 1949.

Fraser-Brunner, 19.50.

Giinther, 1S60, 1876.

Herre, 1936.

Hildelirand, 1946.

Jenkins, 1903.

Jordan and Evermann. 1896, 1905.

Jordan, Tanaka, and Snyder. 1913.

40

FISHERY BULLErriN OF THE FISH AND WILDLIFE SERVICE

Katsuwonus pelamis — Continued
Synonymy — Continued

Kishinouye, 1023.

MeCulloch, 1922.

Meek and Hildebrand, 1923.

Nakamura, 1939b.

Philllpps, 1927b.

Richardson, 1846.

Soldatov and Lindberg, 1930.

Tanaka, 1912, 1931.

Ulrey and Greeley, 1928.

Waite, 1907.
Tagging

Anonymous, 1939.

Fukuda and lizuka, 1940b.

Godsil, 1938.

Kagoshima Pref. Fi.sh. Espt. Sta., 1928a, 1936b, 1938b,
1939b, 19401).

Matsumoto, 1937.

South Seas Govt.-Gen. Fish. Expt. Sta., 1941c.

Uda, 1936.
Toung

Eckles, 1949b.

Hatai et al., 1941.

Inanami, 1942o.

Kishinouye, 1019b, 1923, 1924, 1926.

Marr, 1948.

Sehaefer, 1948c.

Schaefer and Marr, 1948a.

Yabe and Mori, 1948.
Toung as food of tuna

Kishinouye, 1917b.

Marukawa, 1939.
Katsuifonus pelamys. See Kntsuicovtis pelamis.
Katmiwomis tJagans. See Kat.s-uironiis pelamis.
Kaiicomis vayans. See Katsuwonus pelamis.
Key.*!

Brock, 1949.

Delsman and Hardenburg, 1934.
Fraser-Brunner, 1040, 1950.
Godsil and Byers, 1944.
Hildebrand, 1946.
Jordan and Evermann, 1926b.
Jordan and Hulibs, 1925.
Kishinouye, 1915a, 1923.
MeCulloch, 1922.
Meek and Hildebrand, 1023.
Nakamura, 1040.
Okada and Matsubara, 1938.
Roedel, 194Sb.
Serventy, 1941.
Soldatov and Lindberg, 1930.
Taranetz, 1937.
Wade, 1949.
Walford, 1931, 1937.
Eish inoella
Keys

Soldatov and Lindberg, 1930.

EishiiwcUa rnra
Classification

Nakamura, 1939b.

Okada and aiatsubara. 1038.
Common names

Jordan and Evennann, 1026b.

Jordan and Hubbs, 1925.

Nakamura, 1939b.

Okada and Matsubara. 1938.
Compared with Eisliiiioclhi zacalles

Nakamura, 1939b.
Description

Jordan and Evermann. 1926b.

Jordan and Hubbs. 1925.

Nakamura, 1939b.

Okada and Matsubara, 1938.
Distribution

Jordan and Evermann, 1926a, 1926b.

Jordan and Hubbs, 1925.

Nakamura. lO.'iOb.

Okada and Matsubara, 1938.
Figured

Nakamura, 1939b.
Keys

Brock, 1949.

Jordan and Evermann. 1926b.

Okada and Matsubara, 1938.
Synonymy

Nakamura, 1939b.
Kish inoella tont/r/ol
Anatom.y

Serventy, 1942b.
Common names

Serventy, 1941.

Whitley, 1947.
Compared with Kishinorlla zacalles

Serventy, 1942b.
Compared with Ncoihunnus varus

Serventy, 1942b.
Compared with Thunnux niaeeoyi

Sei-venty, 1041.
Compared with Thunnus nicolsoni

Serventy, 1942b.
Compared with Thunnus tonggol

Serventy, 1942b.
Description

Serventy, 1941, 1942b.
Distiibution

Serventy, 1941, 1942a, 1942b.

Whitley, 1947.
Figured

Serventy, 1941, 1942b.
Food

Serventy, 1942a.
Habits

Serventy, 1942a.
Keys

Serventy, 1941.
Length-weight relation

Serventy, 1941.

BIBLIOGRAPHY ON PACIFIC TUNAS

41

Kishinoelln tonijijol — Continued
Measurement data

Serventy, 1942b.
Reproduction

Serventy, 1042a.
Synonymy

Serventy, 1942b.
KUhinoclla zacalles
Classification

Fraser-Brunner, 1950.

Nicliols and LuMonle, 1941.
Compared witli Kinliiiwclla rara

Nakamura. 19:!9b.
Compared with KiHhinoella tonggol

Serventy, 1942b.
Description

Fraser-Brunner, 19.50.

Jordan and Everniann. 1926b.
Distribution

Fraser-Brunner, 10.10.

.Jordan and Bvermann, 1926b.
Figured

Fraser-Brunner, 19,")0.

Jordan and Everniann, 1926b.
Keys

Fra.?er-Brunner, 19.50.

Jordan and Everniann. 1926b.
Synonymy

FVaser-Brunner, 1950.

Length-weight data. See Morphometries.

Maclierel, frigate. See Auxis spp.
Management

Scbaefer, 194Sc.
Maturity

Anonymous, 1938.

Ban, 1941.

Clark, 1929.

Hatai et al., 1941.

Ikebe, 1939.

Imaizumi, 1937.

Kanamura and Imaizumi, 1935.

Kanamura and Yazaki, 1940a, 1940b.

Kato, 1940.

Marr, 1948.

Matsubara, 1943.

Matsui, 1042b.

Nakamura, 1938.

Nakamiira Res. Staff, 1949.

Okinawa Pref. Fish. Expt. Sta.. 1931.

Okuma, Imaizumi, and Maki, 1935.

Schaefer, 1948b.

Scbaefer and Marr, 1948a.

Soc. Prom. Ocean. Fish., 19.36.

Watanabe, H., 1930.
Measurement data. See Morphometries.
Migration.

Cobb, 1919.

Hatai et al., 1941.

Migration — Continued
Imamura, 1949.
Kimura, 1941, 1942b.
Kishinouye, 1923.

Koehi Pref. Fisli. Expt. Sta., 1923b, 1924.
Matsubara, 1943.
Matsiimoto, 1937.
Nakamura, 1943, 1949.
Sasaki, 1939a, 1939b.
Serventy, 1941.
Shapiro, 104Sa, 104Sb.
Soc. Prom. Ocean. Fish., 1936.
Tauclii, 194()b.
Tominaga, 1943.
Uda, 1936.
Walford, 1937.
Whitehead, 1931.
Morphometries

Length-weight relation

Bonhani, 1946.

Hiratsuka and Morlta, 1935.

Schaefer, 1948a.

Serventy, 1941.
Measurement data

Aikawa and Kato, 1938.

Anonymous, 1938.

Bonham, 1946.

Brock, 1043, 1940.

Formosa Govt.-Gen. Fish. Expt. Sta., 1933a.

Godsil, 1948.

Godsil and Byers, 1944.

Higashi, 1940a, 1940b, 1911a, 1941c, 1942.

Hiratsuka and Imaizumi, 1934.

Hiratsuka and Ito, 1934.

Ikebe, 1939, 1040a, 19401), 1040c, 1041a, 1941b.

Ikebe and Matsumoto, 1037.

Inanami, 1940a.

Japanese Bur. Fish., 1930, 1940.

Kagoshima Pref. Fish. Expt. Sta., 1925, 1926a. 1027b,
1928a, 1929a, 1036a, 1937, 1938a, 193!)a, 1940a, 1941.

Kanamura and Imaizumi, 1935.

Kanamura and Tazaki, 1940a, 1940b.

Kdihinia, lizuka, and Harada, 1934.

Marr, 1948.

Miyama, Saruya, and Hasegawa, 1939.

Nakamura, 1036, 1930a, 1930b.

Nakamura Res. Staff, 1949.

Oita Pref. Fish. Expt. Sta., 1925, 1927a. 1027b, 1930.

Okinawa Pref. Fisli. Expt. Sta.. 1931.

Okuma, Imaizumi, and Maki. 1935.

Onodera, 1941.

Schaefer, 1948a, 194Sb.

Serventy, 1942b, 1948.

South Seas Govt.-Gen. Fish. Expt. Sta., 1941d, 1943a.

Suyehiro, 1036, 1938.

Tailioku Pi-ov. Fish. Expt. Sta., 1028, 1029.

Uda, 1932, 1941.

Uno, 1036b.

Wade, 1949.

Watanalie, Ilajinie, 1939.

42

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

M(iri)hometrics — Continued
Measurement data — Continued

Watanabe, Haruo, 1940.

Watanabe, N., 1941.

Tabe and Mori, 1948.

Yaiuamoto, 1940.
Meristic characters

Clark, 1929.

Godsil and Byers, 1944.

Nakamura Re.s. Staff, 1949.

Schaefer and Marr, 1948b.

Wade, 1949.
Methods of measurement

Godsil, 1948.

Godsil and Byers, 1944.

Marr and Schaefer, 1949.
Sex ratio

Brock, 1943.

Ikebe and Matsumoto, 19.37.

Marr, 194S.

Miyama, Saruya, and Hasegawa, 1939.

Nakamura Res. Staif, 1949.

Ncothiinnus

Compared with ScmatliK units

Fowler, 1933.

Nakamura, 1939a.
New species recorded

Jordan and Bvermann, 1926a.
Neotliunmis albacora
Classification

Nichols and LaMonte, 1941.
Common names

Nichols and LaJIonte, 1941.
Description

Nichols and LaMonte, 1941.
Keys

Nichols and LaMonte, 1941.
Synonymy

Nichols and LaMonte, 1941.
Nrothvnnus alhacora alhacoin. See Ncoihunnns anacora.
Nrothnnmis albacora macropterus. See Neotliunnus

macropterus.
NeotMmnns allisonl
Classification

Nichols and LaMonte, 1941.
Common names

Nichols and LaMonte, 1941.
Compared with Ncothuniins macropterus

Walford, 1937.
Description

Nichols and LaMonte, 1941.
Keys

Nichols and LaMonte. 1941.
Synonymy

Nichols and LaMonte, 1941.
Neotliunnus alUsoni allisoni. See Neotliunnus allisoni.
Ncothunnus allisoni itosibi. See Neotliunnus itosihi.

Neotliunnus argentivittatus
Common names

Nichols and Mui-phy, 1922.
Description

Nichols and Murphy, 1922.
Distribution

Fowler, 1944.

Jordan and Jordan, 1922.

Nichols and Murphy, 1922.
Neotliunnus catalinae
Classification

Nichols and LaMonte, 1941.
Common names

Craig, 1929.

Nichols and LaMonte, 1941.
Description

Jordan and Evermann, 1926b.

Nichols and LaMonte, 1941.
Distribution

Jordan and Evermann, 1926b.

Ulrey, 1929.
Figured

Jordan and Evermann, 1926b.
Keys

Jordan and Evermann, 1926b.

Nichols and LaMonte, 1941.
Synonymy

Nichols and LaMonte, 1941.

Neotliunnus itosibi
Classification

Nichols and LaMonte, 1941.

Okada and Matsnbara, 1938.
Common names

Jordan and Evermann, 1926b.

Okada and Matsubara, 1938.
Compared with Neotliunnus macropterus

Nakamura, 1939a, 1939b.
DescriiJtion

Fowler, 1928.

Jordan and Evermann. 1926b.

Okada and Matsubara, 1938.

Powell, 1937.
Distribution

Domantay, 1940.

Fowler, 192S.

Jordan and Evermann, 1926b.

Martin, 1938.

Okada and Matsubara, 1938.

Powell, 1937.
Figured

Domantay, 1940.

Jordan and Evermann. 1926b.

Powell, 1937.
Keys

Jordan and Evermann. I'.t26b.

Okada and Matsubara, 1938.
Synonymy

Fowler, 1928.

Powell, 1937.

BIBLIOGRAPHY ON PACIFIC TUNAS

43

Ifeothtiiniiix nuicroptrnis
Age

Aikawa iind Kato, 1938.

Ban, 1941.

Higashi, 1941b.

Ikebe, 19:!9, 194(la. 1940h, lOJOc. 1941a, 1941b.

Kanamura and Yazaki, 1940a, 1940b.

Kiiimra, 1942a.

Schaefer, 1948b.

Tauchi, 1940b.
Anatomy

Fish, 1948.

Godsil and Byers, 1944.

Higashi, 1941e.

Kishinouye, 1915a, 1915b, 1919a, 1922a, 1923.

Matsui, 1942a.

Migita and Arakawa, 1948.

Nakamura, 1949.

Suyehiro, 1941, 1942.
Body condition

Aikawa and Kato, 1938.

Ikebe, 1939.

Kanamura and Yazaki, 1940a, 1940b.
Body temperature

Anonymous, 1938.

Kanamura and Imaizuuii, 1935.

Kanamura and Yazaki, 1940a, 1940b.

Nakamura, 1941.

Oita Pref. Fish. Expt. Sta., 1927a, 1930.
Catch per unit of effort

Formosa Govt.-Gen. Fish Expt. Sta., 1933a.

Hiratsuka and Iniaizumi, 19.34.

Hiratsuka and Ito, 1934.

Imaizuuii, 1937.

Kanamura and Imaizuuii, 1935.

Kanamura and Yazaki, 1940a, 1940b.

Nakamura, 1949.

Okuma, Imaizumi, and Maki, 1935.
Chemical analysis

Dill, 1921.

Higashi and Hirai, 1948.

Miyania and Osakabe, 1940.

Miyama, Saruya, and Hasegawa, 1939.
Classification

Fra.ser-Brunner, 1950.

Godsil and Byers, 1944.

Hildebrand, 1946.

Kishinouye, 191.ja, 1923.

Nakamura, 1939a, 1939b, 1943, 1949.

Nichols and LaJIonte, 1941.

Okada and Matsubara, 1938.

Roedel, 194Sb.

Schaefer, 194Sa.

Shapiro, 194Sa.

Soldatov and Lindberg, 1930.

Taranetz. 19:'.7.

Walford. 1931.
Coiiimun names

Barnhart, 1936.

Delsman and Hardenburg, 1934.

Neothtimius macropterus — Continued

Common names — Continued

FAO, 1949.

Fi.sh, 194S.

Fujita and Wakiya, 1915.

Herre and Uniali, 1948.

Jordan and Evermann, 1926b.

Jordan and Hubbs, 1925.

Jordan and Jordan, 1922.

Jordan and Snyder, 1901.

Jordan, Tanaka, and Snyder, 1913.

Kishinouye, 1915a, 1923.

Kumata et al., 1941.

Nakamura, 1939b. 1943, 1949.

Okada and Matsubara, 1938.

Roedel, 1948b.

Serventy, 1941.

Shapiro, 1948a, 1948b.

Smith, 1947.

Starks and Morris, 1907.

Tinker, 1944.

Ulrey and Greeley, 1928.

Walford, 1931, 1937.

Whitley, 1947.
Compared with Neothiinntis allisoni

Walford, 1937.
Compared with Xeoth minus itosibi

Nakamura, 1939a, 1939b.
Compared witli Parathunnuti iiiehachi

Roedel, 1948b.
Compared with Semathuiniiis yuildi

Nakamura, 1939b.
Compared with Tluinniis tinjiniiis

Thompson and Biggins, 1919.
Description

Barnhart, 1936.

Boeseman, 1947.

Delsman and Hardenburg, 1934.

Fowler, 1928.

Fraser-Brunner, 1950.

Godsil and Byers, 1944.

Hildebrand. 1946.

Jordan and Evermann, 1926b.

Jordan and Hubbs, 1925.

Jordan and Jordan, 1922.

Jordan and Starks, 1907.

Kishinouye, 1915a, 1923.

Matsubara, 1943.

Nakamura, 19.S9b. 1949.

Okada and Matsubara, 1938.

Roedel, 194Sb.

Seale, 1940.

Serventy, 1941.

Shapiro, 1948a.

Soldatov and Lindberg. 1930.

Starks, 1918.

Teniniinck and Schle!;el. 1N">0.

Thompson and Higgins, 1919.

Tinker, 1944.

Walford, 1931, 1937.

44

FISHERY BULLEITIN OF THE FI&H AK.D WILDLIFE SERVIC7E

Neotluinmis macroptents — Continued
Distribution
Abe, 1939.
Anonymous, 1938.
Barnhart, 1936.
Bleeker, 1852, 1862, 1865a.
Chapman, 1946.
Chu, 1931.

Delsman and Hardenburg, 1934.
Domantay, 1940.
Eckles, 1949a.
FAO, 1949.
Fish, 1948.

Formosa Govt.-Gen. Fish. Expt. Sta„ 1933a.
Fowler, 1923a, 1928, 1931, 1938, 1949.
Fi'aser-Brunner, 1950.
Fujita and Wal^iya, 1915.
Godsil and Greenhood, 1948.
Herre, 1932, 1935, 1936, 1940.
Hildebrand, 1946.
Hiratsuka and Imaizumi, 1934.
Hiratsuka and Ito, 1934.
Holder, 1912.
Hubbs, 1916.
Imaizumi, 1937.
Japanese Bur. Fish., 1934.
Jordan and Evermann, 1926a, 1926b.
Jordan and Hubbs, 1925.
Jordan and Jordan, 1922.
Jordan and Seale, 1906.
Jordan and Snyder, 1901.
Jordan and Starks, 1907.
Jordan, Tanaka, and Snyder, 1913.
Kanaraura and Imaizumi, 1935,
Kanamura and Yazaki, 1940a, 1940b.
Kimura, 1942b.
Kishinouye, 1915a, 1923.
Kochi Pref. Fish. Expt. Sta., 1923b, -924.
Kumata et al., 1941.
Martin, 1938.
Matsubara, 1943.
Nakamura, 1939b, 1943. 1949.
OUada and Matsubara, 1938.
Okuma, Imaizumi, and Maki, 1935.
Reeves, 1928.
Richardson, 1846.
Roedel, 1948b.
Schaefer, 1948c.
Seale, 1940.
Serventy, 1941.
Shapiro, 1948a, 1948b.
Smith and Schaefer, 1949.
Soldatov and Lindberg, 19.30.
South Seas Govt.-Gen. Fish. Expt. Sta., 1937a.
Starks, 1918.
Starks and Morris, 1907.
Takao Prov. Fish. Expt. Sta., 1927.
Tnnaka, 19.31.
Taranetz, 1937.
Temminck and Schlegel, 1850.

Neotliimnus macroptents — Continued
Distribution — Continued
Tinker, 1944.
Ulrey, 1929.

Ulrey and Greeley, 1928.
Walford, 1931, 1937.
Whitley, 1928, 1947.
Distribution correlated with water temperature
Takayama and Ando, 1934.
Uda, 1935a.
Exploitation rates

Tauchi, 1940b.
Figured

Anonymous, 1938.
Barnhart, 1936.

Delsman and Hardenburg, 1934.
Domantay, 1940.
Eckles, 1949a.
Fraser-Brunner, 19.50.
Godsil and Byers, 1944.
Jordan and Evermann, 1926b.
Jordan and Starks, 1907.
Kishinouye, 1915a, 1923.
Kitahara, 1897.
Kumata et al., 1941.
Nakamura, 1949.
Roedel, 1948b.
Serventy, 1941.
Shapiro, 1948a.
Starks, 1918.

Temminck and Schlegel, 1850.
Tinker, 1944.
Walford, 1931, 1937.
Fishing conditions correlated with astronomical phe-
nomena
Takao Prov. Fish. Expt. Sta., 1927.
Fishins conditions correlated with oceanography
Aikawa, 1933.
Ban, 1941.

Formosa Govt.-Gen. Fish. Expt. Sta., 1933a.
Hiratsuka and Imaizumi, 1934.
Hiratsuka and Ito, 1934.
Ikebe, 1940d, 1942.
Inanami, 1940b, 1940c, 1941, 1942d.
Japanese Bur. Fish., 1934.
Kagosbima Pref. Fish. Expt. Sta., 1926b, 1927a, 1928b,

1929b, 1930b, 1930e, 1931b, 1932b. 1933b.
Kanamura and Imaizumi, 19.35.
Kanamura and Yazaki, 1940a, 1940b.
Kawamura, 1939.
Kimura, 1942a.
Kinuira and Ishii, 1933.
Mie Pref. Fish. Expt. Sta., 1930c, 1930e.
Nakamura, 1949.
Oita Pref. Fish. Expt. Sta., 1930.
Okunia, Imaizumi, and Maki, 1935.
Shapiro, 1948a.
South Seas Govt.-Gen. Fish. Expt. Sta., 1937a, 1938,

1941b, 1942, 1943b.
Takao Prov. Fish Expt. Sta., 1927.

BIBLIOGRAPHY ON PACIFIC TUNAS

45

Neothunnus macropterus — Continued

Fishing conditions correlated with oc(>anography — Con.
Takayama and Ando, 1934.
Uehara, 1041.
Fishing conditions corrchited with weather
Formosa Govt. -Gen. Fish. Expt. Sta., 1933a.
Hiratsuka and Imaizumi, 1934.
Hiratsuka and Ito. 1934.
Kanamura and Yazaki, 1940a, 1940b.
Oita Pref. Fish. Expt. Sta., 1930.
Okuma, Imaizumi, and Maki, 1935.
Food

Anonymous, 1938.
Ban, 1941.
Chapman, 1946.
Fitch, 1950.

Formosa Govt.-Gen. Fish. Expt. Sta., 1933a.
Herald, 1949.
Hildebrand, 1946.
Japanese Bur. Fish., 1934.
Kanamura and Imaizumi, 1935.
Kanamura and Yazaki, 1940a, 1940b.
Kishinouye, 191Tb, 1023.
Marukawa, 19.39.

Miyania, Saruya, and Hasegawa, 1939.
Nakaniura, 1936, 1943, 1949.
Okuma, Imaiziirai, and Maki, 1935.
Shapiro, 194Sa.
Su.vehiro, 1942.
Tinker, 1944.
Walford, 1937.
Growth
Aikawa and Kato, 1938.
Kimura, 1932, 1935.
Kishinouye, 1923.
Schaefer, 1948a, 1948b.
Habits

Kishinouye, 1923.
Nakaniura, 1949.

Schaefer, 194Sb.

Shapiro, 1948a.
Hormones

Migita and Arakawa, 1948.

Toyama et al., 1941.
Keys

Brock, 1949.

Delsman and Hardenburg, 1934.

Fraser-Brunner, lO.'O.

Godsil and Byers, 1044.

Hildebrand, 1946.

Jordan and Evermann, 1926b.

Kishinouye, 1915a, 1923.

Nakaniura, 1949.

Okada and Matsubara, 1938.

Roedel, 1948b.

Serventy, 1941.

Soldatov and Lindberg, 1930.

Taranetz, 1037.

Wallord, 1931, 1937.

Ncoth iiiinus macropterus — Continued
Length-weight relation

Hiratsuka and Morita, 1935

Schaefer, 194Sa.
Measurement data

Aikawa and Kato, 1938.

Anonymous, 19.38.

Bonham, 1046.

Formosa Govt.-Gen. Fisli. Expt. Sta., 1933a.

Godsil, 1948.

Godsil and Byers, 1944.

Higa.shi, 1940a, 1941b, lOllc, 1042.

Hiratsuka and Imaizumi, 1934.

Hiratsuka and Ito, 1034.

Ikebe, 1039, 1040a, 104(ib, 1040c, 1941a, 1941b.

Inanami, 1940a.

Kanamura and Imaizumi, 10.35.

Kanamura and Yazaki, 1040a, 1940b.

Marr, 1948.

Miyama, Saruya, and Hasegawa, 19.39.

Nakamura, 19.36, 1939a, 1930b.

Oita Pref. Fish. Expt. Sta., lOL'.". 1027a, 1027b, 1930.

Okuma, Imaizumi, and Maki, 1935.

Schaefer, 1948a, 194Sb.

South Seas Govt.-Gen. Fish. Expt. Sta., 1943a.

Watanabe, H., 1940.
Meristic characters

Godsil and Byers, 1044.
Migration

Kochi Pref. Fish. Expt. Sta., 1923b, 1924.

Nakamura, 1943.

Shapiro, 1948a.

Tauchi, 1940b.

Walford, 1937.
Parasites

Kishinouye, 1923.
Populations

Godsil, 1948, 1049.

Godsil and Byers, 1944.

Tauchi, 1040b.
Reproduction

Hatai et al., 1041.

Ikebe, 1041b.

Kishinouye, 1923.

Marr, 1948.

Nakaniura, 103!)b, 1943, 1949.

Schaefer, 194Se.

Schaefer and Marr, 1948a.

Tinker, 1944.

Walford, 1937.
Sex ratio

Marr, 1948.

Miyama, Saruya, and Hasegawa, 1939.
Sexual maturity

Anonymous, 1938.

Ban, 1941.

Hatai et al., 1941.

Ikebe, 1039.

Imaizumi, 1037.

Kanamura and Imaizumi, 1935.

46

FISHERY BULLErriN OF THE FISH AA'D WTLDLIFE SERVICE

Neothunnus macroptervs — Continued
Sexual maturity — Continued

Kanamura and Yazaki, 1940a, 1940b.

Kato, 1940.

Marr, 1948.

Okuma, Imaizumi, and Maki, 1935.

Schaefer, 1948b.

Schaefer and Marr, 1948a.
Size composition

Aikawa and Kato, 1938.

Kiniura, 1932, 1942a.

Scliaefer, 1948b.

Schaefer and Marr, 1948a.

Tauehi, 1940b.
Survival rates

Tauehi, 1940b.
Synonymy

Boeseman, 1947.

Chu, 1931.

FAO, 1949.

Fish, 1948.

Fowler, 1928, 1931, 1949.

Fraser-P.runner, 1950.

Herre, 1936.

Hildebrand, 1946.

Jordan and Hubbs, 1925.

Jordan and Starks, 1907.

Jordan, Tanaka, and Snyder, 1913.

Kishinouye, 1923.

Nakamura, 19.39a, 19.S9b, 1949.

Richardson, 1846.

Soldatov and Lindberg. 1930.

Tanaka, 1931.

Ulrey and Greeley, 1928.
Tagging

Godsil, 1938.
Young

Kishinouye, 1924, 1926.

Schaefer, 1948c.

Schaefer and Marr. 1948a.
Neothunnus ranis
Anatomy

Kishinouje, 1915a, 1915b, 1923.

Nakamura, 1949.
Classification

Kishinouye, 191.5a, 1923.

Nakamura, 1943, 1949.

Nichols and LaMonte, 1941.
Common names

Delsman and Hardeiiburg, 1934.

Kishinouye, 1915a, 1923.

Nakamura, 1943, 1949.

Nichols and LaMonte, 1941.
Compared with Kishinoelhi loni/gol

Serventy, 1942b.
Description

Delsman and Hardenburg, 1934.

Kishinouye, 191.->a, 1923.

Nakamura, 1949.

•Nichols and LaMonte, 1941.

Neothunnus ranis — Continued
Distribution

Delsman and Hardenburg, 1934.

Herre, 1940.

Ki.shinouye, 191.5a, 1923.

Nakamura, 1943, 1949.
Eggs

Delsman and Har<lenburg, 1934.
Figured

Kishinouye, 1915a, 1923.

Nakamura, 1949.
Food

Kishinouye, 1923.

Nakamura, 1943, 1949.
Habits

Kishinouye, 1923.

Nakamura, 1949.
Keys

Delsman and Hardenburg, 1934.

Ki.shinonye, 1915a, 1923.

Nakamura, 1949.

Nichols and LaMonte. 1941.
Migration

Nakamura, 1943.
Reproduction

Delsman and Hardenburg, 1934.

Nakamura, 1943.
Synonymy

Kishinouye, 1923.

Nakamura, 1949.

Nichols and LaMonte, 1941.
Neothunnus ranis xucalles. See KishinoeUa zacalles.
Neothunnus tonf/gol
Description

Jordan and Evermann, 1926b.
Distribution

Jordan and Evermann. 1926b.
Keys

Jordan and Evermann. 1926b.
Synonymy

Jordan and Evermann, 1926b.
Neothynniin macroptcru.i. See Neothunnus macroptcrus.
Nicotinic acid

Higashi and Hirai, 194S.
Nomenclature, tuna. See Tuna, common names.

Oceanographie conditions. See also Currents ; Salinity ;
Specific gravity : Tides ; Water.
Correlated with fishing
Ban, 1941.

Formosa Govt.-Gen. Fish. Expt. Sta., 1933a.
Hiratsuka and Imaizumi, 1934.
Hiratsuka and Ito, 19.34.
Ikehe, 1942.
Imamura, 1949.

Kanamura and Imaizumi, 1935.
Kanamura and Yazaki, 1940b.
Kawamura, 1939.

Kochi Pref. Fish. Expt, Sta., 1923a.
Nakamura, 1949.

BIBLIOGRAPHY ON PACIFIC TUNAS

47

Oeeanographic conditions — Continued
Correlated with fishing — Continued

Oita Pref. Fish. Espt. Sta., 1930.

Okuma, Imaizunil, and Malii, 1935.

Scagel, 1949.

Shapiro, liMSa.

South Seas Govt.-Gen. Fish. Expt. Sta., 1937c, 1938,
ISMlb.

Taihoku Prov. Fish. Expt. Sta., 1927a, 1927b.

Uda, 1935b, 1940c.
Correlated with location of fishing grounds

Inanami, 1942a.

Soc. Prom. Ocean. Fish., 1936.
Orcynua. See Thunnidae.
Orcynus alalonffa. See Thunnus germo.
Orcynua gernw. See Thunnus germo.
Orcynus paciflcus. See Thunnus germo.

Parasites

Bennett, 1840.
Harada, 1928.
Kishinouye, 1923.
Manter, 1940.
Van Cleave, 1940.
Parathunmis
Keys

Soldatov and Lindberg, 1930.
Pnrathunnus mebachi
Anatomy

Godsil and Byers, 1944.

Higashi, 1941c.

Kishinouye, 191.5a, 1915b, 1918, 1919a, 1922a, 1923.

Nakaniura, 1949.
Body temperature

Kanamura and Imaizumi, 1935.

Oita Pref. Fish. Expt. Sta., 1927a, 1930.
Catch per unit of effort

Imaizumi, 1937.

Japanese Bur. Fish., 1939.

Kanamura and Imaizumi, 19.35.

Kanamura and Yazaki, 1940a.

Nakamura, 1949.
Chemical analysis

Miyama and Osakabe, 1940.

Miyauchi, 1915.
Classification

Godsil and Byers, 1944.

Kishinou.ve, 191.5a, 1923.

Nakamura, 1939b, 1943, 1949.
Common names

Kishinouye, 191.5a, 1923.

Kumata et al., 1941.

Nakamura, 1939b, 1943, 1949.
Compared with Neothunnus macropterm

Roedel, 194Sb.
Compared with Thunnus germo

Roedel, l948b.
Description

Godsil and Byers, 1944.

Kishinouye, 191.5a, 1923.

Nakamura, 10.'{9b, 1949.

929179'— 51 4

Parathunnus mebachi — Continued
Distribution

Fish, 1948.

Imaizumi, 1937.

Japanese Bur. Fish., 1934.

Kanamura and Imaizumi, 1935.

Kanamura and Yaziiki, 1940a.

Kimura, 1942b.

Kishinouye, 1915a, 1923.

Kochi Pref. Fish. Expt. Sta., 1923b, 1924.

Kumata et al., 1941.

Matsubara, 1943.

Nakamura, 1939b, 1943, 1949.

Takao Prov. Fish. Expt. Sta., 1927.
Distribution correlated with water temperatures

Takayama and Ando, 1934.
Figured

Godsil and Byers, 1944.

Kishinouye, 1915a, 1923.

Kumata et al., 1941.

Nakamura, 1949.
Fishing conditions correlated with astronomical phe-
nomena

Takao Prov. Fish. Expt. Sta., 1927.
Fishing conditions correlated with oceanography

Aikawa, 1933.

Fukuda and lizuka, 1940a.

Ikebe, 1942.

Inanami, 1940b, 1940c, 1042d.

Japiinese Bur. Fish., 1934, 1939.

Kagoshima Pref. Fish. Expt. Sta., 1926b, 1927a, 1928b,
1929b, 1930b, 1930c, 19311), 1932b, 1933b.

Kanamura and Imaizumi, 1935.

Kimura, 1942a.

Mie Pref. Fish. Expt. Sta., 1930c, 1930e.

Nakamura, 1949.

Oita Pref. Fish Expt. Sta., 19,30.

Okinawa Pref. Fish. Expt. Sta., 1940b.

Omori and Fujimoto, 1940.

Omori and Fukuda, 1938, 1940.

South Seas Govt.-Gen. Fish. Expt. Sta., 1942.

Takao Prov. Fish. Expt. Sta., 1927.

Takayama and Ando, 1934.

Uehara, 1941.
Fishing conditions correlated with weather

Kanamura and Imaizumi, 1935.

Oita Pref. Fish. Expt. Sta., 1930.
Food

Kishinouye, 1917b, 1923.

Nakamura, 1943, 1949.
Habits

Kishinouye, 1923.

Nakamura, 1949.
Keys

Godsil and Byers, 1944.

Kishinouye, 1915a, 1923.

Nakamura, 1949.
Measurement data

Godsil and B.vers, 1944.

Higashi, 1940a, 1941c.

48

FISHERY BULLEmN" OF THE' FISH ANOi WILDLIFE. SERVICE

Parathunnus mebachi — Continued
Measurement data — Continued

Ikebe, 1040a.

Kanamura and Imaizumi, 1935.

Oita Pref. Fish. Expt. Sta., 1925, 1927a, 1927b, 1930.

Watanabe, H., 1940.
Meristic characters

Godsil and Byers, 1944.
Migration

Kochi Pref. Fish. Expt. Sta., 1923b, 1924.

Nakamura, 1943.
Parasites

Kishinouye, 1923.
Reproduction

Nakamura, 1943.
Sexual maturity

Kanamura and Imaizumi, 1935.
Synonymy

Kishinouye, 1923.

Nakamura, 1939b, 1949.
Young

Hatai et al., 1941.

Kishinouye, 1926.
Young as food of tunas

Kishinouye, 1917b.
Parathunnus siM
Anatomy

Su.vehiro, 1941, 1942.
Chemical analysis

Mi.vama and Osakabe, 1938.
Classification

Okada and Matsubara, 1938.
Common names

Jordan and Hubbs, 1925.

Jordan and Snyder, 1901.

Okada and Matsul>ara. 1938.

Shapiro, 194Sb.

Tinker, 1944.

TJlrey and Greeley, 1928.
Compared with Pelamys sibi

Bleeker, 1879.
Compared with Thynnus alalonga

Temminck and Schlegel, 1850.
Description

Brock, 1949.

Fowler, 1927, 1928.

Jordan and Evermann, 1926b.

Jordan and Hubbs, 1925.

Jordan and Jordan, 1922.

Okada and Matsubara, 1938.

Temminck and Schlegel, 1850.

Tinker, 1944.
Distribution

Domantay, 1940.

Fowler, 1927, 1928, 1929, 1931, 1938, 1949.

Herre, 1940.

Jordan and Evermann, 1926a, 1926b.

Jordan and Hubbs, 1925.

Jordan and Jordan, 1922.

Jordan and Snyder, 1901.

Paratlunmus sibi — Continued
Distribution — Continued

Okada and Matsubara, 1938.

Richardson, 1846.

Shapiro, 1948b.

Smith and Schaefer, 1949.

Snyder, 1904.

Tanaka, 1931.

Tinker, 1944.

Ulrey, 1929.

Ulrey and Greeley, 1928.
Distribution correlated with water temperature

Uda, 1935a.
Figured

Domantay, 1940.

Fowler, 1927, 1928.

Jordan and Evermann, 1926b.

Kitahara, 1897.

Temminck and Schlegel, 1850.

Tinker, 1944.
Pood

Suyehiro, 1942.
Habits

Brock, 1949.
Hormones

Toyama et aL, 1941.
Keys

Brock, 1949.

Jordan and Evermann, 1926b.

Okada and Matsubara, 1938.
Measurement data

Brock, 1949.

Higashi, 1942.
Synonymy

Fowler, 1928, 1949.

Jordan and Evermann, 1926b.

Jordan and Hubbs, 1925.

Richardson, 1846.

Tanaka, 1931.

Ulrey and Greeley, 1928.
Young as food of tunas

Marukawa, 1939.
Paraihynnus sibi. See Parathunnus sibi.
Pelamys afflnc. See Euthynnus alletteratus.
Pelamys macropterus. See Neothunnus macropterus.
Pelamys pelamys. See Katsuwonns pelamis.
Pelamys sibi

Compared with Thynnus sibi

Bleeker, 1879.
Pelamys thunnina. See Euthynnus alletteratus.
Plecostei
Anatomy

Berg, 1947.

Kishinouye, 1917a.

Takahashi, 1924.
Classification

Berg, 1947.

Kishinouye, 1917a.

Takahashi, 1924, 1926.

BIBLIOGRAPHY ON PACIFIC TUXAS

49

Populations
Alkawa, 1937.
Brock, 194;{.
Clark, 1929.
Goilsil, 1948. 1949.
Godsil and Byers, 1944.
Imamura, 1949.

Tauchi, 1940a, 1940b. 1940c, 1941.
Tominaga, 1943.
Uda and Tokunaga, 1937.
Uda and Tsukushi, 1934.

Reproduction
Brock, 1943.

Delsman and Hardenburg, 1934.
Eckles, 1949b.
Hatai et al., 1941.
Ikebe, 1941b.
Imamura, 1949.
Kishinouye, 191.5a, 1923.
Marr, 194S.

Nakamura. 1938, 1939b, 1943, 1949.
Schaefer, 194Sc.
Schaefer and Marr, 1948a.
Serveuty, 1941, 1942a.
Shapiro, 1948b.
Soc. Prom. Ocean. Fish., 1936.
Tinker, 1944.
Walford, 1937.
Watanabe, H.. 1939.
Whitehead, 1931.
Tabe and Mori. 1948.

Salinity. See also Oceanographic conditions.
Correlated with fishing

Inanami, 1941.

Uda and Tokunaga, 1937.
Scomber taso. See Auxis taso.
Semathunnus

Compared with yeothunnus

Fowler, 1933.

Nakamura, 1939a.
Semaihuntius guildi

Compared with Ncothunnus macropterus

Nakamura, 1939b.
Description

Fowler, 1933.
Distribution

Fowler, 1934.
Synonymy

Fowler, 1934.
Semathunnus itosibi
Common names

Tinker, 1944.
Description

Tinker, 1944.
Distribution

Fowler, 1934.

Tinker, 1944.
Synonymy

Fowler, 1934.

Sex. See Morphometries.
Sexual maturity. See Maturity.
Size composition

Aikawa, 1937.

Aikawa and Kate, 1938.

Brock, 1943.

Hart et al., 1948.

Inanami, 1942b.

Kagoshima Pref. Fish. Expt. Sta., 1937.

Kawana, 1934.

Kida, 1936.

Kimura. 1932, 1935, 1941, 1942a.

Mine and lehisa, 1940.

Nakamura Res. Staff, 1949.

Okamoto, 1940.

Sasaki, 1939a, 1939b.

Scagel, 1949.

Schaefer, 1948b.

Schaefer and Marr. 1948a.

Serventy, 1941, 1947.

Tauchi, 1940a, 1940b, 1940c.

Uda, 1935b.

Uda and Tsukushi, 1934.

Yabe and Mori, 1948.
Skipjack. See Katmiu-onus pelamis.
Skipjack, black. See Euthynnus spp.
Spawning. See Reproduction.
Specific gravity

Correlated with fishing

Formosa Govt.-Gen. Fish. Expt. Sta., 1930, 1931,

1932, 1933b, 1934.
Japanese Bur. Fish., 1939, 1940.
Mie Pref. Fish. Expt. Sta., 1930a, 1930b, 1930c, 1930d,

1930e.
Omori and Fujimoto, 1940.
Omori and Fukuda, 1938, 1940.
Shimamura, 1927.

Taihoku Prov. Fish. Expt. Sta., 1929.
Stock. See Populations.
Stomach contents. See Food.
SuiTival rates

Tauchi, 1940a, 1940b, 1940c.
Synonymy

Bleeker, 1852, 1856.

Boeseman, 1947.

Chevey, 1932a, 1934.

Chu, 1931.

Evermann and Seale, 1907.

FAO, 1949.

Fish, 1948.

Fowler, 1904b, 1928, 1931, 1934, 1938, 1944, 1949.

Fraser-Brunner, 1949, 1950.

Griffin, 1927.

Giinther, 1860, 1876.

Herre, 1936.

Hildebrand, 1946.

Jenkins, 1903.

Jordan, 1923.

Jordan and Evermann, 1896, 1905, 1926b.

Jordan and Gilbert, 1882.

50

FISHERY BUXlrErKEN OF THE FISH ANJ> WILDLIFE SERVICE

Synonymy — Continued
Jordan and Hiibbs, 1925.
Jordan and Starks, 1907.
Jordan, Tanaka, and Snyder, 1913.
Kishinouye, 1923.
Liitken, ISSO.
McCuIloch, 1922.
Meek and Hildebrand, 1923.
Nakamura, 1939a, 1939b, 1949.
Nichols and LaMonte, 1941.
Phillipps, 1927b.
PoweU, 1937.
Richardson, 1846.
Schultz, 1949.
Schultz and DeLacy, 1936.
Serventy, 1942b.
Soldatov and Lindberg, 1930.
Tanaka, 1912, 1931.
Ulrey and Greeley, 1928.
Wade, 1949.
Walte, 1907, 1921.
Weber, 1913,
Whitley, 1937.

Tagging

Anonymous, 1939.

Fukuda and lizuka, 1940b.

Godsil, 1938.

Kagoshima Pref. Fish. Expt. Sta., 1928a, 1936b, 1938b,

1939b, 1940b.
Kawana, 1934.
Matsumoto, 1937.
Seagel, 1949.

South Seas Govt.-Gen. Fish. Espt. Sta., 1941c.
Uda, 1936.
Temperature. See Body temjierature ; Water tempera-
ture ; also Oceanographic conditions.
Thunuidae
Anatomy

Kishinouye, 1917a, 1919a.
Classification

Jordan, 1923.

Kishinouye, 1917a.

Liitken, 1880.
Distribution

Bleeker, 1844.
Keys

Jordan and Hubbs, 1925.
Synonymy

Jordan, 1923.

Lutken, 1880.
Thunniformes. See Plecostei.
Thunnus alalungu. See Thunntis germo.
Thunnus albacora. See Neothunnus macropterus.
Thunnus germo
Age

Aikawa and Kato, 1938.

Brock, 1943.

Ikebe, 1940c.

Kanamura and Yazaki, 1940b.

Kimura, 1942a.

Thunnus germo — Continued
Age — Continued

Tauchi, 1940c.

Uno, 1936b.
Anatomy

Bennett, 1840.

Fish, 1948.

Godsil and Byers, 1944.

Kishinouye, 1915a, 1915b, 1919a, 1922a, 1923.

Nakamura, 1949.

Suyehiro, 1941.
Body condition

Aikawa and Kato, 1938.

Kanamura and Yazaki, 1940b.

Soc. Prom. Ocean. Fish., 1936.
Body temperature

Anonymous, 1938.

Kanamura and Yazaki, 1940b.

Oita Pref. Fish. Expt. Sta.. 1927a.

Seagel, 1949.
Catch per unit of effort

Imaizumi, 1937.

Japanese Bur. Fish., 1939, 1940.

Kanamura and Yazaki, 1940a, 1940b.

Nakamura, 1949.
Chemical analysis

Dill. 1921.

Miyauchi, 1915.

Soc. Prom. Ocean. Fish., 1936.
Classification

Fraser-Brunner, 1950.

Godsil and Byers, 1944.

Kishinouye, 1915a. 1923.

Nakamura, 1939b, 1943. 3949.

Okada and Matsubara, 1938.

Phillipps, 1927b.

Roedel, 1948b.

Shapiro, 1948a.

Soldatov and Lindberg, 1930.

Taranetz, 1937.

Walford, 1931.
Common names

Banihart, 1936.

Craig, 1929.

FAO, 1949.

Fish, 1948.

Fujita and Wakiya, 1915.

Herre and Umali, 1948.

Jordan and Evermann, 1896, 1905.

Jordan and Hubbs, 1925.

Jordan, Tanaka. and Snyder, 1913.

Kishinouye, 1915a, 1923.

Nakamura, 1939b. 1943, 1949.

Okada and Matsubara, 1938.

Phillipps, 1927b.

Roedel, 1948b.

Serventy, 1941.

Shapiro, 194Sa, 1948b.

Smith, 1947.

Starks and Jlorris, 1907.

BIBLIOGRAPHY ON PACIFIC TUNAS

51

Til II II II us germ o — Continued
Common naiups — Continued

Tinker, 1944.

Ulrey and Greeley, 1928.

Walford, 1931, 1937.
Compared with Paratlniiiiiiis mehachi

Roedel, 194Sb.
De.soription

Barnhart, 1936.

Bennett, 1840.

Boeseman, 1947.

Clemens and Wilby, 1946.

Cooper, isa'!.

Cuvier and Valenciennes, 1831.

Fowler, 1904b, 1928.

Fraser-Brunner, 19.o0.

Godsil and Byers, 1944.

Griffin, 1927.

Giinther, ISCO, 1876.

Jordan and Evermann. 1905, 1926b.

Jordan and Hubbs, 192.").

Jordan and Jordan, 1922.

Kisbinouye, 1915a, 1923.

Jleek and Hildebrand, 1923.

Nakamura, 1939b, 1949.

Oka da and Matsubara, 1938.

Roedel, 1948b.

Serventy, 1941.

Shapiro, 1948a.

Soldatov and Lindberg, 1930.

Starks, 1918.

Stead, 1906.

Tinker, 1944.

Walford, 1931, 1937.
Distribution

Anonymous. 1938.

Barnliart, 1936.

Brock, 1939.

Clemens and Wilby, 1946.

Cooper, 18a3.

Cowan, 1938.

Cuvier and Valenciennes, 1831.

Eigenmann, 1892.

Eigenmann and Eigenmann, 1891.

FAO, 1949.

Fisii, 1948.

Fowler, 1904a, 1923b, 1928, 1931, 1938, 1944.

Fraser-Brunner, 1950.

Fujita and Wakiya, 191.5.

Gilbert and Starks, 1904.

Godsil and Greenhood, 1948.

Griffin, 1927.

Giinther, 1860, 1876.

Herre, 1940.

Hildebrand, 1946.

Holder, 1912.

Hubbs, 1928.

Imaizuuii, 1937.

Japanese Bur. Fish., 1939, 1940.

Jordan, 1885.
320179°— 51 5

Thunnus germo — Continued
Distribution — Continued

Jordan and Evermann, 1896, 1905, 1926a, 1926b.

Jordan and Gilbert, 1881a, 1882.

Jordan and Hubbs, 1925.

Jordan and Jordan, 1922.

Jordan and Seale, 1906.

Jordan, Tanaka, and Snyder, 1913.

Kanamura and Yazaki, 194()b.

Klmura, 1942b.

Kishinouye, 1915a, 1923.

Koehi Pref. Fish. Expt. Sta., 1923b, 1924.

Matsubara, 1943.

McCuUoch, 1922.

Meek and Hildebrand, 1923.

Metz, 1912.

Nakamura, 19.39b, 1943, 1949.

Okada and Matsubara, 1938.

Phillipps, 1927a, 1927b.

Phillipps and Hodgkinson, 1922.

Roedel, 1948b.

Roughly, 1916.

Sampson, 1940.

Sehaefer, 1948c.

Schultz and DeLacy, 1936.

Serventy, 1941, 1947.

Shapiro, 1948a, 194Sb.

Soldatov and Lindberg, 1930.

Starks, 1918.

Starks and Morris, 1907.

Stead, 1906, 1908.

Tanaka, 1931.

Taranetz, 1937.

Thompson and Higgins, 1919.

Tinker, 1944.

Ulrey, 1929.

Ulrey and Greeley, 1928.

Walford, 1931, 1937.

Whitehead, 1929.
Distribution correlated with water temperature

Takayama and Ando, 1934.

Uda, 1935a.
Eggs

Watanabe, H., 1939.
Enemies

Bennett, 1840.
Exploitation rates

Tauchi, 1940c.
Figured

Anonymous, 1938.

Barnhart, 19.36.

Clemens and Wilhy, 1946.

Cooper, 1S&3.

Fowler, 1904a.

Fraser-Brunner, 19.50.

Godsil and Byers, 1944.

Griffin, 1927.

Giinther, 1876.

Holder, 1912.

Jordan and Evermann, 1905, 1920b.

52

FISHE'RY BULLEITIN OiF THE* FISH AA^D WILDLIFE SERMCE

Thunnus germo — Oonlinued
FiKui-fd — Continned

Kishinouye, 1915a, 1923.

Kitahara, 1897.

Nakamura, 1949.

IJoedel, 194Sb.

Serventy, 1941.

Shapiro, 1948a.

Tinker, 1944.

Walford, 1931, 1937.
Fisiiing conditions correlated witli area

Hart and Hollister, 1947.

Hart et al., 1948.
Fisiiing conditions correlated with oceanography

Aikawa, 1933.

Chiba Pref. Fish. Expt. Sta., Katsuura Br., 1936, 1941.

Hart and Hollister, 1947.

Hart et al., 1948.

Inanaml, 1942d.

Japanese Bur. Fish., 1939, 1940.

Kagoshima Pref. Fish. E.xpt. .Sta., 1927a, 1928b, 1930b,
1930c, 1931b, 19.32b, 1932c, l!l33b.

Kanamnra and Yazaki, 1940b.

Ximura, 1942a, 1949.

Mie Pref. l^sh. Expt. Sta., 1930c, 1930e.

Nakamura, 1949.

Sasaki, 1939b.

Scagel, 1949.

Shapiro, 1948a.

Takayama and Ando, 19.34.

Uda, 1940c.

Uda and Tokunaga, 1937.
Fishing conditions correlated wilh season

Hart et al., 1948.
Fishing grounds correlated with oceanography

Soc. Prom. Ocean. Fish., 1936.
Food

Anonymous, 1938.

Asano, 1939.

Bennett, 1840.

Clemens and Wilby, 1946.

Hart and Holli-stor, 1947.

Hart et al., 1948.

Japanese Bur. Fish., 1939, 1940.

Jordan and Gilbert, 18811), 1882.

Kanamura and Yazaki, 1940b.

Kishinouye, 1917b, 1923.

Kuronuma, 1940.

Nakamura, 1943, 1949.

Scagel, 1949.

Shapiro, 1948a.

Starks, 1918.

Starks and Morris, 1907.

Walford, 1937.

Watanabe, H., 1939.
Growth

Aikawa and Kato, 1938.

Brock, 1943.

Kishinouye, 1923.

Thunnus germo — Continued
Habits

Jordan and Gilbert, 1882.

Kishinouye, 1923.

Nakamura, 1949.

Shapiro, 1948a.
Hormones

Toyama et al., 1941.
Keys

Brock, 1949.

Fraser-Brunner, 1950.

Godsil and Byers, 1944.

Hildebrand, 194C.

Jordan and Evermann. 1926b.

Kishinouye, 191."ia, 1023.

McCuUoch, 1922.

Meek and Hildebrand, 1923.

Nakamura, 1949.

Okada and Matsubara, 1938.

Roedel, 194Sb.

Serventy, 1941.

Soldatov and Lindberg, 1930.

Taranetz, 1937.

Walford, 1931, 1937.
Measurement data

Aikawa and Kato, 1938.

Anonymous, 1938.

Brock, 1943.

Godsil, 1948.

Godsil and Byers, 194^.

Ikebe, 1940c.

Japanese Bur. Fish., 1939, 1940.

Kanamura and Yazaki, 1940b.

Oita Pref. Fish. Expt. Sta., 1925, 1927a.

South Seas Govt.- Gen. Fish. Expt. Sta., 1943a.

Uno, 193Cb.

Watanabe, H. 1939.
Meristie characters

Clark, 1929.

Godsil and Byers, 1944.
Migration

Cobb, 1919.

Kimura, 1942b.

Kisliinouye, 1923.

Koclii Pref. Fish. Expt. Sta., 1923b, 1924.

Nakamura, 1943, 1949.

Sasaki, 1939b.

Shapiro, 1948a.

Soc. Prom. Ocean. Fish., 1936.

Walford, 1937.
Populations

Brock, 1943.

Clark, 1929.

Godsil, 194S, 1949.

Godsil and Byers. 1944.

Tauehi, 1940c.

Uda and Tokunaga, 1937.
Reproduction

Brock, 1943.

Nakamura, 1943.

BIBLIOGRAPHY ON PACIFIC TUNAS

53

Th II II II IIS i/crmo — Continued
Reproduction — Continued

Sehaefer, 1948c.

Soc. Prom. Ocean. Fi.sl'., 1936.

Wiilford, 19.37.

WjitanMlic, H., 1939.
Sex ratio

Brook, km:;.

Sexual maturity

Anonymous, 193S.

Clark, 1929.

Kanamura and Yaznki. 1940b.

Soc. Prom. Ocean. Fish.. 1936.

Wataiuibe, H., 19.39.
Size composition

Aikawa and Kato, 1938.

Brock, 1943.

Hart et al., 1948.

Kimura, 1942a.

Sasaki, 19391x

Scagel, 1949.

Tauchi, 1940c.
Survival rates

Tauclii, 1940c.
Synonymy

Boeseman, 1947.

FAO, 1949.

Fish, 1948.

Fowler, 1904b, 1928.

Fraser-Brunner, 1950.

Griffin, 1927.

Giinther, 18G0, 1876.

.Jordan and Evermann, 1896, 1905, 1926b.

Jordan and Gilbert, 1882.

Jordan and Hubbs, 1925.

Jordan, Tanaka, and Snyder, 1913.

Kishinouye, 1923.

MrCulloch, 1922.

Meek and Hildebrand, 1923.

Nakamura, 1939b, 1949.

Phillipps, 1927b.

Schultz and DeLaey. 1936.

Soldatov and Lindberg, 1930.

Tanaka, 1931.

Ulrey and Greeley, 1928.
Tagging

Seagal, 1949.
Young

Kishinou.ve, 1917b, 1919b, 1923.

Liitken, 1880.

Schaefer, 1948c.
Th II II 11 IIS ninccori. See Tliiiiiiiiis iiinccoyi.
'riiiiiiiiiiK iiiacroyi
Catch per unit of effort

Serventy, 1947.
Classification

Itnughly, 1916.
Common names

Serventy, 1941.

Whitley, 1947.

Tliiiiuiiis mucroiji — Continued
Compared with Kiskinoella tonggol

Serventy, 1941.
Description

Castelnau, 1872.

Jordan and Evermann, 1926b.

Macleay, ISSl.

Roughly, 1916.

Serventy, 1941.

Stead, 1908.
Distribution

Jordan and Evermann, 1926b.

Lord, 1927.

Macleay, 1881.

McCulloch, 1922.

Roughly, 1916.

Serventy, 1941, 1947.

Stead, 1908.

Waite, 1928.

Whitley, 1947.
Figured

McCulloch, 1922.

Roughly, 1916.

Serventy, 1941.
Habits

Roughly, 1916.
Keys

Jordan and Everniaiui, 1926b.

McCulloch, 1922.

Serventy, 1941.
Length-weight relation

Serventy, 1941.
Migration

Serventy, 1941.
Reproduction

Serventy, 1941.
Size composition

Serventy, 1941. 1947.
Synonymy

Joi'dan and Evermann, 192Gb.

McCulloch, 1922.
Thiiiiniis ma<-r<ipicnis. See Neothuiiniis macropterus.
Thunniis maciilatus
Distribution

Holder, 1912.
Figured

Holder, 1912.
Thiuiiiiis mebdclii. See I'lirathiiiinus tnebachi.
Thunnus nicolsmii
Compared with KishiiiinJUi loiir/r/ol

Serventy, 1942b.
Til II II II 11.1 ohesus. See also Ptiiulliiiunus iiiehachi and I'ara-

thininus sibi.
Clas.sification

Fraser-Brunner, 19.50.
Doiscription

Fraser-I'.runner, 1950.
Distribution

Fraser-Brunner, 1950.

54

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

ThmDiiis obesiis — Continued
Figured

Fraser-Brunner, 1950.
Keys

Fraser-Brunner, 1950.
Synonymy

Fraser-Brunner, 1950.
Thunints orientalis
Age

Aikawa and Kato, 1938.
Kiraura, 1935.
Tauchi, 1940a.
Anatomy

Kishinouye, 1915a, 191!jb, 1919a, 1921, 1022a, 1923.
Migita and Arakawa, 1948.
Nakamura, 1938, 1949.
Suyeliiro, 1942.
Body condition

Aikawa and Kato, 1938.
Body temperature

Olta Pref. Fisli. Expt. Sta., 1927a, 1930.
Chemical analysis

Miyama and Osakabe, 1938, 1940.
Miyauchi, 1915.
Shimizu, 1947.
Classification

Kisliinouye, 1915a, 1923.
Nakamura, 1939b, 1043. 1949.
Okada and Matsubara, 1938.
Shapiro, 1948a.
Common names

Fu.iita and Wakiya, 1915.
.Jordan and Hubbs, 1025.
Jordan and Snyder, 1001.
Kishinouye, 1915a, 1023.
Nakamura, 1939b, 1043. 1949.
Okada and Matsubara, 1938.
Shapiro, 1048a, 1948b.
Tinker, 1944.
Compared with Thunnns thynnus
Kisliinouye, 1021.
Soc. Prom. Ocean. Fish., 1936.
Tinker, 1944.
Description
Boeseman, 10

Jordan and Evermann, 1926b.
Jordan and Hubbs, 1025.
Jordan and Jordan, 1922.
Kishinouye, 1015a, 1923.
Nakamura, 1930b, 1949.
Okada and Matsubara, 1938.
Shapiro, 104Sa.
Temminck and Schlegel, 1850.
Tinker, 1044.
Distribution
Fowler, 1034.
Fujita and Wakiya, 1015.
Jordan and Evermann, 1026a, 1926b.
Jordan and Hubbs. 1925.
Jordan and Jordan, 1922.

Th u n n us or en talis — Continued
Distribution — Continued

Jordan and Snyder, 1000, 1001.
Kimura, 1042h.
Kishinouye, 1915a, 1023.
Kochi Pref. Fish. Expt. Sta.. 1024.
Mat.subara, 1943.
Mori, 1928.

Nakamura, 1038, 1930h, 1943, 1949.
Okada and Matsubara, 1038.
Reeves, 1928.
Richardson, 1846.
Shapiro, 1948a, 1048b.
Tinker, 1944.
DistriI)ution correlated with water temperature

Takayama and Ando, 1034.
Eggs

Hatai et al., 1041.
Nakamura, 1938, 1949.
Enemies

Kishinouye, 1928.
Exploitation rates

Tauchi, 1940a.
Figured
Kishinouye, 1915a, 1923,
Naliamura, 1939b, 1040.
Otaki, Fujita, and Higurashi, 1003.
Shapiro, 1948a.
Tinker, 1044.
Fishing conditions correlated with astronomical
phenomena
Kawana, 1034.
Fishing conditions correlated with oceanography
Aikawa, 1033.
Fukuda and lizuka, 1040a.
lehisa, 1030.

Kagoshima Pref. Fish. Expt. Sta., 1927a, 1930c, 1932b.
Kawana, 1934, 1037.
Mie I'ref. Fish. Expt. Sta., 1930c, lO.SOe.
Oita Pref. Fish. Expt. Sta., 1030.
Okinawa Pref. Fish. Expt. Sta., 1940b.
Omorl and Fujimoto, 1940.
Omori and Fukuda, 1938, 1940.
Shapiro, 104Sa.
Takayama and Ando, 1934.
Uda, 1940c.
Fishing conditions correlated with weather

Oita Pref. Fish. Expt Sta., 1930.
Food

Kishinouye, 1023.
Nakamura, 1043, 1949.
Shapiro, 104Sa.
Suyehiro, 1042.
Growth

Aikawa and Kato, 1938.
Kimura, 1932. ^

Kishinouye, 1923.
Habits

Kishinouye, 1923.
Nakamura, 1049.
Shapiro, 194Sa.

BIBLIOGRAPHY ON PACIFIC TUNAS

55

Thunniis orentalis — Continued
Hormones

Migita and Arakawa. 1948.

iirock, 1949.

.Ionian and Evermann. 1926b.

Kishinouyp, lltl.-)a. 1923.

Nakamura, 1!)49.

Okada and Matsubara, 1938.
Me.-isiirement data

Aikawa and Kato, 1938.

Higashi, 1040a.

nita Pref. Fish. Expt. Sta., 1927a, 19,30.
Migration

Kimura, 1942b.

Kishinoiiye, 1923.

Kochi Pref. Fisli. Expt. Sta., 1924.

Nakamura, 1943, 1949.

Shapiro, 1948a.
Populations

Tauchi, 1940a.
Reproduction

Hatai et al., 1941.

Kishinouye, 191.5a, 1923.

Nakamura, 1938, 1939b, 1943, 1949.

Soc. Prom. Ocean. Fish., 1936.
Sexual maturity

Hatai et al., 1941.

Nakamura, 19.38.
Size composition

Aikawa and Kato. 1938.

Kawana, 1934.

Kimura, 1932, 193.5.

Jline and lehisa, 1940.

Tauchi, 1940a.
Survival rates

Tauchi, 1940a.
Synonymy

P>oeseman, 1947.

Fowler, 1934.

Jordan and Evermann, 1926b.

Jordan and Hubbs, 1925.

Kishinouye, 1923.

Nakamura, 1939b, 1949.

Richard.«on, 1846.
Tagging

Kawana, 1934.
Young

Kishinouye, 1919b, 1923.
TlniiDuis phillippsi
Classification

Phillipps. 1927b.
Common names

Phillipps, in27b.
Description

Jordan and Evermann. 1926b.
Distribution

Jordan and Evermann, 1026b.

Phillipps, 1927b.
Figured

Jordan and Evermann, 1926b.

ThunnuH orentalis — Continued
Keys

Jordan and Evermann, 1926b.
Synonymy

Phillipps, 1927b.
Tliinnnis pltiltipHi. See Thunnvs phillippsi.
Thiititius rants. See Neothunnus rarus.
Thinirius siilirns
Common names

Craig, 1929.
Description

Jordan and Evermann, 102Gb.
Dlstriliution

Jordan and Evermann, 1026b.

Ulrey, 1020.
Figured

Jordan and Evermann, 1026b.
Keys

Jordan and Evermann, 1926b.
Thunnus schlegeli. See Thunnus orirntalis.
Thtinrnis tkunninn. See Euthynnus allHteratus.
Thunnus thunnus. See Thunnus thynnus.
Thunnus thynnus
Anatomy

Fish, 1948.

Godsil and Byers, 1944.

Kishinouye, 1921.
Catch -per unit of effort

Whitehead, 1931.
Chemical analysis

Dill, 1921.
Classification

Fraser-Brunner, 1950.

Godsil and Byers. 1944.

Roedel, 194Sb.

Soldatov and Lindberg, 1930.

Taranetz, 1937.

Walford, 1931.

Whitehead, 1931.
Common names

Barnhart, 1936.

FAO, 1949.

Fl.sh, 1948.

Jordan and Evermann, 1896.

Jordan, Tanaka, and Snyder, 1913.

Roedel, 194Sb.

Schultz, 1949.

Starks and Morris, 1907.

Tinker, 1944.

Ulrey and Greeley, 1928.

Walford, 1931, 1937.
Compared with Xrothunnus macropterus

Thompson and Higgins, 1919.
O^unpared with Thunnus orientalis

Bashinouye, 1021.

Soc. Prom. Ocean. Fish., 1936.

Tinker, 1944.
Description

Barnhart. 1036.

Fowler, 1028, 1944.

Fraser-Brunner, 1950.

56

FISHERY BULLEimsr OF THE FISH ANjy WILDLIFE SER\^OE

Thunnus thynnus — Continued
Description — Continued

Godsil and Byers, 1944.

Giinther, 1876.

Jleek and Hildebrand, 1923.

Roedel, 194Sb.

Soldatov and Lindberg, 1930.

Stark.s, 191S.

Stead, 1906.

Tinker, 1944.

Walford, 1931, 1937.
Distribution

Abe, 1939.

Barnhart, 1936.

Brock, 193S.

FAO, 1949.

Fish, 1948.

Fowler, 1923a, 1923b, 1928, 1929, 1931, 1934, 1938,
1944.

Fraser-I'runner, 19.50.

Gilbert and Starks, 1904.

Giinther, 1876.

Herre, 1936, 1940.

Hildebrand, 1946.

Holder, 1912.

Jordan and Evermann, 1896.

Jordan and Jordan, 1922.

Jordan, Tanaka, and Sn.vder, 1913.

Meek and Hildebrand, 1923.

Metz, 1912.

Roedel, 1948b.

Schultz, 1949.

Schultz and DeLacey, 1936.

Soldatov, 1929.

Soldatov and Lindberg, 1930.

Starks, 1918.

Starks and Morris, 1907.

Stead, 1906.

Tanaka, 1931.

Taranetz, 1937.

Tinker, 1944.

Ulrey, 1929.

Ulrey and Greeley, 1928.

Waite, 1921.

Walford, 1931, 1937.

Whitehead, 1929, 1931.
Distribution correlated with water temperature

Uda, 1935a.
Enemies

Tinker, 1944.

Walford, 1937.
Figured

Barnhart, 1936.

Fraser-Brunner, 1950.

Godsil and Byers, 1944.

Holder, 1912.

Kitahara, 1897.

Roedel, 1948b.

Soldatov and Lindberg, 1930.

Starks, 1918.

Tinker, 1944.

Th iiiDiiis thynnus — Continued
Figured — Con t i nued

Walford, 1931, 1937.

Whitehead, 1931.
Fishing conditions correlated with oceanography

Kida, 1936.
Food

Tinker, 1944.

Walford, 1937.
Habits

Kida, 1936.

Uchida, 1923.
Keys

Brock, 1949.

Fraser-Brunner, 1950.

Godsil and Byers, 1944.

Hildebrand, 1946.

Meek and Hildebrand, 1923.

Roedel, 194Sb.

Soldatov and Lindberg, 1930.

Taranetz, 1937.

Walford, 1931, 1937.
Measurement data

Godsil and Byers, 1944.

Uda, 1932.
Meristic characters

Godsil and Byers, 1944.
Migration

Wliitehead, 1931.
Populations

Godsil and Byers, 1944.
Reproduction

Tinker, 1944.

Walford, 1937.

Whitehead, 1931.
Size composition

Kida, 1936.
Synonymy

FAO, 1949.

Fish, 1948.

Fowler, 1928, 1934, 1944.

Fraser-Brunner, 1950.

Giinther, 1876.

Herre, 1936.

Jordan and Evermann, 1896.

Jordan, Tanaka, and Snyder, 1913.

Meek and Hildebrand, 1923.

Sclniltz, 1949.

Schultz and, DeLacy, 1036.

Soldatov and Lindberg, 1930.

Tanaka, 1931.

Ulrey and Greeley, 1928.

Waite, 1921.
Thunnus tonf/ffol
Classitication

Fraser-Brunner, 1950.
Compared with Kishinoclla tonggol

Serventy, 1942b.
Description

Bleeker, 1852.

BIBLIOGRAPITi' ON PACIFIC TUNAS

57

Thiinniis ionggol — Continued
Description — Continued
Fraser-Brunner, lOriO.
Giinther, ISGO.
Distribution

Bleeker, 1852. lS61b.
Fraser-Brunner, 1950.
Gunther, 1S60.
Figured

Fraser-Brunner, 1950.
Serventy, 10-42b.
Keys

Fraser-Brunner, 1950.
Synonymy
Bleeker, 1852.
Fraser-Brunner, 1950.
Giinther, 1860.
Thiiiiniin zacnllex. See KishiiioeUa xticalles.
'I'hiDinus. See Thiiiinidiie.
Tliiniiiiis afpnis. See EiithiitniKs allcttcrntiis.
Thiinnus alaloiiyn. See also Tliiinnux girmo.
Compared with TliininuK sihi
Temminck and Soldegel, IS.jO.
Thtjrmus gcrmo. See Thunnus germo.
Thynmis mnccoyi. See Thunnus marroyi.
Thynnus macropterus. See Neotlnnntux mncropierus.
'I'hynnus oricnialis. See Thunnus orienfulis.
Tliyiuius pacificus. See Thunnus gcrmo.
Thynnus pelamys. See Knisuiconus pclnmis.
Thynnus silii. See Pamthunnus sihi; also Thunnus

gcrmo.
Thynnus thunina. See Euthynnus allettcratus.
Thynnus thiinnina. See Euthynnus allettcratus.
Thynnus thynnus. See Thunnus thynnus.
Tliynnus tonggol. See Thunnus toni/gol.
Tides. See also Oeeanographic conditions.
Correlated with fishing
Takao Prov. Fish. Expt. Sta., 1927.
Transparency, water. See Water transparency ; also

Oeeanographic conditions.
Tuna

Bibliography

Corwin, 19.30.
Chemical analysis
Kodama, lizuka, and Harada, 1934.
Tomiyama, 19.3.3.
Common names
Australian

Serventy, 1941.
Wliitley, 1947.
Kngllsh

Barnhart, 1936.

Craig, 1929.

Fish, 1948.

Herre and Uniali, 1948.

Jordan and Evermann, 1896.

Kumata et al., 1941.

Nichols and I.aMonte, 1941.

Roedel, 194Sb.

Schultz, 1949.

Starks and .Morris. 1907.

Tuna — Continued

Couunoii nanie.s — Continued
English— Continued

Tanaka, 1912.

Tinker, 1944.

Ulrey and Greeley, 1928.

Walford, 1931, 1937.
European

Kumata et al., 1941.

Tinker, 1944.
Hawaiian

Jordan and Kvermann, 1905.

Jordan ami .Jordan, 1922.

Smith, 1!)47.

Tinker, 1944.
Indo-Chinese

Chevey, 1932a.
Japanese

Fish, 1948.

Fujita and Wakiya, 1915.

Jordan and Evermann, 1926b.

Jordan and Hubbs, 1925.

Jordan and Jletz, 1913.

Jordan and Snyder, 1901.

Jordan, Tanaka, and Snyder, 1913.

Kishiiiouye, 191."a, 1923.

Kumiita et al.. 1941.

Nakamura. 19.391). 1943, 1949.

Okad.i and Matsubara, 1938.

Shapiro, 194Sa.

Tanaka, 1912.

Tinker, 1944.

Tomiaaga. 1943.
Malayan

Delsniau and Ilardenbur^, 1934.

Kumata et al., 1941.
Maori

Phillipps, 1927b.
Mieronesian

Smith, 1947.
New Zealand

PhilUpps, 1927b.
Peruvian

Nichols and Murphy, 1922.
Philippine

Herre and Umali. 1948.
Ryukyuan

Shapiro, 1948b.
Venezuelan

Schultz, 1949.
Worldwide

FAO, 1949.
Distribution

Hasegawa, 19.37.

South Seas Govt.-Gen. Fish. Expt. Sta., 1937b, 1941a.
Food

Kishinouye, 1895, 1915a.
Habits

Kishinouye, 191.'5a.
Measurement data
Kodama, lizuka, and Harada. 19.34.

58

FISHERY BULLETIN OF THE FISH AJXD WILDLIFE SERVICE

Winidcrer wallisi
Classification

Whitley, 1937.
Compared with Euthynnus allittcratus

Whitley, 1937.
Compared with Eutliynnus yaito

Whitley, 1937.
Description

Whitley, 1937.
Food

Whitley, 1937.
Synonymy
Whitley, 1937.
Water. See also Oceanosraphlc conditions.
Color correlated with fishing
luanami, 1940c.

Taihoku Prov. Fish. Expt. Sta., 1929, 1932.
Temperature

Correlated with body temperature
Nakamura, 1941.

Oita Pref. Fish. Expt. Sta., 1927a, 1930.
Correlated with distribution
Takayama and Ando, 1934.
Takayama, Ikeda, and Ando, 19.34.
Correlated with fishing conditions
Aikawa, 1933.
Chiba Pref. Fish. Expt. Sta., Katsuura Br., 1936,

1937, 193S, 1941.
Formosa Govt.-Gen. Fish. Expt. Sta., 1930, 1931,

1932, 1933b, 1934.
Fukuda and lizuka, 1940a.
Hart and HoUister, 1947.
Hart et al., 1948.
lehisa, 1939.
Inanami, 1941, 1942d.
Japanese Bur. Fish., 1934, 1939, 1940.
Kagoshima Pi-ef. Fish. Expt. Sta., 1925, 1926a,
1926b, 1927a, 1927b, 192Sa, 192Sb, 1929a, 1929b,
1930a, 1930b, 1930c, 1931a, 1931b, 1932a, 1932b,
1932c, 1933a, 1933b, 1935, 1936a, 1937.
Kanamura aud Yazaki, 1940a.
Kawana, 1937.
Kida, 1936.

Kimura, 1941. 1942a, 1949.
Kimura and Ishii, 1933.
Kumamoto Pref. Fish. Expt. Sta., 1946.
Mie Pref. Fish. Expt. Sta., 1930a, 1930b, 1930c,

1930d, 1930e.
Okinawa Pref. Fish. Expt. Sta., 1940a, 1940b, 1943.
Omori and Fujimoto, 1940.
Omori and Fukuda, 1938, 1940.
Sasaki, 1939a, 1039b.

Shizuoka Pref. l"ish. Expt. Sta., 1936, 1937.
South Seas Govt.-Gen. Fish. Expt. Sta., 1942, 1943b.
Taihoku Pi-ov. Fish. Expt. Sta., 1929, 1932.
Takayama and Ando, 1934.
Takayama, Ikeila, and Ando, 1934.
Uda, 1935a, 1935h, 1936, 1938, 1939, 1940b, 1940c.
Uda and Tokunaga, 1937.

Water — Continued

Temperature — Continued

Correlated with fishing conditions — Continued
Uehara, 1941.
Yabe and Mori, 1948.
Transparency correlated with fishing

Inanami, 1942a.

Japanese Bur. Fish., 1934.
Weather

Correlated with fishing

Formosa Govt.-Gen. Fish. Expt. Sta., 1933a.

Hiratsuka and Imaizumi, 1934.

Hiratsuka and Ito, 1934.

lehisa, 19.39.

Kanamura and Imaizumi, 1935.

Oita Pref. Fish. Expt. Sta., 1930.

Okinawa Pref. Fish. ExiJt. Sta., 1940a, 1943.

Okunia, Imaizumi, and Maki, 1935.

Taihoku Prov. Fish. E.xpt. Sta., 1927a, 1927b.

Uda and Watauabe, 1938.

Yellow-finned tuna. See Neothunnus macropterus.
Young

As food of tunas

Eckles, 1949b.

Kishinouye, 1917b.

Marukawa, 1939.
Description

Delsman, 1931.

Delsman and Hardenburg, 1934.

Eckles, 1949b.

Giinther, 1889.

Kagoshima Pref. Fish. Expt. Sta., 1926a, 1927b.

Kishinouye, 1919b, 1923, 1924, 1926.

Liitken, 1880.

Marr, 1948.

Schaefer and Marr, 194Sa, 1948b.

Wade, 1949.
Figured

Eckles, 1949b.

Giinther, 1889.

Kishinouye, 19191i, 1923, 1926.

Liitken, 1880.

Schaefer and Marr, 1948a, 194Sb.

Wade, 1949.
Records of capture

Delsman, 1931.

Delsman and Hardenburg, 1934.

Eckles, 1949b.

Giinther, 1889.

Hatai et al., 1941.

Inanami, 1942c.

Kagoshima Pref. Fish. Expt. Sta.. 1926a, 1927b.

Kishinouye, 1919b, 1923, 1924, 1926.

Liitken, 1880.

Marr, 1948.

Schaefer, 1948c.

Schaefer and Marr, 1948a, 1948b.

Wade, 1949.

Yabe and Mori, 1948.

O

UNITED STATES DEPARTMENT OF THE INTERIOR, Oscar L. Chapman, Secretary
FISH AND WILDLIFE SERVICE, Albert M. Day, Director

BREEDING HABITS OF LAKE TROUT

IN NEW YORK

By William F. Royce

FISHERY BULLETIN 59

From Fishery Bulletin of the Fish and Wildlife Service

VOLUME 52

JNITED STATES GOVERNMENT PRINTING OFFICE • WASHINGTON 1951

?or sale by the Superintendent of Documents, V. S. Government Printing Office, Washington 25, D. C.- Price 20 cents

CONTENTS

Page

Sexual dimorphism 59

Spawning habits 61

Age and size at maturity 61

Time of spawning 62

Duration of spawning period 65

Place of spawning 66

Spawning act 68

Environment and development of eggs and larvae 70

Efficiency of fertilization 70

Temperature requirements 71

Effects of predation 71

Development of eggs and alevins 72

Juvenile lake trout of Keuka I^ake 73

Summary 74

Acknowledgments 75

Literature cited 75

BREEDING HABITS OF LAKE TROUT IN NEW YORK

By William F. Royce, Fishery Research Biologist

The several races of lake trout (Salcelinus
[ = Cristii'omer] namaycush) are widely sought in
all the more accessible parts of their range. In
tlie Great Lakes, where this species is one of the
most valued food fishes, it is the object of a major
fishery. In smaller lakes of the northeastern
I'nited States and southern Canada, where com-
mercial fishing usually is prohibited, it is sought
as a game fish.

This popularity has been accompanied by
severe declines in the populations of lake trout in
some lakes, notably the Great Lakes. Detailed
knowledge of the species, particularly of the eggs,
larvae, and juveniles below the sizes commonly
caught, is needed for devising measures to prevent
such declines, and for successfully introducing
this desirable species in additional lakes.

Almost nothing is known of the habits of young
lake trout, probably because of their deep-water
habitat ; in fact, very few wild lake trout less than
8 inches long have even been seen. The re-
productive habits of the species have been im-
perfectly known, and very little has been published
on size and age at maturity. Accordingly, a
study of the breeding habits of this species and
the life history of its young was made in 1939,
1940, and 1941, on several lakes in the State of
New York.

SEXUAL DIMORPHISM

The lake trout, unique among the salmon family,
lacks almost completely the malformed jaws or
kype common to mature males of other species.
Examination of several hundred lake trout from
various lakes in New York State showed that it is
almost impossible to distinguish the sex of mature
lake trout by examination of the head alone. The
males have only a slight tendency toward a more
j pointed snout — although J. R. Westman reported
in a personal communication that he had seen a verv

Note.— This paper is a revision of a thesis that was submitted to Cornell
I'niversity in 1943 in partial fulfillment of the requirements for the depree
of doctor of philosophy.

large male lake trout from Lake Simcoe, Ontario,
with a well-developed kype.

It is pertinent to compare the jaws of the lake
trout with those of the Pacific salmon, in which
the kype attains its maximum development.
The Pacific salmon migrate enormous distances
to the spawning ground and live entirely on stored
food for almost a year before spawning. Mottley
(1936) ' suggests that the development of the kype
in the male may occur because its demand on the
material mobilized for the development of the
gonads differs from that of the female. He
postulates that the ovaries would have a general
requirement for stored materials, while the testes
would require little albuminoid or fat. Thus,
these materials might be utilized in the growth of
the kype instead of being excreted.

The lake trout would appear to be a diametric
opposite. It rarely has a kype, migrates only the
short distance from the deep to the shoal waters
of a lake, and feeds up to and through the spawning
period.- Inasmuch as the lake trout does not ac-
quire a kype and as the maturation of the gonads
parallels that of the salmon, Mottley's suggestion
leaves some things to be explained. Possibly,
since the lake trout feeds right up to and through
the spawning season, the gonads can develop from
ingested food instead of mobilizing stored material
from the body.

Alike in external structure, male and female
lake trout are also very similar in color when
removed from the water. However, in New York
State, the normal coloration of both sexes varies
widely from lake to lake. The lake trout of the
large, clear Finger Lakes are light olivaceous,
almost silvery on the back and sides, with a little
yellow or orange in the fins. There are all grada-
tions between the color of these trout and the very
dark trout of the brown-water Adirondack lakes.

I Publications referred to parenthetically by dale are listed in Literature
Cited, p. 75

' Rayner (194 1) found that stomachs of ripe lake trout taken on the spawn-
ing area contained fish, lake-trout eftRS, and miscellaneous invertebrates.

59

60

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Figure 1. — Male lake trovit on the spawning grounds in Otsego Lake, N. Y.

LAKE TROUT BREEDING HABITS

61

The latter have stronger colors, and the sexual
differences are a little more pronounced; the males
tend to have more brilliant yellow, orange, and
black in the paired fins than the females. But
even in these lake trout it is not always possible
to distinguish the sexes on the basis of external
differences.

This normal coloration is considerably changed
when the male lake trout are excited on the spawn-
ing area. While they are courting, the chromato-
phores on their backs contract, making the backs
appear decidedly light colored, while the sides,
flooded with pigment, become very lustrous and
almost black (fig. 1). Merriman (1935) observed
this condition in the lake trout of Squani Lake, N . H. ,
and it was seen by the writer in Otsego Lake,
N. Y., in 1940 and 1941, when selected fish were
speared and the brilliant coloration was found to
be restricted to the males. Striking as this colora-
tion was during the courting or spawning, the colors
were most ephemeral. After the fish were netted
or speared, color differences between the sexes
could not be detected.

SPAWNING HABITS
AGE AND SIZE AT MATURITY

The age analysis, by means of scales, of 33
mature lake trout caught by gill net on the spawn-
ing area oft' Peach Orchard Point in Seneca Lake,
N. Y., showed that 13 had 5 annuli and the remain-
ing 20 had 6 annuli. Comparison of the lengths
of the lake trout in this sample with the length
frequency of 424 lake trout taken during the
spawning season in 1941 showed that these age
groups comprised tlie bulk of the catch, but
probably an appreciable quantity of older fish
wiere taken.

Data collected during 1940 by J. R. Westman
on the lake trout of Lake Simcoe, Ontario, showed
that 13 out of 20 five-year-old and 16 out of 17
six-year-old lake trout were mature. Samples from
Keuka Lake, N. Y., in the same year showed
similar results: 15 out of 18 five-year-old and 5 out
of 6 six-year-old trout were mature. There was
a shght tendency for the greater proportion of
the young males to be mature in these two lakes,
as well as in Seneca Lake.

Fry and Kennedy (1937) estimated, by means
of the modes of a length frequency distribution,
that the lake trout of Lake Opeongo, Algonquin
Park, Canada, reached the minimum age at

maturity in their fifth year of life (corresponding,
presumably, to four annuli). Inasmuch as they
had only five lake trout less than 13 inches long,
and as my observations indicate very small
growth of lake trout in the first year, I believe
that they assigned to each mode an age 1 year
less than it should have been.

These data are substantiated by studies made
on the growth of hatchery-reared trout. Surbcr
(1933) secured eggs from female lake trout, aged
4 years 6 months, whose lengths varied from 18
to 26 inches; but at this time only 10 females
out of somewhat less than 2,000 males and females
spawned, producing an average of only 962 eggs
per female. No data on subsequent spawning
were presented, but certainly the majority of these
fish did not spawn before their sixth year. Surber
considered that this age at maturity was com-
parable to that attained by wild fish. He gave
the length of the trout at the end of their first,
second, third, and fourth years of life as 10, 14,
16 to 18, and 18 to 26 inches, respectively. This
rate of growth in the fii-st and second years of life
is markedly greater than that existing in Keuka
Lake. With this start it is possible that the
hatchery fish spawned earlier than they would in
the wild, which is known to be true of some other
species of hatchery-reared trout, especially brook
trout.

The rapidly growing lake trout of Seneca Lake,
whatever their age, do not mature until they are
26 to 30 inches in total length; those of Keuka
Lake mature at a total length of 18 to 24 inches.
In Skaneateles Lake, N. Y., however, Rayner
(1941) captured many mature lake trout of 15
and 16 inches total length. Fry (1939) reported
that the minimum size at maturity in some lakes
of Algonquin Park, Canada, varied from 14 to 18
inches according to the lake.

Obviously with this variation in size at maturity,
a uniform minimum legal-size hmit of 15 inches,
such as exists in New York State, may permit
the taking of many immature, rapidly growing
fish in some lakes while providing entirely too
much protection in other lakes. It would appear
necessary to consider the growth rate and fishing
pressure in each lake in setting a mmimum size
limit.

Slowly growing lake trout may be subject to
senility at a small size. Fry and Kennedy (1937)
reported that none of the lake trout of more than

62

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

22 inches fork length in Lake Opeongo, Algonquin
Park, Ontario, were capable of spawning. Such
widespread inipotency was not observed in any
of the New York lake trout. The conservation
department employees engaged in spawn-taking
operations on the Adirondack and Finger Lakes
reported that only occasionally would an impotent
fish be found. The more limited observations I
made also failed to show any impotency, and it
is quite likely that after the lake trout in New
York State lakes are mature they may spawn
several times before succumbing to the infirmities
of age.

TIME OF SPAWNING *

The available information shows that lake trout,
and most other trout, spawn once a year in the
fall when the temperature is dropping and the
days are becoming shorter. Among different races
of lake trout, small variations in the spawning
date are found. This is true also of the same
race of lake trout in different lakes, and of the
same race in the same lake in different years.
It appears probable that fluctuations in light and
temperature, in the physical characteristics of
different lakes, and in the responses of different
races are the determining factors.

These factors have proved important in in-
fluencing the spawning time of other species.
Hoover and Hubbard (1937) have shown that
brook trout which normally spawned in Decem-
ber could be induced to spawn in late August
and early September by increasing the amount
of light in early spring and decreasing it in late
summer. Bissonette and Burger (1940) state
that "there is no uniform control of the sexual
cycle applicable to all fish. In some fish, tem-
perature seems to be the major factor; in others,
light and temperature play cooperative roles;
while in still others, light appears to be the most
important factor."

Merriman and Schedl (1941), on the basis of
laboratory experiments on the four-spined stickle-
back, Apeltes guadracus (Mitchill), concluded that
light influenced oogenesis but not spermato-
genesis, while temperature somewhat unequally
affected the maturation of the gonads of both
sexes. McCay et al. (1930) concluded on the
basis of feeding experiments that the spawning
time of brook trout could be influenced by the
food supply. They found that the age at ma-

turity could be advanced or postponed by in-
creasing or decreasing the amount of food fed
to the hatchery trout, but the question of chang-
ing the spawning date of mature trout was not
clarified.

After several years of netting lake trout in
Raquette Lake for spawn taking, the hatchery
men of the New York Conservation Department
have observed that the lake trout run earlier
after a sudden drop in temperature. The exten-
sive data on their operations were made avail-
able to me, and weather data were obtained
from the United States Weather Bureau (table 1).

Table 1. — Weather conditions in relation to peak of lake-
trout egg take at Raquette Lake, 1933-41

Year

Air tem-
perature '
(° F.)

Cloudy
days '

Peak of
egg take

1933

56.8
54.9
52.4
54.0
55.0
(')
55.4
53.4
56.6

22
21
24
19
21
(')
18
22
21

Oct. 22

1934

Oct. 18

1935

Oct. 13

1936

Oct. 19

1937

Oct. 21

1938

{')

1939

Oct. 23

1940

Oct. 19

1941

Oct. 19

' Average air temperature for the month of September at nearby Indian
Lake.

' Number of cloudy days in July, August, and September in the northern
plateau region of New York.

3 No eggs taken.

The average air temperature for September
reported by the Indian Lake weather station was
used because it was the nearest station to
Raquette Lake, with complete weather records for
the 8 years of spawning data. The average
number of cloudy days for the entire northern
plateau region of New York was selected because
many of the smaller stations had no automatic
sunshine recorders and their estimates of cloudi-
ness varied considerably. The number of cloudy
days in July, August, and September was used
because the work of Hoover and Hubbard (1937)
indicated that changes in the light required a
considerable time to influence the development
of the eggs, and these 3 months were the ones
preceding the spawning season which had
decreasing amounts of daylight.

The analysis of these data by multiple regres-
sion (table 2) indicated that the date of spawning
was advanced by lower temperatures or a greater
number of cloudy days and retarded by warmer
weather or fewer cloudy days. However, neither
on air temperature alone nor on cloudiness alone

LAKE TROUT BREEDING HABITS

63

was the partial regression of the spawning date
statistically significant. When both factors were
considered in a multiple regression coefficient the
result was significant (7?=. 8643 when R of .836
or greater is to be expected 5 percent of the time
with 5 degrees of freedom).

Table 2. — Reduced data for tnutliple regression analysis of
the date of peak of lake-trout egg take at Raquetle Lake

i, = Avera!;e air temperature for the month of September
at Indian Lake.

i2= Number of cloudy days in July, August, and Septem-
ber in the northern plateau region of New York.

?/=Date of peak of lake-trout egg take.

Number of observations: n = 8

Means:

i, = 54.81 X2 = 21.00 17=10.25

Sums of squares:

&,2= 16.01

Sums of products;
Sj 1X2= -6.80

Sx22 = 24.00 5i/2 = 65.50

Sz2y= -27.00 St,!/ = 23.08

Correlation coefficients:

r,2=-.3469 r,2=-.6810 r„ = .7534

Standard partial regre.ssion coefficients:

B„,.2 = .5675 B„2.,= -.4841

Multiple regression equation:

B= - 80.3 -I- 2.32A',- 1.32X2

Tests of Sionikic^nce:

Standard partial regression coefficients: (DF = 5)

.5675

for B„i 2 (
for B„2 1 ( =

.2398
.4841

= 2.366
= 2.019

.2398
neither significant
Multiple correlation or multiple regression: (DF = b)
/? = .8643 significant

A similar analysis of data on the peak of egg
take from Upper Saranac Lake (tables 3 and 4)
was less conclusive. The date of peak of egg take
in 1941 was about a month later than usual, but
if we omit this aberrant observation the date of
the peak at Upper Saranac Lake seems to bear
the same relation to air temperature and cloudiness
as at Raquette Lake. However, neither the partial
nor the multiple regression coefficients are signifi-
cant. (R=. .699 when R of .930 or greater is to be

expected 5 percent of the time with 3 degrees
of freedom).

Table 3. — Wealher conditions in relation to peak of lake-trout
egg take in Upper Saranac Lake, 1935-41

Year

Air tem-
perature'
(°F.)

Cloudy
days'

Peak of
egg take

52.3
56.9
54.8
52.0
M.g
52.4
57.2

24
19
21
28
18
22
21

Oct. 17

1936

Oct. 23

1937 _

Oct. 21

193g

Oct. 15

1939

Oct. 24

1940

Oct. 26

1941

Nov. 20

I Average air temperature for tlie month of Septemljcr at nearby Tupper
Lake.

' Number of cloudy days in July, .\ugust, and Septemi>er in the northern
plateau region of New York.

Table 4. — Reduced data for the multiple regression anaylsis
of the date of the peak of lake-trout egg take at Upper
Saranac Lake

ii = Average air temperature for the month of September
at Tupper Lake.

i2 = Number of cloudy days in July, August, and Septem-
ber in the northern plateau region of New York.

y=Date of peak of lake-trout egg take.

Number of observations: n = 6 '

Means:

*, = 53.87

Sums of squares:

Sxi2= 19.03

Sums of products:
Si,X2= -28.10

i2 = 22.00 j/ = 21.00
5x2' = 66.00 Si/2 = 90.00
Sx2)/=- 62.00 5x,!/= 19.00

Correlation coefficients:

r,2=-.7929 r,2=-.6263 r„, = .4591

Standard partial regression coefficients:

B„i.2=-1008 B„2.i=--7062

Multiple regression equation:

£:= 50.94 -.219A'i-.825A'2

Tests op Significance:

Standard partial regression coefficients: (Df = 3)

.1008

for B„i.2 < =
for /?„2 1 ' =

6776
7062

= .1488

= 1.0421

6776

neither significant

Multiple correlation or multiple regression: (,DF = S)
ff = .6990 not significant

1941 data omitted.

64

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Other things must be considered in evaluating
these analyses. The data are few, only 6 years in
one instance and 8 in the other, and the Weather
Bureau data on air temperature and cloudiness
cannot be a precise measurement of the tempera-
ture and the light actually affecting the fish.
Furthermore, the period during which the light
and the temperature changes are influential can
only be surmised, and other factors may be
important. For example, in Raquette Lake in
1938 the notably high water level was suspected
of being the cause of almost no lake trout being
caught. However, it was not certain whether this
affected the migrations or prevented the nets from
operating effectively.

Considering that a significant relation was
established in one instance, and that other data
were inconclusive but showed a similar tendency,
it is probable that both light and temperature do
influence the spawning time of lake trout.

Lake trout in Raquette Lake (Oliver R. Kings-
bury, report to the New York Conservation De-
partment, November 1935) spawn at about the
time of the lake turn-over. In the middle of the
1935 spawning season, temperatures taken at the
surface and at depths down to 56 feet revealed
no more than a 3° F. difference between top and
bottom. This seems to be more important than
the actual surface temperature in influencing
spawning, for the surface temperature on the day
the first eggs were taken was 58° F. in 1933, 52° F.
in 1934, and 50° F. in 1935. Merriman (1935)
reports lake trout spawning in Squam Lake, N. H.,
when the surface temperature was 42° F. In
Otsego Lake in 1940 the lake trout were observed
spawning December 5, when the surface tempera-
ture was 37° F. No facilities were available for
taking deep-water temperatures at that time, but
in 1941 the fish were observed late in their spawn-
ing season on December 3, when the water tem-
perature was uniformly 43° F. from the surface
down to 60 feet. These wide variations in surface
temperature indicate its slight value as a deter-
minant of the date of spawning.

Such differences in the progress of cooling in
different lakes are probably associated with the
depths of the lakes, and it appears that the depth
of a lake is associated with the time of lake-trout
spawning. Table 5 presents data from the files of
the New York State Conservation Department on
the time and duration of lake-trout spawn taking

Table 5. — Duration of lake-trout spawn taking operations
by State Conservation Department in some New York
lakes

Year

Date first
eggs r(>
eeived at
hatch-
ery

Date of
peak of
egg take

Date last
eggs re-
ceived at
hatch-
ery

Raquette Lake (alt. 1,762 ft.; max. depth 96
ft.);

1933

1934 ___

Oct. 14
Oct. 14
Oct. 11
Oct. 16
Oct. 16
Oct. 16
Oct. 12
(')

Nov. 5
Oct. 31
Nov. 5
Nov. 2
Nov. 4

(')
Oct. 12

Oct. 13

(')
Oct. 12
Oct. 16

Oct. 17
Oct. 15
Oct. 13
Oct. 10

Oct. 20
Sept. 23
Nov. 20

(')
(»)

('J
P)
(')
(')

Oct. 22
Oct. 18
Oct. 13
Oct. 19
Oct. 21
Oct. 23
Oct. 19
Oct. 19

(')

(')

(')
Nov. 6
Nov. 8

Oct. 14

(')

(')
Oct. 22
Oct. 16
Oct. 21

Oct. 25
Oct. 24

(')
(')

Oct. 24
Oct. 10

Nov. 25

Oct. 17
Oct. 23
Oct. 21
Oct. 15
Oct. 24
Oct. 26
Nov. 20

Oct. 24
Oct. 20

1935

1936 --

Oct. 16
Oct. 21

1937

Oct. 26

1939

Oct. 26

1940

Oct. 24

1941

(')

Lake George (alt. 322 ft.; max. depth 187 ft.):
1928

Nov. 14

1929

Nov. 5

1932

Nov. 13

1936

Nov. 9

1938

Nov. 11

Lake Pleasant (alt. 1,724 ft.; max. depth 53
ft.):

1930

1932

(')
Oct. 15

Sacandaga Lake (alt. 1,724 ft.; max. depth
60 ft.):

1929

Oct. 13

1930

Oct. 26

1932

Oct. 23

1933 ..

Oct. 23

Piseco Lake (alt. 1,661 ft.; max. depth 129 ft.):
1930 . .

Oct. 29

1931 ...

Nov. 5

1932

Oct. 28

1933

Oct. 15

Seventh Lake (alt. 1,786 ft.; max. depth 85
ft.):

1933

Oct. 24

Seneca Lake, (alt. 444 ft.; max. depth 625 ft.):
1939-41 2

Nov. 3

KeukaLake (alt. 709 ft.; max. depth 187 ft.):
1936-39 '

Dec. 3

Upper Saranac Lake (alt. 1,571 ft.: max.
depth 100 ft.):

1935

(=)

1936

(')

1937

(')

1938

0)

1939

m

1940

(')

1941

(')

' Data not available.

Same dates were reported (or each year.

' Data depended on hatchery schedule rather than lake-trout migrations.

operations in some New York lakes. Figure 2,
which incorporates information from table 5, from
Rayner (1941) for Skaneateles Lake, and from my
observations on Otsego Lake, shows this relation
graphically.

It appears that the lake trout spawn early in
the shoal lakes and later in the deep lakes. If, as
indicated previously, they spawn at about the
turn-over time of the lake, this would be expected,
as the deeper lakes cool off more slowly.

Like so many rules, the one that the deeper
the lake the later the lake trout spawn has an out-
standing exception. In Seneca Lake, the deepest
lake in New York State (625 feet maximum
depth), the lake trout spawn the earliest. They
start in late September and continue through
October, spawning in water from 100 to 200 feet

LAKE TROUT BREEDING HABITS

65

10

1 I 1

° 5

-

O OTSEGO L

/

30

-

/

25

-

Okeuka l /

f

JJO

_

/

—

3

/

O SKANEATELES L

t>5

Z

-

/

-

• C

-

/ Ol GEORGE

-

5

—

/

~

30

-

/

-

25

SEVENTH

vCf O PISECO L

-

I 20

O

SACANOfiGA

'7

/ O UPPER SARANAC L
O PAOUETTE L-

-

10

A

^ PLEASANT

5

-

{ 1

SENECA L »

1 t

1 1 1 1 1 1 1 i

1 1 1 1 1 1

z
<
in 5|—

100 20D 300 40^

MAXIMUM DEPTH IN FEET

Fir.iRE 2. — Relation of average date of peak of lake-trout
spawning activity and maximum depth of some New-
York lakes.

deep at a time well in advance of the turn-over
period of the lake. Data taken from September
29 to October 17, 1941, showed that the surface
temperature ranged from 57° to 62° F.

This large deviation in the time of spawning
may be attributed to racial differences in the lake
trout. Milner (1874) gives the spawning time of
the siscowet (Cristmimer namaycush siscowet) as
late August and early September in the deep
waters of Lake Superior. In the same lake the
common lake trout {Salreliniis [ = ('ristimmer]
namaycush) spawns in from 7 feet to 15 fathoms
of water during the month of October and in early
November (Milner 1874, Van Oosten 19:55).
Hubbs (1930) has described the Rush Lake trout
{Cristivomer namaycush huronicus) and states
that it spawns in deep water in late summer rather
than in fall, as does the common lake trout in the
same lake. Dymond (1926) gives the time of
spawning of the common lake trout as the month
of October in Lake Nipigon, Ontario. But he

points out that tliere is a race of black trout in
the same lake which ascends some of the tributary
streams and starts spawning about September 20,
and a third race which is said to spawn in deep
water from October 20 to November 10.

In New York State the spawning data indicate
that two races' of lake trout e.xist: One, the
Seneca Lake trout, spawns early in deep water,
and the other, widespread in the Finger and
Adirondack Lakes, spawns in shallow water at
about the time of the turn-over of the lake.

With these differences in reactions and spawning
habits, it would be desirable to determine if the
Seneca Lake trout can adapt themselves to the
conditions existing in Adirondack Lakes and vice
versa before extensive stocking is attempted.
Lntil such knowledge can be secured it would be
wise to stock lake trout in lakes similar to those
from which the eggs were obtained.

DURATION OF THE SPAWNING PERIOD

Data on the receipt of lake-trout eggs at some
of the New York State hatcheries are summarized
in table 5. The date of receipt of eggs corresponds
closely to the date of take, except for the first
one or two days of the spawning season. Ordi-
narily, only a few ripe fish are found at first,
and if only a few thousand eggs were obtained,
they often were held for a day or two until more
eggs were available to make the trip to the hatchery
worth while. The date the first eggs were taken
probably averages about 1 day earlier than the
date of their receipt at the hatchery. At the
peak of the spawning season the eggs were usually
rushed to the hatchery immediately, so the date
of the peak receipt of eggs corresponds to the date
of the peak egg take.

The tlata in table 5 do not indicate the com-
plete spawning season but rather the season dur-
ing which it was feasible to catch and strip the
trout. High water sometimes so affected the
fishing of the nets that it was not practical to
continue fishing, and bad weather sometimes cut
short the stripping operations. Hence, a short
period of egg take is not necessarily indicative of a

1 other evidence of racial dilTerence is available. New York State fi.sll
hatchery foremen agreed that ckks from Seneca Lake trout averaped ahout
240 an ounce, while egps of lake trout of comparable size from Adirondack
lakes averaeed about 200 to 210 an ounce. No measurements of the actual
diameters of the ecRs were available, but the counts of the hatchery foremen
appeared to be fairly consistent. I). C. llaski'll (unpublished material
gathered in 1941) also reports that th<' Seneca Lake trout grow signifiointly
raster under hatchery conditions than the young laki- trout from Ranuelte
atHi t'pper Saranac Lakes.

66

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

short spawning season. It seems likely, however,
that the longer periods of spawn taking closely
approximate the spawning season.

It appears that the lake-trout spawning season
lasts from 10 to 20 clays in the smaller New York
lakes and the duration is fairly uniform in the
same lake from year to year. The lake trout of
Lake George consistently completed their spawn-
ing in 7 to 10 days at the most.

The length of the spawning season increases
in the larger lakes. Van Oosten (1935) gives the
duration of the spawning season in Lake Michigan
as October 10 to November 21; in Lake Huron,
October 10 to November 15; and in Lake Superior,
October 1 to November 6. Seneca Lake is
similar to the Great Lakes in both date and
duration of the spawning season. The earliest
and latest dates on which the New York State
Conservation Department obtained eggs in Seneca
Lake were September 23 and November 3. These
dates are for difTerent years, but the earliest and
latest dates were similar from year to year.

PLACE OF SPAWNING

The observations of Merriman (1935), Royce
(1936), and the writer indicate that lake-trout
spawning areas are restricted to bottom of clean
gravel or rubble, free of sand and mud. As the
fish make no effort to bury the eggs, the bottom
must have crevices into which the eggs can roll,
if eggs and larvae are to be protected.

The location of these suitable areas of bottom
in the lake is primarily determined by currents
or wave action which keep the bottom swept clean.
The lake trout will roll the smaller stones around
and fan oflF the silt, but they cannot remove sand
or mud from the crevices. Any bottom that is
not swept by currents or waves eventually becomes
covered with mud, although in the usual oligo-
trophic lake-trout lake this process would take a
very long time.

In the littoral zone, the width of the area of
clean rocks or sand is dependent directly on the
size of the lake and its exposure to the wind. In
the smaller New York lakes the lake trout general-
ly may be found spawning by windy points near
deep water (Royce 1936), on bottom kept clean
by the waves. A typical example of such shallow-
water spawning is to be found in Otsego Lake.

In larger lakes the lake trout may go to deeper
water for their spawning. Milner (1874) reports
that the lake trout in Lake Superior spawn in
7 feet to 15 fathoms of water. Evidence of
spawning in the deep water was provided by the
capture of ripe fish at that depth and by raising
in the nets fragments of honeycombed rocks
containing eggs. In Seneca Lake the lake trout
are captured for stripping in 100 to 200 feet of
water at a time when no lake trout are found in
shallow water. The fact that ripe lake trout
are captured over bottom that is suitable for
spawning is strong evidence that the trout
actually are spawning at these depths. Further
proof was provided by the capture on the spawning
bed in Seneca Lake, in April 1940, of a lake-trout
fry 25 millimeters in total length, in water 130
feet deep.

There is much evidence that these deeper
spawning areas are swept by strong currents.
The hatchery fishermen reported that their nets
were often rolled over and over by the currents
in Seneca Lake. In this same lake off Peach
Orchard Point the 40° F. isotherm rose from a
depth of 260 feet on September 29, 1941, to 100
feet on October 1 after a strong south wind;
on October 7 it was back down to a depth of 230
feet. Such a change must be accompanied by
the movement of a huge quantity of water.

These currents in Seneca Lake and the other
Finger Lakes have left evidence of a prevailing
direction of flow. All these lakes are very long
and narrow and lie with their long axes in very
nearly a north-south direction. Seneca Lake is
the largest, being about 40 miles long and 3 miles
wide at its widest point. The prevailing winds
come from the northwest or the southeast, blow-
ing obliquely to the south on the eastern shore
and obliquely to the north on the western shore
of the lake. The general result has been to form
the tips of deltas to the south of the stream mouths
on the eastern shore of the lake and to the north
of the stream mouths on the western shore.

In addition to the characteristic orientation of
the deltas, there is a definite gradation in the size
of the material deposited in the various parts of
the delta. Off the tip of Peach Orchard Point in
Seneca Lake down to a depth of at least 300 feet,
only clean gravel and rubble could be found with
a clamshell dredge, or seen in bottom photo-

LAKE TROUT BREEDING HABITS

67

A

1

>

9

i

n

§>'

{^

f

m

1 ^

Figi;r?; 3. — The bottom of Seneca Lake west-southwest off the tip of Peach Orchard Point where the lake trout congregate
during the spawning season. The picture covers an area on the bottom about 18 by 24 inches at a depth of 120
feet.

68

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

graphs* (fig. 3). The hghter materials, such as
mud, were deposited in the coves adjacent to
Peach Orchard Point.

Evidently other deltas in this lake have similar
deposits, since lake trout are captured in large
numbers during the spawning season near the
tips of the points.

The writer has found no evidence that lake
trout select a lake bottom supplied with spring
water for the deposition of their eggs. The
spawning area in Otsego Lake was on a fill about
100 feet out from the original shoreline which was
bedrock and showed no evidence of any spring
seepage. Comparison of numerous water tem-
peratures taken on the spawning area and in the
nearby lake at all seasons of the year showed no
difference in temperature. Additional evidence
was the presence of as thick an ice cover over the

' Ewing. Vine, and Worzel (1946) describe submarine photographic equip-
ment and techniques in detail.

spawning area on March 31 as on other parts of
the lake, just before the spring breakup, when any
springs should have caused some erosion of the
ice. No mention of spring water on lake-trout
spawning areas has been found in the literature
I have reviewed. It is concluded that for lake
trout, unlike some other species of trout, spring
water is a negligible factor in selection of a
spawning area.

SPAWNING ACT

All my observations on the spawning act of
lake trout reported here were made at a spawn-
ing area on Otsego Lake, N. Y. Otsego Lake is
about 8 miles long and averages three-fourths of
a mile in width. Its maximum depth is 168 feet,
and about 90 percent of the lake is more than 60
feet deep (Odell and Sennmg 1936). Chemical
conditions are ideal for lake trout, and the lake
has produced fairly good lake-trout fishing for

Figure 4.— The courtship act. The male at the left is nudging the female in the side.

LAKE TROUT BREEDING HABITS

69

many years. The spawning area kept under ob-
servation — the only one well known to the local
residents and the only one that could be found —
was along the middle of the west shore opposite
the deepest part of the lake.

Observations were made in this area on Novem-
ber 16 and 30 and on December 1 and 5, 1940,
and on December 1, 2, and 3, 1941. The trout
were observed from 7 a. m. to 11 p. m. on some
of those days, but the area was visited mostly in
the evening.

Some trout were on the spawning area at all
times of day during the spawning season, but most
of the activity was restricted to the evening hours.
During periods of bright sunlight only a few males
could be seen and they kept to fairly deep water
so that observation was difficult. The direct
rays of the sun were cut off by a mountain about
4 p. m. and then many trout, both males and
females, would arrive on the spawning area, and
the males would start courtship and attempt the
spawTaing act. The peak of the activity was

from 5 p. m. to 9 p. m. Later in the evening the
trout again disappeared until only a few were
left at 1 1 p. m., when observations were discon-
tinued.

No nest or redd was built. The males spent
their time cruising along close to the bottom,
occasionally giving the stones a little fillip with
their tails, and several showed considerable abra-
sion on the lower jaw and under side of the tail
from this fanning and digging. This activity
cleaned several hundred square feet of bottom so
thoroughly that it was easy to distinguish the
area on which the trout were working even when
they were not present.

It has been the experience of employees of the
New York State Conservation Department in
netting lake trout for spawn that the males appear
in the nets on the spawning area earher in the
season than the females, and usually more males
are caught. From this experience, and from the
fact that the males predominated on the area in
Otsego Lake, it seems probable that the males

Figure 5. — Just after completion of the spawning act. Two males have spawned with the female in the center.

70

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

are almost entirely responsible for any cleaning of
the spawning area before spawning.

Belying their appearance, the males are not
pugnacious. Occasionally one would make threat-
ening motions at another male, but no vigorous
fighting was observed. Several whitefish (Core-
gonus dupeaformis) and a large eel (Anguilla
hostoniensis) were seen among the milling lake trout
and were unmolested. It was noted, however,
that the males were nearly of the same size. Per-
haps they had already disposed of any venture-
some small males.

Merriman (1935) and others have observed the
spawning lake trout splashing at the surface. In
Otsego Lake this was noted only infrequently,
possibly because the spawning was on a steep
slope in 2 to 15 feet of water — deeper water than
that in which Merriman made his observations.

The males began their courtship upon the ap-
pearance of the females on the spawning area.
Usually the male nudged the female in the side
with his snout (fig. 4) and then attempted the
spawning act. Frequently two or more males
courted and attempted to spawn with a female at
the same time. During courtship the males dis-
played the characteristic coloration (fig. 1) and
commonly held the dorsal fin erect. These dis-
plays were apparently identical to those noted by
Merriman (1935).

The spawning act or attempts at it normally
consisted of one or two males approaching a
female, pressing against her sides with their vents
in close proximity and then quivering all over
(fig. 5). Usually the mouths of both sexes were
open and the dorsal fin of the male was held erect.
This act was seen clearly at close range several
times when no eggs or milt were expressed. On
two occasions a cloudiness was noted in the vi-
cinity of the vents which probably was caused by
the emission of sperm. No eggs were seen but
this could have been because of the distance of the
observer from the fish and the turbidity of the
water. No other act or behavior was seen which
could be construed to accompany oviposition.
Probably the attempt at the spawning act is a
part of courtship and is repeated over and over
again until fulfillment.

The spawning act was not limited to two or
three trout; as many as seven males tad three
females were seen at one time, all pressing to-
gether in one large group and quivering in unison.

No spawning act lasted for more than a few sec-
onds, and it seems that a female must accomplish
many unions to empty the ovaries completely.
The trout are not monogamous and it was impos-
sible to follow the movement of any one pair in
the milling group.

No tendency toward oviposition in any definite
place on the spawning area was observed. The
trout mated at random over the area cleaned off,
and there was no attempt by either sex to bury
the eggs. This seeming carelessness in regard to
the fate of their young was justified when one
attempted to find the eggs. A casual examination
of the bottom revealed practically no eggs, but
they could be picked up by the hundreds when
the stones were turned over carefully. Eggs were
recovered in water from 3 inches to 14 feet in
depth. Those collected in more than 2 feet of
water had to be taken in a Petersen dredge and
no estimate of their abundance could be obtained.
Along shore in less than 2 feet of water, however,
where only an occasional trout was seen spawning,
from 20 to 50 eggs could be recovered per square
foot of bottom. The eggs were difficult to pick
up, and the slightest motion of the water sent
them rolling further into crevices between the
rocks. In their selection of the bottom on which
to spawn, the lake trout had chosen an ideal
shelter for their eggs and young.

ENVIRONMENT AND DEVELOPMENT OF
EGGS AND LARVAE

EFFICIENCY OF FERTILIZATION

It has been a long-cherished belief of fish
culturists that the natural spawning of trout is a
highly inefficient, hit-or-miss process. Critical
investigations have shown this belief to be untrue.
White (1930) was able to hatch 79 percent of a
sample of naturally fertilized brook-trout eggs
removed from their redd and placed in a hatchery,
and 66 percent of another lot placed in a screen
basket and reburied in the redd. Hobbs (1937),
after intensively investigating the redds of brown
trout, rainbow trout, and quinnat salmon, found
that more than 99 percent of the eggs were
fertilized. He also found that subsequent heavy
loss in the pre-eyed, eyed, and alevin stages was
a result of adverse environmental conditions.
Under favorable conditions the natural reproduc-
tion was a highly efficient process.

LAKE TROUT BREEDING HABITS

71

A check of the natural spawning of lake trout
in Otsego Lake provided further evidence that
natural reproduction is efficient. On December 28,
1941, about 25 days after the trout were observed
on the spawning area, a sample of 309 eggs was
collected from under the rocks along shore with
a small rubber bulb and tube. Of these 309 eggs,
18, or 5.8 percent, were not fertihzed, and 47,
or 15.2 percent, had died. Seventy-nine percent
of the eggs were ahve and apparently entirely
normal after having been on the lake bottom nearly
a month. This probably represents a near mini-
mum figure for the survival (exclusive of those
eaten by predators) inasmuch as the eggs were of
necessity collected in only a few inches of water
where they were subject to heavy wave action.
The vast majority of the eggs were laid in deeper
water out of reach of available collecting appara-
tus and where they should have been better
protected.

TEMPERATURE REQUIREMENTS

Lake-trout eggs appear both to require and to
withstand slightly lower temperatures than the
eggs of other trout. Embody (1934) found that
brook- and rainbow-trout eggs suffered excessive
mortaUty and developed at a different rate when
the water temperature was below 37.4° F.' He
found, also, that lake- and brown-trout eggs
followed the same rate of development down to
35.2° F., and he judged that development pro-
ceeded normally. Brook trout usually spawn in
spring water so that their eggs are not subjected
to near-freezing temperatures during the winter
(Greeley 1932, Hazzard 1932, White 1930). Rain-
bow trout normally spawn in the spring when the
water is warming (Rayner 1941). Cook (1929)
reports that lake-trout eggs develop satisfactorily
at the Duluth, Minn., hatchery where water
temperatures remain about 32.5° F. throughout
the winter. The 140-day incubation period of
lake-trout eggs in Otsego Lake indicates an
average temperature of 36° or 37° F. in the egg-
development tables of Embody (1934). At the
Rome, N. Y., State hatchery high mortality
occurred in lake-trout eggs developing at water
temperatures above 50° F. when other trout eggs
developed normally. In other hatcheries, lake-
trout eggs from the same source developed nor-

* Rainbow-trout cpgs suiterod hiph mortality at temp(?raturcs below 43° F.,
but Emtwdy thought that in some cases this was due to inferior eRjts.

mally at lower temperatures. These facts would
indicate that lake-trout eggs can develop success-
fully in a lake in the winter, so long as they do not
freeze, and that they do not require spring water.
No data arc available on the temperature
requirements of the alevins. In the spring of
1941 they left the spawning area in Otsego Lake
when the water temperature was about 55° F.
It seems likely, therefore, that they avoid tem-
peratures above 60° F.

EFFECTS OF PREDATION

The data on the survival of eggs in Otsego
Lake do not indicate the true value because
they do not consider the removal of eggs by
predators. Predators are an ever present danger
to lake trout from the egg stage almost to maturity,
and cause a loss which is exceedingly difficult
to evaluate. No precise measurements have
ever been made on the effects of predation at any
stage in the growth of wild trout.

Many are the potential predators of eggs and
alevins. Table 6 lists the animals captured
within 100 yards of the lake-trout spawning area
in Otsego Lake during April and May 1941.
Many of these would destroy eggs if eggs were
availabe to them. Atkinson (1931) and Greene,
Hunter, and Senning (1932) found that numbers
of lake-trout eggs were eaten by suckers {Cat-
ostomus commersonii) and bullheads {Ameiurus
nebulosus). Both of these species occur in Otsego
Lake although they were not captured in the
immediate vicinity of the lake-trout spawning
area. Greeley (1936) states that a fisherman
reported finding lake-trout eggs in the stomachs
of Otsego Lake whitefish. Rayner (1941) found
many lake-trout eggs in the stomachs of adult
lake trout. A female taken by the writer on the
Otsego Lake spawning area had 13 lake-trout
eggs in its stomach. Small lake trout may be
even more voracious predators. W. C. Senning,
in a letter to me, reported finding lake-trout eggs in
every one of 31 small lake trout taken on the
spawning grounds in Seneca Lake in the fall of
1942. These lake trout ranged from 6K to 13
inches in length, and one 12-inch individual
had eaten 147 eggs. White (1930) found large
numbers of brook-trout eggs in brook-trout stom-
achs. Metzelaar (1929) reported that rainbow
trout ate numbers of their own eggs. Greeley
(1932) found brooks, browns, and rainbows to

72

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Table 6. — Animals found on and near lake-trout spawning
area in Otsego Lake, Apr. 27-June 2, 1941

Phylum and
order

Coelenterata

Platyhelminthes.
Arthropoda;

Amphipoda.

Neuroptera...

Ephemerida. ,

Do-

Do

Do

Do

Odonata

Do

Do

Do

Do

Do

Do

Plecoptera

Coleoptera . . .

Trichoptera- .

Do

Do

Do

Diptera

Do

MoUusca:

Gastropoda...
Do-

Pelecypoda..
Chordata:

Pisces

Do

Do

Do

Do-

Do

Do

Do

Do

Do

Do

Do.

Do

Amphibia...

Species

Hydra sp

Planaria sp-

Hyalella sp

Sialis sp -

BlastuTUi sp -.

Ephemerella sp

Stenonema sp

Hexagenia sp

Ephemera sp

Qomphus sp -

Didymops transversa

Epicordulia princeps

Helocordulia tihleri. .

Neurocordulia obsoleta^ ..

Argia moesta

Enallagma sp

Neoperla sp

Dineutes sp

Stenophylaz scabripennis .

Molanna sp

Phryganea sp

Qtossosomatinae '

Chironomus sp

Tanytarsus sp

Limnea sp

Planorbis sp

Unidentifiable.

Coregonus dupeaforrrtis ^ .
Cristivomer n. namaycush.

Notropis h. hudsonius

Hyborhynchus notaius

Esoi niger

Angidlla hostoniensis

Perca fjavescens

Stizosledion v. vitreum

Bolesoma nigrum olmstedi
Micropterus d. dolomieu..

Lepomis gibhosus

AmhloplUes rupestris.

Cottus cognatas

Triturus viridescens.,.

Common name

Alderfly..
Mayflay.
....do---

do--.

do...

.do-

Dragonfly

do

do

. -do

do

Damsel fly

do..

Stone fly

Whirligig-beetle.

Caddisfly

do

do

do

Midge..

do..

Pond snail . .
Wheel snail.
Clam

Whiteflsh

Lake trout

Spot-tail shiner

Blunt-nosed min-
now.

Chain pickerel

American eel

Yellow perch

Yellow pike-perch.

Johnny darter

Small-mouthed

bass.
Pumpkinseed (sun-
flsh).

Rock bass

Slimy muddler

Newt -.-

Stage

Larva.
Nymph.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Larva.
Do.
Do.
Do.
Do.
Do.

' Two or more species.

be trout-egg eaters. On the Otsego Lake spawn-
ing area, an eel (Anguilla bostoniensis) and several
whitefish (Coregonus clupeajormis) were seen
industriously feeding among the stones where
the lake trout were spawning. In addition, a
slimy muddler {Coitus cognatus), which is known
to eat trout eggs, was captured in the immediate
vicinity.

What is the effect of this predation? Greeley
(1932) concluded that practically all the eggs of
rainbow, brown, and brook trout eaten were
waste eggs not buried in the redd, and that the
effect of egg predators on reproduction was neg-
ligible. Hobbs (1937) thought that the number
of eggs eaten from the redds of rainbow and
brown trout and quinnat salmon was very small.
The spawning trout themselves are important
predators but they could scarcely be accused of
eating all their own spawn.

It seems likely that predation would have no

more effect on the eggs of lake trout than it has
on those of other trout. If the lake trout can
spawn on the type of bottom they seem to prefer,
the eggs and alevins are certainly well protected
until they emerge from the rubble. It was neces-
sary to dig deep into the rubble in the Otsego
Lake spawning area to capture either eggs or
alevins.

Additional evidence is provided by the lack of
any lake-trout alevins in the stomachs of the
following fish captured in the immediate vicinity
of the lake-trout spawning area between April
27 and June 2, 1941:

6 whitefish {Coregonus clupeaformis)

I adult lake trout {Salvelinus { = Cristivomer] namay-
cush)

II shiners {Notropis hudsonius)

1 blunt-nosed minnow {Hyborhynchus notatus)

1 chain pickerel {Esox niger)

17 yellow perch {Perca flavescens)

22 johnny darters {Boleosoma nigrum olmstedi)

I smallmouth bass {Micropterus d. dolomieu)
4 common sunfish {Lepomis gibhosus)

13 rock bass (Ambloplites rupestris)

II slimy muddlers {Cottus cognatus)

These fish were all captured during the pre-
sumably vulnerable time the alevins were absorb-
ing the yolk sac and leaving the spawning bed.
Such negative evidence is inconclusive but reassur-
ing.

It is important to note that most trout-egg
predators have been indicted for their activities
during the time the eggs were being laid and not
after the eggs were hidden in the gravel. It is
concluded that lake-trout eggs and alevins suffer
little from predation after the spawning season,
and that during spawning the eggs that are eaten
are only those left exposed on the bottom.

DEVELOPMENT OF EGGS AND ALEVINS

Greeley (1936) collected eyed eggs and newly
hatched alevins on the Otsego Lake spawning
area on April 12, and more-advanced alevins on
May 9. I took newly eyed eggs on February 17,
1941, and later-eyed stages on March 31, 1941, by
chopping holes through the ice. (The lake trout
had been observed spawning December 5, 1940.)
Later, on April 27, with the surface water tempera-
ture 44° F., newly hatched sac fry were taken, and
on May 17, 1941, many more-advanced fry were
taken (temperature data in fig. 6). All the stages
were taken from the rubble on the spawning area.

LAKE TROUT BREEDING HABITS

73

30 40

TEMPERATURE

50 60 70

IN DEGREES FAHRENHEIT

Figure 6. — Temperature stratification of Otsego Lake
associated with different stages of larval development of
lake trout.

(Several hauls of the trawl in the vicinity of the
spawning area on April 27 and May 17 produced
no fry.) Both eggs and fry were well buried in the
stones. The eggs were taken with a Petersen
dredge, and only after the surface stones were
removed could they be found. The fry were all
taken with a trawl fitted with a heavy weight in
front which turned over the stones. On June 2,
1941, 18 tows of the trawl over the spawning area
and in the vicinity down to depth of 60 feet failed
to produce any young lake trout. They had
definitely moved from the spawning area and the
habitat of the earhest feeding stages was still
unknown.

Comparison of the development of wild fry
which were captured and of those grown in a hatch-
ery indicates that the time of hatching in Otsego
Lake in 1941 was about April 15, and the fry
left the shelter of the spawning area May 20 to 25.

In Seneca Lake, where the lake trout spawn
during late September and October, a single ad-
vanced fry was captured in about 130 feet of water
off Peach Orchard Point on April 2, 1940. This
fry was considerably more advanced than a

hatchery fry 2 months old. This would place
the time of hatching in late January and indicate
an incubation period of approximately 4 months.
Consideration of the type of bottom and the
kinds of invertebrate inhabitants (table 6) of the
lake-trout spawning area in Otsego Lake empha-
sizes the striking resemblance of this area to a
typical trout-stream environment. Clean gravel
and rubble bottom inhabited by stonefly and may-
fly nymphs and caddis larvae ordinarily would be
associated with a stream instead of a lake. Cer-
tainly it seems that lake-trout fry and fingerlings
would fare best under conditions similar to those
selected by the young of other trout.

This trout-stream-like environment in Otsego
Lake gave me high hopes of capturing the early
fingerling stages in the vicinity. But all efforts,
including those with minnow traps, trawl, and
shore seine, were unsuccessful. No helpful clues
were found in the literature, for lake-trout finger-
lings have been reported only from shoal water
and small tributaries. Kendall and Goldsborough
(1908) captured several lake trout, 1.87 to 2.37
inches long, in small spring tributaries of First
Connecticut Lake on July 16 and 18 and August
10. Neave and Bajkov (1929) reported taking
10 lake trout, 32 to 45 mm. long, with a hand net
in a small inlet creek at Pyramid Lake, Nev.
Miller and Kennedy (1948) noted that fry, and
1-, 2-, and 3-year-old lake trout were found in
shallow water along a bouldery shoreline of Great
Bear Lake, Mackenzie, Canada. Lake-trout fin-
gerlings are not found in such habitats in the
summer in New York. The biological survey of
the New York State Conservation Department
captured none in extensive seining of the shores
of the Adirondack lakes and streams, many of
which were adjacent to lake-trout waters. There
seems to be little doubt that in New York they live
in the deeper waters of the lakes in the summer
and probably seek rocky bottom.

JUVENILE LAKE TROUT OF KEUKA LAKE

Intermittently from April 18 to September 16,
1940, effort was made to capture fingerling and
juvenile stages of lake trout in Keuka Lake.
Their capture was attempted with gill nets, trawls,
set lines, and minnow traps. A number of 100-
foot sections of gill nets of %-inch to 1 J^inch bars
were set for an aggregate of 67 nights at depths of

74

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

10 to 130 feet. Fifty -nine tows of a trawl were
made over a similar range of depths. A set line
equipped with 80 No. 7 hooks was set for 4 days
covering depths from 15 to 40 feet. Minnow
traps were set for 8 days at depths from 40 to 80
feet.

Included in the catch were 41 lake trout (all
caught in gill nets) of which 13 were more than
15 inches in total length — the minimum legal size
in New York. The stomach content of the 13
legal-sized trout, and of 1 1 others of legal size
gathered from anglers, was 100 percent alewives
{Pomolobus psevdoharengus) or unidentifiable fish,
probably of the same species (anglers report
finding practically nothing but alewives in lake-
trout stomachs).

The lengths and stomach contents of the sublegal
specimens are listed in table 7. Of the 16 speci-
mens between 10 and 15 inches in length, only one
had eaten arthropods, while the principal food of
those between 6 and 10 inches was arthropods,
mostly Mysis relicta.

Table 7.

-Food of lake trout less than 15 inches long from
Keuka Lake, 1940

Total
length

(inches)

Date of
capture

Stomach contents

im.....

May 11

do

Empty.

Unidentifiable fish remains.

14

do

3 Pomolohus pseudobarengus' 2 unidentifiable fish

13ii

.. do

2 Pomolohus pseudoharengu3.

13

...do

12^

do

12)^.....

12H

llH---

n'A

IIM

June 29

May 11

June 29

May 24

.do

Do.
Do.
Do.
Do.
Do.

lOJ^

lOJi

May 11..

do

Do.
Empty.

lO^j ....

.. do

W'/s

lOJi

9H

9H

1;;::;;

Sept. 11

May 25

Sept. 13-16 ...

May 24

Sept. 13-16...

do

do

do

1 mayfly nymph (Ephemerinae); 1 unidentifiable
fish.

5 Pomolohus paeudokarengus.

1 Pungitius pungitius; 23 Mysis Telicta.

Unidentifiable fish remains.

1 Pungitius pungitius: 1 unidentifiable fish.

1 Cottus cognatus; 9 Afysis relicta.

12 Mysis Telicta.

7H-.---!

do

do

34 Mysis relicta.

6H

do

10 Mysis Telicta.

6'4

do . ..

do

6ii

do.

28 Mysis relicta.

Summary: Of lake trout 10 to 15 inches in total length, 14 stomachs con-
tained fish remains and 1 stomach contained arthropod remains. Of lake
trout 6 to 10 inches in total length, 4 stomachs contained fish remains and 10
stomachs contained arthropod remains.

In most cases capture of the lake trout was
very erratic. The 10 small specimens taken May
1 1 were found in the same place at very nearly the
same depth of 100 feet. Nets set there on follow-
ing nights caught nothing. The other small

specimens taken during May and June and all the
larger lake trout were caught, one or two at a time,
in different places but almost entirely at depths
of 80 to 120 feet.

Some consistency was found, however, in the
capture of the young lake trout caught September
11 to 16, 1940. These were taken, two or three
a rtight, in %- to K-inch bar gill nets set in one
restricted location off the southern tip of Bluff
Point, a very rocky, steep underwater slope,
between depths of 40 and 70 feet. Nets of the
same mesh set at the same depths in the vicinity
on mLxed mud and rubble bottom failed to catch
any trout. As large lake trout were taken in
larger-mesh nets in the same area, it seems that the
juveniles must have been relying on the shelter
of the rocks for protection from their voracious
elders.

Scale examination indicated that these 6}i- to 10-
inch trout were yearlings and 2-year-olds. Since
the lake trout of Keuka Lake spawn in late
November and probably hatch in late April
(see p. 64, table 5), a rate of growth comparable
to hatchery growth would allow them to reach
only 2 or 3 inches by the first September. Possibly
these fingerling fish could be found in the same
location as the yearlings were found. Lack
of time and equipment prevented any further
effort in this direction but it is a good stage at
which to resume the search in the future.

SUMMARY

Lake trout were observed during their spawning
season in 1939, 1940, and 1941 in several lakes in
New York State, and actual spawning was seen
in Otsego Lake, N. Y. Extensive data on spawn-
taking operations were obtained from the New
York State Conservation Department, and exist-
ing literature on the subject was reviewed.

It was found that, except for a striking color
change in the males while on the spawning area,
lake trout lack sexual dimorphism. They mature
in about their sixth year at lengths varying from
15 to 30 inches in the different lakes.

Spawning occurs once each year, during the
autumn. The date varies from late September
to early December depending on the race of trout,
the amount of sunlight, the autumnal drop in
temperature, and the depth of the lake.

In the deep water of Seneca Lake, one race

LAKE TROUT BREEDING HABITS

75

spawned early. In all other lakes studied, the
lake trout spawned in shallow water and usually
later. Increased cloudiness in July, August, and
September, and low temperatures in September,
advanced the date of spawning in Raquctte
Lake. Shallower lakes had earlier spawning
dates. At the time of spawning, water tempera-
ture varied from 58° to 37° F., but in Raquette
and Otsego Lakes it was observed that spawning
times approximated the turn-over times of the
lakes. Generally, the spawning period was about
20 days, but it varied from 10 to 40 days and was
fairly consistent from year to year in any one lake.

Spawning, whether in shallow or deep water,
took place on gravel or rubble bottom that had
crevices into which the eggs could roll. No nest
or redd was built. No evidence of spring water
was observed near any spawning area.

In the spawning act, which usually occurred
during the evening, from 2 to 10 lake trout par-
ticipated. Each attempt at spawning lasted
only a few seconds; the act was repeated many
times.

Approximately 1 month after spawning, a
sample of eggs recovered from the crevices in the
rocks of Otsego Lake was found to be 79 percent
alive. No measurement of the effects of preda-
tion on eggs was possible, but it was estimated
that only eggs that failed to roll into crevices
between the stones could be eaten by predators.

In Otsego Lake in 1941 the eggs hatched about
April 15 and the fry left the spawning area about
May 22. In the deep water of Seneca Lake
where the lake trout had spawTied in early October
a single advanced fry was taken April 2, 1940.
Its development indicated that hatching occurred
in late January.

Extensive operation of a small beam trawl, set
hnes, and minnow traps in Otsego, Keuka, and
Seneca Lakes failed to produce any lake trout
between advanced fry stage and a length of about
6 inches. Twelve specimens between 6 and 10
inches long that were captured in gill nets in Keuka
Lake were found to be 1- and 2-year-olds and to be
feeding mostly on Mysis relicta.

ACKNOWLEDGM ENTS

Deep appreciation is expressed to the following
people whose assistance made this work possible:
Dr. A. H. Wright, professor of zoology, Cornell

University, Ithaca, N. Y., gave much encourage-
ment and made funds available; Peter I. Tack,
A. H. Underbill, and William M. La%vrence,
graduate students, and Philhp Strong, fish hatch-
ery foreman, provided a large amount of help in
the netting operations and the aquatic photog-
raphy.

Members of the New York State Conservation
Department were most cooperative and generous
with their time and equipment. Among those to
whom I am particularly indebted are S. M.
Cowden, supervisor of fish culture; A. P. Miller,
district supervisor of fish culture; Dr. Emmehne
Moore and Dr. W. C. Senning, aquatic biologists;
Charles Deuell, David Haskell, K. B. Nichols,
and L. D. Winslow, fish hatchery foremen; and
L. D. Tompkins, game protector.

I am further indebted to V. S. L. Pate and
Minter J. Westfall, Jr., for identification of aquatic
insects from Otsego Lake, and to J. R. Westman,
for scale samples and data on the lake trout of
Lake Simcoe, Ontario.

LITERATURE CITED

Atkinson, N. J.

1931. The destruction of grey trout eggs by suckers and
bullheads. Trans. Amer. Fisheries Soc, vol. 61, pp.
183-188.
BissoNETTE, T. H., and J. Wendell Burger.

1940. Experimental modification of the sexual cycle of
fish. Abstracts of papers presented at the North-
eastern Fish Culturists' Meeting, p. 12.
Cook, W. A.

1929. A brief summary of the work of the Bureau of
Fisheries in the Lake Superior region. Trans. Amer.
Fisheries Soc, vol. 59, pp. 56-62.
Dymond, John Rich.\rd80N.

1926. The fishes of Lake Nipigon. University of
Toronto Studies, Publications Ontario Fisheries Re-
.search Laboratory, No. 27, pp. 3-108.
Embody, George C.

1934. Relation of temperature to the incubation periods
of eggs of four species of trout. Trans. Amer. Fish-
eries Soc, vol. 64, pp. 281-292.
EwiNG, Mavrice, a. Vine, and J. L. Worzel.

1946. Photography of the ocean bottom. Jour. Optical
Soc. America, vol. 36, No. 6, June 1946, pp. 307-321.
Fry, F. E. J.

1939. A comparative study of lake trout fisheries in
Algonquin Park, Ontario. Univ. of Toronto Studies,
Biol. Ser., No. 46: Publications of the Ontario Fish-
eries Research Laboratory, No. 58, pp. 7-69.
Fry, F. E. J., and W. A. Kennedy.

1937. Report on the 1936 lake trout investigation,
Lake Opeongo, Ontario. Univ. of Toronto Studies,

76

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Biol. Ser., No. 42: Publications of the Ontario Fish-
eries Research Laboratory, No. 54, pp. 3-20.
Greeley, John R.

1932. The spawning habits of brook, brown, and rain-
bow trout, and the problem of egg predators. Trans.
Amer. Fisheries Soc, vol. 62, pp. 239-248.

1936. A Biological Survey of the Delaware and Susque-
hanna Watersheds. II. Fishes of the area with an-
notated list. Supplemental to 25th Ann. Rept., New
York Conserv. Dept., 1935, pp. 45-88.

Green, C. W., R. P. Hunter, and W. C. Senning.
1932. A Biological Survey of Oswegatchie and Black
River systems. Spjtwn-eating by suckers and bull-
heads. Supplemental to 21st Ann. Rept., New
York Conserv. Dept., 1931, pp. 26-28.

Hazzard, a. S.

1932. Some phases of the life history of the eastern
brook trout Salvelinus fontinalis (Mitchell). Trans.
Amer. Fisheries Soc, vol. 62, pp. 344-350.

HoBBS, Derisley F.

1937. Natural reproduction of the Quinnat salmon,
brown and rainbow trout in certain New Zealand
waters. New Zealand Marine Dept., Fisheries Bull.,
No. 6, pp. 7-104.

Hoover, Earle E., and Harry E. Hubbard.

1937. Modification of the sexual cycle in trout by the
control of light. Copeia, No. 4, pp. 206-210.
HuBBS, Carl L.

1930. Further additions and corrections to the list of
the fishes of the Great Lakes and tributary waters.
Papers of the Michigan Acad. Science, Arts and
Letters, vol. XI, pp. 425-436.
Kendall, William Converse, and E. L. Goldsborough.
1908. The fishes of the Connecticut Lakes and neighbor-
ing waters. U. S. Bur. Fisheries Doc. No. 633,
77 pp., 10 pis., 5 figs.
McCay, C. M., L. a. Maynard, J. W. Titcomb, and
M. F. Crowell.
1930. Influence of water temperature upon growth and
reproduction of brook trout. Ecology, vol. XI, pp.
30-34.
Merriman, Daniel.

1935. Squam Lake trout. Bull. Boston Soc. Nat.
Hist., No. 75, pp. 3-10.
Merriman, Daniel, and H. P. Schedl.

1941. The effects of light and temperature on game-
togenesis in the four-spined stickleback, Apeltes

quadracus (Mitchill). Jour. Exper. Zool., vol. 88,
No. 3, pp. 413-449.
Metzelaar, Jan.

1929. The food of the trout in Michigan. Trans.
Amer. Fisheries Soc, vol. 59, pp. 146-152.
Miller, R. B., and W. A. Kennedy.

1948. Observations on the lake trout of Great Bear
Lake. Jour. Fisheries Research Board of Canada,
vol. 7, No. 4, Feb. 1948, pp. 176-189.
Milker, James W.

1874. Report on the fisheries of the Great Lakes; the
result of inquiries prosecuted in 1871 and 1872.
U. S. Fish Comm. Rept. 1872-73, Part II, pp. 1-78.
Mottley, C. McC.

1936. The hooked snout in the Salmonidae. Prog.
Repts. Pacific Biol. Sta., Nanaimo, British Columbia,
and Pacific Fish. Exp. Sta., Prince Rupert, British
Columbia, No. 30, pp. 9-10.
Neave, F., and A. Bajkov.

1929. Reports of the Jasper Park lakes investigations,
1925-26. V. Food and growth of Jasper Park fishes.
Contrib. to Canadian Biol, and Fisheries, New Ser.,
vol. IV, No. 16, pp. 199-299.

Odell, T. T., and W. C. Senning.

1936. A biological survey of the Delaware and Susque-
hanna watersheds. III. Lakes and ponds of the
Delaware and Susquehanna watersheds. Supple-
mental to 25th Ann. Rept., New York Conserv.
Dept., pp. 89-121.
Rayner, H. J.

1941. The development of a management policy for the
rainbow trout of the Finger Lakes. Ph. D. Thesis,
Cornell Univ., June 1941.
Royce, James S.

1936. Collecting eggs from lake trout in New York
lakes. Fish Culture, 2 pp.

SURBER, ThADDEUS.

1933. Rearing lake trout to maturity. Trans. Amer.
Fisheries Soc, vol. 63, pp. 64-68.
Van Oosten, John.

1935. The value of questionnaires in commercial fisher-
ies regulations and surveys. Trans. Amer. Fisheries
Soc, vol. 64, pp. 107-117.
White, H. C.

1930. Some observations on the eastern brook trout
(S. fontinalis) of Prince Edward Island. Trans.
Amer. Fisheries Soc, vol. 60, pp. 101 108.

U S. GOVERNMENT PRINTING OFFICE

UNITED STATES DEPARTMENT OF THE INTERIOR, Oscar L. Chapman, Secretary
FISH AND WILDLIFE SERVICE, Albert M. Day, Director

DECLINE OF THE LAKE TROUT FISHERY

IN LAKE MICHIGAN

By Ralph Hile, Paul H. Eschmeyer, and George F. Lunger

FISHERY BULLETIN 60

From Fishery Bulletin of the Fish and Wildlife Service

VOLUME 52

UNITED STATES GOVERNMENT PRINTING OFFICE

WASHINGTON : 1951

For sale by the Superintendent of Documents, U. S. Government Printing Office, Washington 25, D. C.

Price 20 cents

CONTENTS

Page

Materials and methods 77

Production trends in Lake Michigan, 1879-1949 78

Production in State of Michigan waters, 1891-1908 and 1929^9 81

Abundance in State of Michigan waters, 1929-49 88

Fishmg intensity in State of Michigan waters, 1929^9 90

Relations of production, abundance, and fishing intensity 92

Summary 94

Literatm'e cited 95

II

DECLINE OF THE LAKE TROUT FISHERY IN LAKE MICHIGAN

By Ralph Hile and Paul H. Eschmeyer, Fishery Research Biologists, and George F. Lunger, Statistician

Collapse of the fishery for lake trout, Salveliniis
[=Cristivomer] namaycush, of Lake Huron has
been treated in detail in a recent publication by
Hile (1949). In the present paper we take up the
unpleasant task of describing the decline of the
lake-trout fishery in yet another of the Great
Lakes, Lake Michigan. Lake Superior now stands
as the only significant center of conunercial pro-
duction of that species yet remaining in the United
States.

In this, as in the earher paper mentioned, treat-
ment will be limited to a statistical account of the
changes that have taken place in the lake-trout
fisheiy. We offer no extended argument on the
role of the sea lamprey in this most recent debacle,
other than to express the considered opinion that
on the basis of ciu-rently available evidence this
parasite must be held the major cause of the
catastrophes that have overtaken both Lake
Huron and Lake Michigan.

MATERIALS AND METHODS

The statistics on the production of lake trout
in the individual States over the period 1879-
1940, incorporated in table 1, were adapted from
Gallagher and Van Oosten (1943) and are from
the sources listed in that publication. Our annual
totals, however, are in agreement with those of
Gallagher and Van Oosten only for those years in
which statistics were available for aU four States
bordering the lake. In a number of years statis-
tics were at hand for Michigan and Wisconsin but
not for lUmois and Indiana; in such situations
those authors recorded the yields from the first
two States as the totals for Lake Michigan. Our
totals in the same situations include estimates of
the Illinois-Indiana catch. On the basis of the
actual distribution of the take among the States
in the 8 years with complete data from 1885
through 1917 and in the 6 years ' from 1922

' For this purpose the 1925 data were usable since the Indiana-Illinois
catch was included in the total; statistics for the two States Individually,
however, were not available.

through 1929 we derived the correction factors
1.0291 and 1.0683. The former factor was ap-
plied to the combined Michigan-Wisconsin catch
to give an adjusted grand total in years lacking
lUinois-Indiana data through 1919; the latter
factor was used for years after 1919. To be sure,
the percentage contribution of Illinois and Indiana
varied within each of the two periods, but the
derivation of a greater munber of factors would
not have been profitable. We have not consid-
ered it advisable to estimate the Lake Michigan
total in any year for which we had data for only
one State.

Statistics on production after 1940 were com-
piled directly from commercial fishei-men's re-
ports in the Ann Arbor offices of the Fish and
Wildlife Service (Michigan) or supplied by State
conservation agencies (Wisconsin, Illinois, and
Indiana) .

The data on the yield of lake trout in the several
statistical districts of the State of Michigan waters
of Lake Michigan for 1891-1908 were tabulated in
the Service's Great Lakes offices from original
records supplied by the Michigan Department of
Conservation."

The detailed information on production, fishing
intensity, and estimated availability of lake trout
in the State of Michigan waters in 1929^9 is
based on analyses of monthly reports of com-
mercial fishermen licensed by the State of Michi-
gan. These reports, which were supplied by the
department of conservation, contain data on
fishing locality, kind and amount of gear fished,
and kinds and quantities of fish captured for each
day of fishing by each Ucensee.

The methods employed in estimating the
abundance of the principal species and the intens-
ity of the fishery in the State of Miciiigan waters
of the Great Lakes have been described in detail in
earlier publications (Hile 1937; Hile and Jobes

> The Works Progress Administration gave valuable assistance in this
vorlc

77

78

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

1941; Van Oosten, Hile, and Jobes 1946). The
boundaries of the eight statistical districts, M-1 to
M-8, are given in figure 2.

PRODUCTION TRENDS IN LAKE
MICHIGAN, 1879-1949

The trends of production of lake trout from 1879
through 1949 perhaps can be brought out best
through comments on the yield over certain
periods of years (tables 1 and 2; fig. 1).

The take in 1879, the fu'st year for which we have
a record, was comparatively low (2,659,000
pounds). Catches were higher in 1885 (6.431,000
pounds) and 1889 (5,580,000 pounds) but the take
in each of those years and the mean for the two
(6,006,000 pounds) were far below the level that
characterized the period beginning with 1890.
It may be assumed that the fishery was in the
process of development in 1879-89.

The interval 1890-1911 was one of rather con-
sistently high production. The take exceeded 8
million poimds in 7 of the 11 years for which lake
totals are recorded and was more than 9 million
pounds in 1 of these 7 (9,282,000 pounds in 1896).
Of the remaining 4 years, 2 had yields between 7
and 8 million pounds, 1 between 6 and 7 million,
and 1 less than 6 million. The two lowest catches
(6,624,000 poimds in 1892 and 5,286,000 pounds
in 1899) both deviated sharply from the general
level for the period and both can be attributed to
the low yields recorded for Wisconsin. The grand
average catch => for 1890-1911 was 8,230,000
pounds or 2,224,000 pounds greater than for 1885-
89. Every State but Indiana shared in the in-
crease; the rise was greatest, however, in Wiscon-
sin (1,950,000 pounds).

The production of lake trout in Lake Michigan
was at a decidedly lower level in 1912-26 when the
average yield of 7,007,000 pounds was 1,223,000
pounds below that of 1890-1911. Of the 14 years
for which there are totals (see footnote 1 to table 1
concerning the exclusion of data for Wisconsin in
1921) 5 had catches between 7 and 8 million
pounds, 8 between 6 and 7 million pounds, and 1
less than 6 million pounds. The highest yield was
7,928,000 pounds in 1915 and the lowest was
5,979,000 pounds in 1918. Dechnes from the
preceding period of 932,000 pounds in Wisconsin

> To obtain full use of the data of table 1, the means in the body of table 2
were determined from all records of yield for each State during the indicated
periods and these State means were added to obtain the totals at the right.

and 459,000 pounds in Michigan, were compen-
sated to a small degree by increases of 132,000
pounds in Indiana and 36,000 poimds in Illinois.

Table 1. — Production of lake trout in Lake Michigan,
1879-1949

[In thousands of pounds]

Year

State

Total

Michigan

Wisconsm

Illinois

Indiana

1879

2,659

1880

1881

1882

1883

1884

1885. - -

3,725

2,668

4

34

6,431

1886

1887

1888

1889

2,950
4,674

2,455
3.464

25
72

150
155

5,680

1890

8,364

1891

3,686
3,616
3,122
2 668

2'82i"
5,404
5, 865

1892

6,624

1893

8,774

1894

8,781

1895

2,392

5,304

7,920

1896

3,020
2,872

6,000
4,711

-J--

...

9,282

1897

7,823

1898

2,540
2,370
2,016
2,844

1899

2,804

77

35

6,286

1901

~

1902

4,337
4, 055

1903

4,613

199

76

8,943

4,254
4,456

1905 -

1906

6,103

1907

4,271

1908

4,023

4,328

150

130

8,631

1909

_»-

4,337

1911

3,526

4,640

8,404

3,003

3,558

6,752

IQia

2,544

3,761

6,488

1914

2,711

4,126

7,036

191=1

3 853

3 851

7,928

IQlfi

2,805

3,195

6,174

1917.

2,866

3,745

169

123

6,904

2 456

3, .354

5,979

2,735
3,143

3, 849
3,840

6,776

1920.

7,461

3,107
3,264

■8,642
3. 801

12,651

19?2

203

272

7,640

1923

2,767
3 472

3.419
3 752

6,599

1Q?4

7,717

1Q95

3,422

3. 101

J 6, 894

1926

3,352

2,762

165

250

6,530

1927

2,900

2, 379

167

2.53

6,699

1928..

1,831

2.629

172

187

4,819

1929

2,198

3,817

247

132

6,394

1930.. ..

2,556

2,316

383

186

5,441

1931...

2, 6.52

2,673

202

106

6,632

1932

2,746

2,345

281

98

6,470

1933... . .

2,379

2,481

262

90

6,212

1934

2,053

2,590

225

88

4,957

1935. -_

2, 451

2,042

260

120

4,873

1936

2,127

2,232

274

130

4, 763

1937

2,264

2,353

271

100

4,988

1938

2,480

1,940

311

174

4,906

1939 -

2,778

2,358

318

205

6,660

1940.

2,780
3,189

2,492
2.747

814
705

179
146

6,266

1941.

6,787

1942

2,641
2, 814

2.695
2,825

1,111
1,193

38
28

6,484

1943

6,860

1944 .

2,609
2,228

2,852
2,516

1,036
694

6,498

1945.

5,437

1946

1,908
914

1,650
1,178

416
333

1
1

3,974

1947 -

2,425

1948.

589

542

65

C)

1,197

1949.

223

116

4

342

1 The recorded yield of 8,642,000 pounds in Wisconsm in 1921 is so badly
out of line with data for neighboring years as to be held unreliable. It was
not plotted in fig. 1 or employed in the computation of any means or per-
centages.

2 No breakdown available of the 371,000 pounds taken in Indiana and Illi-
nois.

» Less than 500 pounds.

DECLINE OF LAKE TROUT IN LAKE MICHIGAN

79

1920

1945

Figure 1. — Production of lake trout in Lake Michigan, 1889-1949. Upper solid line = entire lake; broken line=

Wisconsin; lower solid line = Michigan.

The take of lake trout fluctuated about a still
lower level in 1927-39 when the average total for
the lake was 5,293,000 pounds, 1,714,000 pounds
below the mean for 1912-26 and 2,937,000 pounds
less than that for 1890-191 1. The catch exceeded
6 million pounds only once in 13 years (6,394,000
pounds in 1929 — again a sharp deviation of the
Wisconsin figure from the characteristic level was
responsible for the extreme) ; it was between 5 and
6 million pounds in 6 years, and less than 5 million
pounds in 6 years. The lowest catch of the period
was 4,763,000 pounds in 1936. Michigan, Wis-

consin, and Indiana contributed to the decline
from 1912-26 to 1927-39 with decreases of 616,000,
1,107,000, and 71,000 pounds, respectively. The
Illinois catch, on the contrary, was increased by
80,000 pounds in the latter period.

The lake-trout fishery of Lake Michigan enjoyed
a brief period of heightened productivity in 1940-
44 when the take exceeded 6 million pounds in
every one of the 5 years and averaged 6,578,000
pounds, or 1,285,000 pounds above the 1927-39
mean. To a considerable extent the improvement
can be attributed to the large increase of 713,000

80

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Table 2. — Average production of lake trout in Lake Michigan, by periods
[In thousands of pounds]

Period

Number
of years '

Item

State

Michigan Wisconsin Illinois Indiana

Total

1879

1885-89..

1890-1911

1912-26

1927-39

1940-44

1946-49

Production-
Mean annual

Percentage
Mean annual

Percentage
Mean annual

Percentage
Mean annual

Percentage
Mean annual

Percentage
Mean annual

Percentage

production..

of total

production.

of total

production.

of total

production.

of total

production.

of total

production,
of total

3,338

55.6
3,492

42.4
3,033

43.3
2.417

45.7
2,807

42.7
1.172

43.8

2,562

42.7

!4.512

54.8

' 3, 580

61.1

' 2, 473

46.7

2, 722

41.4

1,200

44.9

14
2
143
1.8
179
2.6
269
4.9
972

14.7
302

11.3

92
1.5

83
1.0
215
3.1
144
2.7

78

1.2

2,659
6,n06

100
8,230

100
7,007

100
6,293

100
6,578

100
2,674

100

1 Number of years for which statistics were available in at least 1 State or
for the entire lake.

2 The reported Wisconsin production for the years 1892 and 1899 was far
below the level characteristic of the period. If these years are excluded, the
Wisconsin mean becomes 4,822 and the percentages and total change
accordingly.

pounds in Illinois, a rise exceeding the combined
increases in Michigan (390,000 pounds) and Wis-
consin (249,000 pounds). Indiana alone experi-
enced a decline (66,000 pounds).

The sharp drop in the recorded Indiana take to
a lower level during the 1940-44 interval probably
reflects improvement in the collection of statistics
more than a decrease in output. Indiana pro-
ducers, who traditionaUy take the bulk of their
catch of lake trout in State of Michigan waters,
have to our best knowledge customarily reported
their entire production to both Indiana and Mich-
igan. There is considerable evidence, therefore,
that part of the take of Indiana fishermen in
earlier years was reported in duplicate. In view
of the relatively small production of these opera-
tors, the efl^ects on the statistics for the entire lake
were not particularly damaging, but the figures for
Indiana before about 1942 must be viewed with
some skepticism.

The period 1940-44 is exceptional for its brevity.
Statistics for the preceding three periods demon-
strated a tendency for the productivity of the lake-
trout fishery to fluctuate closely about a character-
istic level for from 13 to 22 years. In view of this
tendency, it might well be expected that the new
high level reached in 1940 would be maintained
longer than 5 years. That it was not maintained
suggests that some disruptive factor intervened.
The sea lamprey qualifies well as that factor.

Although the downward trend of production

' Excluding 1921 for which year the reliability of the Wisconsin data appears
questionable.

* The reported Wisconsin production for 1929 was considerably above the
level characteristic of the period. If this year is excluded, the_ Wisconsin
mean becomes 2,362 and the percentages and total change accordingly.

actually started a year earlier, 1945 can be set a
the beginning year of the recent disastrous decline.
In this year the catch dropped by more than a
million pounds and fell distinctly below the level
of 1940—44. Once the decline started, its progress
was spectacular. In 1946 the take was under 4
million pounds for the first time since 1879, and
each of the years 1947 to 1949 set a new record
low. It is the high rate of decrease rather than
the average of 2,674,000 pounds that makes the
1945-49 period significant.

The collapse of production in the lake-trout
fishery of Lake Michigan resembles closely that
described for Lake Huron by Hile (1949). Indeed,
the decline appears to have been even more rapid
in Lake Michigan than in the United States
waters of Lake Huron. This point can be brought
out by a comparison of the number of years
required for a 90-percent or gi-eater decline from
the last year with the take above the "modern"
average. In Lake Michigan this average can
be set at 5,651,000 pounds (the mean for 1927-44),
and the last year in which the take exceeded that
figure was 1944 (6,498,000 pounds); only 5 years
later the catch had dropped by 94.7 percent
(to 342,000 pounds m 1949). In the United
States waters of Lake Huron the "modern normal
yield" was set by Hile at 1,685,000 pounds (the
mean for 1895-1939), and the last year with an
output above this figure was 1935 (1,743,000
pounds); 10 years were required for the catch
to decline 90.1 percent (to 173,000 pounds in 1945).

DECLINE OF LAKE TROUT IN LAKE MICHIGAN

81

PRODUCTION IN STATE OF MICHIGAN
WATERS, 1891-1908 AND 1929-49

Records of the annual take of lake trout in the
several statistical districts * of the State of
Michigan in 1891-1 90S (table 3) make possible
the comparison of the actual productivity of
various regions and of their percentage contri-
butions to the total for the lake * in that period

Table 3. — Production of lake troul in Michigan statistical
districts, 1891-1908
[In thousands of pounds]

District

Year

Total

M-1

M-2

M-3

M-4

M-5

M-6

M-7

M-8

1891

171

349

1,554

130

346

228

395

513

3,686

1892

35

390

1.691

77

379

290

257

496

3,616

1893 - -

174

144

1,392

98

311

318

360

324

3,122

18M

142

249

1,285

86

255

224

185

243

2,668

1895

109

57

1,312

118

267

185

165

180

2,392

1896

119

392

1,529

151

307

207

160

155

3,020

1897

176

411

1,456

76

212

200

174

167

2,872

1S98

161

288

1,367

46

233

258

98

89

2, 540

1899

127
90

264
191

1,160
782

47
42

298
259

190
190

130
195

164
266

2,370

1900

2.016

IWl . .

168

361

1,073

78

330

344

212

279

2. 844

1902

307

470

1,704

112

362

345

542

493

4,337

1903

380

598

1,534

94

422

246

368

412

4, 055

1904 ,

363

572

1,708

138

428

311

296

438

4, 254

1905

382

538

1,903

158

443

380

238

412

4.456

1906 -

332

348

2, 325

195

498

503

446

456

5. KB

1907

299

298

1,670

170

437

446

503

448

4,271

1908

300

421

1,.553

134

33U

m

484

318

4,023

1891-1908

mean.

213

352

1,500

108

340

297

289

325

3,425

Percentage

of total-.-

6.2

10.3

43.8

3.2

9.9

8.V

8.4

9.5

100

Table 4. — Production of lake trout in Michigan statistical

districts, 1929-49

[In thousands of pounds]

Year

District

Total

Produc-
tion
indei i

M-1

M-2

M-3

M-4

M-5

M-6

M-7

M-8

1929

182
203
220
194
134
72
77
158
236
248
167
83
75
56
91

146

S.7

47
29
11
46
178
149

153
234
300
331
298
276
242
269
296
243
234
220
354
251
299

266

10 5

195
145
79
25
25
3

912
986

1,020
898
692
669
771
823
738
801

1,047
739
910
684
837

835

32.9

675
599
448
219
87
23

68
90
102
113
102
71
89
76
88
117
100
109
141
133
122

101

4.0

131
96
68
38
19
13

273
286
321
387
449
380
432
363
447
437
407
427
449
385
453

393

15.5

462
299
263
126
86
21

291
270
291
354
303
278
306
143
147
183
286
424
413
283
274

282

11.1

251

227

152

71

19

5

146
224
249
313
206
144
234
111
131
148
195
289
414
342
216

224

8.8

261
247
293
155
45
2

174
262
148
156
196
163
300
193
180
303
370
488
432
508
523

293

11.5

587
586
593
234
131
6

2,198
2,556
2,662
2.746
2,379
2,053
2.461
2.127
2,254
2,480
2,778
2,780
3.189
2,641
2,814

2,540

100

2,609

2,228

1,908

914

589

223

86

19.30

101

1931

104

1932

108

1933

94

1934. _..

81

1935

96

1936

84

1937- -

89

1938-

98

1939

109

1940

109

1941

126

1942

104

1943

HI

1929-43 mean.
Percentage
of total.-..

1944

100
103

194.5

1946

1947

88
75
36

1948

23

1949 _

9

with conditions in recent years (table 4). Despite
the considerable fluctuations in annual yield in
the different districts to be seen in table 3, com-
ments on the 1891-1908 data* will be restricted
to the averages; we are without the information on
fluctuations in the availability of lake trout, in
the intensity of the fishery, and in other conditions,
that we need for an intelligent treatment of the
matter. Attention should be called, however, to
the distinct similarity of trends in production in
the several districts.

District M-3 strongly dominated the production
of lake trout in the State of ^lichigan waters of
Lake Michigan in 1891-1908, contributing 43.8
percent of the total output for the period. The
percentages for five of the seven remaining districts
e.xhibited only small differences, ranging from 10.3
percent for M-2 which held second position to 8.4
percent for M-7 which ranked sixth. The lowest
average yields were in M-1 (6.2 percent) and M-4
(3.2 percent). In this early period, waters north
of Grand Traverse Point (M-1, M-2, and M-3) ac-
coimted for 60.3 percent of the total output as
compared with 39.7 percent for districts M-4
through M-8.

To facilitate comparisons between the produc-
tion of lake trout in the statistical districts in
1891-1908 (table 3) and 1929-43, the"base period"
for modern statistics (table 4), a summary (table
5) has been prepared. The principal features of the
comparison are a generally lower level of take in the
more recent period, a shifting of production toward
the more southerly districts, and a lack of pro-
noimced changes in the ranking of the districts
with respect to the percentage of total yield.

Only M-5 exhibited a rise in average armual
production from 1891-1908 to 1929-13 (an increase
of 53,000 pounds). The remaining seven districts
all suffered declines that ranged from 7,000 pounds
in M-4 to the tremendous drop of 665,000 pounds
in M-3. This latter decline accounted for most of
the decrease of 885,000 poimds for the combined
districts. In no other district did the take fall by
more than 86,000 pounds (the decrease for M-2).

1 Percentage of 1929-43 mean.

' See figure 2 for the boundaries of the statistical districts.
' The term "lake" in this and the following sections has reference to State
of Michigan waters only.

• The data for 1891-1908 provide a less reliable record of production in the
individual districts than do those for 1929 and later. In the earlier period
the annual catch of each fisherman was allocated to the district in which his
home port was located, whereas in the recent period each day's catch was
credited to the statistical district in which the gear actually was lifted. The
extent to which fishermen operated outside their home districts in 1891-1908
is unlmown, but records for recent years suggest that error from this source
was not sufficiently great to affect the validity of comparisons based on tables
3 and 4,

82

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

STATUTE MILES

10 j 10 20 30 40 iO

Figure 2. — Statistical districts in State of Michigan waters of Lake Michigan.

DECLINE OF LAKE TROUT IN LAKE MICHIGAN

83

Table 5.-

—Comparison of average production of lake trout in Michigan statistical districts, 1891-1908 oi

id 19S9-4S

District

1891-1908

1929-43

Change. 1891

-190S to 1929-43, in—

Average
produc-
tion '

Percentage
of total

Hank

Average
produc-
tion'

Percentage
of total

Rank

Average
produc-
tion '

Percentage
of total

Rank

M 1 ---

213
352
1,500
108
340
297
289
325

6,2
10.3
43.8
3.2
9.9
8.7
8.4
9.5

7
2
1
8
3
5
6
4

146
266
835
101
393
282
224
293

5.7
10.5
32.9

4.0
15.5
11.1

8.8
11.5

7
5
1
8
2
4
6
3

-67
-86
-665
-7
-1-53
-15
-65
-32

-0.5

+.2

-10.9

-f-.8
-f5.6
+2.i

+.i
4-2.0

M 2 -

-3

M 3 _ _

M-4 __

\I-S

+1

M 6 __

+1

M 8 - - -

-1-1

3.424

100

2.640

100

-885

I Mean annual production in thousands of pounds.

The large drop in production in M-3 from 1891-
1908 to 1929-43 was reflected in a decrease of 10.9
in the percentage contribution of the district to the
total output of the State of Michigan waters (from
43.8 to 32.9 percent). The only other district in
which the percentage decreased was M-1 (a drop
of but 0.5). The remaining six districts experi-
enced increases in percentage that ranged from .2
m M-2 to 5.6 in M-5. These changes in the vari-
ous districts resulted in a noticeable shift of produc-
tion toward the south. Districts JM-1, M-2, and
M-3, which, as noted earlier, contributed 60.3
percent of the total in 1891-1908, accounted for
only 49.1 percent in 1929^3. The proportion for
M^ through M-8 rose correspondingly from 39.7
to 50.9 percent. A similar shift in production of
lake trout toward the south was described for the
State of Michigan waters of Lake Huron by Hilo
(1949).

Rather than burden the present section, which
deals with production trends in 1929-49, with
numerous micxplained exceptions to general state-
ments, it is believed desnable to anticipate discus-
sion that logically should appear later and describe
at this tune the peculiar situation in district M-1
that makes the data for that area so difficult to fit
into a general account of the lake-trout fishery of
the State of Michigan waters of Lake Michigan.
This difficulty has its origin in the circumstance
that M-1 is not true "lake-trout water" and that
the commercial catches of the species are normally
part of the production in a fishery aimed primarily
at the taking of lake whitefish (Coregonvs clupea-
formis). As a result, the intensity of the fishery
for lake trout, and consequently the production as
well, are controlled to a large degree by the condi-
tions of the whitefish fishery. This relation is
brought out rather forcefully by the data of table

933837—51 2

6 on the production, abundance, and fishing in-
tensity for the two species in M-1 over the period
1929^9.

The salient features of table 6 are summarized
briefly in the foUowing sentences. First, the pro-
duction of whitefish in M-1 normally is consider-
ably greater than that of lake trout. In only 2
of the 15 yeai-s of the base period 1929-43 was the
take of lake trout the greater, and the 15-year
average for whitefish was nearly three times that
for lake trout. In the years after 1943 the ad-
vantage of whitefish was much greater than in the
earlier, more nearly nomial period. Second, the
availability of lake trout and the intensity of the
fisher}^ for that species did not exhibit the positive
con-elation that would be expected if abundance

Table 6. — Comparison of lake-trout and whitefish fisheries in
district M-1, 1929-49

Lake trout

Whitefish

Year

Pro-
duc-
tion '

Abun-
dance
iudej '

Fishing-
inten-
sity
index >

Pro-
duc-
tion 1

Abun-
dance
index '

Fishing-
inten-
sity

index ' •

1929 - -

182

203

220

194

134

72

77

158

236

248

157

83

75

56

91

146

47
29
11
46
178
149

71
65
69
80
97
92
87
137
157
112
94
105
138
96
100

100

63
61
32
20
44
45

162
198
204
155
88
49
56
72
94
139
105
49
35
37
67

100

66
36
22
111
253
207

1,140

1,076

1,196

910

238

263

175

90

105

354

238

123

116

93

141

417

232

234

514

2.427

3,066

2.263

180
145
143
120
66
91
89
75
65
104
86
74
90
SO
92

100

114
100
148
275
221
168

199

1930

238

1931 ....

234

1932

187

1933

62

1934

46

1935

67

1936

42

1937 -

47

1938

120

1939

83

1940

37

1941

36

1942

44

1943

1929-43 mean

1944

1945

1946 _

1947

68

100

90

97

139

397

1948

629

1949

600

' In thousands of pounds

' Percentage of 1929-43 moan.

' Operations with large-mesh gill nets only.

84

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Table 7.- — Correlations between abundance and fishing-
intensity indices for lake trout and whitefish in district
M-1

Indices correlated

Period '

1929-41

1929^3

1929-19

Abundance of trout : Fishing intensity for
trout

Abundance of whitefish : Fishmg intensity

-0.611
.888

-.710
.961

-.736

.779

.553
.684

-0. 553
.891

-.690
.955

-.704

.778

.514
.641

-0.316
.800

Abundance of trout : Abundance of white-
Fishing intensity for trout : Fishing inten-
sity for whitefish -

-.745
.786

Abundance of trout : Fishing intensity for
whitefish

-.250

Fishing intensity for trout : Abundance of
whitefish

Value of r at p — 05 -

.561
.433

.549

' Data given for two earlier periods as well as for entire 21 years since war-
time conditions disrupted normal trends in fishing intensity after 1941 and
the extremely low abundance of lake trout introduced a disturbing factor
after 1943.

were an important factor in deteimining the rate
of fishing; the correlation that did exist is negative
(table 7). It should be emphasized here that the
estimate of fishing intensity for a particular
species is based only on gear lifted on days when
some quantity of that species was captured. Third,
the fluctuations in fishing intensity for lake trout
followed closely those of the gUl-net fishery for
whitefish (most lake trout are captured in gill nets),
and fishing intensity for whitefish in turn was
correlated closely with the fluctuations in the
abundance of that species. The data of tables 6
and 7 thus offer rather conclusive evidence that

the availability of whitefish is of primary signifi-
cance in the determination of the intensity of the
lake-trout fishery.

The situation just described for district M-1 is
not entirely without paraUel. Hile (1949) demon-
strated that in three districts of Lake Huron in
which lake trout and whitefish ordinarily were
taken together in a "two-species fishery" (catches
of other varieties in this type of fishery are usually
imimportani) the fluctuations in the availability
of whitefish exerted a readily detectable effect on
the fishing intensity for lake trout. The condi-
tions in M-1 merely represent an extreme because
of the strongly predominant position of whitefish
in the joint fishery and also because of the tre-
mendous upturn in the abundance of whitefish and
hence in fishing intensity for both whitefish and
lake trout at a time when the availability of the
latter species was far below normal.

Comments on the 1929-49 trends of production
in the several statistical districts as recorded in
table 4 will be based largely on the summary in
the top section of table 8. Reference to the pro-
duction curves of figures 3, 4, and 5 also should
prove helpful.

A pronounced difference is to be detected be-
tween the "northern" districts (M-1, M-2, M-3)
and the remaining or "southern" districts with
respect to the calendar years of highest produc-
tion of lake trout within the period 1929-49. Of

Table 8. — Summary of -production, abundance, and fishing intensity for lake trout in Michigan statistical districts, 1929-49

Item

District

All
districts

M-1

M-2

M-3

M-i

M-S

M-6

M-7

M-8

combined

Peodcction:

1 1938

1941

1939

1941

1944

1940

1941

1946

1941

3 years cf greatest production

1 1937

1932

1931

1942

1943

1941

1942

1944

1943

I 1931

1931

1930

1944

1941

1932

1932

1945

1940

Last year with production average or greater

'1939

1943

1943

1944

1944

1942

1946

1946

1944

First year of recent progressive decline

J 1944

1944

1944

1945

1945

1941

1947

1947

1944

First year with production less than half average

> 1944

1946

1947

1947

1947

1947

•1948

1948

1947

Abundance;

( 1937

1936

1939

1943

1943

1940

1941

1942

1943

3 years of greatest abundance

{ 1941

1933

1941

1935

1944

1941

1942

1943

1941

[ 1936

1931

1932

1934

1941

1943

1943

1944

1942

Last year with abundance average or greater

1943

1941

1943

1944

1946

1946

1947

1947

1944

First year of recent progres.sive decline

•1944

• 1944

1944

1944

1944

•1944

1942

1943

1944

First year with abundance below 70 percent

'1944

1944

1946

•1947

1948

1949

1949

•1949

1947

Fishinointensitt:

( (')

1941

1930

1940

1933

1931

1931

1946

1930

.1 yenrsj nf grentp.<;t inteiritty

\ (')

1943

1931

1930

1932

1932

1932

1940

1931

I (')

1942

1938

1932

1937

1930

1930

1935

1932

T-ast year with inten'^ity average or greater ._ ,_.

(')

1944

1945

1945

1939

1941

1946

1946

1941

First year nf recent progressive decline

(')

1944

1946

1945

1947

1942

1947

1947

'1947

First year with intensity less than half average

(')

1947

1948

1948

1947

1947

1948

1949

•1949

' 1948 and 1949 production above average.
2 Decline interrupted by increases in 1947 and 1948.
' First recent year; production less than half average in 1934 and 1942.
< First recent year; production less than half average in 1936.
' Decline interrupted by increases in 1948 (followed by further slight rise
In 1949 in M-1).

• First recent year; abundance below 70-percent level in 1930 and/or 1931.

' Fishing intensity so closely linked with availability of whitefish that
summary would be meaningless and possibly misleading; see p. 83.

• 1941 if irregularities in 1944 and 1946 are ignored.

• Intensity unquestionably would have been less than 50 percent of average
In 1948 but for the abnormal situation in M-1; see p. 83.

DECLINE OF LAKE TROUT IN LAKE MICHIGAN

85

the 9 "high-production" years listed in tabic 8
for the first three districts, 8 were earlier than 1940
(the 1941 production in M-2 provided the only
exception) and 5 earlier than 1935. In districts
M— i through M-8, on the contrary, the highest

yields usually came after 1939. Only 2 of the 15
high-production years listed for the southern dis-
tricts were earlier than 1940 (1932 in M-6 and
M-7) and 10 fell within the brief 4-year period
1941^4.

O

z

3
O

0.

CO

a

<

o
o

375

M-l

/\

300

/ \

' 1

t

1

1

225

// /V\

-^^^V^

A /

ISO

- ^

/ \ / /\

\

—

/ •

^ . ,_^

N

"v

Jx

\ \ / /

75

—

\

^^^;:^^-^-n//--

1 1 1

-J

1 1 1 1 L

— ! 1 1 1 1 1 \ 1 — 1

200

— 100

M
O

<

Ul

>
<

1990

I93S

1940

1945

Z 500

o

o
o

ce
a

400

300

200

100

M-2

200

ti.

o

lil
o

<
I-
z

u

too

1930

1935

1940

1945

FlGtTBE 3. — Production, abundance index, and fishing-intensity index for lake trout in districts M-l and M-2 1929-49.
Solid line = production ; long dashes = abundance index ; short dashes= fishing-intensity index. Scale at left (thousands
of pounds) appUes only to production; scale at right is in terms of 1929-43 mean for each item.

86

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

1600 —

1200 —

eoo

in 400
O

z

O

0.

100

1930

1935

1940

1945

O

<
a:

UJ

>

<

IL
O

in
a

z
<
m

o

200

150 -

100

V. 50 —

Z O

O

I-

o

3 750

o
o
a.

M-4

\
\

-j^

\

1 1 1 1 1

\ 1 1

1

1 1 1 1 1 1 1

200

100

1 930

1935

1940

I94S

eoo

450

300

150

M-5

L

<

200 f-

z
u
u
ce
w
a

100

1930

1935

1940

t94S

Figure 4.— Production, abundance index, and fishing-intensity index for lake trout in districts M-3, M--4, and M-5,
1929-49. Solid line = production; long dashes= abundance index; short dashes=fishmg-intensity index, hcale at
left (thousands of pounds) applies to production only; scale at right is in terms of 1929-43 mean for each item.

DECLINE OF LAKE TROUT IX LAKE MICHIGAN

87

Soo

M-6

1930

1935

19 40

19 45

iOO

U.
O

10

a

X 300

<
in

:d
o

I

200 —

100 —

o

3 600

a

o

M-7

/3

/ .y ^^. Y/ /''\\~~\

1 1 1

1 1 1

r 1 1 r

\
1 f 1 r t 1 1 1

\
\
\
\ \
\ ^
1 N

200 n

100

1930

1935

1940

1945

450 —

300 ^^

ISO —

M-8

A

1 1 1 1 1 1 1 1

. 1 . .

1 1 1 1

\ \
\ \

.1.. 1 ^

200

CM
0>

(1.
O

o
<

o
a:

100

1930

1935

1945

Figure 5. — Production, abundance index, and fishing-intensity index for lake trout in districts M-6, M-7, and M-8,
1929-49. Solid line= production; long dashes = abundance index; short dashes= fishing-intensity index. Scale at left
(thousands of pounds) applies to production only; scale at right is in terms of 1929-43 mean for each item.

88

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Despite the differences between the northern
and southern waters just outlined, all districts
agreed in showing production equal to or greater
than the 1929^3 mean in relatively recent years.
If we ignore the 1948-49 data for M-1, where, as
explained, conditions were abnormal, the situation
can be described by the statement that every
district had average or better production in 1942
or later and in two districts (M-7 and M-8) the
take was still above the mean in 1946.

The districts agreed further in that the onset
of the progressive decline which has caused so
much concern and the drop of production to less
than half the average also were recent. In only
one of the eight districts (M-6) did the recent
progressive decrease get imder way before 1944,
and in the southernmost waters (M-7 and M-8) it
did not start until 1947. With the exception of
M-1 and M-2 (again 1948-49 data are ignored in
the former district) the 50-percent level was not
passed before 1947, and in M-7 and M-8 the
take did not drop below half the mean untU 1948.
These data suggest a distinct north-to-south
trend in the time at which the decline set in.

Despite the lateness of the decline, the speed
with which it progressed was such that by 1949
the lake-trout fishery had practically come to an
end in all districts but M-1. The 1949 total catch
for districts M-2 through M-8 was only 74,000
pounds. These same waters had yielded more
than 3 million pounds as recently as 1941 and in
excess of 2 million pounds as late as 1945. The
decline since the latter year represents a decrease
of 96.7 percent.

The production data for the combined districts
may be summarized as follows: Highest yields
occurred in the early 1940's (1941, 1943, 1940);
1944 was the last year of above-average production
and the first year of the recent decline; the
output fell below 50 percent of the 1929-43
mean for the first time in 1947. Even when data
are included for M-1 where the 1949 take was
above the 1929-43 average, the decrease from
1944 to 1949 amounted to 90.6 percent.

ABUNDANCE IN STATE OF MICHIGAN
WATERS, 1929-49

The estimates of the abundance or availability '
of lake trout in the statistical districts of the State
of Michigan waters of Lake Michigan beginning

Table 9. — Abundance indices for lake trout in Michigan
statistical districts, 1929-49

[Percentages of 1929-43 mean]

Year

Abundance percentage in district—

Aver-

M-1

M-2

M-3

M-4

M-5

M-6

M-7

M-8

age '

1929

71
65
69
80
97
92
87
137
157
112
94
105
138
96
100

53
51
32
26
44
45

84

93

114

112

116

110

112

122

98

95

93

81

104

77

90

69
56
61
33
40
19

99

89
103
106

98
104
104
104

88

86
120

83
116

96
105

84
71
56
36
22
12

80
69
86
88
100
132
134
89
92
99
93
77
119
108
134

105
91
76
63
40
30

88
79
71
78
S3
93
101
93
94
97
102
110
129
126
166

146
126
97
73
60
35

89
79

77

98

107

108

116

76

78

90

102

126

125

108

121

117
113
77
72
73
43

72

79
79
110
94
79
96
76
74
78
91
126
153
161
143

139
132
115
108
89
21

74
81
66
73
88
70
81
78
96
100
101
116
119
179
178

174
166
109
106
84
33

87

1930

83

1931

87

1932

96

1933

97

1934

98

1935

102

1936

97

1937

93

1938 — —

92

1939 ---

105

1940

100

1941

123

1942

114

1943

126

1944

110

1945 — -

98

1946

75

1947

60

1948

60

1949

26

1 In the computation of the averages the abundance index for each district
was weighted by the percentage contribution of that district to the total
catch of all districts over the 15-year period 1929-43.

with 1929 (table 9; see also figs. 3, 4, and 5), are
based principally on the records of the catch per
imit lift of large-mesh gill nets (mesh sizes 4K
inches and greater, extension measure). During
the base period 1929-43, large-mesh gill nets
accounted for 88.1 percent of the total catch of
lake trout. Set hooks were second (8.2 percent),
and poimd nets third (2.2 percent). The catch
of other gears plus a small quantity of lake trout
for which gear records were lacking made up the
remaining 1.5 percent (presentation here of
original data on gear composition of the catch is
not considered necessary). Poimd nets were of
sufficient importance to be included in the estima-
tion of abundance in only three districts (M-1,
M-3, M^).

Records of the catch per unit of fishing effort
of large-mesh gill nets, set hooks, and pound nets
in the several districts in 1929-49 are given
in tables 10, 11, and 12.

In the listing of the years of highest abundance
(middle section of table 8), as was true for the
years of greatest production (top section) , distinct

' Argument about which of the two words should be employed would con-
stitute a futile quibbling over terminology. These estimates are based on
the fishing experience of the fishermen — the records of their catch of legal-sized
lalce trout per standard unit of fishing effort. They offer no uiformation on
the abundance of undersized lalce trout and are affected by such factors as
meteorological conditions, annual differences in the time of spawning in
relation to the fixed dosed season, and annual differences In the distribution
of fish. Yet, for all these obvious wealmesses they offer the best estimates
of abundance to be had at the present time. Accordingly, we do not hesitate
to use "availability" and "abundance" interchangeably.

DECLINE OF LAKE TROUT IN LAKE MICHIGAN

89

Table 10. — Catch of lake trout per lift of large-mesh gill nets
in Michigan statistical districts, 1929-49

[In pounds per li/t of 10,000 linear feet of large-mesh gill nets 4H inches and
greater, extension measure]

Year

District

M-1

M-2

M-3

M-4

M-5

M-6

M-7

M-8

1929

1930

66
67
63
78
106
73
79
168
189
121
96
118
134
91
94

102

50
48
30
24
42
44

126
143
175
171
169
168
166
184
146
142
142
121
161
115
136

151

105
81
78
49
61
28

13!

117
140
143
122
127
136
136
113
113
161
109
155
125
138

131

109
92
73
47
29
16

83
66
90
88
88
153
138
97
92
106
101
80
126
118
143

105

109
92
80
65
42
31

84
77
72
80
86
96
103
94
95
99
103
113
131
127
158

101

147
126
98
73
61
35

98
86
84
107
119
118
127
82
85
98
113
139
137
118
130

109

129
124
84
79
80
47

99
111
139
201
140
126
188
148
143
181
189
276
264
247
234

179

219
212
189
189
143
34

85
108

1931

92

1932

138

1933 -

1934

138
91

1935

1936 — - — -

128
149

1937

163

1938 — - -

177

1939

184

1940

212

1941 .

196

279

1943.

260

1929-^ mean

160

1944 _.

258

1945 --

239

1946

158

1947

150

1948

1949

122
48

Table 12. — Catch of lake trout per lift of pound nets in
Michigan statistical districts, 1929-49

(In pounds per lift of 1 pound net. Where no figures are given, few or no lake
trout were talcen with this gear]

Table 11. — Catch of lake trout per lift of set hooks in
Michigan statistical districts, 1929-49

[In pounds per lift of 1 .000 set hooks. Where no figures are given, few or no
lake trout were taken with this gear]

Year

District

M-1

M-2

M-3

M-4

M-5

M-6

M-7

M-8

1929

223

253
201
151
197
247
237
165
154
129
138
1-29

173
111

187
218
290
198
259
236
215
207
158
190
91

133
143

118
132
229
264
161
182
114
61
111
104
102

137
119
123

94
172
139
147

96
191
131

83
143

73
107

356

247
208
138
165
162
202
275
218
433
117
120

131

108
122
131
72
112
120

"56'

239
194
132
191
201
154
143
117
122
123
153
134
137
173
249

164

346
211

185
74

252

1930 -

194

1931

145

1932

116

19.33

132

1934 . __.

200

1935

162

1936

112

1937

133

19.38

140

1939

161

1940

158

1941

176

1942

102

212

1943

265
121

323

1929-43 mean'

184

190

143

128

140
167

243

174

1944. -

73

1945

1946

208

1947

~i?)"

""(".)"

435

1948 —

""(.)-"

~m"

~m"

65

1949

C)

(»)

' For each district for which data are not given for 1 or more years, the
15-year average is estimated by dividing the mean of the available annual
averages by the mean of the abundance percentages for the same years. See
Van Oosten, Hile, and Jobes (1946) for comments on the estimation of a
normal catch when data are not available for all years.

" No fishing with set hooks in 1949.

diflFerences are to be seen between the northern
and southern areas of the lake. Of the 12 "high-
abundance" years listed for districts M-1 through
M-4,* 9 were earlier than 1940 and only 1 was

» District M-1, assigned to the southern districts in the grouping with
respect to production, has been assigned to the northern with respect to years
of greatest abundance.

Year

District

Year

District

M-1

M-3

M-f

M-1

M-3

M-4

1929

14
15
13
18
16
29
23

8
13
16
12

8

17
16
15
16
25
17
20
17
22
15
11
9

21
27
22
43
47
38
66
24
33
17
13
16

1941

13

12
8
12

16

13
16
10
4

3

1

19

1930

1942

23

1931

1943

2
14
4

18

1932—

1929-43 mean'..

1944

1945

1933

28

1934

1935..

9

1936

1937

1946

10

1938

1947-^ —

9
8
S

2

1939

1948 —

1949

7

1940..

' For each district for which data are not given for 1 or more years, the 15-
year average is estimated by dividing the mean of the available annual aver-
ages by the mean of the abundance percentages for the same years. See
Van Oosten, Hile. and Jobes (1946) for comments on the estimation of a nor-
mal catch when data are not available for all years.

later than 1941. The corresponding record for
districts M-5 through M-8, on the contrary,
shows all 12 years within the period 1940-44
and 9 within the still-shorter interval 1941—43.

Although the recent progi-essive decline in
abundance appears to have started at much the
same time in all districts (1942 in M-7, 1943 in
M-8, and 1944 in all other districts) it proceeded
much more rapidly in northerly than in southerly
waters. The last year with abundance at average
or greater was 1941 in M-2, 1943 m M-1 and M-3,
1944 in M-4, 1945 m M-5 and M-6, and 1947 in
M-7 and M-8. The same north-to-south sequence
exists in the first year in which abimdance dropped
below the 70-percent level,' 1944 in M-1 and
M-2, 1946 in M-3, 1947 in M^, 1948 m M-5,
and 1949 in M-6, M-7, and M-8. This north-
to-south progression resembles closely that de-
scribed for production in the preceding section.
The situation invites speculation about the
possibility that a southward spread of the sea
lamprey was a contributmg factor.

Despite the differences in timing just described,
the districts agreed in that all showed an ex-
tremely low level of availability of lake trout in
1949 (range of abimdance percentages from 45 in
M-1 down to 12 m M-3). Admittedly, the
dependability of the estimates of abundance
decreases rapidly as production falls to low levels.
Nevertheless, the consistently low returns per

• The 70-percent level Is considered preferable here to the 50-percent flgiu^
employed for analogous items In the data for production (and for fishing
hitensity, discussed later). Usually the fishery has all but disappeared by
the time the 60-porcent level of abundance is reached.

90

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

unit of fishing effort together with the very fact
that production had all but ended in most areas
must be accepted as conclusive evidence of the
great scarcity of marketable-sized lake trout in
the State of Michigan waters of Lake Michigan in
1949.

For the combined districts the level of abun-
dance was highest in 1943 (126), 1941, and 1942.
The last year with abundance above average and
the first year of the recent progressive decline
was 1944, and abundance first dropped below the
70-percent level in 1947. In 1949 the abundance
had reached the low figure of 26 percent.

Table 13. — Correlations between 1929-43 fluctuations in
abundance indices for lake trout in Michigan statistical
districts

[Values of r corresponding to probabilities p of 0.05 and 0.01 are ±0.514 and
±0.641]

District

District

M-1

M-2

M-3

M^

M-6

M-6

M-7

M-8

M-1

0.113

'"7370
.181
-.460
-.255
-.374
-.617

-0.040

.370

.404
.181
.233
.201
-.037

0.175
.181
.404

"7587
.591
.394
.365

0.346

-.460

.181

.587

"".m

.786
.889

0.043

-.256

.233

.591

.681

--"767
.526

0.142
-.374
.201
.394
.786
.767

-"165

223

M-2

0.113
-.040
.175
.346
.043
.142
.223

-.617

M-3

-.037

M-4

.365

IM-5

.889

M-6

M-7

M-8

.626
.805

From earlier discussion and from the examina-
tion of table 9 and figures 3, 4, and 5, it is apparent
that in certain districts the annual fluctuations in
the abundance of lake trout followed similar
trends. In the northern waters for example, it
has been pointed out that most of the years of
highest abundance fell before 1940, whereas the
southern districts shared a period of high avail-
ability in the early 1940's. To provide a more
precise measurement of the agreement in these
trends, coefficients of correlation were computed
for the abundance percentages for aU pairs of
districts over the period 1929-43. Data for
yeare later than 1943 were excluded in order to
minimize or possibly eliminate the distorting
effects of the decline in abundance that followed
the depredations of the sea lamprey in all districts.
This restriction, we believe, has made the coeffi-
cients recorded in table 13 relatively reliable
estimates of the correlations between fluctuations
in the availability of lake trout in the difl'erent
districts under approximately "normal" condi-
tions.

The outstanding feature of the data of table
13 is the close positive correlation among the
fluctuations in abundance in the four southern
districts (M-5 thi-ough M-8). Of the sLx coeffi-
cients that could be computed for these districts,
five exceeded the value ordinarily accepted as
"higlily significant" (p<^0.01), and the sixth was
above the level ordinarily termed "significant"
(^<0.05). These high values, together with the
consistency with which they occurred with all
possible pairings, suggest strongly that the lake-
trout fisheries to the south of Grand Traverse
Point were based on a common stock or on stocks
in which the factors controlling abundance in
1929-43 were the same or subject to sunilar
annual fluctuations. Further speculation in the
matter would be to little point until we have
definite information on the nature of these factors
and the methods by which they operate.

The fluctuations of abundance in M-4 exhibited
positive significant correlation with those in the
two districts immediately to the south (M-5
and M-6). The correlation with fluctuations in
M-3 also was positive but the value of the coeffi-
cient (r= 0.404) was well below the level of
significance.

Of the 3 coefficients computed between districts
M-1, M-2, and M-3, and the 15 calculated
between those districts and the ones lying farther
south, only one was significant (r= — 0.617, M-2
and M-8). This single significant value in a
group of 18 faUs to fit the pattern. The weight
of the evidence suggests that the fluctuations in
the abundance of lake trout in each of the three
northern districts were not correlated with those
ia the remaining ones.

FISHING INTENSITY IN STATE OF
MICHIGAN WATERS, 1929-49

The records of the annual fluctuations in the
intensity of the fishery for lake trout (table 14;
figs. 3, 4, and 5; bottom section of table 8) fail
to reveal the distmct separation with respect to
trends that existed between northern and southern
areas in production and abundance. With the
exception of M-2 where all three years and M-8
where two of the three years of most intensive
fishing occurred in the 1940's, the tendency was
general for fishmg operations to be heaviest in the
early 1930's. Of the 21 "high-intensity" years
listed in table 8 (see section on production in the

I

DECLINE OF LAKE TROUT IN LAKE MICHIGAN

91

Table 14.-

-Intensity of fishery for lake trout in Michigan
statistical districts, 1929-49

[In units corresponding to 1/1500 of total eipected catch for all districts over

15-year period 1929-43]

Year

District

Tota

M-1

M-2

M-3

M-4

M-5

M-6

M-7

M-8

19M ..

10.1

7.1

36.8

3.4

11.9

12.7

8.3

9.5

98.8

1930

12.3

9.7

42.9

6.2

14.0

13.3

11.5

13.0

121.9

1931 ..

12.7

10.1

38.3

4.7

17.3

14.6

12.7

9.1

119.6

1932 .

9.6

11.4

32.7

5.2

19.2

14.1

11.5

8.6

112.3

1933

5.4

10.0

27.3

4.1

20.9

11.1

S.9

9.1

96.8

1934

3.1

9.8

25.1

2.2

15.8

10.1

7.5

9.4

83.0

1935

3.4

8.4

28.9

2.6

16.7

10.3

9.5

14.5

94.3

1936

4.6

8.3

30.8

3.3

15.1

7.4

5.8

9.6

84.8

1937... .

5.8

11.8

32.8

3.8

18.6

7.4

6.9

7.3

94.4

1938

8.6

9.9

36.4

4.6

17.4

7.9

7.4

11.8

104.0

1939

6.5

9.8

33.9

4.2

15.6

10.1

8.4

14.3

102.8

1940

3.1

10.6

34.8

6.5

15.1

13.0

8.9

16.5

107.5

1941.

2.1

13.3

30.3

4.6

13.5

12.9

10.6

14.1

101.4

1942

2.3

12.9

28.1

4.8

11.9

10.2

8.8

11.1

90.1

1943

3.6

13.0

31.0

3.6

11.3

8.8

5.8

11.4

88.4

1929-43 mean...

6.2

10.4

32.6

4.1

15.6

10.9

8.9

11.3

100

1944

3.5
2.2
1.4
6.9
15.7

11.0

10.0

6.0

3.0

2.4

31.6
32.8
31.1
23.9
15.8

4.9
4.1
3.5
2.4
1.8

12.3
9.3

10.5
6.8
5.6

8.3

7.8
7.7
3.8
1.0

7.3

7.3
9.9
5.6
1.9

13.1

13.7

21.2

8.7

6.1

91.9

1945

87.2

1946...

91.3

1947

61. 1

1948

50.3

1949

12.8

.7

7.4

1.7

2.4

.4

.4

.7

26.5

various districts for an account of the unusual
situation ia M-1) 12 fell within the 4-year period
1930-33.

The last year of average or greater fishing
intensity was 1939 in M-5, 1941 in M-6, and 1944
to 1946 in the remaining districts. The recent
progressive decline started in 1942 in M-6 and in
1944 to 1947 in other areas. Fishing intensity
first dropped below the 50-percent level in 1947
m M-2, M-5, and M-6, in 1948 in M-3, M^, and
M-7, and m 1949 in M-8.

For the combined districts the intensity of the
lake-trout fishery was greatest in 1930, 1931, and
1932, and the last year of greater-than-average
intensity was 1941. The recent progressive de-
cline started in 1947, and in 1949 fishing intensity
was only 26 percent of the 1929-43 mean.

The factors that influence the intensity of the
fishery for lake trout are so numerous, so variable
in their effects, and so difficult to appraise, that in
most situations it is impossible to evaluate the
effect of any one of them. Among these factors
may be listed: Weather conditions; costs of
operation; availability of and market for lake
trout, for species taken along with lake trout, and
for species produced alternatively. During the
war years scarcities of equipment and supplies
and manpower shortages also affected fishing
intensity.

The availability of the lake trout itself well
might be expected to exert an important influence

on the intensity of fishing since good catches per
unit of effort shoidd stimulate fishing operations
and poor lifts depress them. This expectation
is not borne out, however, by the following
tabulation of the coefficients of correlation between
the abundance of lake trout and fishing intensity
for the species in the various districts in 1929^1 :""

r

District M-1 -0. 611

District M-2 .034

District M-3 -. 378

District M-4 -. 677

r

District M-5 -0. 379

District M-6 . 225

District M-7 .357

District M-8 . 633

Of the eight coefficients calculated, four were
positive and four negative, and of the three that
were "significant" (r= ±0.553 at the 5-percent
level of probability) one was positive and two
negative. It is not to be concluded, of course,
that a plenitude of lake trout is about equaUy
likely to stimulate or depress fishing activity;
rather, it should be stated that in many situations
other factors are of greater importance.

The high negative correlation between fishing
intensity and abundance of lake trout in M-1
has already been explained. The available sta-
tistical data do not suggest an explanation of the
even higher negative figure for M-4. Perhaps
this significant correlation was merely fortuitous.
We are inclined to suspect, however, that the neg-
ative correlation can be attributed in part to
changes of fishing grounds during the time of the
great increase in the popularity of "deep-sea'
troUing for lake trout in Grand Traverse Bay
(identical with M^) in the 1930's. Although we
have no quantitative measure of the effect on the
intensity of the fishery, we do know that certain
fishermen, in an attempt to lessen friction between
sport and commercial interests, avoided the sport-
trolling grounds during the peak of the tourist
season and moved their operations to grounds
north of Grand Traverse Point (M-3) and near
Cathead Point (M-5). Consequently, fishing in-
tensity may have been lower than normafly would
be expected in some years when lake trout were
relatively plentiful.

The significant positive correlation between
fishing intensity and the abundance of lake trout
in M-8 may reflect a true cause-and-effect rela-

'0 The elimination of years after 1911 in these computations makes possible
the best estimate of rel.itions under approximately "normal" conditions since
bias from wartime shortages of manpower and materials and the effects of the
general sharp deline in abundance that accompanied the increase in the
population of sea lampreys in recent years are eliminated or minimized.

92

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

tion, but the lack of a simOar correlation in the
other districts throws some doubt on such an
interpretation.

The general situation in the State of Michigan
waters seems to be much the same as that in the
United States waters of Lake Huron where Hile
(1949) concluded that "indispensable as the lake
trout may be to the conduct of a lake trout
fisheiy, the abundance of that species is only one
of the factors, and in some situations a subordinate
factor, in the determination of fishing intensity."

RELATIONS OF PRODUCTION,
ABUNDANCE, AND FISHING INTENSITY

Considerable infoi-mation on the relations of
production, abundance, and fishing intensity in
the lake-trout fishery of the State of Michigan
waters of Lake Michigan was given in the preced-
ing sections. The discussion of the present sec-
tion is restricted largely to the question of the ex-
tent to which production has served as an indica-
tor of fluctuations in the abundance of lake trout
and to changes in the fishery immediately pre-
ceding and dm-ing the recent collapse, with special
reference to the possible role of overfishing as a
factor in the decline in abmidance of lake trout.

The accumulation of information on the degree
of reliability of production statistics as indicators
of changes in abundance or availability in the
Great Lakes fisheries is of importance because in
many areas data on the actual take per unit of
fishing effort are not available or are at hand for
only the more recent years.

The opinion was expressed by Van Oosten, HUe,
and Jobes (1946) that "imder normal conditions
(without disruption in the methods or regulations
of the fishery), over limited areas, and for short
periods of years, large increases or decreases of
production may serve as reliable indicators of in-
creases or decreases in the abundance of fish on
the grounds." A similar view was held by Doan
(1942) who considered it valid to employ catch
statistics for the estimation of the fluctuation in
the abundance of several commercially important
species in Lake Erie. Doan based his opinion
largely on the agreement between trends in the
catch of walleyes or yellow pikeperch {Stizostedion
V. vitreum) per unit effort in the principal gear and
the total production of the species in four fishing
areas of Lakes Huron and Michigan (data for these

two lakes adapted from Hile 1937) and in Lake
Erie. More recently, Hile (1949) demonstrated a
significant positive correlation between annual
fluctuations in the production and abundance of
lake trout for four of the sLx statistical districts of
the United States waters of Lake Huron and for
the six districts combined. In a fifth area the co-
efhcient was positive with a value corresponding
to the 10-percent level of probabihty, but a sig-
nificant negative value existed in the sixth district.
This negative correlation was explained as the
result of the depressing effect of the collapse of the
whitefish fishery on the intensity of operations with
large-mesh gill nets dui'ing years of relatively high
abundance of lake trout (note the similar situation
described earlier in this paper for district M-1).

Of the coefficients of correlation between the
production and abimdance computed for Lake
Michigan (table 15) those for the period 1929-41
most nearly reflect "normal" conditions. The co-
efficients for the base period 1929-43 were prob-
ably biased by the depressing effects of wartime
scarcities of manpower and equipment and those
for 1929—49 were affected by wartime conditions
and more recently by the general collapse of the
lake-trout fishery.

Table 15. — Correlations between production and abundance
of lake trout in Michigan statistical districts, for 3 periods

Item

Period

1929-41

1929-43

192949

-0. 050
.614
.431
.065
.677
.775
.904
.874
.579

.476
.553
.684

-0.028
.516
.441
.223
.528
.714
.817
.878
.696

.441
.614
.641

0.337

District M-2

.914

District M-3 _.

.937

.712

District M-5

.708

District M-6

.802

District M-7

.802

District M-8

.872

All districts

.918

Value of r at p — 0.10

.369

.433

.549

Actually, the differences between 1929-41 and
1929-43 were unimportant. In both periods the
correlations between production and abimdance
were "highly significant" (p<0.01) for M-6, M-7,
and M-8 and were "significant" (0.05>p>0.01)
for M-2 and M-5 and for the combined districts.
The positive coefficients for M-3 were moderately
high but nevertheless fell short even of the 10-per-
cent value in 1929-41 and barely attained that
level in 1929-^3. The 1929-41 and 1929^3 data

DECLINE OF LAKE TROUT IN LAKE MICHIGAN

93

5.000 F

a

z

o

a
z
<

D
O

X

o
O

3,000 -

2.000 —

1,000 —

1930

1935

1940

1945

Figure 6. — Production, abundance inde.x, and fishing-intensity inde.x for lake trout in combined districts of State of
Michigan waters, 1929-49. Solid line = production; Iohr dashes = abundance index; short dashes = fishing-intensity
index. Scale at left (thousands of pounds) applies to production only; scale at right is in terras of 1929-43 mean for
each item.

offer no evidence for a correlation between the pro-
duction and abundance of lake trout in M-1 and
M-4. A negative correlation between abundance
and fishing intensity in each of the two districts in
1929-^1 (see preceding section) imquestionably
was a major disturbing influence.

From the values of the coefficients for 1929-^1
and/or 1929-43 it appears that production served
as a more or less reliable indicator of at least the
more significant fluctuations of abundance in five
of eight districts and in the lake as a whole, was
of highly limited value in one district and was com-
pletely undependable in two (see figs. 3, 4, 5, and
6). The failm-e of production and abundance to
follow similar courses in M-1 and M-4 (to a con-
siderable extent in M-3 also) brings out the impor-
tance of being constantly alert to identify and, if
possible, evaluate distmbing factors in the use of
production figures for detecting changes in abun-
dance. It should be stressed also that catch statis-
tics should be employed only to detect changes of
abundance and not as measures of those changes.

The coefficients of correlation for 1929-49 had
high positive values — far beyond the level accepted
as higlily significant — in districts M-2 through
M-8 and in the combined districts. District M-1 ,
where abnormally intensive fishing kept produc-
tion high in later years, offered the single excep-
tion. These high values for districts M-2 through
M-8 can be attributed to the enormous declines
in both production and abundance that occiured
in the later years of the period. Too much should
not be made of the high coefficients for 1929-49 as

an argmnent for the value of production statistics
for following trends of availabihtj'. When a
fishery suffers a decline as disastrous as the one
that has overtaken the lake-trout fishery of Lake
Michigan, statistical analyses are hardly required
to prove that fish are too scarce to support com-
mercial operations.

During the years of the decline in the lake-trout
fisheries of Lakes Huron and Michigan we heard
the opinion expressed both privately and publicly
that the sea lamprey had not contributed signifi-
cantly to the collapse, that the stocks of lake trout
simply had dwindled away under the pressure of
overfishing, that the distress of the fishing industry
was but just retribution for a wanton despoliation
of a valuable public resource. The facts given in
an earlier study of the lake-trout fishery of Lake
Huron (Hile 1949) demonstrated rather conclu-
sively that excessive fishing intensity could not
have brought about the collapse of the fisheiy in
the United States waters of that lake. Corre-
sponding data for the State of Michigan portion
of Lake Michigan compel a similar conclusion for
the lake-trout fishery of those waters.

The data of table 16 (see also fig. 6) fail com-
pletely to show a level of fishing intensity that
would account for the recent decline in the lake-
trout fishery of Lake Michigan. On the contrary,
the most intensive fishing operations of the 21-year
period, 1929^9, occurred m 1930-32 (112 to 122
percent of the 1929-43 mean — figures that do not
indicate excessive fishing even at that time)
whereas in the later years fishing intensity has

94

FISHERY BtTLLETESr OF THE FISH AND WILDLIFE SERVICE

Table 16. — Indices of production, abundance, and fishing
intensity for lake trout in Slate of Michigan waters, 1929-49

[Percentages of 1929-43 means]

Year

Produc-

Abun-

Inten-

Year

Produc-

Abun-

Inten-

tion

dance

sity

tion

dance

sity

1929 __

86

87

99

1940

109

100

108

1930 -

101

83

122

1941

126

123

101

1931

104

87

120

1942

104

114

90

1932

108

96

112

1943

111

126

88

1933 -

94

97

97

1944

103

110

92

1934

81

98

83

1945

88

98

87

1935

96

102

94

1946

75

75

91

1936

84

97

85

1947

36

60

61

1937

89

93

94

1948

23

50

50

1938

98

92

104

1949

9

26

26

1939

109

105

103

been invariably below the 100-percent value since
1941. It is particularly significant that intensity
was below average in 3 of the 4 years of highest
abundance (1941-44) and was barely above the
15-year mean in the fourth. These same years
saw production consistently above the mean and
at a 21 -year peak in 1941, but a high level of
abundance, not intensive fishing, was the cause.
Furthermore, the intensity percentage exceeded
the abundance percentage in only 2 of the 9 years
of the period 1941-49; in the remaining 7 years
the two index figures were the same or fishing in-
tensity was the lower. It is thus obvious that a
rate of fishing that could bring the index of
abimdance from a record high figure of 126 in

1943 to a record low value of 26 in 1949 simply
did not exist. Some factor other than overfishing
caused the lake trout to disappear in Lakes Huron
and Michigan. The best evidence points to the

sea lamprey.

SUMMARY

After a developmental period from 1879 through
1889, the fishery for lake trout, Salvelinus [=Cris-
tivomer] namaycush, in Lake Michigan entered on
a 22-year period (1890-1911) of high and rela-
tively stable production. The average annual
output for this latter interval was 8,230,000
pounds. There followed two shorter intervals of
15 years (1912-26) and 13 years (1927-39) in
which the annual yields were still moderately
stable but had successively lower average values
of 7,007,000 and 5,293,000 pounds. Production
rose in 1940 but the heightened prosperity was
short-lived. After 5 years (1940-44) in which the
yield was consistently more than 6 million pounds
and averaged 6,578,000 pounds, the lake-trout
fishery suffered a calamitous decline which saw
the annual catch drop from 6,498,000 pounds in

1944 to only 342,000 pounds in 1949.

Michigan and Wisconsin have always contrib-
uted the bulk of the production of lake trout in
Lake Michigan. The contribution of Michigan
for the periods listed in the preceding paragraph
(excluding the developmental years for which only
scattered data were available) ranged from 42.4
percent in 1890-1911 to 45.7 percent in 1927-39.
In Wisconsin the range was from 41.4 percent in
1940-44 to 54.8 percent in 1890-1911. The per-
centages have been consistently small for Indiana
(maximimi of 3.1 percent in 1912-26) and were
smaU for Illinois also in the earlier years. More
recently Illinois contributed 14.7 percent of the
total for the lake in 1940-44 and 11.3 percent in
1945^9.

Comparison of the aimual yields of lake trout
in the eight statistical districts of the State of
Michigan waters of Lake Michigan in 1891-1908
with those of 1929-43 (the base period for our
modern statistical analyses) revealed a lower
level of productivity in more recent years for
every district but M-5 and a slight southward
shifting of the centers of production (the north-
erly districts M-1 through M-3 contributed
60.3 percent of the 1891-1908 total but only
49.1 percent of the 1929-43 yield). The ranking
of the districts with respect to their percentage
contribution to the lake total changed little,
however.

Production statistics for the individual dis-
tricts in 1929-49 showed that most of the years
of relatively high production (the three best
years for each district) fell before 1940 in north-
erly waters (M-1 through M-3) and after 1940
in southerly waters (M-4 through M-8). Al-
though the recent progressive decline in produc-
tion got under way earlier than 1944 in only one
district and started as late as 1947 in M-7 and
M-8, the catch had dropped to an insignificantly
low level in all districts by 1949 (an exception
must be made for M-1 where considerable quan-
tities of lake trout were taken coincid en tally in
an abnormally intensive fishery for whitefish).

Records of the three years of greatest abun-
dance or availability of lake trout (as computed
from the data on the catch per unit of fishing
eft'ort of the principal gears) revealed that most of
these years fell before 1940 in districts M-1
through M-4, whereas in the waters to the south
(M-5 through M-8) they all fell within the period
1940^4. Figures on the last year with abun-

DECLINE OF LAKE TROUT IN LAKE MICHIGAN

95

dance at or above the 1929^3 index of 100 and
on the first year of abundance below 70 (a level
of availability selected as critical in this study)
give strong indication of a north-to-south pro-
gression in the timing of the recent decline (wTth
the more northerly districts the first to drop below
average and to pass the 70-percent level). This
sequence suggests that the different areas may
have been affected successively as the sea lamprey
spread from the north to the south. Despite this
progression, all eight districts agreed in exlii biting
an extremely low level of abundance in 1949 (from
12 to 45 percent of average in the individual
districts; 26 percent for the combined districts).

During the more nearly normal years preceding
the recent general decline of the lake-trout fishery,
the annual fluctuations in the abundance of lake
trout in the four southern districts (M-5 through
M-8) were closely correlated. The coefficient of
correlation r was highly significant (p<C0.01) for
five of six possible pairings over the period 1929-43
and was significant (p<0.05) for the sixth. The
fluctuations of abundance in M-4 also were coiTe-
lated significantly with those in M-5 and M-6.
The abimdance in each of the northern districts,
on the contraiy, appeared to be independent of
that in any other area.

In the majority of the statistical districts the
years of most intensive fishing for lake trout fell
in the early 1930's and for the combined districts
the three years of greatest fishing intensity were
1930, 1931, and 1932. With the exception of M-1,
where a recent upswing in the intensity of fishing
for whitefish led to an increased pressiu-e on lake
trout, fishing intensity for the latter species en-
tered on a progressive decline as early as 1942 and
in no district later than 1947. By 1949, fishing
intensity was far below 50 percent of the 1929^3
average in aU districts but M-1 and amoimted to
only 26.5 percent for the eight districts combined.
The abundance of lake trout seems to have had
little influence on the intensity of the fishery under
the nomial conditions of 1929-41 (before World
War II with its shortages of manpower and equip-
ment and well before the general decline of the
lake-trout fishery associated with the spread of
the sea lamprey) .

Dming the same normal 1929^1 period, fluc-
tuations in production served as reasonably de-
pendable indicators of major changes in abundance
in five of the eight districts. These changes in

production did not, however, provide rehable
measures of the extent of the fluctuations in
abundance.

Statistics on the production and abundance of
lake ti'out and on the intensity of the lake-trout
fishery refute the view sometimes advanced that
overfishing has been the cause of the decline of
the lake trout in the State of Alicliigan waters of
Lake Michigan. The most intensive fishing of
the 1929-49 period took place in 1930-32, and
intensity has been consistently below the 1929-43
average since 1941. Some factor other than over-
fisliing caused the lake trout to disappear. The
best evidence points to the sea lamprey.

LITERATURE CITED

Do.\N, Kenneth H.

1942. Some meteorological and limnological
conditions as factors in the abundance of
certain fishes in Lake Erie. Ecol. Mon.,
vol. 12, pp. 293-314.

Gallagher, Hubert R., and John Van Oosten.

1943. Supplemental report of the United
States members of the International Board
of Inquiry for the Great Lakes Fisheries.
International Board of Inquiry for the
Great Lakes Fisheries — Report and Sup-
plement, pp. 25-213.

HiLE, Ralph.

1937. The increase in the abundance of the
yeUow pike-perch, Stizostedion vitreum (Mit-
chill), in Lakes Huron and Michigan, in
relation to the artificial propagation of the
species. Trans. Amer. Fish. Soc, vol.
66 (1936), pp. 143-159.

1949. Trends in the lake trout fishery of
Lake Huron through 1946. Trans. Amer.
Fish. Soc, vol. 76 (1946), pp. 121-147.
Hile, Ralph, and Frank W. Jobes.

1941. Age, growth, and production of the

yeUow perch, Perca flavescens (Mitchill),

of Saginaw Bay. Trans. Amer. Fish. Soc,

vol. 70 (1940), pp. 102-122.

Van Oosten, John, Ralph Hile, and Frank W.

Jobes.

1946. The whitefish fishery of Lakes Huron
and Michigan with special reference to the
deep-trap-nct fisheiy. Fisheiy Bull., U. S.
Fish and Wildlife Service, vol. 50, pp.
295-394.

O

UNITED STATES DEPARTMENT OF THE INTERIOR, Oscar L. Chapman, Secretary
FISH AND WILDLIFE SERVICE, Albert M. Day, Director

I

CHARACTERISTICS OF SPAWNING NESTS
OF COLUMBIA RIVER SALMON

\

By Clifford J. Burner

FISHERY BULLETIN 61

From Fishery Bulletin of the Fi*h and Wildlife Service

VOLUME 52

UNITED STATES GOVERNMENT PRINTING OFFICE

WASHINGTON

1951

For sale by the Superintendent of Documents, U. S. Government Printing Office, Washington 25, D. C.

Price 20 cents

CONTENTS

Page

General life history 97

Criteria of a mature redd 97

Measurements and methods 100

Chinook salmon 102

Spring Chinook 102

Summer chinook 103

Fall ciiinook 103

Silver salmon 106

Chum salmon 106

Blueback salmon 107

Redd size and interredd space 107

Summary 110

Literature cited 110

CHARACTERISTICS OF SPAWNING NESTS OF COLUMBIA

RIVER SALMON

By Clifford J. Burner, Fishery Research Biologist

GENERAL LIFE HISTORY

Construction of Grand Coulee Dam across the
main stem of the Columbia River raised a serious
problem concerning the salmon that spawned in
the upper reaches of the river and produced an
important part of the west-coast catch. Grand
Coulee was to be a high dam, with a tailrace-
forebay difference of about 350 feet. Although it
was possible to provide reasonably safe passage
upstream past the dam for the adult salmon, the
cost would be extremely high. Of greater im-
portance was the probability that the salmon
fingerlings on their way to the sea would be killed
in passing down the spillway or through the tur-
bines. It was decided, therefore, to relocate the
salmon rims that spawned above the Grand Coulee
site in four tributary systems entering the Colum-
bia River below that site. The Wenatchee, En-
tiat, Methow, and Okanogan Rivers were selected
to receive the transplanted salmon.

One of the manj' questions in connection with
the relocation was how many salmon should be
placed in each stream or section of stream to get
the maximum yield of spawn and frj'. To answer
this question, a study was made of the spawn-
ing habits of four species of Pacific salmon of
the genus Oncorhynchus. These are the chinook
(0. tschawytscha) , the silver (0. kisutch), the chum
{0. keta) , and the blueback {0. nerka) . This study
was concerned particularly with the type of
stream bottom that a given species uses for spawn-
ing, and the space occupied by a pair of spawning
fish for the nest, or redd. The study included
redds of salmon spawning naturally in some of the
lower Columbia River tributaries and redds of
transplanted spawners in the foster rivers. The
information obtained was used in planning and
carrying out the maintenance project (Fish and
Hanavan 1948) but was not published.

At this time, in view of the program for the
development of the lower Columbia River tribu-
taries in the interest of salmon production, it
seems worth while to set forth the results of the
study so that they may be available for reference.

All species of Pacific salmon are anadromous,
that is, the adults migrate from the ocean into
fresh-water streams to spawn. They proceed up
rivers, such as the Columbia, until they arrive at
the same tributary where they themselves began
life some years before. Verj' few stray to other
streams. The female salmon deposits her eggs
in a nest, or redd, which she digs in the gravel of
the stream or shallow lake-shore waters. In the
process of egg laj-ing, the fertilized ova are covered
with successive layers of gravel to a depth of
several inches. The time required for the eggs to
hatch depends on the temperature of the water.
Newly hatched fish live in the gravel of the redd
and gradually absorb the food in the abdominal
yolk sac. At the end of this period, usually in the
late winter or early spring, they struggle up through
the gravel and begin to seek food. How long the
young fish stay in fresh water varies considerably
with the species, but eventually they migrate
downstream to the sea, where they remain from 1
to 3 years and grow rapidly. When they approach
sexual maturity, they return to fresh water to
spawn and thereby complete the cycle. All
Pacific salmon die after spawning.

CRITERIA OF A MATURE REDD

At the outset of this study, it was necessary to
determine at which stage of development a redd
should be measured. Redd building may be
divided into three stages, prespawning, spawning,
and postspawning. During the prespawning stage,
the female salmon is green, that is, the eggs are
neither ripe nor loose in the ovaries. Males are
seldom in attendance, and are frightened away by
the female, who repels all intruders of either sex.
The female digs the redd as she turns on either
side, at an angle of about 45° to the current, head
upstream, body arched, and makes a series of
violent flexions with body and tail. (See fig. 1.)
The tail strikes the gravel occasionally and the
strong-boiling current created carries gravel and

97

aistM O - il

98

FISHERY BULLETIN OF FISH AND WILDLIFE SERVICE

I /oor'

Figure 1. — Redd making. Female digging.

Figure 2. — Typical currents in a redd.

silt a short distance downstream. This material
spreads out in a flat semicircle at first; then, as the
digging upstream proceeds, it collects into a loose
pile called the tailspill. With more digging, the
redd assumes a long oval shape about twice the
length of the salmon and several inches deep.
The prespawning digging of the redd may go on
for as many as 5 days.

At the beginning of the spawning stage, the nest
is ready for the eggs. All loose gravel and fine
material have been removed from the pot, or
center of the redd, whose shape is such that any
current in the bottom flows upstream (see fig. 2),
then upward and outward. Usually there remain
in the pot large stones too heavy for the fish to
move far, and the crevices between these rocks
provide excellent lodgment for the eggs. Males

are constantly present now. The female alter-
nately digs at the redd and settles back into the
depression to release eggs. A male then moves
quickly alongside the resting female, as in figure 3,
curves his body against hers, and releases sperm
in a small milky cloud that settles briefly in the
bottom of the redd where the eggs are lodged.
The newly deposited eggs are thus surrounded by
sperm and eventually fertilized. Excess sperm is
carried slightly upstream along the bottom of the
redd and gradually carried away by the current.
During the spawning stage the redd increases
considerably in length and depth, and appears to
move upstream as a result of the continued digging
at the upstream wall and the filling in of the tail-
spill area.

The postspawning stage begins after the female

CHARACTERISTICS OF SPAWNING NESTS OF COLUMBIA RIVER SALMON

99

o::5-^cD-^cU^

o

r

Figure 3.-

-A pair of spawning salmon on a redd.

100

FISHERY BULLETIN OF FISH AND WILDLIFE SERVICE

finishes depositing her eggs. Males are no longer
attentive. The female is gaunt and spent, but
she continues to dig at the gravel with ever-
weakening efforts until she dies. This post-
spawning digging, which may continue for 10
days, becomes shallow, ofiF-center, and ineffective.
The area of the nest is increased without (after
the first day at least) adding to the protection of
the eggs.

In view of these facts, a mature redd is con-
sidered one in which all egg-laying activities have
been concluded, and some postspawning digging
has been accomplished.

Several criteria were used to determine whether
an observed redd was matiu-e: (1) The gaunt and
spent appearance of a lone female salmon still
digging — considered the most reliable criterion;
(2) the infrequency of the mating act, which
becomes sporadic as the supply of eggs is ex-
hausted; and (3) the presence of freshly covered
eggs in a redd unoccupied by salmon. Most of
the redds measured during the study met the first
criterion. For redds observed daily, the second
criterion indicated near maturity. Some blue-
back-salmon redds in which no fish were present
were considered mature on the basis of the third
criterion.

MEASUREMENTS AND METHODS

Size of the redds was determined by wading into
the stream and taking the length, depth, and
several width measurements. The outline of the
redd was sketched to scale on engineer's notebook
paper, with all pronounced irregularities drawn in.
Later, in the laboratory, a planimeter was used to
compute the area. The entire excavated portion
of the redd back to the tailspill's highest point was
included in the measurement. The prespawning-
digging area, usually located directly under the
crown of the tailspill, was thereby included. The
long tapering downstream slope of the tailspill was
not considered an essential part of the nest meas-
urement, for several reasons: Live eggs were rarely
found there; the velocity of the current would
carry fine sand and lighter silt considerable dis-
tances, resulting in elongation of the slope; and
often the downstream slope of the tailspill of one
redd would be disrupted by salmon making redds
immediately below it. Such tailspill encroachment

never proceeded far enough to endanger the eggs
laid in the neighboring redd.

Depth measm-ements were taken from the sur-
face of the water at 1-foot intervals starting at
stream bed at the upstream edge of the redd,
down the central axis, through the deepest portion,
and over the tailspill. A cross section at the
greatest depth of the redd was taken in similar
fashion from the stream bed on one side to the
stream bed on the other.

The gravel composition for each redd was
arrived at by estimating the amount of large,
medium, and small gravel that had been exposed.
The term "large" gravel is used to describe stones
more than 6 inches in diameter, but not necessarily
round. "Medium" applies to stones from 6 inches
down to 3 inches. "Small" applies to those less
than 3 inches, but larger than heavy sand.

Stream velocities were taken by clocking a bit
of drift over a measured course. The currents and
other flow conditions in a redd were determined
with an aqueous solution of potassium permanga-
nate.

The times of the salmons' first entry into the
streams, the times of first redd digging and of
peak of spawning, average stream and redd depths,
and water velocities and temperatures are shown
in the table.

Except in small, sparsely populated creeks, no
attempt was made to measure all the redds in a
stream. In rivers thickly covered with redds
throughout their length, only representative
sections were observed, but all the redds in Such
sections were measured, in order to avoid selection.
In these sections each redd was marked by driving
a stake at the downstream slope of the tailspill, or
by placing a number on a tree opposite the redd.
The stakes facilitated observation, from day to
day, of the redd-digging progress of an individual
salmon. Figure 4 is a diagram of a redd that was
marked on the first day of digging and measured
daily thereafter. In this diagram, it will be seen
that redd digging extended from September 20
to October 8. The sign of Venus (9) below the
line indicates the female, present each day the
redd was measured. The sign of Mars (cf) above
the line shows for each day the number of male
salmon actively attending and fighting for the
privilege of fertilization.

CHARACTERISTICS OF SPAWNING NESTS OF COLUMBIA RIVER SALMOX

101

Summary of information gathered on spawning of salmon in selected streams

CfflNOOK SALMON

SavRR

Chum

SALMON

Blueback salmon

Spring run

Summer run

Fall run

SALMON

In low-

in
Toutle
River
(1938)

er-Co-
lumbia

tribu-
taries 1

(1938)

White
River
(1939)

Little
We-
natchee
River
(1939)

We-

natchee
River

(1939)

Okan-
ogan
River

(1939)

Ohana-
pecosh
River
(1938)

Nason
Creek
(1939)

Entiat
River
(1939)

We-

natchee

River

(1939)

White
River
(1939)

Kalama
River
(1938)

Toutle
River
(1938)

Spawning schedule:

(■)
Aug. 20

(>)
Aug. 21

(>)
Sept. 7

(•)
Sept. 8

(>)
Sept. 23

Sept. 9
Sept. 20

(>)
Sept. 27

(')
(>)

(•)
(■)

(•)
Oct. 11

(')
Sept. 17

(»)
Oct. 2

(1)

First redd digging...

(S)

Peak of spawning

Aug. 28

Aug. 31

(')

Sept. 20

(')

Sept. 30

(')

Oct. 22

Nov. 22

Oct. 20

Oct. 12

Oct. 8

(1)

Spawning ended . ...

Sept. 10

Sept. 15

Nov. 15

Oct. 25

Oct. 15

(»)

Nov. 2

(')

(')

(>)

Nov. 4

Oct. 31

Nov. 15

Depth of stream: '

Average (mean)

._ .inches..

14

8.6

16

13

10

14

11.6

7.8

10

11.5

12

13

9

Minimum

do....

2

3

7

4

6

3

3

2

2

3

2

5

4

Maximum

do....

36

18

26

30

16

48

24

26

30

37

24

28

17

Depth of redds: •

Average (mean)

do....

9

8.5

10

9.7

9.3

10

10.7

8

8 5

5.5

5.7

4.2

5

Minimum

do....

3

4

4

4

5

2

4

3

3

3

3

2

2

Maximum

do....

20

14

19

18

14

17

18

20

17

9

n

8

9

Velocity of water:

Average (mean)

.cubic feet a second..

(>)

2

1.5

2

1.7

2

1.3

5''

(«)

1.6

1.7

1.8

1.7

Minimum

do....

(')

.5

1

1

1.4

1

1

(")

(■)

1

1

1.7

1.5

Maximum

do....

(')

3.5

2

3

2

3.5

3

(')

(')

1.8

1.9

2

2

Temperature (Fahrenheit) ot water:

Minimum

degrees..

51

47

40

55

47

52

42

42

40

44

48

54

47

Maximum

do....

53

52

55

62

51

61

58

S8

44

49

51

55

48

' Germany Creek, Abemethy Creek, Elokomin River, and Grays River.

' No data.

• Transplanted.

< Indefinite.

* Average measurements taken from surface to stream bed at each side
and at upstream, end of each redd.

• Depth below stream bed, taken at deepest part of redd.

/y<7/f ^«*/

^i&si^

Lono/'/'uc/ino/ tJec//

V — ioeo//on one/ compara^/ife a/ouft^on.e* or <
iJea/«

^ ^/«/

Figure 4. — Diagrammatic views of a fall chinook salmon redd measured daily.

102

FISHERY BULLETIN OF FISH AND WILDLIFE SERVICE

CHINOOK SALMON

The chinook salmon is native to the Pacific
coast from California to Alaska. Some runs ex-
tend from Bering Strait to the southern Siberian
coast. By transplantation of fertilized eggs, runs
have been established in the St. Lawrence River
and in certain parts of New Zealand. The
Columbia River supports the largest population of
the species.

In the Columbia River, most of the chinook
salmon migrate upstream from March through
September. The migration is divided into three
more or less distinct classes, and the fish are
referred to as spring-run, summer-run, and fall-run
chinooks, according to the time they leave the
ocean and start on their upstream journey. The
smaller spring chinooks, which average about 15
pounds in weight, ascend the Columbia River
system for considerable distances and spawn in
headwaters from mid-July to mid-September.
The larger summer chinooks do not go as far
upstream as the spring chinooks, and the time of
spawning is later, from September to mid-No-
vember. The fall chinooks spawn chiefly in the
lower Columbia River tributaries and in the main
stems of the Columbia and Snake Rivers at about
the same time as the summer chinooks, and the
two classes are comparable in size. The summer
chinooks have an average weight of about 30
pounds, and the fall chinooks average 20 to 25
pounds.

The following three sections describe and com-
pare the size and other characteristics of the
redds made by spring, summer, and fall chinook
salmon, in several tributaries of the Columbia
River.

SPRING CHINOOK

Investigation of spring chinook salmon redds
was made in the Ohanapecosh River, a tributary
of the Cowlitz River (which is a lower-Columbia
tributary), and in Nason Creek, a tributary of
the Wenatchee River. The Ohanapecosh has a
natural run of spring chinook salmon, whereas the
Nason was one of the streams into which fish were
transplanted during the Grand Coulee fish-
maintenance project.

The average redd size and gravel composition
of these two streams may be compared in figure 5o,
circles A and B. The Ohanapecosh, a mountain
stream, contained a high proportion of large

rubble about the size of a football. Because of the
large-gravel component, the Ohanapecosh redds
were considerably smaller (2.9 square yards) than
Nason Creek redds (4.9 square yards). The
Ohanapecosh redds contained an average of 59
percent medium and small gravel, whereas the
Nason Creek redds averaged 86 percent medium
and small.

Spawning times, stream depths at the redds,
depths of redds, and water velocities and tempera-
tures for the spring-chinook redds in the two
streams are given in the table.

SUMMER CHINOOK

The spawning of summer chinook salmon was
studied in the Entiat River, the Wenatchee River,
and the White River tributary of Wenatchee Lake.
These are streams selected as foster rivers for some
thousands of the chinook salmon blocked by Grand
Coulee Dam. The spawning redds measured were
made by the transplanted salmon, trapped at
Rock Island Dam near Wenatchee, Wash., in July,
August, September, and October. Because of the
similarity of summer-run to fall-run chinook sal-
mon in all but time of migration, I have combined
the measurements of the summer-chinook redds
with those of fall-chinook redds in the size fre-
quency graph, figure 7.

For the 41 redds measured in the Entiat, the
average size was 7.8 square yards. A comparison
of the Entiat average, figure 5a, circle C, with the
average nest areas for summer and fall chinooks
from other streams shows that the Entiat River
redds were distinctly larger than those in other
streams. The Entiat River contains an abundance
of medium and small rubble which facilitated redd
construction and resulted in large redds. The
degree of cementation was less in the Entiat than
in the Kalama River or the Toutle River (where
fall-chinook redds were studied) and probably con-
tributed to the ease of digging. Subsurface per-
colation was greater, and this is a factor that
governs the location of redds to a greater extent
than is generally recognized.

It was noted that most spawning took place on
gravel through which there was a flow of water.
The flow was detected by releasing potassium-
permanganate solution in test holes in the stream
beds. There were areas in the Entiat River and
in nearly all streams examined, apparently unex-
celled for redd building and where trial redds were

CHARACTERISTICS OF SPAWNING NESTS OF COLUMBIA RIVER SALMON

103

visible, that were deserted by salmon for no other
ascertainable reason than that there was little or
no flow of water through the gravel. Gravel
firmly cemented with silt and clay binders usually
lacked a percolating flow and was avoided by
Entiat River chinooks and by salmon in other
streams. All species showed a decided preference
for moderately bound stream-bed materials in
place of either loose shingle (free-rolling gravel) or
firmly bound rubble.

Nearly all spawning of summer chinook salmon
in the White River took place in areas of the stream
that contained 95 percent medium and small
gravel. As shown in figure 5a, circle D, 9 redds
were measured and the average nest area was 4.7
square yards. Although this appears to contradict
the inverse-ratio relation between gravel size and
redd area, it is not considered significant, in view
of the small number of redds measured. As its
name implies, the White River is clouded by quan-
tities of chalky glacial material during the summer
and fall run-off, and this made observations diffi-
cult.

The redds studied in the Entiat, Wenatchee, and
White Rivers were made by salmon transplanted
to each spawning area over a long period of time.
Relocation was spaced out in order to keep the
sexes evenly distributed in each area. As a result,
there was a mixture of stocks, or races, of summer
chinook on the same spawning areas, and a wide
assortment of sizes of redds resulted. Although the
summer chinook are a little larger, as a class, than
the fall chinook, their redds contained about the
same proportion of large, medium, and small
gravel as fall-chinook redds. Figure 5a, circle E,
shows that average redd size and gravel composi-
tion, for summer chinook in the Wenatchee River
are comparable to the redd sizes and gravel com-
positions for fall chinook in the Toutle River sys-
tem, figure 5o, circles G and H.

FALL CHINOOK

The Kalama River, the Toutle River, and the
Green River tributary of the Toutle, were selected
for study of fall chinook salmon redds. The
Toutle River is a tributary of the lower Columbia
through the Cowlitz River; the Cowlitz and the
Kalama enter the Columbia only a few miles
apart, about 60 miles from the sea. Thus, they
are neighboring streams and they have somewhat
similar watersheds — both are moderately forested

and have fair gradients — but here the resemblance
ends. Because of an insurmountable falls, the
Kalama River has only 7 miles of available spawn-
ing area, containing a high proportion of large
gravel. Most of the stream bed is of stratified
gravel, that is, stream-bed disturbances and sub-
sequent flooding have overlaid the large gravel
with successive layers of smaller stones. During
redd digging the salmon encountered the sub-
stratum of large rocks with the result that the
redds resemble oversize underwater Easter egg
baskets. The Kalama River fall-chinook redds
contained a higher proportion of large gravel
than did other fall-chinook redds. (See fig. 5a,
circle F.)

The Toutle River and its Green River tributary
are both accessible through virtually all their
lengths, presenting 40 miles or more of stream bed
with a greater choice of spawning rubble than is
available to the Kalama River fall chinooks.
The areas used contained gravel of relatively
uniform size with little or no stratification.
Whereas the Kalama River redds averaged 5.7
square yards with 41 percent large gravel, the
Toutle River redds averaged 6.5 square yards
with 11 percent large gravel.

It would appear, from examination of figure
5a, circles F, G, and H, and figure 6, that the
abundance of large gravel in the Kalama had the
effect of reducing the size of the fall-chinook redds
there as compared with fall-chinook redds in the
Toutle River and its Green River tributary.
The slightly smaller average for the size of the
Green River redds, figure 5a, circle G, may be
attributable to the fact that fewer redds were
measured; figure 6 shows that the modal size of
the Green River redds is greater than that of the
Kalama River redds. These differences might be
explained on the basis of the mechanics of redd
building: the large gravel in the Kalama was
difficult to dislodge and to move, so the resulting
redds were smaller, whereas the medium gravel of
the Toutle River was easier to dig in and produced
larger redds.

SILVER SALMON

Silver salmon are distributed throughout the
North Pacific from mid-California to Alaska and
in Asiatic waters as far south as Japan. The
greatest runs are found in the streams of Oregon,
Washington, British Columbia, and southeastern

104

FISHERY BULLETIN OF FISH AND WILDLIFE SERVICE

s5/>r/fT^ CA/ftooA

/Yason Cf.

4.9 ayt^a, 90 /-*Ma

0/?c

^h /?.

lonapeco^t

2.9 aye/sj 9^ f^Ms

Sufftftrar C/f/'/rooA

7.8 ayt/s, 4/ ree/efs

4:7 aye/j, 9 /••</</«
fa// Ch/nook

tc/enatcJtee A.
S. 9 Oy</s , 8S /'et/efa

Ko/ama /?. Creen /?. Toufle R.

S.7 aytA, /■^J r-eeA/j S.^ OyA , 2 7 /-ce^s 6.S aytA^ BS ^at/t/s

Figure 5o. — Average size and gravel composition of Columbia River salmon redds.

CHARACTERISTICS OF SPAWNING NESTS OF COLUMBIA RIVER SALMON

J- 1 Chum

//ver

105

7ou//e /?.

Loo/er Co/umoia Tribi.
Z.7 aye/jj 66 /-ee/t/s

S/uejback

2. uuds J J/ rec/i/s

/.8 ay*/i , 3/ redt/s

Okanoyan /i.

^arqe orave/ -mors //ton O <//a/t7.
/^ecZ/um and Sma// - 6 or /esi

Figure 56. — Average size and gravel composition of Columbia River salmon redds.

106

FISHERY BULLETIN OF FISH AND WILDLIFE SERVICE

Alaska. At maturity they average about 9K
pounds in weight and about 24 inches in length.

In the upper Toutle and Green River tribu-
taries of the Columbia, the silver salmon occupied
many of the same spawning areas as the fall
chinooks, and the two species were found spawn-
ing at the same time.

In general, the sUver salmon apparently prefered
small streams flowing only 3 or 4 cubic feet a
second and were present in a number of localities
not occupied by the chinook salmon. A compari-
son of the nesting habits of the two species was
obtained at a point where the Toutle River is
divided by a large bar into a broad and a narrow
channel. The small, 3-foot-wide watercourse was
populated exclusively by silver salmon. The
wider run, nearly 60 feet across, contained only
fall-chinook salmon. In the shallower upper
reaches of the Green River tributary, the two
species spawned virtually side by side.

The silver salmon demonstrated a redd-building
versatility that was not equalled by other species.
In the small Beaver Creek tributary of the Green
River, a stream of less than 2 cubic feet a second,
the bottom was composed of flat chunks of slate-
shale rubble that defied classification by the usual
gravel standards. The silvers were paired off
and spawning in stream-width redds that were end
to end for a distance of nearly 2 miles. In the
Toutle River, immediately below Spirit Lake,
silver-salmon redds assumed bizarre shapes, both
in surface outline and in bottom contour, as the
fish dug around embedded boulders and fallen
trees. This was the only salmon of the four
species whose redds contained up to 10 percent
mud. The gravel composition of silver-salmon
redds is shown in figure 56 and the size frequency
of the redds is shown in figure 7.

CHUM SALMON

Chum salmon are found in rivers of the Pacific
coast from Oregon to the Arctic Ocean and in
streams of the northern Japanese islands. In the
Columbia River these salmon spawn mainly in
the small tributaries only a short distance from
the sea. They average 26 inches in length and
weigh about 10 pounds at maturity.

The streams selected for a study of chum-
salmon spawning, Germany Creek, Abernethy
Creek, Elokomin River, and Grays River, are
tributaries of the lower Columbia River and only

a few miles apart. The chum salmon did not
migrate far upstream, and in Abernethy Creek
some spawned in tidal water so that the redds were
uncovered and dry at the surface during a part of
each day. Several of the redds were examined
when exposed, and live ova were found in the
damp gravel of the nest. At high water, these
redds were occupied by spawners, but it was not
determined whether they were the original
occupants.

Chum salmon were also found spawning in
water just deep enough to cover the lateral line of
the fish. When distm-bed they would dash out
of the water onto the banks and flop back into the
stream. In thickly populated sections, the redds
were ill-defined and overlapped from end to end
and laterally. The riffles contained hundreds of
opaque dead eggs and a few lives ones. Because
of the abundance of spawners and the overlapping
of nests, it was necessary to select redds for study
on the basis of their individuality of outline and
apparent maturity. These salmon were more
easily frightened than the other species so that it
was difficult to determine whether the females
were in continuous possession of their redds. In
a few instances it was definitely determined that
the same females occupied their nests for at least
3 days.

Of 66 chum-salmon redds measured, the average
size was 2.7 square yards (fig. 5b, circle J). The
proportions of large, medium, and small gravel
were similar to the proportions for most of the
other species. Chum salmon, even more than
other species, avoided firmly cemented gravel
bottom and spawned in sections of moderately
bound rubble where subgravel flow or percolation
was evident.

BLUEBACK SALMON

Blueback salmon is the name applied to the
species 0. nerka within the Columbia River System
and a few neighboring streams. In Puget Sound
and British Columbia they are called sockeye,
and in Alaska, red salmon. In the Columbia
River, blueback salmon average 3 pounds in
weight and 20 inches in length.

The blueback salmon differs from all the other
species in that the spawning redds, with few
exceptions, are made only in streams tributary
to lakes or along lake shores. The young salmon,
on emerging from the gravel of the nest, descend

CHARACTERISTICS OF SPAWNING NESTS OF COLUMBIA RIVER SALMON

107

without delay to the lake and live there at least a
year before migrating seaward.

Blueback-salmon redds are perfect models of
the nests made by larger salmon of other species.
The extent of the redd and the size of the gravel
chosen are scaled down to the size of the blueback.
The number of redds measured, the average size,
and the gravel composition are shown in figure
56, circles K, L, M, and N. The gravel composi-
tion was 90 percent or more of medium and small
size, with the small gravel (about the size of a
golf ball) predominating. The stream-tjrpe blue-
back redd contained a small pot of larger stones
to receive the eggs, had a loose tailspill, and was
oval. The lake-type redd in the shallows near
shore in Osoyoos Lake (Okanogan River water-
shed) was larger and of irregular shape; because
there was no current, the female would dig all
around the edge of the nest. As there were rela-
tively few of the lake-type redds, none were
measured.

REDD SIZE AND INTERREDD SPACE

In general, for all species of salmon the size of
the redds varies in direct proportion to the size
of the salmon comprising the run, and in inverse
proportion to the size and cementation of the
gravel in the stream. The redds made in slow
water are larger and more circular in outline, but
as a rule are not as deep as those made in rapid
water where the hydraulic force helps move the
gravel.

On crowded spawning gravels of riffles and
rapid runs, some chinook redds overlapped slightly
end-to-end because the long tailspill of one redd
would be disturbed by the female working
directly downstream from it. Only a few redds
overlapped laterally. As a matter of fact, few
redds of any species were made exactly side by
side, but occasionally the redds would form diag-
onal rows across the streams. For the most
part, the female chinook salmon was vigorously
averse to the presence of another female im-
mediately upstream from her nest, or one digging
directly at the side of her nest, until her own redd
was well under way.

The natural tendency of the female salmon
to guard the privacy of the redd area made for
fairly regular spacing. The more or less sym-
metrical oval shape of most nests was an addi-
tional space factor. The salmon redds in a

crowded stream area do not fit into each other
like the parts of a jigsaw puzzle, but have spaces
between them nearly as great as, or greater than,
the areas of the nests themselves. This interredd
space varies with the species and also with such
physical factors as population pressure, composi-
tion and gradient of stream bottom, and water
velocity. The ratio of interredd space to redd
size appeared to be less for chum salmon and
silver salmon than for the other species studied.
The contiguous and in some cases superimposed
construction of chum-salmon redds may have
been the result of overpopulation of the limited
spawning areas available in the streams examined.
Population pressure noticeably decreased the
interredd space of silver salmon in Beaver Creek
at the upper limit of spawning, where the stream
was wide enough for only one or two redds.

In the Kalama River, the large rubble made
for smaller redds, but interredd spacing was
about the same as elsewhere — presumably because
the nest radius to be defended remained the same
for chinook salmon of a given size. In quiet-water
areas, both redd size and interredd spacing were
proportionately greater than the redd size and
interredd spacing in stretches of rapid water
where the stream bed had considerable gradient.
In rapid water, the spawning salmon were busier
with redd digging, so that fewer "dog-fights"
occurred. Their distribution on the spawning
gravels was more or less uniform, resembling the
typical spawning-stream population of moderate
riffles.

In general it was noted for chinook salmon that,
wherever sufficient spawners were present to
utilize virtuaUy all the usable gravel, the interredd
space amounted to nearly three times the area
occupied by the redds. Thus, the total average
area necessary for a pair of spawning fish was
about four times the area of the average redd. For
other species, the space factor was somewhat less
than that for chinook salmon. It is believed,
however, that to arrive at a conservative figure
for the number of pairs of salmon that can satis-
factorily utilize a given area of gravel suitable
for spawning, the area should be divided by four
times the average size of the redds. Thus, a
pair of spawning summer or fall chinook salmon
would require approximately 24 square yards of
suitable gravel; spring chinook salmon, 16 square
yards; silver salmon, 14 square yards; chum

108

FISHERY BULLETIN OF FISH AND WILDLIFE SERVICE

IS

10

•^

WENATCHEE R.

autrttrtcf t^cfft

WHITE R. jummef /►«/>»

10

40

O

a 5
ui

E NT I AT R. summef /-t/f?

O
m
w

TOUTLE R.

Af// fc/^

GREEN R.

/i//

20

IS

10

KALAMA R.

2 3 4 S 6 7 8 9 10 II 12 13 14 IS 16 17 18 19 20

SIZE OF REDDS IN SQUARE YARDS

Figure 6. — Size frequency distribution of summer and fall chinook redds.

CHARACTERISTICS OF SPAWNING NESTS OF COLUMBIA RIVER SALMON

109

70

60

50

40

30

20

10

20

10

BLUEBACK

141 REDDS

CHUH

66 REDDS

(A

O

I

SILVER

65 REDDS

8 9

II 12 13 14 19 16 17 18 19 20

SIZE OF REDDS IN SQUARE YARDS
Figure 7. — Size frequency distribution of salmon redds from all streams combined.

no

FISHERY BULLETIN OF FISH AND WILDLIFE SERVICE

salmon, 11 square yards; and blueback salmon,
8 square yards.

SUMMARY

1. Observations were made on a large number
of chinook, silver, chum, and blueback salmon
redds in the Columbia River watershed, and 850
redds were measured.

2. Normally, the female salmon constructs the
redd, the male taking no part in this activity.

3. The redd is formed or excavated by the
female turning on her side and making violent
flexions of the body and tail. The boiling currents
set up by this action disturb the gravel of the
stream bed which is carried a short distance
downstream to form the tailspill.

4. A typical redd is an excavation in the stream
bottom, oval in shape, the greatest diameter being
lengthwise with the current, and with a tailspill
at the downstream end. The center of the redd
is referred to as the pot, and it is here that the
bulk of the eggs is deposited.

5. Current velocities at spawning areas varied
from less than 1 foot a second to 3.5 feet a second.
Redds made in fast water were invariably long
and narrow; those in quiet water had a broad
oval shape.

6. The current in the pot of the redd flows
slightly upstream, which favors safe deposition
of the eggs in the gravel and is conducive to
complete fertilization by the milt of the male
salmon.

7. As the spawning progresses, the redd in a
sense moves upstream by continued excavation of
the upstream edge and filling in of the tailspill

area.

8. In general, salmon chose areas of stream bed

composed of gravel less than 6 inches in greatest

diameter, with the size of the redd inversely pro-
portioned to the size of gravel. Firmly cemented
gravel was avoided, though where there was some
cementation, the size of the redd was inversely
proportioned to the amount of cementation.

9. Percolation of water through the gravel
appears to be a requisite of the redd site.

10. In general, salmon prefer areas of stream
bottom relatively free of mud or silt for redd-
making purposes. Silvers (0. kisutch) were the
only salmon of the four species which constructed
redds in areas of stream bottom containing up to
10 percent mud.

11. Average redd size for the various salmon is
as follows: Summer and fall chinook, 6.1 square
yards; spring chinook, 3.9 square yards; silver,
3.4 square yards; chum, 2.7 square yards, and
blueback, 2.1 square yards.

12. Few redds of any species were made side
by side. For the most part, nests were either up
or down stream from each other so that they
woidd form diagonal rows across the stream.

13. The tendency of female salmon to prevent
other females from getting too close resulted in
interredd space approximately three times the
size of the redd.

14. By dividing the area suitable for spawning
in a given stream by four times the average redd
area, a conservative estimate will be obtained of
the number of salmon that may satisfactorily
spawn in the stream.

LITERATURE CITED

Fish, Frederic F., and Mitchell G. Hanavan.

1948. A report upon the Grand Coulee fish-maintenance
project 1939-1947. U. S. Fish and Wildlife Service,
Special Sci. Rept. No. 55.

o

UNITED STATES DEPARTMENT OF THE INTERIOR, Oscar L. Chapman, Secretary
FISH AND WILDLIFE SERVICE, Albert M. Day, Director

CONTRIBUTIONS TO THE

BIOLOGY OF TUNAS FROM THE

WESTERN EQUATORIAL PACIFIC

By Bell M. Shimada

FISHERY BULLETIN 62

From Fishery Bulletin of the Fish and Wildlife Service

VOLUME 52

UNITED STATES GOVERNMENT PRINTING OFFICE • WASHINGTON : 1951

For sale by the Superintendent of Documents, U. S. Government Printing Ofifice, Washington 25, D. C. Price 15 cents

CONTENTS

Page

Collection of data 111

Notes on tuna spawning li;i

Yellowiin (Neothunnus macropierus) ^ 113

Big-eyed tuna (Parathunnus sibi) 114

Records of juvenile oceanic skipjack (Katsuwonus pelamis) 116

Occurrence of bluefin tuna ( Thunnus orienialis) 117

Siunmaiy 118

Literature cited 118

CONTRIBUTIONS TO THE BIOLOGY OF TUNAS FROM THE
WESTERN EQUATORIAL PACIFIC

By Bell M. Shimada, Fishery Research Biolosist

Kesearcli into the biolojiy of Pacific tunas has
advanced rajiidly in recent years, yet much re-
mains unknown about the life history and habits
of tuna species inhabiting waters of the former
Man(hited Islands now known as the Pacific Trust
Territories, in the western equatorial Pacific
Ocean. In prewar years, some scientific studies
were conducted by the Japanese, but these were
limited in scope and directed primarily towards
exploitation of the extensive tuna resources to be
found near their island possessions.

With the opening of the Trust Territories on
May 11, 1950, to Japanese mothership-type tuna-
fisliing operations, an opportunity was given the
Pacific Oceanic Fishery Investigations of the
United States Fish and AVildlife Service to gather
important data on tunas of this region by send-
ing a scientific and technical observer along with
the first mothership expedition to leave Japan.
I was subsequently detailed aboard the mother-
ship Tenyo Maru No. 2 and accompanied the expe-
dition from June 12 to September 14. 1950. Dur-
ing this assignment my principal duties were to
observe Japanese methods of fishing and process-
ing tuna, and to collect morphometric data on
various tuna species for use by the Pacific Oceanic
Fisliery Investigations in current studies on Pa-
cific tuna populations. Some information was
obtained also on other biological aspects of tunas.
These incidental observations on the spawning of
yellowfin and big-eyed tuna, on the occurrence of
juvenile oceanic skipjack, and on the capture of
adult bluefin tuna in the area covered by the expe-
dition are summarized in this report.

Tliese studies were made possible througii the
cooperation of the High Commissioner for the
Trust Territoi-ies of the Pacific Islands and the
Natural Resources Section, General Headquar-
ters, Supreme Commander for the Allied Powers.
The assistance rendered by various membcis of
the Japanese Fishery Agency and the Taiyo Fisli-
ing Co., Ltd., aboard the mothership is also
acknowledged.

953180°— 51

COLLECTION OF DATA

The expedition, consisting of a mothership and
25 iongline-fishing vessels, commenced its activi-
ties in the vicinity of 4°35' north latitude and
143°32' east longitude on June 17, 1950. As the
season progressed, the center of fishing gi-adually
shifted eastward at a rate of about 100 nautical
miles a week, the changes in position of the vessels
being dictated largely by the success of fishing in
any one area. The deployment of fishing vessels
in a north-and-south direction was bounded by 1°
and 9° north latitude, but in general fishing was
mostly between 1° and 5° north latitude, for it
was here that the best catches were made. Wlien
operations were terminated on September 5, 1950,
the mothership's position was 8° north latitude,
15r)°46' east longitude, whence it returned to
Japan. The easternmost limit reached by the
catcher boats was 160° east longitude. In all, the
expedition fished an area of approximately 305,-
000 square miles from wliich it took over 4,055
tons of tunas, spearfishes, sharks, and other fishes
(table 1).

Table 1. — Total catch, by species, of Japanese tuna mother-
ship expedition, J une-Se.ptember 1950

Species

Catch 1

YoUowfin tuiiLi {Neothunnus macropterus)

Pounds

4.574,358

699,014

65,378

3,430

6,968

1,760.389

48.182

1,229

Big-evod tuna (PaTafbimmts sihi) .

Bluefin tuna (TItunmi.s orienialis)

Skipjack iKatsntioiins peJnmis)

While marlin (Maknini nttiTlina)

Striped marlin (^t'lknirn milsukurii)

Sailfish • (Isfinptionis oritfttalis) _

28,160

13,656

895, 022

23,048

Swordflsh (Xiphiaa gladius)

Shark

Others i

Total

8.118,834

1 Statistics provided by the Japanese Fishery Agency and converted to
pounds using conversion factor of 8.27 lbs.=l kan,

- Includes short-nosed marlin (Tetraplurus breriroslris).

3 Includes barracuda (Sphyraena argeiUea), wahoo (Acanthocvbium solaTidri),
and doliihin {CoTuphaena liippurus).

A few tunas wex'e caught by pole and line at tiie
surface, but gear employed chiefly was the long-
line. This type of gear was developed to a great

111

112

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

20
10

__ JUNE

N = 70

1

—

I

,UJ

Jmli^

la

10

_ JU
N>

LY

186

Jy

U

dl

k

k ,

—

I
<n

•^ 60

u.

o

_ AU

N =

GUST

= 821

—

q:

UJ

00 60

s

—

1

—

40

■^

I

"

30

—

80

1

—

10

o

HUU

mi

Olu

dil

i

1

^1

60

60

70

140

ISO

160

80 90 too 110 120 130

TOTAL LENGTH IN CENTIMETERS

FroTTBE I. — Length frequencies (if yellowlin tuna measured aboard the ujothership Temjo Maru No. 2. June-August 1950.

extent by the Japanese and is highly effective for
fishing subsurface levels for tunas and otlier com-
mercially valuable fishes otherwise unavailable to
fishermen. Although variations in the construc-
tion of gear and minor differences in operating
technique existed among the manj' fishing vessels
of the expedition, the louglines were built and
handled essentially in the same manner by all ves-
sel'; A good description of Japanese longline

gear and fishing methods is given by Shapiro
^(1950).

The principal species of fish landed was the yel-
lowlin tuna {NeotJiunnus macropterus) w^hich
comprised more than 50 percent of the total catch
bj^ v\eight and ninnber. Yellowfin tuna, because
of their export value, were delivei'ed to the mother-
ship as whole fish for freezing, whereas other
species were usually gutted at sea. Those yellow-

TUNAS FROM WESTERN EQUATORIAL PACIFIC

113

fin not suitable for freezing in the round because
of size or condition were butchered for filleting.
Such fish were examined whenever possible for
sexual maturity and food habits.

The big-eyed tuna {Parathunnus sibi) appeai-ed
less frequently in the catches than yellowfin tuna
but ranked second in percentage composition of
tuna landings by weight and number. Approxi-
mately S50 tons of this species were received by
the mothership. Biological observations were
made on big-eyed tuna similar to those for the
yellowfin.

NOTES ON TUNA SPAWNING

Yellowfin (Neothunniis macropterus)

Previous studies on the gonads of yellowfin tuna
have been largely confined to smaller fish, less than
a meter in length, usually captured by surface-
trolling gear (Schaefer and Marr 1948a, Wade
1950a). Schaefer and Marr's work (1948a) on
the spawning of yellowfin tuna in Central Amer-
ican waters included large fish, but even so, repre-
sentative samples from catches made by bait boats
and purse seinere were composed predominately
of fish measuring less than a meter. It is ap-
parent, therefore, that fishing gear designed to
fish at or near the surface catches smaller and
younger fish than subsurface gear and for this
reason does not supply material that gives infor-
mation on the maturation of older fish.

The longline, on the other hand, captures larger
fish. This is evident from figure 1 which shows
the plotted length-frequency data for yellowtin
tuna taken randomly from longline catches during
the season. Length frequencies of fish of less than
80 cm. include not only those caught by longlines
but also fish taken at the surface by pole-and-line
gear.

Although the proportion of males was usxuiUy
greater than that of females among yellowfin tuna
examined, the sex ratio sometimes running as high
as 80 males to 20 females in samples drawn from
landed catches, no effort was made to analyze the
condition of male gonads for it is extremely diffi-
cult, if not impossible, to make a reliable estimate
of the state of maturity by gross examination.
Milt was found in the central lumen of practically
all testes examined, even in those which, fi'om all
appearances, woidd be classified either as spent or
as ripening.

Female yellowfin tuna occurred more frequently
among fish below 130 cm. in length than among the
larger size groups, but in no case was it observed
that the proportion of females exceeded that of
males.

Ovaries of the fish examined were found to be
inmiature, ripening, or in spent condition, by
Marr's criteria (Schaefer and Man*, 1948a) of
gonad classification. Since the yellowfin tuna
probably spawns several batches of eggs over an
extended period of time, as suggested by Schaefer
and Marr (1948a), the ovaries possibly do not im-
mediately become much reduced in size after
spawning. A long-extended spawning season,
with individuals spawning more than once, would
result in an ovary ripening over a long period.
For these reasons, it is difficult, as others have
found, to distinguish between spawning and
ripening ovaries. The tabulated results of gonad
observations, table 2, probably include both of
these categories under the classification of "ripen-
ing."

No ovaries that could be considered ripe or run-
ning ripe were found. The absence from catches
of individuals ready to spawn has been noted
wherever studies have been made on the spawning
habits of yellowfin tuna. Sdiaefer and Marr
(1948a) observed no running ripe females and hy-
pothesized that, as spawning approaches, the fish
either migrate beyond the range of the fisliery or
stop feeding. In the Philippine Islands, Wade
(1950a) found ripe yellowfin in the course of his
investigations but no spawning or spent individ-
uals. Apparently this phenomenon is not limited
to the yellowfin tuna, for it has been observed for
big-eyed tuna (Parathunnus sihi), as noted later,
and for oceanic skipjack {Katsuwonus pelamis)
(Hataietal. 1941),

During early August, yellowfin females with
spent ovaries started to appear among catches
made 150 to 200 miles east and northeast of
Kapingamarangi Island (1°05' N., 154°45' E.).
Some such ovaries, flabby in a^ipearance and dark
red in color, might also have been observed in late
July if a check had been made then of incoming
fish. Spent ovaries were observed up to the time
fishing operations ceased in September.

From these superficial observations of gonads,
it was conjectured that the yellowfin tuna to the
east of Kapingamarangi Island had spawned in

114

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Table 2. — Sexual maturity of female yellowjin tuna caught
in the western equatorial Pacific, June-August 1950

Approximate locality

Date

Approxi-

of capture

Total

Sexual

mate date
of capture

length

maturity

examined

Latitude

Longitude

MiUi-

meters

June 25

June 22

3-20' N.

Hl'.IS' E.

1,269 1

Ripening.

Do

do

3''20' N.

141°53' E.

1,285

Do.

Do-

do

3°20' N.

141''53' E.

1,269

Do.

Do-

do

3°20' N.

141°53' E.

1,379

Do.

Do

do

3°20' N.

Nl'.W E.

1,416

Do.

Do

do

3°20' N.

141°53' E.

1,230

Do.

June 26

do

2">51' N.
2°2,5' N.

142°07' E.
143°27' E.

1,485
1,427

Do.

June 30

June 26

Do.

July 2

June 27

I°51' N.

14.'i°43' E.

1,294

Do.

July 6

July 2 -

2°06' N.

14.'i''46' E.

1,324

Do.

Do-

do

2°06' N.

145°46' E.

857

Immature (or
spent?)

Do

do

2°06' N.

145°46' E.

884

Do.

Do

do

2°n5' N.

142°10' E.

1,142

Ripening.

Do

do

2''05' N.

142°10' E.

1,413

Do.

Do

do

2<'05' N.
2'>05' N.

142°10' E.
142" 10' E.

1,189
1,144

Do.

Do

do

Do.

Do

do

2''05' N.
2"'n5' N.

142°10' E.
142° 10' E.

1.064
1,256

Do.

Do

do

Do.

Do

do

2°05' N.

142°10' E.

1,032

Do.

Do

do -

2°05' N.

142° 10' E.

1,120

Do.

Do

do

2°05' N.

142°10' E.

1,232

Do.

Do

do -

2°n5' N.

142°10' E.

1, 243

Do.

Julys

July 3-

rsT' N.

144°05' E.

1.189

Do.

Do

do

rsT' N.

144°n.')' E.

1,446

Do

Do -

do

r37' N.

144°05' E.

893

Do.

July 9- -

Julys

2'>12' N.

149°25' E.

1.418

Do.

Do

do

2''12' N.

149°25' E.

1.353

Do.

Do

do

2<'12' N.

149°25' E.

1.347

Do. .—

Do

do

2''12' N.

149°25' E.

1.257

Do

Do

do

2°12'N.
2n2' N.

149°2.r E.
149°2.V E.

1.181
638

Do.

Do

do

Immature.

Do

do

2'>12' N.

149°2.V E.

673

Do.

Do

do

1''49' N.

149°08' E.

1,367

Ripening

Do

do

1°49' N.
1°49' N.

149°n8' E.
149°08' E.

1.222
1,249

Do.

Do

do -

Do. .---

Do

do -

1''49' N.
1°49' N.

149°08' E.
149°08' E.

1.364
1.281

Do.

Do

do -

Do.

Do

do

1°49' N.
1049' N.
1°49' N.
4°25' N.

149°08' E.
149°n8' E.
149°08' E.
150°.58' E.

1.303
1.256
1.344
1.420

Do.

Do

do

Do.

Do

-.-. do

Bo.

July 13

July 9

Do.

Do

...do

4°25' N.
I°18' N.

160°58' E.
155°30' E.

1,408
1,428

Do.

Aug. 3

July 29

Do.

Do

do

I-IS' N.

165°30' E.

1,390

Do.

Do

do

1°18' N.

155°30' E.

1,154

Do.

Do

do

1°18' N.

155°30' E.

1,203

Do.

Do

do

1°18' N.

156°30' E.

1.3.50

Do.

Do

do

ri8' N.

155''.30' E.

1,279

Do.

Do

do

1°18' N.

155°30' E.

1,233

Spent.

Do

do

1°18' N.

155°30' E.

857

Immature (or
spent?).

Do

do

1°18' N.

156°3D' E.

881

Do.

Do

do

1°18' N.

15.'i°30' E.

1,212

Spent.

Do

do

1°18'N.

l.W°30' E.

1,471

Ripening.

Do

do

I^IS' N.

155°30' E.

1,316

Do.

Do-^..-

do

\°\»' N.

15.'i°.3fl' E.

1,312

Do.

Do

do

1°18' N.

155°30' E.

1.343

Do.

AUB. 4-_

July 31

1°10' N.

l.")7°29' E.

1.395

Do.

Do

do-

1°10' N.

157°29' E.

1,498

Do.

Do

do

rio' N.

I.'i7°29' E.

1,213

Do.

Do -

do

PlC N.

157°29' E.

1, 465

Spent.

Do

do

1°10' N.

157°29' E.

1,365

Do.

Do

do

1°10' N.

157°29' E.

1,307

Ripening.

Do

do

1°10' N.

167°29' E.

1,277

Do.

Aug. 20

Aug. 15---.

3°35' N.

1S6°4.5' E.

l.,302

Do.

Do

do

3''35' N.

155°46' E.

1, 275

Do.

Aug. 29

Aug. 26.-..

2°22' N.

156°34' E.

1,092

Spent.

Do

do

2'=22' N.

156°34' E.

1,250

Do.

Note.— Y. Yabuta of the Nankai Fisheries Experiment Station, Tokyo,
Japan, assisted in making part of these observations.

July with active spawning commencing in June
and extending into August. Further hypothe-
sizing that a common yellowfin population had
been fished during the season — and there appears
to be no evidence to the contrary — it does not seem
unreasonable to believe that spawning had oc-

curred coiiuidentally throughout the area fished.
The spawning season is most likely a long one and
may not necessarih' be limited to the summer
months, but the peak of spawning probably is at-
tained during that period.

Yellowfin tuna found elsewhere in the tropical
western Pacific Ocean are generally believed to
spawn most actively during the summer months.
Preliminaiy studies by biologists of the Pacific
Oceanic Fishery Investigations indicate that dur-
ing 1950 this species spawned in the vicinity of
the Hawaiian Islands from early June to Septem-
ber. Ill the eastern Pacific, however, the spawn-
ing season is considered to be during the late
winter and early spring months (Schaefer and
Marr 1948a). This variation in time of spawn-
ing may be connected to some extent with latitude,
or it may be a race-connected characteristic. Dif-
ferences in spawning times of different races of
the same species in the same or similar places have
been observed in other species of fish, such as the
Pacific surf smelt (Schaefer 1936) and European
herring (Lissner 1934).

Big-eyed tuna (Parathunnus sibi)

Since big-eyed tuna were usually eviscerated at
sea, as previously mentioned, I was not able to
examine many reproductive organs of this species.
No check was made of the maturity of male fish,
but some females that were brought in whole were
opened and examined throughout the fishing sea-
son from late June to early September. These
females possessed either ripening or ripe ovaries,
with a few having what could be considered ad-
vanced-ripe ovaries. No running-ripe or fully
spent ovaries were found. Ovaries classified as
ripening may have been in a spawning state, be-
cause the big-eyed tuna, like the yellowfin, prob-
ably spawns over an extended period with succes-
sive batches of eggs being ripened and extiTided.

Ovaries that appeared ripe were gi'eatly en-
larged, round in cross section, and light pink in
color. Those approacliing the running-ripe stage
had translucent ova whicli were ready to emerge
from the follicles. A sample of 1,000 eggs from
such an ovary removed from a 1,102-mm. female
showed a modal group of large eggs centering
around 1.06 mm. in diameter (fig. 2) . The largest
eggs measured approximately 1.22 mm. The eggs
probably increase a little more in size as water is
absorbed after emission into the sea.

TTJNAS FROM WESTERN EQUATORIAL PACIFIC

-r 1 r I

115

.10 .20 .30 .40 .50 .60 .70 .80 90 l£>0 1. 10 1.20

DIAMETER IN MILLIMETERS
PiGURK 2. — Frequency histogram of ova diameters for a sample of 1,000 Parathunnus siW eggs.

116

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICK

From these observations of gonads it may be
inferred that the big-eyed tuna also spawns in the
area south of the Caroline Islands. Partial veri-
fication of the existence of spawning grounds in
these waters is furnished by Marukawa (Hatai
et al. 1941), who reported at a gathering of
Japanese scientists convened to discuss tuna and
skipjack spawning that "Juveniles of big-eyed
tuna measui'ing 4.2 to 4.3 inches were found inside
yellowfin tuna taken by longlines in the Tokobei
area (Tobi Island, 3° N., 131°31' E.) last year,
while I was in Palau, by a ship of the Fisheries
Experiment Station.'" No mention is made,
how6ver,'of the date of capture. Despite cai-eful
search, juveniles of big-eyed tuna were not found
in the many stomachs of yellowfin tuna and other
jjelagic fishes examined aboard the mothership.

Little is known of the spawning season of the
big-eyed tuna; observations, however, suggest
that it spawns from June to September, and pos-
sibly later. The possibility is not excluded that
spawning may be a year-round phenomenon.

RECORDS OF JUVENILE OCEANIC
SKIPJACK (KATSUWONUS PELAMIS)

While examining stomachs of fish landed
aboard the mothership, I recovered and preserved
in formalin seven juvenile scombroids later iden-
tified as oceanic skipjack, Katsuwonus -pelamis.
One specimen, measuring 130 mm. from the snout
to the end of the hypural plate, was found on
July 21, 1950, in the stomach of a black marlin
{Makaira masara) caught a few days previously
in the vicinity of 1°30' N., 154°08' E. Two addi-
tional juveniles of 132 mm. and 169 mm. were re-
covered on July 24, 1950, from a sailfish {Istio-
phoms orientalis) captured by longlines near
2°28' N., 155°01' E. The remaining four speci-
mens, measuring 81 nnn., 94 mm., 132 mm., and
148 mm., were found in stomachs of yellowfin
tuna {Neothunnus macroptemis) , the smaller two
on August 4, 1950, and the larger two on August
8, 1950. The earlier catches of yellowfin tuna
were made at approximately 1°10' N., 157°29' E.,
and the later catches at 1°14' N., 157°28' E. Re-
mains of fish up to 250 mm. in size and identified
by skeletal characteristics as oceanic skipjack
were found in tunas and other pelagic fish but
were not retained because of their poor condition.

All of the listed juveniles except the »i-iiii«i.
fish were X-rayed in the laboratories of the Pa-
cific Oceanic Fishery Investigations in Honolulu,
Hawaii. On negatives taken of these juvenile
scombroids the skeletal "trellis"' of Kishinouye
(1923) (="basketwork" of Godsil and Byers
(1944)) was faintly visible in every case and
placed these fish within Kishinouye's family
Katsuwonidae. The Katsuwonidae include two
genera : Euthynnus, which is composed of species
having either 37 or 39 vertebrae (Kishinouye 1923,
Schaefer and Marr 1948b), and Katsuvjonun,
which contains a single species characterized by
41 vertebrae (Kishinouye 1923). There is no
knowledge of an overlap in vertebral counts be-
tween genera. The total count of 41 vertebrae,
including the urostyle, therefore, specifically iden-
tified these juveniles as Katsuwonus pelamis
Linnaeus.

For further verification, the 81-mm. juvenile
was stained, using HoUister's method (1934).
There are 41 vertebrae present with 20 precaudal
and 21 caudal vertebrae. The lateral processes on
the precaudal vertebrae are well developed and
the inferior foramina form a "trellis" with the
haemal arches. The haemal canal is large, and
the first closed haemal arch is on the twelfth ver-
tebra. The gill-raker count for the first gill arch
on the left side, which is 15 for the upper arch
and 38 for the lower, falls within the range of
counts given for adults — 15 to 20 and 36 to 38,
respectively (Kishinouye 1923). Palatine teeth
are present ; vomerine teeth are absent. Vestigial
palatine teeth were observed on the 94-mm. speci-
men and were absent on the next larger juvenile
of 130 mm., so that palatine teeth disappear at
a length somewhere between these two.

The presence of juvenile oceanic skipjack in
stomachs of fish caught throughout the area fished
by vessels of the expedition points to the existence
of extensive spawning grounds in or adjacent to
these waters. The only previous published record
of juvenile skipjack from this general locality is
that of Inanami (1942). Since this reference is
not generally available, my translation of his paper
is given here in full :

When I went to Truk in June of this year, I was shown
siiecimens of small skipjack at the Nanko Fishei'ies Com-
pany. Of tlie two, one specimen measuring over 6 sun
(180 mm.) was unmistakably a skipjack juvenile; the
other, measuring 1.5 »un (45 mm.) in length, may have

TUNAS FROM WESTERN EQUATORIAL PACIFIC

117

been a juvenile skipjack,
ered for these specimens :

The following data were gath- Table 3.

-Bluefin tuna captured in the western equatorial
Pacific, June-September 1960

Date of capture

June 17.
June 26.
Julys,.
July 12.
July 14.
July 19.
July 26.
Aug. 10
Aug. 12
Sept. 4.

Locality of capture

Latitude

4°20' N.
4''30' N.
2°39' N.
4''0»' N.
3°48' N.
5°02' N.
2''25' N.
4°00' N.
4n5' N.
2°2S' N.

I/ODgitude

145''ao' E.
145°10' E.
148'>40' E.
147''57' E.
147<'55' E.
154-16' E.
155<'49' E.
157''30' E.
Mift'W E.
155''49' E.

(1) Dimensions: Length, 6.6 sun (198 mm.); weight

2r. mo«(»ie (94 grams). Fish No
Date of capture : 1700, April 23, 1939.

Place of capture : 4 nautical miles southwest of

Sarasbinm Pass (Salat Pass, 7'14' N., 152''01' E.). i

Method of capture : Pole fishing. 3"1!11II1III1I

At the same time, a specimen which could have been *

placed in a rice bowl and assumed to have been 6

about 3 snn (90 mm.) in length was caught but not gllilllllllllll

retained owing to the carelessness of a crew ';-

member.

(2) Dimensions: Length, 1.5 sun (4."i mm.); weight,

2moinme (8 grams). .species was caucfht this year indicates a possible

Date of capture: May 3, 1940. , • j- . ' • •., j- ^ -u x-

n, - . , , »■ , •, ^. ,.. , • change in tactors {loveniinsr its distribution or

Place of capture: 14 nautical miles oft Sarashima * . . . "^ g.

Pagg availabihty in the western equatorial region.

Method of capture : Recovered from the stomach of a Examination of available published logs covering

skipjack which apiiarentiy had been caught im- the prewar activities of Japanese tuna-fishing ves-

mediately after feeding, for there was no evidence gg]g j,^ ^^^ p^i.^^,^ Mariana, and Caroline Islands

failed to show bluefin tuna in their catches. With

It is said that small fish weighing 25 momme (94 grams) ^he exception of Abe's listing (1939) from the

are extremely rare around Truk, but that fish of this size t> , t i i j n,n . -i ,-i? i

„ ,, , n 1 1 • <- c „* r^alau Islands oi a 240-mm. specimen identined

are often seen around Palau during certain sea.sons of ^ ^ _ _

some years. ^^ Tfainmts thynnus{ = Thimmis onentcdis'i) , gis

Altliough oceanic skipjack are known to be
abundant in the vicinity of the many islands and
reefs of the western equatorial region, this species
apparently is not landbound, for several schools
were seen and fished far from land during the
operations of the expedition. Spawning prob-
ably takes place in the open ocean, as well as near
land, as inferred from the recovery of juveniles in
fresh condition from fish caught in deep offshore
waters. Judging from the sizes of young slcip-
jack found, some spawning must occur during the
spring months. Kishinouye (1924) estimates that
young skipjack grow at a rate of more than 40 mm.
a month. Calculations based on this growth rate
suggest that juveniles recovered aboard the moth-
ership in Julj' were spawned in March and April,
and those found later, in April, May, and June.

OCCURRENCE OF BLUEFIN TUNA
(THUNNUS ORIENTALIS)

The bluefin tunas are generally regarded as
temperate-zone foi-ms and are seldom found in
tropical waters. The capture of 10 large tunas
identified as bluefin or black tuna, probably Thwn-
?r(/.s- oHeiifalis (Temminck and Schlegel), l)y expe-
dition vessels is therefore of interest (table 3).
Furthermore, the frequency with which this

far as is known, no other distribution i-ecords exist
for bluefin tuna from this general area.

The captured fish were all large and weighed
from 150 to 500 pounds eviscerated and with gills
removed. Since these fish were cleaned at sea
immediately after capture and the viscera dis-
carded, it was not possible to examine the internal
organs and gill rakers. The pectoral fins of those
individuals examined were comparatively short,
and eacli fish was characterized by a dark over-all
coloration, which varied from black dorsally to
a dusky graj' veutrally. Measurements of dif-
ferent body characters, using standard morpho-
metric techniques described by Marr and Schaefer
(1949), were taken of four fish. The data are
presented in table 4.

There are three commonly recognized bluefin
species inhabiting the Pacific Ocean: the south-
ern bluefin tuna of Australia, Thimrvus maccoyi;
the Japanese bluefin or black tuna. Thunnus or'i-
entalis; and the so-called California bluefin tuna,
Thviimis thi/niiii,s. which is found in the eastern
Pacific and adjacent waters. The presently recog-
nized northernmost limit of distribution of T.
maccoyi is Sydney, Australia (Serventy 1941).
The Japanese bluefin tuna, T. oriodaJis, which has
yet to be proved distinct from T. thynnus, may
occur as far south as the equator, for there are

118

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Table 4. — Measurevienls of four bluefin tuna from the western
equatorial Pacific

Fish No. 1

Fish No. 3

Fish No. 5

Fish No. 7

Date of capture

June 17

4''20' N.
145°20' E.

Julys

2''39' N.
148°4fl' E.

July 14

3'>48' N.
147''55' E.

487

2.239

631

661

1.185

1,373

748

675

July 26

Locality of capture:
Latitude

2°25' N.

I."i5°49' E.

Approximate weight
(less viscera and gills)

4.30

Total length mm . .

Head length mm-_

enout to insertion first
dorsal mm--

Snout to insertion second
dorsal .mm,-

Snout to insertion anal

mm -

Snout to Insertion ven-
tral mm..

Ventral insertion to
vent ' mm..

Greatest body depth

2.255
600

648

1.221

1.354

698

667

.578
418

441
391

48

2,139
582

624

1.136

1,253

649

632

550
406

344

331

46

2, 205
599

642

1,172

1,310

674

676

Length pectoral mm..

Length second dorsal

mm..

Length anal mm..

Diameter of iris mm..

406

423

428

61

389

377
365

45

I DeQned as the distance from a line connecting the insertions of the ventral
fins to the anterior edge of the vent.

records of this species from the southern Philip-
pine Ishmds as cited by Wade (1950b). How-
ever, Wade believed that the southern distribution
of T. orientalis was limited to the northern Philip-
pine Islands and that other records were of stray
fish.

The bluefin tuna herein recorded have been
assigned to T. (m-entalis on the basis of distribu-
tion alone. It may be shown in the future that T.
orientalis is either a valid species or is synonymous
with T. thynnus.

SUMMARY

Various biological investigations were con-
ducted aboard a Japanese tuna mothership on
tunas and other fishes landed by longline-fishing
vessels which operated in waters south of the Caro-
line I.slands during the summer of 1950. The re-
sults of these studies shed new light on the spawn-
ing and distribution of tuna species found in the
western equatorial Pacific.

Gonads of yellowfin tuna and big-eyed tuna were
examined for sexual maturity, and their condition
suggests the existence of spawning grounds for
these two species in or near the region fished. The
yellowfin probably spawns most actively during
the summer months. Observations of big-eyed
tuna lead to the conclusion that this species spawns

from June to September, and possibly during other
seasons of the year.

Several juvenile oceanic skipjack were recovered
from the stomachs of tunas and other pelagic
fishes. This is definite proof that oceanic skip-
jack spawn extensively in or near the area covered
by the expedition.

The occurrence of bluefin tuna in equatorial
waters is recorded on the basis of several fish
caught from June to September 1950.

LITERATURE CITED

Abe, Tokihaku.

1939. A list of the fishes of the Palao Islands. Palao
Trop. Biol. Sta. Studies, No. 4, pp. 523-583.
GoDsiL, Harey C, and Robeet D. Byebs.

1944. A systematic study of the Pacific tunas. Califor-
nia Div. Fish and Game, Fish Bull. 60, 131 pp., 18
tables, 76 flgs.
Hatai, Shinkishi, et aL

1941. A s.vmposium on the investigation of tuna and
skip.iack spawning grounds. South Sea Science
[Kagaliu Nanyo], vol. 4, No. 1, pp. 64^-75.

HoLI.ISTER, GlOKIA.

1934. Clearing and dyeing fish for bone study. Zoo-
logica, vol. 12, No. 10, pp. 89-101, figs. 18-21.

INANAMI, YOSHrrCTKI.

1942. Small skipjacli captured at Truk. South Sea
Fish. News [Nanyo Suisan Joho], vol. 6, No. 1,
p. 524.

KiSHINOUYE, KaMAKICHI.

1923. Contributions to the comparative study of the so-
called scombroid fishes. Jour. Coll. Agrie. Imp. Univ.,
Tokyo, vol. 8, No. 3, pp. 293-475, 26 figs., 22 pis.

1924. Observations on the skipjack fishing grounds.
Proc. Sei. Fish. Assn. [Suisan Gakkai Ho], vol. 4,
No. 2, ijp. 87-92.

LiSSNEE, H.

1934. On races of herring. Jour, du Couseil, vol. 9,
No. 3, pp. 346-364, 2 tables.
Mare, John ('., and Mit.Nint B. ScHAEFiat.

1949. Definitions of body dimensions used in describ-
ing tniias. U. S. Fish and Wildlife Service, Fishery
Bulletin 47, vol. 51, pp. 241-244, 1 flg.
SoHAEFKii, Milker B.

193(i. Contribution to the life history of the surf smelt,
Hyjioiiiesiis pretiosus, in Puget Sound. Washington
State Dept. Fish. Biol. Kept. 35B, 45 pp., 17 tables,
33 figs.
Schaefee. Milnee B., and John C. Mabb.

1948a. Contributions to the biology of the Pacific tunas.
U. S. Fish and Wildlife Service, Fishery Bulletin 44,
vol. 51, pp. 187-206. 5 tigs.

1948b. Juvenile Euthynnus Ihicatiis and Aiixis thazard
from the Pacific Ocean off Central America. Pacific
Science, vol. 2, No. 4, pp. 262-271, 4 flgs.

TUNAS FROM WESTERN EQUATORIAL PACIFIC

119

Sekventt, D. L.
1941. The Australian timas. Council Sci. and Indust.
Res. Australia. I'aniph. No. 104. 48 pp.. 1> figs., 4 pis.

Shapiro, Sidnet.
1950. Th<> .lapanese longline fislici-j for tunas. U. S.
Fish and Wildlife Service, Commercial Fisheries Re-
view, vol. 4, No. 2, pp. 1-26, 16 figs.

Wade, Chables B.

1950a. Observations on the .si)a\vning of Philippine
tuna. U. S. Fish and Wildlife Service, Fisliciy Uul-
letiu 55, vol. .51, pp. 4119-423, 9 tahles. 3 figs.

1950b. .Juvenile forms of Ncothunniin »iiii-roptcni.i, Knt-
smconits ptlamis, and EuthiiiinUH ijnito from Philip-
pine seas. D. S. Fish and Wildlife Service, Fishery
Bulletin 53, vol. 51, pp. 39.')-404, 13 figs.

o

UNITED STATES DEPARTMENT OF THE INTERIOR, Oscar L. Chapman, Secretary
FISH AND WILDLIFE SERVICE, Albert M. Day, Director

POSTLARVAL NEOTHUNNUS
MACROPTERUS, AUXIS THAZARD, AND

EUTHYNNUS LINEATUS FROM THE
PACIFIC COAST OF CENTRAL AMERICA

By Giles W. Mead
Illustrations by Walter B. Schwarz

FISHERY BULLETIN 63

From Fishery Bulletin of the Fish and Wildlife Service

VOLUME 52

UNITED STATES GOVERNMENT PRINTING OFFICE • WASHINGTON : 1951

For sale by the Superintendent of Documents, U. S. Government Printing Office, Washington 25, D. C.

Price 15 cents

CONTENTS

Page

Observations on adults 121

Observations on yofing 122

Key to postlarvae of five species of Central American scombrids 122

Neothunnus macropterus (Temminck and Schlegel) 123

Auxis thazard Lacep^de - 124

Euthynnus lineatus Kishinouye 126

Literature cited 126

m

POSTLARVAL NEOTHUNNUS MACROPTERUS, AUXIS THAZARD, AND
EUTHYNNUS LINEATUS FROM THE PACIFIC COAST OF CENTRAL
AMERICA

By Giles W. Mead, Fishery Research Biologist

UntU 1942, none of the spawning areas of the
several species of eastern Pacific tunas was laiown.
Since that year several such regions have been
identified and in each case the discovery has been
made by indirect means, through the collection
and identification of the pelagic postlarvae, for
the ripe eggs of the tuna have rarely been found.
Knowledge of the location and extent of the
spawning grounds of the tunas depends, therefore,
on being able to identify the young taken in
plankton collections. This paper provides a de-
scription of the identifying characters of the
juveniles of several tunas.

In the late spring of 1949 I had the opportunity
to make collections of pelagic postlarvae in waters
off the Pacific coast of Central America. Supple-
menting this material, a series of uncatalogued
specimens ' from the California Academy of
Sciences, which was collected off Central America
during the 1932 cruise of the Zaca, was examined.

OBSERVATIONS ON ADULTS

The fishes collected in the spring of 1949 were
taken from the motor vessel Alphecca, a tima
clipper fishing for the Westgate-Sun Harbor Co.
of San Diego, Calif. Actual fishing was confined
to the month of May in waters from 50 to 150
miles off the west coast of Nicaragua and El
Salvador. Diu-ing this period the 240-ton catch
consisted of j'ellowfin tuna, Neothunnus maeropter-
11^ (Temminck and Schlegel), and oceanic skip-
jack, Katsuwonus pelamis (Linnaeus), the former
comprising the bulk of the catch by weight and
number. Gonads of 25 of each species were
examined for degree of maturity. It was apparent
from this examination that the yello\vfin tuna
more than 75 centimeters long and all the oceanic
skipjack were in advanced stages of sexual ma-
turity. (Total lengths are taken from tip of snout

I Made available by Lillian Dempster of the California Academy of
Sciences.

963182-61

to distal end of the shortest caudal fin ray.)
Ovaries were swollen and turgid, although no ova
were visible to the imaided eye. Testes of both
yellowfin tuna and oceanic skipjack had milt in the
central duct. Several large male yellowfin were
running ripe, but no females in a similar condition
were observed in the catch. Two female black
skipjack, Evthynvus lineatus Kishinouye, 54.4 and
55.0 cm. m length were taken. Their ovaries were
similar in degree of maturity to those of the oceanic
skipjack. Two ripe female sierra mackerel, Scom-
heromorus sierra Jordan and Starks, were taken in
a bait haul at Alacapule, Mexico, in the Gulf of
Cahfornia. Eckles (1949) has described the post-
larvae of this species. Althougti numerous at-
tempts were made with a high-speed plankton net
to recover the eggs from the surface layers of
waters where mature fish were found, none proved
successful.

Apparently the spa\vning season for the tunas
is a long one and the spawning area large. Ehren-
baum (1924) outlines the probable spawning
grounds in the Mediterranean region and in the
Atlantic for the species represented in his collec-
tions by larvae and postlarvae. He also describes
the degree of maturity and possible migrational
routes of the adults. Similarly, various Japanese
workers have attempted to delimit spawning areas
in the western Pacific, and at present extensive
work is being done near the Hawaiian Islands and
the Phihppines. The spawaiing areas of the tunas
in Central America are now knowm to extend from
Panama north to Nicaragua and El Salvador and
off shore to a distance of more than 100 miles. It is
also probable that spawnmg of yellowfin tuna and
oceanic skipjack occiu-s off Mexico, since the Zaca
collections made there include frigate mackerel
and one larval black skipjack. It is not unlikely
that futiu-e work will show that this spawning
area extends throughout the tropical waters of
Central America.

121

122

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

OBSERVATIONS ON YOUNG

Since the tunas are subject to intensive fishing
in many parts of the world their biology has long
been under investigation. Kishinouye (1919)
outlines the early work done on the larval stages
of these fishes. As he points out in another
paper (1926), the work of Ehrenbaum (1924) is
probably the most important single work on the
young stages of these fishes. The fishes described
by Ehrenbaum (1924), Kishinouye (1926), Liitken
(1880) and other early workers were generally less
than 15 millimeters in length and were taken with
plankton nets. For the larger sizes the investi-
gator is dependent primarily on collections made
under lights or on specimens found in the stomachs
of adult fish. Such specimens as these have been
described by the more recent workers, Schaefer
and Marr (1948a, 1948b), Eckles (1949), Wade
(1949), and others. In this paper I shall describe
specimens principally between 10 mm. and 18 mm.
in length, larger than those taken in planlcton
hauls, and note characters I have fomid useful in
their identification.

As is generally the practice, the Alphecca often
drifted at night while on the fishing grounds,
offering an excellent opportunity for night col-
lecting. The collections were made imder a drop-
light suspended immediately above the water.
Fourteen such collections yielded, among others,
juveniles of the following three scombrid fishes:
Neothunnus macropterus, the yellou^fin tuna;
Euthynnus lineatus, the black skipjack; and Auxis
thazard, the frigate mackerel. Early stages of

Table 1. — Data on postlarval Auxis thazard, Neothunnus
macropterus, and Euthynnus lineatus taken from the
Pacific Ocean off Central America, May 1949

Location

Num-

Date

Species

berof
speci-

Length in

millimeters

Latitude

Longitude

mens

May 7....

11"'23'N.

90'=29..VW.

A. thazard

28

10. 5 to 28. 5

May 10...-

WSS-N.

89°66'W.

A. thazard

2

10. to 28.

E. lineatus

2

7. 6 to 10. 5

May 15... .

U°4fi'N.

87°28'W.

A. thazard

3

11.5 to 35.0

May 16....

11°46'N.

87°41'W.

A. thazard

2

27.0 to 30.0

May 17....

12°16'N.

89°31'W.

A. thazard

2

28. to 30.

N. macropterus.

2.1

IS. 5 to 25.

May 19....

ll''20'N.

87°20'W.

A. thazard

3fi

14. 5 to 31.0

E. lineatus

23

13. 5 to 18.

May 22...-

U''2f.'N.

89°22'W.

A. thazard

15

18.0 to 35.0

May24...-

10°47'N.

89°30'W.

A. thazard

57

13. 5 to 48.

May27..—

12'>50'N.

89-40' W.

A. thazard

1

19.0

E. lineatus

2

18. to 23. 6

May 28...-

11°05'N.

89'>55'W.

A. thazard

76

10. 6 to 48. 5

N.umcropterus-

12

10. 5 to 16.

May29---.

11°05'N.

SO-SS'W.

A. thazard

12

19. 5 to 36.

May 30..--

12''11'N.

go-is'w.

A. thazard

27

24. 5 to 40. 5

N. macropterus-

6

19. 5 to 26. 5

all these species have been described by Schaefer
and Marr (1948a, 1948b) from specimens taken
in the spring of 1947 off Central America. The
identification of their specimens made known
spawning grounds for the yellowfin tuna, oceanic
skipjack, black skipjack, and frigate mackerel off
Costa Rica and Panama. The present collec-
tions extend the known limits of these spawning
regions for three of these species 350 miles north-
west up the Central American coast. Dates,
positions, and other data for the collections are
reported in table 1.

KEY TO THE POSTLARVAE OF FIVE
SPECIES OF CENTRAL AMERICAN
SCOMBRIDS

A workable key for the identification of the
postlarvae of scombrids known to occiu- off
Central America is dependent on a few discrete
external characters. The teeth and body shapes
are similar in all species. Pigmentation, gill
rakers, preopercular spines, viscera, and, to some
extent, fin rays are in the process of development
and show variation within each species at a given
length. The characters used in the key presented
here were taken from specimens of Euthynnus
lineatus fi'om 7.5 mm. to 32.5 mm., Neothunnus
macropterus from 10.5 mm. to 26.5 mm., Scom-
beromorus sierra from 21 mm. to 71 mm., and
Auxis thazard from 10 mm. to 48.5 mm. in length.
The characters used separate species within these
ranges but may not hold true for larger or smaller
specimens. No specimens of Katsuwonus pelamis
were examined but the description of Schaefer
and Marr (1948b) based on two individuals, 21
mm. and 44 mm. in length, has been referred to
in preparation of the key. Thei'e is no spot on
the isthmus of the smaller of these two specimens.
The larger fish was cleared and stained for bone
study, thus destroying all pigmentation.

la. More than 17 spines in the first dorsal. Total number
of vertebrae more than 46, usually 47 or 48. First
dorsal pigmented distally. Pigment spot on point

of isthmus Scomberomoriis sierra.

lb. Less than 17 spines in first dorsal. Less than 46
vertebrae.
2a. First dorsal separated from the second by a distance
equal to or greater than half the length of the first
dorsal; usually 11 spines in first dorsal. Spot on
isthmus. Vertebral count usually 20+19=39
. x'iuxis thazard.

POST LAR\AL TUNA FROM CENTRAL AMERICA

123

Figure 1. — Ncolhunnus macropterus, 10.5 millimeters long.

2b. First dorsal continuous or almost continuous with

second dorsal.

3a. Pigment spot on point of isthmus. First

dorsal 14 to 16, heavily pigmented. Vertebral

count usually 20+ 17 •= 37 -Euthynnu^ lineatus.

3b. No pigment spot on isthmus.

4a. First dorsal 13 or 14, entire fin heavily
pigmented. Vertebral count 18+21'=39

Neoihiinnus macropterus.

4b. First dorsal 16, bearing a few moderately large
spots distally. Vertebral count 20 + 21=41
Katsuwonus pelamis.

NEOTHUNNUS MACROPTERUS (Temminck
and Schlegel)

A total of 42 specimens of this species was taken
in the collection, ranging from 10.5 mm. to 26.5
mm. in length. Representative specimens were
cleared with potassium hydroxide and stained
with alizarin (Hollister 1934) so that the bone
structure could be examined and the fin rays
counted. Fin- ray counts in very small specimens
are virtually impossible if the specimens are not
stained.

NeothunnxLs macropterus can be identified by its
characteristic shape, vertebral count (18 + 21),
and coloration, as described by Schaefer and Alarr
(1948b). No gill rakers can be seen in fish smaller
than 15 mm. The position and extent of the
visceral organs cannot be determined without
sectioning. Schaefer and Marr (1948b) note the
characteristics of the viscera and gill rakers in
specimens over 15 mm. With the exception of
the pectoral, the fins of a 10.5-mm. fisii have
within one or two rays of the complete complement
of spines or rays. The number of rays in the
pectoral fin increases from 13 in the 10.5 mm.

specimen to 30 in fish of 30 mm. Each half of the
upper and lower jaws bears 11 small, pointed,
irregularly spaced teeth. It was found that these
young yellowfin can be separated readily from the
other specie»s taken, without a special preparation,
by the absence of any pigmentation on the point
of the isthmus and by the heavily pigmented first
dorsal fin. In aU Euthynnus lineatus and Auxis
thazard examined there is a pigment spot on the
point of the isthmus overlying the junction of the
pectoral and pelvic girdles. No post larval Kats%
wonus pelamis were available for study, but
Milner B. Schaefer of the Pacific Oceanic Fishery
Investigations informs me that this spot is not
present on a 21-mm. specimen taken off Costa
Rica. I have found no reference to this spot in
the literatiu-e. This character is most useful for
separating very small A^. macropterus and E.
lineatus since both have a black dorsal fin and
they resemble each other closely in botly shape
until they attain a length greater than 15 mm.

Dermal pigmentation on a 10.5-mm. Neothunnus
macropterus is restricted to a thin strip along the
first dorsal fin insertion, a patch on the tip of the
snout and the heavily pigmented first dorsal fin.
Subcutaneous pigmentation occurs over the brain
and in the peritoneum overlying the dorsal third
of the viscera. In an 11-mm. specimen, the thin
strip along the first dorsal insertion extends
posteriorly to the base of the third ray of the
second dorsal fin; by the 12-mm. stage it lines the
upper margin of the body from the operculum to
the terminal rays of the second dorsal. Those two
specimens show a faint strip along the postcro-
ventral margin of the orbit. From this size up to

124

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

33 mm., the largest yellowfin examined, the color
pattern follows closely the description published
by Schaefer and Marr (1948b).

A 12-mm. yellowfin displays three prominent
spines at the angle of the preoperculum. Anterior
to these are thi'ee lesser spines, and thiee others
protrude from the preoperculum above the lai'ge
spines. With increasing length of fish, all spines
become more and more reduced in relation to the
size of the head. They are apparently overgrown
by the superficial layers of the preopercular bone.
In fish of 26 mm., the only spines discernible are
those at the angle of the preoperculum, and even
these are noticeably less evident. There appears
to be little, if any, growth in these spines over the
size range of the fish in my collections.

AUXIS THAZARD (Lacepede)

This species is the most numerous in the night
collections. Young stages are present in 12 of the
14 collections. The 157 specimens taken range
from 10 to 49 mm. in length. In addition to the
collections listed in table 1, two larger Auxis, 79
and 117 mm. fork length, were taken from the
stomach of a large yellowfin caught on May 6 at
11°40' N. latitude, 91°00' W. longitude. These

two fish, both broken and with the skin and fins
digested away, can be recognized as members of
the genus Auxis by the elongated right lobe of the
liver, the total vertebral count (39), and the struc-
ture of the individual vertebrae as described by
Kishinouye (1923: 460). The gill-raker counts,^
10-f- 1-1-32 and lO-f- 14-33, approximate the counts
made by Schaefer and Marr (1948a) on most of
their juveniles. In a recent paper. Wade (1949)
separates the Philippine species, Auxis (hazard
and A. tapeinosoma, on the basis of characters
among which only the gill-raker count is apphcable
to the young stages.^ He also points out, as
Schaefer and Marr (1948a) suggested, that there
are probably two species of Auxis in Central Amer-
ican waters. If we assume that there are two
species and that they can be separated by charac-
ters applicable to the Philippine species, my two
juveniles, as well as the postlarvae large enough to
show a definitive gill-raker count, are A. thazard.
The giU-raker counts of 10 specimens are given in

2 The method used in counting and recording gill rakers is the same as that
used by Wade (1949) in his discussion of the genus Auih.

3 Wade's description of Anns tapeinosoma agrees with that of Bleeker
(1854). However, the pattern and extent of the corselet scales in Bleeker's
figure (18M, pi. 7) of A. tapeinosoma agrees more closely with Wade's figure of
A. thazard.

Figure 2. — Aiais thazard, 11.5 millimeters long.

Figure 3. — Attxis thazard, 18 millimeters long.

POST LARVAL TUNA FROM CEXTRAL AMERICA

125

table 2. The most anterior arch on both right and
left sides was counted. Specimens No. 7 and No.
8 are apparently too small to have a complete set.

Table 2. — Oill-raker coui>ts ' of postlarval and juvenile
Auxis thazard

Specimen

Fork

length, in

millimeters

Right first arch

Left first arch

No. 1

34
34

41
38
42
35
26
30
79
117

9+1+30=40
8+1+30=39
8+1+31=40
9+1+31=41
9+1+32=42
7+1+30=38
5+1+22=28
7+1+28=36
10+1+32=43
10+1+33=44

8+1+30-39

No. 2

8+1+29-38

No. 3 -

8+1 +.30 -39

No. 4..-

7-i-l+32=40

No. 6

9+1+31-41

No. 6 -

6+1+2S-35

No. 7

4+1+22-27

No. 8

7+1+20-34

No. 9

10+1+33-44

No. 10

10+1+33=44

' The method used in counting and recording gill rakers is the same as that
used by Wade (1949) in his discussion of the genus Auxis.

The smallest Auxis in the collections is a dam-
aged 10-nim. specimen. Dermal pigmentation is
confined to narrow strips along the bases of the
second dorsal and anal fins and the dorsal and anal
finlets, along the lateral line from a point below
the posterior end of the second dorsal fin to the
posterior extent of the finlets, along the postero-
ventral margin of the orbit and to a small spot on
the point of the isthmus. The fins are usually
colorless although the first dorsal may bear a few
scattered melanophores. Four small spines occiu-
along the angle of the preoperculum. Each half
of the upper and lower jaws bears about 10 small
teeth. With increasing size of fish, the local centers
of pigmentation expand. On fish of 13 mm. the
dorsal strip of body pigmentation extends from the
operculum to the caudal at its point of least depth,
and a light coloration appears on the snout and
operculum. All areas in the dorsal hall" of the body

of fish larger than 20 mm. bear at least a light
covering of pigment spots. The degree of pig-
mentation varies greatly from specimen to speci-
men in this species. The pattern here described is
that found to be the most common.

EUTHYNNUS LINEATUS Kishinouye

This species is represented in the collections by
27 specimens, ranging from 7.5 imn. to 23.5 mm.
in length. Two fish were cleared and stained
and each was found to have a vertebral count of
37, the first caudal vertebra in each case being
the twenty-fii'st. As is the case with Neothunnus
macrophrus and Auxis thazard, the viscera of the
smallest specimens cannot be studied adequately
unless specimens are sectioned. Schaefer and
Marr (1948a, 1948b) describe the viscera in speci-
mens of Euthynnus lineatus more than 15 mm.
long. The first dorsal, point of the isthmus,
anterior half of the lower jaw, tip of the snout,
posteroventral margin of the orbit, and operculum
of the smallest specimen (7.5 mm.) bear scattered
melanophores. Subcutaneous pigmentation cov-
ers the brain and the dorsal margin of the peri-
toneum. The only dermal pigmentation evident
on the body of this specimen is a pau- of light
spots at the posterior end of the anal fin insertion.
At 10.5 mm. in length, light pigmentation appears
at the base of the first and second dorsals. Body
pigmentation is still confined to the bases of the
anal and the two dorsal fins. By 14 mm., the
pigment has spread anteriorly from the base of
the first dorsal to the area overlying the brain.
Coloration along the lateral line first appears m a
16-mm. specimen as a few faint spots. On this fish

Figure 4. — Eutlii/iniii.'! lineatus, 14 millimeters long.

126

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

the dorsal body pigmentation extends posteriorly
from the operculum to the end of the second
dorsal. In the region of the second dorsal these
spots form a faint line a half millimeter from the
dorsal margin of the body. Above this line,
along the insertion of the fin itself, is the horizontal
bar of dark pigment characteristic of smaller speci-
mens. By 17.5 mm., the lateral pigmentation
has extended as far back along the Ime of the
vertebral column as the posterior end of the second
dorsal and anal fins. Coloration along the anal
insertion is stUl restricted to the few patches
characteristic of the smallest E. lineatus. The
posterior half of the orbit is dark. Coloration
of snout, jaws, and operculum is more dense.
At 22 nam., coloration fii-st appears over the

terminal segments of the vertebral colmnn and
on the extreme base of the median caudal rays.
The dorsal half of the body is dark as far back as
the caudal peduncle.

Preopercular spines are longer and slenderer
than those of A'^. macropterus. The angle of the
preoperculum bears the three largest spines.
Above these is a pair of small spines; anterior to
them are three others. With increasuig length
of fish, all become overgTO^vn to a certain extent.
At 18 mm., the most dorsal and anterior spines
are no longer visible without the use of special
techniques. The remainder ai-e visible, although
less distinct, m the largest E. lineatus in the
collections.

Figure 5. — Euihynnus lineatus, 22 millimeters long.

LITERATURE CITED

Bleeker, Pieter.

1854. Fauna ichthyologicae japonicae species novae.
Natuurkundig Tijdschrift voor Nederlandsch-Indie
uitgegeven door de Naturkundige Vereenigining in
Netherlandsch-Indie, vol. 6, pp. 395-426.
1854-57. Nieuwe nalezingen op de ichthyologie van
Japan. Verhandelingen van het Bataviaasch
Genootschap van Kunsten en Wetenschap, vol.
26, pp. 1-132, 8 pis.
EcKLEs, Howard H.

1949. Observations on juvenile skipjack (Katsu-
wonus pelamis) from Hawaiian waters and sierra
mackerel {Scomberomorus sierra) from the Eastern
Pacific. U. S. Fish and Wildlife Service, Fish.
Bull., No. 48, vol. 51, pp. 245-250.
Ehrenbaum, E.

1924. Scombriformes. Rept. Danish Oceanog. Exped.
1908-1910 to the Mediterranean and Adjacent
Seas, vol. 2 (Biology), No. 8, A. 11, pp. 1-42.
HoLLisTER, Gloria.

1934. Clearing and dyeing fish for bone study.
Zoologica (N. Y.), vol. 12, No. 10, pp. 89-101.

KiSHlNOUYE, KaMAKICHI.

1919. The larval and juvenile stages of the Plecostei.
Suisan Gakkai Ho, vol. 3, no. 2. (U. S. Fish and
Wildlife Service, Pacific Oceanic Fishery Investi-
gations, Translation No. 20 by W. G. Van Campen;
hectographed.)

1923. Contributions to the comparative study of the
so-called scombroid fishes. Jour. Coll. Agric,
Tokyo Imp. Univ., vol. 8, No. 3, pp. 293-475, 22 pis.

1926. An outline of the studies of the Plecostei
(tuna and skipjack) in 1925. Suisan Gakkai Ho,
vol. 4, no. 3, 1 pi. (U. S. Fi.sh and Wildlife Service'
Pacific Oceanic Fishery Investigations, Transla-
tion No. 18 by W. G. Van Campen; hectographed.)

LDtken, Ch. Frederik.

1880. Spolia Atlantica. Bidrag til Kundskab om
Formforandringer hos Fiske under deres Vaext og
Udvikling, saerlight hos nogle af Atlanterhavets
H0js0fiske. Vidensk. Selsk.Skr.,5. Raekke, natur-
videnskabelig og mathemetisk Afd., vol. 12, No. 6,
pp. 413-613.

POST LARVAL TUNA FROM CENTRAL AMERICA

127

Meek, Seth E., and Hii.debrand, Samuel F.

1923. The marine fishes of Panama. Pub. Field
Mus. Nat. Hist., Zool. ser. 15, part 1, pp. 1-330,
24 pis.

SCHAEFER, MlLNER B., AND MaRR, JoHN C.

1948a. Juvenile Euthynnus lineatus and Auxis
thazard from the Pacific Ocean ofi' Central America.
Pacific Science, vol. 2, No. 4, pp. 262-271.

1948b. Spawning of yeUowfln tuna (Neolhunnus

macropterus) and skipjack (Katsvwoniis pelamis) in
the Pacific Ocean off Central America, with
description of juveniles. U. S. Fish and Wildlife
Service, Fish. BuU., No. 44, vol. 51, pp. 187-196.
Wade, Charles B.

1949. Notes on the Philippine frigate mackerels,
family Thunnidae, genus Auxis. V. S. Fish and
Wildlife Service, Fish. Bull., No. 46, vol. 51,
pp. 229-240.

o

UNITED STATES DEPARTMENT OF THE INTERIOR, Oscar L. Chapman, Secretary
FISH AND WILDLIFE SERVICE, Albert M. Day, Director

JUVENILE OCEANIC SKIPJACK

FROM THE

PHOENIX ISLANDS

By Bell M. Shimada

FISHERY BULLETIN 64

From Fishery Bulletin of the Fish and Wildlife Service

VOLUME 52

UNITED STATES GOVERNMENT PRINTING OFFICE • WASHINGTON : 1951

For sale by the Superintendent of Documents, U. S. Government Printing Office, Washington 25, D. C.

Price 10 cents

JUVENILE OCEANIC SKIPJACK FROM THE PHOENIX ISLANDS

By Bell M. Shimada, Fishery Research Biologist

Studies by various investigators have added
substantially to oiu- hitherto hinited knowledge of
the spawTiiag of oceanic skipjack {Katsuwonus
pelamis Linnaeus 1758) ui the Pacific Ocean.
From evidence based on the examination of
gonads or the capture of juveniles (see table),
spawning grounds have been indicated in waters
ofi' Central America (Schaefer and Marr 1948),
the Hawaiian Islands (Eckles 1949), the northern
Marshall Islands (Marr 1948), the Ti'uk Islands
(Inanami 1942), the Phihppine Islands (Wade
1950), and the northern Ryukyu Islands (Kish-
inouye 1923). The existence of additional spawn-
ing grounds near the PhoenLx Islands in the south
central Pacific is demonstrated by the captm-e of
juveniles incidental to biological, oceanographical,
and exploratory-fishing studies conducted in this
locality during the summer of 1950 by the Pacific
Oceanic Fishery Investigations of the U. S. Fish
and Wildlife Service, Honolulu, Hawaii.

During a regular hydrographic cruise of the
Pacific Oceanic Fishery Investigations research
vessel Hugh M. Smith, between Hawaii and the
Phoenix Islands, two juvenile scombroids were
collected on July 18, 1950, at 3°50.5' S. and
171°48.5' W. by collaborating scientist V. E.
Brock,' and subsequently identified as oceanic
skipjack, Katsuwonus pelamis. These young fish,
measiu-mg 35 mm. and 48 mm. m total length,-
were captui-ed by dipnet under a night light while
the vessel was adrift.

On August 5, 1950, a sister ship, Hem-y O'Mal-
ley, visited the Phoenix Islands for exploratory
fishing. Wliile night-light collectuig from this
vessel at a position approximately 400 yards ofi'
the west end of Hull Island (4°30' S., 172°11' W.),
K. Yee,' caught thi-ee additional specimens of
juvenile K. pelamis. Total lengths of these fish
were 20 mm., 22 mm., and 36 mm.

Director, Division of Fish and Game, Territory of Hawaii.

3 Defined as the distance from the tip of the snout to the tip of the shortest
median caudal ray.

s Fishery Methods and Eriuipment Specialist, Pacific Oceanic Fishery
Investigations, U. S. Fish and Wildlife Service.

953184—51

All five specimens exhibit body contours typical
of juvenile oceanic skipjack and possess a very
slightly pigmented first dorsal fin and a colorless
second dorsal fin, which are characteristic of young
fish of this species (Schaefer and Marr 1948, Wade
1950). The 48-mm. juvenile of the Smith col-
lection was stained with alizarin red S and found
to have a "trellis" and a total of 41 vertebrae,
m'ostyle included. The 20-nun. specimen of the
O'Malley collection was stained and cleared after
HoUister's (1934) method and was found to have
a vertebral count of 20-1-21. These characteristics
are definitive of Katsuwonus pelamis as shown by
Kishmouye (1923), Frade and de Buen (1932),
and Godsil and Byers (1944).

The 35-mm. specimen is colored with light-
brown pigmentation except for the belly, which is
colorless, and the head. Pigmentation is more
concentrated dorsally and along the sides of the
body where it outlines a narrow band along the
midline. Scattered melanophores on the peri-
toneum are visible tlnough the thin body wall and
extend caudally to the anus. The top of the
head forward of the nape is brown in color with
subcutaneous melanophores on the underlying
brain covering. The upper portion of the oper-
culum, the posterior and inferior orbit, as well
as the sides of the upper and lower jaw, are lightly
pigmented with brown. The membrane between
the first and second dorsal spme is irregularly
marked witli black spots from the Inise to tlie
distal ends of the spines; the membrane comiecting
the remaining dorsal spines is similarly marked
but only near the tips of the spines, the basal
half beuig colorless. The second dorsal is with-
out color. Black pigment spots are present along
the upper pectoral raj's and along the upper base
of the fin. Similar spots are present along the
insertion of the median fins and finlots.

The first dorsal fin is composed of 16 spines of
which the second is the longest. Fouileen rays
are present in the second dorsal fin. There are
8 dorsal fuilets and 7 anal finlets. An interradial

129

130

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

membrane is present in both series of finlets and
joins individual finlets at a point midway between
the insertion and the tip. The anal fin has 15
soft rays, the pectoral 27 rays, and the pelvic 6
rays. The tip of one large spme and outlines of
two additional spines are visible at the angle of
the preopercle.

The two smallest specimens, of 20 mm. and 22
mm., agree in general with the description pre-
viously given for oceanic skipjack of this size by
Schaefer and Marr (1948), but differ in a few
respects from the larger juveniles. Body colora-
tion is lighter dorsaUy, and pigmentation is more
intense on the peritoneimi. The snout appears to
be more sharply pomted, possibly because the

upper jaw noticeably overlaps the lower jaw.
Two conspicuous spines are present at the bend
of the preopercle^ and the tip of one additional
spine is visible on the inferior margm. Pigmen-
tation of the first dorsal fin is linuted to distal
ends of the fin membrane between the first and
seventh or eighth spine. This is also true of
larger specimens, but in the latter coloration ex-
tends to the base of the first few anterior spines
as well. The basal portion of the pectoral fin is
colorless, and the dorsal and anal finlets are
joined at the tips by interradial membranes.

The capture of these small juveniles is definite
evidence that oceanic skipjack spawn in the
Phoenix Islands area.

Published records oj juvenile oceanic skipjack (Katsuwonus pelamis Linnaeus) from the Pacific Ocean

Date of capture

August 1916.
July 1923---

Do

August 1923- _
Apr. 14, 1924.

May 16, 1924-
May 19, 1924.

Do

May 21, 1924-

Do

Do

May-June 1924.

Do

June 1924

Do.
Do.

Apr. 23, 1939.
May 3, 1940..
Jan. 28, 1947-

Mar. 29, 1947.
July 24, 1947.

Do

May 7, 1948-

July 13, 1948.
Sept. 3, 1948-

Locality

Ryukyu Islands (Oki-
nawa) .
Ryukyu Islands

do

do

Ryukvu Islands (29°47'

N-i29°25' E.)
Ryukvu Islands (28° 10'

"N-i29°15' E.)
Rvukvu Islands (29°51'

N-i29°52' E.)
do

Ryukvu Islands (29°47'

N-i29°25' E.)
do

.do.

Ryukvu Islands (28°31'
N-i29°, 131° E.)

do

Ryukyu Islands

.do-
.do-

Truk Islands

do

Costa Rica (9°22.5' N.-

85°47.5' W.)
Costa Rica (9° 10' N-

85°20' W.)
Marshall Islands (Bikini

Atoll).
do

Philippine Islands

(6°37.2' N-121°31' E.)
Hawaiian Islands (20°30'

N- 158° 45' W.)
Hawaiian Islands (19°33'

N-156°00' W.)

Size

Num-

of

ber

speci-

of

men

speci-

(mm.)

mens

210

1

105

1

125

1

210

1

26

1

58

1

60

1

80

1

63

1

83

1

85

1

3

2

4

3

120

1

153

1

100 to

3

140

198

1

45

1

21

1

44

1

45

1

50

1

13 to

6

27

113 to

6

118

183

1

How collected

Pole and line (?)

From skipjack or yellow-
fin tuna stomach.

do

do

From skipjack stomach.

From skipjack or yellow

fin tuna stomach.
do

do

do

do

do

Plankton net

do

From skipjack or yellow-
fin tuna stomach.

do

Dipnet

Pole-and-line fishing

From skipjack stomach.
Dipnet

do

Regurgitated by skip-
jack.

do

Dipnet

Regurgitated by skip-
jack.
From skipjack stomach-

Reference

Kishinouye (1923, p. 388).

Kishinouye (1924, pp. 88-
89).

Do.

Do.
Kishinouye (1926, p. 128).

Kishinouye (1924, pp. 88-
89).
Do.

Do.

Do.

Do.
. Do.
Kishinouye (1926, p. 128).'

Do.i
Kishinouye (1924, pp. 88-
89).

Do.
Kishinouye (1926, p. 128).

Inanami (1942, p. 524).

Do.'
Schaefer and Marr (1948,
p. 193).

Do.

Marr (1948, p. 202).

Do.
Wade (1950, p. 399).

Eckles (1949, p. 245).

Do.

' Identification reported as doubtful.

SKIPJACK FROM THE PHOENIX ISLANDS

131

LITEIL\TURE CITED

EcKLEs, Howard H.

1949. Observations on juvenile oceanic skipjack
(Katsuwonus pelaniis) from Hawaiian waters
and Sierra mackerel {Scomberomorus sierra)
from the eastern Pacific. U. S. Fish and Wild-
life Service, Fishery Bulletin No. 48, pp. 245-
250, 3 figs.

Fr.\de, Fkrn.^ndo, and Fernando de Buen.

1932. Poissons scomberiforraes (excepte la famille
Scombridae) . Clef de classification principale-
ment d'apres la morphologie interne. Comm.
Int. pour I'Expl. Sci. de la M6diterrande,
Rapp. et Proc. Verb,, vol. 7, annexe A, pp.
69-70.

GoDsiL, Harry C, and Robert D. Byers.

1944. A systematic study of the Pacific tunas. Calif.
Div. Fish and Game, Fish Bulletin 60, 131
pp., 18 tables, 76 figs.

HoLLisTER, Gloria.

1934. Clearing and dyeing fish for bone study. Zool-
ogica, vol. 12, Xo. 10, pp. 89-101, figs. 18-21.

InaNAMI, YOSHIYUKI.

1942. Small skipjack captured at Truk. South Sea
Fish. News [Nanyo Suisau Joho], vol. 6, No.
1, p. 524.

KiSHINOUYE, KaMAKICHI.

1923. Contributions to the comparative study of the
so-called scombroid fishes. Jour. Coll. Agric.
Imp. Univ., Tokyo, vol. 8, No. 3, pp. 293-475,
26 figs., 22 pis.

KiSHINOUYE, KaMAKICHI.

1924. Observations on the skipjack fishing grounds.

Proc. Sci. Fish. Assn. [Suisan Gakkai Ho],

vol. 4, No. 2, pp. 87-92.
1926. An outline of studies of the Plecostei (tuna and

skipjack) in 1925. Proc. Sci. Fish A.ssn.

[Suisan Gakkai Ho], vol. 4, No. 3, pp. 125-137,

Ipl.

Marr, John C.

1948. Observations on the spawning of oceanic skip-
jack (Katsuwonus pelamis) and yellowfin tuna
(Neolhunnus macropterus) in the northern
Marshall Islands. U. S. Fish and Wildlife
Service, Fishery Bulletin No. 44, pp. 201-206,
2 tables, 1 fig.

Schaefer, Milner B., and John C. Marr.

1948. Spawning of yellowfin tuna (Neothunnus ma-
cropterus) and skipjack [Katsuwonus pelamis)
in the Pacific Ocean off Central America, with
descriptions of juveniles. U. S. Fish and Wild-
life Service, Fishery Bulletin No. 44, pp. 187-
196, 5 figs.

Wade, Charles B.

1950. Juvenile forms of Neothunnus macropterus,
Katsuwonus pelamis and Euthynnus yaito from
Philippine seas. U. S. Fish and Wildlife
Service, Fishery Bulletin No. 53, pp. 395-404,
13 figs.

o

UNITED STATES DEPARTMENT OF THE INTERIOR, Oscar L. Chapman, Secretary
FISH AND WILDLIFE SERVICE, Albert M. Day, Director

ESTIMATION OF AGE AND GROWTH

OF YELLOWFIN TUNA (NEOTHUNNUS

MACROPTERUS) IN HAWAIIAN WATERS

BY SIZE FREQUENCIES

By Harvey L. Moore

FISHERY BULLETIN 65

From Fishery Bulletin of the Fish and Wildlife Service

VOLUME 52

UNITED STATES GOVERNMENT PRINTING OFFICE — WASHINGTON : 19 5 1

For sale by the Superintendent of Documents, U. S. Government Printing Office
Washington 25, D. C. — Price_,15 cents

CONTENTS

Page

Sources of data and methods of collection 134

Analysis of weight frequency data 135

Discussion 141

Conclusions 145

Literature cited 145

Appendix 146

II

ESTIMATION OF AGE AND GROWTH OF YELLOWFIN TUNA (NEOTHUN-
NUS MACROPTERUS) IN HAWAIIAN WATERS BY SIZE FREQUENCIES

By Harvey L. Moore, Fishery Research Biologist

With a commercially important species, such as
tlie yellowfin tuna (A'eothunnes macropterus Tem-
niinck and Schlcgel), knowledge of age and growth
is essential in both the management and develop-
ment of a fishery. To be able to assign ages and
to determine the rate of growth makes it possible
to determine the number and strength of the year
classes that comprise the fishable stock. A
fishery dependent on a few age groups or year
classes is greatly affected by the marked success
or failure of the brood produced in any one year.
The reduction or increase in numbers is strongly
evident in the total catch when that particular
year class enters the commercial fishery. If,
however, the fishery is composed of many age
groups, the success or failure of spawning in any
one year will have little effect on the total stock.
It is only when there are several consecutive years
of marked failure or success that any appreciable
differences in numbers are evident.

The vital statistics necessary for quantitative
study of fish populations are based on knowledge
of the age composition of the stock. It would be
difficult indeed to determine such statistics as
rates of increase, decrease, fishing, and natural
mortality without some knowledge of age and
growth. These vital statistics are fundamental in
the management of a fish stock.

The age and growth rate of tunas may also be of
value in the study of migrations, since it seems
logical to expect, in general, that short-lived, fast-
growing fish travel shorter distances than fish
which are long lived and slow growing.

Since Petersen's first application of the method
of size-frequency study to age and growth de-
termination of plaice (1922) many such studies of
different species have been made. Much im-
provement in the original method has been made,
and the application of mathematical formulae to
describe the growth of fishes has contributed much
toward its refinement.

Application of length- or weight-frequency
analysis to study of growth of tunas has been
limited. Kimura (1932) calculated growth curves
for bluefin (Thunnus orientalis) and yellowfin
(Neothunnus macropterus) from weight frequencies
of fish taken in Japanese waters from 1924 to 1931.
Although the data were collected over a long
period of time, those for yellowfin were based on a
few specimens if all data were included in the
graphs. An examination of the data, as presented,
shows that the values plotted in the graphs are
based on a few specimens of yellowfin.

Westman and Gilbert (1941) employed length-
frequency distributions in their study of the
Atlantic bluefin (Thunnus fhynnus). The ages of
bluefin as determined by this work were based
primarilj' on scale readings although the conclu-
sions were correlated with the results of the length
frequencies. Westman and Xeville (1942), in
another study of the Atlantic bluefin tuna, used
length frequencies of tuna samples from chum-
ming and trolling catches made during August and
September 1941. The results of this study were
also correlated with scale readings. Brock (1944)
applied the method of length frequencies in a
study of albacore (Oerino alalunga) taken in the
North Pacific and was able to demonstrate the
growth of size groups through the albacore season.
Partlo (1950) has produced weight-frequency dis-
tributions of albacore {ThunnuN alalunga) taken
in the waters of British Columbia during 1949.
Sampling was not sufficient to show changes in
length throughout the albacore season, but the
frequency distributions show the definite size
groups which make up the fishery. Okamoto
(1940) apphed Petersen's method to weight data
of skipjack (Katsuwonus vagans) taken in Japanese
waters. It was possible to follow definite modal
groups through 5 montlis of the fishing season.
The question whether modes represented age
groups or whether they represented different

133

134

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

strains of skipjack was raised. The conclusion
was in favor of age groups.

There has been httle study of age and growth
determination of Hawaiian tunas. Some measure-
ments of the skipjack {Katsuwonus pelamis) were
collected by Bonham (1946) in 1944 and 1945,
and length frequencies were plotted from these
data. Bonham suggested the possibility that
two successive year classes were present, but
recognized the limitations of his data and did not
attempt to assign ages. Brock (ms.) made a
rather detailed study of size frequencies of skip-
jack. He was able to identify modal groups in
the catches of successive years and to demon-
strate progression of the modes during the year,
whence he concludes they are year classes. No
previous studies have been made of the Hawaiian
yellowfin tuna.

SOURCES OF DATA AND METHODS OF
COLLECTION

The data for this study were obtained from two
different types of fishery, the long-line or flag-line
fishery, ami the pole or live-bait fishery. The
long-line fishery in Hawaii is carried on through-
out the year in most of the waters around the
main Hawaiian Islands. The catch from this
fishery is sold primarily to the fresh-fish markets
by auction. The live-bait fishei-y, on the other
hand, is more seasonal and the catch is primarily
for the cannery, although some of the fish are
sold on the fresh-fish market, especially when
the cannery is not operating during the slack
season.

The long-line fishery is conducted by means of
setlines made up of units of gear known as baskets.
The term "basket" is derived from woven bamboo
baskets in which the units of gear are stowed. A
vessel fishes a long-line composed of about 30
baskets, each of which is from 140 to 203 fathoms
in length and has 4 to 6 brancii lines with hooks.
When the baskets are fastened together and the
long-line is set, the hooks fish from 30 to 50
fathoms in depth (June 1950).

Long-lines are set in the early morning and are
fished only during the daylight hours. LTsually
a few tunas are taken each day, and the catches
may also contain several marlin, swordfish, and
sharks. Fish taken by this method are generally
large in comparison with those taken in the live-

bait fishery. Yellowfin tuna caught by this
method average about 140 pounds in weight, and
the big-eyed tuna {Parathunnus sibi) are heavier.
The total landings, by months, vary considerably
in both the numbers and the species of fish caught.
The yellowfin is the most abundant species taken
during the summer months, and the big-eyed tuna
dominates the winter catch. Albacore also are
caught on the long-lines during the winter months,
but the numbers are small in comparison with
either of the other two species. Although the
tunas are definitely seasonal in availability, some
fish of all three species usually are taken during
the entire year.

The second source of data was the live-bait
fishery. This fishery is seasonal; most of the
catch is taken during the summer months. The
fisheiy is dependent on small live fishes which are
used as chum to lure the tunas within reach of the
feather lures or live bait on hooks on the poles of
the fishermen. The fish caught by this method are
much smaller than those taken by the long-line
method; the largest weigh near 25 pounds. The
fact that no large fish are caught on the surface by
the pole or live-bait fishery and no small fish are
caught at depths fished by the long-line gear indi-
cates that there may be a possible vertical migra-
tion downward of yellowfin tuna during the early
years of life.

Although this fishery is primarily for the skip-
jack, mixed schools of skipjack and yellowfin or
skipjack and big-eyed tuna are sometimes found.
Approximately 12 to 15 catches from mixed schools
are landed at the cannery each season. It was
from schools such as these that tlie data on small
yellowfin were collected for this study. Schools
of tuna, whether a pure school of skipjack or
mixed with either yellowfin or big-eyed tuna,
tend to contain fishes with little range in size.
Brock (ms.) says of skipjack schools, "no indivi-
dual school of fish sampled contained fish differing
by more than 20 centimeters in length and usually
much less." Differences in sizes of fish from dif-
ferent schools, however, were as much as 50
centimeters.

Weight and length frequencies of the long-line
catch were taken from fish sold at auction by the
Kyodo Fishing Co., Ltd., Honolulu. The officials
of this company were kind enough to allow measur-
ing of the fish on the auction floor before the

AGE AND GROWTH OF YELLOWFIN TUNA

135

bidding had begun. As the fish are sohl indi-
vidually, it is necessary for the company to keep
accurate records of the weight of each fish sold.
AYeights as determined by the auction company
were taken from the auction records whi<'h were
available beginning vvith November 1947. Weights
of tunas caught by the live-bait fishery during 1949
were recorded by Fish and Wildlife Service
scientists at the cannery of Hawaiian Tuna
Packers, Ltd. This study includes only the data
of 1948 and 1949.

The data for the 2 years consist of 4,793 indi-
vidual weights of yellovvfin tuna ranging from 5
to 265 pountls. Of the total number of weights
taken, 124 are of small fish most of which were
representative of four mixed schools caught by
live-bait methods. A few of this group were taken
incidentally by trolling or hand-lining. The re-
mainder of the data were obtained from the auc-
tion records.

Since small yellowfin and big-eyed tuna are
likely to be confused, a check of the reliability of
species determination by the auction company was
made during October 1949. During this period
95 yellowfin and 272 big-eyed tuna were identi-
fied by various Fish and Wildlife Service scientists.
In no case was there found to be an auction record
in disagreement with our identifications. It was
concluded that the assignment of species as shown
by the auction records was accurate.

The auction records provided an excellent source
of weight-frequency data for several reasons. Be-
cause Honolulu is the center of population in the
Hawaiian Islands, most of the long-line catch is
landed there, and most of this long-line catch
passes through the auction of the Kyodo Fishing
Co., which supplied the auction records. Fish
taken by long-line gear are generally few in num-
ber per day's fishing, which would suggest that
either the fish tend to be solitary in habit or, if
they are schooled, only a few fish from several to
many schools are caught during a fishing trip.
Since tunas tend to school by size (Brock, in un-
published ms.; Schaefer 1948), samples of this
sort which are composed of a few fish from each
of many schools will tend to be more nearly
representative than large samples drawn from
only a few schools as are the samples from the
cannery.

Weights of fish in the round, that is, the entire

uncleaned fish as landed at the dock, were weighed
on the auction company's scales or on those of the
Hawaiian Tuna Packers. Weights were recorded
to the nearest pound for long-line fish and to the
nearest quarter pound for small fish taken by
live-bait fishing.

ANALYSIS OF WEIGHT FREQUENCY DATA

The initial step in processing the raw data (see
the appendix) was to plot the weights of individual
fish as frequency distributions for monthly
periods. A class interval of 10 pounds was arbi-
trarily chosen, with midpoint values of 4.5, 14.5,
and so on. Because the monthly catches varied
considerably in numbers of fish, they were made
comparable by converting the class frequencies
into percentages of the total for the month. The
average frequency distribution for each year was
calculated by averaging the 12 monthly -percentage
curves. The results are plotted in figures 1 and
2 for 1948 and 1949. In order to show more
clearly the presence of modes, positive de^nations
from the mean curve for the year are shaded on
the graph for each month. The scale at the
bottom of each graph is in terms of both weight
in pounds and length in centimeters. The length
scale was derived from the equation log L=
1.45660 + 0.33290 log IF which was calculated from
a sample of 200 length-weight measurements of
yellowfin tmia collected during 1949 by Fish and
Wildlife Service scientists.

Because there were many irregularities evident
in the frequency curves of each month's catch in
both 1948 and 1949, and because the 2 years were
similar in monthly frequency distributions, it was
convenient to combine the 1948 and 1949 data.
The combination of the data for the 2 years was
then treated in the same manner as that of the
the individual years with the exception of a process
of first smoothing the data by the formula

-7 1 where a, b, and c, are actual values for

consecutive class intervals. After smoothing, the
data were transformed into percentages of montlily
catch. The resulting monthly distribution curves
of the combined data with the superimposed
mean-percentage curve for the 2 yeai-s calculated
in the same manner as for individual years is
shown in figure 3.

136

SEPTEMBER

FISHERY BULLETIN OF

I I I I l .,l I I J I I I I I II

THE FISH AND WILDLIFE SERVICE

LENGTH IN
CENTIMETERS

FiGt'RE 1. — Weight-freqiK'iicy (iistributions (in percentage)
of long-line catches of yellowfin tuna landed at Honolulu,
1948. Monthly frequency distributions are shown by
fine line, and mean monthly frequency distributions by
heavy line. Positive deviations from the mean are
shaded.

FEBRUARY

AUGUST 5

SEPTEMBER 5

OCTOBER 5

ooooooooot^oooooooogjoooooo

I'll I I — 1 1 1 1 1—

Figure 2. — Weight-frequency distributions (in percentage)
of long- line catches of yellowfin tuna landed at Honolulu,
1949. Monthly frequency distributions are shown by
fine line, and mean monthly frequency distributions by
heavy line. Positive deviations from the mean are
shaded.

AGE AND r.ROWTH OF YELLOWFIX TUNA

137

Figure 3. — Weight-frequency distributions (in pereentagej
of long-line anrl live-bait catches of yellowfin tuna
landed at Honolulu. Smoothed data of 1948 and 1949.
Monthly frequenc}' distributions are shown by fine line,
and mean monthly frequency distributions by heavy
line. Po.sitive deviations from the mean are shaded.

Initial examination of the plotted data in
figures 1 and 2 shows the presence of a modal
group of fishes which can be followed through most
months of both 1948 and 1949. The group was
designated .V for reference. In the 1948 data the
progression of the modes representing this group
indicates gradual growth until June, followed by
a 5-month period in which no growth is indicated.
Following this there appears to be a short period

of rapid growth from October through December.
From January through December, modal group A^
shows a gain in weight from 75 to i;}5 pounds, a
gain of 60 pounds in 1 year. Also present in the
plotted data is a smaller size group which becomes
evident in the long-line fishery in October 1948
and in December 1 949. This suggests the entrance
of a modal group 1 year younger than group A'^.

The 1949 data (fig. 2) presented a similar trend
in modal progression, except for the last 3 months
of the year where rather erratic modal peaks were
evident. Because the catches for these months
were not large in comparison to catches of the
summer months (table 1) any unusual distribu-
tions of weights of fish landed would cause erratic
modal peaks to appear in the percentage frequency
distributions.

Table 1. — Xumbers of yellowfin liina taken by long-line
fishing and auctioned at the Kyodo Fishing Company,
Ltd., Honolulu, in 1948 and 1949

Month

January

February...

March

April

May

June

July

August

September.

October

November.
December..

Total

1948

2,488

1»49

40

39

fil

73

45

20

60

67

97

158

3fi2

514

530

M5

M2

400

381

165

179

102

99

31

92

67

2,181

For a more detailed study of the combined data
of the 2 years, a criterion was set up to determine
what should be designated a mode and to designate
its position. . Modal peaks of positive deviations,
evident in the combined 2-ycar data, when plotted
as deviations from the mean curve (fig. 4) which
met either of the two following conditions were
treated as modes in this study:

(1) Any positive deviation of a class which
shows a difference of 0.5 or more from values of
both adjacent classes (fig. 5-A).

(2) Wlum the difl'erence between frequency
values of positive deviations of two adjacent
classes is less than 0.5, and when the frequency
values of the classes above and below these two
adjacent values are at least 0.5 less than the
adjacent values, the intersection of the extrapola-
tion of the lines connecting the two classes with
the adjacent classes was considered the position
of the mode (fig. 5-B).

138

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

This was done by the "transformation" method
of Walford (1946). This is a graphic method of
describing the growth of animals above the point
of inflection, the self-inliibiting phase of growth.

5.0

150 160 170 180
A

190 200

Figure 4. — Deviations of monthly frequency distribution
from the mean monthly frequency distribution (in per-
centage) for combined and smoothed 1948 and 1949 data. 4,0

Using the above criterion, values of modes were
selected as shown in figure 6. Each mode has
been labeled with the age group to which it was
presumed to belong. In order to plot modal
positions against successive months, January of
group A'^ was arbitrarily assumed to occur in
month 37. Thus the mode of group .A^ in Feb-
ruary, March, April, and so on, was plotted in
figure 5 against 38, 39, 40, and so on. Modes
corresponding to groups which are presumed to be
a year younger or older were then plotted 12
months above or below the month value corre-
sponding to group A'^.

Assuming group A'^— I to be 1 year younger than
A'^ and group 7V+I to be 1 year older, A^+II 2
years older, and so on, we proceeded to determine
whether a regular growth curve fitted the data.

200

B

FiGllRB

5.— Theoretical conditions demonstrating the
criterion used in selection of modes.

AGE AND GROWTH OF YELLOWFIN TUNA

139

Size of fisli in fi^curc (i was plotted in tcfnis of
l('i\<rlli nitlicr than wi'i^'-ht since tliis method of
filtin<x a fiiowth cui've is applicable to sizes above
the inflection point. It was obvious from a plot
in terms of wei<rhts ((i>r. 9) that the inflection
I)oint is within the ranfje of our data, whereas our
data in terms of length appear to be above the
inflection point.

P'or the growth of a number of species of animals,
Walford's graphic transformation method gives a
straight line when the lengths at age 1, 2, H, 4,
. . . 7i, reiiresented on the a: axis, are plotteil
against the lengths at age 2, :i, 4, 5, . . . n+1,
on the ?/ axis. This method assumes the growth
during each period to be of constant ratio to that
of the previous period. It has already been noted
that the modes make all their progress during half
the year and none in the remainder. This should
and does show as a stepwise or sinuous deviation
from the straight line. Also, this method requires
length values for each consecutive unit of time, in
this case for each month. Within the limits of
our data (fig. 6) there w-ere 28 months for which no
modal values were evident in the plotted data.
To furnish estimates of the missing values, linear
interpolations were made between observed
monthly values.

200

ISO

The series of actual values and interpolated
values was then smoothed twice by a running
average of three and resulting values of length at
age I) were [)lotted agairLst lengths at age n+1
where age is in months. The plotted data are
well fitted by the least-squares line }'=7.04 —
0.96.336 A^, where )' is length at age n + l, and X
is length at age /( (fig. 7). From this straight line
the upper limit of growth or the upper as\^mptote
can be derived according to Walford's method by
taking the point of intersection of the line fitted
to the plotted data and the line of no growth
represented by a line of slope 45° through the
zero point (fig. 7). In the case of the yellowfin tuna
data used herein, the value in length at the point
of intersection of the two lines is at 190.0 centi-
meters, which in terms of weight is equal to 294.9
pounds. A maximum weight of this magnitude
is within reason for this species; several specimens
approaching this limit have been taken in the local
flag-line fishery. The largest specimens included
in this study, however, were between 260 and 269
pounds.

Because the plot of n against '(+ 1 is a constant-
percentage rate' and not actual-length values, it is
possible to choose the point through which the
curve should be passed. As the period from

X

100

50

1 1

1

1

•

-1 o
o

3

«
•
••

1

1

•oo«

1

N +n
,00000000 •

N-

N -I

1

I

c

• •

o
o

•

1

1

1

1

1

1

10

15

20

25

30

35

40

45

50

55

60

65

70

MONTHS

FiGCRK 0. — Actual aiifi interpolated values in Iciintli plollcd against iiiontlis and sliowinn assisuod modal groups. Solid
points arc actual values and circles arc interpolated values. F'Votu coinhiricd and sniootlied 1948 and 1919 data.

953183 O - 51 - 2

140

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

-r

ZOO

LENGTH IN CMS AT AGE N

Figure 7. — Combined 1948 and 1949 length data are plotted by the method of VValford (1946) and fitted with a straight
line. The intersect of the straight line and the line at 45° through the zero point indicates the upper asymptote
of the yellowfin tuna. Points mariied by O are observed vahies.

month 37 through month 47 is the time group N
and is most evident in the plotted data, the mean
month and mean length of fish occurring in this
period were used as the initial point for computing
the relation between fish length and time.

The reconstructed growth curve of length on
time and the plotted values of the original modes
are shown in figure 8. Since figures 7 and 8
indicate that the position of plotted mode values
are well fitted oy the calculated growth curve,
this serves as verification of the assumption
that modal group N—1 is a year younger than

N, group N+I is a year older than N, and so on,
is correct. Since the original data were in terms
of weight, the calculated curve was also trans-
formed back to those terms. The growth curve
of weight on time is shown in figure 9.

From the results of figures 8 and 9, it is possible
to determine approximate age of fishes. Ex-
trapolation of the curves downward suggests the
origin of the fish to be in year A'^— III. Ex-
amination of the gonads of yellowfin taken in
local waters indicates the spawning period to be
centered about the summer months. Assuming

AGE AND GROWTH OF YELLOWFIN TUNA

141

tills to be true, the month of June may be selected
to represent the mean spawning period; thus,
the period from Juno A'— III to June A"— II
represents age group 0, or fish in their first year
of life, June A^— II to June N — I, age group I,
and so on. Owing to possible error in extrapolat-
ing the curves downward to the origin, the ages
thus assigned may not be quite correct. It is
felt, however, that ages through group IV cannot
be more than 1 year in error.

Sella (1929) states that bluefin tuna hatched in
June weigh 300 to 500 grams by September. This
is a weight of approximately 1 pound and would
fall very close to our growth curve as calculated.
Kishinouye (1923) says of the common tunny
{Thunnus orientalis), "such small individuals are
found in August and in September. Some of them
grow to a length of 30 cm. or more. By next spring
they grow to a length of ca 60 cm. When 2 years
old they are about 1 meter in length and 1 1 kg.
in weight." These values when plotted on our
curve are not much in disagreement. Specimens
of yellowfin tuna have been taken during the
month of December in Hawaiian waters weighing

2 pounds; these weights when plotted, also fail
very close to the curve of figure 9. Lengths and
weights by age groups may also be assigned from
figures 8 and 9 as has been done in table 2.

Table 2. — Lengths and weights hy age groups of yellowfin
tuna taken in Hawaiian waters determined hy the method
of growth analysis of Walford (1946)

.\ge group

Length in centimeters

Weight in pounds

I

54-103 .. ..

7-46.

II

103-136

46-108.

Ill

136-155 -..-

108-163.

IV

155-168

163-208.

DISCUSSION

In fairly close agreement with this study are the
observations of Schacfer (1948) of the yellowfin in
the waters off Central America, where modes in
length-frequency distributions were observed at
approximately 60 cm., 85 cm., and 115 cm. These
modes, when plotted against the assumed age and
the month at which the fish were taken, showed a
close similarity to the age-length curve of the
Hawaiian yellowfin (fig. 10). The conclusion of

AGE GROUP

200

150

X

o

-J

100

L_„

5 10

-m —

20

N-n-

25

30 35 40

MONTHS

N-I ! N

MODAL GROUPS

45

50 55 60
N+I L

65 70
N + H

Figure 8.-

-Cirowth curve of yellowfin tuna taken in Hawaiian waters fitted to lengths witli actual modal values in

length superimposed.

142

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

AGE GROUP

250

200

w 150

Q

■z.

o

a.

; 100

UJ

50

I

IT

m

IS

•

•

^

• •• •

/

1

i_- n-»«

• 1

•

1 1 1

1 1

1 1

1 1

10

N-m-

15

20

25

N-It-

30 35 40

MONTHS

N-L— L

45

50

N -

MODAL GROUPS

55

N+I

60

G5

70

N+tt

Figure 9. — Growth curve of yellowfin tuna taken in Hawaiian waters fitted to lengths and transformed into terms

of weight. Actual modal values in weight are superimposed.

150 I-

u 100

50

AGE GROUP
I 1

18 24

MONTHS

30

36

42

Figure 10. — Lengths of dominant size groups of yellowfin
taken in waters off Central America by Schaefer (1948)
plotted against calculated growth curve of Hawaiian
yellowfin.

Schaefer that the 60-cin. fish probably are 1 year
old and the 85-cm. fish a year older is also in close
agreement.

Our growth curve indicates that the yellowfin
tuna grows rapidly during at least the earher years
of life. Group N demonstrates a gain in weight
of approximately 60 pounds in 1 year. Aikawa
and Kato (1938) and Kimura (1932) have studied
age and growth of the yellowfin tuna in Japanese
waters. Aikawa and Kato assigned ages by the
study of marks on vertebral centra which they
considered to be annuli. The resulting age-weight
relation is shown in figure 11. In plotting these
data, which are from table 3, it was assumed that
the ma.ximum values were representative of the
end of the year of life because the length and
weight values for age group O were maximum
values. As the month of June has been used in
our study as being the approximate center of the

AGE AND GROWTH OF YELLOWFIN TUNA

143

AGE GROUP

Figure 11. — Growth in weight plotted against age for
Hawaiian yellowfin as compared to growth curves
calculated by Aikawa and Kate (1938) and Kimura
(1932).

spawning period, the maximum values as given by
Aikawa and Kato have been plotted for the
month of June, the assumed last month for any
age group. Regardless of the month of the year
these values are plotted against, the valu's for
any given age group differ greatly from the values
resultin£,- from our study of the Hawaiian yellowfin.

T,\BLE 3. — Age, length, and weight range of yellowfin
tuna from Japanese waters, from Aikaioa and Kato
(1938)

Age group

Length in
centimeters

Weight in
kilograms

Weight in
pounds

Less than 38

38 to 54

Le.ss than 1.5

l.S to 4.3

I...

3 3 to 9 5

H

54 to 70

70 to 85

4.3 to 8.6. . . .

9.5 to 19

in

8.6 to 14.0

19 to 30 9

IV

85 to 100

14.0 to 21.4

21.4 to 34.0

34.0 to 44.0

44.0 to 57.5

57.5 to 75.0

.10 9 to 47 2

V

100 to 115

VI .

115 to 130

7S to 07

VII

130 to 145

VIII

145 to 160

The results of Kimura's (1932) age-weight study
also are shown in figure 11. This study is based
on a few specimens taken over a long period with
no defined method of determining modal values
in frequency distributions. The presentation of
Kimura's data is based on values of weight taken
directly from his growth curve shown in figure 12.
Values were converted to pounds for comparison
with our data. This growth curve demonstrates
more rapid growth than the curve of Aikawa and
Kato hut still does not agree with the present
Hawaiian study.

Figure 13 gives growth curves of other species

of tuna taken from various areas in the world
compared to the growth curve of Hawaiian yellow-
fin. We have plotted these from the published
data. This graph shows no other tunas as having
a growth rate as rapid as that of the yellowfin tuna
of Hawaiian waters. The curve of bluefin tuna
of the Mediterranean Sea (Sella 1929) is based on
more than 1,500 vertebrae samples. This growth
curve, like the growth curve of yellowfin based on
vertebra-centra analysis (Aikawa and Kato 1938),
shows a very slow growth rate and infers a very
long-hved fish, for most of the plotted data are
below the point of inflection.

BODY WEIGHT
KG.

50

20

A-

V

A

/

J^

J'

^

n< Mtnni

IMllMUM

\iinmill

I a m IS T Tcr

AGE GROUP

FiatjRF. 12. — Growth curve of yellowfin tuna in Japanese
waters from Kimura (1932). Circles show average
weight of a large number of fish of roughly equal
weight taken at one time. Solid dots are weights of
single fish.

Aikawa and Kato (1938), in addition to their
study of the yellowfin, determined ages and growth
of the black tuna {Thunnus orientalis), the bonito
or skipjack {Katsuwonus vagans), and the albacore
(Germo germo) by vertebral-centra analysis. Be-
cause the skipjack and albacore are smaller species
of tuna not comparable to the yellowfin, they have"
not been included in the graph. The growth
curve of the black tuna, a species more comparable
in size, indicates a more rapid growth rate but the
curve has only the slightest suggestion of an in-
flection point. The growth curve of bluefin tuna
(bl^ck tuna of Aikawa and Kato, Thunnus orien-
talis) by Kimura (1932) from weight frequencies

144

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

350

300

o

z
=)
o

•± 150

100

50

^

BLACK TUNA

/

HAWAIIAN
YELLOWFIN /

/ /

m^

1 /^

/ /

/^SELLA
/^ BLUEFIN

/ KIMURAjf/ /
/ BLUEFIN / /

*yy^

r

1

^^i^

•^ — ^^

* BLACK TUNAOF AIKAWA
1

ni

AGE GROUP

■2L

■m

Figure 13. — Age-weight curves of tunas from waters off Japan and Mediterranean Sea compared to curve of Hawaiian

vellowfin.

demonstrates the most rapid growth but shows no
semblance of a point of inflection. As the curves
have been fitted to the data by eye, there may be
errors in the interpretation, but the curves show
the great variation in results of age and growth
studies of tunas.

Westman and Neville (1942), in a study of 751
length frequencies of bluefin tuna (Thunnus thyn-
nus) taken in waters off New York by both the
troll and chum fisheries, show the catch to be
made up of three distinct age groups. Ages were
assigned by scale readings. A comparison of size
of fish by ages with the Hawaiian -yellowfin study
shows more similarity than the curves indicate in
figure 13. Even so, the growth rate of the Atlantic
bluefin as shown by plotted data (fig. 14) is not
so rapid as yellowfin growth during the early years
of life.

150 r

100

50

AGE GROUP

18 24

MONTHS

30

36

42

Figure 14.— Lengths of dominant size groups of bluefin
tuna taken off Long Island, New York, by Westman
and Neville (1942), plotted against the calculated growth
curve of Hawaiian yellowfin.

AGE AND GROWTH OF YELLOWFIN TtTNA

145

In general, the results of our study of weight
frequencies of Hawaiian yeliowfin tend to disagree
with results of some studies of other species of
tuna and even with comparable yeliowfin studies.
Group A^, present in the Hawaiian long-line catches
of both 1948 and 1949, is with little doubt an age
group demonstrating a weight gain of about 60
pounds in the calendar year. Wliether or not our
conclusions about age are correct in other respects,
the yeliowfin tuna of Hawaiian waters undoubt-
edly is a rapid-growing species.

CONCLUSIONS

1 . The yeUowfin tuna {Neothunnus macropterus)
in Hawaiian waters is a rapid-growing fish demon-
strating at least during part of its life a growth of
approximately 60 pounds in one calendar year.

2. Positions of modes of size frequencies are
well fitted by a growth curve calculated by Wal-
ford's graphic transformation method, having an
upper asymptote at 294.9 pounds.

3. Extrapolation of the calculated curve down-
ward shows the spawning period in reference to
mode A^ to be in year A'^— III. If this interpreta-
tion is valid, mode TV is composed of fish which
were completing their third year of life and enter-
ing their fourth in the middle of the calendar year
of observation.

Using the customary designation of age groups
according to completed years of life, they would
be designated age group II until the middle
of the spawning season which occurs in the mid-
dle of the calendar year, and then become age
group III.

LITERATURE CITED

AiKAWA, HiROAKi and M. Kato.

1938. Age determination of fish (Preliminary Rept. 1).
Bull. Jap. Soc. Sci. Fi.sh., vol, 7, No. 1, pp. 79-88,
8 figs. In Japanese with English summary. Transla-
tion from the Japanese by W. G. Van Campen.

BONHAM, KeI.SHAW.

1946. Measurements of some pelagic commercial fishes
of Hawaii. Copeia, 1946, No. 2, pp. 81-84, 2 figs.
Brock, Vernon E.

1944. Contribution to the biology of the albacore
(Oermo alalunga) of the Oregon coa.st and other parts
of the North Pacific. Stanford Ichth. Bull., vol. 2,
No. 7, pp. 19-248, 19 figs.
JcNE, Fred C.

1950. Preliminary fisheries survey of the Hawaiian-
Line Islands area: Part I — The Hawaiian long-line
fishery. U. S. Fish and Wildlife Service, Comm. Fish.
Review, vol. 12, No. 1, pp. 1-23, 18 figs.

KiMURA, KiNOSUKE.

1932. Growth curves of the blue-fin tuna and yellow-
fin tuna based on the catches near Sigedera, on the
west coast of Prov. Izu. Bull. Jap. Soc. Sci. Fish.,
vol. 1, No. 1, pp. 1-4, 5 figs. In Japanese with
English summary. Translated from the Japanese by
W. G. Van Campen.

KlSHINOUYE, KaMAKICHI.

1923. Contributions to the comparative study of the

so-called scombroid fishes. Jour. College of Agric,

Imperial Univ. Tokyo, vol. 8, No. 3, pp. 293-475,

26 figs.
Okamoto, Gokozo.

1940. On the weight composition of skipjack schools

in the northeastern sea area. Bull. Jap. Soc. Sci.

Fish., vol. 9, No. 3, pp. 100-102, 2 figs. In

Japanese with English synopsis. Translation from

the Japanese by W. G. Van Campen.
Partlo, J. M.

1950. A report on the 1949 albacore fishery (Thunnus

alalunga). Fish. Res. Bd. Canada, Pac. Biol. Sta.,

Cir. 20, pp. 1-37.
Petersen, C. G. J.

1922. On the stock of plaice and the plaice fisheries in

different waters. A survey. Rept. Danish Biol.

Sta., vol. 29, pp. 1-36, Copenhagen.

SCHAEFER, MiLNER B.

1948. Size composition of catches of yeliowfin tuna
(Neothunnus macropterus) from central America, and
their significance in the determination of growth, age,
and schooling habits. U. S. Fish and Wildlife Service,
Fish. BuU., No. 44, vol. 51, pp. 197-200, 4 figs.
Sella, M.

1929. Migrazioni e habitat del tonno (Thunnus thynnus
L.) studiati col metodo degli ami, con osservazioni
su I'accrescimento sul regime delle tonnare, ecc. R.
Comit. Talasso. Ital. Memoir 156, pp. 1-24, 2 figs.

>

v>

146

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Snedecor, Georoe W.

1946. Statistical methods. Iowa State College Press,
Ames, Iowa. 4th Ed., xvi + 485.
Walford, Lionel A.

1946. A new graphic method of describing the growth
of animals. Biol. Bull., vol. 90, No. 1, pp. 141-147,
4 figs.
Westman, J. R. and P. W. Gilbert.

1941. Notes on age determination and growth of the
Atlantic bluefin tuna, Thunnus ihynnus (Linnaeus).
Copeia, 1941, No. 2, pp. 70-72, 3 figs.

Westman, J. R. and W. C. Neville.

1942. The tuna fishery of Long Island, New York.
Pp. 1-31, 12 figs. Board of Supervisors, Nassau
County, Long Island, New York.

APPENDIX

The following tables of data on yellowfin tuna
are those on which the figures and calculations in
the text are based.

Table A. — Weight frequencies of yellowfin tuna taken by
long-line fishing and landed at Honolulu during November
and December 1947

Class interval

70 to 79 pounds.. -
80 to 89 pounds.. -
90 to 99 pounds...
100 to 109 pounds.
110 to 119 pounds.
120 to 129 pounds.
130 to 139 pounds.
140 to 149 pounds.
150 to 159 pounds.
ItiO to 169 pounds.
170 to 179 pounds.
180 to 189 pounds.
190 to 199 pounds.
200 to 209 pounds.
210 to 219 pounds.
220 to 229 pounds.
2.30 to 239 pounds.
240 to 249 pounds.
250 to 259 pounds.
260 to 269 pounds -

Total.

November

December

Number of

tuna

landed

2

2

2

2

3

12

13

10

18

20

17

6

9

5

2

3

1
133

Table B. — Weight frequencies of yellowfin

tuna taken by long-li

ne fishing and

landed

at Honolulu d

iring 194S

Class interval

January

Febru-
ary

March

April

May

June

July

August

Septem-
ber

October

Novem-
ber

Decem-
ber

Number
of tuna
landed

1
1
2
2
5
6
9
2
I
8
3
11
8
7
5
5
6
5
4
1

1

1

1
1

3

6

1

1

5

2

2

6

31

55

45

39

25

37

44

19

25

19

16

8

1
2
3
2
3
3

10
8

18

10
8
5
6

10
4
2
2

6

1
7
4
2
4

4
1
1
4
3
3
3
1
1

1
3
8
4
3
2
3
6
5
8
6
5
2
4
1

1

1

2

4
4

7

20

34

24

18

17

11

12

5

8

7

1

3

21

2
4
7
3
4
1
4
6
5
4

2
3

8
19

15
9
6
3
8
9
3
1
2
4
3

I

16

80

90

60

25

40

30

51

34

29

30

18

15

3

2

2

1

31

6
13
54
68
45
29
30
24
24
24

9
13
17

3

3

3
10
41
71
59
53
46
49
49
40
46
37
21
11

3

45

90 to 99 pounds

1

9
3
11

8

8

4
3
2
2

79

268

110 to 119 pounds

361

272

130 to 139 pounds

218

140 to 149 pounds

199

198

160 to 169 pounds

216

170 to 179 pounds

147

1
1

142

190 to 199 pounds _

125

200 to 209 pounds

85

46

1

10

2

4

1

1
1

4

2

260 to 269 pounds....

1

1

Total

40

61

45

60

97

362

530

542

381

179

99

92

2,488

AGE AND GROWTH OF YELLOWFIN TXINA 147

Table C. — Weight frequencies of yellowfin tuna taken by long-line fishing and landed at Honolulu, 19/i9

Class interval

January

Febru-
ary

March

April

May

June

July

Auftust

Septem-

October

Novem-
ber

Decem-
ber

Number
o( tuna
landed

1

1

I

1

I

1

2

1
4

12
5

I
2

,1
7
4
1
4
8
3
6
5
5
3

1

1

2

6

1
2
2

5

1
1

3'

1
3

3
1
2
24
23
11
16
20
18

12
5
4
2
5
3
2

4
2
10
9
7
6
3
4
4
4
3
4
3
2

14

3
16
52
77
68
65
42
51
47
42
28
17
21
9
4
1

1

6

2

10

23

23

19

12

16

12

9

8

5

13

4

2

4

6

8

4

10

11

12

10

7

7

6

3

6

2

4

1

30

2

9
11
8
14
9
4
1
2
4
1
1

2
20
62
51
52
60
56
63
43
33
15
17
18
13
5
3

4

7
39
58
37
46
39
37
31
30
17
20
20
10
2
1

57

90 to 99 pounds ...

2
2
2
9

1

3

1
4

I

2"

109

2
1

I
4
1
1
2
2

217

110 to 119 pounds

249
238

130 to 139 Dounds

251

140 to 149 pounds

150 to 159 pounds

191
199
ISS

170 to 179 Dounds

144

180 to 189 pounds

1

84

190 to 199 DOunds

7C

1

82

1

1

45

1
1

1

17

6

1

2

1

1

Total

39

73

20

67

158

514

545

400

165

102

31

67

2,181

Table D. — Weight frequ

incies of yellowfin tuna taken by long-line fishing and landed

at Honolulu, 1948 and 1949 combined

Class interval

January

Febru-
ary

March

April

May

June

July

August

Septem-

October

Novem-
ber

Decem-
ber

Number
of tuna
landed

I

1

1

3

2

9

8

19

11

8

14

6

15

12

11

8

9

9

7

4

2

2

1

2

1
1
I
4
6
12
4
5
1

7
8
4

I

3

8

1
5
19
9
2
6
2
5
5
2
5
5
5
3
1
2

1
3
10
23
11
7
3

14

8
14
11
10
5
4
1
1

1

3

3

5

32

42

28

25

26

21

15

21

g

5

4

9

6

2

1

1

2
2

1

5

3

8

8

41

78

68

58

37

53

56

28

33

24

29

12

2

2

1

2

3

2

5

5

12

17

19

11

11

6

10

11

4

4

2

1

1

2

1

12

1
1
2
10
20
11
25
17
12
8
6

3
3

4

8

7

15

24

44

35

30

27

18

19

11

11

13

3

7

1

35

2

6

32

132

167

128

90

82

81

98

76

57

47

39

24

7

3

2

1

61

80 to 89 pounds

8

33

116

119

97

89

86

87

67

57

24

30

35

16

8

3

7

17

80

129

96

99

85

86

80

70

63

57

41

21

5

1

1

102

188

100 to 109

485

610

120 to 129 pounds

510

130 to 139 pounds

469

390

150 to 159 pounds

397

160 to 169 pounds

381

170 to 179 pounds

291

180 to 189 pounds

2
1

226

195

167

210 to 219 DOunds

91

1

27

10

1

6

1

3

260 to 269 pounds

1

1

Total -. -

79

134

65

127

255

876

1.075

942

546

281

130

159

4.669

Table E. — Weight frequencies

f yellow

fin tuna taken by live-bait fishing and trolling and landed at Honol

ulu during 1949

Class interval

January

Febru-
ary

Marcb

April

May

June

July

August

Septem-

October

Novem-
ber

Decem-
ber

Number
of tuna
landed

22
1
1

15

54
1

76

6
1

3

1

12

1

I
13

4

30 to 39 pounds

2

i

1

32

Total

7

3

1

14

39

57

1

2

124

148

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Table F. — Weight frequencies of yellow fin tuna taken by long-line and live-bait fishing and landed at Honolulu during I948

and 1949

Class interval

to 9 pounds

10 to 19 pounds

20 to 29 pounds- --
30 to 39 pounds.-.
40 to 49 pounds...

50 to 59 pounds

60 to 69 pounds...
70 to 79 pounds...
80 to 90 pounds...
90 to 99 pounds...
100 to 109 pounds.
110 to 119 pounds.
120 to 129 pounds.
130 to 139 pounds.,
140 to 149 pounds..
150 to 159 pounds.
160 to 169 pounds..
170 to 179 pounds..
180 to 189 pounds.
190 to 199 pounds..
200 to 209 pounds..
210 to 219 pounds..
220 to 229 pounds..
230 to 239 pounds..
240 to 249 pounds. -
250 to 259 pounds..
260 to 269 pounds..

Total

January

Febru-
ary

137

March

66

April

May

1
294

8
33
116
119
97

933

July

32

132

167

128

90

82

81

98

76

57

47

39

24

7

3

2

1

1,076

August

7

17

80

129

96

99

85

86

80

70

63

57

41

21

5

1

1

944

Septem-
ber

October

Novem-
ber

130

Decem-
ber

Number
of tuna
landed

76
12

12

35

61

102

188

485

610

510

469

390

397

381

291

226

195

167

91

27

10

6

3

Table G. — Weight frequencies of yellowfin tuna taken by long-line and live-bait fishing during 1948 and 1949 as percentages

of monthly catch with mean frequency distribution in percentage

Class interval

to 9 pounds

10 to 19 pounds

20 to 29potmds

30 to 39 pounds....

40 to 49 pounds

50 to 59 pounds

60 to 69 pounds....

70 to 79 pounds

80 to 89 pounds

90 to 99 pounds....
100 to 109 pounds.,
no to 119 pounds..
120 to 129 pounds..
130 to 139 pounds..
140 to 149 pounds.
150 to 159 pounds..
160 to 169 pounds..
170 to 179 pounds..
180 to 189 pounds..
190 to 199 pounds..
200 to 209 pounds..
210 to 219 pounds..
220 to 229 pounds..
230 to 239 pounds..
240 to 249 pounds..
250 to 259 pounds..
260 to 269 pounds.

Janu-
ary

7.0
2.3

1.2

5.8
22.1
10.5
2.3
7.0
2.3
5.8
5.8
2.3
5.8
6.8
5.8
3.5
1.2
2.3

Febru-
ary

2.2

0.7

0.7
2.2
7.3

16 8
8.0
5.1
2.2
5. 1

10.2
5.8

10.2
8.0
7.3
3.6
2.9
0.7
0.7

March

1.6

1.5
1.5
1.5
6.1
9.1
18.2
6. 1
7.6
1.5
10.6
10.6
12. 1
6.1

3.0
1.6

1.5

April

0.7
9.2
0.7

0.7

0.7

1.4

7. 1

14.2

7.8

17 7

12.0

8.6

5.7

4.2

5.0

2.1

2.1

May

7.5
0.3
0.3
5.1

0.3
1.0
1.0
2.6
10.9
14.3
8.8
8.5
8.8
7. 1
5. 1
7.1
2.7
2.6
1.4
3.1
2.0
0.7

0.3

June

5.8
0.1

0.2
O.'i'

0.8
3.5
12.4
12.8
10.4
9.5
9.2
9.3
7.2
6. 1
2,6
3.2
3.8
1.7
0.8
0.3

July

0.1

0.2
6
3.0
12.3
16.5
11.9
8.4
7.6
7.5
9.1
7.1
5.3
4.4
3.6
2.2
0.6
0.3
0.2
0.1

August

0.2
0.2

0.7
1.8
8.5
13.7
10.2
10.5
9.0
9.1
8.5
7.4
6.7
6.0
4.3
2.2
0.5
0.1
0.1

Sep-
tember

0.2

0.9

0.6

1.5

1.5

7.5

14.3

12.4

10.6

6.8

9.7

10.3

5.1

6.0

4.4

5.3

2.2

0.4

0.4

October

1.

1.4

2.8
2.5
5.3
8.5
15.7
12.5
10.7
9.6
6.4
6.8
3.9
3.9
4.6
1.1
2.5
0.4

No-
vember

0.8
1,5
2.3
1,5
3.8
3,8
9,2
13.1
14,6
8,5
8,5
4.6
7,7
8.5
3, 1
3,1
1,5
0,8
'1.8
..6
0.8

De-
cember

0.6
0.6
1.9
1.3
5.7
5,0
11.9
6.9
5.0
8,8
3.8
9.4
7.6
6.9
5,0
5,7
5,7
4.4
2.5
1,3

Mean

1,1
0.8
0,4
1.3
0,4
0.5
1,7
4,0
5,0
6.0
8.7
9.9
9.4
10.1
7.7
8.0
6.9
5.3
4,4
3,3
2.5
1.4
0.5
0.2
0.2
0.1

AGE AND GROWTH OF YELLOWFIN TTJNA 149

Table H. — Time and position of recognized and interpolated modes from the combined 1948 and 1949 data

Month

May

June

July

August

September.

October

November.
December.
January...
February . .

March

April

May

June

July

August

September.

October

November.
December.
January...
February..

March

April

May

June -.

July

Number

Observed
length, in
cenllmeters

47.2
47.2

93.0
93.0

125.3
120.2
125.3
130.1
142 6
134.5
138.7
138.7

Interpolated
length, in
centimeters

50.4

56.8
60.0
63.2
66.5

77.5
85.2

97.6
102.2
106. 8
111.4
116
120.7

Month

August

September.

October

November.
December.
January. ..
February..

March

April

May -.

June

July

August

September.

October

November.
December.
January. ..
February.,

March

AprU

May .

June

July

August

September.

Number

Observed
length, in
centimeters

138.7
14U.3
138.7
146.3

156.4
152.1

152 4
158.2

156.4

162.5
163.1

167.6

Interpolated
length, in
centimeters

149.7
153.0

152 2
152.3

157.3

163.6
164.1
164.6
165.1
165.6
166.1
166.6
167.1

o

UNITED STATES DEPARTMENT OF THE INTERIOR, Oscar L. Chapman, Secretary
FISH AND WILDLIFE SERVICE, Albert M. Day, Director

STUDIES OF GEORGES BANK HADDOCK

Part I: Landings by Pounds, Numbers,
and Sizes of Fish

By Howard A. Schuck

FISHERY BULLETIN 66

From Fishery Bulletin of the Fish and Wildlife Service

VOLUME 52

UNITED STATES GOVERNMENT PRINTING OFFICE . WASHINGTON : 1951

For sale by the Superintendent of Documents, U. S. Government Printing Office, Washington 25, D. C.

Price 20 cents

CONTENTS

Page

Introduction 151

Fishing banks and areas studied 152

Organization of study 153

Development of data 153

Ports of landing 153

Categories of fish 156

Seasons 157

Segregating landings by subareas 157

Pounds of haddock landed 157

Average weights of haddock landed 159

Numbers of haddock landed 162

Size compositions of haddock landed 162

Scrod haddock 164

Large haddock 164

Total haddock 164

Undersized haddock 166

Scrod versus large haddock 166

Discussion and summary 174

Literature cited 176

STUDIES OF GEORGES BANK HADDOCK

Part I: Landings by Pounds, Numbers, and Sizes of Fish

By Howard A. Schuck, Fishery Research Biologist

The haddock, Melanogrammus aeglefinus, has
been New England's most valuable fishery re-
source, and one of the most important in the
United States, for nearly three decades. In the
early days, this fish was little sought and the
annual New England catch was small — only about
40-odd million pounds until well into the 1900's.
With the development of filleting and freezing
methods the market for haddock grew, and during
the 1920's New England landings increased
greatly. They reached a peak of about 250
million pounds in 1929, but after that production
declined rapidly.

From Georges Bank, source of most United
States haddock, production dropped from about
223 million pounds in 1929 to 115 million pounds
in 1931. In addition, an index of abundance
indicates that the size of the stock on Georges
Bank declined greatly over these years.

The decline of haddock landings and abundance
aroused concern in the fishing industry, and in
1930 funds were made available to the United
States Bureau of Fisheries (now the Fish and
Wildlife Service) to study the haddock and the
haddock fishery. The general purposes of the
investigation were to determine (1) what caused
the decline of the fishery in waters fished by
United States fishermen, (2) what could be done
to increase abundance and production, or at least
to prevent them from decreasing further, and (3)
what predictions of future production were
possible.

During the years 1931-48, a large quantity of
data was collected, partly at sea but mostly at
the important haddock ports (Boston, Gloucester,
and New Bedford, Mass., and Portland, Maine)
where collectors and interviewers have worked
systematically since 1931. These data, the basis
of this and other papers, were obtained with the
cooperation of fishermen at sea and of boat owners,
dealers, and fish handlers — especially those on
the Boston Fish Pier (fig. 1).

William C. Harrington, in charge of the Haddock
Investigation from 1931 to 1947, planned the col-
lection of these data obtained in various years
during the period 1931-48 by many employees
of the Fish and Wildlife Service. Among these
were H. M. Bearse, F. E. Firth, D. F. Hammack,
J. J. Miggins, J. M. Shuval, and J. R. Webster.
Assisting in tabulating and summarizing data at
various times during the years 1945-49 were
E. L. Arnold, Jr., F. A. Dreyer, Dorothy B.
Monahan, Elizabeth V. Nugent, E. S. Phillips,
S. L. Cogswell, and L. D. Stringer.

At sea, data were collected on commercial fishing
vessels; on the Atlantis, a research vessel leased
from the Woods Hole Oceanographic Institution;
and on the fishery-research vessels Albatross II
(1931 and 1932) and Albatross III (beginning in
1948). Most of these data were collected to deter-
mine how to protect small haddock, destroyed in
large numbers by the otter-trawl (fig. 2) fleet.
Line trawlers (fig. 3) were used in the early days
of the haddock fishery, but now only two are oper-
ating out of Boston, Mass., the major haddock
port. Results of these studies on the small had-
dock situation were reported by Herrington (1933,
1935, 1936, 1941).' In addition, a small amount of
tagging was done to determine migrations and
interdependence of populations. Most of this
work remains unreported, but one publication refers
to phases of it (Rounsefell 1942). And since the
commissioning of the Albatross III in 1948,
further experiments on mesh sizes, studies of sur-
vival of young haddock that escape through larger
mesh, some tagging, and a census of the population
of all ages of haddock have been undertaken.

At the important haddock ports considerable
quantities of data were obtained. These data arc
largely unreported, although contributions of
Herrington (1944, 1948) and Schuck (1949) have
presented segments of them and certain condu-

' Publications referred to parenthetically by date are listed in the Litera-
ture Cited, p. 176.

151

152

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

ttJI''H2l1HDt«rh

Figure 1. — Part of the Boston Fish Pier, where most of
the United States production of haddock is landed.

Figure 2. — Modern otter trawler: predominant type of
vessel in the present-day New England haddock
fishery.

Figure 3. — Line trawler; prudoniiuant type of vessel in
the early years of the New England haddock fishery.

sions regarding the fishery. At the ports, since
1931, the following data have been collected:

(1) Almost complete records of the poundages
landed from various banks, with records of depths
and locations from which the fish were taken, the
gear used, and the days actually spent fishing;

(2) randomized samples of the lengths of fish in the
landings; (3) selected samples of scales; and (4)
length-weight data.

FISHING BANKS AND AREAS STUDIED

The United States haddock fishery has depended
upon Georges Bank and the Nova Scotian banks.
To the north of these banks, haddock are found,
but are little fished by United States fishermen.
To the south, haddock are not found, except for
stragglers.

Georges Bank is the most important area for
the United States haddock fishery, with about 67
percent of the total United States landings coming
from this area during recent years (1931 to 1948).

The haddock on Georges Bank are apparently
a relatively distinct and homogeneous stock.
Present knowledge indicates that the Fundian
Channel, which separates Georges Bank from the
Nova Scotian banks, is a natural barrier to the
intermigration of bottom-living stages of haddock.
Evidence of this comes from studies of size com-
positions, growth rates, tagging, and vertebral
counts. The size composition of the stock and
the sizes of haddock of various ages on Georges
Bank are decidedly different from those on Browns
Bank across the Fundian Channel (Needier 1930,
Schuck and Arnold in press). Although the num-
ber of tagged haddock is not large, there is no
evidence from the returns that any of them crossed
this channel (Needier 1930, Schroeder 1942,
United States Fish and Wildlife Service unpub-
lished data). There is a seasonal migration in the
spring from Georges Bank north along the coast of
Massachusetts and Maine as far as the Bay of
Fundy and a return to Georges Bank in the fall,
but very few haddock are caught on this northward
migration.

Because, first, the Georges Bank area was the
most important for the United States haddock
fishery and, second, the haddock on Georges Bank
formed a relatively distinct population and, third,
haddock production from this bank had declined
more seriously than production from the Nova
Scotian banks, we decided to study first the

GEORGES BANK HADDOCK PART i: LANDINGS

153

Georges Bank haddock — before the Nova Scotian
haddock.

The Georges Bank region comprises most of
International Area XXII, shown in figure 4.
International Area XXII was established by the
North American Council en Fishery Investigation
when the western North Atlantic Ocean was
divided along natural, political, and ecological
lines. By Georges Bank we mean specifically the
following subareas (fig. 5) of Area XXII:

International
subarea

1. Northern Edge and Northeast Peak J

2. Southeast Part of Georges M

3. Southwest Georges N

4. South Channel and Nantucket Shoals G, H, O '

' Data include very small quantities from subareas Q. R. and S.

The manner by which these subareas were
established is described by Rounsefell (1948).

ORGANIZATION OF STUDY

Russell (1942) has expressed the dynamics of a
fish population by the equation

S, + (0+R)-{C+N) = S2
where

51 = size of population at the beginning of the
year,

G= additions to the population during the year
by growth,

i?= additions to the population by recruitment
of young fish,

C= deductions from the population during the
year by fishery,

N = deductions from the population during the
year due to natural mortahty,

52= size of population at the end of the year.

The main problems, as we see them, are (1) to
obtain accurate measures of the various quantities
expressed in this equation for each year, (2) to
determine what effect variations of catch, natural
mortahty, growth, and recruitment have had on
the size of the stock, (3) to determine what effect
variations in the size of the stock have had upon
each of these factors, and (4) to show what effect
other factors in the environment (hydrographic
conditions and stocks of other species of competing
fishes) have had upon (a) the size of the stock and
(6) the four factors — catch, growth, recruitment,
and natural mortality.

With this information at hand, if the relative
effects of the fishery and of the environment on

the stock are sufficiently clear, it should be possible
(1) to predict the abundance and production of
haddock, and (2) to determine what measures, if
any, would maintain or increase the catch of
haddock from the important populations.

Most of the material in this series is devoted to
solving these problems. The purpose of the re-
mainder of the present paper is restricted to deter-
mining the total landings of Georges Bank haddock
for each season and year, 1931 to 1948, in terms
of pounds, numbers, average weights, and numbers
of each size.

Obtaining "total" values impHes adding together
not only those portions of the landings of the
various ports that originated on Georges Bank,
but adding together also data for two artificial
market categories, the limits of which vary from
season to season, from year to year, and among
different areas of the bank.

Where we refer to totals we refer, of course, to
our best estimate of such values. All such values
are subject to a certain amount of error due to
limitations in collecting and assembling statistics
and to sampling error.

The values developed in this paper represent
landings but not catches because the smallest
sizes of haddock are discarded at sea as they lack
sufficient marketable value to be brought to port.

DEVELOPMENT OF DATA
Ports of landing

Haddock are caught in North American waters
by fishermen from New England, New York,
Canada, Newfoundland, and various European
countries.

Canadian and Newfoundland landings were ex-
cluded from this study, as no records could be
found to indicate that any of their haddock were
caught in the Georges Bank area. McKenzie
(1946) has shown that all Canadian haddock
landings for the years 1938 to 1940 came from
banks to the north and east of Georges Bank.
Herrington (unpublished manuscript) lists all
Canadian landings for the years 1918 to 1940 as
having originated from banks other than Georges.

European fishermen, mainly interested in cod,
frequent the Newfoundland banks and the most
easterly of the Nova Scotian banks. Records
show that Europeans fished on Georges Bank
during early years, but not during the years
covered in this summary.

154

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

_^_^ ____^ — ^

North Amirican Council on FisHWYlNvtSTHATiONS |

CHART NttL (RtVISLD I9J6) 1

STATISTICAL AREAS

ATLANTIC COAST OF NORTH AMLRICA

Number

Region

XIV

EasKoasf of Greenland

IT

WeslCocsl of Greenland

im

Hudson

IVM

Labrador

W

Eosf Coasf of Newfoundlond

Gulf of Sh Lawrence

JL

New/oundrand BanKt

xc

Novo Scoha

n\\

New England

Middle AnanHc S^a^es

XXUI

my Soufh AHanhc Sfofes |

IIV

Gulf of Mexico 1

TTVr Bermuda

XlVll Wesr Indies and Bahamas

HVnLesser AnHlles

I

20'

90° 85° 80° 75° 70" 65° 60° 55° 50° 45* 40° 35° 30°

Figure 4. — International statistical areas off the Atlantic coast of North America.

25°

GEORGES BANK HADDOCK — PART i: LANDINGS

155

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156

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Thus United States fishermen were the only
ones to land haddock from Georges Bank. How-
ever, we could not use the total of all United
States landings of haddock for this study because
United States fishermen took varying quantities
of haddock from other banks as well as from
Georges.

Inasmuch as Georges Bank lies at a considerable
distance off shore, it is exploited mainly by large
vessels. These vessels land at only a few ports
where, for the most part, accurate records have
been kept on the origin of haddock landings.
Thus for Boston and Gloucester we were able to
determine the quantities of haddock landed from
Georges Bank each year. We included also in
our tabulations the quantities of Georges Bank
haddock landed at Portland, Maine, during the
years 1931 to 1946. And beginning in 1942,
landings of haddock at the port of New Bedford
became quite large, so the New Bedford landings
of Georges Bank haddock for the years 1942 to
1948 were included. As almost all haddock
landed at New York City are taken from the
Georges area, the total of that port's landings for
all years also were included. We included also the
total landings for Groton, Conn, for 1931 and
1932 — landings at this port were negligible after
1932. To these quantities, we added the entire
amount of haddock landed on Cape Cod, which
lies next to Georges Bank. This is the only area
where small boats land Georges Bank haddock,
and almost all landings there are from Georges.

The sums of these quantities we have accepted
as the total poundages ^ of haddock originating in
the Georges area that were landed and sold.

Categories of fish

Immediately after capture at sea, haddock are
separated into two market categories, scrod and
large. This division of the catch makes it
necessary to collect complete data on each market
category and later to combine the data to obtain
total statistics for the species haddock.

As defined by the New England Fish Exchange,
scrod haddock (scrod) are those weighing from 1 K

' Sources of data are the former U. S. Bureau of Fisheries and the present
U. S. Fish and Wildhfe Service publications. "Current Fishery Statistics"
for all years, and unpublished records of various fish companies a.ssembled by
William C. Henington.

to 2K pounds (gutted weight), and large haddock
are those weighing more than 2^ pounds. These
definitions are only approximate owing to varia-
tions in culling and to a practice of marketing, as
scrod, many fish weighing less than IK pounds.

We have tabulated records of the landings for
both market categories, large and scrod, for all
years. Small amounts of "mixed" haddock were
added to scrod in New Bedford. When OPA price
control regulations were in effect (which allowed a
higher price for "large" haddock). New Bedford
landings showed an artificial scarcity of scrod and
an overabundance of large. For the period July
1943 to June 1946, therefore, we used the percent-
age that scrod made up of the monthly total of
scrod and large for the ports of Boston, Gloucester,
and Portland, from any subarea in any month, to
estimate the proportion of scrod in the New
Bedford landings from these same subareas in that
month.

Where we refer to "undersized" haddock we
mean those less than IK pounds, the lower limit of
the market category of scrod, although at present
there is no State or Federal regulation that
classifies such fish as imdersized. When we refer
to "total haddock" or merely "haddock", we
mean the total of all haddock regardless of market
category.

Most haddock are landed as drawn or gutted
fish, but some are landed in the "round". Where
poundages of fish in the round were obtained, they
were reduced by 15 percent. Thus all poundages
are in terms of gutted fish.

Landings of large haddock in the round were
negligible but landings of round scrod were more
numerous and were of two types, (1) regular-sized
scrod that were left ungutted because of rough
weather or gluts of fish on deck, and (2) unusually
small-sized scrod, or baby scrod. Landings of
baby scrod became unusually large in the winter
of 1940, owing to a scarcity of large haddock and
a high abundance of baby haddock (year class
1939).

The landings of baby scrod from the winter of
1940 to the summer of 1943 were considered to be
so large that in the initial steps of the analysis
they were treated separately from scrod or large
haddock. These landings of baby scrod amounted
to approximately the following:

GEORGES BANK HADDOCK— PART i: LANDINGS

157

Thousand.^

Year 1940: of pounds

Fall 33

Winter 1 , 097

Year 1941:

Spring 3, lo3

Summer 1, 683

Fall - 913

Winter 339

Year 1942:

Spring 239

Summer 380

Fall 275

Winter 362

Year 1943:

Spring 2,212

Summer - 429

Fall 25

Seasons

A "haddock year" is the summation of spring,
simimer, fall, and winter seasons, and differs from
a calendar year by one month. These seasons are
as follows:

Months

Spring February, March, April.

Summer May, June, July.

Fall August, September, October.

Winter November, December, January (of

following year).

These seasons agree with the Georges Bank
haddock life-cycle better than any other 3-month
grouping, for the months of February, March, and
April constitute the spawning period. During
these months the size and age composition of the
catch is considerably different from that of each
of the other seasons.

All data were collected initially on a monthly
basis, then assembled into seasons, and then into
haddock years.

Segregating landings by subareas

Inasmuch as different sizes of haddock are
caught on various parts of Georges Bank, we
wished in the initial steps of development of the
data to segregate the landings by subareas. For
the ports of Boston, Gloucester, New Bedford,
and Portland, accurate information was obtained
on the amounts of haddock landed from each
subarea. These ports received the bulk of the
total landings (88 percent for all years), thus we
allotted the remainder of the landings to subareas

on the basis of the subarea contribution at these
ports.

The subareas shown in figure 5 were in use from
1939 through 1948. In the years before 1939,
there were several different systems of naming
and segregating the various sections of Georges
Bank. The data from earlier years, therefore,
were arranged to conform, as much as possible,
to the modern subareas. One exception should
be noted, however. During the years 1931
through 1935, published statistics furnished a
breakdown by only (1) South Channel and Nan-
tucket Shoals, and (2) the rest of Georges Bank
proper — roughly J, M, and N of the modern
terminology.

In all tables showing pounds and numbers of
fish, values were rounded off to the nearest
thousand. Total as well as individual values
were rounded off. Thus, individual values do
not add up exactly to the totals in some cases.

POUNDS OF HADDOCK LANDED

Table 1 shows the pounds of scrod and large
haddock landed from the four subareas of Georges
Bank bj" seasons and years, from 1931 through
1948. Whether particular subareas of Georges
Bank contributed more or less haddock in recent
years can be studied through this table. Their
importance, relative to one another, is shown in
table 2 (percent contribution by years, 1936-48
only). The landings are summarized, by seasons,
for scrod in table 3, for large in table 4, and for
total haddock in table 5. Landings by years only
are shown also in tables 3,4, and 5, and in figure 6.

■43 44 45 46 47 46

Figure 6. — Pounds of scrod, large, and total haddock
landed from Georges Bank, 1931 to 1948.

954715 O - 51

158

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Table 1. — Scrod and large haddock landed, by subareas and
by seasons, 1931 to 1948

[In thousands of pounds]

Table 1. — Scrod and large haddock landed, by subareas and
by seasons, 1931 to 1948 — Continued

(In thousands of pounds]

Year 1931:

Spring

Summer

Fall

Winter

Year 1932:

Spring

Summer

Fall

Winter -

Year 1933:

Spring

Summer

Fall

Winter

Year 1934:

Spring

Summer

Fall

Winter

Year 1936:

Spring

Summer

Fall

Winter

Total, 1931-35:

Spring

Summer

Fall

Winter

Year 1936:

Spring

Summer

Fall

Winter

Year 1937:

Spring

Summer

Fall

Winter

Year 1938:

Spring

Summer

Fall

Winter

Year 1939:

Spring

Summer

Fall

Winter

Scrod

North-
ern
Edge

South-
east
Part

South
west
Part

'705

'850

'3,997

'8,613

' 4, 702
'6,797
' 10, 808
'3,226

'3,441
'3.010
> 7, 725
' 1, 245

' 2, 525
' 5, 042
'1,655

'769
'4,802
'9,509
' 8, 037

1 10, 505
' 17. 984
'37,081
'22,776

2,478

3,438

11,368

1,045

875
4,235
1,216
1,816

4,489
5,476
10, 207
1,114

816
1.204
1,246

536

1,680
6,260
13,086
2,313

1.662

966

1,306

2,485

993
4,298
8,592
1,843

3,611
2,900
1,081
1,682

31

375

96

11
185
44
36

151
32
20

173

181

458

296

South

Chan

nel

189

405

1,269

1,473

2,253

1,940

991

796

675

1,510

906

286

717
963
996
190

194

915

1,045

266

4.028
5.733
5,207
3,011

1,556
349
584

198
1,558
3,168

797

814
1,724
6,002
2,233

2,739
4,087
8,043
2, 322,

Large

North-
ern
Edge

South
east
Part

South
west
Part

'24,400
> 18, 822

1 13, 629
'7,637

'8,860
' 14, 006
'16,126

'8,420

' 14, 455

' 12, 056

' 14, 465

'2,542

'4.190
'7,536
' 7. 872
'2,413

' 4, 345

1 14, 861
1 13, 639
'11,082

'56,240
' 67, 280
'65,731
'32,094

7,620

6,440

13, 382

1,892

3.664

6,475

883

2,425

15, 665
9,326

10, 147
3,346

2,562

2,109

706

1,065

5,853
8.162
6.404
2.173

5,670

1,721

639

2,077

2.609
6.831
8,758
2.617

7.747

3.841

834

2.294

235

293

213

168

506

18

126

566

166

13

314

364

978

283

South
Chan-
nel

5.211
14. 788
10. 198

2.854

9.286
5.528
7,177
4,514

3,912
8,659
5,030
1,723

3.071

6.418

4.908

501

821
3.762
4.402

732

22. 301
39, 155
31,715
10. 324

2,309
5,010
2,094
2,133

1,320
5,490
6.776
5.062

3.194
6.598
6.878
4.162

5.091
6,468
7.784
4,911

Season

Year 1940:

Spring

Summer. --

Fall

Winter

Year 1941:

Spring

Summer

Fall

Winter

Year 1942:

Spring

Summer

FalK_

Winter

Year 1943:

Spring

Summer. .

Fall

Winter

Year 1944:

Spring

Summer

Fall

Winter

Year 1945:

Spring

Summer

Fall

Winter

Year 1946:

Spring

Summer

Fall

Winter

Year 1947:

Spring

Summer

Fall

Winter

Year 1948:

Spring

Summer

Fall.

Winter

Total. 1936-48:

Spring

Summer.. -

Fall

Winter

Scrod

North-
ern
Edge

2.156

3. 165

4.535

176

1.916

2.200

8.553

210

3.445

8.462

4.595

404

1.894

3.991

3.170

94

732

2,256

2,286

85

122

322

1,801

7

15

2.497

2.506

412

1,105
2,793
9,936
1,048

2.594
6,523
9.925
4.232

23. 619
49.680
90,568
12,983

South-
east
Part

1,429
2,608
1,407
1.271

4,042
4,698
6,161
3,318

4,892
.3,780
3,783
2,150

8,562

4,937

4.083

372

2.678

1,289

1.963

423

743
1.185
1.660

250

681
1.876
1.546
1.660

3.906
1.242
1.367
1.866

1.692
1,064
1.998
3.824

35.689
31.884
28.797
21. 553

South
west
Part

7

639

28

1,532

883
1,697

421
1,636

138

630

276

3,390

372

960

231

1,078

278

669

39

340

52

623

990

1,469

26
548
110
217

288

959

63

242

210

1,432

32

360

2.628
9.207
2.253
10,853

South
Chan-
nel

3,022
3,081
3,537
1,107

4,773
4,983
5,941
2,342

3,009
4,154
5,104
1,269

790
4,019
2,548

406

290

1,272

536

116

123
853
990
484

287
2,294
4,985
1,560

338
3,343

9,618
2,902

1,680
4,660
4,027
1,323

18, 551
36, 574
54.747
17, 344

Large

North-
em
Edge

4,634
6,417
8,146

2,697

4,380

7,066

264

3.746

8.221

4,947

619

3,296

3,769

4,909

160

3,262

8,215

9,811

509

3,778

3.210

6.934

148

2.871

9. 2.38

9,897

851

4,884

4,644

7,279

666

5,764
3,519
5,786
2,874

66,577
82, 372
103, 456
16,507

South
east
Part

4,713
6.062
1.797
2,508

12. 139
7.619
2,602
2,343

9,531
4.202
1.304
1,452

8.791

4.160

2.769

655

8,807

South-
west
Part

5.373
1,717

7,029

2,296

2,369

866

6,707
4,118
3,690
6,302

11,914

2,111

1,148

836

3,113

678
1.245
1.649

92. 387
47.410
25. 259
26, 179

63
1,!

33
2,010

866
2,738

287
1,397

456

914

181

2,416

469

1,618

415

1,762

5,616

172

5,271

776
4,511
1,387
5,024

1,749

2,922

372

1,329

1,280

3,147

71

461

218

1,868

14

South
Chan-
nel

6,353
7,727
6,514
3,572

4,072
9,071
6,017
4,515

3,138
6,963
6,484
3,138

1,647
8,232
7,292
1,814

2,479
11,093
9,292
4,347

3,060
10, 302
8,570
6,337

1,722
11,547
14,644

5,807

1,616
9,288
9,170
5,856

3,716
6,733
7,102
4,201

8.962 39.716

27. 265

2.963

21,413

103.522
97.617
55,856

' Pounds shown for 1931 to 1935 are combined for Northern Edge, South-
east Part, and Southwest Edge.

Table 2. — Percentages of scrod,

large,

and total Georges Bank haddock landings

by subareas a

nd years, 1936 to 1948

Scrod

Large

Total

Year

North-
ern
Edge

South-
east
Part

South-
west
Part

South
Channel

Total

North-
ern
Edge

South-
east
Fart

South-
west
Part

South
Channel

Total

North-
ern
Edge

South-
east
Part

South-
west
Part

South
Channel

Total

1936... -

61.2
68.5
66.0
36.6
33.9
24.0
34.1
24.4
35. 1
19.3
25.7
36.4
50.0

39.5
38.8

27.2
12.2
16.1
21.5
22.3
33.8
29.5
47.9
41.7
32.9
26.8
20.5
19.2

26.3
27.0

1.7
.9
.9

2.2

7.4
8.6
9.0
7.0
8.7
26.8
4.3
3.8
4.6

6.6
6.6

9.9
18.4
27.0
39.8
36.4
33.6
27.4
20.7
14.5
21.0
43.2
39.3
26.2

28.6
27.5

100
100
100
100
100
100
100
100
100
100
100
100
100

100
100

54.2
59.8
43.0
33.9
31.2
21.0
30.2
23.3
27.0
21.1
27.6
27.1
36.6

32.9
33.5

23.0
10.0
19.1
24.0
23.9
36 4
28.6
31.4
23.4
18.8
23.9
24.9
13.6

23.3

23.2

1,4
1.2
2.0
2.6
6.5
7.8
6.9
8.8
15.9
17.6
7.7
7. 7
6.3

7.4

7.0

21.4
29.0
36.9
.39.5
,38.4
34.8
34.3
36.5
33.7
42.6
40.8
40.3
44.6

36.4
36.3

100
100
100
100
100
100
100
100
100
100
100
100
100

100
100

56.7
62.8
48.7
35.0
32.1
22.3
32. 1
23.8
28.3
20.8
27.2
30.7
43.0

35.2
35.6

24.5
10.7
17.8
22.9
23.4
35.2
29.0
38.3
26.3
21.0
24.5
23.2
16.3

24.4
24.1

1.5
1.1
1.5
2.4
6.8
8.2
7.8
8.1
14.7
18.9
7.0
6.2
4.9

6.8
6.8

17.3
25.5
32.0
39.7
37.7
34.3
31.1
29.8
30.7
39.3
41.3
39.9
35.8

33.6
33.5

100

1937—

100

1938

100

1939

100

1940

100

1941 ._

100

1942 .

100

1943

100

1944.-

100

1945..-

100

1946- -

100

1947—

100

1948— —

100

100

Unweighted average

100

GEORGES BANK HADDOCK— PART i: LANDINGS

159

Table 3. — Scrod haddock landed, by seasons and years
[In tbousands of pounds]

Year

Spring

Summer

FaU

Winter

Total

1931.

894

6,955

4,116

1,605

963

3,872

5,514

4,307

7,524

6,614

11,614

11,484

11,618

3,978

1,040

1,009

5,637

6,176

1,255
8,737
4,520
3,488
5,717
9,604
8,423
7,982
11,743
9,393
13, 578
17,026
13,907
5.485
2.983
7.215
8,337
12,669

5,266

11,799

8.631

6.038

10.554

12.933

14,665

20, 414

17,716

9,507

21,066

13, 757

10,032

4,822

5,441

9,147

20, 873

15, 982

10,086
4,022
1,531
1,845
8.303
3.541
2,482
7,204
6.142
4.086
7,506
7,213
1,950
963
2,210
3,749
6,058
9,729

17,501

1932

31,513

1933

18,798

1934

12,976

1935.

25,537

1936.

29,950

1937

31,084

1938 --

39,907

1939 ---

43,125

1940

29,600

1941 -- -

53,764

1942

49,480

1943

37,507

15,248

1945. -

11,674

1946

21, 120

40, 905

1948 - --

44, 556

Total ---

94,920
5,273

152,062
8,448

218,643
12, 147

88,620
4.923

554,245

Average

30, 791

Table 4. — Large haddock landed, by seasons and years
[In tbousands of pounds]

Year

Spring

Summer

Fall

Winter

Total

1931

29,611

18, 136

18, 367

7,261

.5,166

13, 828
19,705
15,283
15,811
15,763
19, 674
16. 870
14,202
16,310

14, M3
13, 049
19, 693
12,810

33,610
19,534
20.715
13.953
18, 623
17,218
17,431
15,637
18,118
22,204
23,808
20,300
17, 779
27, 942
20,319
27,825
19,190
12, 798

23, 827
23,303
19,495
12,780
18,041
16, 359
17,647
12,834
17,376
16,490
15, 961
12,916
15,385
24,648
19,260
28,603
17,668
14, 147

10,491

12, 934

4,265

2,914

11,814

6,663

9,588

8,726

10, 105

8,588

8,519

7, 525

4,711

11,844

12,375

13,289

7,809

9,212

97.539

1932

73.907

1933.

62,842

1934...

36,908

1935 --.

53. M4

1936

54,068

1937

64,371

1938

52. 480

1939 -

61.410

1940... -.

63,045

1941-.-

67. 962

1942

57,611

1943 - --

52, 077

1944

80,744

1945.

66,597

1946. --

82,766

1947 --.

64,360

1948

48, 967

Total

286,182
15,899

367,004
20,389

326, 740
18, 152

161,372
8,965

1,141,298

\verage

63,405

Table 5. — Total haddock landed, by seasons and years
[In thousands of pounds]

Year

Spring

Summer

Fall

Winter

Total

1931. -

30,505
25,091
22.483
8,866
6,129
17,700
25,219
19,590
23,335
22,377
31,288
28,354
25, 820
20,288
15,683
14,058
25,330
18, 986

34, 865
28,271
25,235
17,441
24,340

26, 822
25,854
23,619
29, 861
31, 597
37. 386
37.326
31.686
33.427
23.302
35.040

27, 527
25, 467

29, 093
35, 102
28,126
18, 818
28, 595
29,292
32,312
33,248
35,092
25,997
37, 027
26, 673
25,417
29,470
24, 701
37,750
38.541
30.129

20, 577
16, 956
5,796
4,759
20, 117
10,204
12,070
15,930
16, 247

12, 674
16,025
14, 738

6,661
12,807
14,585
17,038

13. 867
18.941

115,040

1932.

105, 420

1933

81,640

1934 -

49,884

1935.

79, 181

1936.

84,018

1937 --.

95,455

1938

92,387

1939.

104,535

1940.

92, 645

1941...

121,726

1942

107,091

1943-

89,584

1944. -

95.992

1945...

78.271

1946

103. 886

1947-

105, 265

1948.

93,523

Total

381, 102
21, 172

519,066
28,837

545.383
30,299

249, 992
13,888

1, 695, 543

94,196

AVERAGE WEIGHTS OF HADDOCK
LANDED

Average weights of fish landed, in each season,
year, subarea, and market category, were com-
puted by combining length samples of haddock
landed with seasonal length-weight relations. This
procedure is described in the following paragraphs.

At the Boston Fish Pier, lengths of representa-
tive samples of the haddock landed were obtained
from 1931 through 1948. In general, 50 scrod
and 100 large haddock were measured from a
" trip" when a vessel had fished in only one subarea
of Georges Bank, and as many vessels were
sampled as time permitted.

Each fish was measured from the tip of the
snout to the fork of the tail. Lengths were re-
corded by centimeter groups, that is, fish measur-
ing from 40.0 centimeters to and including 40.9
centimeters were recorded as 40 centimeters,
fish from 41.0 centimeters to and including 41.9
centimeters as 41 centimeters, and so on. No dis-
tinction as to sex was possible as most haddock,
when landed, are already dressed.

The numbers of Georges Bank haddock that
were measured, by years, seasons, and market
categories are shown in table 6. In all, measure-
ments of 627,996 haddock from Georges Bank were
utilized in this analysis.

Table 7 illustrates the general method used to
compute the average weight of haddock landed.
The steps of this method are as follows: (1) The
number of fish of each centimeter size group in the
total sample for the season was entered in column
II; (2) the length-weight relation was available by
seasons (table 8 and figure 7) and the average
weights for each centimeter size group were listed
in column III, the total weight of all fish measured
of each centimeter size group was computed in
column IV, and the total weight of all sizes in the
season's sample was entered at the bottom of
column IV; and finaUy (3) the total weight of the
sample was divided by the number of fish in the
sample to give the average weight of the fish in the
sample. We used this same general method for
each season, year, subarea, and market category.

Summaries of average weights are given in
table 9 and figure 8; to save space, values for the
various subareas are not shown.

160

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

LENGTH IN INCHES

10 15 20_

z

28

111
$6

'J

1 f '■ M M |.I 1 M ] 1 1 M

1 I r-r

! 1 M ! ! ITTJ

1 : T-

z

SPRING AND

SUMMER

i '--

1

-

1

WINTER

f -

h

-

//

1 1

-

i .

-

-

///

-

///

-

_

//'

-

! '

-

1

/

_

,

1

-

In

-

7

7

-

/

-

III

-

//■

-

!,

~

1

-

-

;

:

I

-

>

-

A

-

>/

"-

y

^

:

y'

"i

1 1 1

: 1 f^^ Mill

1 1 1 1

1 1 1 1

nil

MM

III

10

20

.30..„

40 5

6

7

B

9

10

Table 6. — Numbers of haddock measured for length, by
seasons and years

LENGTH IN CENTIMETERS

Figure 7. — Relation between length and weight for Georges
Bank haddock, by seasons.

■iZ 1i 34 -35 '36 37 ^8 '39 40
YEAR

'42 43 '44 -45 46 47

Figure 8. — Average weights of scrod, large, and total
haddock landed from Georges Bank, by years.

Season

Scrod

Large

Total

Year 1931:

Spring __

Summer _. .

S13
1,194
3,285
4,102

5,042
4,054
4,577
2.562

5.555
5,248
7,862
6,664

Fall

Winter

Total _

9,094

16, 235

25,329

Year 1932:

2,913
2,445
4,849
3.741

3,484
6,245
8,558
3,662

6,397

Summer

8.690

Fall

13,407

Winter

7,403

Total

13,948

21,949

35, 897

Year 1933:

3,082

1,702

2,455

911

3,834
3,775
5,349
2,157

6,914

Summer

5,477

Fall

7,804

Winter -..

3,068

Total

18,150

15,115

23,265

Year 1934:

675
2,014
2,588
2,691

3,326
3,341
3,924
1,831

4,001

5,355

Fall

6,512

Winter

4.522

Total

7,968

12, 422

20,390

Year 1935:
Spring --

1,440
4.582
7,199
3,318

3,398
7,357
6,462
2,981

4,838

11,939

Fall ---

13, 661

Winter

6,299

Total

16,539

20,198

36, 737

Year 1936:
Spring

3,643
9,533
9,740
3,849

6,914
11,089
9,997
5,595

10, 557

20, 622

Fall --

19, 737

Winter

9,444

Total

26,765

33, 595

60,360

Year 1937:

3,383
5,394
5,129
4,055

8,781
8.777
5,296
5,387

12,164

Summer

14,171

Fall

10,425

Winter ---

9,442

Total

17.961

28,241

46,202

Year 1938:

4,419
4,592
6,250
3.860

7,574
6,520
4,668
3,716

11,993

Summer ..

11,112

Fall

9,918

Winter .

7,576

Total

18, 121

22, 478

40,599

Year 1939:

2,540
5,244
4,448
3,043

4,002
6,835
7,712
4,141

6,542

12,079

Fall

12,160

Winter

7,184

Total

15, 275

22,690

37,965

GEORGES BANK HADDOCK PART i: LANDINGS

161

Table 6. — Numbers of haddock measured for length, by
seasons and years — Continued

Table 7. — Method used to compute average weight of haddock
Example used: 1948, Spring, Southeast Part, Scrod

Season

Scrod

Large

Total

Year 1940:

4.219
4.085
3,356
4,501

9,324
8,588
4,784
4,379

13,543

12, 674

Fall

8,140

Winter -

8,880

Total -

16, 162

27,075

43,237

Year 1941:

6.080
5,287
8,167
4,853

8,146
6,069
6,179
3,334

14,225

11.356

Fall

14,346

Winter

8,187

Total..

24,387

23, 727

48,114

Year 1942:

4,516
7.163
6,247
3,933

6,380
8,453
6,186
4,345

10, 896

15,616

12,433

Winter

8,278

Total -

21.859

25,364

47,223

Year 1943:

6.082

4,796

3.237

644

6,644
4,834
6,420
2,304

12.726

9,630

9,657

Winter

2.948

Total - -

14, 759

20,202

34.961

Year 1944:

1,471

1,532

1,984

200

3,295
5,183
6,262
1,890

4.766

fi. 715

7.246

Winter -

2,090

Total - - ---

5,187

15,630

20,817

Year 1945:

250
649
950
699

1,644
1,797
3,150
3,266

1,894

2,446

4,100

Winter

3,965

Total --

2,548

9,867

12.405

Year 1946:

750
2,600
3.250
2,234

2,800
6,147
6,660
3,387

3.550

8,747

9,910

Winter

5,621

Total -

S,834

18,994

27,828

Year 1947:

2.230

2,037
3,776
3,205

3,651
2,870
7,861
4.468

5.881

4.907

Fall

11,637

Winter

7,673

Total

11, 248

18,850

30,098

Year 1948:

3,507
3,480
7.101
4,763

4,181-
2,217
7.417
3,903

7.688

5,697

14.518

Winter

8,666

Total -

18,851

17, 718

36,569

.\n years:

51,713
68,330
83,011
54,602

92, 419
104, 151
110,462

63,308

144. 132

172,481

193, 473

Winter

117,910

Total

267,666

370, 340

627,996

Length group '
(I)

Number in
sample

(II)

Average
weight

(III)

Total

weight ol

sample

(IV)

1

5

11

17

29

36

40

44

45

41

31

53

64

82

133

142

188

188

183

160

160

93

62

38

17

11

6

2

Pound)
0.58
.64
.70
.76
.83
.90
.98
1.06
1.14
1.23
1.32
1.4
1.5
1.6
1.7
1.8
2.0
2.1
2.2
2.4
2.5
2.6
2.8
2.9
3.1
3.2
3.4
3.6
3.8
4.0
4.2

Pound)
0.58

30 cm

3.20

31 cm

7.70

32 cm -

12.92

24.07

32.40

35 cm

39.20

46.64

37 cm

51.30

38 cm

50.43

40.92

74.2

81.0

42 cm .

131.2

226.1

255.6

45 cm

376.0

46 cm -

394.8

402.6

48 cm

384.0

49 cm

400.0

241.8

173.6

52 cm

110.2

52.7

35.2

55 cm

20.4

56 cm

7.2

59 cm.. -

1

4.2

Total

1,873

' 1. 966

3, 680. 16

' By 1-cm. intervals
3,680.16 pounds
1,873 fi.sh

= 1.965 pounds.

Table 8. — Length-weight relation by seasons, in terms of
centimeter size groups and drawn weight in pounds

Length >

Drawn weight in pounds

Spring

Summer

Fall

Winter

18 cm.

0.15
.17
.20
.23
.27
.30
.34
.38
.43
.47
.52
.58
.64
.70
.76
.83
.90
.98
1.06
1.14
1.23
1.32
1.4
1.5

0.12
.14
.17
.20
.23
.26
.29
.33
.36
.41
.46
.50
.55
.60
.66
.72
.79
.85
.82
1.00
1.08
1.16
1.2
1.3

0.15
.17
.20
.23
.26
.30
.33
.38
.42
.47
.52
.57
.63
.69
.75
.82
.89
.96
1.05
1.13
1.22
1.31
1.4
1.5

0.14

.16

.19

21 cm. _

.21

.26

.28

24 cm

.32

25 cm.

.36

.40

27 cm

.45

28 cm

.50

.56

30cm

.61

31 cm

.67

.73

33 cm

.80

34 cm

.88

35 cm

.96

1.04

37 cm

1.12

1.21

1.31

40cm

1.4

41 cm

1.5

See footnote at end of table.

162

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Table 8. — Length-weight relation by seasons, in terms of
centimeter size groups and drawn weight in pounds — Con.

Table 8. — Length-weight relation by seasons, in terms of
centimeter size groups and drawn weight in pounds — Con.

Length '

Drawn weight in pounds

Spring

Summer

Fall

Winter

L6
L7
L8
2.0
2.1
2.2
2.4
2.5
2.6
2.8
2.9
3.1
3.2
3.4
3.6
3.8
4.0
4.2
4,4
4.6
4.8
6.0
5.2
5.4
5.7

1.4
1.6
1.6
1.7
1.8
2.0
2.1
2.2
2.3
2,5
2.6
2.8
2.9
3.1
3.2
3.4
3.6
3.8
3.9
4.1
4.3
4.5
4.7
4,9
6.1

1.6
1.7
L8
2.0
2,1
2.2
2.3
2.6
2.6
2.8
2.9
3.1
3.2
3.4
3.6
3.8
4.0
4.1
4.3
4.5
4.8
6.0
6.2
6.4
5.6

1.6

43 cm

44 cm-

1.7
1.8

2.0

2.1

47 cm

2.2

48 cm -.

2.4

49 cm

2 6

60 cm. _ ...

2.7

2.8

3.0

53 cm.

3.2

3.4

3.5

56 cm-

3. 7

87 cm

68cm.--

3.9
4. 1

59 cm.-

60 cm

4.3
4.6
4.8

62 cm

5.0

64 cm

5.2
5.6

66 cm

6. 7

66 cm

6.0

See footnote at end of table.

Length i

Drawn weight in pounds

Spring

Summer

Fall

Winter

67 cm

6.9

6.2

6 4

6.7

7.0

7.2

7.6

7.8

S.l

8.4

8.7

9.0

9.3

9.7

10

10.3

10.6

10,9

11,4

11.7

12,2

12,6

12,9

13,5

6,4

6,6

5,8

6.1

6.3

6.6

6 8

7,1

7,4

7,7

7,9

8,2

8,6

8.9

9.2

9.5

9.8

10.1

10 3

10.7

11.2

11.6

11.8

12.3

5.9

6.1

6.4

6.7

6.9

7.2

7.5

7.8

8.1

8.4

8.7

9

9.3

9.6

10.0

10.3

10.6

10.9

11.4

11,7

12,2

12,6

12,9

13,5

68 cm.

6.6
6 8

69cm-

70cm ---

71 cm.

7 4

72 cm. _

7 7

73 cm --

8 3

76 cm.

8 7

76cm

9 4

78 cm

9 7

79 cm

10 1

80 cm

10 4

81 cm

10 8

82 cm. . - -

11 1

83 cm

11 6

84 cm

11.8

85 cm.

. 12 3

86cm

12.7

87 cm

13.1

88 cm

13 6

89 cm . -

14. 1

90cm

14.6

' Size groups by 1-cm. intervals.

Table 9. — Average weights in pounds of scrod, large, and total haddock, by seasons and years

Year

1931

1932

1933

1934

1935

1936 -.

1937

1938

1939.-

1940

1941

1942

1943

1944 --.

1945 -..-

1946

1947-

1948

Weighted average

Scrod

Spring

1.817
1.664
1.938
I. 890
1.874
1.905
1.950
1.972
1.890
1,989
1,688
2,012
1,924
1,926
1,940
1,665
1,876
1,842

1.871

Sum-
mer

1.640
1.679
1.248
1,648
1,594
1.456
1,528
1.510
1,633
1.748
1,541
1,690
1,586
1,617
1,296
1,449
1,481
1 493

1,556

Fall

1.663
1.942
1.714
1.614
1.706
1.710
1.820
1,709
1,718
1,867
1,681
1. 701
1,837
1.800
1.644
1.770
1.580
1.681

1.719

Winter

1.641
1.921
1.636
1.402
1.624
1,586
1.793
1.656
1.674
1.658
1.823
1,742
1,809
2.049
1.736
1.778
2.291
1.592

1,697

Total

1.586
1.793
1.604
1,617
1,658
1,626
1,748
1,679
1,715
1,803
1.662
1.766
1,757
1.772
1.573
1.642
1.670
1.623

1.691

Large

Spring

3.648
3.732
3,607
3.580
3,706
3, 602
3,580
4,902
3,965
3.434
3.991
3,644
3.495
3,464
3,678
3,630
3, 725
3,959

3.718

Sum-
mer

3.112
3.360
3.062
3.126
3.014
3.009
3.160
3.199
3,083
3,218
3,330
3,195
3,138
3,031
3, 167
3,077
3,635
3, 251

3,163

Fall

3.866
3.184
3. 171
3.271
3.044
3,026
3.289
3.348
2.933
3.357
3.377
3, 121
3.306
3.231
3.648
3. 40fi
3.622
3.472

3.306

Winter

3.490
3.322
3,639
3,195
3,476
3,343
4,061
3.819
3,492
3.998
4.030
3.536
2,774
3,965
3,766
3,824
4,194
3.743

3.661

Total

3.473
3.374
3.277
3.263
3. 174
3,187
3,432
3,716
3.285
3.399
3.592
3,340
3.239
3.290
3.481
3.377
3,719
3,572

3,398

Total

Spring

3. 643
2,769
3,116
3,082
3,212
3.014
3.027
3.692
2.925
2.827
2.660
2.743
2,565
2,995
3,472
3,346
3,055
2,882

2.984

Sum-
mer

3.079
2.562
2.429
2 660
2.492
2.177
2.344
2.322
2.285
2.575
2.342
2.272
2. 195
2,651
2,667
2,499
2,524
2.050

2.430

Fall

3.112
2 621
2 616
2.460
2.360
2 267
2.407
2.107
2 161
2.698
2. 145
2.182
2.513
2.859
2.827
2.782
2 130
2.218

2.413

Winter

2.154
2.832
2.760
2.136
2.363
2.415
3.218
2 401
2 475
2.656
2 572
2 351
2 40O
3.705
3.199
3,052
3.077
2.209

2.596

Total

2.940
2.670
2.643
2.580
2.461
2 374
2 613
2,438
2.384
2.660
2.375
2 366
2 393
2 896
2 948
2.780
2. 519
2.272

2.654

NUMBERS OF HADDOCK LANDED

Dividing poundage by average weight gave the
number of fish landed — for each season, subarea,
market category, and year. Excepting subarea
values, all of these numbers are shown in the fol-
lowing tables.

Tables 10, 11, and 12 show the numbers of
scrod, large, and total haddock landed, by sea-
sons and years. Relative contributions of scrod
and large haddock to the total, by seasons, are
shown in figure 9. Figure 10 shows the yearly
trends, and here it can be seen that much of the
variation in total landings by years is due to
variations in scrod landings. The importance of

these small-sized haddock to the present fishery
is thus evident.

SIZE COMPOSITIONS OF HADDOCK
LANDED

Now having available the number of haddock
that were landed (in each season, year, subarea,
and market category), and having also the lengths
of samples of haddock (in each similar subdi-
vision), we estimated how many haddock of each
size were landed. This was accomplished by
multiplying the number of fish measured in each
centimeter size group by the proportion of the
number landed to the number measured. This

GEORGES BANK HADDOCK PART I I LANDINGS

163

calculation assumes that the fish measured were
representative samples of the landings. Pre-
cautions had been taken to avoid bias in sampling,
and many uniformity trials showed that the sam-
ples could be considered as representative of the
landing.

Table 10. — Numbers of scrod haddock landed, by seasons

and years

(In thousands of fish]

o

-i

15

f:-;;:;-.;;:^ SCROD _

;

^B LARGE

—

A

—

—

1

/
^

i^""'!^

—

-

b

—

HH|

^^1

—

—

1

1

H

—

1

I

I

—

Year

Spring

Summer

Fall

Winter

Total

1831.

492

4.204

2,124

849

514

2,033

2,828

2,193

3,980

3,325

6,879

5,708

6,040

2,06fi

636

606

3,004

3,352

816
5,206
3,623
2,117
3,587
6,598
5,512
5,285
7,190
5,373
8,811
10,077
8,771
3,393
2,301
4,978
5,628
8,484

3,186
6,075
5,035
3,742
6,190
7,561
8,056

11,945

10,313
5,093

12,535
8,088
5,460
2,679
3,310
5,169

13,213
9,510

6,547
2,094

938
1,316
5,113
2,232
1,384
4,350
3,670
2,623
4,117
4,140
1,078

470
1,273
2,108
2,644
6,113

11,041

1932.

17,579

1933

11,718

1934

8,024

1935

15,404

1936

18, 424

1937 .. ..

17,780

1938.

23,773

1939

25,153

1940

16,414

1941

32,342

1942

28,013

1943

21,349

1944

8,607

1945.

7,420

1946-

12,861

1947

24, 489

1948

27, 459

Total -

60,732
2,818

97,760
5,431

127, 160
7,066

62,208
2,900

327,860

Average

18,214

Table U.—

Numbers of large haddock landed, by seasons
and years

[In thousands of fish]

SUMMER

FALL

WINTER

Figure 9. — Numbers of scrod, large, and total haddock
landed from Georges Bank in the average year, by
seasons.

Year

Spring

Summer

Fall

Winter

Total

1931- .

8,117
4,859
5,092
2,028
1,394
3,839
5,504
3,118
3,998
4,590
4,930
4,630
4,064
4,708
3,981
3,595
6,287
3,236

10, 799
5,831
6,765
4,464
6,179
6,723
5,617
4,888
5,876
6,899
7,150
6,353
6,666
9,218
6,436
9,043
6,279
3,937

6,164
7,318
6,147
3,907
5,927
6,408
5,366
3,833
6,924
4,912
4,726
4,138
4,663
7,629
6,428
8,399
4,878
4,075

3,006
3,894
1,172
912
3,399
1,993
2,367
2,285
2,894
2,148
2,114
2,128
1,698
2,987
3,287
3,476
1,862
2,461

28,086

1932-

21,902

1933-

19, 176

1934

11,311

1935

16,899

1936

16,963

1937

18,754

1938

14, 124

1939.

18,692

1940

18,549

1941.

1942 - -- ..

18, 920
17, 249

1943

16,080

1944

24,542

1945.

19, 132

1946. -.

24, 612

1947-.- -

17,306

1948

13, 709

Total

76, 970
4,276

116,022
6,445

98,832
.';,491

44,082
2,449

336,906

Average

18,661

Table 12.

-Numbers of total haddock landed, by seasons
and years
[In thousands of fish]

I93J '32 33 34 35 '36 37 36

■40 HI 42 43 44 45 46 47 46

Figure 10. — Numbers of scrod, large, and total haddock
landed from Georges Bank, by years.

Year

Spring

Summer

FaU

Winter

Total

1931

8,609
9,063
7,216
2,877
1,908
6,872
8,332
5,311
7,978
7,915
11,809
10,338
10,104
6,773
4,517
4,201
8,291
6,688

11,615
11,037
10,388
6,581
9,766
12,321
11,029
10, 173
13,066
12,272
16, 961
16, 430
14, 436
12,611
8,737
14,021
10,907
12,421

9,350
13,393
11,182

7,649
12,117
12,969
13, 422
15, 778
16,237
10,005
17, 261
12,226
10,113
10,308

8,738
13,668
18,091
13,686

9,6S3
5,988
2,108
2,228
8,512
4,225
3,751
6,635
6,664
4,771
6,231
6,268
2,776
3,457
4,560
5,683
4,506
8,674

39, 127

1932

39, 481

1933

30,894

1934

19,335

1935

32,303

1936

35,387

1937

36,634

1938

37, 897

1939

43,845

1940

34,963

1941

1942

37,429

1943

1944

1945

1946

1947

1948

Total

127, 702
7,096

213, 772
11,876

225, 992
12, 655

96,290
5,349

663,756

Average

36,875

164

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

The size compositions for subareas were com-
bined, and thus we obtained a size composition
representing all of Georges Bank, for each season,
year, and market category. A certain amount of
irregularity in these curves was due to sampling
variations, inasmuch as only a limited sample from
a very large population of fish had been obtained.
To eliminate some of this irregularity we smoothed
each distribution by a moving average of three.
ScTod haddock

Tables 13, 14, 15, and 16 show the size compo-
sitions ^ of the landings of scrod, in each of the 72
seasons, from 1931 through 1948. Table 17 shows
the size compositions of scrod by years. Table 18
and figure 11 show the average size compositions
of scrod for each season in all of the 18 years, and
table 19 shows the size composition of scrod that
were landed in the average year, and also the per-
centage size composition.
Large haddock

Tables 20, 21, 22, and 23 show the size compo-
sitions of large haddock in each of the 72 seasons
over the 18-year period. Table 24 shows the size
composition of large haddock by years. Table 25
and figure 11 show, by seasons, the average size

' For convenience in handling the large mass of data, we grouped all length
frequencies by 3-centimenter groups: Fish of the 29-, 30-, and Sl^jentimeter
groups were recorded as 30 centimeters, fish of the 32-, 33-, and 34-centimeter
groups as 33 centimeters, and so on. In graphs and tables where centimeters
are shown, they are shown as 30, 33, and 36 rather than 30.5, 33.5, and 36.5
(the true midpoints of the groups) inasmuch as the original centimeter meas -
urements were recorded as 29 when the midpoint was 29.5, 30 instead of 30.5,
31 instead of 31.5, etc. Where inches are shown in graphs, they represent
actual values: The inch equivalents opposite 30.5 rather than 30, opposite
31.5 rather than 31, and so on.

The sizes in inches corresponding to the true midpoints of the 3-centimeter
groups are as follows:

3-centimeter groups: Iiuhea

18 cm 7.3

21 cm _ 8.5

24 cm _ 9.6

27 cm 10.8

30 cm 12.0

33 cm _ 13.2

36 cm 14.4

39 cm 15.6

42 cm 16.7

45 cm 17.9

48 cm 19.1

51 cm 20.3

54 cm 21.6

57 cm 22.6

60 cm 23.8

63 cm 25.0

66 cm 26.2

69 cm.... 27.4

72 cm 28.5

75 cm 29.7

78 cm 30.9

81 cm 32.1

84 cm 33.3

87 cm... 34.4

composition of large haddock that were landed in
all 18 years, and table 26 shows the size composi-
tion of large haddock that were landed in the
average year, and also the percentage size compo-
sition.

LENGTH IN INCHES

10 15 20 25

I I I I I 1 I I I I I I I I I I I I

30 40 50 60 70

LENGTH IN CENTIMETERS

Figure II. — Size compositions of scrod, large, and total
haddock landed from Georges Bank in the average year,
by seasons.

Total haddock

Tables 27, 28, 29, and 30, and figures 12a, 12b,
and 12c show the size compositions of total had-
dock (scrod and large combined) in each of the 72
seasons over the 18-year period.

The presence of modes (figures 12a, 12b, and
12c), at slightly increasing sizes of fish in succeed-
ing seasons, suggests that each series of modes may
be composed largely of the same year class of had-
dock. In some instances these year classes (if
they are year classes) apparently were the chief
source of supply of the fishery for several succeed-
ing seasons, and even for succeeding years.

These modes are more obvious if one season
(spring, for example) in a particular year is com-

GEORGES BANK HADDOCK — PART i: LANDINGS

165

pared with the average of that season for all years.
Figures 13a, 13b, and 13c show such contrasts in
terms of deviations from seasonal means.

1931

I93£

1933

1934

1935

1936

2
1

-

f

i

b

L

*

L

!

k

k

St

2
I '

L

J

L

A

k

k

k

1

A

L

i

i

L

2

-1 1

2

n

L

^

i

k.

J

i

L

i

Ik

L

i

i

-J
<

3
2

i

k

1

-

a:

z

4

6

4

6

A

6

A

6

4

(,

4

6

LENGTH IN CENTIMETERS

LENGTH IN INCHES

FiouRE 12a. — Size compositions of total haddock landings
from Georges Bank, by seasons and years, 1931 to 1936.

40 60 40 60 40 60 40 60 40 60

LENGTH IN CENTIMETERS

Figure 12b. — Size compositions of total haddock landings
from Georges Bank, by seasons and years, 1937 to 1942.

Table 31 and figure 14 show the yearly size
compositions for total haddock. Table 32 shows
the four seasonal size compositions for the average
of all 18 years. These values are shown also in
figure 11.

In figure 14, it can be seen that there was con-
siderable variation in the relative numbers of vari-
ous sizes in different years. To study these dif-
ferences more readily, we plotted (fig. 15) devia-

4060 4060 4060 40 60 4060

LENGTH IN CENTIMETERS

LENGTH IN INCHES

-lEte-

FiGURE 12c. — Size compositions of total haddock landings
from Georges Bank, by seasons and years, 1943 to 1948.

40 60 40 60 40 60 ' 40 60 I 40 60~

LENGTH IN CENTIMETERS

»« ^o 'si^io 'jo " iJo ' ^0 sjo " ' »' Jo

LENGTH IN INCHES

Figure 13a. — Deviations from the average size composi-
tions, by seasons, 1931 to 1936.

tions from the average year. Here, it can be seen
that a scarcity of small-sized fish characterized
some years such as 1931, 1940, 1944, 1945, and
1946. In other years, such as 1943 and 1948, a
scarcity of large-sized fish occurred. In still others,
an abundance of either small-sized or large-sized
haddock occurred, or a scarcity or an abundance of
both — the scarce years of 1933, 1934, and 1935,
and the abundant year of 1941 demonstrate this.
In other years, such as 1937, all sizes were taken
in approximately average numbers.

The differences in size composition help to ex-
plain how different average weights (shown in
table 9) occurred. As one example, the years 1936

166

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

LENGTH IN INCHES

10 20 30 10 20 30 10 20 30 10 20 30 10 20

40 60 40 60 40 60 40 60 40 60

LENGTH IN CENTIMETERS

■■I'l'i I t. | I .. ,. I. .. [ 1 1 , I , I.,.,

30*H3 20 Xf\0 SO yJo 20 Xf lO

LENGTH IN INCHES

Figure 13b. — Deviations from the average size composi-
tions, by seasons, 1937 to 1942.

1943 1944 I94S 1946 Id47 1946

40 60 ' 40 60 40 60 • 40 60 • 40 60 ' 40 60~

, , LENGTH IN CENTIMETERS

lio ' ' 20 ' ajio ' 20 ' jolo ' 20 '»l'io' ^ 'aJ'iQ 20 ' aj ' ji ^6 ' i^

LENGTH IN INCHES

Figure 13e. — Deviations from the average size composi-
tions, by seasons, 1943 to 1948.

and 1941 had an identical, low average weight of
2.37 pounds. In 1936, this low average weight was
associated with a slight abundance of small-sized
and a scarcity of large-sized haddock, while in 1941
it was associated with factors entirely different —
an abundance of all sizes, but with smaU haddock
much more abundant than large-sized haddock.

It is obvious that average weight is dependent
upon the relative numbers of the various sizes and
not upon the actual numbers of fish of various sizes.

In table 33 are shown the size composition of the
average year and the percent size composition.
Undersized haddock

The New England Fish Exchange defines scrod
haddock as 1% to 2^ pounds. The average length

LENGTH IN CENTIMETERS

Figure 14. — Size compositions of total haddock landings
from Georges Bank, by years.

of lYi pound haddock is about 41 centimeters.
Thus, most fish up to and including the 39-centi-
meter size group could be considered as under-
sized. From table 33, we see that in the average
year about 4,974,000 undersized fish were landed,
or 13.5 percent of the total. In all years the total
number of undersized haddock landed was about
89,513,000. The numbers of undersized haddock
that were landed in each year are shown in table
34.

Scrod versus large haddock

Table 35 shows the percentages of each size
group that were scrod and large haddock; figure 16
shows the actual size compositions of scrod and
large haddock.

The dividing line between scrod and large had-
dock for the average of the 18-year period was
about 48 centimeters. Below 48 centimeters most
fish landed were classified as scrod; above 48 most
were classified as large haddock.

This dividing line has varied from year to year,
owing to differences in relative abundance of fish of
difference sizes and to market conditions. Such

GEORGES BANK HADDOCK — PART I: LANDINGS

167

LENGTH IN INCHES
10 20 3010 20 3010 20 3010 20 30 10 20 30

LENGTH IN INCHES
5 10 15 20 25

! M ' I I I I I I I I M I I I

40 60 40 60 40 60 40 60 40 60

LENGTH IN CENTIMETERS

Figure 15. — Deviations from average size compositions,
by years.

10 20 30 40 50 60 70 80 90 100
LENGTH IN CENTIMETERS

Figures 16. — Size compositions of scrod and large had-
dock landings from Georges Bank in average year.

variation made it necessary to measure samples of
each category in evfry year for which we desired
an accurate measurement of size composition of the
total haddock landings.

The amount of overlap in length between the
two market categories has been considerable. For
instance, haddock as long as 63 centimeters were
occasionally landed as scrod, and fish as small as
36 centimeters were landed as large haddock. This
was due to difficulties and mistakes in sorting had-
dock into two arbitrary categories at sea under
varying conditions of weather, haste, and so on.

Table 13. — Size compositions of scrod haddock, spring seasons
(In thousands of fish]

Length '

1931

1932

1933

1934

1935

1936

1937

1938

1939

1940

1941

1942

1943

1944

1945

1946

1947

1948

1

1

9"
40
105

278
554
86«
726
215
29
4

1

3

13

108

555

1,211

1,121

819

1,184

1,249

533

78

4

1

28

74

98

152

370

650

520

117

17

6

2

30

113

173

185

314

520

542

253

45

11

4

33

125

385

1.117

1.948

1,530

493

71

1

I
12

63

208

774

1.536

1,667

1,155

441

116

36

18

8

3

1

1

1

1

15

66

160

175

68

14

2

7

31

292

927

1,464

1,111

331

39

2

9

37

162

460

962

1,231

851

234

31

2

""l6
101
295
654
989
911
311
43
5

2

11

62

250

480

614

481

145

17

3

......

30

144

230

112

13

3

2

8
15
38
97
198
188
57
5

33cm-..

2
44

172
491
828
478
102
7

2

14

62

242

348

l'i6

24

1

1
13
68
144
163
94
28
3

10
75
382
892
899
549
171
26

2

36cm

87

39 cm

531

42 cm -

1,036

45cm...

925

48 cm.. . _

574

173

.Mem

24

60 cm

69 cm

72 cm

Total-.

492

4,204

2,124

849

514

2,033

2,828

2,193

3,980

3,325

6,879

5,708

6,040

2,065

536

606

3,004

3,352

' Size groups by 3-cm. intervals.

168

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Table 14. — Size compositions of scrod haddock, summer seasons
[In thousands of fish)

Length i

1931

1932

1933

1934

1935

1936

1937

1938

1939

1940

1941

1942

1943

1944

1945

1946

1947

1948

1

2

5

19

128

635

1,550

1.702

1,365

900

258

29

3

1

24 cm

14
152
290
373
524
636
592
593
347

92
9
1

'"17"

265

1,119

1,722

1,343

718

218

64

36

18

2

1

3

16

62

3b6

1,275

1,477

980

769

267

33

5

1

2

4

15

163

949

2,046

1,925

1,402

I. 491

693

107

14

27 cm. .

1

10

106

531

1,230

1,758

2,724

2,706

885

116

10

1

24

214

655

1,276

2,166

2,254

1,575

539

57

8

2

11

29

210

555

940

1,033

1,372

714

104

8

30cm_._

1

16

114

659

1, 594

1,807

842

159

14

2

12

103

225

472

750

463

83

5

1

1

13

189

623

899

1.028

656

154

20

4

1

25

345

1,059

1,768

2,048

1,502

405

31

6

""9
134

587

1,176

1,427

1,416

564

56

4

4

10
85
442
996
1,100
636
112
8

"29"
333

868
688
261
104

17

1

17

556

1,366

1,516

1,249

732

177

16

36cm. ._ _.

8

74

240

324

152

17

1

696

39 cm. .

1 758

42 cm,..

2,420

48 cm.

1 068

51 cm.

135

54 cm...

12

60 cm

1

1

2

63 cm. .

Total

816

5,206

3,623

2,117

3,587

6,598

6,512

5,285

7,190

5,373

8,811

10, 077

8.771

3,393

2,301

4,978

5,628

8,484

' Size groups by 3-cm. intervils.

Table 15. — Size compositions of scrod haddock, fall seasons
[In thousands of fish|

Length 1

1931

1932

1933

1934

1935

1936

1937

1938

1939

1940

1941

1942

1943

1944

1945

1946

1947

1948

24 cm. -

2

30

166

383

385

1.050

2.444

2.395

994

188

19

1

10

59

136

664

2.519

4,546

3,180

1.106

277

35

2

1

17

44

254

1.228

1,943

1,121

373

53

1

4

17

103

345

1,298

2.690

2,172

776

140

14

2

6

48

183

242

414

1,191

1,535

1,076

347

47

3

1

1

6

58

648

1.901

2.294

1,785

1,095

264

34

3

1

6

12

174

812

1,244

798

213

32

16

2

1

8

36

267

884

1,496

1,504

798

164

11

30 cm

33cm

1

7

127

736

1,299

777

203

28

7

1

. ....

29

318

1,547

2,592

1,362

203

21

2

2

41

362

1,094

1,096

693

385

67

1

1

1
24

256

1.310

2.173

1,648

660

111

7

1

40

370

2,291

4,587

3,359

1,092

177

25

3

1

43

354

1,591

3.262

3.178

1,546

308

27

3

3

41

337

836

1,221

1,553

1,162

281

24

2

3

50

139

315

732

929

418

77

14

2

4

54

1.122

4,250

4,482

2,205

921

147

24

4

4

104

36 cm

1,076

39 cm

2,158
2,389

45 cm___ _

48 cm

2,262
1,241

236

32

67 cm-

6

2

Total..

3.186

6,075

5,035

3.742

6,190

7,561

8,056

11,945

10, 313

5,093

12,535

8.088

.'5,460

2,679

3,310

5,169

13, 213

9,510

' Size groups by 3-cm. intervals

Table 16. — Size compositions of scrod haddock^ winter seasons

[In thousands of fishj

Length i

1931

1932

1933

1934

1935

1936

1937

1938

1939

1940

1941

1942

1943

1944

1945

1946

1947

1948

2

11

140

485

632

643

989

1,346

718

136

11

1

27 cm

16

80

109

176

292

389

204

44

6

5

37

168

343

362

460

565

250

36

5

1

2

18

74

149

155

210

395

292

79

9

1

4

67

243

418

644

1.199

1.176

481

105

11

2

2

28
135
434

719
826
887
510
116
12
1

1

63

321

566

419

288

450

384

113

17

1

7

55

114

169

403

1,076

1.412

698

156

26

1

1

10

49

204

779

1.351

1,076

523

'il
1

1

34

694

2,054

2,264

1,205

274

19

1

1

3
24

107

330

661

595

296

74

14

3

1

"32"

254

813

878

444

177

42

3

1

4

33 cm- - -

36cm -

19
152
567
845
445

59
6

14

68

189

362

231

63

*

1

5

63

199

274

281

208

40

7

1

5

28
52
79
191
107
8

7

37

192

448

457

120

11

1

105
893

39 cm

1,712

42 cm - _--

1,537

45 cm ;

48 cm -

1,132
676

51 cm

134

64 cm

17
3

60 cm

Total-.

6,547

2,094

936

1,316

5,113

2,232

1,384

4,350

3,670

2,623

4,117

4,140

1,078

470

1,273

2,108

2,644

6,113

' Size groups by 3-cm. intervals.

GEORGES BANK HADDOCK — PART I: LANDINGS

169

Table 17. — Size composition^ scrod haddock, in each of the 18 years

[In thousands of fish]

Length

1931

1932

1933

1934

193S

1936

1937

1938

1939

1940

1941

1942

1943

1944

1945

1946

1947

1948

1

2

15

101

473

1,421

3.362

5,222

4,752

2,446

551

65

12

1

1

3

32

193

514

904

2,602

4,930

4,999

2,730

700

HI

41

18

2

1

6

34

237

968
2.993
6,089
8.366
7.178
4.544
1.659

246
21

14
153

307
433

890

2,225

3,388

:.773

1,261

255

18

1

'""is"

84

164

655

1.673

2.199

1.995

1,048

180

7

2

1

2

11

142

523

1,090

2,644

4,205

4.184

2,128

429

41

5

1
9

114

458

1.357

4,395

7,577

6,035

2,884

802

114

21

5

1

2

39

240

1,295

3,829

6,818

7,344

4,409

1,063

101

12

1

7

111

529

1.043

1,715

3,309

4 401

3,787

1,335

163

13

1

3

30

246

1.508

4.295

6.520

7.533

5.854

1,774

235

15

2

39

323

1,263

3.085

5.197

5,755

4,100

1,301

204

47

20

8

3

1

1

" "9"

76

314

1,059

2.287

2.834

1,642

342

39

5

1

6

48

546

1,902

2,524

1,746

549

73

21

4

12

48

285

967

2,251

3,388

3,659

1,865

347

33

3

2

1

30 cm

3
42

844

2,920

3,9«3

2,481

697

78

11

2

8
49
454

2.056

5.172

6,355

2,980

460

43

2

4

113

2,007

6,811

7,767

4,797

2.379

537

69

5

8

263

36 cm

2,752

39cm

6,159

7,382

6,660

48cm .

3,459

51 cm.

678

85

57 cm

9

4

72 cm

Total

11,041

17, 579

11,718

8,024

15,404

18,424

17,780

23.773

25,153

16, 414

32,342

28,013

21,349

8,607

7,420

12,861

24,489

27.459

' Size groups by 3-cm. iotervals.

Table 18. — Average size composition of scrod haddock,
each of the seasons

[In thousands of fish]

Length '

Spring

Summer

FaU

Winter

24 cm

1

10

23

81

393

985

1,341

1,354

933

271

32

S

1

27 cm --

1

12

56

157

346

643

808

577

184

29

4

1

1

3

19

76

397

1,389

2,258

1,871

857

172

20

2

3

30 cm

28

107

292

39 cm

562

42 cm

770

716

48 cm

342

51 cm -

71

9

1

63 cm

Total

2,819

5,430

7,064

2,901

T.\BLE 19. — Size composition of scrod haddock in the average
year

[In thousands of fish]

' Size groups by 3-cm. intervals.

Length

Average
number

Percent of
total

1

17

82

320

1,240

3,281

5,012

4,747

2,710

699

89

12

3

1

0.1

30 cm

.4

33 cm

1.8

6.8

18.0

42 cm

27.5

45 cm

26.1

14.9

3.8

54 cm

.5

57 cm

.1

Total

18, 214

100.0

' Size groups by 3-cm. intervals.

Table 20. — Size compositions of large haddock, spring seasons
[In thousands of fish]

Length i

1931

1932

1933

1934

1935

1936

1937

1938

1939

1940

1941

1942

1943

1944

1945

1946

1947

1948

1

1

4

7

38

192

526

658

599

444

306

183

92

44

19

5

1

7

36

148

596

1,068

1,045

732

477

283

172

84

39

16

4

......

25

112

395

673

791

728

585

350

185

87

32

15

4

20

118

444

663

608

551

453

322

228

109

46

19

9

1

3

16

96

461

946

1,139

971

641

545

275

122

63

7

1

39cm

6

36

256

825

1,398

1,567

1,537

1,185

742

364

132

51

18

40

279

548

684

753

834

714

497

300

148

43

16

2

"""ie"

181

637

1,074

897

753

632

450

282

118

41

7

4

1

5

67

276

410

394

317

231

153

99

47

18

6

4

4
44

132

240

289

233

178

140

76

38

17

3

1

9

89

450

777

798

668

435

306

174

87

34

10

1

2

8

118

636

1.225

1,171

897

608

412

232

122

54

17

2

2

7

36

282

652

778

715

560

416

266

167

78

26

10

2

1

1

9

112

647

1,171

1,018

683

402

241

160

88

42

10

5

1

""""3"

51

395

1.025

1.169

940

604

363

198

101

52

23

5

1

10

75

462

945

992

824

586

382

1S7

94

44

14

4

4

15

73

416

958

978

686

416

252

162

67

25

8

4

42 cm

ii

45 cm.

45

48cm. _

206

526

54cm _

627

57 cm , . .

590

60 cm.

410

346

228

69 cm .

162

72 cm.

64

19

1

1

84 cm

Total..

8,117

4,859

5,092

2,028

1,394

3,839

5,504

3,118

3,998

4,590

4,930

4,630

4,064

4,708

3.981

3.695

5.287

3.236

' Size groups by 3-cm. intervals.

170

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Table 21. — Size compositions of large haddock, summer seasons
[In thousands of fish]

Length i

1931

1932

1933

1934

1935

1936

1937

1938

1939

1940

1941

1942

1943

1944

1945

1946

1947

1948

33 cm- __

1

15

49

140

604

1,480

1,624

1,411

1,332

1,107

651

359

181

66

14

8

1

36 cm.

1

11

33

315

1.216

1,458

1,090

698

409

267

146

60

24

5

1

""""4"

19

127

650

1,352

1.227

859

650

316

190

116

67

28

11

1

1

6

20

85

486

1,064

1,107

868

58a

354

179

90

39

12

4

1

19

95

457

1,444

2,043

1,862

1,306

913

521

291

172

60

22

10

2

11

49

119

362

782

1.049

1,203

1,264

806

411

216

108

37

14

5

39 cm. .. ...

1

46

291

1,191

2,099

2,138

1,784

1,427

910

507

255

103

36

7

2

1

1

2

27

318

876

936

789

768

773

630

389

209

82

32

7

2

14
44

280

1,065

1,556

1,374

932

628

424

242

128

56

13

8

2

3

23

143

629

971

869

689

542

327

160

74

25

9

2

18

210

938

1.457

1,351

983

607

344

175

66

22

6

1

5

23

129

848

1,562

1,223

798

520

380

202

112

54

13

5

2

2

12

97

676

1,689

1,644

1,176

722

451

273

149

65

28

13

2

6
14

56

461

1,378

1,726

1,468

927

552

291

153

86

30

10

2

2

12

105

767

1,617

1,349

1,036

669

439

249

HI

59

27

10

1

6

16

66

650

1,370

1,448

993

560

332

187

87

38

10

2

1

......

104

394

739

901

906

686

672

439

260

114

34

17

2

19

45 cm

147

48 cm

675

51 cm

906

54cm.

813

521

60cm

354

63 cm

238

66 cm.

117

62

78

12

78 cm

g

84 cm.

10, 799

5,831

6,765

4,464

6,179

5,723

5,517

4,888

5,876

6,899

7,150

6,353

5,666

9,218

6,436

9,043

5,279

3,937

' Size groups by 3-cm. intervals.

Table 22. — Size compositions of large haddock, fall seasons
[In thousands of fish]

Length >

1931

1932

1933

1934

1935

1936

1937

1938

1939

1940

1941

1942

1943

1944

1946

1946

1947

1948

36 cm

1

4

43

545

1.726

1,802

1,158

716

514

392

244

110

48

12

2

1

1

12

44

337

1,081

1,605

1.182

600

274

138

78

38

12

6

1

4

11

129

825

1,361

883

438

229

124

71

42

14

5

1

6

49

181

406

554

820

984

936

706

387

194

118

60

23

2

1

1

3

22

74

346

1,316

2,047

1,521

996

878

613

343

164

52

20

2

2

39 cm.

14

59

233

463

852

1,029

1,089

956

722

410

171

103

49

11

2

1

6

48

401

1,173

1,685

1,277

762

405

223

156

67

28

10

2

3

1

4

44

213

617

944

777

584

372

210

90

37

9

5

1

19

324

1,320

1,770

1.174

712

336

166

63

24

a

6

1

4

21

203

913

1,327

1,179

788

468

228

121

70

27

11

5

1

2
19
199

729

1,043

806

486

282

149

64

28

17

7

2

1

5

26

362

1,461

1,978

1.196

505

195

116

56

19

6

8

2

10

90

640

1,326

1,242

776

413

210

113

53

25

10

3

6

30

156

601

1,145

1,122

752

449

221

143

64

24

16

6

1

3

16

109

684

1,267

1,109

713

356

193

115

50

20

12

4

2

6

62

436

1,248

1,771

1,671

1,217

671

327

128

55

25

9

3

3
23
126

559

1,005

1,023

797

494

360

255

131

80

16

4

2

2

42 cm. ..

14

45cm

132

48 cm....

694

51cm.. ..

969

54 cm.

729

57 cm. ..

531

60 cm

413

63 cm.

272

66 cm.

166

69 cm.

93

72 cm. ..

52

20

78 cm

7

81 cm

1

84 cm.

Total

6,164

7,318

6,147

3,907

5,927

5,408

6,366

3,833

6,924

4,912

4,726

4,138

4,663

7,629

5,428

8,399

4,878

4,075

' Siie groups by 3-cm. intervals.

Table 23. — Size compositions of large haddock, winter seasons
[In thousands of fish]

Length '

1931

1932

1933

1934

1935

1936

1937

1938

1939

1940

1941

1942

1943

1944

1945

1946

1947

1948

30 cm

2

4

25

48

138

314

446

322

380

461

451

327

200

101

40

19

8

1

33 cm.

1

1

2

36

276

837

911

667

396

341

258

167

67

32

9

2

1

36 cm

5

18

41

64

232

448

470

310

220

146

104

51

18

12

6

2

1

1

7

29

90

193

469

561

569

470

279

174

99

43

12

1

1

39 cm

6

96

410

404

420

469

422

332

229

121

67

32

8

1

4

39

157

257

240

179

118

86

60

26

9

5

1

10

87

191

229

161

98

64

36

18

10

3

4

1

12

216

734

748

626

376

276

222

160

82

36

8

2

1

13

119

384

431

364

265

170

116

71

37

16

5

1

1

7

49

220

355

439

406

322

249

165

90

48

20

5

1

4

16

90

315

451

416

318

249

182

124

71

36

12

2

2

16

124

474

734

564

374

229

165

111

67

31

10

2

1

1

2

36

148

366

439

371

303

201

122

70

42

18

3

2

1

10

55

307

636

470

298

197

118

69

36

17

11

2

1

2

14

68

289

432

346

219

145

86

46

3D

12

6

1

2

6

38

137

394

598

624

528

444

364

188

100

44

16

4

1

......

61

146

257

318

310

258

198

148

101

47

17

6

1

3

42 cm

7

94

48 cm

420

51 cm

486

389

67 cm.

326

60cm...

256

63 cm

198

66 cm

136

69 cm

81

72 cm

44

75 cm

15

78 cm

4

81 cm

1

84 cm..

Total

3,006

3,894

1,172

912

3,399

1,993

2.367

2.285

2.894

2,148

2,114

2,128

1,698

2,987

3,287

3,475

1,862

2,461

' Size groups bv 3-cm. intervals.

GEORGES BANK HADDOCK — PART I: LANDINGS

171

Table 24. — Size composition of large haddock, in each of the 18 years
(In thousands of fish)

Length >

1931

1932

1933

1934

193S

1936

1937

1938

1939

1940

1941

1942

1943

1944

1945

1M6

1947

1948

2
4

42

149

463

1,194

2.177

2.864

3,358

3.389

2,548

1,475

795

414

169

71

15

2

1

1

1

22

96

370

1.531

3,853

4,877

4,107

3,309

2,751

1,846

999

491

181

59

14

4

1

2

9

146

1.418

3,987

4,333

3.257

2.704

2.342

1.777

1,100

534

205

69

13

4

1

36 cm

2

25

99

860

3,130

4.271

3.434

2,231

1,288

817

469

222

86

25

4

.......

55

497

2.419

4,259

4.016

2,950

1,948

1,205

698

398

196

76

23

3

2

16

62

412

1,722

3,074

2,986

2.271

1.558

991

550

281

135

50

13

1

"ii

72

651

3,055

4.962

3.701

2.392

1.504

1,077

634

355

169

57

19

5

1

5
22

72

363

2,195

4,534

4,374

2.945

1,757

1.048

650

341

150

60

27

5

1

"is"

49

299

1,605

3.904

4.456

3,521

2,283

1,337

754

378

204

87

24

6

1

8

43

364

2,361

4,359

3,694

2,596

1,681

1,063

586

283

134

57

17

2

.......

61

315

1.939

4,027

3,881

2,611

1,477

863

510

234

95

36

11

5

3

39

222

1,131

3,481

5,341

.5,139

3.824

2,531

1.410

765

410

167

59

18

2

1

6

55

377

1,559

2.947

3.381

2,984

2,079

1,775

1,117

614

304

74

28

5

1

39 cm

27

237

1,190

2,883

4,769

5.193

4.832

3,900

2,603

1,402

625

289

111

18

4

2

1

21

112

901

3,032

4.471

3.788

2.626

1,783

1,183

730

339

134

35

15

5

1

9

82

510

1.713

2,554

2.201

1.688

1.209

726

367

168

55

24

5

4
53

794

3,124

4.215

3.340

2,304

1,397

872

474

210

86

22

4

6

42 cm

51

45 cm,..

48 cm

418
1,995

51 cm.

.54 cm

2,876
i,5.58

1.968

60 cm

1.433

1.054

637

69 cm

388

72 cm

235

66

20

81 cm

3

87 cm --

Total

28,086

21,902

19, 176

11.311

16,899

16,963

18, 754

14,124

18,692

18. 549

18,920

17.249

16,080

24,542

19, 132

24,512

17.306

13.709

• Size groups by 3-cm. intervals.

Table 25. — Average size composition of targe haddock, in
each of the seasons

(In thousands of flsb]

Table 26. — Size composition of targe haddock in the
average year

[In thousand!! of flshj

Length 1

Spring

Summer

Fall

Winter

36 cm . .

2

10

38

216

840

1.370

1.307

1,020

710

456

256

132

60

19

7

1

8

41

264

922

1,367

1.114

744

467

281

156

74

34

14

3

1

2

39cm.

3

21

126

457

828

868

731

524

356

203

100

42

14

3

6

27

45 cm

129

48 cm

349

468

429

57 cm

346

269

192

66cm

120

65

31

75 cm .

12

3

81 cm

1

Total

4.276

6,444

5,491

2,449

' Size groups by 3-cm. intervals.

Length '

Average
number

Percent

36 cm --

4

27

128

735

2,569

4.032

3,718

2,841

1,970

1,285

736

371

167

59

16

3

39 cm

0.1

.7

3.9

48 cm .

13.8

21.7

19.9

15.2

10.6

63 cm

6.9

3.9

2.0

.»

75 cm .

.3

.1

Total

18.661

100.0

1 Size groups by 3-cm. intervals.

Table 27. — Size compositions of total haddock, spring seasons
[In thousands of fish]

Length '

1931

1932

1933

1934

1935

1936

1937

1938

1939

1940

1941

1942

1943

1944

1946

1946

1947

1948

1

1

""""9'

40

105

280

562

984

1,362

1.440

1,200

901

608

412

232

122

54

17

2

1

3

13

108

555

1,211

1,121

822

1,235

1,644

1,558

1,247

944

604

363

198

101

52

23

6

1

27 cm

1

28

74

98

153

379

739

970

894

815

674

435

306

174

87

34

10

1

2
30
113

174

189

321

558

734

779

703

610

448

307

183

92

44

19

5

5'

33

125

386

1,127

2,023

1,992

1,438

1,063

825

586

382

197

94

44

14

4

1
12
63

208

778

1,551

1,740

1,571

1,399

1,094

722

434

260

165

68

26

8

4

30 cm

16

62

196

431

893

1.412

1,569

1,537

1,185

742

364

132

51

18

7

31

292

928

1,504

1,390

879

723

755

834

714

497

300

148

43

16

2

9

37

162

462

969

1,267

1,133

886

809

717

561

416

266

167

78

26

10

2

1

""ie'
101

296

663

1,101

1,658

1,482

1,061

688

402

241

160

88

42

10

5

1

2
11
63

257

516

762

1,077

1,213

1,062

735

477

283

172

84

39

16

4

2
33
169
342

507

686

794

730

585

350

185

87

32

15

9

15
42
117

2

44

172

507

1,009

1,115

1.176

904

753

632

450

282

118

41

7

4

2

14

63

247

415

432

434

395

317

231

153

99

47

18

6

4

1

13

68

148

207

226

268

292

233

178

140

76

38

17

3

10

76

385

2

36 cm. .

87

39 cm...

531

316 908

1,047

632

720

613

551

453

322

228

109

46

19

9

995

1,010

1,117

1,155

971

641

545

275

122

63

7

1

970

48 cm . . .

780

51 cm..

699

651

590

60 cm. .

410

63 cm . . -

346

228

69 cm.

162

72 cm , . .

64

19

1

•81 cm

1

84 cm

Total.. -.

8,609

9,063

7,216

2.877

1.908

5,872

8,332

5,311

7,978

7,915

11,809

10,338

10, 104

6,773

4,517

4,201

8,291

6,588

' Size groups by 3-cm. intervals.

172

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Table 28. — Size compositions of total haddock, summer seasons
[In thousands of flsh]

Length '

1931

1932

1933

1934

1935

1936

1937

1938

1939

1940

1941

1942

1943

1944

1945

1946

1947

1948

1

2

5

19

128

636

1.561

1.735

1.680

2, 115

1,716

1,119

701

410

257

146

60

24

5

14

152

290

373

524

650

636

873

1,412

1.647

1.383

933

628

424

242

128

56

13

8

2

""17'

265

1,123

1,741

1,470

1,368

1, 570

1,281

895

568

318

190

116

67

28

11

1

1

3

16

62

397

1.281

1.497

1.065

1.265

1,321

1,140

873

584

354

179

90

39

12

4

2
4

15

163

949

2.052

1.939

1.458

1.952

2.071

1,833

1.472

927

552

291

153

86

30

10

2

27 cm

1

10

106

531

1,232

1.770

2,829

3, 473

2,402

1,465

1,046

669

439

249

111

59

27

10

1

1

24

214

655

1,282

2,182

2.319

2.125

1.909

1,505

1,001

562

332

187

87

38

10

2

1

U

29

211

570

989

1,173

1,976

2,194

1,728

1,419

1,332

1,108

652

359

181

66

14

8

1

30 cm. ..

1

16

114

661

1.621

2,125

1,718

1,095

803

758

773

630

389

209

82

32

7

2

1

2
12

103

228

495

893

1.092

854

874

690

543

327

160

74

25

9

1

13

189

625

917

1, 2.38

1.594

1.611

1.371

987

607

344

175

66

22

5

1

1

25

345

1,064

1.791

2,177

2.350

1,967

1,254

804

520

380

202

112

54

13

5

2

9"
134

589

1,188

1,524

2,092

2,153

1.700

1.180

722

451

273

149

65

28

13

2

4

10

86

461

1,091

1,567

2,080

2,165

1.870

1.306

913

521

291

172

60

22

10

2

""29"

344

917

807

623

886

1,066

1,204

1,264

806

411

216

108

37

14

6

33 cm

17

556

1,366

1,626

1,363

1,126

916

917

906

686

672

439

260

114

34

17

2

.36 cm-._

8

75

286

615

1.343

2,116

2,139

1.784

1,427

910

507

255

103

36

7

2

1

1

696

39 cm...

1 759

42 cm-

2,439
2,488

48 cm.

1 743

51 cm

1,040
825

57 cm

60 cm

63 cm._

66 cm

69 cm

621
356
238
117
52

72 cm.

75
12

78 cm.

8

81 cm

84 cm

Total

11,615

11,037

10,388

6,381

9,766

12,321

11,029

10, 173

13,066

12,272

15,961

16, 430

14,436

12,611

8,737

14.021

10,907

12,421

I Size groups by 3-cm. intervals.

Table 29. — Size compositions of total haddock, fall seasons
[In thousands of fish]

Length 1

1931

1932

1933

1934

1935

1936

1937

1938

1939

1940

1941

1942

1943

1944

1945

1946

1947

1948

24 cm

2

30

166

383

386

1,054

2.466

2,598

1,907

1,515

1.198

788

468

228

121

70

27

11

5

1

10

69

136

664

2,525

4,576

3,336

1,707

1.422

1, 157

754

449

221

143

54

24

16

27 cm

1

17
44

254

1,234

1,991

1,522

1,546

1,638

1,278

762

405

223

156

67

28

10

2

3

1

4

17

103

346

1,310

2,734

2,509

1,857

1,745

1, 196

602

274

138

78

38

12

5

1

6

48

183

242

415

1,201

1.625

1,716

1,673

1,289

779

414

210

113

53

25

10

3

1

5

58

649

1,905

2.305

1.914

1.920

1,625

917

441

229

124

71

42

14

5

1

1

6
12

180

861

1,425

1,204

767

852

1,000

938

706

387

194

118

60

23

2

1

1

1

8

36

270

906

1.570

1,860

2,114

2,211

1,632

996

878

613

343

164

52

20

2

2

30 cm --..

1

7

127

750

1.358

1,010

666

880

1,036

1,090

956

722

410

171

103

49

11

2

1

.-

30

322

1,590

3.137

3,088

2,005

1.179

718

614

392

244

110

48

12

2

1

2

41

362

1,098

1,140

906

1,002

1,011

778

585

372

210

90

37

9

5

1

1

24

256

1,311

2.192

1.972

1,980

1.881

1, 181

712

336

166

63

24

11

6

1

i

40

370

2,293

4,606

3,658

1,821

1.220

830

489

282

149

64

28

17

7

2

1

1

43

364

1,696

3,288

3.640

2,997

2,286

1.223

508

195

116

55

19

6

8

2

3

41

337

839

1,237

1,662

1,846

1,548

1,133

715

356

193

115

50

20

12

4

2

3

50

139

321

794

1,365

1,666

1,848

1,685

1,219

671

327

128

55

25

9

3

4

54

1.122

4,253

4,505

2,331

1,480

1,152

1,047

801

494

360

255

131

80

16

4

2

4
104

36 cm ---

39 cm

1,076
2,160
2,403

45 cm-

2,394

48 cm

1,935
1.195

761

57 cm

537
415

63 cm...

66 cm

272
156
93

72 cm

75 cm.

52
20

78 cm

7
1

84 cm

Total .

9,350

13,393

11,182

7,649

12, 117

12, 969

13, 422

15, 778

16,237

10,005

17,261

12,226

10, 113

10, 308

8,738

13,568

18, 091

13.585

' Size groups by 3-cm. intervals.

GEORGES BANK HADDOCK — PART I: LANDINGS

Table 30. — Size compositions of total haddock, winter seasons
(In thousands of flsh]

173

Length '

1931

1932

1933

1934

1935

1936

1937

1938

1939

1940

1941

1942

1943

1944

1945

1946

1947

1948

2
11

140

485

632

644

1,001

1.561

1,452

884

537

377

276

222

160

82

36

8

2

16

80

109

176

293

399

291

235

235

161

98

64

36

18

10

3

4

5

37

168

343

363

473

684

634

467

369

266

170

116

71

37

16

5

1

2

18

74

149

156

217

444

512

434

448

407

322

249

155

90

48

20

5

1

4

67

243

418

648

1,215

1,266

796

556

427

320

249

182

124

71

35

12

2

2

28

135

434

721

842

1,011

984

850

576

375

229

165

111

57

31

10

2

1

1
63
321

671

437

329

514

616

561

487

311

220

146

104

51

18

12

6

2

1

7

55

114

169

404

1.078

1,448

846

512

465

372

303

201

122

70

42

18

3

2

1

10

49

204

780

1.361

1.I3I

830

668

484

299

197

118

69

36

17

11

2

1

1

34

694

2,060

2,360

1,615

678

439

460

423

332

229

121

67

32

8

2

11

62

240

586

771

566

333

381

461

451

327

200

101

40

19

8

1

3

24

107

335

699

732

690

672

638

531

445

354

188

100

44

16

4

1

"'"32"

254

813

883

495

322

299

321

311

258

198

148

101

47

17

6

1

4

2

20

154

603

1.121

1.282

970

563

396

341

258

167

67

32

9

2

1

14

68

190

366

270

220

265

241

179

118

86

50

26

9

5

1

5

63

201

288

349

497

472

353

220

145

86

46

30

12

6

1

2

5

29

59

108

281

300

467

561

569

470

279

174

99

43

12

1

105

36 cm

8»«

39 cm -

1,715

1.544

45 cm

1,226

48 cm

996

620

406

57 cm

329

60 cm

256

198

136

69 cm

81

44

15

4

81 om

1

Total...

9,553

5.988

2.108

2,228

8.512

4,225

3,751

6,635

6,564

4,771

6.231

6.268

2,776

3.457

4,560

5,583

4,506

8.574

' Size groups by 3-cm. intervals.

Table 31. — Size composition of landings of total haddock, in each of the 18 years

(In thousands of fish)

Length i

1931

1932

1933

1934

1935

1936

1937

1938

1939

1940

1941

1942

1943

1944

1945

1946

1947

1948

1

2

15

101

473

1.423

3,387

5,321

,5,612

5,576

4,822

3,499

2.243

1,289

817

469

222

86

25

4

1

3

32

193

514

904

2,613

4.985

5.496

6.149

4,959

4,127

2,991

1,966

1,207

698

398

196

76

23

3

1

6

34

237

968

2,993

6.102

8,416

7,477

6,149

5.663

4,702

3,542

2,283

1,337

754

378

204

87

24

6

14
163

307

433

890

2,246

3.500

3,674

4,293

4,726

3,806

2.627

1.783

1,183

730

3.39

134

35

15

5

1

.......

84

164

655

1.682

2,281

2,505

2,761

2,734

2,208

1.690

1.210

726

367

168

55

24

5

2

11

142

523

1,090

2.648

4.258

4,978

5,252

4,644

3,381

2,309

1,397

872

474

210

86

22

4

i

9

114

458

1,359

4,411

7,639

6,447

4,606

3,876

3.100

2,292

1,563

992

550

281

135

50

13

1

27 cm

2

39

240

1,295

3.843

6,890

7.995

7.464

5,989

3,S62

2,404

1,505

1.077

634

355

169

57

19

5

1

7
111

529

1,048

1,737

3,381

4,764

5,982

5,869

4,637

2,958

1,758

1,048

650

341

160

60

27

5

1

3

30

246

1,509

4.303

6.563

7.897

8,125

6,133

3.929

2.611

1.681

1.063

586

283

134

57

17

2

2

39

323

1.263

3.100

5,258

6,070

6,039

6,328

4.085

2,658

1,497

871

513

235

96

36

11

5

9'

76

317

1,098

2.509

3.965

5.123

5.683

5.178

3,829

2.531

1.410

765

410

167

59

18

2

1

8

52

588

2. 051

2.987

2,910

2.726

2.937

3,379

3,393

2.548

1.475

795

414

169

71

15

2

1

12

49

286

989

2,347

3,768

6,190

5,718

6.224

4.140

3,312

2,753

1.847

999

491

181

59

14

4

30 cm

3

42

844

2.947

4,200

3.671

3.5<I0

4.847

5,204

4.834

3,900

2,603

1,402

625

289

HI

18

4

2

1

8

50

456

2.065

5,318

7.773

6,967

4,793

3,300

2,706

2,342

1,777

1.100

534

205

69

13

4

1

4

113

2,008

6,817

7,822

5,174

3,938

3,484

3,460

2,989

2,079

1.776

1,117

614

304

74

28

5

8

33 cm

263

2,763

6.166

42 cm

7,433

7,078

5.454

51 cm

3,554

54 cm

2,643

1,977

1,437

63 cm.

1,054

637

388

72 cm .

235

66

78 cm.

20

3

84 cm

87 cm

Total

39. 127

39,481

30.894

19,335

32,303

35, 387

36,534

37, 897

43,845

34,963

51,262

45,262

37,429

33. 149

26,552

37.373

41.795

41,168

* Size groups by 3-cm. intervals.

174

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Table 32, — Average size composition of total
each of the seasons
[In thousands of fish]

haddock, in

Table 35. — Division of landings for each size

Length '

Spring

Summer

Fall

Winter

24 cm

1

10

23

81

395

995

1,380

1,570

1,773

1,641

1,339

1,025

712

456

256

132

60

19

7

1

1
12

66

157

349

664

933

1,035

1,012

896

735

525

367

204

100

42

14

3

3
19

76

398

1,397

2,299

2,135

1,779

1,539

1,134

746

467

281

156

74

34

14

3

1

3

30 cm

28

33 cm

107

36cm --

294

39 cm

567

42 cm

797

844

4Scm ...

692

51 cm . -

539

54 cm

438

347

60 cm

269

63cm

192

66 cm.

120

69 cm

72cm

65
31

12

3

1

Total

7,095

11,876

12,555

5,349

' All values calculated by dividing 18-year total for total haddock by 18
rather than by summing 18-ye.ar averages of scrod plus large.
' Size groups by 3-cm. intervals.

Table 33. — Size composition of total haddock in the average

year

[In thousands of fish]

Length i

Average
number

Percent

1

17

82

320

1,244

3,308

5,140

6,482

5,279

4,731

3.807

2,853

1.973

1,286

736

371

167

99

16

3

27 cm . .

1

30cm

2

33cm-.

.9

36 cm

3 4

39 cm

9

13.9

14.9

48 cm .

14 3

51 cm

12.8

10.3

7.7

60 cm .

6.4

63 cm

3.5

66 cm

2.0

69cm...

1.0

72 era

.4

75 cm

.2

78 cm

81 cm

Total

36, 876

100.0

' Size groups by 3-cm. intervals.

Table 34. — Undersized haddock landed, by years
(In thousands of fish]

Year

Number of
fish

1931

3,836

1932

2.579

1933

4,043

1934

2,601

1935

4,416

1936

6,402

1937

4,260

1938... .

6,352

1939

5.419

1940

3,432

1941 .

10,341

1942

6.091

1943

4,727

1944

1,500

1946 . .

2,700

1946

3.683

1947

8,942

1948

9,189

Total... .

89. 513

Average .

4.974

Length '

Percent of landings

Scrod

Large

100.0

99.7

99.2

97.5

86.6

51.3

14.8

2.3

.4

.2

.1

0.3

39 cm

.8

42 cm .. .

2.5

13.4

48 cm

48.7

51 cm ..

85.2

97.7

99.6

60 cm .. .....

99.8

99.9

66 cm and over

100.0

49.4

60.6

1 Size groups by 3-cm. intervals.

DISCUSSION AND SUMMARY

1. Presented in this paper is an outline of a
study of Georges Bank haddock and also details
of landings for the years of 1931 to 1948. Pounds,
numbers, and average weights of fish, and size
compositions of landings are given for scrod, for
large, and for total haddock. While these data
are presented primarily as backgi-ound for further
studies, the averages and ranges are informative.
The values presented, in our opinion, are as nearly
complete a record of the quantities of Georges
Bank haddock that were landed and sold as can
be readily assembled. They are more nearly
complete than values previously given (Schuck
1949), which represent only Georges Bank had-
dock landed at the ports of Boston, Gloucester,
and New Bedford, Mass., and Portland, Maine.

2. The industry is most affected, not by the
average or ordinary condition of the fishery, but
by deviations from the normal, be it in terms of
pounds of fish, of numbers of fish, of numbers of
certain sizes as compared with previous years, or
of a change in the seasonal cycle of the above.
But, in order to measure deviations, it is first
necessary to determine the norm from which they
deviate. We can define the average year as fol-
lows: In the average year (during the period 1931-
1948) there were 94,196,000 pounds of haddock
(30,79 1 ,000 pounds of scrod and 63,405,000 pounds
of large) landed from Georges Bank. The aver-
age weight of these fish was 2.55 pounds (1.69
for scrod, 3.40 for large) and 36,875,000 individual
fish (18,214,000 scrod and 18,661,000 large) were
landed. Of these numbers landed, there were
practically none less than 27 centimeters (9.6
inches), and none more than 81 centimeters (32.1
inches) in length. The 45-centimeter (17.9-inch)

GEORGES BANK HADDOCK — PART i: LANDINGS

175

group contained the most fish and over 66 percent
of all haddock landed were between the 42-centi-
meter (16.2-inch) group and the 54-centimeter
(22.1-inch) group in length.

Also in the average year about 4,974,000 fish
or 13.5 percent of the total number landed were
smaller than the established minimum market
size of IM pounds.

3. So far as subareas of Georges Bank are con-
cerned, in the average year (1936 to 1948 only)
the Northern Edge, though not the largest area,
has been the largest producer, with 35 percent of
the total poundage.

Percentages for scrod, large, and total haddock
from the four areas are as follows:

Total
Scrod Large haddock

Northern Edge 39.5 32.9 35.2

Southeast Part 26.3 23.3 24.4

South Channel 28.6 36.4 33.6

Southwest Part 5. 6 7. 4 6. 8

100. 100.

100.

4. The seasonal landings, for the average year,
are shown in table 36 by pounds, numbers, and
average weights.

Table 36. — Seasonal average weights and quantities landed

Pounds of

fish
(thousands)

Number of

flsh
(thousands)

Average
weight per

flsh
(pounds)

Spring:

Scrod --

5,273
15.899

2.819
4,276

1.871

3.718

Total

21, 172

7,095

2.984

Summer:

Scrod -

8,448
20,389

5,430
6,444

1.556

3.163

Total

28,837

11,876

2.430

Fall:

Scrod

12, 147
18, 152

7,064
5,491

1 719

Large

3.306

Total

30,299

12. 555

2 413

Winter:

Scrod _.

4.923
8,966

2,901
2,449

1.697

Large - - - _,

3 661

Total

13,888

5,349

2 596

Year:

Scrod

30, 791
63,405

18,214
18,660

1 691

Large

3 398

Total.-

94,19&

36,875

2 554

From table 36, we have computed the percent
by weight and the percent by number for scrod,
large, and total haddock of the year's landings.
They are as follows:

Scrod: By weight By number

Spring 17.1 15.5

Summer 27.4 29.8

Fall 39.5 38.8

Winter 16.0 15.9

Total year 100.0 100.0

Large :

Spring 25.1 22.9

Summer 32.2 34.6

Fall 28.6 29.4

Winter 14.1 13.1

Total year 100.0 100.0

Total haddock:

Spring 22.5 19.2

Summer 30.6 32.2

Fall 32.2 34.1

Winter 14.7 14.5

Total year 100.0 100.0

Landings of undersized haddock were greatest
in the fall season, when 38 percent of the yearly
average landings of undersized fish occurred.
The summer season accounted for 30 percent, the
winter season for 20 percent, and the spring
season for the least quantity, 12 percent. Con-
sidering each season separately, the percentages
of haddock landed that were undersized are as
follows:

Percent
undersized

Spring 8. 1

Summer 12. 7

Fall 15. 1

Winter 18. 7

Total year 13. 5

5. Having thus developed average values of
important characteristics of the landings, each
individual year can be evaluated by comparing it
with these norms. For instance, considering 1934
(the poorest year of haddock production), we see
that only 12,976,000 pounds of scrod as compared
with the average of 30,791,000 pounds were
landed; only 36,908,000 poimds of large haddock
as compared with the average of 63,405,000; and
only 49,884,000 pounds of all haddock as com-
pared with the average of 94,196,000. Average
weights for 1934 as compared to the average year
were:

l9Si Average year

Scrod 1.62 1.69

Large 3.26 3.40

Total haddock 2.58 2.55

176

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

The numbers of fish landed in 1934 as compared
with 18-year averages were: scrod 8,024,000
(18,214,000), large 11,311,000 (18,661,000), total
haddock 19,335,000 (36,875,000).

In addition to such yearly deviations, seasonal
deviations for 1934 can be compared with average
seasonal values, and subarea contributions can be
evaluated in terms of average subarea contribu-
tions.

6. For a rapid evaluation of how each of the 18
years deviate in the more important characteristics
from the average year, table 37 has been prepared.
Shown are the percentages that the individual
years are above or below the 18-year average;

pounds, nimibers, and average weights are treated,
for large, scrod and total haddock.

7. The data in this paper serve (1) as a record
of the total landings of haddock from Georges
Bank in terms of pounds, average weights, num-
bers and sizes of scrod, large, and total haddock,
by seasons and years over the 18-year period,
1931 to 1948; and (2) as a basis for developing
other data, among which wUl be the age composi-
tion of the landings; the size of various ages;
year class contributions; and estimates of the
relative size of the stock on the banks, of rates of
dechne of year classes, and of mortahty rabes.

Table 37. — Percentage deviations of quantities and average weights from the average year

Pounds:

Scrod

Large

Total

Numbers:

Scrod

Large

Total-.-

Average weights (pounds)

Scrod

Large

Total

1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 194S 1946 1947 1948

-43.2
53.8
22.1

-39.4
50.5
6.1

-6.2
2.2
15.1

2.3
16.6
11.9

-3.5
17.4
7.1

6.0

-.7
4.5

-38.0

-.9

-13.3

-35.7

2.8

-16.2

-5.1

-3.6

3.4

-57.9
-41.8
-47.0

-55.9
-39.4
-47.6

-4.3

-4.0

1.0

-17.1
-15.4
-15.9

-16.4
-9.4
-12.4

-1.9
-6.6
-4,0

-2.7
-14.7
-10.8

1.2
-9.1
-4.0

-3.8
-6.2
-7.1

1.0
1.5
1.3

-2.4

.5

-.9

3.4
1.0
2.3

29.

-17.

-1.

30.

-24.

2.

40.1
-3.2
11.0

38.1

.2

18.9

1,4
-3.3

-5.7

-3.9

-.6
-1.6

-.6
-5.2

6.7

3.7

60.7
-9.1
13.7

53.8
-7.6
22.7

4.5
-1.7
-7.4

21.1
-17.
-4.

17.:
-13.1

1..

3.!
-4.

-6.;

-50.5

27.4

1.9

-52.8

31.5

-10. I

4.8
-3.2
13.4

-62.

5.

-16.

-59.

2.

-28.

-6.
2.

16.

-31.4
30.5
10.3

-29.4

31.4

1.4

-2.9
-.6
8.8

32.8
1.5
11.8

34.4
-7.3
13.3

-1.2

9.4

-1.4

44.7
-22.8

-.7

50.8

-26.5

11.6

-4.0

5.1

-11.1

LITERATURE CITED

Herrington, William C.

1933. Conservation of immature fish in otter trawling. Trans. Amer. Fish. Soc, vol. 62 (1932), pp. 57-63.

1935. Modifications in gear to curtail the destruction of undersized fish in otter trawling. Bureau of Fisheries, U. S.
Dept. Commerce, Investigational Report No. 24, 48 pp.

1936. Decline in haddock abundance on Georges Bank and a practical remedy. Bureau of Fisheries, U. S. Dept.
Commerce, Fishery Circular No. 23, 22 pp.

1941. A crisis in the haddock fishery. Fish and Wildlife Service, U. S. Dept. Interior, Fishery Circular No. 4, 14 pp.
1944. Factors controlling population size. Trans. Ninth North Amer. Wildlife Conf., 1944, pp. 250-263.

1948. Limiting factors in fish production. Some theories and an example. Bulletin, Bingham Oceanographic Col-
lection, vol. 11, Article 4, pp. 229-283.

McKenzie, R. a.

1946. The haddock fishery of grounds fished by Canadians. Bull. 69, Fish. Res. Bd. Can., 1946, 30 pp.
Needler, a. W. H.

1930. The migrations oi haddock and the interrelationships of haddock populations in North American waters.
Contr. Canad. Biol. Fish., N. 8., vol. 6, No. 10, 1930, pp. 243-313.

Rounsefell, George A.

1942. Field experiments in selecting the most efficient tag for use in haddock studies. Trans. Amer. Fish. Soc, vo^.
71, 1941, pp. 228-235.

1948. Development of fishery statistics in the North Atlantic. U. S. Fish and Wildlife Service, Spec. Sci. Report
No. 47, 18 pp.

Russell, E. S.

1942. The overfishing problem. Cambridge Univ. Press, London, 1942, 130 pp.
Schroeder, William C.

1942. Results of haddock tagging in the Gulf of Maine from 1923 to 1932. Sears Foundation: Jour. Marine Res.,
vol. 5, No. 1, June 1942, pp. 1-19.

ScHucK, Howard A.

1949. Relationship of catch to changes in population size of New England haddock. Amer. Stat. Assn.: Biometrics,
vol. 5, No. 3, Sept. 1949, pp. 213-231.

ScHucK, Howard .\., and Edgar L. Arnold, Jr.

1951. Comparison of haddock from Georges and Browns Banks. U. S. Fish and Wildlife Service, Fishery Bulletin
67, vol. 52, pp. 177-185.

UNITED STATES DEPARTMENT OF THE INTERIOR, Oscar L. Chapman, Secretary
FISH AND WILDLIFE SERVICE, Albert M. Day, Director

COMPARISON OF HADDOCK FROM
GEORGES AND BROWNS BANKS

By HOWARD A. SCHUCK and EDGAR L. ARNOLD, JR.

FISHERY BULLETIN 67

From Fishery Bulletin of the Fish and Wildlife Service

VOLUME 52

UNITED STATES GOVERNMENT PRINTING OFFICE

WASHINGTON : 1951

For sale by the Superintendent of Documents, U. S. Government Printing Office, Washington 25, D. C.

Price 15 cents

CONTENTS

Page

Collection of data 179

Size composition 179

Sizes at various ages 180

Summary 185

Literature cited 185

II

COMPARISON OF HADDOCK FROM GEORGES AND BROWNS BANKS

By HOWARD A. SCHUCK and EDGAR L,

Two large areas in the Northwest Atlantic
Ocean are of utmost importance to the United
Slates haddock fishery. These are the Georges
Bank area and the chain of Nova Scotian banks.
From these two areas comes over 95 percent of the
llnited States production of haddock. In the
years 1931 to 1949, the Georges Bank area pro-
duced ahout 2,092,000,000 pounds (round weight)
of haddock and the Nova Scotian banks better
than 910,000,000 pounds.

These two areas are close geographically but
are separated by the relatively deep Fundian
Channel. The question of the effectiveness of
this channel as a barrier to the passage of had-
dock (Melanogrammus aeglejinus) between the
Georges Bank area and the group of Nova Scotian
l)anks is economically and scientifically important.
Its answer, among other things, determines
whether the haddock stocks in the two areas can
be expected to fluctuate simultaneously or whether
they must be considered separately in interpreting
observed fluctuations in abundance.

It is possible that some intermingling of the
egg or fry stages may occur between the two banks.
Walford (1938), however, concluded that during
1931 and 1932 (the only years in which the drift
of young has been studie-d) Georges Bank, at
least, had received no recruits from other areas.

Regarding the bottom-dwelling stages of had-
dock, various investigators (Needier 1930, Her-
rington 1944) expressed the opinion that inter-
migrntion between the two areas is negligible,
and that the populations iiduibiting the two areas
are largely independent. At present, direct evi-
dence from the movement of marked fish is
limited. Returns from haddock tagged in shallow
inshore waters have been obtained (Needier 1930,
Sehrocder 1942, Rounsefdl 1942, United States
Fish and Wildlife Service unpublished records), but
early tagging of large groups of haddock located
off shore was \msuccessful. The extremely deli-
cate haddock require special methods of collecting

954348 O - 51

ARNOLD, JR., Fishery Research Biologists

and handling, particularly in deep water, if
returns are to be obtained. Recent attempts at
off.shore tagging from the Albatross III are proving
successful, l)ut it will be some time before enough
returns are available to determine how much mi-
gration occurs across the Fundian Channel.

As for indirect lines of evidence, Vladykov
(1935) has shown small differences in the average
numbers of vertebrae in haddock from Georges
Bank and the Nova Scotian banks. The sig-
nificance of the differences is not known, as no
measures of variation of these averages were given.
Other data by Needier (1930) indicate differences
in the size composition and the growth rate be-
tween Nova Scotian and Georges Bank haddock.
But again only averages were given and the sam-
ples were taken by commercial gear which ex-
cluded the younger ages and possibly exercised
selection for the larger sizes of certain ages.

Recent data collected on a cruise of the Albatross
III, research vessel of the United States Fish
and Wildlife Service, make possible a critical
comparison between the haddock from Georges
Bank and those from Browns Bank, the Nova
Scotian bank lying closest to Georges. By such
a comparison, it is the purpose of this report to
consider further the effectiveness of the Fundian
Channel as a barrier to bottom-dwelling stages
of haddock. In effect, this study supplements
Needier (1930) by including younger fish and by
providing stringent statistical comparison of data
from the two l)anks.

In collecting the original data for this study
John B. Colton, -Jr., Frank A. Dreyer, Freeman
A. Pluff, Louis D. Stringer, and Roland L. Wigley
assisted. Sterling L. Cogswell am! Richard E.
Sayles prepared the scal(>s for study, and Manuel
Vieira prepared the illustrations. Robcit Kirk-
I)atrick summarized the 1950 Browns Bank data,
and John C. Marr, Chief, South Pacific Fishery
Investigations, reviewed the manuscript.

177

178

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

HADDOCK FROM GEORGES AND BROWNS BANKS

179

COLLECTION OF DATA

Cruise 23 (June 23 to June 29, 1949) of the
Albatross III was made primarily to tag haddock
on Georges and Browns Banks. However, h-ngth
measurements and scale samples were obtained con-
currently from a substantial number of fish on each
of the two banks, and these data form the basis
for this report.

The mesh in the otter trawl used was small
enough, 2-inch stretched measure, to obtain a
representative sample of all sizes and ages of
bottom-dwelling haddock (other than young of
the year) in a given area. The samples were
obtained from two locations on Browns Bank
and from five locations on Georges Bank (fig. 1).
These locations were not selected at random,
but all fish caught on the two banks were taken
in nets of the same size, fished in the same manner.

SIZE COMPOSITION

During this cruise, 10,163 haddock were caught
in 61 tows, 9,321 in 45 tows on Georges Bank
and 842 in 16 tows on Browns Bank. The
size compositions ' of these catches are shown
in table 1. The percentage size compositions
of the catches from the two banks also are shown
in table 1 and are plotted in figure 2. From
these data it can be seen that there is a marked
difference in the size compositions of the catches
from the two banks.

< By fork Icnpth, from lip of snout to fork of tail. All lenKths were re-
conlpil by continicti'rs, that is, lefiRllis from 20.0 contimeters to and including
20.9 centimeters were recorcieci as 2t).0 centimeters, lengths from 21.0 centi-
meters to and including 21.9 centimeters were recorded as 21.0 centimeters,
and so on. Data are arranged in .1-ctMitimeier groups, that ii». *JD-. 2I-. and
22-centimeter fish arc groupi'd as 21 -centimeter fish; 23-, 24-. and 2S-ccntimctcr
fish are grouped as 2-1-centimeler fish, and so on.

BROWNS BANK

20

25

45

Figure 2.-

30 35 40

LENGTH IN CENTIMETERS

-Percentage size compositions of haddock catches from Georges and Urowiis Batiks.

50

55

180

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Table 1. — Size compositions of haddock catches from
Georges and Browns Banks

Georges Bank

Browns Bank

Length in 3-cen1imeter groups '

Number

Percent

Number

Percent

29
160
129
99
62
81
41
32
47
53
42
46
12
10
4
4
1

3.44

18 centimeters

511

2,973

3,180

734

75

182

410

376

298

239

169

117

40

18

3

3

6.48

31.90

34.12

7.87

.81

1.95

4.40

4.03

3.20

2.66

1.71

1.26

.43

.19

.03

.03

.01

19.00

15 32

24 centimeters

11.76

27 centimeters

6.18

9.62

33 cent iineters

4.87

3ti centimeters .

3.80

5.58

42 centimeters

6.29

4.99

48 centimeters

5.40

51 centimeters . .-

1.42

I 19

57 centimeters

,48

.48

. 12

2

.02

Total

9.321

100.00

842

100,00

' See text footnote 1.

SIZES AT VARIOUS AGES

Without sonic method of age determination,
we could only speculate about the ages of the fish
represented by the modes in these size distribu-
tions. Fortunately the age of haddock, at least
for the ages represented here, can be assessed
accurately by microscopic examination of impres-
sions of their scales. Figure 3 shows impressions
of scales of 1-, 2-, 3-, and 4-year-old haddock
collected on this cruise.

Scale samples were taken from 1,285 haddock,
823 from Georges Bank and 462 from Browns
Bank. Tables 2 and 3 show the distribution of
these fish by size, and the number and percentage
of fish from each size group that wei-e assigned to
each age on the basisof scale examination. From
the percentages thus obtained, it was possible to
estimate how many fish in the total catch were
of each age.

It was necessary to determine tlie number of
each age in the entire catch, rather than to use
only the age samples of tables 2 and 3, because
scales were taken from more large fish than from
small, in proportion to their abundance. This
was done because of the relative scarcity of
larger sizes and because of the greater number of
ages that make up the size groups of larger fish.

The age composition of the total catch was ob-
tained by allotting the total catch of each size
group (table 1) to the various ages on the basis of
the percentages shown in tables 2 and 3. For
example, the Georges Bank age analysis showed
that, of all 18-centimeter fish for which age read-
ings were made, 100 percent were 1-year olds.
Accordingly, the total catch (511) of 18-centi-
meter haddock taken on Georges Bank were con-
sidered to be 1-year-old fish. Likewise, of all
36-centimeter fish for which the ages were read,
92.1 percent were 2-year-olds and 7.9 percent
were 3-voar-olds. Thus, of the 410 fish of 36

Table 2. — Age composition of 823 Georges Bank haddock, by scale analysis
[In parentheses is the percentage that each age contributed to the total for each sl7.el

Length In 3-centimeter

Number and percent in age group—

Total
number,
all ages

groups '

1

2

3

4

6

6

7

8

9 and over

3 (100.0)
39 (100.0)
39 (100.0)
18 (100.0)

6 (46.2)

3

21 centimeters

39

39

27 centimeters

18

7 (53.8)
65 (100.0)
139 (92, 1 )
106 (67, 7 )
34 (30.6)
2 (2.2)

13

33 centimeters

65

36 centimeters

12 (7.9)
.50 (32.3)
75 (67.6)
69 (77.fi)
35 (56.4)
10 (20.4)

161

155

42 centimeters. . ..

2 (1.8)
18 (20.2)
23 (37.1)
35 (71,4)
11 (78.6)

3 (37.5)

HI

45 cenlimeters

89

4 (6. 6)
4 (8.2)

2 (14,3)

3 (37.6)
1 (60.0)

62

49

1 (7. 1 )
1 (12.5)

1 (,50.0)

2 (100,0)
1 (100.0)

14

57 centimeters.. ..

1 (12.5)

8

60 centimeters

2

2

66 centimeters

1

72 centimeters

1 (50.0)

1 (60.0)

2

All sizes

105

3S2

251

92

14

6

2

1

823

1 See text footnote 1.

HADDOCK FROM GEORGES AXD BROWNS BANKS

181

Table 3. — Age composition of 4^2 Browns Bank haddock, by scale analysis
[In parentheses is the percentage that each age contributed to the total for each size]

Length in 3-centimeter
groups '

15 cen
18 cen
21 cen
Z'l cijn
27 cen
30 ci'ii
33 cen
36 cen
39 ecu
42 cen
45 cen
48 cen
51 cen
54 cen
57 cen
fiOccn
63 cen

timeters..
timctcrs.,
timeters,.
timeters..
timeters. -
timeters..
timeters..
timeters.,
timeters..
timeters..
timeters.,
timeters..
timeters..
timeters..
timeters.,
timeters..
timeters..

All sizes..

Number and percent in age group —

13 (100.0)
62 (89.9)
13 (16.0)

7 (10. 1)
68 (S4.0)
50 (96.2)
11 (31.4)

2 (3.8)

24 (68.6)

49 (100.0)

32 (97.0)

12 (63.2)

1 (3.0)
7 (36.8)

19 (90.5)

20 (87.0)
10 (40.0)

4 (17.4)

2 (9.5)

3 (13.0)

15 (60.0)

16 (69.6)
5 (83.3)
1 (12.6)

42

2 (8.7)
(0.0)
5 (62.5)

1 (4.3)

1 (16.7)

2 (25.0)
1 (50.0)

1 (50.0)
1 (100.0)

9 and over

2 (100.0)

ToUl
number,
all ages

13

69

81

52

35

49

33

19

21

23

25

23

6

8

2

1

2

462

1 See text footnote 1 .

centimetei-s caught on Georges Bank, 378 (92.1
percent) were estimated to be 2-year-olds and 32
(7.9 percent) to be 3-year-oIds.

The total numbers of haddock caught of each
size and age, shown in tables 4 and 5, were trans-
formed into percentages and plotted in figure 4.
In effect, this amounted to converting the per-
centage size compositions shown in figure 2 into
percentage age compositions. From figure 4, it
can be seen that, as already suspected from figure
2, the modes are composed largely- of fish of
different ages.

It can be seen from figure 3 and also from table
6 that for each age the fish caught on Georges
Bank were considerably larger than those caught
on Browns Bank. One-year-olds from Georges
averaged 22.7 centimeters as compared with only
17.9 centimeters from Browns; 2-year-olds from
Georges were 36.6 centimeters as compared with
22.4 from Browns; 3-year-olds were 43.2 centime-
ters as compared with 30.6; 4-year-olds were 49.4
centimeters as compared with 41.1 centimeters.
Also shown in table 6 are the ranges of the means,
expressed as the mean + 2 times its standard

T.\BLE 4. — Estimated age distribution of haddock catch from
Georges Bank

Length in 3-centl-
meter groups '

Number In age group—

Tnial

1

2

3

4

5

6

7

8

9 and
over

all
ages

511
2.973
3.180

734
35

511

2.973

24 cenllmeters

3, 180

27 ccniimeters

734

30 centimeters

40
182

378

2,55

91

5

75

182

30 centimeters

32
121
202
186
90
24

410

376

42 ccniimeters

J

48
.59
83
31

7

298

45 centimeters

239

10
10

6
7
2

1.59

51 centimeters

117

3
2

I
3

1

40

....

2

18

3

63 centimeters

3

60 centimeters . _

1

69 centimeters

1

1

2

Allsiies

7,433

951

655

233

35

10

3

1

9.321

Table 5. — Estimated age distribution of haddock catch from
Browns Bank

Lenpth in 3-centi-
meter groups '

Number In age group—

ToUl,

1

2

3

4

5

6

7

8

9 and
over

all
ages

15 cenllmeters

29
144
21

29

18 centimeters

16
108
95
16

160

129

24 centimeters

4
36
81
40
20

99

52

30 centimeters

81

33 centimeters

1

12
42
46
17

8

41

32

3ti centimeters

S

7

25

32

10

1

47

53

45 centimeters

42

4

6

2
2
3
2

46

12

54 centimeters

10

2
4

......

4

fiO centimeters

4

63 centimeters

1

All sizes

194

215

181

126

80

10

9

6

1

842

' See text footnote 1.

' See text footnote 1.

182

FISHERY BULLETIN OF THE FISH AAD WILDLIFE SERVICE

GEORGES
BANK

YEAR

2 YEARS

i^^^k

3 YEARS

4 YEARS

FiaoRE 3a. — Impressions of scales of 1-, 2-, 3-, and 4-year old haddock from Georges Bank.

HADDOCK FROM GEORGES AND BROWNS BANKS

183

BROWNS
BANK

I YEAR

2 YEARS

3 YEARS

4 YEARS

Fir.uRE 3b. — Impressions of scales of 1-, 2-, 3-, and 4-year-old haddock from Browns Bank.

184

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

20-

10

BROWNS BANK

/ V \ A
.s:;^^ ^::frws- :::» - — -^-^ "' --° '°

1 30
cr

UJ
Q.

20

10

GEORGES BANK

.^-O'

?.^-- — --° ~6--'sr.m-?—-- — t.

25 30 35 40 45 50

LENGTH IN CENTIMETERS

Figure 4. — Percentage age compositions of haddock catches from Georges and Browns Banks.

55

error. The variation within the age groups was
such that if sampHng continued, about 95 percent
of the mean lengths obtained might be expected
to fall within the limits indicated.

The differences in average length between the
Georges and Browns Banks fish for each age were
found to be highly significant.^ The F-test (pro-
duced by the analysis of variance of the lengths
in tables 2 and 3) showed values far in excess of
the 1 percent level. The probability is much less
than 1 in 100 that such a large difference in the
average length at each age would be due to chance
sampling of a homogeneous population of fish. If
average lengths are plotted against age for the
Browns Bank data, it is seen that the curve is not
as smooth as that for the Georges Bank data and
that two points (2- and 3-year-olds) seem par-
ticularly at variance with (below) what we might
expect in a "normal" growth curve. We believe
this is due to the fact that, in general, there is

^ .\ges 1 to .'» only. No tests of slcntflcance wpre con'puted for older ages.

variability in growth rate between different year
classes and one cannot expect to obtain a smooth
or "normal" growth curve from a single year's
collection of data. Specifically, we contend that
the 1946 and 1947 year classes on Browns Bank
were subnormal in attained size.

Table 6. — Mean length and length range of various ages
of haddock from Georges and Browns Banks

[.\verages computed from tables 4 and 5: standard errors from tables 2
and 3. Figures In parentheses show number of fish for which ages were

read.)

Georges Bank

Browns Bank

Age

Mean
length

Length
range '

Mean
length

Length
range '

22.7 (105)

36.6 (352)

43.2 (251)

49.4 (92)

62.4 (14)

69.1 (6)

(0)

62.0 (2)

72.0 (1)

22. 2 to 23. 2
3ft. 3 to 36. 9
42. 7 to 43. 7
48. 7 to 50. 1
60. 2 to 64. 6

17.9 (88)
22.4 (136)
30.6 (119)
41.1 (61)
46.4 (42)

61.6 (7)

52.7 (5)
.59.0 (2)
63.0 (2)

17. 6 to 18. 2

2 years .

22. to 22. 8

30. 1 to 31.1

4 years -

40. 2 to 42.

45. 4 to 47. 4

6 years

9 years and over

1 Mean±2 times Its standard error.

HADDOCK FROM GEORGES AND BROWNS BANKS

185

After this report was begun, the Albatross III
completed its 1950 summer census on Browns
Bank and there became available a means of
testing this hypothesis: If true, the 3- and 4-
year-ohls taken in 1950, rather than the 2- and
3-year-olds in 1949, might be found to be smaller
than expected. To investigate this, we com-
l)uted the average size at each age of all haddock
from which scales were taken on Browns Bank
in 1950. These average lengths in centimeters
are as follows:

Areraee Number

Imfflh included

1-year-olds 19.3 43

2- year-olds 26. 3 141

3-year-olds 31.5 122

4-year-olds 38. 5 1 64

5-year-olds 48. 1 80

6-year-olds 51.4 162

7-year-olds 55. 1 117

If these values are plotted it can be seen that
the points for 3- and 4-year-olds do fall below
the general trend. Thus it appears that the 1946
and 1947 year classes actually had smaller at-
tained sizes, and this appears to be a reasonable
explanation for not obtaining a smooth growth
curve from the 1949 collection of data on Browns
Bank.

A completely chance sampling of a homogeneous
population in nature is difficult to obtain, but we
believe that our sampling was sufficiently repre-
sentative to confirm the differences described here.
Fii-st, the haddock were caught over several
hundred square miles of Georges Bank and over
about 100 square miles of Browns Bank. Such
large areas were not covered thoroughly, of course,
but the net was set at random within them. Sec-
ond, the same otter-trawl net was used on the two
banks and it should have sampled similarly the
same-size fish on the two banks and unquestionably
should have made no selection of different ages
at the same size. Third, from extensive (un-
published) studies of the catch of the commercial
fleet on Georges Bank we know that haddock
from different parts of Georges Bank grow at
rather similar rates. The other possible objection
to the tests of significance concerns the "normal-
ity" of the size distributions for various ages.

Inspection of figure ^indicates that all curves are
close to normal except the flat-topped one for 2-
year-old haddock from Browns Bank; even this
one instance of kurtosis should have little effect
on the tests of significance.

SUMMARY

The haddock on Georges anri Browns Banks
grow at different rates. One-year-old haddock
averaged 22.7 centimeters on Georges Bank as
compared with 17.9 centimeters on Browns; 2-
year-olds averaged 36.6 on Georges, 22.4 on
Browns; 3-year-olds were 43.2 on Georges, 30.6
on Browns; 4-year-olds were 49.4, and 41.1; and
5-year-olds were 52.4, and 46.4. This difference
indicates that hereditary or ecological condi-
tions governing growth are different in the two
areas and that important intermigrations of the
bottom-dwelling stages of haddock do not occur.
As a consequence, we need not expect the stocks
to fluctuate simultaneously and we should con-
tinue to collect and to analyze separately for the
two areas the statistics of landings, age, growth,
abundance, and other biological data.

LITERATURE CITED

Herrinoton, William C.

1944. Factors controlling population size. Trans. Ninth
Am. Wildlife Conf., pp. 250-263.
Needler, a. W. H.

1930. The migrations of haddock and the interrelation-
ships of haddock populations in North American
waters. Cont. Can. Biol, and Fish., N. S., vol. 6,
No. 10, pp. 241-314.

ROUNSEFELL, GeORGE A.

1942. Field experiments in selecting the most efficient
tag for use in haddock studies. Trans. Amer. Fish
Soc, vol. 71, pp. 228-235.

SCHROEDER, WlLLI.^M C.

1942. Results of haddock tagging in the Gulf of Maine
from 1923 to 1932. Ssars Foundation: Journal
Marine Research, vol. 5, No. 1, pp. 1-19.
Vl.\dykov, Vadim D.

1935. Haddock races along the North American Coast.
Biol. Bd. Can. Prog. Report, No. 14, pp. 3-7.
Walford, Lionel A.

1938. Effect of currents on distribution and survival of
the eggs and larvae of the haddock (Melanogrammus
aeglefinus) on Georges Bank. U. S. Bureau of Fisher-
ies Bull. 29, 73 pp.

U. S. GOVERNMENT PfilKTING OFFICE O — 1952

UNITED STATES DEPARTMENT OF THE INTERIOR, Oscar L. Chapman, Secretary
FISH AND WILDLIFE SERVICE, Albert M. Day, Director

A UNIQUE BACTERIUM PATHOGENIC FOR
WARM-BLOODED AND COLD-BLOODED

ANIMALS

By Philip J. Griffin and Stanislas F. Snieszko

FISHERY BULLETIN G8

From Fishery Bulletin of the Fish and Wildlife Service

VOLUME 52

UNITED STATES GOVERNMENT PRINTING OFFICE • WASHINGTON : 1951

For sale by the Superintendent of Documents, U. S. Government Printing Office
Washington 25, D. C. Price 10 cents

CONTENTS

Page

Description 187

Pathogenicity 188

Discussion ; 189

Summary 189

Literature cited 190

II

A UNIQUE BACTERIUM PATHOGENIC FOR WARM-BLOODED
AND COLD-BLOODED ANIMALS

By PHILIP J. GRIFFIN' and STANISLAS F. SNIESXKO,'' Bacteriolosists

The vast majority of bacterial fish diseases are
caused by motile or noimaotile Gram-negative
bacteria. Some of these, such as Bacterium sal-
monicida, have stable characteristics and represent
bacterial species with well-defined properties.
There are, however, many inadequately described
motile Gram-negative bacteria which have been
isolated from diseased warm- and cold-water
fishes, amphibians, and reptiles from all over the
world. Many of these bacteria belong to the genus
Pseudomonas. Some bacteria, pathogenic to am-
phibians and reptiles (Hinshaw and McNeil 1946,
1946a, 1947), have been recently described and
classified as paracolons.

The microorganism described in this report has
a peculiar taxonomic position, because some of
its characteristics indicate that it should be classi-
fied as a pseudomonad, while its physiological
and antigenic properties suggest relationship with
the paracolons.

Paracolon organisms isolated from outbreaks of
gastrointestinal diseases in man have been de-
scribed as a group of aberrant coliform organisms
comprising a distinct biological group (Stuart et
al. 1943). Borman, Stuart, and Wheeler (1944)
referred coliform-like bacteria that slowly fer-
mented lactose to a separate genus, Paracolobac-
trum. Those organisms which produced acetyl-
methylcarbinol were termed Paracolobadrum aero-
genoides.

This report is believed to be the first description
of organisms conforming largely to the description
of Paracolobadrum aerogenoides and pathogenic for
fish. Microorganisms were isolated from the body
cavities of four aquarium fish belonging to several
species (Corydoras aeneus, Xiphophorus hellerii,
Platypoecilus maculatus, Lebistes reticulatus) all
of which had died suddenly within a period of a

' Department of Microbiology, Yale University, New Haven, Conn.
» Microbiological Laboratory, U. S. Fish and Wildlife Service, Kearaeys-
vlUe, W. Va.

956468°— 61

week. One strain (1) was obtained from a living,
infected Corydoras aeneus.

We are indebted to Dr. E. K. Borman, Bureau
of Laboratories, Connecticut State Department
of Health, Hartford, for preliminary antigenic
typing and for his advice and comments, and to
Dr. S. H. Hutner, Haskins Laboratories, New
York, and to Dr. R. W. Hinshaw, Camp Detrick,
Md., for advice and reading of the manuscript.

DESCRIPTION

In all cases observed, lesions developed on one
side of the body as small areas of greenish discol-
oration just under the skin between the pectoral
and ventral fins. Upon incision, a fetid and
purulent material was exuded. A Gram stain of
the discharge revealed numerous Gram-negative
rods, 1.3 to 2 microns long and 0.7 micron ^v^de,
with romided ends, and exhibiting bipolar staining.

In broth and on agar, the bacteria were arranged
singly, in pairs, and occasionally in filaments.
The rods were encapsulated, as determined by
Anthony's method, and did not form endospores.
Active motOity was observed and single polar
flagella were demonstrated by Novel's method
(1939). The organisms were facultatively an-
aerobic but grew best with unrestricted access to
air. In nutrient broth, the optimum growth
temperature was 37° C, the ma.ximum 43° C,
and the minimum 5° C. The pH range for growth
was from 5.0 to 9.5 with the optimum range be-
tween 6.5 and 7.5; best growth occurred at pH 7.
Cultures maintained for almost 8 months in the
refrigerator stUl contained viable organisms.

On nutrient agar, colonies averaged 2 mm. in
diameter in 24 hours. They were circular, smooth,
entire, slightly convex, and opaque. On blood
agar, strains 1 and 2 exhibited a beta hemolytic
zone averaging 7 mm. in diameter in 24 hours.
After 48 hours the colonics were surrounded by a
16-mm. hemolytic zone with a greenish-bro\vn

187

188

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

discoloration. Strain 3 was nonhemolytic. Blood-
agar and nutrient-agar cultures had a strong odor
similar to that detected in the incised lesion from
the infected fish. Colonies on eosin-methylene-
blue and MacConkey's agars appeared glistening
and colorless. On agar slants, growth was abun-
dant, filiform, glistening, butyrous, and colorless.
The appearance of the mediimi remained un-
changed. In nutrient broth a pellicle was
formed; there was dense clouding and a scant
flocculent sediment. A loopful of a 48-hour broth
cultm-e inoculated into nutrient broth resulted
in visible growth in 4 hom-s at 37° C.

At 20° C, growth in gelatin was best at the
top, with subsequent stratiform liquefaction. At
37° C, liquefaction was complete in 24 hours.
Nitrates were rapidly reduced to nitrites. The
methyl-red test was negative. Acetylmethylcar-
binol and indole were produced by strains 1 and 2.
Strain 3 produced acetylmethylcarbinol but failed
to form indole. Growth occiu-red on Simmon's
citrate agar. In Koser's citrate broth, strain 1
was negative, strains 2 and 3 positive, after 3
days. Hydrolysis of cornstarch was complete in
24 hours (no color with iodine). Digestion of
egg albumin and Loeffler's serum slants began in
48 hom-s and was practically complete in 96 hom-s.
H2S was not produced in Pb acetate medium or in
Kligler's iron agar. The m-ease test was negative.
There was slight acid production (pH 6) with the
formation of a small amomit of precipitate in
bromo.cresol-pm'ple milk. Peptonization was evi-
dent in 48 hours and practically completed in 120
hours. Litmus milk was reduced in 24 hours.

Various sugars, alcohols, and glucosides were
sterilized by filtration through a porcelain filter
and incorporated into standard basal medium in
1-percent concentrations. On original isolation,
strains 1 and 2 produced acid in lactose after 21
days, and culture 3 after 27 days. This conforms
to the behavior of the paracolon type of micro-
organisms which are described as slow lactose
fermenters in Bergey's Manual (Breed, Mm-ray,
and Hitchens, 1948). After several serial transfers
in lactose broth, the time of acid formation in
lactose was reduced by 6 to 11 days, depending on
the strain. Readings made during a 4-week period
showed that acid and gas were produced in 24

hours at 25° C. and at 37° C. in L-arabinose
(weak), glucose, D-fructose, D-mannose, sucrose,
maltose, trehalose, soluble starch, dextrin, glyco-
gen, and mannitol. A faint acid reaction and
trace of gas appeared in salicin after 4 to 6 days'
incubation at 37° C. At 25° C, salicin was fer-
mented by all 3 strains in 24 hom-s. Strain 3
differed from strains 1 and 2 in that it produced
acid and gas in raffinose but not in sucrose at
either temperature. No acid or gas was'produced
in D-xylose, L-rhamnose, cellobiose, mellibiose,
melizitose, inulin, glycerol, erythritol, adonitol,
dulcitol, D-sorbitol, inositol, and esculin, at 25°
C. or 37° C.

Preliminary antigenic analysis indicated that
strains 1 and 2 were antigenically diverse from any
of the paracolon types described by Stuart et al.
(1943). Strain 1 proved to possess somatic com-
ponents XXX and XL of the Salmonella group,
while all tests with flagellar antisera were negative.
Strain 2 was rough and consequently could not
be typed. Strain 3 was negative for somatic
components I to XXXVIII and for all flagellar
antigens.

PATHOGENICITY

Nine goldfish {Carassius auratus) and 27 adult
white mice were inoculated intraperitoneally with
0.2 ml. of 24-hour broth cultures of the 3 strains,
and in 19 hoiu-s all were dead. In every instance,
the organisms were reisolated in almost pure cul-
ture from the fluid present in the body cavity.
Similar tests were made with 0.2-ml. suspensions
of heat-killed bacteria and filtrates from the same
24-hom- nutrient broth cultures. All fish and mice
proved refractory. Strain 3 also proved to be
pathogenic for guinea pigs.

Further experiments were carried out at the
Microbiological Laboratory, Kearneysville, W.
Va., in which 60 fingcrling trout were used. Ten
trout of each of the following species were inocu-
lated intraperitoneally with 0.2 ml. of a 24-hour
broth culture: Rainbow trout {Salmo gairdnerii),
eastern brook trout (Salvclinus jontinalis), and
brown trout {Salmo trutta). As controls, 10 fish
of each of these species were inoculated with
sterile broth. The temperature of the water in the
troughs was approximately 14° C. Some deaths

BACTERIUM PATHOGENIC FOR WARM-BLOODED AND COLD-BLOODED ANIMALS

189

occurred within 24 hours after inoculation, and in
less than 41 hours eight of the rainbow and all
the brook trout were dead. All controls of these
two species lived. Results of the brown-trout
inoculations were not ?s striking as those of the
other two species. In 48 hours sLx of the brown
trout had died, but three of the contiol fish also
were dead. There were no further deaths in
either group.

Gross pathological changes were observed in
inoculated yearling trout of the three species.
Inoculations were performed, as previously indi-
cated, using strain 1. Dead and living fish were
examined. Macroscopically, the artificially in-
fected trout did not show any external lesions
other than slight swelling and congestion in the
anal region. The most important and character-
istic internal pathological changes noted were as
follows: Intestine filled with a yellow or white
gelatinous mucus, particularlj' in the posterior
portion; blood vessels congested and intestinal
wall swoUen; liver redder in color than in the
controls, and spleen enlarged and much darker.
There was some exudate in the peritoneal cavity
and occasiozially the peritoneum in the posterior
portion of the abdominal cavity was congested.

DISCUSSION

Biochemically, the organisms described in this
paper are very similar to Paracolobactrum aero-
genoides; but the possession of a single polar
flagellum would place the bacteria in the genus
Pseudomonas. It is interesting to note that cul-
tures 1 and 2 differed from classical description
of members of the Paracolobactrum group in that
they formed indole and acetylmethylcarbinol.
The production of both substances is not a com-
mon occurrence within this genus. Though the
slow fermentation of lactose, its pathogenicity,
and presence of some Salmonella somatic antigens
suggests relationship to paracolons, the possession
of a single polar flagellum would, according to
the present taxonomic concepts, relate these or-
ganisms to the genus Pseudomonas.

Paracolon types have been described in warm-
blooded and cold-blooded animals. Edwards,

Cherry, and Bruner (1943) reported isolating a
paracolon type from the liver of a rattlesnake.
Hinshaw and McNeil (1946a) reported the isolation
of paracolon types that caused heavy mortality in
turkey poults. The same authors (1946b) isolated
related paracolon types from the livers of rattle-
snakes, suggesting a relationship between the
types isolated from snakes and those causing in-
fection in turkeys. Hinshaw and McNeil (1947)
reported the isolation of two sucrose-fermenting
paracolon types possessing antigenic components
of the Salmonella group from Pacific fence lizards
and of paracolons from gopher snakes and sick
turkey poults.

Members of the genus Pseudomonas have been
isolated repeatedly in outbreaks of disease of
fishes and other cold-blooded animals (Schaeper-
claus 1941, Guthrie 1942). The relative fre-
quency of isolations of these groups of bacteria
from other cold-blooded animals, and the isola-
tions described in this paper, call attention to
the possibility that fish ma}- be carriers of these
microorganisms. It is also possible that the con-
verse is true, that fish acquire infection from organ-
ismscarried byhigheranimals. The fact that these
organisms have been shown experimentally to be
pathogenic for both cold-blooded and warm-
blooded animals places them in a unique position
and leads one to speculate on the role played by
fish with respect to infection in man.

SUMMARY

The isolation and description of a unique
bacterium pathogenic for warm-blooded and cold-
blooded animals is discussed.

The ntiicroorganism described in this report has
a peculiar taxonomic position in that its single
polar flagellum is a characteristic of the genus
Pseudomonas, whereas relationship to the para-
colons is suggested biochemicaUy by its phj^sical
and antigenic properties. Paracolon organisms
producing acetymethylcarbinol and classified as
Paracolobactrum aerogenoides have been isolated
from the gastrointestinal tract of man diu'ing
epidemics, but this is believed to be the first
description of an organism similar to P. aerogen-
aides pathogenic for fish.

190

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

LITERATURE CITED

BoRMAN, E. K., C. A. Stuart, and K. M. Wheeler.
1944. Taxonomy of the family Enterobacteriaceae.
Jour. Bact., vol. 48, pp. 351-367.
Breed, R. S., E. G. D. Murray, and A. P. Kitchens.
1948. Bergey's manual of deterniinative bacteriology,
6th ed. Williams & Wilkins Co., Baltimore, Md.
Edwards, P. R., W. R. Cherry, and D. W. Bruner.
1943. Further studies on coliform bacteria seriologieally
related to the genus Salmonella. Jour. Infectious
Diseases, vol. 73, pp. 229-238.
Guthrie, R.

1942. Studies of microorganisms classified as Proteus
hydrophilus. M. S. Thesis, University of Maine,
Orono, Maine.
HiNSHAw, W. R., and E. McNeil.

1946a. The occurrence of type 10 paracolon in turkeys.
Jour. Bact., vol. 51, pp. 281-286.

1946b. Paracolon type 10 from captive rattlesnakes.

Jour. Bact., vol. 51, pp. 397-398.
1947. Lizards as carriers of Salmonella and paracolon

bacteria. Jour. Bact., vol. 53, pp. 715-718.
Novel, E.

1939. Une technique facile et rapide de mise en Evidence

des oils bact^riens. Ann. Inst. Pasteur, vol. 63, pp.

302-311.

SCHAEPERCLAUS, W.

1941. Fischkrankheiten. 2d edition. Gustav Wenzel

& Sohn, Braunschweig, Germany.
Stuart, C. A., K. M. Wheeler, R. Rustigian, and A.

Zimmerman.
1943. Biochemical and antigenic relationships of the

paracolon bacteria. Jour. Bact., vol. 45, pp. 101-119.

o

UNITED STATES DEPARTMENT OF THE INTERIOR, Oscar L. Chapman, Secretary
FISH AND WILDLIFE SERVICE, Albert M.Day, Director

ESTIMATION OF SIZE OF ANIMAL

POPULATIONS BY MARKING

EXPERIMENTS

By Milner B. Schaefer

FISHERY BULLETIN 69

From Fishery Bulletin of the Fish and Wildlife Service

VOLUME 52

UNITED STATES GOVERNMENT PRINTING OFFICE . WASHINGTON : 1951

For sale by the Superintendent of Documents, U. S. Government Printing Office
Washington 25, D. C. - Price 15 cents

CONTENTS

Page

Simple case 191

The problem 191

Some applications in the literature . 192

Some further considerations 195

Repeated sampling of a constant population 196

Estimation of a changing population 199

Literature cited 203

ESTIMATION OF SIZE OF ANIMAL POPULATIONS
BY MARKING EXPERIMENTS

By MILNER B. SCHAEFER, Fishery Research Biologist

Determination of population numbers is basic
to studies of changes in populations of animals
and of the causes of the changes, such as the
effects of fishing on a population of fishes. For
many animals this cannot be accomplished by
direct enumeration, and recourse must be had to
indirect methods. One technique which has
been employed in the study of fishes, and other
organisms as well, and wliich is still in course of
development, is the use of marked members to
estimate population numbers.

SIMPLE CASE
THE PROBLEM

The simplest case vnth which we have to deal,
and which can be applied to many fish populations,
is where we have a population containing A''
members (unknown) which is known to contain T
marked members and U=N—T unmarked, and
where we have drawTi a single representative
sample of n members containing t marked and
u = n—t umnarked. The term "representative" is
used here to mean that the character estimated
from the saniple will have a mean value in repeated
samples equal to the population value. This cor-
responds with the commonly accepted sense of the
term, and also with its usage by Neyman (19.34).
A simple random sample of the population is repre-
sentative, but so also may be various others.

The problem of estimating N consists in making
such an estimate given T and the sample values
/), t, and u. The usual basis of procedure is to

accept 7p=-r intuitively and to estimate A^^by the

equation

N--

nT

(1)

If, for example, we know there are 100 marked
members in the population, and a samph? of 500

contains 50 marked members, we would estimate
the population by this equation to be

N--

500X100
50

1,000

968620°— 51

This method has been employed by a consider-
able number of mvostigators during the last two
decades to estimate the populations of various or-
ganisms. The method is much older than this,
however, having been employed as early as 178.3
by the famous French mathematician and scientist
Laplace in estunating the human population of
France. Laplace gave considerable attention to
the theoretical problem of the error involved in
employing tliis method. This problem attracted
the attention of another famous statistician.
Karl Pearson, who published an analysis of it in
1928. Later workers in various branches of
zoology seem to have overlooked Pearson's work
and also that of their zoological contemporaries.
They have apparently often "rediscovered" the
same method, but have in the main given little or
no attention to the problem of the accuracy of the
resulting estimate.

Laplace determined from a sample the ratio of

births in a year to the population producing those

births, and then ascertained the number of births

in a year in each urban and rural district of

France; by multiplying the number of births by

th{> ratio of pojiulation to births determined from

the sample, he arrived at an estunate of the total

population. Laplace was led to consider also the

error inherent in his estunate. This problem, as

restated by Pearson (1928), but using my notation,

is as follows: "A population of unknown size A^is

known to contain T affected or marked niembei-s.

It is desired to ascertain — on the hypothesis of

inverse probabilities — a measure of the error

T
introduced by estimating N to ha n —> where t is

191

192

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

the number of marked individuals in a sample of
size 71." Laplace treated this problem as an urn
problem, with an infinite number of black and
white balls representing marked and umnarked
members. On the basis of an extension of Bayes'
theorem, he predicted from a first sample of t
and n observed what a second sample with known
T but unknown A^^ might produce. He found
that the mean value of N would be equal to

—7- if T, n, and / are all large. He also took the

Tn
distribution of A'^ to be normal about — as mean

with standard deviation estimated by

where t, u, and T are all large, Laplace's case,

Cn

Tu{T+t){t+u)

(2)

where the numbers are all large.

For the preceding example, where T=]00,
71 = 500, and t=50, Laplace's solution would give
an estimate of standard deviation

/I

00X450X1 50 X500 Y^^g^

50*

Pearson reexamined this problem in his 1928
paper because he felt Laplace's urn statement did
not fit the actual problem since "We are not
taking a second sample from an infinite population.
We have only one sample and we want to learn
something about the population from which it
has been sampled, which is finite in extent,
although its extent is unknown. We do know,
however, that it contains T white balls; i. e.,
births in all France."

Assuming the sample ti to be a random sample
of the finite population A'^, and on the basis of
inverse probabilities (Bayes' theorem), Pearson
finds that the modal value of the distribution of
the possible values of A'^ is

N=u + T-

u{T-t)_nT

t

the mean value is

A^=ii+T-
and the variance is

{t-2)

On

2

(•u+l)(r-<+l) (n- 1) (T-1)

{t-2y {t-2.)

(3)

(4)

(5)

Ar=7V=f

and

"N

TuiT-t)(t+u)
t^

(6)

(7)

This estimate of o-^^ is different from and smaller
than that of Laplace, the disagreement being
attributed by Pearson to Laplace's taking his
sampled population as if it were a second sample
independent of that already taken.

For the example employed before, with r=100,
71=500, <=50, formula 7 would give

an

<'

00X450X50X500X1

50'

=9;

Pearson's paper seems to have been generally
overlooked by zoologists dealing with similar
problems.

SOME APPLICATIONS IN THE LITERATURE

Formula 1 has been applied to the estimation of
diverse aniinal populations. One of the best
known of these applications is the so-called Lincoln
index of the duck population of North America de-
veloped by Lincoln (1930), and mentioned in the
textbook of Leopold (1935), the monograph of
Kendeigh (1944), the manual of Wright (1939),
and elsewhere. Lincoln used the ducks banded at
stations in North America as his marked members,
and the kill by hunters as his sample of the popula-
tion. The inaccm-acies of kill records and the in-
complete return of bands were recognized as
sources of errors. No attempt was made to esti-
mate the statistical error.

An application of tliis method was made by Vor-
hies and Taylor (1933). These workers computed
the number of jack rabbits on fenced cattle ranges
of Arizona by taking the ratio of jack rabbits seen
to the number of cattle seen in a strip of width
equal to the apparent flushing distance of the
jack rabbits, and comparing this ratio with the
known number of cattle on the range. In this
case, the cattle would represent the "marked"
members of the population of rabbits plus cattle.
It seems rather doubtful whether the ratio in the
sample would be a fair estimate of the ratio in
the population because of the obviously different

SIZE OF ANIMAL POPULATIONS

193

visibility of cows and rabbits, even in a narrow
strip.

Jackson (19:^3) developed a method of comput-
ing the population of tsetse flies in a closed area
by marking flies with colored paint and taking a
sample to determine the ratio of marked to un-
marked. In a later paper (1936) Jackson states
that he discovered this method independently in
1930, but meanwhile became cognizant of Lin-
coln's work and hastens to credit Lincoln with the
method.

Jackson mentioned, also, that a representative
sample of the population as regards mark ratios
would be obtained if either the marking or the
subsequent sampling were carried out in a non-
selective fashion. This is of considerable prac-
tical importance. It is not necessary that both
be nonselective. If the marks are randomly, or
evenly, distributed in the population, any sample of
n members will yield a consistent estimate of the
mark ratio in the population. (The term "mark
ratio" or "tag ratio" will be used in this paper to
mean the quotient of the number of marked mem-
bers in a group divided by the total members in
the group.) Similarly, a representative sample of
the population will yield a consistent estimate of
the mark ratio regardless of the distribution of
marked members in the population.

Sato (1938) estimated the stock of red salmon
in the western North Pacific. He stated:

2. The stock (S) of red salmon may be estimated by the
formula:

Y:X = S:Z,

where Y is the number of tagged fishes, X, the number of
recaptured fishes, and Z, the total catch of the fish.

His estimate of 94.7X10^ individuals in 1936
was made from 1,358 marked fish and 177 re-
captures among a sample of 12,339X10^ He
made no attempt to estiniate the reliability of the
result. It may be seen from formula 7, however,
that the sampling error is actually quite large.

Green and Evans (1940) employed this method
for computing populations of snowshoe hares.
Hares were trapped and banded during a long
"prccensus period" lasting all winter and up to
mid -April. The banded hares at Uberty from
these operations were taken as the kno\vn niunber
of marked members, and the ratio of marked to
unmarked was determined during a short "census
period" in April. The formula employed by

these authors is essentially formula 1, since they

take

Hares banded in precensvis period
Other hares present in precensus period

_ New-banded hares trapp>ed in census period ,„.
Other hares trapped in census period ^ '

and compute the number of "other (unmarked)
hares present in precensus period," and add it to
the number of marked hares to get the total
population. This may be illustrated by the
suuple example we have employed before, where
we have a population containing 100 marked
members and draw a sample of 500 containing
50 marked members. Green and Evans would
compute "other hares present in precensus period,"
as follows:

100_ 50
X ~450

X=900

and add the 100 marked hares to get the population
estimate of 1,000.

These authors consider the effects of several
possible sources of error. They show that migra-
tion in and out of the area of study is unimportant.
The "evenness" of the sampling Ls also considered.
They state that "It is essential that trapping
throughout the area be uniform during the census
retrap in the spring. . . . LTniformity need not
be so rigidly maintained during the precensus
period." This, of course, is a special case of the
rule that either the sampling for tagging must be
uniform or the subsequent sanapling for tag ratio
must be such as to \aeld a representative sample
of the whole population.

Green and Evans also consider the "error of
random sanapling." Using their notation, wc
find that they take:

p= proportion of hares trapped in census period that were
not banded (trapped) in precensus period.

P = number of the hares trapped in census period that were
not trapped (banded) in precensus period.

.V= total number of hares trapped in the census period.
P

They then take ffp for the standard deviation
of p and state that

■V

pq

N

(9)

where q=l—p- Taking P±2<jpN, and emplojnng
these values in place of the second quotient

194

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

in their formula (8), they arrive at an estimate of
range of the error due to sampling. They conclude
that —

If we use 2(T„ as our range on either side of the figure
obtained ... we are almost certain to include the correct
figure for p, since twice the standard deviation on either
side of the mean includes 95 percent of a normal distribu-
tion curve.

"While this estimate of the reliability of the
population estimate is better than none and,
indeed, will give an idea of limits mthin which
the population may be expected to fall, it suffers
from a lack of precision. The method of compu-
tation may be illustrated by the simple numerical
example we have employed before. Here P=450,
A^=500, and p = 0.90. Formula 9 then yields

ffp=y-

9X.1

500

.01342

and 2o-pA^= 13.42. The corresponding values of
463.4 and 436.6 may be employed in the second
quotient of formula 8 in place of 450 for P to
obtain estimates of 927 and 873 for limits of the
estimate of "other hares present in precensus
period." Corresponding values of total population
arc 1,027 and 973.

Formula 9 gives the standard deviation of 2' in
repeated samples of size N from a population of
infinite size. Since in the present case the popula-
tion is finite, and A'^is large with respect to it, the
formula for the standard deviation of p should be

,_P-Np.q

"""F-l N

where P=the number in the population (Cramer
1946, p. 516; Kendell 1944, p. 203). Thus Green
and Evans' limits for p would tend to be too broad.
For the same simple example used above, this
formula gives us

(1000-500) 0.9X0.1

= .0000901

" (1000-1) 500

ap = . 00949

Green and Evans' estimate also has, however,
the same objection that Pearson raised to Laplace's
solution, rather important in this instance, that
this treats the problem of a further sample from a
population in which the value of p is known.

which is not the same thing as determining the
error of the estimate of the population from the
single sample available.

Dice (1941) refers to the paper by Green and
Evans and considers a number of practical factors
to be taken into account in carrying out the
sampling.

Knut Dahl (1943, pp. 139-143), has applied the
method of marked members to enumeration of
trout in a lake. In a small lake on the west coast of
Norway, of 250,000 square meters, trout were
captured by beach seine and marked. During a
second fishing 8 to 14 days later he determined the
number of marked and unmarked fish captured.
From the number of marked fish liberated, divided
by the number of marked fish recaptured, he com-
puted a "Gjenfangstkvotient" by which the total
fish taken in the second fishing was multiplied to
obtain the total population. This is, of course,

T .
the same a» formula 1, where y is the "Gjenfangst-
kvotient."

Rieker (1942) mentions the simple case here con-
sidered, although he uses a method of repeated
tagging and sampling on the stationary pojmla-
tions of pond fishes dealt with in his paper. This
method will be reviewed subsequently.

In a later paper, Rieker (1945a) employs for-
mula 1, which he calls "the Peterson method,"
after the Danish investigator who is said to have
used it on plaice. Ricker's field procedure is
siniilar to that of Green and Evans on hares in
that he used the number of fish marked during a
precensus period and the mark ratio of a later
period. He also writes in regard to the sampling
consideration we have discussed earlier in relation
to Jackson (1936) that:

The principle involved here is that if either the marking
or the search for recaptured fish is made on only a part of a
homogeneous population, the Peterson estimate will still
apply to the whole population. If both marking and
search are made in only a fraction of the population, the
estimate applies to whichever fraction is larger.

Cagle (1946) employed marked lizards to esti-
mate their population on a section of Tinian
Island by the employment of the method formu-
lated in formula 1. He marked 127 individuals by
cUpping their toes and in a sample of 52 found
12 marked, jdelding an estimated population of
roughly 500 individuals. He did not consider the
problem of sampling error.

SIZE OF ANIMAL POPULATIONS

195

SOME FURTHER CONSIDERATIONS
An alternative derivation

Formulae 3 to 7 were reached by Pearson by
means of Bales' theorem, which is objected to as
invalid by many mathematical statisticians (.Ken-
dall 1944, p. 176 et seq.)- Dr. S. Lee Crmnp has
suggested (private communication) that an esti-
mate of A'^ may be arrived at by other moans, as
follows. Drawing samples of fixed size n from a
population A'^ of which Tare marked, the probabil-
ity that, in a sample of n, f are marked is

Pit)-

(N-n)\nm{N-T)\

NW.iT-ty. (n-ty. {N-T-n+t)l

,(10)

whence

in+l)(r+l)

E

(t+

^ytL^|=iv+i-P(0)(iv-r-7i). . .(11)

where E ( ) denotes mathematical expectation and
P (0) is the probability of getting no tags in the
sample.

This means that

(n+DJT+l)
(t+l)

1

(12)

is an estimate of A'^ biased by an amount P (0)
(N—T~n). If conditions arc such that a sample
of n with no marked individuals is very unlikely,
the bias is negligible. We may say that formula 12
is an efi'ectiveh' unbiased estimate of A'^.

^There the numbers are all large, formula 12
reduces immediately to formula 1 or formula 6.

Unfortunately, an estimate of the variance of
the estimate of A'^ given in formula 12 has not yet
been obtained.

Chapman (1948) has considered the problem of
determining the value or values of A'^ which make
P (t), formula 10, a maximum. He found that the

nT
maximum-likelihood estimate of A^ is — > or if that

is fractional, the integer immediately below

nT

t '

Confidence limits on the population estimate

The method of confidence intervals, due to
NejTnan (1934), may be employed to determine
the range of values within which we may expect A'
to lie. A discussion of the theory of confidence

intervals is beyond the scope of this paper, and
reference is made to the original paper of Neyman
or to the discussion of Cranacr (1946, p. 507 et seq.)
or that of Kendall (1946, p. 62 et seq.).

The confidcnco limits of the estimate of the
tag ratio in the population may be obtained as
follows (Cramer 1946, p. 515):

Suppose wc have a population consistinK of a finite
number .V of individuals, .Vp of which pos-sess a certain at-
tribute A, while the remaining Xg = X— Np do not possess
A. It is now required to estimate the unknown proportion
p . . . Let us draw a random sample of n individuals
without replacement, and observe the numljer v of indi-
viduals in the sample possessing the attribute A. In
current text-books on probability, it is shown that we have

Further the variable p*=- is approximately normally dis-
tributed, when n and N—n are large. Taking p* as an
estimate of p, we now assume as above that the error of ap-
proximation in the normal distribution can bo neglected.
The probability that p* lies between the limits pdb

/A[-n pq ig
V A/-1 n

then equal to e, where X has the same

significance as in the preceding example. (Note: where X
was stated to be the lOOe % value of a normal deviate, and
€ is the confidence level.)

In Cramer's notation E ( ) denotes mathe-
matical expectation (or mean value) and D^ ( )
denotes the variance.

A' and n have the same meaning as in our earlier

T
formulae, 1 to 12; p is equal to — > and y is equal to

t in those formulae.

For any given values of A^, n, and T we can cal-
culate the limits within which w* = - mav be ex-

' n

pected to fall for a given confidence level, «, by
the formula

p±X

iN-n pq
\N-1 ' n

(13)

where

T

Given values of n and T from an experiment,
we can, then, by formula 13 calculate for various
values of p, as ordinates, the limits within which
p*, the tag ratio of the sample, as abscissae, may
be expected to fall for a given value of the con-
fidcnco level e. The (turves connecting these
points will form the confidence limits corresponding

196

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

to various values of sample tag ratio ?*="• Since

to every value of p there corresponds a value of A'',
these curves also give the confidence limits of
our estimate of the size of the population made by
the formula

T

(14)

T

V

which is the same as formula 1, of course.

A niunerical example may make this clear.
Suppose that in a given experiment we have
placed 1,000 tagged fish in the population and
plan to draw a sample of 2,000 fish for determinmg
the tag ratio. By formula 13 we can compute for
values of population tag ratio, p, the limits within
which p* will be expected to fall in, say, 95 percent
of the cases (e=0.95). In figure 1, we have
calculated and plotted these limits for part of the
range of p for this example. The ordinates on
this graph are values of p, and the abscissae are
values oi p*. Going horizontally across the graph
for a given value of p we come to the values of p*
withm which samples of 2,000 from a population
having a true tag ratio of p would be expected to
fall in 95 percent of the cases. By the theory
developed by Neyman the loci of such points for
various values of p form the 95-percent confidence
limits for values oi p*. For a given value oi p*
we go along the vertical to the intersections with
these loci to find the confidence limits for that
value of p*. Thus, suppose that we draw our
sample of 2,000 and find that it contains 100
tagged fish. Our estunate of the tag ratio in the
population is 0.05, and from figure 1 we find that
for this value oi p* the 95-percent confidence
lunits are 0.042 and 0.059. Since we know there
are 1,000 tagged fish in the population, our
estimate of the population by formula 14 is 20,000
with 95-percent confidence limits 16,950 and
24,800. On the right-hand edge of the graph we
have plotted the values of A^^ corresponding to
tag-ratio values of the same ordinates on the
left-hand edge, in order to exhibit graphically the
relation between the two.

Such a chart as this may be computed for any
particular experiment . The entire range of values
of p need not be included; it is sufficient in practice
to compute the values to include the region within
which p* \a expected to fall.

For values of n which are small with respect to
N, so that -j^ — T approaches 1, formula 13 ap-
proaches the form appropriate for the binomial.
Clopper and Pearson (1934) have computed and
charted the confidence limits of the binomial for a
large number of values of n for 95 percent and
99 percent confidence levels. Since the limits for
the binomial fall in every case outside the limits
given by formula 13, these charts may be used to
obtain upper and lower limits on the sample value
oi p* even where n is not small in relation to A'^.
This involves, of course, a considerable loss of
efficiency when n is not small in relation to A'', so
that the employment of formula 13 would seem to
be generally preferable in such cases.

Chapman (1948) has considered the Poisson
approximation to the distribution of expected
numbers of tag recoveries where the tag ratio is
low, in addition to the normal, normal-binomial,
and normal-hypergeometric approximations, as
bases for confidence-interval estimates of A^. He
has tabulated useful confidence limits for the
Poisson distribution, and discusses practical cri-
teria for judging which distribution to choose as a

basis of estimation for various values of n and —

n

As is shown by Chapman's example on page 81
of his paper, for experiments involving numbers of
tagged fish, T, and subsequent samples, n, of the
magnitude of the example we have employed, and
which is of the approximate magnitude of most
practical tagging experiments, the differences in
confidence lunits resulting from the several dis-
tributions which might be employed are not very
great. In practice it would make little difference
which we chose. He recommends which distribu-
tion to employ for various situations ; for values of

n> 1,000 and->0.05he recommends the normal

hypergeometric, which has been employed by me
in the example above.

REPEATED SAMPLING OF A CONSTANT
POPULATION

Where the population of an area remains con-
stant over an appreciable period of time, it is
possible to arrive at an estimate based on repeated
sampling and marking.

SIZE OF ANIMAL POPULATIONS

197

In order to estimate the population by this
method, a sampling station or group of stations is
established that will result in a random sample of
all parts of the population. Samples are dra^\^l at
intervals and the fish are tagged and replaced.
Records are kept, for each sample, of the number of
fish caught and the number of recaptures.
Schnabel (1938) provided a solution to the problem
of estimating the population from the resulting
data.

We may let A^be the total population, as before,
Ti be the number of tagged fish in the lake when
the i'" sample is drawn, 7i j be the total number in
the i'* sample, consisting of ti tagged fish recap-
tured and Ui untagged. Schnabel finds that where
k samples are drawn, the method of maximum
likeliliood gives as an estimate of N the positive
real root of the k"' order equations

k

N-Ti

k

-12 ti

which can be expanded in the form

^..T.

m N V~^N^N'^

/ 1=1

(15)

(16)

By taking sufficient terms in formula 16 the root
maj' be approximated as closely as desired.
Schnabel states that 3 terms of the series are
usually sufficient, and that the computations
necessary for higher approximations are often
prohibitive.

Schnabel also considers some sp(>cial cases of
formula 16. By writing the equation (15) in the
form

(17)

it may be seen that if Ti is negligible compared to
AT', the root of formula 15 is approximately

JZniTi

i=l

k

i=l

(18)

This is the formula which has been emploj'ed by
fislieries workers in practice. Its application wall
be clear from the example given in table 1 , the data
for which are from a marking experiment by
Krumholz (1944).

Table 1. — Schnabel's method of computing a fish population
by repeated sampling and marking

[Data from Krumboli (1944) table I]

Num-

Number

Esti-
mated
popula-
tion

Date
(1941)

ber of

fish

exam-

of
marked

flsb in

Product

Sum of
products

Num-
ber of
returns

Sum
of re-
turns

ined

lake

53
65

Ti

niTi

sn.r,

ti

2<i

ZmTilSti

lulv 30

31

53

2,915

2,915

2

2

1,458

Aug, 1

67

106

7,102

10, 017

3

5

2.003

2

59

170

10, 030

20. 047

2

7

2.864

4

85

225

19, 125

39. 172

6

13

3. 013

5

94

297

27, 918

67.090

3

16

4, 193

6

53

376

19.928

87. 018

1

17

5.119

1

115

426

48.990

136.008

5

22

6.182

8

59

520

30,680

166.688

4

26

6.411

9

53

573

30, 371

197. 059

4

30

6.669

11

53

609

32,277

229.336

5

35

6, 5.62

12

68

604

41. 074

270. 410

2

37

7.308

13

45

666

29,970

300. 380

4

41

7,326

14

38

705

26.790

327. 170

41

7,980

15

45

742

33,390

360, 560

3

44

8,196

16

28

742

20.776

381.336

44

8.667

18

40

741

29.640

410. 976

2

46

8.934

19

20

741

14.820

425,796

46

9.256

20

30

741

22,230

448,026

5

51

8.785

21

27

741

20. 007

468,033

1

52

9,001

22

42

741

31, 122

499,155

1

53

9,418

23

20

741

14.820

513. 975

53

9,698

Next Schnabel points out that if Ti= T for all i

N=T

rr^ni

(19)

and states that "This formula is applicable to the
data of experiments in wliich the number tagged
is held constant after a certain point . This method
has the disadvantage that the data taken before
T become constant are not utilized."

It may be readUy seen that if we consider the
sum of the samples in this last case as a single
largo sample, fonuula 19 is identical with formula
1. Thus the simple case considered earlier may
be regarded as a special case of the method of
the present section.

Schnabel's formula 18 has been emploA^ed by
Ricker (1942, 1945a) to estimate fish populations
of lakes and ponds in Indiana. Ricker has as-
sumed that, in situations where this formula is
applicable, the fiducial limits of the Poisson distri-
bution appUed to Sf, would give some idea of the
variabUityascribable to random sampling (Ricker
1945b), but also states that "an estimate of error
obtained dii'cctW from the data themselves, for
both the general and the special case, is to be
desired."

Underbill (1941) applied this method and
formula 18 to the computation of a chub-sucker
population of a pond in New York, and Roach

198

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

(1943) has done the same in estimating the white-
bass population of an Ohio lake.

Schumacher and Eschmoyer (1943) have de-
vised an estimate of A'^ from repeated samplings
which is different from that of Schnabel. They
assume that the weight, or value, of each sample
is proportional to the nimiber of fish in the sample.
Under this assumption, an estimate of A^ is arrived
at by minimizing the sum of the squares of the

T
weighted discrepancies of the ^' from their esti-

mates

This leads to the formula

A^^

1=1

i=l

(20)

which is applied by these authors to the estimation
of fish populations of a pond in Tennessee.

These authors have also derived an expression
for the sampling error of A'^. They take as the
standard error of A'^ the square root of

JVV_

(21)

where

-^-iLSi^ivS^'^'J

In the last formula I have corrected a typo-
graphical error which appears in the original paper
(formula 3, page 234) and which Professor Schu-
macher has kindly pointed out in a private
communication.

In table 2 is recapitulated a numerical example
from Schumacher and Eschmeyer (1943), pertain-
ing to the estimation of a population of bullheads
in Yellow Creek Pond, Tennessee. Substituting
the appropriate sums from this table in formulae
[20] and [21], we obtain the following estimates
for A'^ and its standard error (o-at):

A^=

49,398,907

35,121

1,412

14V

27.992263-

35,121'
1412 ,

= 0.222S

afi

^^

412)3(0.2228)^

35,121

:134

Table 2. — Schumacher and Eschmeyer' s method oj com-
puting a fish ■population by repeated sampling and marking

[Data from table 2 of Schumacher and Eschmeyer (1943)]

Date (1941)

Number

of marked

flshin

pond

Number
of flsh in
sample

Number

of marked

fish in

sample

IV-m

r,(,

Ti

Tli

ti

Oct. 3

Oct. 6

Oct. 7-

Oct. 8

Oct. 9

Oct. 10

Oct. 11

Oct. 12

Oct. 13

Oct. 14

Oct. 15

Oct. 16

Oct, 17

Oct. 18

Oct. 19

23

57
102
149
172
232
267
309
329
386
372
383
383
383
383

39
49

51
28
79
43
49
22
38
22
15
4
25
98
71

4
4
4
5
19
8

2
11
5
4
1

30
12

20. 631

159, 201

530, 604

621, 628

2, 337, 136

2, 314. 432

3, 493, 161
2. 100. 582
4.113.158
2, 788, 102

2, 075, 760
586, 756

3, 667, 225
14, 375. 522
10, 414. 919

92

228

408

745

3,268

1,8,';6

1. 869

618

3,619

1,780

1,488

383

2,681

11,490

4, 896

0. 41025G
. 326531
. 313725
. 892857

4. 569620

1. 488372
1.000000

. 181818
3. 184211
1. 136364
1. 066667

. 250000

1. 960000
9. 183673

2. 028169

Total.

49, 598, 907

35, 121

27 992263

Kicker (1945b) has investigated the relative
efficiency of Schumacher's estimate (20) and
Schnabel's formula (18). He states:

From an exchange of letters with Dr. Schumacher it

appears that the efficiency of this expression is at a maxi-

T
mum when -^ is equal to 0.5, whereas Schnabel's second, or

approximate formula becomes most efficient as (T/N) —►0,
and the two formulae are of equal efficiency when
T/N=0.2o. Consequently Schnabel's form will ordinarily
be best, since the value of T/N rises gradually from a very
small initial magnitude, and, except on quite small bodies
of water, will not often exceed 0.25 even when the experi-
ment comes to an end. Of course Schnabel's long formula,
carried to several terms, can always be used if the best
possible estimate is desired; but the labor of computation
will rarely be warranted, considering the magnitude of the
sampling and probably systematic errors in such experi-
ments.

Krumholz (1944) has made a practical check of
the accuracy of estimation of a fish population by
repeated sampling, marking by clipped fins, and
the application of Schnabel's formula (18). He
computed the population of fish over 45 milli-
meters in length in the north basin of Twin Lake,
Mich., in this manner and then poisoned the area
with rotenone and counted the fish poulation
directly. He concluded:

The estimate from netting operations was very close to
that obtained by poisoning in this first check on the fin-
clipping method for estimating fish populations. Further
studies of this type are needed to prove definitely the
accuracy of the method. . . . Other checks of this method
will be made when conditions permit.

SIZE OF ANIMAL POPULATIONS

199

ESTIMATION OF A CHANGING
POPULATION

Some fishes, such as salmon spawning in a given
stream or lake, do not always form a single, homo-
geneous, completely mixed population. There
may be a tendency for the fish which migrate to
the spawning grounds earliest to complete their
spawning and die earliest; there results a positive
correlation between time of migration past a
point below the spawning grounds and the time of
appearance on, and of death at, the spawning
grounds. If, now, we are tagging fish below the
spawning grounds, or even on these grounds, and
later sampling for tag ratios, the "mi>dng" of the
fish between tagging and sampling is not complete,
and this may need to be taken into consideration
in our estimation of the population. Similar
situations may occm- among other migratory
animals.

When there exists such a correlation between
time of tagging and time of subsequent sampling,
the samples drawn during any particular part of
the season do not represent all parts of the popula-
tion equallj^; the sample is not a random sample of
the whole population. The possible effects of
this on our estimates by formula 1 are easily seen.
If, as has already been pointed out, all parts of the
population have the same tag ratio, if the tags are
"evenly distributed," it will make no difference
whether the subsequent saniples represent the
various parts of the population equally or not.
Likewasc, if the population is "evenly" sampled
after tagging, that is, if the probability of a given
fish being included in the sample is not a function
of the time of sampling (and, therefore, not a
function of the tinae of tagging), any uneven dis-
tribution of tags by time of migration will have
no effect. If, on the other hand, the probability
of a fish being tagged (the tag ratio) varies with
the time of tagging, and the probability of being
included in the subsequent sample varies with the
time of sampling, and there also exists a correla-
tion between time of tagging and time of sampling,
it is obvious that the tag ratio in the total sample
for the season will differ from that of the popula-
tion to some extent, depending on the magnitudes
of these factors.

Presented here is a method of estimating the

population by which these errors may be reduced
when the tagging is done by means of numbered
tags, so that the relation between time of tagging
and time of recovcrj'' may be estimated. I am
indebted to Dr. S. Lee Crump of the Iowa State
College Statistical Laboratory for much assistance
with the mathematics involved.

If our tagged fish have been marked by num-
bered tags, we know both the date of tagging and
date of recovery for each one recovered. This
makes it possible to tabulate the recoveries by
time of tagging and time of recovery, using as a
time interval a convenient period of days. Our
notations for the elements involved in the discus-
sion of this section, in addition to those introduced
before, are as follows:

Let

A^„ = the total number of fish passing the point
of tagging during the a'" period of tagging.
(a=l,2, 3, ... a).

ra = tho number of these fish which are lagged
dm-mg the a'* tagging period.

n„t=tha number of fish out of the A'a that are
subsequently recovered during the ;"' recovery
period.

Tai=the number of fish out of the Ta that die
and are thus available to be recovered during the
i'" recovery period.

m„<=the number of tagged fish tagged during
the a"" period of tagging and recovered during the
i'" period of recovery (i=l, 2, 3, . . . s).

m'a,= the number of untagged fish passing the
point of tagging during the a'" tagging period and
recovered during the i'" recovery period.

The following summation conventions are cni-
ployed:

i a a i

^m'ai = m'a- '^m'a, = m'.i

i a

Obviously,

Also let:

ma--\-m'a. = na.

m.i + m'.t=(^i

200

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

A'^,=the number of fish dying on the spawning
grounds during the i'" recovery period.

Pi =

The data available from a given experiment can
be laid out in a table as follows:

Period of tagging (a)

Total
tagged

fish
recov-
ered

Total

flsh
recov-
ered

1

2

3. . . a

Period ol recovery (i):
1 _ .

mil
mi2

77121

maa
mn

mat

mai . . . TTioi
raaa . . . moa
maa . . . moa

77131 . . . TTlof

771.1

m.2
m.3

771 ,

Ci

2

c,

3

c.

- -

ci

Total tagged flsh re-
covered

TBI.

■mi.

7713 . . . ma

"=()■

Total fish tagged -_

T,

T,

Ta . . . To

Of course, 'E.T^^T and "^Ct^n.

a i

Now, the nuin])er of fish passing the tagging
point during a which die during period i might be
estimated by

n „( =

rria

P.i

(22)

(I shall denote "estimate of" by the asterisk
herein) where Pai is the probability of a fish being
tagged during a and recovered during i. This
probability is unknown, and om' best available
estimate of it seems to be the joint probability
Piq^a, where these terms are as defined above.
This amounts to taking as the probability of
recovery the average probability of recovery of
all the fish passing the tagging point during a,
and as the probability of being tagged the average
probability of being tagged of all the fish dying
during period i.

If the samples drawn for tagging and the samples
later drawn for tag ratios are representative of the
parts of the population from which they are
drawn, Pi and ga may be estimated from the data
as follows:

'Z a =

nia

p-^^ m.j

m.i

The estimate of iiai is, then, given by

«,'

mat

(24)

which is equivalent to

,(; la (yi

it ai — '*'' a i • • • •

m„. m.i

The estimate of the total population is obtamod
bj' summing all these n*ai, thus

TaCt

N* = J2J2ma,

(25)

m„m.i

A somewhat more rigorous derivation, based on
Bayes' theorem, has been suggested by Dr.
Crump:

The problem is to estimate the Ua, and the qa-
if we can do this we can take as our estimate of A^,

n *
a qc

Let P(i/a) be the probability that a fish tagged
during the a'" period dies and is recovered during
the i'" recovery period. Now we have C, fish
taken diu"ing the i'" recovery period to be allo-
cated over the "a" tagging periods, and hence
we want the probability that a fish taken during
the i'" recovery period is one of those which passed
the tagging point during the a'" tagging period.
Denote by P{ali) the desired probability, and by
P{a) the true proportion of the ?i fish recovered
which passed the tagging point during the a'"
tagging period. Then by Bayes' theorem

P{i/a)P(a)

Piali)-

'j:Piilcc)P{a)

(26)

we have the problem of estimating the P{i/a)

and the P(a).

Now,

P(„)=-l-—

and we may estimate P(a) by

P*(a) =

m.

To estimate Pii/a) we may use

rrici

P*(ila) =

rua

Then our estimate of Pia/i) becomes
m..ma m..

P*{a/i) =

nia

Sr^ m„-ma
/ vm..m„

m.

(23) This gives us for an estimate of n„.

■ri*ai=j;:c,p*iah)='z:r,

m.i

mai

m.i

(27)

(28)

(29)

(30)

SIZE OF ANIMAL POPULATIONS
Table 3. — Data from a lagging experiment on migrating adult sockeye salmon

201

Week of tagging (a)

Total
tagged Ssb
recovered

Total
flsh re-
covered

Cilm-i

I

2

3

4

5

6

7

8

Week of recovery (0 :

1

1

1
3

7

1
11
33
24

5

m-i

3
19
82
184
159

9
30
26

8

C,
19
132
800

2,848

3.476

644

1,247

930

376

6 33

2 ...

5
29
79
52
3
2
7
3

"

6 95

3

2

U
67
77
2
16
7
3

4

14
25
3
10
6
2

15 4S

5

21 86

6 . -.

71 56

1
6

1

8

1

35 77

9

Total tagged flsh recovered ma-.-

3

11

76

180

183

60

6

1

520

Total fish tagged Ta

15
5.00

59
5.36

410
5.39

695
3.86

773
4.22

335
5.58

59
9.83

5
6.00

Talma-

2C. = 10,472.
2 To = 2,351.

Taking our estimate of qa as before (23), and as
our estimate of N

a y o

we have, then,

„ i m.i rria.

(31)

(32)

which is the same result as obtained in formula 25.
Application of this method of population estima-
tion may be illustrated by the data from a tagging
e.xperiment conducted by me on a migrating popu-
lation of adult sockeye salmon in British Columbia.
A total of 2,351 fish were tagged in a certain river,
on the waj' to their spawning grounds, over an
8-week period. Later, tag-ratio samples were
drawn regularly over a 9-week period as the fish
spawned and died on the spawning gi-ounds
farther upstream: 10,472 fish, of wliich 520 had
been tagged, wore recovered in these san^ples. In
table 3 are tabulated, in the same form as the
table on page 200, tag recoveries by week of tagging
and week of recovery, with data on total numbers
tagged and recovered for each week. From these
(lata are computed values of Talma, and dim.,
tabulated along the margins. From these com-
puted values and the tag-recovery data tabulated
in the body of the table has been computed the
estimate of the population, as shown in table 4,
according to formulae 24 and 25 (or 32). Tiie
values in the body of tliis table are values of

Ta d

n

mat which sum to the estimate of A^,

ma. m.i '

47,860 fish.

Table 4. — Compulation of pofidalion estimate by formulae
2/f and S5 from the data of table 3

Week of tagging (a)

Total

1

2

3

4

5

6

7

8

Week of recovery (i) :
1

32

34

112
366

34

412

1,736

2,002

689

380

100

2

134

1,093

4,720

4.388

829

321

967

544

3

98

453

4,377
7,103

604
2,807
1,057

595

3, 740

4

1,209
3,049
1,198
2,320
1,198
525

12, 308

5

15. 129

6..

3 017

409
1,758

208

6,065
5 173

8 .

193

9..

1 664

Total

130

512

6,352

12,996

16,996

9,499

2,167

208

47,800

From formula 25 (or 32) it may be seen that
where the tagging or the sampling is uniform, this
estimate reverts to the simple case first discussed.
For, if the probabiUty of being tagged is constant

for all i, the expected value of
Then,

N*=j:j:ma>^

d

n

m-i m'

■, a constant.

n

ma- m -

T

m .

(33)

wliich is identical with formula 1 since m..=t in

formida 1.

Likewise, if the probabiliity of being recovered is

T T
constant, the expected value of — - is , a constant.

Then,

m„

m..'

A'*=z;z;wai

d T

(34)

m.i m. . m . .

The tagging experiment illustrated in table 3 is

a practical situation of this sort. iVlthough the

probabihty of a fish being recovered, estimated

from dlm.t, changed very much during the course

202

FISHERY BULLETIN OF THE FISH AM) WILDLIFE SERVICE

of the season, the probability of being tagged,
judged from Ta/nia- was fau'ly even over most of
the season. In consequence, the estimate from
the simple formula (1)

(10,472) (2,351)^ 345

520 'i^'rito

is practically identical with the estimate from
formula 25 (or 32).

T = 1000
71-2 000

.17
.16
.15
.14
.13
.12
.1 I
.10
.09

Q..07

u.
O.06

(ii

o

05

.04

.03

.02

.01

.00

^.

Z.

/.

^

7

y

7

/

/

/

J.

^

T

-6

z

-7

^

-9

10

-II
-12

-15

20

-25

-30

o
o
o

is.

o

-J
<
o
en

■40

-60
_80
■100
200

.00 01 .02 .03 .04 .05 .06 .07 .08 .09 .10 .11 .12 .13 .14 .15
SCALE OF P* = ^

Confidence limits on .sample tag ratios and on estimated population numbers, at a confidence level of 95 percent,
experiments involving 1,000 tagged individuals and samples of 2,000.

for

SIZE OF ANIMAL POPULATIONS

LITERATURE CITED

203

Cagle, Fred R.

1946. A lizard population on Tinian. Copeia, 1946,
No. 1, pp. 4-9.

Chapman, D. G.

1948. Problems in enumeration of populations of spawn-
ing sockcye salmon. 2. A mathematical study
of confidence limits of salmon populations cal-
culated from sample tag-ratios. Int. Pacific
Salmon Fish. Comm., Bull. II, pp. 69-85.

Clopper, C. J., and E. S. Pearson.

1934. The use of confidence or fiducial limits illustrated

in the ca.se of the binomial. Biometrika, vol. 26,

pp. 404-413.
Cramer, H.

1946. Mathematical methods of statistics. Princeton

Univ. Press, 1946, 575 pages.
Dahl, Knut.

1943. 0rret og 0rretvann. Studier og fors0k. NY

Utgave. J. W. Cappelens Forlag, Oslo, 1943,
182 pages.
Dice, L. R.

1941. Methods for estimating populations of mammals.
Jour. Wildlife Management, vol. 5, No. 4, pp.
398-407.

Green, R. C, and C. A. Evans.

1940. Studies on a population cycle of snowshoe hares
on the Lake .Alexander Area. I. Gross annual
census, 1932-1939. Jour. Wildlife Manage-
ment, vol. 4, No. 2, pp. 220-238.

Jackson, C. H. N.

1933. On the true density of tsetse flies. Jour, .\ninial

Ecology, vol. 2, pp. 204-209.
1936. Some new methods in the study of Glossina mossi-
lans. Proc. Zool. Soc. London, 1936, pp. 811-
896.

Kendall, M. G.

1944. The advanced theory of statistics, vol. I. J. B.

Lippincott, London. 457 pp.
1946. The advanced theory of statistics, vol. II. Charles
Griffin & Co., London, 521 pp.

Kendeigh, S. C.

1944. Measurement of bird populations. Ecol. Mono-
graph 7.^ (1) : 67-106.

Krumholz, Louis A.

1944. A check on the fin clipping method for estimating
fish populations. Papers Michigan Acad. Sci.,
Arts and Letters, vol. 29, pp. 281-291.

Leopold, .\ldo.

1935. Game management. New York, 481 pages.

Lincoln, F. C.

1930. Calculating waterfowl abundance on the ba.sis of
banding returns. U. S. Dept. Agric. Circ. 118,
pp. 1-4.

Neyman, Jerzy.

1934. On the two different aspects of the representative
method — the method of stratified sampling and
the method of purposive selection. Jour. Royal
Stati.st. Soc, vol. 97, pp. 558-625.

Pearson, Karl.

1928. On a method of a.scertaining limits to the actual
number of marked members in a population of
given size from a sample. Biometrika, vol. 20,
pp. 149-174.

RiCKER, W. E. '

1942. Creel census, population estimates and rate of

exploitation of game fish in Shoe Lake, Indiana.

Invest. Indiana Lakes and Streams, vol. 2.

pp. 216-253.
1945a. .\bundance, exploitation and mortality of the

fishes in two lakes. Invest. Indiana Lakes and

Streams, vol. 2, pp. 345-448.
1945b. Some applications of statistical methods to

fishery problems. Biometrics Bulletin, vol. 1,

No. 6, pp. 73-79.
Roach, Lee S.

1943. Buckeye Lake white bass. Ohio Jour. Sci., vol.

43, No. 6, pp. 263-266.

Sato, Rokxtzi.

1938. On the migratory speed of salmon and the stock
of red salmon estimated from the tagging experi-
ments in northern North Pacific. Bull. Jap.
Soc. Sci. Fish, vol. 7, No. 1, pp. 21-23.

Schnabel, Zoe E.

1938. The estimation of the total fish population of a

lake. Am. Math. Monthly, vol. 45, pp. 348-3.52.

Schumacher, F. X., and R. W. Eschmeyer.

1943. The estimate of fish populations in lakes or ponds.
Jour. Tenn. Acad. Sci., vol. 18, pp. 228-249
(1943).

Underbill, A. Heaton.

1941. Estimation of a breeding population of chub
suckers. Trans. Fifth North American Wild-
life Conference, 1940, pp. 251-256.

VoRHiEs, C. T., and W. P. Taylor.

1933. The life history and ecology of jack rabbits Lepus
alleni and L. californicus .ssp. in relation to
grazing in Arizona. Univ. Ariz. Tech. Bui.
49, pp. 472-587.

Wright, H. M.

1939. Field and laboratory technic in wildlife manage-

ment. Univ. of Mich. Press, .Ami Arbor, 1939,
107 pages.

o

UNITED STATES DEPARTMENT OF THE INTERIOR, Oscar L. Chapman, Secretary
FISH AND WILDLIFE SERVICE, Albert M. Day, Director

AGE, GROWTH, AND PRODUCTION OF
YELLOW PERCH IN LAKE ERIE

By Frank W. Jobes

FISHERY BULLETIN 70

From Fishery Bulletin of the Fish and Wildlife Service

VOLUME 52

UNITED STATES GOVERNMENT PRINTING OFFICE

WASHINGTON : 1952

For sale by the Superintendent of Documents, U. S. Government Printing Office, Washington 25, D. C.

Price 20 cents

CONTENTS

Page

Commercial production of yellow perch in Lake Erie 205

Materials and methods 211

Determination of age and growth of Lake Erie yellow perch by the

scale method 214

Validity of the annulus as a year mark 214

Body-scale relation 215

Calculation of growth • 218

Calcxilated growth histories of the age groups 218

Discrepancies in the calculated growth histories of different age groups. _ 220

Selection by gear 220

Segregation correlated with sexual maturity ..'- 22 1

Selective destruction according to the legal size limit 222

Other causes 223

General growth curves 223

Growth in length 223

Growth in weight 224

Growth of yellow perch in Lake Erie compared with that in other

waters 227

Growth compensation 229

Proportion of season's growth completed at time of captm-e 230

Aimual fluctuations in growth 232

Length-frequency distribution 236

Age composition and abundance of year classes 243

Length-weight relation 252

Coefficient of condition (K) 253

Monthly and annual fluctuations ui the value of K 254

Fluctuations m value of K with stage of maturity 256

Fluctuations in value of if with age 256

Influence of rate of growth on value of K 257

Effect of type of gear on determining value of K 258

Size at matm^ity 259

Sex ratio 260

Summary 262

Bibliography 264

II

AGE, GROWTH, AND PRODUCTION OF YELLOW PERCH IN LAKE ERIE

By FRANK W. JOBES, Fishery Research Biologist

The American yellow perch, Perca flavescens
(Mitchill), is one of the most common food fishes
native to the lakes and streams of the northeastern
United States and southeastern Canada. It con-
tributes heavily to the take by hook and line
throughout its range and foiTas an important part
of the catch of the modern commercial fisherj' in
the Great Lakes.

The present study of the yellow perch is part of
an extensive investigation of the Lake Erie com-
mercial fisheries begun by the former U. S. Bureau
of Fisheries and continued by the U. S. Fish and
Wildlife Service. In the years 1927 through 1931
field work was carried on in cooperation with the
States of Ohio, Pennsylvania, and New York, the
Province of Ontario, the city of Buffalo, and the
Buffalo Society of Natural Science; materials were
collected also in 1932, 1934, and 1937, and in the
years 1943 through 1948. This report is based
primarily on the data for the specified years from
1927 to 1937 (referred to here as 1927-37) because
in each of those years the materials consisted of
random samples of aU yeUow perch taken by the
nets. The 1943-48 data are from random sam-
ples of the commercial catch only (fish 8)2 inches
or more in total length) and will be used only
where they add to the knowledge gained from the
1927-37 data.

The assistance of the officials and employees of

all the agencies involved in this investigation is
deeply appreciated. Without their cooperation in
the collection of data and the loan of materials
this study would have been much more restricted
in scope, if not impossible. Special thanks are due
Dr. John Van Oosten for directing the study and
critically examining the manuscript, and Dr.
Ralph HUe for substantial assistance in the anal-
j'sis and interpretation of the data. N. H. Lager-
strom, Oberlin, Ohio, translated the Swedish and
Norwegian references listed in the bibliography.

Several authors have studied the age and growth
of the yellow perch without making a critical study
of the validity of age determinations based on
scales. Jobes (1933) and Schneberger (1935) cal-
culated lengths from scale measurements on the
assumption that the ratio of body length to scale
length is constant after the first annulus is formed.
Hile and, Jobes (1941) determined the body-scale
relation for the yellow perch in Saginaw Bay
(Lake Hui-on) and corrected the lengths computed
by direct proportion to conform to the empiri-
cally determined body-scale relation. Before a
detailed study of the life history of the yellow
perch in Lake Erie could be undertaken, it was
necessary to demonstrate that ages read from
scales are accm'ate and to determine the most
satisfactoiy method of calculating growth from
scale measurements.

COMMERCIAL PRODUCTION OF YELLOW PERCH IN LAKE ERIE

The earliest records of the production of yellow
perch in Lake Erie are for the year 1885. The
species was taken commerciaUy before that time
but was not considered important enough to war-
rant separate treatment in the earlier statistical
reports. Table 1 gives the available figures on
production for the years 1885 to 1947. The pro-
duction records for United States waters, for On-
tario waters, and for the entire lake are sho\\Ti
graphically in figure 1.

Although the record of the catch in the United
States waters is not complete for the earlier years
of the fisher}', the annual yield appears to have
been greater before 1900 than in the period im-
mediately after. The extremes in the fluctuation
in annual production during the earhest period,
1885-99, occurred in the years 1885 and 1889,
when catches of 1,601,000 and 3,830,000 pounds
were reported. The fragmentary statistics indi-
cate a good production in this period; the average

205

206

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Table 1. — Annual production of yelloiv perch in Lake Erie, 1885-1947
[In thousands of pounds]

United States i

Canada (Ontario)'

Year

Michigan

Ohio

Pennsylvania

New York

Tot;ll

Western
part 3

Eastern
part*

Total

LAKE

1885

100

1,266

225

11

1,601

1886.. __

1887..

1888...

1889

96

159

3,204
2,483

459
209

70
49

3,830
2,900

1890

1891_

1892

138
223
115
266
202
147
164
92

128
136
107
81
70
106
99
118
147

1893 -

2,595

1894

282
241
266
238
121
209

398

255

373

218

436

346

176

364

450

428

464

681

913

794

1,137

809

614

852

1,810

876

1,006

1,676

1,810

281
166
208
263
258
182

297
253
193
201
161
207
168
108
180
153
210
167
198
161
271
234
156
143
246
221
267
289
299

663
397
474
500
379
391

696

508

566

418

698

553

334

472

630

681

674

847

1,110

955

1,408

1,042

769

995

2,056

1,097

1,272

1,965

2,109

2,397

2,192

2,060

1,716

2,491

4,330
5.689
3,420
4,266
5, 029
2,729
5,671
5,634

1,254
1,691
2,696
1,407
1,994
2,060
964
711
1,372
1,207
2,417
2,262

1896

1896

1897 •

2,604

407

96

3,253

3,763

1898

1899

2,175

816

268

3,340

3,731

1900..- - -

1901

1902 _.

1903-

626

141

27

873

1,292

1904

1906 _. _

1906

1907

1908..

1,441

85

83

1,766

2,386

1909

1910

1911

1912.

86
66
67
108
136
140
68
37
42
41
68
36
34
48
63
32

20
35

34
72
97
87
48
54

17
16
25
13
14
25
36
24
20
29
46
49

1913

•686
1,888
1,698
1,370
866
919
2,673
1,189
2,063
1,768
1,668
» 1,677
2,202
2,414
2,468

3,678
6,779
4,187
8,455
9,239
3,024
13, 252
8,303

1,886
1,596
4,912
1,493
2,774
3,596
1,790
1,178
2,092
1.260
2,636
1,687

'114
81
105
116
173
80
61
18
70
64
98
199

4
13
22
17
79
21
114
10
28
47
67
31

870
2,039
1,933
1,637
1,269
1,088
2,776
1,259
2,192
1,926
1,870
1,941
2,458
2,622
2,748

4,275
6,043
4,341
9.062
9,741
3,434
14,218
9,046

2,051
1,760
6,187
1,608
3,030
3,821
1,958
1,253
2.188
1,352
2,685
1,797

1,825
3,447
2,975
2,406
2,254
3,145
3,872
2,532

1914

1916

1916

1917

1918

1919..

1920

1921 _

1922

4 036

1923

4,267
4,133
4,618
4,338
6,238

8,606
11,733
7,761

13, 327

14, 770
6,163

19, 889
14, 678

3,305
3,441
7,782
3,015
5,024
6,871
2,922
1,964
3,560
2,559
5, 102
4,049

1924

1,719
1,304
1,323
1,888

3,577
4,782
2,839
3,466
3,667
1,474
3,460
3,795

887
1.298
2.139

956
1.390
1,398

640

536
1.146

982
2.110
1.464

473
756
393
603

753

907

680

799

1,372

1,265

2, 211

1,838

367
393
457
451
604
652
324
176
226
225
307
798

1925

1926..

76
206

447
177
85
480
330
278
798
642

131

106
200
80
216
163
89
31
66
58
95
97

68
40

130
52
34

55
75
45
119
146

18
34
50
21
26
38
44
20
20
6
8
63

1927

1928

1929..

1930

1931.

1932

1933..

1934

1935

1936..

1937

1938..

1939

1940 .

1941

1942 .

1943

1944 .

1946

1946 .

1947

' Records of production from United States waters and from entire lake tor
1886-1940 are from Gallagher and Van Oosten (1943). Statistics of produc-
tion from United States waters for later years were compiled originally in
the Great Lakes Laboratory of the U. S. Fish and Wildlife .Service from
data supplied by the several States and have been published in the Com-
mercial Fishery Statistics series of the Service.

' Canadian (Ontario) records for 1894-1939 are from Ford (1943). Data
on the yield from Canadian waters in later vears were supplied by the On-
tario Department of Lands and Forests. The figures on the catch from all

of the Canadian waters of Lake Erie may be found in the annual reports of
the Ontario Dep.artment of Lands and Forests.

3 West end to Port Burwpll.

' East of Port Burwell.

5 Fiscal year, July 1, 1896, to June 30, 1897, in United States waters, except
Michigan.

• Fall catch only.

' Estimated.

> Fall catch ol 1924 plus spring catch of 1925.

YELLOW PERCH OF LAKE ERIE

207

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SONOOd JO SNOinilW

208

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

of the recorded yields was 2,946,000 pounds.'
The lowest annual United States yield on record
occurred in the next period, 1900-1927, when in
1903 only 873,000 pounds were reported. (No
reference has been found that suggests that the
statistics for 1903 are incomplete.) In only 6
years (1914, 1919, 1921, 1925, 1926, and 1927) of
the 16 in this period did the annual catch from
United States waters exceed 2 miEion pounds.
The average annual yield of 1,905,000 pounds in
this period was only 65 percent of the 1885-99
average. The upward trend that was to cany
the yield in United States waters to the unprece-
dented catch of nearly 14^ million pounds in 1934
actually began in 1925, but was relatively slight
until 1928. The average of 7,520,000 pounds for
the years 1928-35 was 2.55 times the average of
the 1885-99 period and 3.95 times the 1900-1927
average. Not only was production high in 1928-
35, but the fluctuations in annual catch were
sudden and violent (for example, 9,741,000
pounds in 1932, 3,434,000 pounds in 1933, and
14,218,000 pounds in 1934). The violent fluc-
tuations continued into the 1936-47 period, when
the average annual production fell to 2,390,000
pounds. The average annual yield in these most
recent years was 81 percent of that of the 1885-99
period, and only 32 percent of the 1928-35 aver-
age. The grand average for the years of recorded
statistics was 3,262,000 pounds.

The Ohio production has always dominated the
United States catch, and in the years for which
complete data are available Ohio, on the average,
has accounted for more than half of the yield of
the entire lake. Furthermore, the relative im-
portance of the Ohio catch in the United States
production has shown a distinct tendency to
increase. In the early period, 1885-99, Ohio
produced 77.8 percent of the total United States
yield. This percentage increased to 87.7 in the
1900-1927 period, to 92.9 in 1928-35, and to 93.1
in recent years. The proportion of the United
States catch taken in each of the three remaining
States has tended to decline.

If the Ontario statistics were to be segregated
by periods independent of those of the United
States, the following intervals would be selected
to show the trend of production: 1894-1911,

' To make use of all available statistics, the averages computed from table
1 for United States waters, and for the entire lake, are the sums of the corre-
sponding averages of the individual States and the Province of Ontario.

1912-20, 1921-27, 1928-35, and 1936-47. The
Ontario figures in table 1 show a progressive in-
crease in catch with each succeeding period except
the last. This trend on the Canadian side of
Lake Erie, therefore, does not correspond to that
on the United States side, except during the
last two periods, 1928 and following years. Ap-
parently the Canadian fishery for yellow perch
began later and developed more slowly than that
of the United States.

The earliest statistics of the catch in Ontario
waters of Lake Erie show a relatively low yield
with no extremely large variation from the average
of 532,000 pounds during the period 1894-1911.
The average annual catch of the next period, 1912-
20, was 1,189,000 pounds or 2.23 times the 1894-
1911 average; in only one year, 1918, did the take
exceed IK million pounds. The 1921-27 period
was one of relatively stable production with an
average catch of 2,133,000 pounds (1.79 times the
average of the preceding period) . The large annual
catches and increased variability of the annual
yields in Ontario waters in 1928-35 were not un-
like those in United States waters for the same
period, except that in Ontario production did not
reach such heights and the fluctuations in catch
were not so violent as in the United States. The
average annual Ontario yield for this period was
4,596,000 pounds, or 2.15 times that of the preced-
ing period. Production during 1936-47 declined
to an average of 1,660,000 pounds, or to 36 percent
of the 1928-35 average. In only 4 of the last 12
years, 1938, 1941, 1946, and 1947, did the catch
exceed 2 million pounds. The grand average for
the 54 years of recorded statistics was 1,702,000
pounds.

The production from the western part of the lake
(west end to Port Burwell), on the average, made
up more than 60 percent of the Canadian total in
each period. The percentage increased from 62 in
the years 1894-1911 to 82 m 1912-20, and re-
mained relatively constant, between 74 and 78, in
the last three periods. This stabilization in the
relative productivity of the two sections of the
Canadian waters is in contrast to the situation in
the United States waters where the western (Ohio)
section increased in importance each period.

The catch in the entire lake showed variations
similar to those in United States waters, except
during the years 1921-27, when the total produc-
tion was augmented by the increased yield in

YELLOW PERCH OF LAKE ERIE

209

Ontario waters. The average total production of
about 3/3 million pounds diu-ing the period 1885-99
appears high only when consideration is given the
low fishing intensity and the crude apparatus em-
ployed. The output of the fishery was low in 1903
but tended to increase, though h-reguJarly, during
the 1900-1920 period. The average annual yield
of 2,464,000 pounds during this period was approxi-
mately 70 percent of the earher average. The
following period, 1921-27, was the steadiest one of
the fishery, with but little fluctuation from an
average of 4,384,000 pounds. This average was
1.78 times the average of the preceding period and
about 1.29 times the 1885-99 average. The
period 1928-35 was one of tremendous annual
productions and violent fluctuations in yield from
year to year. In every year, the catch exceeded
the best of any previous period, and in 5 of the 8
years it was more than 10 million pounds. The
average annual catch of 12,116,000 pounds was
4.92 times the 1900-1920 average and 2.76 times
the 1921-27 average. Dm-ing 1936-47, production
fell off', with only one year, 1938, yielding as much
as the poorest of the preceding period. Wide
fluctuations in yield persisted into this last period.
They were caused largely by variations in the
catch in United States waters, and these in turn
were due to variations in Ohio's yield. The aver-
age catch of 4,050,000 pounds in 1936-47 was
only about a third of the 1928-35 average but was
approximately 1.25 times the average of the
earliest period, 1885-99.

The grand average production of yellow perch m
all waters of Lake Erie for the years 1885 to 1947
was 4,964,000 pounds.

The tendency toward an increasing variability
in the annual catch in United States waters
suggests the dependence of the commercial fishery
on a small number of age groups. This inter-
pretation is supported by the observation (p. 245)
that in the present-day fishery a year class is
normally of major importance for little longer than
a single year. Under such conditions it may be
expected that production would be sensitive to
variations in the strength of year classes and
hence subject to sudden and wide fluctuations.

Any discussion of the factors that contributed
to the changes that have occurred in the produc-
tion of yellow perch in Lake Erie must be in
large measure speculative. Although certain
events are known to have contributed to the

observed changes, their precise effects are diflScult
to evaluate. Brief mention may be made of the
more important factors.

The early fishery in Lake Erie was conducted
primarUy on the inshore grounds with relatively
crude gear. As production on these grounds
declined, larger, faster, and seaworthier boats
were buOt which permitted not only the extension
of operations to more distant grounds but also the
handling of more nets. The number of boats in
operation also increased rapidly with expansion of
the fishing grounds. Further increase in the
amount of gear handled by each boat foUowed
introduction of the power lifter for gill nets in
the 1890's and for trap nets in the early 1930's.
Efficiency of the nets was increased by reducing
the size of the meshes, by using finer thread in
gill nets, and by "reefing" or tying down the
gill nets. Gill nets were made still more eflficient
by the development of the buU net, a gill net 100
meshes deep, fished in all strata of water from top
to bottom. The shift from pound nets to trap
nets and more recently a partial shift from gUI
nets to trap nets also increased exploitation, since
trap nets are the most efficient gear now in use.

Although it is not possible to state precisely
the extent to which fishing intensity has increased,
it is valid to state that the increases in the amount
and efficiency of gear just mentioned have led
to a multiplication of fishuig intensity in recent
years over that of the early fishery.

For many years the practice has been to decrease
gradually the size of mesh in the nets to com-
pensate for diminishing yields. It was not until
1937 that the State of Ohio reversed the trend
by increasing the size of mesh in trap nets to
afford greater protection to the smaller fish.

In addition to these developments that have
affected the fishery as a whole, there have been
other cu'cumstances that contributed more speci-
fically to an increase in the intensity of the fishery
for perch. The collapse of the cisco fishery, for-
merly the most productive in Lake Erie, in 1925
forced many operators, particularly the gill-netters,
to turn to other species. The resultmg increase
in intensity of the fishing for perch was an impor-
tant factor in the rise in production of this species.
The yield of perch was affected also by the reduc-
tion in July 1929 of the minimum legal size from
9 to 8/2 inches in the State of Ohio. The record
catch of 13 million pounds in' Ohio in 19.34 oc-

210

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

curred in a year wlien the officials failed to enforce
the law on size limits.

Economic conditions doubtless have had an
effect on the annual fluctuations in the yield of
perch, but the relation is too obscure to point
to any major change in the annual catch as the
result of changes in the price of or demand for
perch.

The discussion of the relation of production to
fishing intensity, to fishery laws and enforcement
of laws, and to market conditions, has been given
in advance of the treatment of the relation between
the catch and the abundance of perch, not with
the intent to imply that abimdance is not of great
importance in determining the yield, but rather
to bring out the dangers of interpreting too freely
fluctuation in production as the result of fluctua-
tion in abundance. To be sure, abundance and
catch are closely related; but careful recognition
also must be given to other factors that affect the
annual yield.

Abimdance may be considered in terms of long-
period changes such as those brought about bj^
the prosecution of the fishery or by gradual changes
in the environment, or in terms of the short-period
fluctuations traceable to variations from year to
year in the success of natural reproduction. Both
types of changes are reflected in fluctuations in the
annual catch. Many of the variations in annual
yield as recorded in table 1 are probably to a large
extent the result of relative strength or weakness
of year classes. Age determinations have shown,
for example, that the increases in production in
1928 and 1929 were not exclusively the result of
increased fishing intensity and the reduction of
the legal size for perch, but were furthered also by
the phenomenal richness of the 1926 year class.

The fluctuations in abundance that arise from
variations in the strength of year classes must be
accepted by fishermen as part of the natural course
of events, since at present very little can be done
to increase the survival of young. The environ-
ment may be improved by such measures as the
control of poflution and erosion. The value of
such measures to the Lake Erie fisheries is open
to question, since it has been shown that no ex-
tensive areas of heavy pollution e.xist that would
be inimical to fish life (Wright and Tidd 19.33,
Fish 1929), and that turbidity is not a factor in
either the survival of the young or their subse-
quent growth in Lake Eric (Van Oosten 1948).

In fact, the causes underlying annual variations
in the success of natural reproduction are little
understood. Although a knowledge of the fluc-
tuations that occur in the strength of year classes
may contribute to an understanding of changes in
the fishery, a knowledge of the general level of
abundance and of long-period trends in abundance
is more pertinent to the solution of administrative
problems than is information on short-period fluc-
tuations.

The abundance of yellow perch in the early
period of the United States fishery (1885-99) must
have been at a relatively high level, since good
production was maintained in spite of low fishing
intensity and inefficient methods. On the other
hand, the reduced yields of the 1900-1927 period —
one of expanding fishing intensity and increasing
efficiency in fishing methods — indicate a sharp
reduction in the general level of abimdance. The
greatly increased production in 1928-35 must be
considered the result, in part at least, of the
increase in intensity of the fishery for perch that
followed the collapse of the cisco fishery. The
known abundance in 1928 and 1929 of perch of the
big 1926 year class and the virtual removal of the
size limit in Ohio in 1934 undoubtedly contributed
to the large yields in those years. It seems
unlikely, however, that a production of over 14
million pounds could have been reached in 1934,
even without a size limit, unless the population
had reached an enormous size that year. Like-
wise, the yields of more than 9 million pounds in
1931, 1932, and 1935 indicate tremendous abund-
ance. Evidence will be presented later (p. 245)
which shows that normally the perch of a year
class dominate the fall fishery in their third year
and the spring fishery in their fourth year of life.
Thus, two year classes of perch make up the bulk
of the commercial catch each calendar year. On
the basis of that evidence, it may be assumed that
the year classes of 1928 to 1932 or 1933, inclusive,
were of exceptional strength to have been able to
produce the high yields during the period 1931-35.

The statistics (table 1) suggest strongly that the
abundance of yellow perch was reduced greatly
during the years 1936-47. The fishing intensity
may have decreased in United States waters when
some of the operators quit business, but it is
known also that some new outfits started opera-
tions during this period. Increase in size of the
mesh in the Ohio trap nets probably did not

YELLOW PERCH OF LAKE ERIE

211

release enough legal-sized perch to affect materially
Ihe total yield. Since Van Oosten (1932) showed
that trap nets \vith a mesh larger than that em-
ployed in the nets at the present time did not
release perch of 8% inches (present legal size limit)
and larger, the reduction in take in 1936-47 un-
doubtedly was largely the result of a decrease in
abundance of perch rather than a decrease in
fishing intensitj-.

A precise evaluation cannot be made of the
changes in abundance of the yellow perch in Lake
Erie during the period of greatest fluctuations in
yield, because the data are not sufficient. An
appro.ximation of the abundance may be obtained,
however, from the records of the W. D. Bates
Fishery, Rondeau, Ontario, which give the number
of pound nets fished and the catch each year for
the period 1900-1940, and from those of Leonard
Bickley, Sandusky, Ohio, which give the catch by
trap nets of a 1-boat fisherj- during the years 191 1-
3 1 . The records of number of nets fished and total
pounds of fish taken published by the former

Ontario Department of Game and Fisheries also
are of value.

Although there are certain discrepancies among
these three sets of data, they all suggest that the
period 1928-35 was one in which the abundance
of yellow perch in Lake Erie was high, and all
data are consistent in showing that the abundance
declined sharply in 1936 and has remained at a
relatively low level since that time. Bickley's
data, in contrast to those of Bates, suggest a slight
increase in abundance in 1921-27, thus indicating
that the slight rise in production in the Ohio
waters in those years may, in part, reflect abund-
ance.

It must be recognized tliat the j'ellow-perch
fishery in Lake Erie is not in a prosperous con-
dition at the present time. That the fishery has
not collapsed entirely is perhaps a tribute to the
fecundity of the perch. The danger exists in the
absence of a reserve supply, as well as in the low
abundance. The failure of only two successive
year classes would lead to collapse of the fishery.

MATERIALS AND METHODS

Materials for this investigation on the age and
growth of yellow perch were collected at the follow-
ing Lake Erie ports: Port Clinton. Sandusky,
Huron, Vermilion, Lorain, Ashtabula, and Conne-
aut, Ohio; Erie, Pa.; and Dunkirk, N. Y. (See
fig. 2.) Originally a separate analysis was made
of the data for yellow perch from the western,
middle, and eastern sections of the lake; it was
found, however, that a combination of the data
was justifiable. It was found also that the data
for trap nets and pound nets could be combined.

Table 2 shows, for each type of gear, the number
of specimens on which this study has been based.
The 1927-37 materials used in the growth-rate
studies, a total of 3,036 fish, were random samples
of the trap-net and pound-net catches taken during
the latter part of the collectmg period of each year.
Samples from impounding nets were used because
that tj'pe of net is less selective than gill nets, and
because the impounding-net collections covered a
greater period of years. The 1,341 fish taken from
trap nets in the years 1943-48 were used in the
study of ammal fluctuations in growth. The ages
were determined of 430 specimens taken in com-
mercial gill nets during 1927 ami 1928, and of
1,136 fish taken in the j^ears 1943-48. The
1927-28 material consisted of random samples

955513—5:; 2

from shoal nets (228 fish) and from bull nets
(202 fish). The data on age were used to compare
the age composition of the catch in gill nets %vith
that of impounding nets.

All specimens for which length and weight were
recorded (23,158 fish) in 1927-37 were used in the
study of the length-weight relation. The length-
frequency data for the years 1927-37 were based
on 58,665 specimens taken from random samples
only and included those specimens whose ages
were determined, most of those used in the study
of the length-weight relation, and a large number
for which lengths only were obtained. The length
distribution of 1,114 yellow perch taken in 1943-48
by trap nets was used for comparison with the
earlier material.

Investigation of the relation between scale length
and body length was based on the examination of
selected or "key" scales from 600 specimens col-
lected in western Lake Erie as follows: September
to November 1928, 188; May to August, and
November 1929, 79; October 4, 1934, 207; April
1937, 60; and late autumn 1937, 66. The scale
measurements from only 576 of these specimens
could be used, since 24 individuals had lost the
designated scale or had key scales that were re-
generated, injured, or otherwise atypical. The

212

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

si

P

I

YELLOW PERCH OF LAKE ERIE

213

Table 2. — Specimens used in study of Lake Erie yellow
perch and gear employed in taking them

•

Number ot specimens used in study of—

Oear employed and year taken

Age and
growth

Length-
weight
relation

Length
frequency

Caught by Impounding net
during—
1927

481
■918

' 1. 151
222

1,816

3,123

11,216

269

3,224

1928

5,785

1929

11,939

1930

7.118

19,391

1932

133

«131
45
81
157
225
343
490

133
207
131

133

1934

1937

131

1943

1944

81

1945

132

1946 - -

1947

204

297

400

Total

'4,377

16,594

48,835

Caught by shoal gUl net*
during—
1927 - -

84
144

1,659
3,386

1,670

1928

2,754

1929

4,744

1930

1931

1934

1943

129
67
75
204
380
291

1947

1,364

5,045

9,168

during—

69
133

116
665
838

257

1928

681

838

1930

1932

1937

1944 -.-

1946 -

1948 -

Total -

202

1,519

1,776

5,943

23,168

59, 779

1 In addition, 188 selected specimens were used In the key-scale study.
' In addition, 79 selected specimens were used in the key-scale study.
' 207 selected specimens were collected for key-scale study.
' In addition, 126 selected specimens were used in the key-scale study.
i Selected specimens used in the key-scale study and for the determination
of maximum age are not included in the totals.
' Q ill nets 22 meshes deep.
' Oil] nets 100 meshes deep.

600 specimens collected for the key-scale study
were not used for any other purpose, except the
207 collected October 4, 1934, which were em-
ployed as part of the data on the length-weight
relation.

During 1927 and 1928 the lifting cribs of the
trap nets from which samples were taken were
made of 2-inch or 2Ji-inch webbing (stretched

measure as manufactured), except for the vertical
middle third of the backs, where the mesh was
2% inches. From 1929 to 1937 the mesh of the
crib was 2^ inches (stretched measure as manu-
factured) in all parts except the entire back where
the mesh was 2Yi inches. Since 1937 the mesh in
the back of trap nets has been 2% inches, with the
sides made of 2}^-inch mesh. The pound-net
samples (from Erie, Pa.) were from nets with
meshes of 2'){6 inches (stretched measure as manu-
factured). The gill nets, from which the 1927-28
samples were studied, were of 3-inch and SKe-incb
mesh (stretched measure as manufactured). Since
the length frequencies of the perch taken in the
two sizes of mesh showed no significant differences,
the size of mesh was ignored in treating the gUl-
net data. The gill-net data, however, have been
separated on the basis of depth of net because
there was a difference between the length fre-
quencies of perch taken in shoal gill nets and in
bull gill nets. The shoal nets were 22 meshes deep
and the bull nets 100 meshes deep. The meshes
of the shoal nets from which the 1943-48 samples
were taken measured 2% inches.

Except in 1930-31 and 1943-48, lengths were
measured with a flexible steel tape held so as to
foUow the curve of the body from the tip of the
snout to the thickest part of the body, and then
in a straight line approximately parallel to the
long axis of the body. The length records of fish
caught in 1930-31 and 1943-48 were obtained with
a measuring board. The lengths measured on the
board were converted to "tape-line lengths" by
the factor 1.02. Weights were recorded to the
nearest fourth of an ounce except in 1948 when
they were recorded in tenths of ounces. All meas-
urements of length and weight were obtained from
fresh specimens in the field, except those of fish
collected for key-scale study. Of those, the 207
used in the length-weight-relation study were
shipped fresh, packed in ice, to the laboratory,
where they were measured and weighed, and the
rest, all preserved, were measured but not weighed.
Lengths obtained from preserved specimens were
corrected for shrinkage produced by the preserva-
tive; the coiTcction factor was 1.0065.

Scales for age determinations were taken from
the left side of the fisli, below the lateral Une and
beneath the spinous dorsal hn. The}"^ were
mounted on standard glass microscope sHdes in

214

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

the gelatin-glycerin medium recommended by
Van Oosten (1929).

The first examinations of the 1927 and of part
of the 1928 scale collections were made by use of
the projection apparatus described by Van
Oosten (1923). The final examinations and the
measurements of those scales, and all examinations
and the measurements of the remaining scales,
were made by means of the apparatus described
by Van Oosten, Deason, and Jobes (1934) at
magnification X 40.7. The measurements from
the focus to each successive annulus and to the
extreme edge of the scale were made along the
most anterior interradial space. Approximately
5 percent of the scales examined were discarded

because the age could not be determined with
confidence.

Ages are designated in roman numerals corre-
sponding to the number of annuli visible on the
scales except for those fish taken in the early
spring before growth began. An amiulus was
assiuned to be present on the edge of the early-
spring scales. Such an assumption is necessary
to avoid the assignment of one age to fish of a
year class whose scales were without spring
growth and another age to fish of the same year
class collected the same day whose scales had
begmi the current season's growth. Thus fish
assigned to age group I were in or just ready to
begin their second year of life.

DETERMINATION OF AGE AND GROWTH OF LAKE ERIE YELLOW PERCH BY THE

SCALE METHOD

Since the demonstration by Hoffbauer (1898)
that the age of carp could be determined by
examination of their scales, the scales of fish
have been used extensively for the study of growth
rates and age composition of the stocks of many
marine and fresh-water species. Historical sum-
maries of the literature and discussions of the
validity of age determinations from scales and of
growth calculations from scale measurements
already published make it unnecessary to say
more here than that the major part of the evidence,
obtained from a wide range of species, sub-
stantiates the general premise that age can be
determined accurately from scale markings and
that measurements of fields of growth in scales
can be employed for the calculation of lengths
at the end of the dift'erent years of life.

VALIDITY OF THE ANNULUS AS A YEAR MARK

It has been assumed by the several workers
that ages may be determined accurately from
an examination of the scales of the American
yellow perch, since these scales showed clearly
the characteristics that had been used in the
accurate determination of the ages of certain
other species. The data, and observations of the
present study, given in the following paragraphs,
substantiate this assumption.

1. The collections of 1927, 1928, and 1929 were
dominated by fish whose scales showed 1, 2, and
3 annuli, respectively. The corresponding aver-
age total lengths of the age groups were 7.5, 8.3,

and 9.5 inches. (Most of the 1928 collections
were not made as late in the autumn as were the
collections of 1927 and 1929; consequently, the
average length of 8.3 inches does not represent 3
full years of growth.) That the catches of suc-
ceeding years were dominated by progressively
larger individuals which, in accordance with ex-
pectation, were shown by scale readings also to be
progressively older, is strong evidence that on(>
annulus is formed each year and that the scale
markings can be interpreted accurately for at
least the first three years of life.

2. Scales collected on December 7, 1929,
showed no annulus on the edge. Samples obtained
July 1, 1929, April 11 and 13, 1932, and April 29,
1937, showed an aim.ulus forming on the edge of
the scales. On July 11, 1930, the scales showed a
completed annulus a short distance inside the
margin. The outermost annulus was farther from
the scale margin on September 25, 1930, than in
July. These observed variations, especially those
on the relative positions of the annulus within
the scale margin at different times during the
same year (1930), provide evidence that only one
annulus was formed on yellow-perch scales each
year.

3. There was closer agreement between the
calculated and empirical lengths of fish of the
same age as determined from scales than between
those of different ages. This agreement indicates
a constancy in the number of annuli formed each
vear.

YELLOW PERCH OF LAKE ERIE

215

Annuhis formation appears to be completed be-
tween early April (1932 and 1937 collections) and
the middle of July (1929 collection). There is no
evidence from these data to show a relation be-
tween the time of annulus formation and sex,
maturity, or spa^^^ling activity. The annulus on
yellow-perch scales cannot be said to be a spawn-
ing mark despite the approximate coincidence of
spawning and the completion of the annulus
because (1) immature yellow perch form annuli
identical in appearance with those formed by
spawning fish, (2) the stage of sexual maturity-
appears to have no influence on the time of year
the annulus is completed, and (3) the annuli do
not show the typical spa\vning marks observed
in other species of fish.

The most important characteristics of the annuli
on the scales of the Lake Erie yellow perch may
be stated briefly to be the "cutting over" in the
lateral fields resulting from the discontinuity
between scale sculpturing of the successive growth
areas, and the irregular or fragmented appearance
of the last circulus laid down each year. Usually
there is a narrow, clear band between the outer-
most circulus of one growth area and the first
circulus of the next.

False (accessor}') annuli occurred not infre-
quently on the yellow-perch scales but are be-
heved not to have affected the results seriously
since all that were recognized were disregarded.
Those annuli designated as false were character-
ized by a decreased amoimt of "cutting over,"
by less-well-defined discontinuity between the
adjacent fields of growth, and, frequently, by a
position that would have given inconsistent calcu-
lated lengths.

BODY-SCALE RELATION

Few calculated lengths for the American yellow
perch have been published. The earliest, by
Jobes (1933) and Schneberger (1935), were com-
puted by the Dalil-Lea method of direct propor-
tion. This method is based on the assumption
that the ratio of body length to scale length is
constant at all lengths beyond that at which the
first year mark or annulus is formed. The age and
growth of the closely related European perch,
Perca fiumatilis L., have been studied by this
method by several investigators who found that the
lengths calculated by direct proportion usually

were less than the empirical lengths for the early
years of life.

In spite of the wide use of the direct-proportion
method, numerous investigations have shown that
this method frequently failed to give satisfactorily
accurate results since the computed lengths
obtained often did not agree with empirical
lengths. Of the several methods developed to
obtain a closer agreement between calculated and
empirical lengths only that of SegerstrMe (1933)
for the European yellow perch will be mentioned
here, since the calculation of lengths in the present
study was by a modification of his procedure.

Segerstrale determined the average scale lengths
corresponding to different body lengths through an
extensive series of measurements of "key" scales,
or "Normalschuppen," taken from a selected area
of the body. The body-scale relation so deter-
mined, expressed either in tabular form or as a
curve, served as the basis for calculating the
growth histories of individual fish. On purely
theoretical grounds, the method of Segerstr&le is
the best since it assumes no fixed mathematical
relation between body length and scale length, but
rather is based on the detailed examination of the
actual size of scale at different body lengths.
The most serious objection to the use of an
empirically determined relation of body length to
scale length in the calculation of growth histories
is the practical difficulty of obtaining samples with
adequate representation of all lengths of fish.
The distribution by length of a fish population
usually is such that individuals of certain sizes are
difficult or impossible to obtain. Inadequate
representation of these length intervals inevitably
leads to inaccuracies in the calcidated lengths.

The diversity of opinions expressed and of
results obtained by the several investigators deal-
ing with presumably representative collections of
the same and different species leads to the con-
clusion that the relation of body length to scale
length in fishes is not a subject for generalization.
The proper method of calculation must be deter-
mined for the material at hand. Data on the
yellow perch from Lake Erie made possible an
anah-sis, for the first time,- of the relation of body
length to scale length in a population of American
yellow perch.

2 Although circumstances prevented earlier publication of this study, Hile
and Jobes (1941) were able to apply the method developed here to the determi-
nation of the body-scale relation of the yellow perch of Saginaw Bay.

216

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

intervals, and the corresponding average total
lengths in inches, together with the average scale
measurement (at magnification X 40.7), and the
body-scale (L/Sc) ratios of each length and age
group. The L/Sc ratios of the age groups are
the averages for data collected both at the end
of the growing season and at various times
throughout the summer (see p. 211). The data
were originally grouped in 5-mm. length intervals,
but careful examination revealed that condensa-
tion to 10-mm. intervals was justifiable. The
average L/Sc ratios of the age groups indicate that
the relative size of the scale increased during the
first 3 years of life and then decreased slightly
during the fourth. However, a comparison of
the L/Sc ratios of fish in the same length interval
but of different ages revealed that there was no
consistent change in the relative size of scale with
age. Consequently, the differences between the
relative sizes of scales in the different age groups
do not depend directly on age but rather on the
length distribution of the age groups. Com-
parisons between fish in the same age group but
of different average lengths showed that the
L/Sc ratios became relatively smaller (relatively
larger scales) as the fish length approached 4.3
inches (see data for age groups and I) ; remained
reasonably constant over the length range of 4.3
to 9.2 inches (age groups I, II, and III); and then
established another reasonably steady but higher
ratio (relatively smaller scales) over the length
range of 9.2 to 10.9 inches (age groups II and III).

-Body length io scale length ratio (L/Sc) of selected scales from western Lake Erie yellow perch by 10-mm. intervals

(Number of specimens in parentheses)

Only key (selected) scales were used to determine
the relation between size of scale and size of fish.
The scale on the left side of the fish in the third row
below the lateral fine and directly beneath the
sixth spine of the dorsal fin was designated the key
scale. The position of the key scale approximated
the center of the area from which the unselected
scales were obtained for age and growth determina-
tions. The scale occupying the designated posi-
tion on the right side of the specimen was used
when the one on the left side was lacldng or was
regenerated or malformed. Although the collec-
tions for the key-scale study were taken at widely
spaced intervals of time (see p. 211), an analysis of
the data failed to reveal any large or consistent
differences for fish captured in different years or
seasons.' There is no evidence of a seasonal lag
between the growths of body and scale in the Lake
Erie yellow perch. The data also failed to show
any consistent differences in the relative sizes of
scale correlated with sex or stage of maturity.
Therefore, data from all fish have been combined
in this study without regard for the time of capture,
sex, or stage of maturity.

Table 3 shows the average standard length of
the Lake Erie specimens grouped in 10-millimeter

' Tlie scales of group (first year of life) yellow perch caught during late
October and early November 1928 were found to be consistently somewhat
smaller than the scales from fish of the same length and the same year class
that were caught during September 1928 and June 1929. This unusual
phenomenon cannot be explained satisfactorily at present. However, the
differences were so small that the inclusion of fish caught during October and
November did not change greatly the grand average ratio of body length to
scale length (table 3) .

Table 3.-

Standard-length interval

LfSc ratio for age group —

Grand average
LISc ratio

Average stand-
ard length
(mUlimeters)

Average total
length (inches)

Average scale

measurement

(X40.7)

0'

I

II

III

41 to 50 mm

1.97 (40)
1.74 (91)
1.55 (37)
1.41 (7)
1.36 (1)

1.97 (40)
1.74 (94)
1.66 (64)
1.41 (30)
1.33 (26)
1.16 (32)
1.16 (16)
1.19 (6)

1.16 (12)
1.14 (29)

1.13 (31)
= 1.13 (40)

1.14 (48)

1.19 (21)

1. 15 (8)

1.17 (21)
1. 23 (8)

1.20 (34)

1.21 (13)
1.17 (3)

1.24 (576)

47.7
55.5
64.6
74.6
85.2
97.2
104.2
116.5
126.3
136.7
145.1
166.3
165.5
173.9
184.2
196.6
205.9
216.8
223.6
234.0

2.3

2.7
3.1
3.6
4.1
4.6
5.0
5.5
6.0
6.3
6.7
7.2
7.6
8.0
8.6
8.9
9.4
9.9
10.2
10.6

24.2

1.64 (3)
1.67 (27)
1.42 (23)
1.32 (25)
1.16 (32)

1.15 (15)
1.19 (6)

1.16 (11)
1. 14 (26)
1.12 (23)
1.14 (15)
1.16 (11)
1.18 (1)

31.9

61 to 70 mm-- __-

41.4

71 to 80 mm

52.8

81 to 90 mm.

64.3

91 to 100 mm

83 5

101 to 110 mm...

1. 2i (1)

90.1

Ill to 120 mm

98.2

121 to 130 mm

i.n (1)

1.22 (2)
1.08 (6)
1. 12 (22)

1.14 (36)

1.19 (20)

1.15 (8)
1.18 (17)
1.22 (7)

1.20 (24)

1.21 (7)
1.21 (2)

1. 16 (163)

110.2

1.20 (1)
1.22 (2)
1. 13 (2)
1.09 (1)

119 8

141 to 150 mm

128 6

151 to 160 mm

138 3

161 to 170 mm

144 5

171 to 180 mm

146.7

181 to 190 mm

160.2

1.14 (4)
1.35 (1)
1.22 (10)
1.20 (6)
1.08 (1)

1.19 (28)

167.5

201 to 210 mm

166 9

211 to 220 mm

179 9

221 to 230 mm

185 2

231 to 240 mm

200 7

Average

1.74 (176)

1.26 (218)

> First year of life.

» The age was not determined for 1 specimen in this length interval.

YELLOW PERCH OF LAKE ERIE

217

These changes in the LjSc ratio perhaps are shown
more clearly in table 3 and figure 3. It is evident
that the ratio of body length to scale length in the
Lake Erie yellow perch is determined primarily
by the length of the fish.

Figure 3 is a graphic presentation of the average
total lengths and average scale measurements
shown in table 3. The straight line extenduig
upward from a fish length of 4.6 inches represents
the body -scale relation of all fish with total lengths

greater than 4.2 inches, on the assumption that a
single average (1.16) describes the body-scale
ratio satisfactorily for all these fish. The line for
the average fish lengths of 2.3 to 4.6 inches was
drawn freehand. The line determined by the
average LjSc ratio (1.16) fits the data closely for
the fish with average total lengths of 4.6 to 8.9
inches. The scales of those fish with average
lengths of 9.4 inches and more were somewhat,
but not pronouncedly, smaller than would have

<

O

/

/

«

y

/■

'""//

V

/

/

...

b

2

10 15

SCALE X 40 7

Fir.URE 3. — Relation between body length and scale length in yellow perch of Lake Erie.

2 5

218

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

been expected on theoretical grounds. These
rather sHght discrepancies which affected only
three length intervals are not believed to invali-
date the conclusion that the body-scale ratio is
constant beyond the average body length of 4.6
inches. The scales from the fish with average
lengths of less than 4.6 inches were relatively
much smaller than the scales from the larger fish.
It is to be noted particularly that the relative size
of the scale increased rapidly as the average length
of the fish increased from 2.3 to 4.1 inches. The
increase in relative size follows approximately a
straight line but its slope is greater than that of
the line fitted to the data for the larger fish.

The rapid increase in the relative size of the
scale during early life was expected from the
known facts of scale growth. The scales originate
as tiny isolated platelets when the yellow perch
has a total length of approximately 1 inch. The
scale, then, must grow more rapidly than the
body in order to attain the degree of imbrication
characteristic of larger fish.

It is evident from table 3 and figure 3 that a
sharp break in the series of LjSc values and in the
continuity of the curve occurred between the
average lengths of 4.1 and 4.6 inches. A detailed
examination of the LjSc ratios for each millimeter
length indicated that the break occurred at a
length of 4.3 inches. The average ratio of the
4.2-inch individuals was comparatively high (1 .34),
but it fell suddenly to 1.13 in the 4.3-inch fish and
continued at that level in the lai-ger specimens.
It appears, then, that the LjSc ratio actually
assmnes constancy at a fish length of 4.3 inches
rather than at 4.6 and no corrections for dispro-
portionate growth of body and scale are necessaiy
for calcidated values greater than 4.2 inches.
Since the two discontinuous portions of the curve
of figure 3 were based on averages (in order to
obtain a smoother curve) and (for purposes of
correcting computed lengths below 4.3 inches) were
connected at points of average lengths (4.1 and
4.6), any calculated values that fall between these
two averages will be subject to correction. Any
correction of length between 4.2 and 4.6 inches
theoretically is unwarranted. However, as may
be seen from table 4, the corrections for lengths
between these hnaits are small and for all practical
purposes may be ignored.

If the length of the scale were purely a function
of the length of the fish, the body-scale curve for

the smaller individuals would be expected to join
smoothly the straight line that describes the body-
scale relation for the larger ones. The pronounced
discontinuity in the curve suggests that other fac-
tors must be involved. Changes in the relative
size of the head with increase in fish length may
have been a factor. The relative size of the head
was found to decrease progressively with mcrease
in fish length tlu'ough the 71 to 80 mm. interval or
up to the average length of 74.6 mm. (3.6 inches
total length) . Thereafter, variations in the relative
size of the head were small and without any detect-
able trend through the 171 to 180 mm. interval (8.0
inches average total length). Although the pro-
gressive decrease in the relative length of the head
may have contributed to the decrease in the values
of LjSc up to a fish length of 3.8 inches, it is
apparent that these changes did not produce the
observed sudden shift in the body-scale relation
between 4.3 and 4.7 inches.

The possible effect of variations in the number
of scales in linear series on the body-scale ratio also
was investigated. It was foimd that fish with
standard lengths of 81 to 90 mm. (4.1 inches aver-
age total length) averaged 54.9 (51 to 58) scales
in the latei'al line, and that fish with lengths of 91
to 100 mm. (4.6 inches average total length), aver-
aged 55.1 (51 to 62). The small difference (0.2)
in the averages could have had little effect on the
changes in the body-scale ratio. If it is assumed
that this difference could affect the body-scale
ratio, then one would expect the larger fish to have
relatively smaller scales, a conclusion contrary to
the observed facts. It appears that the number
of scales in linear series was not a factor in the
sudden change in the body-scale ratio of the Lake
Erie yellow perch.

Length of fish is the ouIa' factor iii these data
that can be demonstrated to have had an appreci-
able effect on the body-scale ratio. The failure of
the two portions of the curve to join smoothly can-
not be explained satisfactorily as j-et.

CALCULATION OF GROWTH

In the preceding discussion it was indicated that
because of the discontinuity of the LjSc curve
(change m average LjSc ratios) all direct-propor-
tion computations of length less than 4.6 inches
must undergo correction, and because of the con-
stancy in the average ratios no corrections were
needed for lengths of 4.6 inclies or more. The

YELLOW PERCH OF LAKE ERIE

219

direct-proportion method was therefore employed
whenever the calculated lengths exceeded 4.5
inches and the empirical curve was used only for
the smaller lengths. Since the correction for 4.51
inches was less than 0.05 inch, the empirical-
curve method was applied only to lengths of 4.46
inches and less.

In practice, all lengths were computed b)' direct
proportion, and corrected lengths corresponding to
calculated lengths 4.46 inches and less were read
directly from table 4, which was prepared with the
assistance of the empirical body-scale curve (fig.
3). The data for this curve were plotted originally
on 1-nim. cross-section paper and the amount of
each correction was read directly from this graph.
The amomit of correction required for each direct-
proportion calculated length is the vertical dis-
tance between the extended straight hne repre-
senting the body-scale ratio of fish with total
lengths of 4.6 inches and more and the empirical
line representing the ratio for the shorter fish.
The procedure for obtaining the correction for a
du-ect-proportion calculated length of 3.25 inches
is illustrated in figui-e 3. Line AB is drawn hori-
zontally from i=3.25 to B on the straight line
representing the body-scale ratio of fish with total
lengths of 4.6 inches and more. Line CD is a

Table 4. — Calculated lengths (inches) of Lake Erie yellow

perch

[Total-Iengtb conversion of standard length in millimeters]

Direct-proportion
calculated length

Corrected cal-
culated length

Dlrect-proiwrtion
calculated length

Corrected cal-
culated length

1.72

2.63
2.63
2.68
2.72
2.77
2.82
2.87
2.87
2.92
2.96
3.01
3.06
3.U
3.15
3.15
3.20
3.25
3.30
3.30
3.35
3.39
3.39
3.44
3.49
3.54
3.54
3.59
3.63
3.68
3.68

3.15

3.73

1.77

3.20

3.78

1.82

3.25

3.82

1.86

3.30

3.82

1.91

3.35

3.82

1.9«

3.39

3.85

2.01

3.44

3.85

2.06

3.49

3.90

2.10

3.54

3.95

2.15

3.58

3.95

2.20

3.63

4.00

2.25

3.68

4.04

2.29 . .

3.73

4.04

2.34

3.78 - . .

4.09

2.39 .

3.82

4.09

2.44

3.84 -

4.14

2.49

3.87

4.14

2.53

3.90

4.18

2.58

3.95

4.18

2.62

4.00

4.23

2.68

4.04 -

4.28

2.72

4.09

4.28

2.77

4.14

4.28

2.82

4.18 -

4.32

2.87

4.23

4.32

2.92

4.28

4.37

2.96

4.32

4.42

3.01

4.37

4.42

3.06

4.42

4.46

3.11

4.46

4.51

perpendicular that passes thi'ough B from the
scale axis to D on the Une representing the bod}'-
scale ratio of the smaller fish. The correction is
the distance between points B and D. In the
present stud}^ only the first-year lengths fell
within the range that requu'ed correction.

CALCULATED GROWTH HISTORIES OF THE AGE GROUPS

The average weight at capture and the calculated
lengths of yellow perch taken from impounding
nets in the years 1927-37 are shown by sex and
age gi'oup in table 5. Combination of the data
for the several years was possible because the
corresponding averages varied but little from
year to year and the trends in discrepancies
between lengths computed from fish of different
ages were the same in each of the year classes.
The more rapid growth of the females in all years
of hfe except the second was evident for each year
as well as for the combined years.

The corrected calculated lengths at the end of
the first year of life are seen to be 0.6 inch greater
than those obtained by direct proportion for all
age groups of both sexes except group I where the
difference was 0.4. The smaller amoxint of cor-
rection for age-group-I fish is to be expected since
they were the larger individuals of their year class
and hence their body-scale ratio deviated less

955513—52 3

from the straight-hne relation requu'ed for direct-
proportion computations. In general, the same
remarks may be made regarding the data for males,
females, and all fish. Without exception the cal-
culated first-year lengths of age-group-I fish were
greater than those computed from older fish.
The calculated lengths of fish older than age group
I revealed a slight tendency for the first-j'ear
length to decrease as the fish became older. The
discrepancies between the calculated first-year
lengths of fish older than group I were small.
Comparisons of the calculated lengths for all years
of life after the fu-st revealed not only that there
was a definite tendency for the lengths to decrease
as the fish became older but also that the dis-
crepancies each year were larger than in the first
j-^ear of hfe. It is to be noted also that, with the
exception of group-II fish, the length at capture
in the late fall was greater than the corresponding
lengths computed from older fish.

220

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Table 5. — Average weights and calculated lengths of Lake Erie yellow perch taken in impounding nets in late fall, 1927-37

combined

[Number of specimens in parentlieses]

Age group

Average
weight at
capture
(ounces)

Calculated length ' (inches) at end of year—

Uncorrected Corrected

Male:

Age group I...
Age group II--
Age group Ill-
Age group IV..

3.15
4.25
5.54
6.15

Average'

Annual increment -

Female:

Age group I.--
Age group II--
Age group III..
Age group IV..
Age group V...

2.96
4.66
6.57
7.40
8.50

Average'

Aimual increment-.

All fish: 1

Age group I---
Age group II-.
Age group III.
Age group IV..
Age group V...

3.02
4.38
5.99
6.86
8.60

Average'

Annual increment.

3. 6 (266)

3. (532)

3. 1 (397)
2. 9 (45)

3.0(974)
3.0

3. 5 (37)
3. 1 (490)
3. 2 (355)
2. 9 (55)
2. 9 (5)

3. 1 (905)
3.1

3. 6 (392)
3. 1 (1, 636)

3. (895)
2. 8 (108)
2. 9 (5)

3. 1 (2, 644)
3.1

4. (266)

3. 6 (532)

3. 7 (397)
3. 5 (45)

3. 6 (974)
3.6

3. 9 (37)

3. 7 (490)

3. 8 (355)
3. 5 (65)
3. 6 (5)

3. 7 (905)
3.7

4. (392)
3. 7 (1, 636)
3. 6 (896)
3. 5 (108)
3. 5 (5)

3. 7 (2, 644)
3.7

2 7. 5 (266)
6. 7 (632)
6. 5 (397)
6. 7 (45)

6.6(974)
3.0

7. 2 (36)
6. 9 (490)
6. 7 (355)

5. 9 (65)

6. (6)

6. 7 (905)
3.0

7.4 (371)
6.8 (1.636)
6. 6 (895)
6.8 (108)
6.0(5)

6.7(2,644)
3.0

8. 4 (394)
8.4 (397)

7. 7 (45)

8. 4 (836)
1.8

9. 3 (209)
8. 9 (46)

9. 4 (254)
1.0

9. 6 (23)

10. 1 (23)

.7

8. 7 (310)
8. 7 (355)

7, 9 (55)
7.9(6)

8. 6 (725)
1.9

9.9 (192)
9. 3 (55)
9. 1 (6)

9.8 (252)
1.2

10. 2 (28)
10. (5)

10. 7 (33)
.9

10.6 (4)

11.3(4)
.6

8. 5 (750)

8. 5 (895)

7. 9 (108)

7. 9 (5)

8. 5 (1, 768)
1.8

9. 5 (409)
9. 1 (108)
9. 1 (5)

9. 6 (622)
1.0

10.0 (61)
10. (6)

10. 4 (56)
.9

10. 6 (4)

11.0 (4)
.6

• The calculated lengths are based on all flsh without regard for time of
capture and usually include more specimens than used to determine the
length at capture.

> The last length shown for each age group is the length at capture late in
the fall.

In fish older than age group I the discrepancies
just described differ from "Lee's phenomenon of
apparent decrease in growth rate," as most com-
monly encountered, in that the wider disagree-
ments occurred among the computed lengths for
the later rather than the earlier years of life. It
seems probable that the factors that produced the
discrepancies in calculated lengths of the Lake
Erie perch began to be effective after the first year
of hfe had been passed.

Since an intensive study of the body-scale rela-
tion of the Lake Erie yellow perch has eliminated
the possibility of large errors in computed lengths

' Age group I is not included because of selected size. Beyond the third
year of life the average lengths were determined by successive addition of
the average aimual increments of the age groups for those years.

* Includes fish for which the sex was not determined.

resulting from the method of calculation, the ob-
served discrepancies in the calculated lengths must
be considered real rather than apparent. In other
words, the older fish in the samples actually grew
more slowly than the younger ones. The demon-
stration that the discrepancies in computed growth
were real, however, does not justify the conclusion
that the data are exactly descriptive of the growth
in the population from which the samples were
taken. Consideration must be given to the possi-
bility that the samples were not representative of
the population as a whole.

DISCREPANCIES IN THE CALCULATED GROWTH HISTORIES OF DIFFERENT

AGE GROUPS

Two explanations of the discrepancies in com-
puted growth can be offered. It may be held that
the samples were not representative of the popula-
tion in the lake, and that data based on fuUy ade-
quate material would not have shown a decline in
the growth rate with an increase in age. Or it may
be held that the samples were satisfactorily repre-
sentative but that certain factors tended to bring
about the gradual elimination of the more rapidly

growing individuals from the yeUow-perch popula-
tion, and that the recorded data therefore represent
a valid description of the growth of the Lake Erie

perch.

SELECTION BY GEAR

The selective action of impounding nets in tak-
ing samples depends on the escape of small fish
through the meshes. A rough approximation of the
maximum size of escape may be obtained by deter-

YELLOW PERCH OF LAKE ERIE

221

mining the length of fish with a girth equal to the
circumference of the largest meshes found in the
lifting pot of the nets. Since the largest meshes of
the impounding nets from which the yellow-perch
samples were taken were approximately 2}: inches
(stretched measm-e), no fish with a girth in excess
of about 5 inches should be expected to escape from
the net. Forty-two perch with an average girth of
5 inches (range, 4.72 to 5.28 inches) had an average
total length of 7.9 inches.

Examination of the length-frequency distribu-
tions of the age groups (table 19) shows that only
the larger of group I were retained because they
were too large to escape. About one-fourth of the
yellow perch in age group II were as short as the
theoretical maximum size of escape; only a few of
the group-Ill fish and none in age groups IV and V
were shorter than 7.9 inches.

It is not possible to make precise estimates of the
extent to which the reliability of the samples of the
different age groups was affected by the selective
action of the gear. However, group-I samples were
unquestionably composed of individuals with the
most rapid growth. Group-II samples were
affected much less severely. Beyond age group II,
gear selection probably had no significant effect on
the reliability of the samples. It may be concluded,
then, that inadequate sampling traceable to gear
selectivity was an important factor in the dis-
crepancies between the lengths calculated from
group-I yellow perch and from older fish, and was
a contributing factor in discrepancies between the
lengths calculated from group II and from older
fish. Discrepancies among age groups older than
group II cannot be attributed to the selective
action of the nets.

The selective action of the impounding nets
serves also as the basis for the differential destruc-
tion, correlated with growth rate, that brings about
an exaggeration of the discrepancies between the
calculated growth histories of yellow perch of
different ages. Capture in a commercial net ex-
poses illegal-sized perch * to a serious risk of de-
struction in the fishery since a significant propor-
tion ° of the undersized yellow perch are dead when
the nets are lifted. With a fishery as intensive as

' Since the legal siie for yellow perch (8H inches total length) Is well above
the marimum length of escape, the question of differential destruction de-
pendent on gear selectivity concerns only the undersized flsh.

' Dr. John Van Ooston, U. S. Fish and Wildlife Service, found that approxi-
mately 14 percent of the undersized yellow perch were dead in Lake Erie trap
nets at the time of lifting.

that in Lake Erie a single individual may be ex-
posed to destruction repeatedly. Consequently,
a severe mortality of the faster-growing yellow
perch of the younger age groups, especiallj' age
group I, is certain to occur. It appears, then, that
perch of the same year class captured at older ages
show relatively slow growth not only because the
samples of the younger age groups were composed
of the faster-growing fish but also because some of
these same fast growers were eliminated from the
stock as young fish.

SEGREGATION CORRELATED WITH SEXUAL
MATURITY

Any segregation of the yellow-perch population
according to maturity would be in effect a segre-
gation according to size also, since the proportion
of mature individuals increased rapidly mth in-
crease La length (table 36), and it was the larger
fish in the j'ounger age groups that were mature.
It will be shown later that the only evidence of a
segregation of yellow perch according to maturity
was found during the spawTiing season when the
samples consisted almost entirely of mature fish —
97 percent of the yellow perch in samples taken
April 11 and 13, 1932, were mature.

A comparison of the percentage of mature radi-
viduals at different lengths (table 36) with the
length-frequency distribution of the age groups
(table 19) provides an indication of the extent to
which segregation on the basis of maturity may
affect the samples of each age. It is seen in table
36 that a majority of the males reached maturity
at 6)2 inches but that most of the females were not
mature until thej' had passed 8)2 inches. It is
apparent from table 19 that of the males only
group I would be affected by a segregation on the
basis of maturity. Such segregation, however,
would practically eliminate the group-I females,
seriously affect those in age group II, and to a
lesser degree disturb age group III. Because the
data in tables 19 and 36 were largely from fish
taken in the fall, the remarks concerning each age
group may be expected to apply equally well to the
next-older group in the next spawning season,
since little if any intervening growth would occur.
Thus, in the spawning season a segregation on the
basis of sexual maturity would affect some of the
males and practically all of the females in group II,
a few of the males and many of the females in group
III, and almost none of the fish in group 1\ and

222

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

older groups. The April 11 and 13, 1932, samples
seem to bear out this expectation as there were -no
females in age group II but they accounted for 14.3
and 39.4 percent, respectively, of all fish in age
groups III and IV. Although other factors no
doubt affected the sex ratio in the April 1932
samples (see section on sex ratio, p. 260), segrega-
tion on the basis of maturity must have played an
important part.

Inadequate sampling because of segregation
according to maturity is of little unportance in the
present study since only one collection employed
in the study of age and growth was taken from the
spawning rim (1932 collection). In this material
the reliability of the data for the group-Ill
females only is open to question.

Since maturity and length are closely related, it
is possible that segregation according to maturity
may be a source of destruction in the spawning-
run fishery of fish with more rapid growth. The
effects of this higher mortality of fish with rapid
growth on comparisons of the growth histories of
fish of different ages are similar to the effects of
the selective destruction of rapidly growing fish
associated with gear selectivity (p. 221).

SELECTIVE DESTRUCTION ACCORDING TO THE
LEGAL SIZE LIMIT

The imposition of a minimum legal size limit
does much to reduce the effect of selection by gear
through the protection of the faster-growing but
still illegal-sized individuals, but at the same time
adherence to a legal size limit produces a similar
selective effect of its own. As the fish reach the
minimum legal size limit they are subject to re-
moval by the commercial fishery. Consequently,
the faster-growing individuals are exposed to this

source of destruction earlier in life than are those
of slower gi'owth. In a heavily exploited fishery,
successive samples of a year class, then, may be
composed of fish with successively slower growth
as a consequence of continued sorting according
to size.

The manner and extent to which the selective
destruction of yellow perch accordmg to legal size
Umit may give rise to discrepancies between the
calculated growth histories of different age groups
are brought out by the data of table 6. Effects of
the elimination of different percentages of legal-
sized fish ° on the determination of the growth
histories of three age groups also are shown.
From the data of table 6 it is obvious that the con-
tinued removal of legal-sized yellow perch in the
commercial fishery will bring about a decrease in
the calculated growth rates of an age group.
The first-year computed lengths were affected the
least. The exclusion of all legal-sized fish reduced
the fh-st-year length by only 0.1 inch in the 1928
group II and 0.2 inch in the 1929 group II but
brought about a 0.2-inch increase in the first-year
length of the 1928 group III. On the other hand,
the effect of the elimination of legal-sized yellow
perch on the determination of the calculated
lengths at the end of the second and third years of
Ufe was pronoimced. The decreases in the second-
year length with aU legal-sized fish excluded were
as high as 0.7 inch (1929 group II); the decreases
in the thu'd-year length were as high as 0.9 inch
(1928 group III). When lesser percentages of

" A size limit of 8M inches was employed in the separation of legal and
undersized fish in all three age groups although a 9-inch limit was actually
in effect in 1928. Since most of the 1928 samples were taken in the summer
before completion of the season's growth and most of the 1929 samples were
taken in the fall, presumably after completion of the season's growth, it was
believed that the data for all age groups would be made more nearly com-
parable by the use of a single size limit.

Table 6. — Effect of excluding legal-sized fish in determining growth histories of Lake Erie yellow perch

[Legal size: BH inches]

1928 group II

1929 group II

1928 group III

Proportion of legal-sized fish excluded

.Vumber
of speci-
mens

Calculated length
at end of year of
life—

Number
of speci-
mens

Calculated length at end of
year of life —

Number
of speci-
mens

Calculated length at end of
year of life—

1

2

1

2

3.

1

2

3

832

750
669
588
506

3.8
3.8
3.8
3.7
3.7

7.1
7.0
7.0
6.9
6.7

372
323
274
225
176

3.5
3.6
3.5
3.4
3.3

6.8

6.7
6.6
6.4
6.1

8.6
8.4
8.3
8.1
7.9

70
57
44
31
18

3.7
3.7
3.8
3.8
3.9

6.2
6.2
6.1
6.1
5.8

8.2

26 percent

8. 1

8.0

75 percent

7.9

100 percent

7.3

1 Length at capture in fall (see footnote 0, above).

YELLOW PERCH OF LAKE ERIE

223

legal-sized fish were excluded the reductions in the
calculated lengths were smaller.

It should be mentioned that the data of table
6 are based on the elimination of legal-sized fish
in a single group of samples whereas the removal
of legal-sized individuals by the fishery is gradual
and is also progressive in the sense that continued
growth during the fisiiing season brings more and
more individuals to the legal size. The data
serve, nevertheless, to illustrate the type of
selective destruction that must occur in the heavily
exploited yellow-perch fishery.

Comparisons of the growth data of table 6 with
those of table 5, reveal that the discrepancies pro-
duced by the elimination of legal-sized fish from
an age group resembled closely the discrepancies
that actually occurred between the growth histories
of different age groups. It is particularly striking
that in both table 6 and table 5, the greatest dis-
agreements among the calculated lengths of fish
older than age group I occurred beyond the first
year of life. It must be considered probable that
selective destruction based on sorting according to
the legal size limit was an important contributing
factor in the observed discrepancies in the calcu-
lated lengths of the different age groups of Lake
Erie yellow perch.

OTHER CAUSES

Differential natural mortality connected with rate
oj growth. — The widely observed association of
slower growth with the attainment of greater age
in poildlothermic animals which was also found
by Hile (1936) in the ciscoes of Silver Lake, Wis.,

may have been a possible factor in the discrep-
ancies in the calculated growth histories of the
Lake Erie yellow perch. The effects of such a
differential natural mortality among the Lake Erie
perch, however, would be obscured by the more
unportant soin-ces of differential destruction by
the fishery.

Annual fluctuations in growth rate. — The dis-
crepancies in calculated growth cannot be traced
to annual differences in growth rate since the dis-
agreements occurred between different age groups
of the same year class.

Formation of more than one annulus per year. —
The vaHdity of the use of the annulus on the Lake
Erie yellow-perch scale as a true year mark has
been established. Although accessory checks are
not infrequent, the scales of those fish concerning
whose age there was doubt were discarded. It
does not appear reasonable, therefore, to assume
that the number of errors in the determination of
age was sufficiently great to account for the ob-
served discrepancies in the calculated growth of
different age groups.

Contraction and resorption of the scale. — Van
Oosten (1929) pointed out that the natm-e of the
structure of scales makes wholly unacceptable
the assmnption that a contraction of scales occurs.
The examination of thousands of yellow-perch
scales faUed to yield any indication of resorption
that would effect the calculation of growth. The
lunited amount of resorption or erosion observed
in the lateral fields of the scales of some old fish
did not affect the measurements along the antero-
posterior axis of the scales.

GENERAL GROWTH CURVES

GROWTH IN LENGTH

It is not possible to determine a growth cmwe
for the Lake Erie yellow perch that is general in
the sense that it describes the growth of an indi-
vidual typical of the population as a whole. The
preceding discussions have brought out clearly that
in general the older fish had a slower rate of growth
than the j'ounger. Consequently, the combina-
tion of the data of several age groups to determine
a general growth ciu-ve involves the lumping to-
gether of heterogeneous growth material. The
resulting curve is descriptive of the samples rather
than of a typical individual. These limitations to
the significance of the data should be kept in mind

in the examination of the information on general
growth contained in table 7.

The average lengths listed in table 7 have been
taken from table 5 and are based on the combina-
tion of all age groups except group I, which was
omitted as nonrepresentative by reason of gear
selection (see p. 221). The lengths of fish taken
in the fall (presumably at the end of the growing
season) were combined with the corresponding cal-
culated lengths. Beyond the third j^car of life
the average lengths of the different age groups
were determined by successive additions of the
average annual increments of growth. This pro-
cedure brings about a natural smoothing of the
general growth curve for the later years of life.

224

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Table 7. — Average calculated length, by age, of Lake Erie
yellow perch taken by impounding nets

Year of life

Males;

1 year.

2 year.

3 year.

4 year.

5 year.

6 year.

Females:

1 year.

2 year.

3 year.

4 year.
6 year.
6 year.

All fish:

1 year.

2 year.

3 year.

4 year.

5 year.

6 year.

Number

Incre-

of
speci-

Total
length

ment
in

Increase

mens

length

Inches

Inches

Percent

974
974

3.6
6.6

3.6
3.0

83.3

836

8.4

1.8

27.3

264

9.4

1.0

11.9

23

10.1

.7

7.4

905
906

3.7
6.7

3.7
3.0

81.1

726

8.6

1.9

28.4

252

9.8

1 2

14.0

33

10.7

.9

9.2

4

11.3

.6

6.6

2,644
2,644

3.7
6.7

3.7
3.0

81.1

1,758

8.5

1.8

26.9

622

9.5

1.0

11.8

66

10.4

.9

9.5

4

11.0

.6

5.8

Standard
length

Milli-
meters

76
143
181
203
220

77
146
187
216
234
248

77
146
184
208
228
242

The use of the average annual increments caused
the lengths of the fish in the later years of life to
be higher than the corresponding average calcu-
lated lengths as determined from the individual
age gi'oups (table 5). For example, as derived
from the general growth cm-ve, the length of the
females at the end of the fifth year was 10.7 inches
as compared to the values of 10.2 (length at time
of capture in the autumn) and 10 inches as deter-
mined from age-gi-oups IV and V, respectively.
Similarly, this length was 10.1 inches as derived
from the growth curve of the males but was only
9.6 inches at time of captm-e in the autumn. Dis-
crepancies occurred also in the lengths at the end
of the fourth and sixth years of life. Although
the successive additions of the average annual
growth increments, to determine the general
growth curve in the later years, introduce dis-
crepancies, they cannot be held with certainty to
represent errors in the general growth curve. On
the contrary, the use of the average annual
increments may tend to offset the distorting
effects of the differential destruction of the more
rapidly growing individuals; hence the seemingly
greater lengths of the general growth curve may
approximate the true typical growth of the Lake
Erie yeUow perch more closely than a cm-ve based
entirely on grand-average calculated lengths.

Figure 4 is a graphic presentation of the data of
table 7 on length at the end of each year of life
and the annual growth increment. At the end of

the first year of life the females were slightly larger
(0.1 inch) than the males, and they maintained this
advantage in length during the second year. Be-
gimiing in the third year the females increased in
length progressively faster than males of the same
age until at the end of the fifth year they were 0.6
inch longer.

Of particular interest is the fact that the
minimum legal size of 8)^ inches, effective in the
States of Michigan and Ohio, was reached at the
end of the thu-d year by all fish (sexes combined).
It may be seen also (table 5) that the average
length of the males captured late in the faU at
the end of their third year was only slightly less
(8.4 inches) and that of the females only a little
more (8.7 inches) than the legal minimum. The
maxim lun length of yellow perch examined in Lake
Erie was 13.9 inches total length, sex not deter-
mined. The longest male was 11.3 inches and
the longest female 12.9.

No physiological explanation can be offered for
the difference in the growth of the sexes. It is
rather certain, however, that the earlier attain-
ment of sexual maturity by the males was not the
primary cause of their poorer growth. The
females enjoyed the gi-eatest actual and relative ad-
vantage in growth in the fourth year of life (fe-
males 1.2 inches, males 1 inch). Yet at that size
86.1 percent of the females and 98.6 percent of the
males were matm-e (see table 36). If the poor
growth of the males was the result of their early
attainment of matiu-ity, the greatest advantage in
the growth of the females would be expected to
occur in the second year of life when 57.8 percent
of the males and none of the females were mature.

In spite of the differences in the growth of the
sexes, the same general description of the course
of growth applies to the cm-ves for the females,
males, and the sexes combined. The most rapid
growth in length took place in the first year of life,
after which the annual increments decreased
continuously'.

GROWTH IN WEIGHT

The average weights of the age groups of yellow
perch taken late each fall (table 5) bring out clearly
that the females were heavier at each age than
the males with the exception of those fish assigned
to age group II in which the males also were the
longer. The best-represented age group (II),
which characteristically dominates the late-season

YELLOW PERCH OF LAKE ERIE

225

YEAR OF LIFE

Figure 4. — General growth curves showing average length and average annual increments in length
of Lake Erie yellow perch at end of each year of life.

catches by trap nets, had an average weight of
just over 4 ounces. The only group with an
average weight of over 8 ounces (V) was repre-
sented by only four fish in the late fall samples
and, therefore, the reliability of the average is
open to question. Although there was consider-
able annual variation, the values in table 5 are
believed to represent rather well the average
weights of yellow perch taken by trap nets from
Lake Erie during the later season.

The average weights of the age groups captured
late in the autumn differed considerably from the

corresponding calculated weights (tables 5 and 8).
The empirical weights were greater for the younger
fish and smaller for the older individuals. Net
selectivity, whereby only the heavier of the shorter
fish were retained, no doubt accounted for the
greater empirical weights of the younger fish.
Perhaps the decrease in condition during October
and November (p. 255) was enough to bring about
the discrepancies noted among the older ages.

In order to have strictly comparable data for
general growth in length and in weight, the equa-
tion for the length-weight relation of the Lake

226

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

ot

FEMALE

— -/■

MALE

J

/

/

/

/

f

/

/

/ y

- — —

/

/ y
/ X

//
//
// ^ -

2 5

2

5

3

O F

FinuRE 5.-

-General growth curves showing average calculated weight at end of each year of life and average annual
increase in weight of Lake Erie yellow perch according to sex.

YELLOW PERCH OF LAKE ERIE

227

Table 8. — Average calculated weight, by age, of Lake Erie
yellow perch

(Collections of all years combined]

Year of life

Males:

1 year..

2 years..

3 year...

4 year..

5 year..,

6 year..
Females:

1 year...

2 year..

3 year...

4 year..

5 year..

6 year..
All fish:

1 year..

2 year..

3 year..

4 year..

5 year..

6 year..

Weight

Qrams

8

66

113

160

204

59
125
190
246
303

58
119
172
224

279

Ounces

0.28
1.98
3.99
5.64
7.20

.32

2.08
4.41
6.70
8.68
10.69

.32
2.05
4.20
6.07
7.90
9.84

Increment
in weight

Ouncei
0.28

1.70
2.01
1.65
1.66

.32
1.76
2.33
2.29
1.98
2.01

.32
1.73
2.16
1.87
1.83
1.94

Increase

607.1
101.5
41.4
27.7

650.0
112.0
61.9
29.6
23.2

640.6
104.9
44.5
30.1
24.6

Erie perch (see p. 252) has been employed to com-
pute weights corresponding to the grand-average
lengths of table 7. These calculated weights are
table 8 which shows also the annual

given in

increments and percents of increase in weight.
The data on general growth in weight are pre-
sented graphically in figure 5.

The calculated weights of the females exceeded
those of the males in every year of life. The
advantage of the females increased regularly from
0.04 ounce at the end of the first year of fife to
1.48 ounces at the end of the fifth. The greatest
advantage in the growth of the females occurred
in the fourth year of life when the increment was
2.29 ounces as compared to 1.65 for the males.

For each sex and for the sexes combined the
annual percent increase in weight was greatest
in the second year and decreased continuously in
the later years. The greatest actual increase in
weight occurred in the third year of life. At the
end of the third year, when the Lake Erie yellow
perch attained the legal length, 8^ inches, the
weight (4.2 ounces) was less than half that at the
end of the sixth year (9.8 ounces). The heaviest
male weighed 12)4 ounces and the heaviest female
(a gravid specimen) weighed 19% ounces.

GROWTH OF YELLOW PERCH IN LAKE ERIE COMPARED WITH THAT IN OTHER

WATERS

Comparison of the growth of yellow perch hi
Lake Erie with that in other waters will be based
on data from the major centers of commercial
production of the species. With reference to other
waters, it is sufficient to say that the numerous
published average lengths of the age groups show
tremendous variation in the size of fish of the same
age. There appears to be no correlation between
geographical location of the lakes and the rate of
growth of perch.

Table 9 gives the average calculated total length
of yellow perch at the end of each year of life as
determined in the present study; ' by Hile and
Jobes for Saginaw Bay (1941) and for the Wis-
consin waters of Green Bay and northwestern
Lake Michigan (1942); and by Carlander (1942)
for the Mimiesota waters of Lake of the Woods.
The data are presented graphically in figure 6.
The total lengths shoA^ii were determined where

' Data on the Lake Erie yellow perch published by Harkness (1922) are
not Included in the table because of differences In criteria for recognizing
aimuli, and his estimated lengths were not computed with reference to the
end of years of life. Study of these scales, which he kindly sent to me, failed
to reveal any pronounced differences In the rates of growth of yellow perch
collected by him in 1920 and of those collected In 1927 and used in the present
study.

necessary from standard lengths in millimeters by
use of the appropriate conversion factors. Calcu-
lated lengths at the end of each year of life are
used rather than length of the age groups at
capture to eliminate discrepancies caused by differ-
ences in the time of capture.

With the single exception of the first year when
the growth from Lake of the Woods was the
greatest (3.9 inches), the yellow perch were
larger in Lake Erie and Saginaw Bay than in the
other three areas. The Lake Erie yellow perch
were larger than those from Saginaw Bay in the
first 3 years of life. In the fourth year they aver-
aged the same, but thereafter the Saginaw Bay

Table 9. — Comparison of average calculated total lengths of
yellow perch from several localities

[Data for sexes combined)

Locality

Average calculated length (In inches) at end
of year—

1

2

3

4

5

6

7

8

9

10

11

3.7
3.0
2.8

2.8
3.9

6.7
6.3
4.C

4.6
6.4

8.6
8.0
6.3

6.0
6.9

9.6
9.6
7.9

7.1
8.1

10.4
10.7
9.0

8.5
9.2

11.0
12.0
10.2

9.7
10.6

Saginaw Bay

Qreen Bay

Northwestern Lake

12.8
11.2

12.1

13.9

:::;

Lake of the Woods

11.8

12.9

14.1

15.2

19.6

955513— 52-

228 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

I S

10

1 2

YEAR OF LIFE

Figure 6. — Average calculated total length in inches at end of each year of life of yellow perch from diflferent waters of

the Great Lakes and Lake of the Woods. Sexes combined.

YELLOW PERCH OF LAKE ERIE

229

fish averaged the larger. There is a striking
similarity in the growth curves of the other three
populations (fig. 6). The yellow perch from Lake
of the Woods averaged about 1 inch longer than
those from Green Bay and northwestern Lake
Michigan at the end of the first year, and after
this year the individuals from northwestern Lake
Michigan averaged somewhat shorter than those
from the other two areas.

Although each of these growth rates compares
favorably with those from other waters, slow

growth does occur in the Great Lakes. Van
Oosten (1944) reported a sample of yellow perch
taken from Presque Isle Bay (Lake Erie) that
averaged only 6.7 inches total length as age-group-
IV fish. Apparently these slow-growing fish do
not frequent Lake Erie proper as none was found
among the thousands examined in the course of
the present study. The largest yellow perch taken
from Lake Ontario by Greeley (1940) had a total
length of just more than 6.5 inches in its fifth
summer of life.

GROWTH COMPENSATION

Two types of relation between early size and
subsequent growth have been observed: (1) That
in which the individuals with greater growth in the
first year retain or add to that advantage in later
growth; and (2) that in which the individuals with
greater growth in the first year grow relatively
more slowly each subsequent year so that a reduc-
tion in range of size occurs. This latter relation
is known as growth compensation. No attempt
will be made to review the literature on the subject,
but it may be stated that the phenomenon of
growth compensation has been observed in so
many species of fish, both marine and fresh-water,
that its occurrence may be considered general.

Age groups II and III of the 1929 collection,
both of which contained large numbers of speci-
mens, have been selected for a study of the rela-
tion between the first-year length and the later
growth in length of the Lake Erie yellow perch.
The data have been restricted further to those
fish collected late in the autumn, when it could be
assumed that the year's growth was complete.
Table 10 shows the growth histories of the dif-
ferent yearling-size classes (sexes separately) of
each of these age groups.

The first-year difference of 0.99 inch between
the average lengths of the largest and smallest
group-II males was increased to 1.38 inches in the
second year. The maximum difference was re-
duced by compensatory growth in the third year
to 1.05 inches, but nevertheless remained above
the original difference. In the group-II females
the original 0.94-inch advantage of the largest
yearlings over the smallest was increased sfightly
to 0.97 inch in the second year. The maximum
difference was reduced by compensatory growth
in the third year to only 0.68 inch.

Table 10. — Relation between calculated length of Lake Erie
yellow perch at end of first year and growth in subsequent
years, based on 1929 collections of age groups II and III

Calculated length at
end of first year of

Num-
ber of

speci-
mens

Length (Inches) at
end of year—

Increment (Inches)
for year—

life

1

2

3

4

1

2

3

4

Age group II:
Males:
3.35 Inches and
under . ..

59

77

29

3.16
3.58

4.14
.99

3.16
3.68

4.09
.94

3.11
3.58

4.09
.98

3.20
3.63

4.18
.98

6.24
6,88

7.62
1.38

6.28
6.88

7.25
.07

5.60
6.42

7.21
1.71

5.97
6.38

7.88
1.61

8.22
8.55

9.27
1.05

8.27
8.63

8.95
.68

7.48
8.27

8.81
1.33

7.99
8.60

9.32
1.33

3.16
3.68

4.14

3.09
3.30

2.68

1.98
1.67

1.65

3.3fi to 3.82 Inches.

3.83 Inches and

over -

Maximum dU-

Females:
3.36 Inches and

49
64

27

40
68

70

3.16
3.58

4.09

3.13
3.30

3.16

1.99
1.75

1.70

3.36 to 3.82 inches-

3.83 inches and

over _

Maximum dif-

Age group III:
Males:

3.35 Inches and
under...

3.36 to 3.82 Inches.
3.83 Inches and

8.86
9.27

9.73

.87

9.46
9.73

10.33
.87

3.11
3.58

4.09

3.20
3.63

4.18

2.39
2.84

3.12

2.77
2.76

3.40

1.98
1.85

1.60

2.02
2.12

1.74

1.38
1.00

.92

Maximum dif-
ference

Females:

3.35 inches and
under

3.36 to 3.82 Inches.
3.83 inches and

over .......

40
57

58

1.47
1.23

1.01

Maximum dif-

The relation between first-year length and later
growth in length of both sexes of age group III
resembled that of the group-II males. The
largest yearlings of both the males and females
added materially to their first-year advantage
over the smallest j-earlings during the second year
of fife. The maximum difiference was reduced by
compensatory growth during the third year, but
remained greater than the original difference. In

230

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

the fourth year further growth compensation
reduced the maximum difference below the first-
year value.

It appears to be characteristic of the growth of

the Lake Erie yellow perch that a first-year
advantage in size is increased in the second year.
Growth compensation occurs in the third and
fom-th years of life.

PROPORTION OF SEASON'S GROWTH COMPLETED AT TIME OF CAPTURE

Table 11. — Increment of growth completed by Lake Erie
yellow .perch at certain dates in 1927

For flsh captured—

Age group and sex

Oct. 24

Oct. 31 to
Nov. 21

Season's growth (increment of standard length) to
date of capture:
Age group I:

Males - -

Mm.
76

76

46
38
39

21
27
19

Percent
96
95

92
81
83

75
93
66
88

Number
28
40

3

15
22

2
2

8

Mm.

80

All fish »

79

Age group II:

Females - --

50

47

All fish "

47

Age group III:

28

Males

29

All fish 1 -

29

Proportion of season's growth completed to date
of capture:
Age group I:

Males _

Percent

100

All fish >

100

Age group II:

100

Males

100

AH fish 1 . -

100

Age group III:

Females -

100

100

All fish 1

100

Average (weighted) percentage

100

Specimens:

136

All fish 1

195

Age group II:

46

Males

95

All fish 1

170

Age group III:

Females.-- --.

15
21

AUflsh" .

39

' Includes fish whose sex was not determined.

Although the dates of collection of the Lake
Erie yellow perch were not distributed in such a
manner as to permit a thoroughgoing study of the
progress of growth during the season, scattered
data based on samples taken after June 30 do
provide a certain amount of information. The
calculated increments of growth added in the year
of capture and the percentages of these increments
of the year's total growth are shown in tables 11,
12, and 13 for three age groups collected in 1927,
1928, and 1929. The growth increments of perch
from late-season collections have been considered
to represent the total season's growth and hence
have been assigned the percentage of 100. The
selection of these late-season samples was not

Tablk 12. — Increment of growth completed by Lake Erie
yellow perch at certain dates in 1928

For flsh captured—

Age group and sex

July 17
and 23

Aug. 4
and 8

Aug. 23

Sept. 6

Oct. 16

and
Nov. 20

Season's growth (increment
of standard length) to
date of capture:
Age group I: All fish •.-

Mm.

Mm.

Mm.
52

26
20
26

20
20
19

Percent
70

70
69
70

83
91
79

71

Number

7

104
40
242

2
3
9

Mm.

Mm.
74

Age group II:

Female

29
27
29

26
23
24

Percent

37

Male

34

All fish '

15

18

37

Age group III:

24

Male

22

Allflsh 1

16
Percent

21

Percent

24

Proportion of season's
growth completed to date
of capture:
Age group I: All fish ' .

Percent
100

Age group II:

78
79
78

108
104
100

80
Number

100

Male

100

All fish 1

40

49

100

Age group III:

Female

100

Male

100

All flsh 1

67

45
Number

88

60
Number

100

Average (weighted)
percentage

100

4

Age group II:

68
70
148

5
5
10

77

86

All fish '

107

151

184

Age group III:

Female

18

Male.-- -

7

AU flsh 1

21

5

25

1 Includes fish whose sex was not determined.

arbitrary, but was based on a careful study of
the growth increments of fish in the collections of
single days. For example, detailed data for 1928
(not given here) demonstrated that the growth
increments of perch captured on October 16 were
as large as those of fish taken on November 20.
It was assumed, therefore, that no growth occurred
after October 16 in that year, and consequently
the sample of that date was included as part of
the "late-season" collection. In 1927, on the
other hand, the growth increments of perch cap-
tured on October 24 were noticeably smaller than
those of fish taken on October 31 and on various
dates in November. Accordingly, the October
24 sample was excluded in the computation of the

YELLOW PERCH OF LAKE ERIE

231

T,\BLE 13. — Increment of growth completed by Lake Erie
yellow perch at certain dates in 1929

For flsh captured—

Age group and sex

Julyl

Aug. 29

and
Sept. 8

Sept. 23

Nov. 12

to
Dec. 7

Season's growth (Increment of
standard lonsth) to date of
capture:
Age group I:

Mm.

A/m.

Mm.
67

Mm.
64

72

AH flsh •

62

67

42
38
40

26
21
24

Percent
105

70

Age group II:

9
8
9

3

1
2

Percent

39

39

All flsh

41

39

Age group III:

27

22

AH flsh ' -

20
Percent

26

Proportion of season's growth
completed to date of capture:
Age group I:

Percent
100

Males

100

All flsh ' ..

89

96

108
97
102

96
95
96

96

Number

1

100

Age group II:

23
20
23

11

4

8

9
Number

100

Males

100

AUflsh'..

Age group III:

108

100
100

100

AUflshi

Average (weighted) percent-
age

80

90

Number

100
100

Specimens:

Age group I:

Number
17

53

All flsh '

12

1

6
3
9

44
60
104

70

Age group II:

8
5
13

96
35
131

140

168

All flsh '

42

308

Age group III:

155

178

AUflsh '

64

333

' Includes flsh whose sex was not determined.

full-season increments of growth.* Other com-
binations of collections, as for example, that of
the samples of July 17 and 23, 1928, were made
only after examination proved the combinations
to be warranted.

The data of tables 11, 12, and 13 were presented
in considerable detail to bring out the fact that
neither sex nor age appeared to affect the course
of the season's growth. Females did not show
consistently lower or higher percentages than
males taken on the same day or days; neither did
the percentages vary consistently among samples
of different age groups captured on the same

> Estimates of the progress of growth during the season of capture made
by Hile. for the Cisco (1936) and for the rock bass (1941) in the lakes of north-
eastern Wisconsin, were based on comparisons of the growth increments up
to the time of capture with the full-season growth as calculated from samples
of the same year class in collections of later years. The severe discrepancies
between the calculated growth histories of different age groups of the same
year class of the Lake Erie yellow perch prohibit the use of the same pro-
cedure in the present stuily.

dates. It appears valid, therefore, to employ
the weighted percentages (given in each table) as
measures of the proportion of season's growth
completed at different dates.

In order to obtain a more definite idea of the
course of growth through the season, the weighted
percentages of tables 11, 12, and 13 were plotted
as functions of time within the season (fig. 7).
The smooth curve appearing in figure 7 was fitted
by inspection to the percentages for 1928 and 1929.
For reasons to be brought out presently the single
percentage available for 1927 (that of growth up
to October 24) was held to represent exceptional
conditions and was disregarded in the fitting of
the curve.

If the curve of figure 7 is accepted as descriptive
of the normal course of growth of the yellow
perch during the season, the following estimates
are obtained:

Percent Percent

_ , . r If total growth of total growth

b or montn OI— end of month within month

June 15 15

July... 50 35

August. 80 30

September. 100 20

According to these estimates relatively little
growth was completed before July 1 (only 15 per-
cent of the total) . The greatest increase in length
in a single month occurred in July (35 percent).
Growth dropped shghtly in August (to 30 percent)
and sharply in September (to 20 percent), and
appears to have ceased toward the end of Septem-
ber. The small percentage completed on July 1
suggests that growth began some time in Jime,
although it is not possible to be certain on that
point.

The preceding description of the course of the
growth of the yellow perch during the season
must be recognized as merely an approximation
since it was based on rather limited and scattered
data. The data for 1927 indicate that with
exceptional conditions the percentage of total
growth completed at different times within the
growing season may vary considerably. Perch
collected on October 24, 1927, were found to have
completed only 88 percent of the estimated total
growth for the season. Although the indicated
growth of 12 percent of the season's total between
October 24 and October 31 does seem to be too
high, the data provide evidence, nevertheless, that
growth was proceeding actively in October.

232

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

O
U)

a.

O
O

X

$
o
c
o

in

z
o
n

<
u
w

Ik
o

bl
O

<
h-
Z
bJ

u

ce
ij
a.

9

n

• /^

1927

1928

o

1929

•

8

y

/ o

7
60
50

/o

/

o

/

°/

4
3

/

2

y

/

10

4

»

2
JUNE

10 2

JULY

10 2

AUGUST

10 20

SEPTEMBER

10 2

OCTOBER

3 I

Figure 7. — Percentage of season's growth completed at different dates by Lake Erie yellow perch. Curve fitted to

1928-29 data by inspection.

Exceptional conditions may be expected also to
affect the course of growth in the early season

(earlier onset or more rapid early-season increase
in some years).

ANNUAL FLUCTUATIONS IN GROWTH

Data are available for the analysis of fluctua-
tions in the growth of the yellow perch taken by
impounding nets in Lake Erie in the two periods,
1927-29 and 1943^8. Although the annual
increments of growth in the years 1924-29 were
computed from samples of the entire take by the

nets, whereas the growth in 1940-48 was deter-
mined only from the legal-sized fish (8}^ inches and
larger), the average annual increments did not
differ greatly. The fluctuations in growth were
determined separately for each period and repre-
sent deviations from the average of the period to

YELLOW PERCH OF LAKE ERIE

233

Table 14. — Calculated annual growth increments according
to calendar year and year of life of Lake Erie yellow perch
taken by impounding net, 1927-29

[Data for sei.es shown separately]

Year of life

Males:

Age group HI:

Fourth year.

Third year_-

Second year.

First year

Age group II:

Third year.-

Second year.

First year

Females:

Age group III:

Fourth year.

Third year.-

Second year.

First year

Age group II:

Third year. .

Second year.

First year

Calculated growth Increments
(Inches) in—

1924

3.6

3.7

1926

2.3
3.6

3.6

2.4
3.5

1926

1.9
2.6
3.8

2.7
3.8

1.9
2.7
3.8

2.9
3.8

1.2
1.9
2.9

2.1
3.3
3.6

1.2
2.3
3.0

2.3
3.4
3.6

1928

0.9
1.8

1.4
3.2

1.0
2.0

1.3

3.2

1.7

0.9

which the individual years belong. The analysis
has been confined to the growth of age groups II
and III since other age groups contained too few
fish to give reUable averages in all years.

The calculated annual increments of age groups
II and III taken in 1927-29 are shown for each sex
in table 14 and those for the fish taken in 1943-48
are given in table 15. The data in both tables are
arranged so that the horizontal rows show the
growth in different calendar years of fish in the
same year of life. The vertical columns show the
growth in a single calendar year of fish in different
years of life. The growth histories of the individ-
ual age groups are shown in rows running diago-
nally from the bottom to the right.

The method of estimating annual fluctuations
in growth may be illustrated by the 1925 and 1926
data for the females in table 14. The 1926

Table 15. — Calculated annual growth increments according
to calendar year and year of life of Lake Erie yellow perch
taken by impounding net, 1943-48

[Data for sexes combined]

Year of life

Calculated growth increments (inches) in —

1940

1941

1942

1943

1944

1945

1946

1947

1948

Age group III:

1.2
1.6
2.8
3.9

1.8
3.4
3.7

1.3

1.9
3.1
3.5

1.9
3.3
3.8

1.1

1.6
2.5
3.8

1.9
3.3
3.5

I.l
2.0
2.4

1.3
1.7

1.4

2.1
2.5
3.6

2.4
3.9

3.7

Age group II:

2.1
3.6
3.8

1.9
3.0

2.4

Second year

3.1
3.9

First year

4.1

growths of 2.7, 3.8, and 3.8 inches of age group III
in the first and second years of life and of age
group II in the first j^ear of life totaled 10.3 inches
or 0.9 inch more than the total (9.4) of the corre-
sponding increments in 1925 (2.4, 3.5, and 3.5).
The average of the two totals is 9.85 inches. Com-
pared with this average, the total growths in 1926
showed an improvement of 9.1 percent. A con-
tinuation of this procedure shows the percentage
change in growth from each year to the next. The
position of each year's growth with respect to that
of 1924 is obtained by the successive addition of
the percentages of change. For example, the
growth of the group-Ill females decreased 5.6
percent from 1924 to 1925 as determined by this
method of computation, but as indicated above,
that of the group-II and group-Ill females in-
creased 9.1 percent from 1925 to 1926. Hence, the
growth in 1926 may be said to have been —5.64-
9.1, or 3.5 percent better than in 1924. In order
to make the percentage deviations describe the
changes with respect to average growth over the
period 1924-29, rather than only to growth in
1924, the mean of the deviations as computed by
the above procedure was subtracted from the in-
dividual deviation of each year. The same pro-
cedure was used to determine the annual fluctua-
tions in growth in 1940 to 1948 (table 15). The
method just described for obtaining the percentage
deviations from average growth is that employed
by Hile (1941) to determine the annual fluctua-
tions in growth of the Nebish I.rake (Wisconsin)
rock bass.

The annual percentage deviations of the growth
of the Lake Erie perch from the 1924-29 and 1940-
48 means are shown in table 16 for the sexes sepa-
rately, where possible, and for the sexes combined.
Particularly noteworthy is the very close agree-
ment between the percentage deviations of the
sexes. The coefficient of correlation between the
annual deviations in the growth of the sexes has
the high value of 0.959. This close correlation
may be construed as a strong argument for the
refiability of the percentages in table 16 as true
measures of the annual fluctuations in growth.

The annual variations in the growth of the Lake
Erie yeUow perch were fairly large. The ranges
for the percentages in the period 1924-29 were
23.2 percent for the females, 15.2 percent for the
males, and 18.3 percent for the sexes combined.
The range in the percentage variation of the sexes

234

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Table 16. — Deviations in growth rate of Lake Erie yellow perch and in mean air temperatures at Sandusky, Ohio, from

19S4-S9 and 1940-48 averages

Deviation from average growth

Deviations of mean temperatures

Male

Female

Average

May

June

July

August

September

October

1924

Percent

-4.8

-4.8

2.3

8.5

-6.7

5.5

Percent

-10.2

-4.6

4.5

13.0

-7.4

4.8

Percent

-7.6
-4.7
3.4
10.8
-7.0
5.2

-3.1
2.2

-1.7
-.4

1.8
-4.2

3.4
-7.4

9.7

op

-3.9

-1.6

1.8

1.2

2.1

.6

-2.0

4.4

3.0

-.4

5.4

-6.0

-1.0

-2.9

-1.9

'F.
-0.7
5.6
-1.5
-1.9
-2.1
.5

.2

1.0

.4

4.0

2.8

-2.8

-1.0

-3.2

-1.4

op

-1.9

-1.1

.0

.2

2.1
.6

1.1

1.3

1.1

.8

.6

-2.1

-.7

-2.5

.6

°F.

0.3

.6

2.8

-4.2

2.8

-2.1

-.3
-.9
-.9
.1
1.5
-.1
-4.1
4.7
-.3

"F.

-4.5

3.3

.1

3.3

-2.6

.3

-2.5

2.9

-1.3

-3.3

-.1

1.1

.7

.8

1.7

op

3.0

1925

-8.3

1926

-1.4

1927

4.4

1928

3.6

1929 -

-1.0

1940

-.9

1941

2.2

1942 --

-.1

1943

-2.4

1944 _

-l.B

1946

-2.3

1946 -

3.5

1947

6.5

1948

-4.7

Correlation (r) between growth and temperature (sexes combined)....

.346

-.030

.347

-.605

.504

-.117

combined during the 1940-48 period was 17.1 or a
little less than in the 1924-29 period. Growth was
below average in 1924 but unproved each year
untU the maximiun was reached in 1927. The
sharp decline in 1928 was followed by an improve-
ment in 1929. Growth in 1940 was below the
average for the period 1940-48. The increase in
1941 was followed by a 3-year period in which the
growth fluctuated but little; the variations were
greater in 1945-48. The poorest growth in the
1940-48 period was in 1947 and the best in 1948.

Neither a detailed discussion of all the probable
factors that contributed to the annual fluctuations
observed in the growth of the Lake Erie yellow
perch nor a review of the literature on fluctuations
in the growth of fish seems desirable. It may be
stated, however, that chief among the factors that
previous investigators found associated with
annual fluctuations in growth rate were changes in
the density of the population and fluctuations in
weather conditions (temperature and precipi-
tation) .'

It is not possible to state definitely whether fluc-
tuations in the density of the yellow-perch popula-
tion affected the growth of the species in Lake Erie.
Three years in which growth was above average
(1926, 1927, and 1929) and a year of poor growth
(1928) occurred when members of the strong year
class of 1926 were abundant. This situation sug-
gests that fluctuations in the density of the popu-
lation may have little or no effect on the growth
rate of the Lake Erie perch.

• Hile (1936) and Van Oosten (1944) have reviewed the literature on the
causes of fluctuations in the growth rate of fish.

In the study of the relation between meteor-
ological conditions and the growth rate of the Lake
Erie yellow perch, detailed records of rainfall, the
percentage of possible sunshine, mean wind veloc-
ity, and temperature were consulted. Preliminary
analyses of the data demonstrated that no corre-
lation existed between growth rate and the first
three of the meteorological factors. Seemingly,
variations in the amount of sunshine did not affect
the production of food sufficiently to influence the
growth of the perch . The influence of rainfall which
would affect turbidity and the chemical content of
the water, and of variation in wind velocity which
would affect turbidity, appeared to be too small to
detect, or was obscured by other factors.

Investigation of the relation between annual
fluctuations in temperature and in the growth rate
of the Lake Erie yellow perch yielded suggestive
results. The annual deviations of the air temper-
atures at Sandusky, Ohio,'" from the 1924-29 and
1940^8 averages in each month from May to
October, and the coefficients of correlation between
the annual deviations of growth and of temperature
in each month are shown in table 16. Included in
the table are data not only for the four months,
June through September, that were held to consti-
tute the normal growing season (p. 231), but also
for May and October. Evidence was brought out
that under exceptional conditions growth may
continue through October (p. 230), and it is be-
lieved possible that temperatures in May can

" These data on air temperatures were taken from Climatologioal Data of
the United States by Sections, Weather Bureau, U. S. Department of
Agriculture.

YELLOW PERCH OF LAKE ERIE

235

affect the time at which the season's growth begins.
It is recognized that air temperatures do not
provide an exact measure of water temperatures,
but air temperatures averaging exceptionally high
or low over the period of a month probably have a
significant effect on the average water temper-
atures, especially in such shallow water as in
western Lake Erie. Doan (1942) concluded that
either air or water temperatures may be used to
indicate monthly variations from normal, as
the two fluctuate similarly.

Of the six coefficients of correlation between
annual fluctuations in growth rate and in the air
temperatures of individual months listed in table
16, only that for August (r=— 0.605) may be
termed "significant" (r= ±0.514 when p = 0.05).
The coefficient for September (r=0.504) fell just
short of the significant value and those for July
(r=0.347) and May (r = 0.346), though moder-
ately high were far from significant. The ex-
tremely low values for October (r= — 0.117) and
June (7-=— 0.030) offer not the slightest sugges-
tion of any correlation between annual fluctua-
tions in growth rate and temperatures in those
months.

Even if temperature were known to be a major
factor in the determination of annual fluctuations
in growth rate, high correlations between growth
and temperature in individual months could
hardly be anticipated, since, as has been demon-
strated previously, the growing season of the Lake
Erie perch includes aU or part of several months.
It was with this in mind that the following coeffi-
cients of correlation (r) were computed between
annual fluctuations in growth and the combined
temperatures for several groupings of months:

May to October (inclusive) —0. 124

June to September (inclu.si ve) . 036

May and June .218

May, June, and July . 268

May, June, and September . 416

May, June, and October . 104

May, June, September, and October . 352

May and July . 371

May, July, and September . 562

May and September . 550

May and October . ne

May, September, and October . 327

June, July, and August —.289

June and August — . 461

June, August, and October.. —.537

June and September . 328

June and October — . 176

June, September, and October.

July and August

July, August, and September..

July and September

August and October

September and October

.202
.384
.289
.651
420
180

A detailed discussion is unnecessary, but
attention is called to the foUowing points:

1. There is no evidence of correlation between
annual fluctuations in growth rate and in tempera-
ture during the season as a whole. The coeffi-
cients for the 6- and 4-month periods May-October
and June-September were both low (—0.124 and
0.036).

2. Combinations of data for the 3 months,
May, July, and September, which exhibited
positive though statistically insignificant correla-
tions of temperature and growth yielded evidence
that a real correlation may exist. The coefficient
for the tliree months combined was 0.562, and
both of the groupings of two that included Septem-
ber — May and September (r= 0.550), and July
and September (7-=0.651)— also showed significant
positive correlation between temperature and
growth. Only the coefficient for May and July
(r=0.371) was below the significant value. It is
to be noted also that the combinations of still
other months with any of these three, or groupings
of them, diminished the correlation below the
significant level.

3. The negative coefficient of correlation between
annual fluctuations in growth and the combined
temperatures during the three months, June,
August, and October, that exhibited negative
values individually was significant (r=— 0.537)
but was less than the figure for August alone
('■=—0.605). Furthermore, not one of the co-
efficients for the three pairings of these months — •
June and August (r=0.461), June and October
(r=— 0.176), and August and October (r=
— 0.420)— was sigiuficant. This behavior of the
data suggests that any true negative correlation
between growth and temperature during the
growing seasons probably holds for August alone.

Inasmuch as earUer investigations have demon-
strated that correlations among meteorological
factors themselves can obscure true relations be-
tween those factors and growth (Hile 1941) or even
render the data highly ambiguous (Van Oosten
and Hile 1949), the possibility of similar inter-
ference was checked in the present data. This

236

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

work was carried out with special reference to the
relation between the annual fluctuations of temper-
atures in June and in August and those of other
months.

The lack of correlation between June tempera-
tures and growth appears to be somewhat anoma-
lous in view of the evidence of a positive correlation
between growth and temperatures in May and
July. Since the absolute temperatiire in Jime
normally is intermediate between those of May
and July a similar relation would be expected for
all 3 months. The coefficients of correlation be-
tween temperatures in June and those in certain
other months listed below are too small, however,
to support any belief that a true relation between
growth and June temperatures has been concealed
by correlations with temperatures of other periods
of the growing season.

Between June temperature and temperature in —

Correlation

May and July 0. 291

May and September . 214

May, July, and September . 246

July and September . 124

August .083

The high negative value of r for gi-owth and
August temperatures cannot be termed anomalous
since water temperatures reach their maximum
in that month in most years " and the concept that

II This statement is supported by records of lake Erie water temperatures
at the intake of the Chestnut Street Water Plant at Erie, Pa. (published in
the Annual Reports of the Commissioner of Water Works of that city).
According to those records the maximum monthly average water temperature
occurred in August in 23 of the 25 years, 1923-47; furthermore, August temper-
atures of the period averaged 2.3° and 3.7° F. higher than those of July and
September. The crib of the intake is located 5,100 feet north of the Presque
Isle Peninsula and is covered by 22 feet of water at low-water level. Al-
though Erie is located well to the east of the centers of greatest abundance of
the yellow perch, water temperatures off that port may be taken to indicate
monthly trends.

a high maximum might exert a depressing effect
on growth is not unreasonable. It was considered
desirable, nevertheless, to determine the possible
effects on the interpretation of the data of correla-
tions between August temperatures and those of
months that exhibited significant positive correla-
tions between temperature and growth. The
following coefficients, including one for May and
July in which temperature was not correlated
significantly with growth, were computed.

Between August temperature and temperature in —

Correlalion

May and July —0. 086

May and September — . 186

July and September — . 339

May, July, and September — . 205

Again none of the correlations between tempera-
tures in different periods was sufficiently close to
conceal possible relations.

The data presented in this section may be taken
as strong evidence that temperatures exert a
significant effect on the annual fluctuations in
growth of the yeUow perch in Lake Erie, with
high temperatures in May, July, and September
(especially September) accelerating growth, and
high temperatures in August retarding it.

Any attempt at a biological interpretation of
the observed correlations would, with our present
knowledge, be of little value. Conceivably, tem-
peratures may affect growth dnectly, as through
the control of the instantaneous rate of increase
or of the length of the growing season, or indi-
rectly, as through the control of the distribution
or abimdance of food organisms. Until more is
learned of the natural history of the perch, the
mechanism of the apparently significant correla-
tion between growth and temperature must remain
unknown.

LENGTH-FREQUENCY DISTRIBUTION

The catches of impoimding nets and gill nets
differed in the actual form of the frequency dis-
tribution as well as in the size of fish taken (table
17). The length distribution of yellow perch
caught in trap nets and pound nets was unimodal
each year. The shoal-net collections, on the
other hand, showed definite bimodal length distri-
butions for 1927 and 1929, but gave no indication
of bimodality in 1928. The fairly large number
of small perch taken by the shoal nets during
1927 is probably explained by the presence of the

abundant year class of 1926, then in their second
year of life (age group I). The bimodal length
distribution of the bull-net samples in 1927 was
the result of the accidental captm-e of a large
school of small fish on a single day. These smaller
individuals ordinarily were not gfiled in the true
sense, but rather, were captured by tangling the
webbing of the net in the marginal bones of the
mouth or in the fins.

It will be noticed that there was considerable
annual variation in the length of the modal fre-

YELLOW PERCH OF LAKE ERIE

237

Table 17. — Length frequencies of Lake Erie yellow perch by year of capture and type of gear
[An asterisk designates tbe modal interval in each frequency distribution]

S tand ard-lengt h

Total length
equivalent to

Taken by impounding nets

Taken by sboal gill nets

Taken by bull gill nets '

midpoint

1927

1928

1929

1930

1931

1932

1937

Total

1927

1928

1929

Total

1927

1928

1929

Total

Incha

2 2

1

1

2.7

2

2

81 to 90 mm

4

2

2

4 5

1

1

1

5

6

1

1

101 to no mm

111 to 120 mm

6

4

1

31

36

9

1

13

23

4

4

5.4

21

5

73

7

106

37

1

8

46

27

1

28

121 to 130 mm

131 to 140 mm

5 9

46

19

61

40

14

180

64

5

69

•49

49

6.3

108

94

108

168

108

1

677

49

4

4

57

35

1

36

141 to 150 mm

6.7

272

477

291

529

568

3

3

2,143

47

16

1

63

17

9

i

27

151 to 160 mm

7.2

380

1,143

553

1,016

1,167

1

10

4,270

26

11

1

38

4

14

18

161 to 170 mm. .--

7.6

495

•1,531

1,021

•1,641

2,608

10

24

7,130

14

30

4

48

1

30

3

34

171 to 180 mm

8.1

•509

1, 090

1,692

1, 364

4,524

28

•35

9,242

13

84

27

124

3

40

5

48

181 to 190 mm

8.6

414

612

2, 653

1,126

•4,963

•46

24

•9,738

31

241

165

437

6

79

lb

100

191 to 200 mm

9.0

375

411

•2, 632

759

3,608

27

19

7,831

130

708

987

1,825

13

136

78

227

201 to 210 mm

9.4

317

253

1,765

376

1,399

10

6

4,126

397

•866

•1,750

•3, 013

40

•173

262

46S

211 to 220 mm

9.9

164

98

776

121

381

6

6

1,651

•545

629

1,214

2,288

36

130

•300

•466

221 to 230 mm

10.3

82

29

263

44

103

4

625

237

200

443

880

16

46

1.50

212

231 to 240 mm

10.7

16

14

83

22

29

1

165

51

47

88

186

3

16

30

49

241 to 250 mm

11.2

17

2

28

10

8

65

16

12

24

62

1

4

4

9

251 to 260 mm

11.6

3

3

3

4

4

17

2

2

3

7

I

1

2

261 to 270 mm

2

2

3

8

12 5

1

1

13.0

4

3

7

1

1

1

1

291 to 300 mm

13 4

1

1

13.9

1

1

Total

3,224

5.785

11, 939

7,118

19, 391

133

131

47, 721

1,670

2,764

4,744

9,168

257

681

838

1,776

Average standard Ic

ngth Cmm.)

177

170

187

174

182

186

181

180

201

203

207

206

167

200

212

201

Average total lengt

1 (inches)

8.17

7.85

8.64

8.04

8.41

8.69

8.36

8.32

9.22

9.32

9.50

9.41

7.72

9.18

9.73

9.22

Percentage illegal

Oess than SH

inches)

61.1

78.8

38.1

69.8

63.4

43.6

61.1

65.6

15.9

7.4

2.0

6.2

54.9

17.0

1.4

16.1

' Gill nets 22 meshes deep.

quency group in each gear. The modal frequency
intervals of perch caught in impounding nets
varied from 161-170 mm. (7.6 inches total length)
in 1928 and 1930 to 191-200 mm. (9.0 inches
total length) in 1929, or over a range of 30 mm.
(1.4 inches). Annual fluctuations in the per-
centage occurrence of individuals in the several
length intervals of the trap-net and pound-net
catches of 1927-29, inclusive, are showTi graphi-
cally in figure 8, which includes only the length
range over which the representation was continu-
ous. The years 1927 to 1929 were selected for
graphic presentation because the year class of 1926
dominated the collections for each of those three
years. The mode of the 1927 specimens caught in
impounding nets was at a length 10 mm. greater
than the mode of the 1928 collections. Since col-
lections of both years were dominated by fish of the
1926 year class, one would expect the length of the
modal frequency in 1928 to be greater than that in
1927. However, this discrepancy can be ex-
plained readily. It may be seen in table 21 that
two age groups were well represented in the 1927
icollections ; age group I made up 48.9 percent and
age group II made up 39.9 percent of the total.
The 1928 collections were made up almost entirely
(90.6 percent) of group-II fish. Approximately

> Oill nets 100 meshes deep.

95 percent of the 1927 specimens were taken in
October and November whereas some 72 percent
of the 1928 individuals were taken by the end of
June. Thus, the 1926 year class (group I of 1927),
had only a small part of a growing season in which
to increase their lengths before the 1928 collections
(in which the year class appeared as age group II)
were made. Furthermore, the occurrence of large
munbers of group-II fish m 1927 caused the length
at maximum abundance in the combined collec-
tions of that year to be greater than that of the
dominant age group (see table 19). Thus, the
reduced abundance of fish older than the 1926
year class in 1928 and the short period of time
Lutervening between the dates of collection of the
1927 and 1928 samples no doubt account for the
shorter modal length in 1928.

The large modal length in 1929 may be attrib-
uted in great measure to the dominant 1926 year
class which had completed approximately 2 full
years' growth subsequent to the collection of the
1927 material. Even so, the length of the modal
frequency in 1929 was somewhat less than the
modal length of the 1926 year class (age group III)
in that year because of the strong representation
of the 1927 year class (age group II). In general,
the position of the modal frequency each year can

238

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

2 8

24

>
O
2
UJ

O

UJ
IT
U-

LJ

o
<

I-
z

LJ
O
(T
U
Q.

I

I I

I 2

TOTAL LENGTH IN INCHES

Figure 8. — Percentage frequency distribution of total length of Lake Erie yellow perch in 1927, 1928, and 1929 collections
from impounding nets. Curves extend only over length range where representation was continuous.

be explained by the known age composition of the
stock and the time of year when the collections
were obtained . A similar explanation may acco unt
for the shifts in the modal frequency of the years
1930 to 1932 and 1937.

The gill-net collections showed trends in the
annual fluctuation of the length at maximum
abundance similar to those of the impoimding nets,
but the total range of variation of the length of the
modal frequencies of the fish actually gUled was

reduced. The modal frequency interval of the
shoal-net samples varied only from 201-210 mm.
(9.4 mches total length) in 1928 and 1929 to
211-220 mm. (9.9 mches total length) in 1927,
or extended over a range of 10 mm. as compared
with a range of 30 mm. in impounding-net samples.
The modes of the yellow perch actually gilled by
the bull net were at the 201-210 mm. (9.4 inches
total length) interval in 1927 and 1928, and at the
211-220 mm. (9.9 inches total length) level in

YELLOW PERCH OF LAKE ERIE

239

1929. The reduction in the annual fluctuation of
the position of the modal length intervals of the
gilled fish in the gill-net collections as compared
with the impounding-net samples can be ascribed
to the greater selectivity of gill nets.

The lengths of the modal frequencies of fish
gilled in both shoal and buU nets were without
exception greater than those of fish caught in
impounding nets in the same year. The general
differences between the length distribution of the

3 5

fish from impounding, shoal, and bull nets (all
collections combined) are shown graphically in
figure 9. The curves are based on the totals of
table 17, expressed as percentage frequencies.
The graph includes only the length range over
which representation was continuous. As men-
tioned in the preceding paragraph, the much more
compact distributions and the greater average size
of perch in the gill-net collections may be attrib-
uted to net selectivity. The occurrence of small

3

2 5

U

z

3

o

<

z

UJ

o

2

I 5

I

TOTAL LENGTH

9
I N

I

1 2

N C H E S

Figure 9. — Percentage frequency distribution of total lengths of Lake Erie yellow perch in collections from each kind of
gear. Curves extend only over length range where representation was continuous.

240

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

perch in the gill-net collections does not represent
gUling but, as stated earlier, is the result of the
entanglement of the marginal bones of the mouth
or of the fins in the gill-net webbing.

The occurrence of illegal-sized yellow perch in
unpounding-net samples (table 17) varied from a
maximum of 78.8 percent in 1928 when the
collections were dominated by the 1926 year class
as age group II to a minimum of 38.1 percent in
1929 when the same year class was dominant as
age group III. Had the computation for 1928
been made on the basis of the then-effective size
limit of 9 inches instead of the current 8% inches,
the proportion of undersized yellow perch would
have been even greater — 89.6 percent. The 1927
collection which was dominated by the 1926 year
class as age group I nevertheless had relatively
fewer illegal-sized yellow perch (61.1 percent
computed from a size limit of 8% inches and 76.2
percent from a size limit of 9 inches) than the 1928
collection. An explanation of this discrepancy
was given on page 237. Perch under the legal size
limit were in the minority in the impounding-net
samples in only 2 of 7 years (1929 and 1932).
The percentage of undersized perch in the collec-
tions of all years combined, computed from a size
limit of 8% inches, was 55.6.

Illegal-sized yellow perch were relatively much
less abundant in the gill-net than in the impound-
ing-net catches, except in the 1927 bull-net
samples which contained a high proportion of
small, accidentally captured fish. Undersized
individuals in shoal-net samples varied from a
maximum of 15.9 percent in 1927 to a minimum
of 2 percent in 1929 and amounted to 6.2 percent
for the 3 years' collections combined. Com-
puted from the then-effective size limit of 9 inches,
the 1927 and 1928 percentages would have been
higher — 20.3 and 23.4. The percentages of under-
sized yellow perch in bull nets were 54.9 in 1927,
17.0 in 1928, and 1.4 in 1929. On the basis of the
then-effective size limit of 9 inches these would
have been increased to 59.1 and 33.2 percent in
1927 and 1928. For all years combined the per-
centage of illegal-sized yellow perch in the bull
nets was 15.1 as compared with 6.2 in the shoal-
net collections. The percentage of Ulegal-sized
fish in all gill nets was 7.6.

The proportion of illegal-sized yellow perch in
gill-net catches provides a fairly precise measure
of the destruction of undersized individuals by

this type of gear, as practically all individuals are
dead at capture or are killed in the process of
removal from the nets. It should be noted,
however, that on the average the percentage of
undersized fish in gill-net samples usually fell well
below Ohio's legal allowance of 10 percent in the
conomercial catch, especially since the allowance
is based on weight rather than on numbers of fish.

The destruction of illegal-sized yellow perch can
be determined less accurately for impounding nets
than for gUl nets because the trap-net and pound-
net fishermen are required to return all illegal-
sized fish to the water. It is relatively certain
that an unknown portion of these fish die as the
residt of handling. It is known that on the aver-
age 14 percent of the Ulegal-sized perch taken by
Lake Erie trap nets are dead at the time of lifting.
(See footnote 5, p. 221.) Since 55.6 percent of the
yellow perch from impounding nets were under-
sized, it may be computed that for every 1,000
yellow perch taken, 76 illegal-sized fish were de-
stroyed. This value was well below the 151 de-
termined for buU nets but was above the 62 for
shoal nets, and equaled the 76 from all gUl nets.
However, the computed number of illegal-sized
yellow perch destroyed by impounding nets must
be considered as the minimum since it does not
include those fish that are lolled during the sorting
of the catch to conform to the legal-size limit.
Further, impounding nets took many more fish
during the year than did the gill nets and therefore
destroyed many more individuals. The data seem
to offer good support to Van Oosten's (1936) con-
clusion that more fish are destroyed by trap nets
than by gUl nets.

The importance of the destruction of small
yellow perch by trap nets is emphasized when it is
remembered that in recent years this gear has
accounted for approximately 61 percent of all
perch taken in the United States waters of Lake
Erie (65 percent of those taken in Ohio waters) .^^

Table 18 contains a summary of the length fre-
quencies (total lengths) by half-inch intervals, the
percentage frequencies, and the cumulative per-
centages for Lake Erie yellow perch taken in
different types of gear, with all years' collections
combined. Practical considerations make such

13 Percentages were computed from data for the calendar years 1930, 1931,
1932, 1934, 1936, 1937, and 1938 contained in the former V. S. Bureau of Fish-
eries publication, "Fisheries Industries of the United States," Report of the
Commissioner of Fisheries, for 1931, 1932, 1933, 1935, 1937, 1938, and 1939.

YELLOW PERCH OF LAKE ERIE

241

Table 18. — Length frequencies of Lake Erie yellow perch taken in different types of gear

[Collections of all years combined]

Trap and pound nets

Shoal gill nets

Bull gill nets

Total-length interval '

Number of
specimens

Percentage

Cumulative
percentage

Number of
specimens

Percentage

Cumulative
percentage

Number of
specimens

Percentage

Cumulative
percentage

1
2

0.01
.02

0.01

.03

.03

.03

.07

.22

.72

1.31

2.24

2.86

3.38

4.06

6.18

17.13

49.27

83.69

97.30

99.41

99.97

99.99

99.99

99.99

100.00

3 . I to 4 inches

1

7

98

130

664

1,872

5,182

8,109

10, 473

11,346

6,189

2,634

761

174

65

11

6

3

4

2

(•)
0.01
.21

.27

1.39

3.92

10.86

16.99

21.95

23.78

12.97

6.62

1.67

.36

.14

.02

.01

.01

.01

«o.oi

.22
.49
1.88
5.80
16.66
33.65
55.60
79.38
92.36
97.87
99.44
99.80
99.94
99.96
99.97
99.98
99.99
100. 00

4

14

46

S4

85

67

48

62

194

1,004

2,947

3,156

1,248

193

'I

.04

.16

.60

.69

.93

.62

.62

.68

2.12

10.95

32.14

34.42

13.61

2.11

.66

.02

4 5 to 5 inches _ .

2

18

40

61

33

22

40

63

156

399

594

297

50

8

2

0.11
1.01
2.25

2.87

1.86

1.24

2.26

3.56

8.78

22.47

33.45

16.72

2.82

.45

.11

0.11

5.0 to 5.5 inches

1.12

3.37

6.0 to 6.6 inches

6.24

8.10

7.0 to 7.5 inches

9.34

7.5 to 8.0 inches

11.69

15.14

8.5 to 9.0 inches

23.92

46.39

9.5 to 10.0 inches -

79.84

96.66

10.5 to 11.0 inches

99.38

11.0 to 11.5 inches __.

99.83

11.5 to 12.0 inches

99.94

12 to 12 5 inches

13.0 to 13.5 inches

1

.01

1

.06

100.00

13 5 to 14 Inches

1

' Each H-inch interval contains lengths up to but not including the greater value.
> Specimens occurred in the samples but made up less than 0.005 percent of the total.

a tabulation desirable sLnce legal-size limits for
yellow perch are expressed in terms of the total
length in inches. It may be seen at a glance, for
example, that with a size limit of 8K inches, 55.6
percent of the yellow perch taken in trap nets were
under legal length, whereas 79.38 percent were
undersized with a 9-inch limit; or it may be seen
that almost 98 percent of the yellow perch in trap-
net catches were less than 10 inches long. The
tabulation also permits ready comparisons of the
catches by different types of gear.

The length distributions by age for impounding-
net samples are shown in table 19. The collections
of 1930, 1932, and 1937 are omitted from the table
because the number of specimens whose ages were
determined was too small in each of those years
to give reliable results. The length range of fish
of the same age did not vary greatly in the better-
represented age groups during the 3 years 1927 to
1929. The range in length of the age groups was
sufficiently great to cause considerable overlapping
between these groups. Because of this overlap,
length cannot be held a reliable indication of age.
Age groups IV and V were represented by too few
individuals to give an accurate idea of the range
in either group. The distinctly unimodal dis-
tribution within each well-represented age group
and the great amount of overlapping in length
probably accounted for the unimodal length dis-

tribution in the yearly collections from impounding
nets.

Additional data obtained from impounding nets
each year in the period 1944^8 (table 20) make
possible a comparison of the length distribution
of the legal-sized yeUow perch in the commercial
catch of those years with the legal-sized fish in-
cluded in the biological samples collected from
the same type of nets in the 3 years 1927 to 1929.
Only age groups II and III will be compared since
younger and older fish contributed but little to
the commercial catch.

The length distribution of the legal-sized (8^
inches total length and larger) yellow perch
assigned to age group II exhibited a striking dif-
ference between the two periods, 1927-29 and
1944-48. The minimum legal size of 8% inches
was near, or above, the modal length of aU group-II
fish in each of the 3 years 1927 to 1929. The
length distribution of group-II fish in each year
of the period 1944-48 gave strong reason to be-
lieve that the 8K-inch size limit was below (less
than) the modal length each year with the pos-
sible exception of 1945 when the small sample
agreed more nearly with the data of the earUer
period. Also in each year except 1945 of the
recent period, age group II contained longer fish
than in any year of the earlier period. Fmlher,
the number of the longer group-II fish tended to

242

FISHERY BULLETIN OP THE FISH AND WILDLIFE SERVICE

Table 19. — Length frequencies of Lake Erie yellow perch by age and year of capture, taken by impounding nets from western

and middle Lake Erie

[An asterisk designates the modal interval in each frequency distribution)

Total
length
equiva-
lent to
midpoint

Age group I

Age group U

Age group III

Age group IV

Age group V

AUage

interval

1927

1928

1929

1927

1928

1929

1927

1928

1929

1927

1928

1929

1927

1929

groups

106 to 110 mm

111 to 116 mm....
116 to 120 mm

inches
6.1
6.3
6.6
6.8
6.0
6.1
6.4
6.6
6.8
7.1
7.3
7.6
7.8
8.0
8.2
8.6
8.7
8.9
9.1
9.3
9.6
9.8
10.0
10.1
10.4
10.6
10.8
11.1
11.3
11.5
11.7

1
2

1

2

2

1
1
3
3
6

13

•16

6

11
7
9
6
1

1

2

1

126 to 130 mm....
131 to 135 mm....
136 to 140 mm....
141 to 146 mm....
146 to 150 mm....

161 to 156 mm

166 to 160 mm

161 to 165 mm

166 to 170 mm

171 to 176 mm....
176 to 180 mm....
181 to 186 mm... _
186 to 190 mm....

191 to 196 mm

196 to 200 mm....

16
18
23
26
32
•62
37
13

I

1

2

1

2"

' r

2

^

g

7

1

3

2

7

20

21

34

36

27

•42

39

33

39

27

21

16

4

1

14

I

4

8

14

14

•27

21

•27

20

18

10

11

3

3

2

3

11

29

41

68

80

99

•122

108

100

77

49

28

16

7

3

1

38

1

55

68

1

1
2
3
3
3
6
•8
2
6
8
6

§"

1

106

1
3
4
6
6
4
3
10
•11
8
4
4
2

1
2

134

4

10
18
31
31
52
70
72
•76
68
68
61
36
16
16
10
2
2

199

•223

211

1

•223

1

2

5
8
7

5
3

7
•12
2
6
4
1

204

197

-.

1

189

163

1

133

211 to 216 mm....
216 to 220 mm....
2'>l to 225 mm

106

88

1

71

1

1

41

1

i"

1
1

25

236 to 240 mm

21

12

2

4

2

266 to 260 mm....

1

1

Total -

236

11

83

192

832

372

47

70

632

6

6

6'1

2

3

2,660

Average standard length

162
7.6

97.9

138
6.4

100.0

162
7.0

100.0

181
8.4

69.4

179
8.3

61.2

182
8.4

47.0

196
9.0

26.6

198
9.1

26.7

207
9.6

8.2

214
9.8

20.0

217
10.0

214
9.8

250
11.4

223
10.1

186

Average total length (inches)-
Percent illegal Oess than 184

8.6
47.2

Table 20. — Length frequencies of legal-sized yellow perch taken commercially and as biological samples in impounding nets

in western and middle Lake Erie

Standard-
length
Interval

1927'

1928 >

1929 »

1944 »

1946'

1946 »

1947'

1948 >

Years combhied

Total-length interval i

1927-29

1944-48

Age group II:

Millimeiers
184 to 189
190 to 196
196 to 201
202 to 206
207 to 211
212 to 217
218 to 224
226 to 230
231 to 236
237 to 241

28
20
11
11
2
4
1

119
104
£4
28
12
7
3

44
43
46
26
18
16
3

6
10
17
16
12
6
2

13
13
6

6

S
1

8
8
34
53
26
17
7
1

13

22

60

24

32

9

9

2

2

19
37
65
48
62
28
29
3
7
1

191
167
110
66
32
27
7

59

8 75 to 9 00 inches

90

172

146

9.50 to 9.75 inches -

140

61

10 00 to 10 25 inches

47

10 9*1 tn in 'iO Inrhp";

6

1

10

in 7fi tn n 00 inrhpi

1

Total number

77
8.96

327
8.86

196
9.07

69
9.37

47
9.10

164
9.45

163
9.28

299
9.39

699
8.94

732

Average total length (inches) —

9.36

Age group III:

184 to 189
190 to 196
196 to 201
202 to 206
207 to 211
212 to 217
218 to 2.i4
226 to 230
231 to 236
237 to 241
242 to 247
24S to 252
263 to 268

3
11

4
4
6
4
2
2

5
4
12
12
6
6
3
2
2

41

68

84

69

76

93

68

51

21

12

8

3

1

1
6
17
18
17
14
7
2
3

2
11
30
21
32
14
16
4
4

1
1
20
20
28
16
9

49

73

100

86

86

103

'3

66

23

12

8

3

2

4

8 75 to 9 00 inches

18

4
5
1
2

2
6
16
12
9
3
1
2

n

9.25 to 9.50 inches

69

94

9.76 to 10.00 Inches

68

10 00 to 10 25 inches

40

10 25 to 10 50 Inches

9

10 50 to 10 75 inches

2

1

10

10 75 to 11 00 irches

3

1

1

11.25 to 11.50 inches--

1

3

3

36
9.29

62
9.45

684
9.63

12
9.46

85
9.63

60
9.96

134
9.61

101
9.63

671
9.60

382

Average total length (inches)

9.62

' Each Interval contains lengths up to but not including the greatest value. ' From biological samples. • From commercial samples.

YELLOW PERCH OF LAKE ERIE

243

increase in the later years of the 1944-48 period.
The average total length of the legal-sized group-II
yellow perch was considerably larger in each year
except 1945, of the period 1944^8, than in any
year of the period 1927-29.

The totals for the two periods place the modal
length of the legal-sized fish in the 8.50 to 8.75
inch interval in 1927-29 and in the 9.00 to 9.25
inch interval in 1944-48. The weighted-average
total lengths for the two periods were 8.94 and
9.36 inclies, respectivelj*. The use of unweighted
means of the annual average total lengths to elim-
inate the distorting effects of the differences in
size of samples changes the averages for the
periods only slightly, to 8.96 and 9.32 inches.
Both methods of computation show that the
age-group-II fish of legal size taken in 1944-48
averaged about 0.4 inch longer than those taken
in 1927-29.

The general pattern of the length distribution of
the legal-sized yellow perch assigned to age group
III failed to show as great differences between the

1927-29 and 1944-48 periods as were exhibited
by group-II fish. The modal frequency interval
was well above the SJs-inch size limit in all years.
The average total length was greater each year
in the 1944-48 period than in either 1927 or 1928
l)ut agreed rather well with that of 1929. The
weighted-average length was almost identical in
both periods because the best represented year in
the earlier period included fish with the longest
average length while the best represented of the
later years included specimens with the shortest
average for the period. The unweighted means of
the annual averages in the two periods were 9.46
and 9.64 inches. The more reliable vmweighted
means thus show the legal-size 3-ellow perch as-
signed to age group III to have averaged approxi-
mately 0.2 mch longer ua 1944^8 than m 1927-29.
Although these data do not constitute proof,
the,v do offer strong evidence that yellow perch
in Lake Erie were growing at a faster rate in
1944-48 than m 1927-29.

AGE COMPOSITION AND ABUNDANCE OF YEAR CLASSES

In the study of the age and 3-ear-class composi-
tion of the Lake Erie yellow perch it should be
remembered that the samples must be considered
truly descriptive, not of the stock, but rather of
the catch of commercial gear. Trap-net and
poimd-net collections were employed in the bio-
logical study of the relative abimdance of age
groups and year classes because those nets are less
selective than gill nets. Although samples from
impounding nets in a single j^ear may not give
dependable information as to the relative abun-
dance of the year classes represented, the per-
sistent abundance or scarcity of a year class at
different ages, that is, in different years' collec-
tions, offers a reasonably trustworthy method for
the detection of exceptionally strong or weak year
classes. Of course, a knowledge of the age com-
position in both gill nets and impounding nets is
of importance in the practical problem of deter-
mining the effects of these types of gear on the
stock.

The number of specimens and the percentage
occurrence of each age group in the yearly collec-
tions of biological samples from impounding nets
for the years 1927-37 are shown in table 21. Ago
group I dominated the samples in one (1927) of

the six years in which collections were made,
although the percentage of abundance of this age
group was also high in 1937. Age group II
dommated in tlu-ce years (1928, 1930, and 1937),
and gi'oup III was dominant m the remaining two
years (1929 and 1932). However, the fact that
the 1932 samples were taken from the spawning
run in April, when the fish were comparable in
size and maturity to those in the next younger
age group iu the previous fall, throws doubt on the
validity of comparisons between the data for this
and other years. The spawning run consists al-
most entirely of matiu-e individuals; consequently,
those age groups containing high percentages of
immatm-e fish were not represented adequately in
the 1932 collections. The 1932 data serve, how-
ever, to show the age composition of the catch in
the spawning-run fishery.

It will be brought out later (p. 251) that unusual
conditions made possible the dominance of age
group I in 1927 and of age group III in 1929.
Dominance of age group II in the late-season
catch of yellow perch in impounding nets may be
considered the normal condition.

The preceding remarks were based on the total
catch of impounding nets including both legal-

244

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Table 21. — Distribution by age groups of yellow perch in the different years' collections from impounding nets

(Percentages in parentheses]

Year

Month of capture

Number ot
specimens

Number and percentage in

age group—

I

II

III

IV

V

1927

481
918
1,151
222
133
131

235

(48. 9)

11

(1.2)

83

(7.2)

1

(0.4)

192

(39. 9)

832

(90.6)

372

(32. 3)

172

(77. 5)

2

(1.6)

66

(50.4)

47

(9.8)

70

(7.6)

632

(54.9)

45

(20.3)

98

(73.7)

3

(2.3)

5

(1.0)

6

(0.6)

61

(6.3)

4

(1.8)

33

(24.8)

2

1928

July, August, September, October, and November

(0.4)

1929

.■5

1930

(0.3)

1932

April

1937

November . _

62
(47.3)

3,036

392
(12.9)

1,636
(53. 9)

895
(29. 6)

108
(3.6)

5

(0.2)

* The 1929 data may be considered as representative of autumn conditions since 66 percent of the specimens were collected in November and December.

sized and illegal-sized fish. It is of practical value
to know also the representation of these two size
gi'oups separately as well as the age groups in the
marketable catch, that is, legal-sized fish. Data
on these subjects are contained in table 22 which
shows the number and percentage of legal and
undersized yellow perch in each age group repre-
sented in the total catch and in table 23 which
gives the numerical and percentage composition
of the marketable catch in each year's collection.
From the former table it may be seen that legal-
sized yeUow perch constituted an unimportant
proportion of age group I. This age gi'oup domi-
nated the catch of impounding nets in 1927 but

apparently contributed nothing to the commercial
yield. The highest percentage of legal-sized
perch in any group I was 8.1 in 1937. The
majority of all group-II perch captured were
undersized — 60.3 percent as determined from a
size limit of Sji inches. In only two years (1929
and 1937) did the percentage of undersized perch
in age group II fall below 50. Thus it may be seen
that the age group that normally dominated the
catch of impounding nets (the spawning-run fish-
ery excepted) consisted largely of yellow perch that
could not be retained and sold by the fisherman.
The percentage of undersized perch in all group-
Ill fish combined was small (15.1). In two years

Table 22. — Distribution by age groups of legal- and illegal-sized yellow perch in the different years

impounding nets
[Percentages in parentheses]

collections fro7n

Minimum
legal-size

limit
(inches)

Number
of speci-
mens

Number
of legal

in all

ages

Number
of illegal

in all

ages

Number and percentage in age group —

Year

I

II

III

IV

V

Legal

Illegal

Legal

Illegal

Legal

Illegal

Legal

Illegal

Legal

Illegal

1927.--

9

m

9

m

8M
SH
8H

m

8!.4

481
481
918
918
1, 151
222
133
131

3,036
3,036

56

(11.6)

123

(25. 6)

151

(16.4)

384

(41. 8)

843

(73. 2)

54

(24. 3)

74

(55. 6)

60

(38. 2)

1,228
(40. 4)
1.528
(50.3)

425
(88. 4)

358
(74. 4)

767
(83.6)

534
(48. 2)

308
(26. 8)

168

(75. 7)

59

(44. 4)

81

(61. 8)

1,808
(59. 6)
1,508
(49. 7)

(0)

4
(1.7)

(0)

(0)

(0)

(0)

236

(100.0)

231

(98. 3)

11

(100. 0)

11

(100.0)

83

(lOO.O)

1

(100.0)

29

(15.1)

77

(40. 1)

103

(12.4)

327

(39.3)

195

(52. 4)

9

(5.2)

(0)

42

(63.6)

378
(23.1)

660
(39. 7)

163
(84. 9)

116
(59. 1)

729
(87. 6)

.505
(60. 7)

177
(47. 8)

163

(94.8)

2

(100.0)

24

(36. 4)

1.268

(76. 9)

986

(60.3)

21
(44. 7)

36
(74. 6)

44
(62. 7)

62

(74. 3)

.584

(92. 4)

41
(91.1)

45

(45. 9)

3

(100. 0)

738
(82. 5)

760
(84. 9)

26

(56.3)

12

(25. 5)

26

(37. 1)

18

(25. 7)

48

(7.6)

4

(8.9)

53

(54. 1)

(0)

157
(17. 5)

135
(15. 1)

4

(80.0)

5

(100.0)

4

(80.0)

5

(100. 0)

61

(100.0)

4

(100. 0)

29

(87. 9)

1

(20.0)

(0)

1

(20.0)

(0)

(0)

(0)

4

(12. 1)

2
(100. 0)

2
(100.0)

1928

(0)

(0)

1929

3
(100. 0)

1930

(0)

1932

1937

5
(8.1)

5
(1.3)

9
(2.3)

57
(91. 9)

387
(98. 7)

382
(97. 7)

Total:
Effective limits >.

8H-inch limit!-.

102
(94. 4)

104
(96.3)

6
(5.6)

4
(3.7)

6
(100. 0)

(100. 0)

(0)

(0)

' The number and percentage of legal- and illegal-sized fish in the various age groups of all years' collections combined as determined for the size limit effec-
tive in each year.

' As determined for SJi-inch limit for all years.

YELLOW PERCH OF LAKE ERIE

245

(1927 and 1932), however, this percentage ex-
ceeded 50. The proportion of undersized perch in
age group IV may be considered unimportant, and
all group-V perch were of legal size.

The effects of the varying percentages of legal
and undersized yellow perch in the different age
groups, and of the varying abundance of the age
groups themselves, on the age composition of the
marketable catch may be seen in table 23. Age
group II dominated the commercial catch in all
years' samples except four, 1929, 1930, 1932, and
1945, when group-Ill fish were most numerous.
The data in table 23 give strong indication that
the time of capture within the season may have
an important effect on the age composition of the
marketable catch. The April 1932 (spawning-
run) sample contained no legal-sized yellow perch
younger than age group III. The midsummer
collection of 1930 (most of the fish were taken in
July) was dominated by age group II when both
legal and undersized yellow perch were included

Table 2Z.— Distribution by age groups of legal-sized yellow
perch in the different years' collections from impounding
nets

IPerceutages in parentheses]

Legal

size

limit >

(inclies)

Number
of speci-
mens

Number and percentage in age group—

Year

I

II

III

IV

\-

1927

11)28.

1929.. ....

19,'!0

1932-

1937

1943

1944 -

1945

1946

1947

1948

Total

A verage
(unweieht-
ed) percent-
age :
Effective

9

m

9
8H

sy-

8^

m

8H
8H

m

(■)

(•>

8M

56

123

151

384

843

54

74

.W

28

81

153

213

320

420

2,443

(0)

4
(3.2)

(0)

(0)

(0)

n
(n)

(n)

5

(10. n)

6
(21.4)

(0)

(0)

(0)

1

(0.3)

(1.7)

19

(0.8)

(2.8)
(3.0)

29

(51. 8)

77

(62. 6)

103

(68.2)

327

(8,'i.2)

195

(23.1)

9

(10. 7)

(0)

42

(84.0)

16

(57. 1)

69

(85.2)

47

(30.7)

154

(72.3)

163

(50.9)

299

(71.2)

1.126

(46. 1)

(50.9)
(53.3)

21

(37. 5)

3i
(28. .1)

44
(29.1)

62

(13.5)

584

(69.3)

41
(75.9)

45

(60.8)

3

(6.0)

5

(17.9)

12
(14.8)

85
(55.6)

50

(23.5)

134

(41.9)

101
(24.0)
1.125
(46. 0)

(38.0)
(36.0)

4
(7.1)

5
(4.1)

4
(2.7)

5

(1.3)

61

(7.2)

(7.4)

29

(39.2)

(0)

1

(3.6)

(0)

19

(12.4)

(3.3)
19

(6.0)
13

(3.1)
161

(6.6)

(7.7)
(7.3)

2
(3.6)

2
(I. 6)

(0)

(0)

3
(0.4)

(0)

(0)

n

(0)

(0)

n

(0)

2

(l.,3)

2

(0.9)

3

(0.9)

(0)

12

(0..5)

(0.6)
(0.4)

limits.'
3H-lnch

limit."

I Minimum legal size 9 inches In 1927 and 1928 and 8H Inches in all oilier
years.
' As determined for 8M-inch limit for all years.

(table 22). However, such a small proportion
(5.2 percent) of the age group had attained legal
size (table 22) that age group III became strongly
dominant (75.9 percent) when only legal-sized
fish were considered (table 23). Of the 10 years
in which all or most of the yellow perch were
taken in autumn (1927, 1928, 1929, 1937, 1943-
48), after the continued growth of group-TI perch
had brought a greater proportion of them to legal
length, this group dominated the commercial
catch in all but 1929 and 1945. Since the condi-
tions are known to have been abnormal in 1929,
and perhaps also in 1945, it appears vaHd to con-
clude that age group II normally dominates the
late-season commercial catch. Members of the
same year class dominate the fishery as age group
III the following spring and during the summer
up to the point that the growth of the incoming
group II makes it possible for fish of that age to
assume a dominant position in the commercial
catch.

The conclusion about the change in the age
composition of the marketable catch within a
single season finds further support in data of the
1928 and 1929 collections. Scales were collected
in both summer and autumn of each of these
years. Comparisons of the percentage age com-
position of legal-sized perch in different months
of capture in the two years may be found in table
24. Analyses were made for the 1928 data with
respect to the then-effective 9-inch size limit and
the current 8K-inch limit. The data of table 24
cannot be considered descriptive of the typical
seasonal changes in the age composition of legal-
sized yellow perch since age group II was abnor-
mally abundant in 1928 and group III was excep-
tionally strong in 1929. The percentages serve,
nevertheless, to show clearly the tendency for
group II to replace group III in the marketable
catch as the season progresses. In 1928, age
group III was dominant among legal-sized j'cUow
perch in July (41.7 percent) but age group II
was dominant in the later months of the season.
Had an 8K-inch limit been in force, age group II
would have dominated the catch in July as well
as in late season, but its relative importance would
have increased, nevertheless, from 69.1 percent
in July to 91.1 percent in August to November.
The great abundance of group-Ill yellow perch
in 1929 made it possible for that age group to
maintain its dominance in the marketable catch

246

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Table 24. — Percentage age composition of legal-sized yel-
low perch in Lake Erie in different months of capture in
1928 and 1929

Age group

Size limit and month of capture

II

III

IV

V

1928:

9-inch size limit:

July

33.3

71.6

69.1

91.1

.8
14.4

31.6

41.7

27.7

21.4

8.6

8S.5
86.6

59.4

25.0

.7

9.5

.3

12.9

8.6

August through Novem-

8H-inch size limit:

July

August through Novem-
ber --

1929: 8}-^-inch size limit:

July

.8

August and September . .
November and Decem-

.4

to the end of the season. The representation of
age group II increased, however, from 0.8 percent
in July to 14.4 percent in August and September
and to 31.6 percent in November and December.
At the same time the corresponding percentage
representations of age group III changed from
85.5 to 85.6 to 59.4.

The legal-sized fish of the combined samples for
all years' collections belonged very largely (92.1
percent) to age groups II and III which were
represented almost equally — 46.1 and 46 percent
(table 23). However, the relatively high repre-
sentation of age group III can be traced to the
large 1929 collection in which it was dominant.
A more reliable estimate of the age composition
of the marketable catch may be had from the un-
weighted averages of the percentages for the
different years. At the bottom of table 23 these
averages are given as computed from the size
Hmits actually in effect in the different years (that
is, from a size limit of 9 inches in 1927 and 1928
and of SK inches in the later years) and as com-
puted from a size Hmit of 8K inches for all years.
The percentages computed from both the effective
and the 8K-inch size Umits showed dominance of
age group II.

Yellow perch older than age group V were not
found in the samples, but are known to have been
present in Lake Erie. Specimens selected because
of their large size revealed no males older than
age group IV, but did include one female of age
group VII and two fish of undetermined sex
assigned to age group VIII.

The data on the age composition of gill-net
catches (shoal and bull nets) contained in tables
25, 26, and 27 correspond to those already given

for trap nets. The data for 1927 and 1928 in-
cluded both legal- and iUegal-sized fish while
those for later years' represented only the com-
mercial sizes. Comparisons between the catches
of trap nets and giU nets bring out sharply the
strongly selective action of the latter gear. Age
group III dominated three of the four gill-net
collections obtained in 1927 and 1928 (table 25).
The fourth (the bull-net collection of 1928) was
dominated by age group II, but age group III was
only slightly less abundant. This distribution of
the age groups bears Uttle resemblance to the age
composition of the less-selective impounding nets
(table 21) where the 1927 samples were dominated
by age group I (48.9 percent), and 90.6 percent of
the yellow perch in the 1928 collections were
members of age group II. The 1927 gill-net
samples do not give the sUghtest indication of the
great abundance of age group I. Possibly the
dominance of age group II in the 1928 buU-net
collection was due to the great abundance of
group-II fish in that year. However, the shoal-
net collection failed to reveal such dominance and
abundance. On the whole, the age composition
of gill-net catches appears to be in large measure
independent of the relative strength of the age
groups in the population. Characteristically, age
group III was dominant, with age group II regu-
larly well represented and occasionally dominant.
The tendency for giU nets to take older fish than
do trap nets may be seen also in the greater abun-
dance of group-IV yellow perch in the gill-net
samples.

A second difference between gUl-net and im-
pounding-net collections lies in the greater pro-
portion of legal-sized yellow perch in the age groups
from the former gear (table 26). For example,
the percentages of legal yellow perch of group II,
in the impounding-net collections for 1927 and
1928, were only 15.1 and 12.4, computed from a
9-inch size hmit (table 22). Group II in the gill-
net collections for these years, on the other hand,
contained from 30.2 to 79.2 percent of such perch
and showed an average for the 2-year period (bull
and shoal nets combined) of 47.9 percent. If the
percentages of legal-sized yellow perch in age
group II are computed from a size limit of 8K
inches, the values are 39.7 for impounding-net
samples and 76.3 for gill-net collections. A
similar though less pronounced difference existed
between the percentages of group III legal-sized

YELLOW PERCH OF LAKB ERIE

T.\Bi,E 25. — Distribution by age groups of yellow perch from gill nets
[Percentages in parentheses]

247

Year

Month ot capture

Number of
specimens

Number and percentage

in age group—

I

II

III

IV

^

Taken in shoal nets:

1927

August.. --

July and August —

84
144

2
(2.4)

29
(34.6)

S3
(36.8)

40
(47.6)

73
(50.7)

11
(13.1)

17
(11.8)

2

1928

(2.4)

1

(0.7)

Total

228

2
(0.9)

82
(36. 0)

113

(49.6)

28
(12.3)

3

August

July and August

(2.9)

Taken in bull nets:

1907

69
133

24

(34.8)

63

(47.4)

38
(55. 1)

66
(42.1)

5

(7.2)

13

(9.8)

2

1928

(0.8)

(2.9)

Total - .

202

(0.5)

87
(43.1)

94
(46. 5)

18
(8.9)

2

August . .

(1.0)

Take of shoal and bull nets combined:
1927

153
277

2
(1.3)

1
(0.4)

53

(34.6)

116

(41.9)

68

(51.0)

129

(46. 6)

16
(10. 5)

30
(10. 8)

4

1928

.Tply find August

(2.6)
1

(0.4)

Total

430

3

(0.7)

169
(39. 3)

207
(48.1)

46
(10. 7)

5

(1.2)

Table 26. — Distribution by age groups of legal- and illegal-sized yellow perch from gill nets

IPercentages in parentheses]

Number of
specimens

Number
legal size

Number il-
legal size

Number and percentage in age group—

Year and minimum legal size

I

II

III

IV

V

Legal

Illegal

Ugal

lUegal

Legal

Illegal

Legal

Illegal

Legal

Illegal

Taken in shoal nets:
1927:

84

84

144
144

22s
228

69
69

133
133

202
202

430
430

72

78

101
136

173

213

64

68

75
101

139
169

312
382

12
6

43
9

55
15

5
1

58
32

63
33

118
48

(0)

(0)

2

(100.0)

2

(100.0)

19

(65. 5)

25

(86.2)

24

(45. :«

44
(83.0)

43

(52.4)

69

(84. 1)

19
(79.2)

23
(95.8)

19

(30.2)

37

(58.7)

38
(43.7)

60
(69.0)

81

(47.9)

129

(76.3)

10
(34.5)

(13.8)

29

(54.7)

9

(17.0)

39

(47. 6)

13

(15.9)

5

(20.8)

1

(4.2)

44
(69.8)

26
(41.3)

49
(66.3)

27
(31.0)

88
(52. 1)

40
(23.7)

40
(100.0)

40
(lOO.O)

60

(82. 2)

73

(100.0)

100

(88.6)

113

(100.0)

38
(100. 0)

33
(100.0)

43

(76. 8)

61

(91.1)

81
(86.2)

89
(94.7)

181
(87.4)

202
(97.6)

(0)

(0)

13

(17. 8)

(0)

13

(11.5)

(0)

CO)

(0)

13

(23.2)

5

(8.9)

13

(13. 8)

5

(5.3)

26

(12.6)

5

(2.4)

11

(100.0)

11

(100.0)

16

(94.1)

17

(100.0)

27

(96.4)

28

(100.0)

5
(100.0)

6
(100.0)

13

(100.0)
13

(100.0)

18
(100.0)

18
(100.0)

45

(97.8)

46

(100.0)

(0)

(0)

1

(5.9)

(0)

I

(3.6)

CO)

CO)

CO)

(0)

(0)

(0)

(0)

1

(2.2)

(0)

2
(100.0)

2
(100.0)

1
(100.0)

1
(100.0)

3

(100.0)

3

(100.0)

2
(100.0)

2
(100.0)

(0)

1928:

9 inches

(0)

8J^ inches

(0)

Total, 1927-28:
9 inches

(0)

(0)

2

(100.0)
2

(100.0)

(0)

SH inches

(0)

Taken in bull nets:
1927:

(0)

(0)

1928:

9 inches

(0)

(0)

(0)

(0)

(0)

(0)

1

(100.0)

1

(100. 0)

1

(100.0)

1

(100.0)

3
(100.0)

3
(100.0)

(0)

8^^ inches

Total, 1927-28:

9 inches

2
(100.0)

2
(100.0)

5
(100.0)

S
(100.0)

8H inches

(0)

Take of shoal and bull nets com-
bined:
9 inches

(0)

8H inches

(0)

(0)

248

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Table 27. — Distribution by age groups of legal-sized yellow
perch from gill nets, 1927-28 and 1943-48

[Percentages in

parentheses]

Number and percentage in

age

Year and minimum legal

Total
number

group—

size

I

II

in

IV

V

Period 1927-28:
1927:

130
146

176
236

312
382

CO)

(0)

(0)

(0)

(0)

(0)

(0)
(0)

6
(5.3)

(0)

1
(1.3)

1
(0.5)

9
(2.3)

(0)

38
(27.9)

48
(32.9)

43
(24.4)

81
(34.3)

81

(26.0)

129

(33. 8)

(26. 1)
(33. 6)

64

(56. 1)

42

(75. 0)

35

(47.3)

148

(71.5)

74

(19. 0)

170

(58. 4)

78
(57.4)

78
(53.4)

103
(58. 5)

124
(62.6)

181
(58.0)

202
(52.9)

(68.0)
(53.0)

34
(29. 8)

13
(23.2)

35
(47. 3)

48

(23. 2)

235

(60. 4)

103

(35. 4)

16
(11.8)

16
(11.0)

29
(16. 5)

30
(12.7)

45
(14.4)

46
(12.0)

(14. 1)
(11.8)

8

(7.0)

1

(1.8)

3

(4.1)

9

(4.3)

71

(18.3)

18

(6.2)

4

(2.9)

4

1928:

(2.7)

1

8J*> inches

(0. 6)
1

Total, 1927-28:
9 inches

(0.4)

5

(1.6)
5

Average percentage: •

(1.3)
(l.S)

(1.6)

Period 1943-48:

1943; 8H inches

1944: 8H inches

1945; 8V4 inches

1946; 8H inches

1947: Hi inches

1948: 8H inches

114
56
74
207
389
291

2
(1.8)

(0)

(0)

1
(0.5)

(0)

(0)

Total, 1943-48:

1,131

17
(1.6)

(1.6)

633
(47. 1)

(54. 6)

468
(41.4)

(36.6)

110
(9.7)

(7.0)

3

Average percentage: i
8H inches

(0.3)
(0.4)

Total, all years ' —
Average percentage: i
Effective limits

1,443

17

(1.2)
(1.2)

614

(47. 4)
(49.3)

649

(41.9)
(40.6)

155

(8.8)
(8.2)

8
(0.7)

8H-inch limit

(0.7)

1

1 Unweighted mean.

' Minimum legal size wis 9 inches in 1927 and 1928 and 8!-i inches in all
later years.

yellow perch in impounding-net and gill-net col
lections. The small numbers of specimens do not
warrant detailed comparisons of the remaining
age groups. Attention should be called to the
fact that in both 1927 and 1928 the samples taken
by gill nets did not contain fish caught as late in
the season as did those taken by impounding nets.
Consequently, the yellow perch taken by gUl nets
may be expected to have completed less of the
season's growth. Had the collections from both
types of gear been made at the same time within
the season, the advantage of the gill-net samples
with respect to the percentage of legal-sized yellow
perch in the age groups would probably have been
even greater.

Differences in the age composition of collections
from the two types of giU nets were not great,
although there was a slight tendency for bull nets
to take more of the younger fish (table 25) . The

only dominant group II occurred in the 1928 bull-
net collection, and when the data for 1927 and 1928
are combined, bull nets may be seen to have taken
relatively more fish of age group II than did shoal
nets and relatively fewer of the older age groups.
Likewise, the differences in the proportion of legal-
sized yellow perch in corresponding age groups of
shoal-net and bull-net collections were not large.
The best represented age groups (II and III) of
the shoal-net samples contained shghtly higher
percentages of legal-sized fish than the same age
groups in buU-net samples.

The data on numerical and percentage age
composition of the legal-sized yellow perch taken
by gill nets are presented in table 27 with the
catches of shoal and bull nets combined. Added
to the 1927 and 1928 data are those obtained from
samples of the commercial catch by gill nets in
1943-48. Age group III dominated the samples
in both 1927 and 1928 and made up 58 percent of
the total at the then-effective size limit of 9 inches
(53 percent at the present 8K-inch size limit).
Age groups II and JV made up 26.1 and 14.1 per-
cent (33.6 and 11.8 percent at the 8K-inch limit)
and formed the only other well-represented groups
in the catches. Age group I was not represented
at all. The 1943-48 data differed from those of
the earlier years in that age-group-II fish domi-
nated in 4 years, age groups II and III were equally
represented in one, and age group III was domi-
nant in only 1 year. The averages for the 6 years
(comparable to the averages at the 8j2-uich size
limit m 1927-28) showed that group II made up
54.5 percent of the total, group III 36.5 percent,
group IV 7 percent, and group 11.6 percent. Thus
it is seen that there was not only a shift in domi-
nance from group III m 1927-28 to group 11 in
1943^8 but also an accompanying decrease in the
relative abundance of the fish in groups IV and V
and an increase in the number of those in group I.

Explanation of the difference in age composi-
tion of the legal-sized yellow perch taken by gill
nets in 1927-28 and 1943-48 probably hes in the
time of year the fish were captured. All of the
1927-28 samples were collected in July and Au-
gust whUe those for 1943-48 were taken from late
September to early November. The samples ob-
tained in July and August (1927-28) unquestion-
ably were made up of fish that had not completed
the season's growth, whereas those taken later in
the year (1943-48) could be expected to have

YELLOW PERCH OF LAKE ERIE

249

completed, or nearly completed, growth for the
year. The continued growth, especially of the
age group just entering the commercial fishery in
large numbers (group II) can be expected to in-
crease the relative abundance of the j^ounger indi-
viduals among the legal-sized fish. The belief
that the time of capture in a year explains the
shift of dominance from group III to group II is
supported by the strikingly similar changes found
in the impouncUng-net data.

If the data for impounding and gill nets are
considered together, it may be stated that the
fishery is supported chiefly by age groups II and
III. Age group III dominated the commercial
catch of gill nets in late summer of both 1927 and
1928. The same age group is in all probability
usually dominant in the earh-season catches also.
The late-season (late September to early Novem-
ember) commercial catches by gill nets were dom-
inated by age group II in 4 of the 6 years 1943^8.
Age group III dominated the late-season giU-net
catches only once (1947) and age groups II and
III were of equal abundance in 1945. The com-
mercial catch of impounding nets appeared to be
dominated by age group III in the spring and
during at least part of the summer. As growth
during the summer brings an increasing percent-
age of age group II to legal size this age group
assumed a more important position in the catch.
Dominance by age group II seems to be character-
istic of late-season impounding-net catches, al-

though there may be exceptions, as in 1929 and
1945, when age group III may be the stronger.

The dependence of the fishery on two age groups
renders the abundance of the Lake Erie perch
very sensitive to natural fluctuations in the
strength of year classes and vulnerable to over-
fishing. The small quantity of fish of commercial
size that is carried over from one year to the next
makes the maintenance of protective measures to
ensure an adequate stock of spawners at all times
highly imperative.

The percentage representation of the year classes
in each year's collection of j^ellow perch from im-
pounding nets in Lake Erie is recorded in table
28. The data for the 1937 collection have been
omitted because of the long time interval separat-
ing this sample from the earUer collections. Dis-
cussion of the year-class composition of the 1937
samples will be based on the age-composition
data of table 21. No tabulation has been pre-
sented of the year-class composition of gill-net
samples because of the highly selective action of
that gear.

The inability of impounding nets to retain repre-
sentative samples of the j'ounger age groups, and
the rapid rate at which year classes disappear from
the fishery owing to the short life span, combine
to make interpretation of data on the year-class
composition of the samples most dLSicult. Age
group (first year of life) is of course absent from
all collections, and normally group-I fish occur

Table 28. — Occurrence of year classes of yellow perch in the catch of impounding nets of Lake Erie

Asterisk designates dominant year class each year; roman numerals show age at capture]

PART I-PERCENTAGE BASED ON ALL FISH TAKEN

Year of capture

Year class of—

1922

1923

1924

1925

1926

1927

1928

1929

1930

1927..

0.4 V

1.0 IV

9. 8 III
.5 IV
.3 V

39. 9 II
7. 6 III
5.3 V

•48. 9 I
•90. 6 II
•54. 9 III
1.8 IV

1928-

1.2 I
32. 3 II
20. 3 III

1929

7.2 1
•77. 5 II
24. 8 IV

1930-

0.4 I
•73.7 III

1932

1.6 n

PART n— PERCENTAGE BASED ON COMMERCIAL CATCH

Year of capture

Year class of —

1939

1940

1941

1942

1943

1944

194S

1946

1947

1943

3. 6 IV

17.9 111

•57. 1 II
14.8 III
12.4 IV
.9 V

21.4 I
•85. 2 II
•5.5. 6 III
3.3 IV
.9 V

19J4

1945 :..

1.3 V

30. 7 II

23.6 111

6.0 IV

1946-

•72.3 11
41.9 III
3.1 IV

'"""•sirg'ii"

24.0 III

b'.i'i"

•71. 2 II

1947

1948-.-

1.7 1

250

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

only in small numbers. Age group II is affected
less by the selective action of the gear although
many fish of this age seem to be too small to be
retained in the nets in spring and early summer
(p. 221). It appears, then, that estimates of the
relative abundance of the year classes of the Lake
Erie perch must be based chiefly on the represen-
tation of the older fish in the different years'
samples. The relative strength of age group II
may be considered significant only if the sample
was taken late in the season. The scarcity of
group-I fish cannot be held to indicate a weak
year class, although a great abundance of yellow
perch of this age may be considered evidence of
a strong one.

Ordinarily the estimate of the strength of a year
class is based on a knowledge of its relative
abundance in the collections of several successive
years. In the Lake Erie yellow perch, however,
the great scarcity of all fish older than age group
III, together with the unrehability of data on the
abundance of the younger age groups, makes the
application of this method very difficult. Further
complications arise from the failure to obtain
data in 1938 and 1939, and the fact that only the
legal-sized fish were sampled in 1943-48.

Because of the limitations just outlined it is
not possible to make a precise arrangement of the
year classes of the Lake Erie yellow perch in the
order of their abundance. In fact it is possible
to speak with certainty concerning only one of
them — the year class of 1926. This year class
was without doubt one of exceptional strength.
It dominated the impoimding-net collections of
three successive years, 1927, 1928, and 1929.
Dominance of this year class as group I and as
group III is particidarly significant. The only
dominant group I of the collections occurred in
the 1927 samples. In the remaining collections,
age group I made up no more than 7.2 percent of
the samples except in 1937 and 1943. Age group
III was dominant in the late-season collections of
both 1929 and 1945. It should be pointed out
further than in 1928 the 1926 year class provided
relatively the strongest group II in any of the
collections (90.6 percent of the total).

Three other year classes appeared to have been
of more than ordinary strength. The 1936 year
class as grouji I made up 47.3 percent of the entne
1937 sample (table 21). The only other collec-
tion with such an abundance of group-I fish was

made in 1927 when the 1926 year class dominated
the catch of impounding nets. Unfortunately, no
samples were obtained in either 1938 or 1939 and,
as a consequence, nothing is known of the strength
of the 1936 year class at the ages when they would
contribute most to the fishery. However, produc-
tion increased from 3,305,000 pounds in 1936 to
7,782,000 pounds in 1938 when the 1936 year class
would have entered the commercial fishery in
greatest numbers. A large increase in yield is to
be expected when a strong year class enters the
fishery, and the 236-percent increase from 1936 to
1938 in the catch of yellow perch may be taken as
evidence, if not proof, that the 1936 year class was
of more than ordinary strength. The sharp decline
to 3,015,000 pounds in 1939 in the take of yeUow
perch could mean the exhaustion of an abundant
year class by an intense fishery.

Despite the fact that the evaluation of the
strength of year classes in the 1943-48 period is
handicapped by lack of knowledge of the abun-
dance of group-I fish in those years, itseems evident
that the 1942 year class was one of considerable
size. It comprised 21 .4 percent of the 1943 samples
as age group I. The same year class was strongly
dominant as group-II fish in 1944 (85.2 percent)
and continued to dominate the commercial samples
as age group III in 1945 (55.6 percent). The
strong representation of the 1942 year class as
group-I fish in the commercial yield in 1943 and
the dominance of the group in the two succeeding
years could have been accomplished only by re-
markably good survival.

Evidence, less convincing but nevertheless
strongly suggestive, points to 1944 as having pro-
duced a year class that was stronger than that
of either 1943 or 1945. The 1944 year class as
group-II fish made up 72.3 percent of the 1946
commercial samples and contributed heavily (41.9
percent) to the 1947 take when they were in age
group III.

The 1943-48 data from gill nets (table 27)
provide some evidence of the relative strength of
year classes despite the fact that these nets are
highly selective and the samples were taken from
the legal-sized yellow perch. Age group III made
up 47.3 percent of the legal-sized fish in 1945 and
equaled the abundance of group II. This high
relative abundance of age group III supports the
conclusion reached from the trap-net data that
the 1942 year class was of more than ordinary

YELLOW PERCH OF LAKE ERIE

251

strength. Although the fish assigned to age
group III dominated the late-season commercial
catch of yellow perch by gill nets in 1947, the
evidence that the 1944 year class was exceptionally
strong is not conclusive. As group-II fish the
1944 year class strongly dominated (71.5 percent)
the commercial catch in 1946 and exliibitcd the
second-strongest dominance in the 6-year period
1943^8, hut the class appeared sparingly (1.:?
percent) as age group I in 1945. Data from the
gill nets add strength to the suggestion based on
trap-net catches that the year class of 1944 was
stronger than that of either 1943 or 1945.

The occurrence of rather wide fluctuations in
the abundance of year classes has been observed
in a large number of species, both marine and
fresh-water. Despite the extensive studies that
have been made of the fluctuations in abundance
of year classes, relatively little is known concerning
the imderlying causes. It is agreed rather gen-
erally, however, that the fluctuations "have their
origin in certain conditions prevailing at a very
early period in the fife of the fish" (Hjort 1914).
The belief is general also that fluctuations depend
on variations in meteorological-hjdi-ographical
conditions, although biological conditions (for
example, competition for food among the young
and increase in predators) may at times be
important."

Under conditions of a stabilized fishing inten-
sity, it is believed that the causes of fluctuations
in the abundance of year classes in the fishes of
Lake Erie are most probably to be found in the
meteorological-hydrographical conditions. It is
recognized that overfishing and other factors also
may be involved. The simultaneous occurrence
in 1926 of a strong year class in seven species
strongly suggests that competition for food among
the young is not normally a limiting factor. The
comparatively low yield of the fishery in 1926, a
year that produced a strong year class, indicates
that as long as the population is maintained at a
reasonable strength the number of spawners may
not be the primary determining factor.

The weather records from the Sandusky, Ohio,
station of the U. S. Weather Bureau (1919-48)
have been examined in an effort to detect a
possible correlation between weather conditions

■> Jensen (1933) gave a detailed review of the literature and a critical dis-
cussion of the causes of fluctuations in the abundance of marine fish of the
North Sea and neighboring waters.

and the strength of the year classes. It has been
assumed that conditions in 1926 and 1942 and
probably in 1936 and 1944 were exceptional as
those years produced the strongest year classes
of 3'ellow perch found within the data, and that
the causes for the strength of those year classes
should be found in the extent and manner in
which the meteorological conditions of those j^ears
(lifTered from other years. It was expected
further that conditions would be more comparable
in the years 1926 and 1942 than in any other j'ears.

Because of the previously mentioned impossi-
bilit}' of evaluating accurately the strength of each
j-ear class it is possible to speak only in general
terms concerning the effects of weather, hence
detailed weather data will not be presented. The
temperature data that were examined referred to
air temperatures. As mentioned previously, trends
in air temperatm-e no doubt indicate approximate
trends in water temperature, especiafly in such
shallow water as is found in western Lake Erie.
It was found that the winter of 1925-26 (Novem-
ber to February) was cold and that the following
prespawning period (March and April) was the
coldest for the years 1919 to 1948. However,
both the winter of 1941-42 and the prespawning
period in 1942 were warmer than average. The
2 years probablj^ producing strong jear classes
(1936 and 1944) differed m that the winter of
1935-36 was exceptionally cold and that of 1943-44
was warmer than average. The prespawning
period in 1936 had above average temperatures
but in 1944 temperatures were below average.
In other months of the year temperature exhibited
no relation to the strength of the year classes.

Although all of the 4 years that apparently
produced strong year classes had less than average
rainfall in May and June, the total precipitation
in both 1942 and 1944 was only slightly below
normal and amounted to between two and tliree
times that in either 1926 or 1936. Wind velocities
and percentage of possible sunshine appear to bear
even less relation to the strength of year classes
than the other factors considered. Van Oosten
(1948) pointed out that there was no relation
between turbidity and strength of year classes.

The contradictory evidence of the effects of
temperature during the winter and prespawning
period and total precipitation during May and
June on the strength of year classes makes it
appear that no siinjile n^lation exists. Although

252

FISHERY BULLETIN OF THE FISH AND "WILDLIFE SERVICE

extremely high or low temperatures and severe
storms may lead to catastrophic destruction of
eggs and small fish, the strength of a year class is
believed to depend normally on the sum of the
effects of many factors. It seems entirely reason-

able to suppose that the controlling factors have
to do with the coincidental occurrence of early
feeding by the newly hatched fish and the appear-
ance of suitable food organisms in adequate
amounts.

LENGTH-WEIGHT RELATION

The mathematical relation between length and
weight of the yellow porch of Lake Erie in 1927-37
was determined by fitting the equation W=cL"
to the average empirical length and weight of each
5-mm. standard-length frequency interval over
the range 106 to 250 mm. (5.0 to 11.4 inches total
length) . Length intervals both longer and shorter
than this range contained less than 28 fish each
and were not employed in the fitting of the equa-
tion because of possibly unreliable averages. The
data represent all yellow perch with standard
lengths of 106 to 250 mm. that were measm-ed and
weighed without regard for locality, sex, season
and year of capture, or gear employed. Data on
the length and weight of Lake Erie yeUow perch
in 1943—48 are not included because analysis of
these later data showed them to be similar in every
respect to those obtained during the earlier years.
The equation derived from the 1927-37 data ap-
phed equally well to the 1943-48 material.

The equation that best describes the length-
weight relation of the Lake Erie yellow perch is:

W=1.766X10-'D'"',

in which PF= weight in grams, and L= standard
length in millimeters. Since n=3.015, it may be
said that the weight of the yellow perch in Lake
Erie increased approximately as the cube of the
length (n=3.0).

Table 29 shows the actual and calculated weights
for each 5-mm. interval of standard length of the
yellow perch of Lake Erie from 1927 to 1937.
Weights were computed both from the cube rela-
tionship and from the more general equation (W=
ci"). It was found that weights calculated by the
general equation agreed closely with those com-
puted by the equation IF=1.91X10"'Z^ (The
weighted grand average K for all Lake Erie yellow
perch was 1.91.) Weights calculated by the two
equations were in complete agreement for all but 6
of the 31 frequency intervals for fish with standard
lengths of less than 236 mm., and in no interval
differed by more than 1 gi-am. The weights com-

puted by the two equations agreed at no lengths
greater than 235 mm. The weights of these larger
yellow perch calculated from the cubic relationship
were always less than those computed from the
more general equation but at no length was the
difference between the two calculated weights
greater than 4 grams. It is true also that the
differences between the two corresponding calcu-
lated weights tended to increase progressively as

Table 29. — Actual and calculated weights of Lake Erie
yellow perch by 5-millimeter length intervals

[Data based on all flsh weighed during the investigation)

Standard-length
interval >

Total
length

Number
offish

Average
actual
weight

Average weight
calculated from
equation—

n=cL"

W=KX

10-Si5

83 mm

Inches
3.9
4.1
4.4
4.6
4.8
.5.1
5.3
5.5
.5.8
6.0
6.2
6.4
6.6
6.8
7.1
7.3
7.6
7.8
8.0
8.2
8.5
8.7
8.9
9.1
9.3
9.5
9.8
10.0
10.2
10.4
10.6
10.8
11.1
11.3
11.5
11.7
12.0
12.2
12.4
12.6
12.9
13.1
13.3
13.6
13.8
14.0

1

Grams
7

Grams
11
13
15
18
21
24
27
31
35
40
45
.50
56
62
68
75
82
90
99
108
116
127
137
148
160
172
185
198
212
227
242
258
275
292
310
329
349
369
390
412
436
469
483
508
535
562

Grams
11

88 mm

13

93 mm - -

I

1

8

28.

52

53

58

76

93

144

281

431

513

751

992

1,161

1.275

1,463

1,633

1,844

1,997

2,252

2,124

1,845

1,531

1,066

681

399

166

113

66

34

5

7

1

5

1

21
21
21
24
26
29
35
40
45
61
58
64
69
77
83
91
98
108
117
126
137
149
162
174
186
200
213
227
240
255
266
282
304
334
312
349
404

15

68 mm

IS

21

24

113 mm

28

31

123 mm

36

128 mm

40

133 mm

138 mm - .

45
50

143 mm

56

62

153 mm

R8

75

83

168 mm

91

173 mm

99

108

183 mm

117

1S8 mm -

127

193 mm

137

198 mm

148

160

172

213 mm

185

198

223 mm

212

226

233 mm

242

238 mm

257

274

248 mm

291

309

258 mm

328

347

268 mm

368

273 mm

389

410

283 mm

3
2

418
524

433

456

480

1

476

605

631

658

' In 5-mm. intervals.

YELLOW PERCH OF LAKE ERIE

253

the standard length of the fish increased above
270 mni.

A comparison of the average actual weights
with the calculated weights shows that there was
excellent agreement over most of the length
range for which there were large numbers of fish.'*
Over the standard length range of 103 to 238 mm.
the actual weights at no point disagreed with
either of the computed weights by more than 3
grams. It is apparent also that calculated weights
obtained by the two equations agreed almost
equally well with the average actual weights over
this length range. The lack of agreement between
the observed weights and the computed weights
of perch with standard lengths less than 103 mm.
may be due to the small number of specimens of
that size. The empu'ical weights were somewhat
less than either calculated weight at all but three
of the lengths greater than 238 mm. (intervals
with midpoints at 258, 273, and 288 were the ex-
ceptions). Over this range, the weights calcu-
lated on the basis of the cubic relationship were
ordinarily closer to the observed weights than
were those calculated from the more general
equation. The fact that the actual weights of the
larger fish were usually less than the computed
weights may indicate that both equations fail to
fit the data exactly for standard lengths greater
than 238 mm., or it may be due to the small
number of individuals in most of the frequency
intervals. Another possible explanation of the
lower actual weights at lengths greater than 238

» The average actual weights are the averages of all flsh in each 5-mm.
interval. Only the midleagth of each interval is shown in the table.

mm. is that the gill nets selected only the lighter
of the longer fish.

The weights calculated from the length-weight
equation, >F= 1.766 XIO"'!.'"", are shown graphi-
cally in figure 10. The use of two scales permits
ready conversion from metric to English units of
weights and measures. The factors needed most
frequently for conversions between standard, fork,
and total lengths are shown in table 30. It was
mentioned (p. 252) that intervals of standard length
that contained less than 28 fish were not used in
the determination of the general length-weight
equation. Hence, the points on the curve that
he below 106 mm. and above 250 mm. are outside
the range to which the cui-ve was actually fitted.
However, the closeness with which the extra-
polated portions of the curve (shown by broken
hues) fit the average actual weights based on few
specimens indicates that, in spite of the discrep-
ancies already mentioned, the curve is for practi-
cal purposes applicable to the length-weight rela-
tion over the entire range represented.

COEFFICIENT OF CONDITION (K)

The condition of fishes and fluctuations in the
values of the coefficient of condition (K) involve
problems that are distinctly different from the
description of the general length-weight relation
(see Hile 1936, for detailed discussion). Condi-
tion, or relative heaviness, is influenced b}' those
physiological and environmental factors that
affect the general well-being of the individuals.
The present data permit a description of the fluc-

Table 30. — Factors for conversions between standard, fork, and total lengths of Lake Erie yellow perch
[Number of specimens employed to determine values of the factors are shown in parentheses]

Factors to be employed for standard lengths of—

Conversion of—

80 mm. and
under

81 to 130 mm.

131 to 190 mm.

191 to 220 mm.

221 mm. and
over

Standard length to total length (same unit of measurement)

1.215
(87)

.0478
(87)

1.193

(112)

.0470

(112)

1.141

(5)

.0449

(5)

.838

(112)

21.285

(112)

.956

(5)

.876

(5)

22.250

(5)

1.046

(5)

1.174
(648)

.0462
(648)

1.132
(285)

.0446
(285)
.852
(648)
21.641
(648)
.964
(285)
.883
(285)
22.428
(285)

1.037
(285)

1.165

(1.267)

.0459

(1.267)

1.125

(591)

.04(3

(591)

.858

(1.267)

21.793

(1. 267)

.966

(591)

.889

(691)

22.581

(591)

1.035

(591)

1.156

Standard length in millimeters to total length in inches..

(513)
.0455

(513)
1.119

Standard length in millimeters to fork length in inches

(0)

(131)
.0441

(0)

.823

(87)

20.904

(87)

(131)
.865

Total length in Inches to standard length in millimeters

(513)
21. 971

(513)
.968

Fork length to standard length (same unit of measurement) _. .

(0)

(131)
.894

Fork length In inches to standard length In millimeters

(6)

(131)
22.708

Fork length to total length (same unit of measurement)

(0)

(131)
1 033

(0)

(131)

254

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE
TOTAL LENGTH IN INCHES
3.5 4.5 5.5 6.5 7.5 8.5 9.5 10.6 11.5 12.5 13.5 14.5

2

IS

I e

14

W

kJ

O '2

z

o

2 10

I-
X

o

)>

• /

/ L

/

/

/.
/
/
/.

•

/
/
/•

/

/

/

/

/

/

7

>

X

^

/

JL

•

r 1

75 100 125 150 175 200 225 250 275

STANDARD LENGTH IN MILLIMETERS

3

5 5

50

450

400

35

3 00

250

200

I 50

1

5

<

a:
O

I

32 5

FinuRE 10. — Relation between length and weight in yellow perch of Lake Eric. Solid portion of the curve represents
length range to which equation W^cL" was fitted; broken lines represent the curve in length ranges not well repre-
sented in the data. Dots show averages of empirical data grouped into 5-nim. length intervals.

tuations in the coefficient of condition (K) of the
Lake Erie yellow perch according to month of
capture, sex and maturity, state of gonads, age,
length, and type of gear employed. The data
obtained from samples taken in the period 1943-48
will be omitted from this discussion since they
contribute nothing new and would bring about no
important changes in the conclusions.

Monthly and annual fluctuations in the value of K

Among the factors that might be expected to
influence monthly variations in /t are food, degree
of activity, and stage of sexual maturity. Spawn-
ing, and the preparatory sexual development,
may be expected to produce the greatest changes
in condition. Description of the montlily and
annual fluctuations in the value of K in the Lake

YELLOW PERCH OF LAKE ERIE

255

Erie 3'el]osv perch is based entirely on specimens
taken from impounding nets since, as will be
shown later (p. 258), the type of gear employed
influences the average value of K and gill nets are
particularly selective in this respect.

Sex and stage of maturity wei-e shown by sepa-
rate analyses to have had very little effect on the
value of K except in the spawniing period. The
data in table 31 showing the montldy fluctuations
in condition of Lake Erie yellow perch according
to year of capture therefore, include individuals
for which sex or stage of maturity was not re-
corded. The data from samples obtained during
April 1932, October 1934, and November 1937
are not shown in the table because each of those
years was represented by only 1 month. The
values of /v for these 3 months were 2.24 (133 fish),
2.24 (207 fish), and 2.18 (131 fish), respectively.

Annual fluctuations in condition and differ-
ences with respect to the months represented in
the various years' collections place limitations on
the conclusions to be drawn from the data of table
31. Nevertheless, certain trends can be detected.
It is obvious, for example, that perch tend to be
in better condition in midsummer and late summer
than in June. This is brought out by the follow-
ing tabulation of the unweighted averages of K
for corresponding months of 1928 and 1929:

Average K

September 1 . 96

October 1.92

Ax'eruge K

June 1.80

July 1.97

August 1.98

November 1. 87

The montlily averages for the 2 years show a
great improvement in condition from June to
July. Condition remained good in August and
September. The average K decreased shghtly
in September and undei-went a greater decrease
in October and November. The averages in
table 31 show that the October-November decline
was much more pronounced in 1929 than in 1928.

The averages for September, October, and
November, 1927, suggest that loss of condition
in tlie autumn may not be typical for the Lake
Erie perch. In 1927 the value of iiC increased in
both October and November. The averages for
the 1930 collection, on the other hand, agreed with
the trend of the 1928-29 averages. In 1930 the
value of K increased markedly in July and re-
mained at a high level in August and September.
The only available comparisons of the averages
of A' for November and December (1929) indicate

Table 31. — Monthly values of K (condition) of Lake Erie
yellow perch taken in impounding nets, 1927-30

Month

April

May

June.-

July___

August

September.

October

November.
December. .

.\verape. all months...

.\verage, excluding

April and May

1927

125
895
496

1,616
1,516

1.87
1.91
2.01

1928

1929

I"

429
664
504
132

510
162
458
264

3,123
2,030

>^

1.78
1.76
1.81
2.06
2,04
2.00
1.9»
1.

1,
1.96

aS.

3,122

1,841

2,747

1.820

451

126

691

417

11,215

8,093

So

1.84
1.78
1.88
1.92
1.93
1.86
1.78
1.88

1.85

1.

41
5
173
25
25

269
228

1.85
1.81
2.31
2.34
2.33

2.24
2.30

an improvement in condition m the latter month.
Three comparisons are available of condition in
May and June and one of condition in April and
May. However, the possible distm-bing effects
of variations in the relative abundance of giavid
and spent fish in the various AprU and May
collections make it inadvisable to draw con-
clusions concerning montlily changes in condition
from April to May and from May to June.

The grand averages for K in the different
years' collections are not strictly comparable
because of dift'erences from year to year in the
months represented. A more reliable estimate
of the annual fluctuations in condition may be
had from comparisons of averages for correspond-
ing months. Comparisons of the averages for
September, October, and November indicate
that condition was slightly better m 1928 than in
1927. The large 1928 advantages in September
and October overshadowed the 1927 advantage
in November. Condition was poorer in 1929 than
in 1928. The K averages were lower in 1929 in
every month except May. The condition of the
Lake Erie perch in 1929 was also proliably poorer
than in 1927. The September average was higlier
in 1929 than in 1927, but the October and Novem-
ber averages were both higher in 1927. The
best condition of the 4 years occurred in 1930.
With the exception of June which had the same
K averages in 1928 and 1930, the montlily averages
in 1930 were consistently greater tlinn the cor-
responding averages in any other year. From
the data just discussed it would appear that the
probable order of the 4 years with respect to
condition of the Lake Erie yellow perch from

256

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

best to poorest condition is: 1930, 1928, 1927, and
1929.

The K averages of 2.24 in April 1932 and
October 1934, and 2.18 in November 1937 (p. 255),
suggest that the condition of the Lake Erie yellow
perch in these 3 years was excellent — probably
superior to that in 1927, 1928, and 1929.
Fluctuations in value of K with stage of maturity

Great differences in value of K associated with
stage of maturity were foimd in the comparison
of the gravid and spent females taken in May.
(Unfortunately, gravid and spent males were not
recorded separately in the field records.) The
detailed information on the loss of weight by
the females at spawning is presented in table 32
where the data have been arranged to show the
average weight in grams and the average K before
and after spawning for each 5-mm. standard-
length interval. For both gravid and spent
females the changes of K with increase in length
appeared to be random rather than to exhibit a
progressive increase or decrease. Consequently,
there was no obvious relation between the per-
centage loss of weight and the length of the speci-
mens. The loss of weight varied from 3.4 to
24.6 percent. The average of the percentages
computed from the best-represented intervals,
those in which both gravid and spent fish were
represented by seven or more specimens, showed
a weight loss of 16.1 percent at spawning. A
slightly lower estimated loss of weight (15.5 per-
cent) was obtained from the weighted-average
coefficient of condition.

Fluctuations in value of K with age

Data for the study of the variations of K with
age are given in table 33. To avoid the distorting
effects of monthly and annual variations in con-
dition, averages are given for each month's col-
lection of each year. Since sex and stage of matu-
rity have little influence on the value of K in the
summer and autumn, the data include all the fish
whose ages were determined. The data of table
33 do not point toward any dependence of condi-
tion on age. It is true that in 7 of 10 comparisons
fish of age group II had lower average coefficients
of condition than those of age group I. This
difference can be explained, however, as the result
of gear selectivity. Since the group-I fish were
near the smallest size that could be retained by
the impounding nets it is readily conceivable that
only the heavier individuals of that age group
were retained. There is less indication that gear
selectivity affected the K values of age groups II
and III although numbers of the group-II yellow
perch were below the theoretical maximum length
of escape (170 mm.). Gear selection possibly
may account for the fact that group II had the
larger average Kin 9 of 10 comparisons for months
earlier than October (see p. 221). In the later
months, after group II has practically completed
the third season of growth, age group III had the
higher K values in all 7 comparisons (October,
November, and December). Comparisons of age
groups III and IV reveal that the former had the
higher average K 6 times whereas the latter had
the higher value 2 times. The two age groups

Table 32. — Comparison of average weights and condition (K) of gravid and spent female ijellow perch taken by impounding

nets in Lake Erie, May 1929

(Number of specimens in parentheses]

Average total
length

Qravid females

Spent females

Loss of weight

Average weight

K

Average weight

K

at spawning

166 to 170 mm

Inches

7.8
8.0
8.2
8.5
8.7
8.9
9.1
9.3
9.6
9.8
10.0
10.2
10.4
10.6
10.8

OraTTW
89 (3)
122 (5)
115 (10)
128 (29)
138 (68)
148 (82)
161 (90)
172 (100)
186 (90)
200 (40)
211 (42)
232 (26)
246 (14)
261 (6)
291 (1)

1.89
2.36
2.05
2.08
2.08
2.06
2.08
2.05
2.06
2.07
2.04
2.09
2.08
2.06
2.16

2.07 (696)

arama
86 (10)
92 (20)
99 (24)
109 (52)
118 (75)
125 (101)
135 (107)
147 (92)
157 (77)
167 (48)
175 (39)
181 (7)
214 (5)
232 (3)
230 (4)

1.82
1.78
1.76
1.77
1.78
1.74
1.74
1.76
1.76
1.73
1.69
1.63
1.81
1.83
1.71

1.75 (664)

Percent

3.4

171 to 176 mm.. ...

24.6

13.9

181 to 185 mm . _ . .

14.8

186 to 190 mm

14.6

191 to 195 mm -

16.5

196 to 200 mm

16.2

201 to 205 mm

14.6

206 to 210 mm...

15.6

211 to 215 mm

16.5

216 to 220 mm...

17.1

221 to 225 mm

22.0

226 to 230 mm... ..... ...

13.0

231 to 235 mm

11.1

236 to 240 mm...

20.7

16.1

' Unweighted mean, based on those length intervals in which both gravid and spent fish are represented by at least 7 individuals.

YELLOW PERCH OF LAKE ERIE

257

The range of fluctuation of K for the age groups
of Lake Erie yellow perch extended from 1.72 to
2.61. The individual yellow perch were found to
have values of K ranging from 1.13 to 3.23, with
the average 1.91. Comparisons of these values of
K with those found in other waters of the Great
Lakes reveal that the yellow perch of Lake Erie
were a little heavier than the ones in Saginaw Bay
(Hile and Jobes 1941), about equal to those in
Green Bay, and somewhat more slender than the
yellow perch in northwestern Lake Michigan (Hile
and Jobes 1942).

Influence of rate of growth on value of K

The possibihty that the values of K of the age
groups were influenced by varying proportions of
faster or slower growing individuals has been in-
vestigated. Table 34 permits comparisons of K
for yellow perch of the same length but of different
ages and for fish of different lengths but of the
same age. All comparisons have been limited to
fish collected in the same year and month. The
data have been limited further to the 1927 and
1929 collections from trap nets since those collec-
tions had the most suitable distribution of the age
groups, that is, contained adequate samples from
more than one age group. It may be seen that
there were no consistent differences between the
values of K for fish of the same length but different
age. In other words, neither the older (slow
growing) nor the younger (rapid growing) yellow
perch maintained a consistent advantage. This
indication that individual growth rate did not
influence individual condition is supported by the
fact that the longer (more rapid growing) indi-

Table 34. — Comparison of condiiioti (K) in Lake Erie yellow perch at different ages and lengths taken by trap nets

[Number of specimens in parentheses]

had the same values in November 1927. Only
three comparisons were available between age
groups IV and V, and in each the older age group
had the lower K. In general, fluctuations of K
with age may be considered random among all
age groups in which gear selectivity is absent or
unimportant, although there was a tendency for
a progressive decrease ^vith age during the period
April to September. It may be justified to con-
clude, however, that generally condition is inde-
pendent of age in the Lake Erie yellow perch.
No computation was made of average values of K
for all data combined since the combined effects
of monthly variations and of variations in the
numbers of specimens would cause these averages
to be of little significance.

Table 33. — Coefficient of condition (K) of Lake Erie yellow
perch according to age, month, and year of capture

[Number of specimens in parentheses]

.Month and year

Age group

I

II

in

IV

V

April: 1932 . -

2. 35 (2)

2.05 (107)
2.0O (13)
2.51 (128)

2.07 (393)
1.91 (29)
2.32 (23)

2.26 (98)

1.85 (21)
1.90 (131)
2.16 (40)

2.14 (14)

1.86 (32)
2. 14 (2)

1.94 (10)
2.05 (136)
2. 12 (3)

1.93 (28)
2. 05 (9)

2.08 (19)
2 02 (16)
1.84 (218)
2. 15 (3)

1.94 (115)

2.23 (33)

1.93 (4)
1.82 (16)
2.13 (4)

July:
1928

1929 - -

1.72 (1)

1930 —

August:

1928 —

2.61 (7)
2. 05 (7)

1929

1930

September:
1928

2.00 (148)
2. 16 (22)
2.41 (21)

1.89 (61)
1.96 (61)

1.92 (129)
1.99 (123)
1.79 (170)
2.07 (66)
1.91 (138)

1929

2.01 (6)
2.38 (1)

1.90 (74)

1930

October:

1927

1.96 (4)
2.02 (1)

2.08 (1)

1.91 (2)

1928

November:

1927

2.01 (161)
1.99 (4)
1.87 (28)
2. 30 (62)
1.93 (42)

1928

1929

1.80 f33)

1.78 (2)

1937

1.93 (12)

Average total
length

Value of ifin-

Standard-length interval

October 1927

November 1927

November 1929

December 1929

I

II

I

II

II

lU

II

III

121 to 130 mm

Inehet
8.9
6.3
6.7
7.2
7.6
8.1
8.6
9.0
9.4
9.9
10.3
10.7
11.2
11.6

1.67 (1)

1.96 (1)
1.98 (6)
2. 02 (27)
1. 99 (31)
2.01 (59)
1. 96 (34)
1.91 (2)
1.94 (1)

3.23 (1)

131 to 140 mm

1.71 (4)

1.79 (7)
1.95(17)
1.87(26)
1.87(16)

1.80 (5)

141 to 1 SO mm

1.71 (3)
1.96 (3)
1.91 (12)
1. 82 (10)
1.88(14)
1.81 (U)
1.85 (6)
1.81 (1)

2.03 (5)
1.95 (9)

1. 97 (16)

2. 00 (.■!8)
1. 99 (33)

2.04 (17)

2.01 (8)

2.02 (4)

1.83 (2)
1.81 (9)
1.70 (19)
1. 76 (23)
1. 70 (42)
1. 75 (43)
1. 73 (24)
1.81 (8)

1.93 (2)
1.85(11)
1.86(21)
1.87(30)
1.88(29)
1.81 (18)
1.85(19)
1.85 (7)
1.76 (1)

151 to ITiO mm

161 to 170 mm _..

i.Vs "(i)

1.70 (4)
1.72(13)
1.73 (34)
1. 78 (52)
1.78 (48)
1. 83 (36)
1. 87 (18!
1.93 (10)
1.78 (2)

2.02 (1)

1.87(11)
1.83(14)

181 to 190 mm...

191 to 200 mm

1.86 (21)

1.88 (25)

211 to 220 mm

1. 93 (23)

221 to 230 mm

1.93(15)

231 to 240 mm

2.01 (5)

251 to 260 mm

258

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

viduals of an age group did not differ in condition
from tlie shorter, slower-growing fish of the same
group.

The conclusion concerning the independence of
growth rate and condition disagrees with Van
Oosten's (1937) observation that the slower-grow-
ing individuals of the Lake Superior longjaw
{Leucichthys zenithicus) were in the better condi-
tion. The same author (Van Oosten 1938)
found, however, that growth rate and condition
were not correlated in the Lake Erie sheepshead
(Aplodinotus (jrunniens) .
Effect of type of gear on determining value of K

The study of condition in the preceding sections
was confined entirely to data from collections
taken by trap and pound nets. Gill-net samples
were excluded because of the effect of the selective
action of that gear on the determination of K.
The extent to which gill-net selection affects the
determination of the value of the coefficient of
condition may be seen from the data of table 35
which show the average K for each centimeter-
length interval of the Lake Erie yellow perch
taken from trap and gill nets in the same month
and calendar year. Only five series were available
for comparisons. The consistency with which the
value of K was greater for fish caught in gill nets
than in trap nets each month leaves little doubt
that gill nets capture relatively heavier yellow
perch than do impounding nets. In no single
month did yellow perch taken in trap nets have

average coefficients of condition as great as thosp
of fish taken in gill nets.

The unweighted averages given in the two
columns at the extreme right of table 35 give
further information on the general influence of the
type of net on the value of K. These averages
were computed only for those lengths that were
represented in the samples in all the months for
which comparisons are given. An examination
reveals that fish taken in gill nets had consistently
higher average values of K. The averages also
reveal a difference between gill- and trap-net
samples with respect to the variation of K with
length. Except for the relatively high figures at
141 to 150 mm. and 161 to 170 mm., the values of
K tended to be constant at all lengths in the trap-
net samples. The cause of the high values of K in
these shorter fish taken in impounding nets has
been discussed previously (p. 256). The nearly
constant value of K over the interval 171 to 220
mm. is proljably descriptive of true condition in
the population. In the gill-net samples, on the
contraiy, K decreased consistently with each
increase in length over the entire interval of 171 to
240 mm. In other words, the gill nets selected
the heavier short fish and the slenderer long fish.
At lengths below 171 mm. the captures of perch
by gill nets were probably in large measure
"accidents," that is, the fish were tangled in the
meshes by their fins or the marginal bones of the
mouth. The selective action of gill nets with

Table 35. — Effect of type of gear on determination of the coefficient of condition (K) in Lake Erie yellow perch

[Number of specimens in parentheses]

Standarrt-'.ength
interval

Average
total
length

September 1927

October 1927

July 1928

August 1928

November 1928

Average i K

Trap nets

Gill nets

Trap nets

Gill nets

Trap nets

Gill nets

Trap nets

Gill nets

Trap nets

GUI nets

Trap
nets

Gill

nets

91 to 100 mm

Inches
4.5
5.0
5.4
6.9
0.3
6.7
7.2
7.6
8.1
8.6
9.0
9.4
9.9

in. 3

10.7
11.2
11.6
12.1
12.5

2. 23 (1)

101 to 110 mm ..

2. 78 (1)
2. 86 (3)
2. 53 (2)
2. 72 (1)
2.11 (12)
2. 10 (65)
2.04 (123)
2.01 (146;
2. 03 (99)

2. 00 (42)
1.97 (9)

2. 01 (3)
2. 11 (2)
1.68 (1)

Ill to 120 mm

2.13 (1)

121 to 1.30 mm

i. 96 (3)

1. 90 (5)
1. 86 (9)
1.97 (7)
1.80 (1)
2. 64 (1)
2. 16 (6)

2. 05 (39)

2.06 (168)
2.00 (261)
1.99 (99)

1. 91 (20)
1. 85 (6)

1. 67 (4)
1.70 (16)
1.87 (.38)

1.95 (67)

1.93 (98)

1.91 (115)
1.90 (132)
1.90 (I6:i)
l.Hl (1401

1.94 (71)
1.94 (49)

1.92 (4)
1.9fl (5)

1. 96 (2)

2.31 (i)
1.90 (1)

1. 95 (2)
1.98 (1)
2. 00 (3)
2. 02 (2)
2. 16 (2)
2.02 (11)
2.08 (29)
1.97 (51)

1.96 (32)
1. 83 (5)
1. 90 (4)

131 to 140 mm ..

1.90 (2)
1.76 (1)
1.80 (1)
1.76 (7)
1.89 (19)
1.82 f23)
1.93 (22)
1.8« (21)
1.88 (13)
1.87 (12)
1.92 (3)
1. 73 (1)

2. 70 (1)
2.30 (8)
2. 14 (13)
2.16 (24)
2.11 (32)
2.18 (61)
2. 17 (74)
2.06 (79)
2.02 (49)
1.91 (24)
1. 86 (9)
1.68 (3)
1.94 (1)

1.90 (1)
1. 97 (1)
1.79 (1)
2.12 (1)

1.94 (5)
2.10 (11)
2.09 (.12)
2 05 (116)

1.95 (101)

1.91 (69)
1.88 (10)

141 to 150 mm

161 to 160 mm ,,

2. 36 (5)
2.22 (18)
2. 14 (25)
1. 98 (33)
2. 06 (32)
1.90 (10)
1. 60 (4)
1. 94 (2)

2.08 (2)
2. 04 (3)
2.19 (20)
2.19 (70)
2.18 (209)
2. 14 (499)
2 08 (468)
2 01 (212)
1. 96 (43)
1.91 (11)
1. 78 (4)

1.97 (2)

2.01

2.03

161 to 170 mm

171 to 180 mm...-
181 to 190 mm. --
191 to 200 mm..--
201 to 210 mm- ..
211 to 220 mm.---
221 to 230 mm

2.12 (2)
2.00 (17)
1. 99 (35)
1.98 (43)
1.96 (27)
1.96 (16)
1.89 (2)
2. 25 (1)

2.00
1.96
1.93
1.94
1.94
1.95

2.05
2.18
2.16
2.09
2.06
1.99
1.96

231 to 240 mm.-. -

1.88

241 to 250 mm- ..

251 to 260 mm

2.06 (1)

261 to 270 mm- .-

271 to 280 mm....

1.99 (1)
1.99 (145)

Average ^

1.87 (126)

2.01 (626)

1.91 (894)

2.06 (129)

2.10 (369)

2.04 (510)

2.10(1,642)

1.98 (144)

2.00 (368)

1.96

2.04

' Unweighted mean, computed only for length intervals that were represented in all samples.
' Unweighted mean.

TELLOW PERCH OF LAKE ERIE

259

respect to condition would not be expected lo
operate on these accidental captures. The selec-
tion by gill nets of yellow perch according to the
condition of the fish is similar to the action of drift
(gill) nets on marine herring (Farran 1936) and
supports the i)revious conclusion of a like action
among the smaller perch by impounding nets.

From the preceding discussion it appears not
only that gill nets tenfl to take relatively heavier
yellow perch in Lake Erie than trap nets but that
in gill-net samples K decreased with increases in
length. The resulting distortion of the data
justifies the exclusion of gill-net material from the
study of condition.

SIZE AT MATURITY

A knowledge of size at sexual maturity has its
practical application in the determination of the
minimum legal size that may be needed to protect
an adequate spawning stock. Data on the rela-
tion between total length and the percentage of
maturity of the yellow perch taken in 1927-37 are
given for the sexes separately and combined in
table 36. The males matured at a much smaller
size than the females: 47.4 percent of the males
were mature or maturing at 6 to 6.5 inches and
48.4 percent of the females were mature or matur-
ing at 8 to 8.5 inches. Any minimum legal size for
the Lake Erie yellow perch, therefore, must be
based on the maturity of females.

The shortest K-inch total-length interval that
contained a large percentage of mature females
was 8 to 8.5 inches. At that length 48.4 percent
were mature. At lengths of 8.5 to 9 inches 86.1
percent were mature, and at 9 to 9.5 inches 97 per-
cent were mature. All females 9.5 inches and
longer were mature. These data show that 86.1
percent of the females were mature in the shortest
}2-inch total-length interval (8.5 to 9) available to
the commercial fishery operating under the 8}2-inch
minimum legal size now effective in the Michigan
and Ohio waters of Lake Erie (no size limit on
yellow perch in Pennsylvania and New York

waters). The samples collected in 1947-48 showed
an even greater proportion of mature female yellow
perch since 51 of 53 individuals (96.2 percent) in
the 8.5- to- 9-inch interval were mature.

On the basis of the data in table 36 it is ap-
parejit that the great majority of female j'ellow
perch in Lake Ya'ip mature at total lengths
between 8 and 9 inches. Reference to table 19
reveals that most of the fish with these lengths
belonged to age group II (174 mm. standard
length is equivalent to 8 inches total length, and
196 mm. equals 9 inches). It thereby becomes
apparent that the majority of the female yellow
perch reach maturity in Lake Erie during their
third year of life and spawn for the first time early
in theii- fourth year (as age-group-III fish). The
average calcidated length of the females at the
end of the third year of life was 8.6 inches
(table 7).

Although the data in tables 36 and 19 are from
fish taken late in the fall one would expect little,
if any, growth in winter or until spawTiing time
in the spring. The percentages of maturity at
the different sizes determined from fall samples,
therefore, may be applied reasonably well to the
spawning-season population. The small sample

Table 36. — Relation between length of Lake Erie yellow perch and proportion of mature individuals, 1927-37

Fork-length interval '

Standard-length
interval

Sexes combined

Female

Male

Total-length interval '

Mumber
mature

Number
imma-
ture

Percent-
age
mature

Number
mature

Number
imma-
ture

Percent-
age
mature

Number
mat ure

Number
imma-
ture

Percent-
age
mature

Less than 6.n inches . .

Less than 5.7 inches...

5.7 tofi..1 inches

«..■? to 6.7 inches

Less than 127 mm

127 to 140 mm

10

26

82

216

521

901

737

426

236

38

17
50
154
189
137
64
15

37.0
34.2
34.7
53.3
79.2
93.4
98.0
100.0
100. U

1

30
103
348
423
290
190

15

31
95
131
110
56
13

12.5

fi.9
18.0
48.4
86.1
97.0
100.
100.0

9

26

75

18S

418

553

314

136

46

23

10

19

59

58

27

8

2

47.4

141 to 149 mm

57.8

7.0 to l.h inches

1.50 to 161 mm

.56.0

7.2 to 7.7 inche-s

7.7 to 8.2 inches

8.2 to 8.7 inches

8.7 to 9.2 inches

9.2 to 9.7 inches.

9.7 inches and over

162 to 172 mm

76.2

8.0 to 8.5 inches

n.? to 183 mm.

1.S4 to 195 mm

93.0
98.6

9.0 to 9..1 inchos

9.5 t(i in.tJ inches

10.0 inches and over. .

19B to 206 mm

207 to 218 mm

219 ram. and over

99.4
100.0
100.0

> Fish included within each total-length and fork-length interval had lengths equal to the lowest and up to. but not including, Che greatest length of the

interval.

260

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

obtained during the breeding season suggests that
spawning in itself may protect immature females
since only 3 of 27 females (11.1 percent) in the

entire sample were immature. The largest of the
immature females in this sample was 8}^ inches
total leng;th.

SEX RATIO

The number of specimens, the sex ratio ex-
pressed as the percentage of males in the total for
the daily collections, and the ratios for the com-
bined collections of each month are shown in table
37 for samples containing 50 or more fish. All
samples were obtained from commercial impound-
ing nets. The sex ratio of the individual samples
fluctuated rather widely within each month except
August, September, and December, 1929, and
April 1932. This wide fluctuation points to a
segregation of the sexes throughout much of the
year. A segregation may occur, however, in a
month in which the sex ratio is not highly variable
(as the predominance of males in April 1 932) .

The wide daily variation in the relative abun-
dance of females and males in the samples makes
it <lifficult to determine a truly reliable sex ratio
for the perch of Lake Erie. The data in table 37
suggest that a large number of relatively small
samples, preferably distributed thi'oughout the
season, will permit a more accurate estimate of the
relative abundance of the sexes than may be
obtained from a few large samples. Table 37
reveals that the average ratio for all samples com-
bined, except those taken in April, was 96 females
to 100 males (50.9 percent). The April samples
were omitted from the computation because the
sex ratio obviously was distorted by the presence
of disproportionately large numbers of males.

The April (1928 and 1932) collections were con-
sistent in the strong preponderance of males.
The males predominated also in both samples ob-
tained late in May 1929. On the other hand, the
females were relatively more abundant in the
samples obtained May 9 and 10, 1929. One
sample collected during June 1929 indicated that
the sexes were segregated, whereas the other
showed no marked preponderance of either sex.
The data obtained during July 1929 showed an
increasing proportion of males as the month ad-
vanced. The males were somewhat more abun-
dant than the females in each sample taken during
August, but on no date, with the possible excep-
tion of August 6, were they strongly predominant.
No strong dominance of either sex was evident in

the material taken in September. The single
October collection contained nearly 70 percent
males. Only two of seven samples taken during
November (November 26, 1929, and November 7,
1937) showed sufficiently disproportionate repre-
sentation of the sexes to be interpreted as indic-
ative of segregation. There was little evidence
of segregation on the two dates in December. In
general, then, it appears that the sexes were segre-
gated during April and May, and probably to
some extent during part of June, July, August,
October, and November. There is no evidence of
any distinct segregation during September and
December; however, only two samples were taken
in each of these months.

Table 37. — Percentage of males in the daily samples of
Lake Erie yelloiv perch

Date

Num-
ber of
speci-
mens

Percent-
age of
males

Date

Num-
ber of

speci-
mens

Percent-
age of
males

1928: Apr. 30 . -

1929:

May 9

May 10

May l.-i

May 25

94

110
147
228
132

95.7

30.9
26.5
74.6
69.7

1929:

Nov. 2 -

Nov. 12

Nov. 16

Nov. 22....
Nov. 26

Novem-
ber, all
samples.

Dec. 4

Dec. 7

Decem-
ber, all
samples.

1932:

Apr. 11

Apr. 13

April, all
samples-

1937:

Nov. 3 -

Nov. 7 -

N v c m
ber, all
samples-

Orand
total,
April
ex-
cluded

72
251
114
51
86

.'.1. 4
47.0
57.9
54.9
72.1

574

May, all
samples -

617

54.3

M.7

June 20

June 29

563
90

37.1
54.4

136
171

.55.1
.57. .T

June, all
samples.

653

39.5

307

56.4

Julyl

Julys

July 13

July 20

July 30

202

65
447
114

68

30.7
36.9
48.1
60.5
64.7

70
63

75.7
84.1

133

July, all
samples

896

46.2

79.7

65
66

Aug. 6

Aug. 17

Aug. 22

Aug. 26

Aug. 31

252
87
86
178
133

61.1
56.3
52.3
56.6
52.6

47.7
68.2

131

68.0

August,
all sam-
ples

736

56.7

4,313

Sept.3 -

Sept. 23

216
114

47.2
65.3

50.9

Septem-
ber, aU
samples.

330

50.0

Oct. 26

69

69.6

YELLOW PERCH OF L.\KE ERIE

261

The reasons for the apparent segregation of the
sexes of the Lake Eric yellow perch are largely un-
known. The segregation during April and May
perhaps was due to the spawning-season habits of
the species. A segregation associated with se.x
differences in feeding habits during the summer
months, such as was found by Eschmeycr (1938),
may occur. Materials for study of the food of
the Lake Erie perch were not available. Another
possible factor in the fluctuating sex ratios during
the summer is age. The females tend to increase
in relative abundance with advancing age; con-
sequently, variation in the age composition of the
samples would contribute to an apparent segrega-
tion of the sexes. However, this explanation can
account for only part of the variation in the sex
ratio since the ratios varied \\idely in samples of
fish of the same age but taken on different days of
the same month (table 38).

Age determinations of certain of the above
materials permit the examination of the relation
between the proportional representation of the
sexes and age. Table 38 shows the sex ratio of
Lake Erie yellow perch in a number of samples,
expressed as the percentage of males in the total,
by age group. Because of the daily fluctuations

Table 38. — Percentage of male Lake Erie yellow perch by
age grorips, according to date of capture

[Total numbor of sppcimpns In parontheses]

Date

Age group

I

II

III

IV

v

1939:

July!

38.5(13)
33.3(9)

26. 7(131)

57. 7(104)

12. 5(16)

0(1)

-Sept. 23

0(1)

Nov. 12

83.3(18)
80. 0(5)
80.0(5)

49.4(83)
55. 8(52)
74.3(35)

43. 8(121)
.57. 4(54)
67. 4(43)

33.3(27)
66. 7 (.3)
100. 0(3)

0(2)

Nov. 16

Nov. 26

all

November,

82. 1(28)

56.5(170)

51.8(218)

42. 4(33)

0(2)

Deo 4

83. 3(6)
69.4(36)

52 7(55)
51.8(83)

.56.1(66)
59. 2(49)

44.4(9)
66. 7(3)

Dec. 7 -- -

all

Doccmber,

71. 4(42)

52. 2(138)

56. 5(115)

50. 0(12)

1932:

Apr. 11

100. 0(2)

83.3(48)
88.0(50)

55. 0(20)
69. 2(13)

\pr 13

ples-

.\prll. allsam

100. 0(2)

85. 7(98)

60. 6(33)

1937:

Nov. 3

71.4(28)
73. 5(34)

31. 4(35)
61. 3(31)

0(2)
100.0(1)

Nov. 7

all

November,

samples

72. 6(62)

45. 5(66)

33.3(3)

tal,
ex-

.

Grand tc
April
eluded-.

73.7(133)

52.0(396)

48.0(571)

36.1(61)

0(3)

in sex ratio the data have been presented for dailj'
catches as well as bj' the month and for all months
combined. In spite of certain exceptions, it may
be said that there was a progressive decrease in
the proportion of males as the age increased. It
is apparent that either the relative abundance of
males in the stock was progressivelj^ less with each
yearly increase in age, or that the females were
progressively more available to the fishery.

Sex differences in the age of entry into the
fishery can produce an "apparent" change in the
sex ratio with increase m age. The earlier attain-
ment of maturity by the males, together with their
apparent tendency to remain on the spawning
grounds longer than the females, doubtless ac-
counted for the great preponderance of males in
age groups I and II and their abundance in age
gi-oup III of the spawning-run (April 1932) collec-
tion. Consequently, the decrease in relative
abundance of males \ni\\ increase in age in that
collection caiuiot be accepted as descriptive of the
general population. Significance must be as
cribed, however, to the fact that a similar, if less
pronounced, change in the sex ratio occm-red in the
collections of other months when there is no
reason to believe that a segregation on the basis
of maturity existed. In a majority of the samples
taken in months other than April the males ex-
hibited a tendency to decrease in relative abun-
dance with increase in age. It may be concluded
that this tendency of the males is a real and not
an apparent characteristic of the Lake Erie
yellow perch.

The acceptance of a shifting sex ratio with age
as characteristic of the Lake Erie yellow perch
population carried with it the assumption of a
differential mortality of the sexes. This differ-
ence in death rate may have its origin in a selective
destruction in the fishery or it may depend on sex
differences in the natural mortality rate.

It would appear that a differential destruction
of the sexes by the fishery is the most plausible
explanation of the changes in sex ratio Avith age
of the Lake Erie yellow perch. The males
mature at a j-ounger age, and consequently, are
taken by the nets during the spawning season
earlier in life than are the females. Furthermore,
the apparent tendcncj' for the males to arrive
earlier and stay longer than the females on the
spawning grounds increases the chances of capture
for any particular male, and presumably would

262

FISHERY BITLLETIX OF THE FISH AND WILDLIFE SERVICE

result in effect in a more intensive fishery for that
sex. The monthly records of the Ohio Division
of Conservation for the years 1930, 1931, 1939,
and 1940 '* reveal that during those years the
spawTiing-season fishery (April and May) produced
28.3 percent of the perch caught diu'ing the entire
year in Ohio waters. Fishing intensity during the
spawning season, when the males predominate in
the catches, is therefore sufficiently great to ac-
count for an important differential destruction of
the sexes. The apparent preponderance of fe-
males during early May would reduce, but prob-
ably not eliminate, the effect of the spawning-
season fishery on the changes in the sex ratio. It
seems impossible to escape the conclusion that the
changes in sex ratio with age of the Lake Erie
yellow perch were caused in large measure by a
differential destruction by the fishery chiefly diu--
ing the spawning season.

It should be mentioned that the minimum legal
size operates to reduce the effect of the differential
destruction of the males in the spawning-run
fishery. Large numbers of mature but illegal-
sized males on the grounds are captured but

returned to the lake. However, it is known that
about 14 percent of the illegal-sized yellow perch
are destroyed, or seriously injured, when the nets
are lifted. It is not improbable that the total
destruction of illegal-sized males during a spawn-
ing season is considerable, in spite of the fact that
none enters the commercial catch.

Other factors that might have had aii influence
on the changes in sex ratio with age will be men-
tioned briefly. Geiser (1923, 1924a, 1924b) con-
cluded that the females (of fishes, as of many other
animals) are inlierently more viable than the
males under adverse conditions. Hile (1936)
stated that a differential natural mortality was
the most probable cause of the changes in sex ratio
of the Cisco, Leucichthys artedi, with age. There
is no fishery for the cisco in the Wisconsin lakes
whose populations he studied. Hile pointed out
further that there was no basis for any assumption
of a differential destruction of the sexes by preda-
tory forms. Any possible effect of a differential
natural mortality of the sexes would be obscured
in the Lake Erie yellow perch because of the
differential destruction by the fishery.

SUMMARY

1. The annual production of yellow perch from
the United States waters of Lake Erie fluctuated
about an average of 3 million pounds in the early
(1885-99) period of the fishery. The average
declined to about 2 million pounds in 1900-1927,
increased to over 7 K million pounds in 1928-35, and
fell to about 2% milhon pounds in 1936-47. There
was a definite tendency for the variability in
annual production to increase in each succeeding
period except the most recent one (1936-47).
The trend in average annual production from the
Ontario waters was similar to that in United States
waters only in the last two periods, 1928-35 and
1926-47. The factors of fishing intensity (in-
creases in the number of nets, and improvements
in nets, boats, and methods of lifting gear) , changes
in fishery laws and the administration of the laws,
and abundance were considered in evaluating both
tlie long- and short-period trends in the annual
production of Lake Erie yellow perch.

2. In this study, age determinations and growth
calculations were made from examination and
measurement of the scales of 4,377 yellow perch

" These four years are the only ones close to the period during which sex
data were obtained for which monthly records of catch are available.

taken by trap nets from Lake Erie. In addition,
ages were determined of 576 specimens employed
in a special study of the relation between body
length and scale length, and of 1,566 fish taken by
gill nets. Analysis of the length-weight relation
was based on 23,158 specimens, and the length
frequencies were compiled from the measurements
of 59,779 individuals. The materials were col-
lected during the years 1927 to 1930, and in 1932,
1934, 1937, and 1943 to 1948. Data from the
diflerent sections of th(> lake were combined after
preliminary examinations revealed the combina-
tion justifiable.

3. Validity of the use of annuli on the scales of I
the yellow perch as year marks was established
for the first time on the basis of the following
observations: (a) The 1927, 1928, and 1929 col-
lections were dominated by the same year class
that was represented by larger and, according to
scale readings, older fish in each succeeding year;
(b) the annulus was on the margin of the scale in
the early season but was progressively farther
from the margin in raid-July, September, and
December; (c) the lengths calculated from scale
measurements for different years of life agreed

YELLOW PERCH OF LAKE ERIE

263

rather closely with the empirical lengths of fish
shown by scale readings to have completed the
same number of years of life, and lengths calcu-
lated for the same year of life agreed more closely
with each other than with lengths computed for
any other year regardless of the age of the fish
employed in the calculations.

4. The more important criteria employed to
determine the presence of an annulus were the
discontinuity between successive growth fields
which resulted in well-defined "cutting over" of
the cu-culi, particularl}' in the lateral region of the
scale, and the fragmented, u-regular appearance
of the last circulus laid down in each growing sea-
son. False annuli occui-rod but it is believed they
usually could be detected by the lack of cutting
over, their generally indefinite appearance, and
tlieir position with respect to true annuli. About
5 percent of the scales were discarded as unfit for
age determinations.

5. Annulus formation maj^ be completed as
late as July 1 in some years. In spite of the ap-
parent coincidence of spawning and the completion
of the annulus in some years, the annulus cannot
be considered as a spawning mark since immatm-e
individuals form annuli identical in appearance
with those formed by mature fish, and the charac-
teristics of a typical spawning mark as found on
the scales of other fish are absent from yellow
perch scales.

6. Detailed data are provided on the relation
between body length and scale length of the
American yellow perch.

7. The Dahl-Lea method of calculating lengths
by direct proportion was applicable to the yellow
perch when the calculated standard lengths were
96 mm. (4.5 inches total length) or greater. When
these lengths were less than 4.5 inches they were
corrected by use of a table containing the corrected
length corresponding to each length computed
by direct proportion. These corrected calculated
lengths, derived from an empirical curve of the
body-scale relation, were always gi-eater than the
uncorrected lengths. Correction of the com-
puted lengths failed, however, to e'iminate the
discrepancies between corresponding lengths cal-
culated for different age groups.

8. Discrepancies occurred between correspond-
ing calculated lengths in all years of life. The
computed lengths for any one year of life decreased
progressively as the fish for which the computa-

tions were made became older. Discrepancies in
first-year calculated lengths were small among
age groups older than group I.

9. The discrepancies in calculated lengths were
shown to represent real rather than "apparent"
differences in growth since large erroi"s could not
result from the method of calculation.

10. It was concluded that the selective action of
gear, selection according to maturity at the time
of the spawning run, and selection according to
legal-size limit, all of which doubtless produced a
selective destruction of the more rapidlj' growing
individuals in the fishery, were the chief causes
of the discrepancies in the calculated growth of
the Lake Erie yellow perch, but that a differential
natural mortality, correlated with rate of growth,
was a possible supplementary factor. The presence
of discrepancies between corresponding calculated
lengths of different age groups of the same year
class proved that annual fluctuations in growth
rate were not an important source of the dis-
crepancies in calculated lengths.

11. The females grew in length a little more
rapidly than the males during the first j-ear of
life, at the same rate in the second year, and
more rapidly in all later j^ears.

12. The aimual increments of growth in length
decreased progressively with age in both sexes.

13. Growth compensation occurred in the Lake
Erie yellow perch, but usually did not appear
before the third year of life. The difl'erence in
average length between the largest and smallest
yearlings was maintained or increased in the
second year.

14. It was estimated that the proportions of
growth completed at the end of the different
months of the 1928 and 1929 seasons were 15 per-
cent for June, 50 percent for July, 80 percent for
August, and 100 percent for September. How-
ever, growth continued through October in 1927.

15. Significant correlations could not be demon-
strated between armual fluctuations in growth
rate and precipitation, percentage of possible sun-
shine, and mean wind velocity. Significant posi-
tive correlations were determined, however, be-
tween growth and mean air temperatures for the
following combinations of mouths: May, July,
and September; May and September; July and
September. Mean air temperatures in August
exhibited sisrnificaiit negative correlation with
annual fluctuations in growtli rate.

264

FISHERY BULLETIN OF THE FISH AND WILDLIFE SEEVICE

16. The yellow perch of Lake Erie grew more
rapidly than did most of the perch of other waters
with which comparisons were made.

17. Scales of Lake Erie yellow perch used by
Harkness (1922) were compared with those in the
present study, and the annual increments of
calculated length indicated no pronounced change
in the growth rate of 1927 from that of 1920.

18. Length frequencies of the impounding-net
collections had a unimodal distribution each year,
but gill-net collections showed both unimodal and
bimodal distributions.

19. The position of the mode in the length fre-
quencies fluctuated from year to year, and was
influenced to a considerable extent by the average
length of the dominant age group. The modal
frequency fluctuated over a wider range in the im-
pounding-net collections than in the gilled fish
from gill nets because of the greater selectivity
of the latter gear.

20. The coefficient of condition K of individual
Lake Erie yellow perch ranged from 1.13 to 3.23,
and averaged 1.91. The state of the gonads
affected the coefficient of condition of the females
during the spawning season, at which time they
lost approximately 16 percent of their prespawning
weight. There are no data on the loss of weight of
males at spawning. At other periods condition
was not related to sex or state of maturity.

2 1 . The coefficient of condition increased sharply
from June to July and remained at a high level in
August and September. In two of three years
condition declined in the autumn, but m the third
year it improved.

22. Weight of the Lake Erie yellow perch in-
creased at a rate slightly greater than the cube of
the length. Over the interval of length to which

the equation was fitted the empirical and calcu-
lated weights agreed closely.

23. The year class of 1926 was unusually strong
and dominated the impounding-net catches of
1927, 1928, and 1929. There is evidence from the
samples of legal- sized yellow perch that the 1942
year class also was one of exceptional strength.
The year classes of 1936 and 1944 are believed to
have been of more than ordinary size.

24. No relation between strength of year classes
and meteorologic conditions could be demon-
strated.

25. The commercial catch (legal size) of both
impounding and gill nets was dominated by age
group III in the spring and early summer. Domi-
nance by group-II fish was characteristic of the
late-season catches of both types of gear, although
there are exceptions when age group III may be
dommant in both gears dui-ing the autumn.

26. The sex ratio was determined to be 96
females to 100 males in the combined data from
all samples except those obtained in AprU, when
the ratio was obviously distorted. Evidence was
obtained of segregation according to sex in all
months from AprU to November, inclusive, except
September. It was pointed out that the number
of samples employed, as well as the number of
individuals examined, was important in the
accm'ate determination of the sex ratio. The
relative abundance of females in a year class
increased with age.

27. Male yellow perch in Lake Erie matured at
an earlier age and at a smaller size than females.
Practically all males were mature or maturing at
a total length of 8 inches. Proportions of females
matm'e or maturing at different total lengths were
48.4 percent at 8 to Scinches, 86.1 percent at S>%
to 9 inches, and 97 percent at 9 to 9/2 inches.

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1942. Some meteorological and limnological conditions
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1939. Growth of Minnesota fishes. Minnesota Con-
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1937. Some characteristics of a population of stunted
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1943. Annual landings of fish on the Canadian side of
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Gallagher, Hubert R., and John Van Oosten.

1943. Supplemental report of the United States mem-
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1923. Evidences of a deferential death rate of the sexes
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Greeley, J. R.

1935. A biological survey of the Mohawk-Hudson
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1936. A biological survey of the Delaware and Susque-
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1939. A biological survey of the fresh waters of Long
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1940. A biological survey of the Lake Ontario watershed.
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Harkness, W. J. K.

1922. The rate of growth of the yellow perch (Perca
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Hile, Ralph.

1931. The rate of growth of fishes of Indiana. Investi-
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1936. Age and growth of the cisco, Leudchthys arledi
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1941. Age and growth of the rock bass, Amblopliles
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Hile, Ralph, and Frank W. Jobes.

1941. Age, growth, and production of the yellow perch,
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1942. Age and growth of the yellow perch, Perca fla-
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Hjort, Johan.

1914. Fluctuations in the great fisheries of northern
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1921. The literature of fish scales. Salmon and Trout
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266

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

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1933. Preliminary report on the age and growth of the
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o

UNITED STATES DEPARTMENT OF THE INTERIOR, Oscar L. Chapman, Secretary
FISH AND WILDLIFE SERVICE, Albert M. Day, Director

FLOUNDERS OF THE GENUS PARALICHTHYS

AND RELATED GENERA IN

AMERICAN WATERS

By Isaac Ginsburg

FISHERY BULLETIN 71

From Fishery Bulletin of the Fish and Wildlife Service

VOLUME 52

UNn ED STATES GOVERNMENT PRINTING OFFICE • WASHINGTON: 19 5 2

For sale by the Superintendent of Documents, U. S. Government Printing Office, \\'ashington 25, D. C.

Price 60 cents

CONTENTS

Pag<!

Common names 269

Sampling 269

Structural differences distinguishing the species 269

Scales 270

Gill rakers 272

Anal rays 273

Dorsal rays 274

Correlation in the numbers of anal raj's and gill rakers 274

Frequency polygons 276

Color pattern 277

Proport ional measurements 280

Cliange of form with size 281

Sijecimens at the border line 282

Generic limits 284

Key to the American species 285

Hippoglossina 287

Sul)genus Hippoglossina 288

H . boUmani 288

H. mystacium 289

H. stomata 289

H. macrops 291

Subgenus Lioglossina 293

H. oblonga^__ 293

H. tetrophtliahnus- 297

Pseiulorhombus 298

P. isosceles 299

Paralichthys 300

Subgenus Paralichthys 301

P. microps 30 1

P. patagonicus 30 1

P. hilgendorfii 304

P. schmitti 305

P. fernandezianus 305

P. adspersus 306

P. californicus 307

P. aestuarius 310

Subgenus Chaenopsetta 312

P. woolmani 312

P. brasiliensis 314

P. dentatus 316

P. albigutta 324

P. vorax 327

P. tropicus 327

P. lethostigma 328

P. squamilentus 332

Species of doubtful relationship , 334

Paralichthys triocellatus„ _ 334

Paralichthys cocruleostiota - — 335

Hippoglossus kingii ^ 335

FLOUNDERS OF THE GENUS PARALICHTHYS AND RELATED GENERA

IN AMERICAN WATERS

By Isaac Ginsburg, Fishery Research Biologist

Tliis report is nn account of tlie iinjioi'taiit trroiip
of fliittishes bel(mfiiii<;; to the ^eiuis Paralivhthys,
and the closely related genera Hippoglossina and
I'se)/dorhoinhuj<. which occur in Aniei'ican watei-s
and, in the agfjregate, are food fishes of great eco-
nomic importance. Three of the leading species,
tlie summer flounder, the southern flounder, and
tlie California halibut, add annually nearly 20
million pounds to the commercial catch of the
United States. Statistics are not available for
some other species which are of lesser economic
importance or occur on the coasts of Central and
South America. The combined catch of all the
lesser species is probably considerable at present
and will very likely increase with future advances
in exploitation of the natural resources of the
American continents. In view of the importance
of these species, it is remarkable how little we
ivuow of their biology. Such knowledge is a pre-
i-equisite to the wise exploitation of any species.
This report presents some basic knowledge of the
species, derived from first-hand, accurately deter-
mined data, which is necessary to their further
study.

In order to understand properly the species of
Paralk-hthy,^. it is necessary to consider also those
that belong to Ilippoglo>iSina and P-'iendo/ho-mhiis,
as the species of these three genera form an inter-
related, closely knit, and compact group. A seri-
ous drawback to a I'ational study of their life his-
tories is the difficulty of properly distinguishing
the species, which are so closely related that where
two or more occur together considerable difficulty
lias been encountered in tiying to refer specimens
to their respective species. It is true that Jordan
and Gilbert (Bull. U. S. Nat. Mus., 16: 8i;-2-823,
1883) long ago indicated in broad outline the
structural characters by which the connnon species
may be distinguished; but in Parulichthys that
did not prove sufficient. Descriptions based on a
few specimens may be of use in separating matei'ial
in btdk, but they are insufficient to identify a

consi(leral)le percentage of individual fish. The
chief characters distinguishing the species are of a
meri.stic nature. The extent of intraspecific vai'ia-
tions in these characters is considerable. More-
over, the species are closely related and they ap-
proach one another or even intergrade somewhat
in these characters. Consequently, when speci-
mens at or near the border line with respect to one
or more structural characters are examined, they
a))])ear to be inseparable specifically, and doubt is
thus cast on the distinctness of the species.

The difficulties encountei-ed in properly distin-
guishing the species concerned may be appre-
ciated by a consideration of two treatises dealing
with those species. Hildebrand and Cable (Bull.
U. S. Bureau of Fisheries 46:464, 1930) state:
"■. . . the present writers are unable to separate
the representatives of this genus [Parali^tithy^^,
occui-ring locally [at Beaufort, N. C], into more
than two groups (species?) . . ." The fact is
that three common species are present at Beaufort.
The data given by these authors on the chief dilfer-
entiating characters nearly agree with those de-
termined by me. Many of their specimens formed
the basis of my studies. Their figures 79-81 rep-
resenting the frequency distributions of the num-
bers of gill rakeis and anal and dorsal rays evi-
dently are bimodal polygons which, taken sepa-
rately, would nn(lerstan(lal)ly lead to the state-
ment quoted above. However, it is of the utmost
importance to correlate the data on wliirh the
p<iiygons are based. To illustrate, their iigurc 7'.)
consists of two well-defined polyg<jns wiiich
tomii at a point, and seemingly it re])resents not
moi'e than two s])eties. Howevei', were the fre-
(|uency distributions of the number of anal rays
of the specimens represented in the left polygon
gra]ihed separiitely. the result would be a polygon
similar to their figure 80. That is, the left poly-
gon represents two s|)ecies, albigutta and letlw-
stigiiHi. while the right jiolygon repivsents
dciitatwi. Similarly we may use their ligure 80

267

268

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

as the starting point of the correlation. It con-
sists of two somewhat irregular polygons which,
considered independently, might also be taken to
represent two species. Were the number of gill
rakers of the specimens represented by the right
polygon graphed separately, the result would be a
bimodal polygon similar to their figure 79, which
would represent two species, lethostigma and
denfafus; while the left polygon of figure 80 rep-
resents aJhIgutta. A comparison of Hiklebrand
and Cable's figures 79-81 with figures 1-3 of this
report will clarify the preceding discussion. The
intraspecific variability and distribution of the
three characters concerned, among the three com-
mon species, are such that when a mixture of speci-
mens of the three species is studied and the mixed
data graphed for each character separately, as
was done by Hiklebrand and C;ible. the resulting
polygons would be similar to their figures 79-81,
leading to the conclusion that not more than two
species are involved. But when the characters are
correlated it becomes clear that three distinct and
common species are represented. Moreover, after
correlating the characters and dividing the mass
of specimens into three rather well-defined species,
other characters appear which although not suffi-
ciently divergent to separate all the specimens will
yet distinguish the great bulk of specimens of the
three species, respectively.

Norman ^ states : '■'•{alblgutta is] perhaps identi-

cal with P. lethostigma .

(p. 75

and

". . . it is possible that lethostigma, alhigutta and
squamilentus will eventually have to be regarded
as representing one variable species" (p. 76).
However, when adequate sanqiles of the tliree
species about which Norman was in doubt are
studied and the data correlated and tabulated, as
is done in tlie following pages, all questions as
to their distinctness disappear. While Norman
tentatively did treat these three species as dis-
tinct, he did not properly separate all his western
Atlantic specimens.-

In order to prove that the separate species are
distinct, and to show how individual fish may be

^A systoinntic nionop:raph of the Fl.itfishes (Heterosoinata)
vol. 1, Psi'ltuilidac, Botliiilao. Plueronectidae, by J. R. Norman,
British Muscmn, London. ]li:;4.

' .See Gin.sl>Hrg, .Tour. Washington Acad. Sci., vol. 26. pp.
130-133. 1936. In that paper I discuss briefly some of the
differences between the present treatment of the species and
that in Norman's work. Where necessary the discussions are
here amplified under the accounts of some of the species.

identified, it becomes necessary to investigate the
chief distinguishing characters by statistical
methods ; in other words, it is necessary to deter-
mine in detail the variability of these characters
of each species separately, showing precisely their
limits and their normal frequency distributions,
and to correlate them. That has been accom-
plished during the present study for the com-
mon species, as far as available material permits.
It now becomes a comparatively easy matter to
separate the species. There is seldom trouble in
placing individual specimens, certainly not more
so than in many other closely related species.

A study such as that reported in the following
pages manifestly must precede any consistent
study of the life history of each species. Besides
studying their taxonomy, the known and scat-
tered data regarding the biology and the econom-
ics of the species have been digested and con-
densed, and original observations included. This
pa]ier treats of those species that inhabit the At-
lantic and Pacific coasts of North and South Am-
erica. The species are so closely interrelated that
it is necessary to treat them as a group in order
to understand them fully.

In stating proportional measurements of cer-
tain parts throughout this paper, the figures given
refer to percentage of the standard length. State-
ments of the size of specimens refer to the total
length, including the caudal fin. Measurements
of the eyeball and orbit are those of the ujiper
eye. The stated number of scales refers to the
number of rows over the straight part of the lat-
eral line unless otherwise specified (p. 271). The
diagnoses include only those characters which are
of importance in distinguishing the species.
Counts and relative proj)ortions are mostly given
in general statements in the diagnoses. More
detailed data are in the tables which form part of
and should be used in connection with the diag-
noses.

In the following accounts of the species, the
given numbers of specimens e.xamiiied are (hose
in the United States National Museiun Catalog,
unless otherwise indicated.

All illustrations accompanying this paper, ex-
ecuted with such obvious skill, were prepared by
Louella E. Cable. Figures of specimens represent
reworked photographs, which were made in the
Smithsonian photographic laboratory.

FLOUNDERS OF GENUS PARALICHTHYS AND RELATED GENERA

269

COMMON NAMES

Since these flounders ;ire common or abunilant
fooil fi^shes, it is esjjecialiy desirable for each
species to have a distinctive common name which
may be uniformly applied to the same species
throughout its ranire. An attempt is here made
to introduce such conmion names for the species of
Paralichthys that occur in the waters of the United
States. It is well known to those who deal with
the fishes of the country as a whole that the mul-
titude of common names applied to a given species
is confusing, especially with food fishes that enter
the cliannels of trade. Xot only are species often
known by different names in different sections of
the country, but frecjuently this occurs in adjacent
communities of the same State. It is even more
confusing when a name is applied in one locality
to a particular species, and in another to an en-
tirely different species. In this paper, therefore, a
distinctive English name is suggested as a uniform
counuon name for the species.

SAMPLING

The chief cliaracters used for separating the
species are of a meristic nature and vary within
rather wide limits. The variations are of the usual
frequency-distribution type and lend themselves
readily to the ordinary methods of statistical
studies of such variations. It is evident, there-
fore, that in any study of these characters it is
important to sample the individuals examined in
such a manner that the resulting frequency dis-
tribution, as tabulated, represents as nearly as pos-
sible the living population of the species in the
water.

The importance of a representative sample in
studies of fin ray counts for instance, is forcibly
impressed after gaining considerable experience in
such studies. It may be readily observed in species
in which the number of fin rays varies within
considerable limits that sj^ecimens obtained in
the same haul of the net will sometimes tend to
grou]) themselves either near the beginning or
near the end of the frequency distribution of the
species as a whole. Therefore, in oi-der to portray
adequately the meristic characters for each species,
the method of selecting the sample to be studied
is of importance. If, let us say. the fin rays of
one hundred specimens are enumerated and tab-
ulated, and all the specimens are obtained in a

single iiaul of the net, the lesult is apt not to pre-
sent a true picture of the species. On the other
hand, if the hundred specimens are taken at ran-
dom, one each, from as many hauls in different
localities, the result is apt to present a fairly good
view of the normal variation of that ciiaiacter
witliin the species as a whole. The individuals
employed in this study represent specimens ob-
tained by methods intermediate between these two
extremes. They were those obtained in the ordi-
nary course of extensive collecting, when the tend-
ency on the part of the collectoi- is to save a few
specimens out of each haul as a sample, especially
when any haul yields too many individuals of one
species. All the individuals tabulated herewith
are a composite of many such samples generally
ranging from 1 to 10 specimens m each sample.
Only three samjiles had more tlian 10 specimens,
the highest number being 21. Tlie frequency dis-
tributions thus obtained for the more common
species probably represent fairly those of the re-
spective species, at lea.st near enough for practical
purposes. (The question is further discus-sed on
p. 276 in relation to tlie tliree common east -coast
species.)

STRUCTURAL DIFFERENCES DISTIN-
GUISHING THE SPECIES

For the practical purpose of the proper distinc-
tion of the three common eastern species, it is onlv
necessary to enumerate correctly for any given
specimen, the gill rakers, the anal rays, the dorsal
rays, and the scales. The importance of the
character's is in the order stated. These struc-
tural characters in combination with evident dif-
ferences in the color pattern will serve to distin-
guish individual fish of the three common si)ecies
of the east coast. Proportional measurements in
the east coast species are generally' of secondary
importance. However, when all the species are
taken into consideration these generalizations do
not hold altogether, and the important differenti-
ating characters are pointed out under each spe-
cies. Also, when all the species of the genus are
considered, the structure of the scales, whether
cycloid or ctenoid, and the presence or absence
of accessory scales is of much importance in classi-
fication.

In distinguishing the species in general, leliance
nuist lie ])laced to a lai'ge extent on the nunil)ei- of

270

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

gill rakers, fin rays, and scales. As these numbers
vary within wide limits within the species, and
individual fish of closely related species may ap-
proach or even overlap in these respects, it is
evident that the course of the student in his at-
tempt to properly distinguish the species is beset
with many pitfalls. By way of illustration, it may
be pointed out that a specimen of lethostigma, for
instance, having 65 rays in the anal fin may be con-
sidered as conspecific with a specimen of alh'tgutta
having 62 rays, rather than with another specimen
of h-thoxtiyma having 72 rays, as far as this one

character is concerned. Of coui-se, in the proper
identification of any given specimen all the char-
acters must be taken into account, but the student
will be greatly aided in reaching the correct con-
clusion, if instead of the simple range of each
meristic character, he has before him tables show-
ing the frequency distributions of these charac-
tei-s. Such tables are therefore supplied here, as
far as availal)le material permitted. In addition
to their practical value, the tables afford valuable
evidence going to prove the distinctness of closely
related species, where doubt may exist.

Table 1. — Fiequencii fHntribiitimi hi/ number of ohliqiie rovs of scales over straight part of lateral line to end of hypiiral.

Number of scales

Spocios

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

Hippodossina

1

1

2

2

1

1

1

2

1

1

3

1

2

—

1

1
2

1

2

2

2

1

1

4

3

1

2

1

1

2

1

2

1

Pseudorhombus

2

1

Paralichthys

1

1

5
5

1
1

7

2

2
2
1
8

1
4
2
1
3
16

1
4
4
1
2
11

7
6
3

3

5

1
3
1
2
2
8

1
6
2
2

2
2

..-
1

'I'

2
4
3

1
5

1
1
1

1
2

1
1
2

1

1
1

1

1

—

1

2

■"

...

2

1
8

U

"

1
3

X
8

2
6

—

1

2
2

2

1

3

2

1

albigutta.

2

1
1

6

5

7

18

16

10

9

—

—

—

---

1
5
1

1

1

1

3

12

11

15

17

20

8

7

11

8

5

5

—

1
1

i"

2

—

1

2

1

2

-■

1

SCALES

The cycloid or ctenoid character of the scales is
of primary importance in the major division of the
species comprising the genus Paralichthys and is
of much help in the identification of the species
of this genus as well as of related genera. In the
Fishes of North and Middle America, by Jortlan
and Evermann (Bull. U. S. Nat. Mus., No. 47, Pt. 3,
1898), a general work used by ichthyologists to
identify American fishes, this character is inade-
quately treated. In the definition of the genus
(ibid. p. 2624) the statement is made "scales small,
weakly ctenoid or ciliated." This is not true of
all the species ; and in the descriptions of some of
the species the scales are correctly described as
"smooth" or "cycloid." It is interesting to note
that in the same work, the two genera which are
closely related to Paralichthys^ namely, Hip-
poglossina (p. 2020) and Lioglossina (p. 2()2'2),
as limited by those authors, are distinguished by

the scales, ctenoid in one and cycloid in the other.
This character is also of importance in forming
major divisions of the species comprising the
genus Paralichthys. The presence or absence of
s])iiiules on the scales was found to be the most con-
stant of all characters used in the distinction of
the species, with the exception of P. assfuarius and
Hippoglossina oblonga (the latter species being
assigned to Paralichthys by Jordan and Evermann
in the work cited). In H. oblonga the number of
spinuliferous scales is highly variable, but a few
are always present on the caudal peduncle of the
blind side in specimens over 75 mm. long, and the
eyed side of the head always has spinuliferous
scales in large specimens. In P. aestiuirius, it is
an age character, the scales of the eyed side being
all si)inuliferous in fish less than about 160 mm. in
length. The spinules are gradually lost after
that length has been reached; the scales become
cycloid in specimens over 220 mm. In the other

FLOI'XDERS OF GENUS PARALICHTHYS AND RELATED GENERA

271

sppries. tliis diaractcr is constant at all apes, al-
ilioiiirli in veiy large fisli the spinules in the species
liavinir tliem sometimes are com])aratively less
niaikeil. In ver}- large specimens they sometimes
change to coarsely granular asperities, but the
<listingnishing nature of the scales is still evident.
The two exceptional species in this respect, and
I lie change of the scales in very large specimens of
otiier sj)ecies perliajis explains the inadequate
treatment this character has received in the study
of the species of Paralichfhys. However, the
structure of the scales is of as nnich importance in
interpreting the relationship of the species and in
the practice of identification, as it is in related
genera. Besides the presence or absence of
spinules on the scales, another important cliaracter
which may be used in generic division is the pres-
ence or absence of accessory scales (see p. •284).

Besides the structure of the scales, their size,
which is usually expressed inversely as the num-
ber along certain lines of the body, is a valualile aid
in distinguishing the species when used in con-
nection with the other characters, although it
usually shows much variability and considerable
intergradation. One serious drawback to a pre-
cise use of this chai-acter is the difficulty of de-
termining the number of scales with any reason-
able degree of accuracy. The ttibes in the lateral
line are easiest to count in young fish, but the more
or less clear-cut boundaries between the individual
tubes disappear to a large extent with growth.
Also, with increase in size the normal scales on
either side gradually overlap more and more those
in the lateral line, while the increasing numbers
of accessory scales cover the surface of all the
large scales more and more. Consequently, in
large or medium-sized fish, it is almost imj)ossible
to count the individual scales in the lateral line
with any reasonable degree of accuracy.

After testing diflPerent methods of expressing the
scale count, the following procedure was adojited
as yielding fairly accurate results with the least
amoiuit of labor. The count is made of the num-
ber of oblique rows over the straight part of the
lateral line, beginning with the row standing di-
rectly over that canal in the lateral line which is
entirely, or almost entirely, horizontal and end-
ing with the i-ow the lowest scale of which is at the
end of the hypural as determined by flexing the

caudal fin. In counting the scales the specimen is
held with the back tilted down and away from
the observer. When held in this position the re-
flection of light is such that the rows of scales
ap]iear fairly prominent, and the rows are counted
rather than the individual scales. Sometimes the
fish has to be turned somewhat at different angles
until the rows become prominently visible so that
they may be coimted with any fair degree of ac-
cuiacy. X check on a number of small specimens
shows that the number of scales in the lateral line
closely approximates the number of oblique rows
placed over it.

The number of rows along the curved part of
the lateral line cannot be determined with as much
accuracy as along the straight part, because the
rows in the anterior part of the body are more
irregular, and because of the greater difficulty of
fixing the point to begin the count. Had these
rows been included in the count, the small increase
in the degi-ee of specific divergence would have
been made at the sacrifice of greater accuracy.
They were, therefore, omitted and the number of
scales stated in the diagnoses in this paper and in
table 1 uniformly refers to the numl)er of oblique
rows over the straight part of the lateral line

In current descriptions, the number of scales is
usually stilted as so many or ''about'' so many in
the lateral line. It seems desirable to have some
conversion factor by which current descriptions
may be correlated with the present paper, al-
though it seems highly probable that counts hither-
to recorded by different investigators are not com-
parable by a wide margin, because of the use of dif-
ferent methods. The number of scales in the
curve was determined on a muuber of small speci-
mens in which they may be counted with a fair de-
gree of accuracy. It was found that, in general,
that number closely appioxinuites one-half of the
number in the straight part. Therefore, by add-
ing one-half to the number given in this paper,
counts of scales are obtained which are approxi-
mately comparable with those gi\en in current de-
scriptions. In the short accounts of established
species of which no si)eciniens were examined the
number of scales stated is that obtained by using
the above conversion factor and subtracting the
estimated numbers in the arch from the number in
the entire lateral line.

272

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

GILL RAKERS

Next to the structure of tlie scales the iiuinber
of gill rakers constitutes the most vahiable char-
acter for separating tlie American species. It has
been universally so used and its importance justly
emphasized. For the three common species of the
east coast, figure 1 shows unquestionably that
dentatus is distinct from the other two. Fre-
quency distributions of all the species studied are
shown in tables 2 to 4. The number of gill rakers
as recorded may vary somewhat with the observer.
For instance, in driitatus the upjiermost gill raker
on the upper limb is sometimes very small. Less

Table 2. — Fmiiirtuij dixlrihiilinii liij vKnihrr of r/il! nikm
on till' iiijjjer limb of tlic first gilt arch

Species

Number of gill rakers on upper limb

1

2

3

4

5

6

7

8

9

10

11

Hippoglossina

3

3

1
8

stomata

6

1

3

23
4

1

tetrophthalmus

Pseudor horn bus

3

Paraliehthys

1

1

adspersus

12
14
11

5
53
21

30

4

1

aestuarius

1
1

9
8
5

1
1

12

8

64

1

2

63

dt^iitatus . _

41

6

31

1
138

lethdstigma

8

7

6

2

frequently, this is also true of the anteriormost
gill raker of the lower limb. In this investigation
the smallest gill rakers were included if they were
large enough to be manipulated with a dissecting
needle. In alhigutta and lethostigina. slight dis-
crepancies in the counts made by different investi-
gatoi's would be due chiefly to the variability in
the uppermost gill raker of the upper limb. This
gill raker is sometimes vei-y small, later becoming
closely adherent to the gill arch as a triangular
piece of cartilage, and finally, seeming to merge
with the gill arch. Frequently, when grown to the

Taulk ."?. — Frcqiiency distribution bij nnmbrr of ijill rnkers
on the lower limb of the first gill arch

Species

Number o( sill rakers on lower limb

7

8

9

10
3

11

12

13

14

15

16

17

IS

19

20

21

22

23

Hippoelos'iina
bollmani

3

1

stomata

1

6

4

4

oblonga

1

11

13

1
2

2
3

tetrophthal-
mus

Pseudorhombus

1

Paraliehthys
patagonicus-

1

1

adspersus

1

2

4

7
5
6

3
10
11

36
9

29
10

17

5

aestuarius.,
woolmani i

-

—

2

ii'

'i'

4
3

2

8
18

—

1

3
44

2
35

4

11

—

—

albigutta

9

39

41

4

1

tropicus

1
6

5

-

7

67

66
5

squamilen-
tus

5

1 The short stumps of gill rakers, 3 to 5 in number, on upper limb, not in-
cluded in the count. Traces of 1 or more gill rakers in other species also not
included (see text).

' The type specimen has 11 gill rakers on lower limb on eyed side and 13 on
blind side, the latter number bt'ing included in the table, all the counts
having; been made on the blind side.

Table 4. — Friq

iienry distribii

tion by

number of gill ra

kers on the outer

gill

arch

Species

Total number of gill rakers on outer arch

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

2S

26

27

28

29

30

31

32

Hippoglossina
bollmani

2

2

2

1
2

stomata

1

....

6

3

2

1

3

10

12

1

1
3

1

tetrophthalmus

Pseudorhombus
isosceles

1

2

Paraliehthys
patagonicus

ad.spersus

1

2

2

7
2

1

4
6
4

1
10
12

califnrnicus

26
14

27
3

13

1

12
1

6

1

7

6
5
2

6
3
2

2

4

12

brasiliensis >

4
35

1
23

2

2

29

albieutta

4

23

29

32

s

1

tropicus - . .

1
10

1

6

63 66

squamilentus. ..

6

6

3

FLOUNDERS OF GENUS PARALICHTHYS ANB RELATED GENERA

273

7. 40

30
20
10

1
1

1

V- —

\

'

—

le

thoA

m j

\
\

\

I

N^^

1

1

\

\ dtbi^utid

/

^N^

k

1
1

i

\ '

Mentalu9 \

1
/

1

\

\

/

\

/

1

!

\

\

\

/

\

/

I

1

\

1

\

\

\

/

\

\

■\

)

a

12 13 14

NUMBER OF (ilLL KAKKKS

15

16

17

18

FiGiRE 1. — Frequpney distrilmtinn by miiubor of ;;ill rakers on lower liuili of outer frill arch of three common east -coast
species of I'aralichthi/s. Number of specimens: 115 cleiitdtiis, IK! Utlwstiymu, 93 tilhiijiittii.

gill arch its triangular outline may be readily
traced, but often it is very faint. In this study the
uppermost gill raker was arbitrarily included when
it projected sufficiently above the surface of the
gill arch so that it could be manipulated with a
dissecting needle. When it was adherent to the
arch even though its outline was evident it was not
included in the count. It may also be stated that
such specimens are comparatively few, and any
slight differences in counts which may be made
by different observers would have little effect on
the final result when large numbers are studied.
In this study all the counts were made by me. The
counts of gill rakers as here recorded were all made
on the blind side because of greater convenience in

counting. The two sides sometimes varA' slightly
in mniiber; but in the small number of specimens
in which counts were made on both sides, as a
test, there was no average difference in comparing
both sides. The counts were then all made on the
blind side for convenience and to insure uni-
formity.

ANAL RAYS

Xext to the gill rakers the number of anal rays
constitutes the most important character for sep-
arating the three common east coast species, the
intergrading individuals being few. This char-
acter is especially valuable in separating alh'xjutta
fniiu lioth (fciifiitKx and Itthostiymu. A glance at

Tahle ."

). —

-Fri'iiinncii

lli.-

in

6h

timi li

/ limit

hr

" of riiiis

1)1

Ihi

II mil

Jin

Species

Number of anal rays

46

47

48

49

SO

SI

52

53

54

55

5t>

57

58

59

60

61

62

63

64

65

66 67

68

69

70

71

72

73

74

7si76;77

1 1

Hippoglossina

bollmani >

1

1

1

2

1

mystacium

1
1

stomata .

1

---

1

2

7

2

1
1

...

1

2

1

6
I

1
1

4

4

1

2

2

...

...

1

FsfUdorhoinbus

1
1

1

1

Panilichthys

i

•

1

adspersus

1
23

i7'

3

16

5
4
3
5
£

6
2
2
5
3

2
2

4

1

2

1

1

4

6

14

26

aestuarius _

3

3

1

8

8

4

8

3

1

1

4
2

1
2

brasiliensis .. ..

2

1
11

1
S

i

5

4

13

2S

21

12

18

6

6

5

albiEutta _.

1

1

4

10

16

16

26

17

1

...

...

...

"2
1

i
2

io"

is"

2S"

27"

si"

13

ii'

■»■

i'

1

...

1

3

3

6

980335°

-52 2

274

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

22

20

a

I 18

•J.

K

< a

P4

i

\

- —

/

\

V

/

\

\

/

ah

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eni

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55 5f S5 S6 51 58 59 60 61

6Z 63 6i 65 66 67 68

NUMBER OF ANAL KAYS

^ 70 71 1Z 75 n 7S 76 77

FiGTTBE 2. — Fre(iuency distribution by number of anal rays of tliree foninion east-coast species of I'driiliclillnis. Xumlier

of sijecimeus : 117 dtntutus, 153 lethustiyma. 111 allnyutta.

figure 2 sho^YS the essential specific divergence of
ulbigutta from those two closely related species.

Because the fin ray counts overlap more or less,
while at the same time being of prime importance
in separating the species, it is essential to make an
accurate count when using this character. In this '
study every fin was counted twice, once on either
side, as a check. Since the fin rays are many and
the labor of counting tedious, great care and
jjatience must be exercised to insure an accurate
count. In practice, some means may suggest them-
selves to check the counts on both sides of part
of the fin. For instance, most specimens have
places where the interradial membrane is con-
spicuously broken. The number of rays up to such
a point is jotted down and when the count is made
on the other side this number is checked. Again
the count may be made in groups of five or ten
rays, a dissecting needle being used to point off
the groups. By adopting some such means of
facilitating the count accuracy is possible.

DORSAL RAYS

Although in the three common eastern species
the number of dorsal rays intergrades to a con-
siderable extent (fig. 3), it is a useful character,
supplementing the two previous ones for distin-
guishing doubtful specimens. In the separation
of cariforruc'us from aestuarhtfi, the numbei' of
dorsal rays intergi-ades somewhat less than the
number of anal rays. The methods of counting
and recording the munber of dorsal rays were the
same as stated for the anal rays.

CORRELATION IN THE NUMBERS OF ANAL RAYS
AND GILL RAKERS

Figures 1 to '?> show that the inimber of gill
rakers and that of the anal rays constitute the two
most divergent characters. By plotting these two
counts, one against the other, in a correlation table
(fig. 4), a striking proof of the essential specific
divergence of the three common eastern species is
obtained. Figure 4 has been prepared from the

FLOUNDERS OF GF.^•US PARALICHTHYS AND RELATED GENERA
Taulki;. — Fri<iii( iirji ilixfriljiilioii hit iiiiiiiIk r of lailx in llii dursiil fin

275

Species

Number of dorsal

rays

60

61

62

63

64 65

66

67 68

69 70

71

72

73

74

75

76

77

78

79

80|81

82

83 ' 84 ' 85 ' 86

87

8889

90

91 I 92

9.

91

95

96

Hippoglossina

bollmani

1

2

2

I

1 1

. ' 1

1
3

slomata

I

1

3

3

3

...

1 1

...

1

2 2 2

5 5 S

i"

2

1

1
1

1

1

1

2

tftropht halmus

1

Pst-udorhombus

isosceles .

-.-

Parulichthys

I

1

1
13

3
18

2
IS

1
18

3

3

7

5
6

1
2
1
2
1

1
1
3
2
3

californicus

i

7

"i"

4

6
2

1

3

1

5

4

1

6

S

2

2

woolmani

2
1

i 2

3
2

5
2

1

—

I

dentatus

1
9

1

n

1
6

4

3
3

9

1

8

13

21

21

IS

5

5 4 :;

1

albiputta

1

2

4

6 12 10

14

13

15

vorax

1
1

tropicus

1 1

' \'

1 4
S .f 9

2

1

6
1

15

11

20 18

1

22

14

11

5 13 2

1

squaiiiilciitus

/8

IC

14

'A

y. /z

~ '0

§ (>

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Figure

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1

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7
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1

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1

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71 7Z 15 If 7S 76 77 78 79 80 81 8Z 83 8f 85 86 87 88 89 90 91 9Z 95 94 9S 96,

NTMIIKR (IF DOKSAL KAVS

3. — Frequency ilislrilmtion liy iiunilier of dorsal rays of iliree eoiuinnii east-coast species of I'ltnilirhtliiis. Nuiii-
lier of siiecinieiis: 11(1 dciitiilKx, 140 li IlKi.slii/iiid, ll)".> iilhiiiiiltii.

roiiorh (lata Ii(>fofe attciiipting to segregate the
specimens into tlieir respective species. .V mere
inspection of figure -4 siiows convincingly how
the specimens are massed into thice fairl}- well
(lefineil gi-oiips. These tliree gionps represent:
(1) alhhjiitta showing a correlation of low gill
raker and fin ray counts; {•!) lethoKtignui having
a combination of rehitively few gill rakers and
many fin rays; (3) thutntiiH being cliaracterized
by relatively many gill rakers in correlation with
many fin rays.

Wliile tlie hulk of the specimens are concen-
lral('(l at tiiree well sepaiiUed legions, smalU'r
numbers of specimens radiate diffusely from ilie
I hree centers of concentration and it is not possible
to draw sharp lines of demarcation sejiarating the
three species by these characters akine. The
proper placement of specimens at or near tlie
border line is discussed on page •2S'2. After sucli
somewhat doubtful specimens are properly placed
the boundaries may be drawn between the species
witli assui'ance, and tliev are indicated \\\ a broken

276

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

line in the chart. In only one of the squares does
the broken line cross. That is, of tlie total number
studied only two specimens of alblgittta and one
of lethostigma have the same correlation of the
number of gill rakers and anal rays. Such speci-
mens must be assi<j:ned to their proper species by
means of other characters.

In figure 4 is plotted the total number of gill
rakers. Practically the same result is obtained by
plotting the number on the lower limb only, except
that in that case the lines are more densely
grouped.

FREQUENCY POLYGONS

Three variable cliaracter.s wliich are of impor-
tance in distinguishing the three common species
from the east coast of the United States are rep-
resented graphically in figures 1 to 3. The poly-
gons representing the number of dorsal rays are
markedly irregular; those representing the gill
rakers are fairly regular; those representing the

anal rays are intermediate with respect to regu-
larity of arrangement. The irregularities are ap-
paiently caused by imperfect sampling and may
result from one or all of the following main fac-
tors. (1) The number of specimens studied may
not be sufficient to form a representative sample
in its resjiective species. (2) The method of sam-
pling may be inadequate. (3) The samples do
not represent altogether homogeneous popula-
tions. It will be shown hereafter (p. 320) that
the populations of dentatus from Chesapeake Bay
and from North Carolina differ appreciably in
these three characters. To some extent this is
also true of diiferent populations of lethostigma
(p. 332), and probably also of alhigvtta, although
in the latter two species population differences are
appai'ently not so marked. The irregularities in
dentatus partly disappear when the data are
tabulated separately for Chesapeake Bay and
Nortli Carolina.

10

t

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M

1

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1

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III

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Mil

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1

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de.

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g 18

1

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II

II

III

1

I

1

1

2/

III

tHJ

lUJ

nil

nil

r

1

Ill

1

2Z

1

f

1

r

rNj

III

III

1

1

23

1

ffV

?i^

nil

tHJ

1

1

II

z-i

II

II

1

1

II

Si- 55 56 57 5a 59 60 61 6Z 6i 6f 65 66 67 68 69 70 71 ^^. 73 7'f^ 75 76 77

NUMBER OF AXAL RAYS

Figure 4. — Corrplation between total number of Rill rakers on first gill arch and number of anal rays, of three common
east-coast species of PnmWehthija. (See p. 274). Each mark represents one specimen; four marks with a cross
line represent five specimens.

FLOUNDERS OF GENUS PARALICHTHYS AND RELATED GENERA

277

On tlic otlier liaiul. llic inarkfd rci;uhnit.v slinwii
liy tlic distribution of the gill-niker count of
li thostlgiiM is apiJaiiMitly due to the fact that it
is based on material tiiat is not entirely homoge-
neous. A combination of the somewhat heteroge-
neous data happened to result in a markedly regu-
lar distiibution in this case. The more detailed
analysis of tlie data for this count is given on
page ;^;^2, which shows that the distribution for the
combined populations of Texas and Louisiana is
not quite so regular as that shown in figure 1.
The same may also be true of alhUjntta.

The geographic origin of the specimens form-
ing the basis of the graiihs is as follows. The
total number of specimens tabulated are dlhigufta^
111; dentatuH, 120; and hthortlgma, 159. The
three charactere were determined for nearly all
these specimens; in a few exceptions one or an-
other character was indetermiiuible on account
of injury. The localities of capture of these speci-
mens are: alhigntfa, 71 in a mixed lot from Beau-
fort, N. C. and Kej' AVest, Fla. (see footnote on
p. 279). 20 from Texas. 13 from Florida, and 1
from South Carolina; dentatus, 71 from Chesa-
]>eake Bay, 45 from Beaufort, N. C, 2 from South
Carolina, and 2 from Georgia; lethosfigma, 100
from Louisiana, 34 from Texas, 15 from Beau-
fort, N. C, 4 from Georgia, and 2 each from Flor-
ida, South Carolina, and North Carolina. The
great btdk of the specimens in every case thus
came from two localities.

Figures 1, 2, and 3 show that we are dealing
here with three entirely distinct species, although
the samides studied apparently are not altogether
re])resentative. and somewhat insufficient as to
number. The distributions based on the speci-
mens examined are somewhat irregular and each
species differs to some extent with the locality;
but the data presented prove conclusively that
each species has its own characteristic distribu-
tion iind fairly well-defined limits. It is evident
that a fairly good idea of the speiitic distributions
and their limits may be gained from the deter-
mined (lata; but a study of more specimens and
sani])les more nearly approaching perfection
should serve in smoothing the distributions. It
is of particular interest to determine further the

(iillVrences witii local stocks in the distributions
of the variabU' characters.

COLOR PATTERN

A cursory examination (jf tiie species of Para-
liclifhyx, in general, shows them to be irregularly
blotched. After handling these fishes for some
time, however, one ma}' sec a definite generalized
color pattern; differences in this pattern, on closer
examination, are of some a id in ilistinguishing the
species.

The generalized color pattern of the genus may
best be discerned in some young fi.sh, especially in
those in which the pigment is of medium intensity,
neither too dark nor too light. The fundamental,
typical color pattern may be said to consist of five
longitudinal rows of spots on a variably shaded
background, one row along the midline, one under
the base of the dorsal, one over the base of the anal
and two intermediate rows, one between the
median and up]>er rows and the other between the
median and lower rows. (The spots are sometimes
rather irregularly arranged and appear to be in
7 irregular rows, see pp. 306, 307, and 312.) The
rows may be designated for convenience in discus-
sion as subdorsal, upper intermediate, median,
lower intermediate and supra-anal. The spots in
the subdorsal and supra-anal rows are generally
smaller than in the other three rows. The
spots in the median row are generally diffuse,
except one spot situated about three-quarters of
the way from the gill opening to the base of the
caudal fin. In many species this is the most con-
spicuous spot on the body and in the following
discussions it will be designated as the ])re])e-
duncular spot.

The value of the color ])altern in distinguishing
species lies chiefly in the fact that certain