415 ,

Pacific Tuna Biology Conference

SPECIAL SCIENTIFIC REPORT— FISHERIES No. 415

UNITED STATES DEPAJWVIEJ^T^^

TTslTAN^wnHirTsERvicr

United States Department of the Interior, Stewart Udall, Secretary
Fish and Wildlife Service, Clarence F. Pautzke, Commissioner
Bureau of Commercial Fisheries, Donald L. McKernan, Director

PACIFIC TUNA BIOLOGY CONFERENCE

AUGUST 14-19,1961

HONOLULU,HAWAII

Edited by

John C . Marr

U. S. Bureau of Commercial Fisheries

Biological Laboratory

Honolulu, Hawaii

United States Fish and Wildlife Service
Special Scientific Report: Fisheries No. 415

Washington, D. C.
May 1962

ABSTRACT

A report of the work and results of the Pacific Tuna Biology Conference, held at the University
of Hawaii in August 1961 under the auspices of the Bureau of Commercial Fisheries Biological Labo-
ratory, Honolulu, and attended by tuna research workers and fishery experts from 11 countries. The
report comprises a general account of the proceedings of the Conference; summaries of the discussions
in six general sessions on distribution, migrations, subpopulations , behavior, tuna oceanography, and
taxonomy and nomenclature; the reports of two special working groups, on identification of larval and
juvenile tunas and on taxonomy and nomenclature; resolutions adopted by the Conference; abstracts of
the 50 papers presented; and a list of the participants.

TABLE OF CONTENTS

Page

Introduction 1

Program 2

Summary report of discussions 2

Resolutions 18

Abstracts of papers 20

Alverson, Dayton L. - Ocean temperatures and their relationship to albacore tuna
(Thunnus germo) distribution in waters off the coast of the States of Oregon and
Washington and the Province of British Columbia 20

Austin, Thomas S., and Richard A. Barkley - Use of oceanographic monitoring stations

in fishery research 20

Bell, Robert R. - The age composition of the California Pacific albacore catch 21

Blackburn, Maurice - Distribution and abundance of Eastern Tropical Pacific tunas in

relation to ocean properties and features 21

Brown, RobertP., and Kenneth Sherman - Oceanographic observations and skipjackdis -

tribution in the North Central Pacific 22

Clemens, Harold B. -The distribution of California bluefin tuna in the eastern North

Pacific 22

Clemens, Harold B. - The distribution of albacore in the North Pacific 22

Clemens, Harold B. - Migration, age and growth, and spawning studies of the North

Pacific albacore (Thunnus germo) 23

Collette, Bruce B. - A preliminary review of the tunas of the genus Thunnus 24

Fujii, Yutaka, Koichi Mimoto, and Shichiro Higasa - Biochemical studies on the races

of tuna. Base composition of testis deoxyribonucleic acid (DNA) 24

Hiyama, Yoshio, and Kenji Kurogane - Morphometrical comparisons of tuna from areas

in the Pacific and Indian Oceans 24

Inoue, Motoo - Relation of sea condition and ecology of albacore in the northwest Pacific

Ocean 25

Iversen, Robert T. B. - Food of albacore tuna, Thunnus germo (Lacepede), in the cen-
tral and northeastern Pacific 26

Johnson, James H. - Sea temperatures and the availability of albacore (Thunnus germo)

off the coasts of Oregon and Washington 26

Kamimura, Tadao, and Misao Honma - Distribution of yellowfin in the longline fishing
ground in the Pacific Ocean, especially on the regional variation of the density in
each size group 27

Kikawa, Shoji -Studies on the spawning activity of the Pacific tunas Parathunnus mebachi

and Neothunnus macropterus by the gonad index examination 27

iii

TABLE OF CONTENTS (con.)

Page

King, Joseph E. , and Robert T. B. Iversen - Midwater trawling for forage organisms

in the central Pacific 28

Legand, M. - Donnees Biometriques sur les thons a nageoires jaunes en Nouvelle-

Caledonie

28

Legand, M. - Quelques donnees biometriques sur les albacores de la region ouest de

la Nouvelle-Caledonie 29

Legand, M. - Longueur, repartition des sexes et maturation sexuelle des thons a

nageoires jaunes de Nouvelle-Caledonie 29

Legand, M. , and R. Desrosieres - Enqueue preliminaire sur les contenus stomacaux

des thons a nageoires jaunes des cStes de Nouvelle-Caledonie 29

Legand, M. and B. Wauthy - Importance presumee d' Alepisaurus sp. dans le cycle

biologique des thons de longue-ligne au large de la Nouvelle-Caledonie 29

Legand, M. - Contenus stomacaux des albacores et yellowfins captures a la longue-
ligne par l'Orsom III 30

Legand, M. - Taille, repartition sexuelle, cycle annuel de l'albacore dans l'ouest de la

Nouvelle-Caledonie 30

Marr, John C, and Lucian M. Sprague -The use of blood group characteristics in

studying subpopulations of fishes 31

Matsumoto, Walter M. - Identification of larvae of four species of tuna from the Indo-
Pacific region. I

31

Mimura, Koya - Studies on Indo-maguro 31

Nakamura, Eugene L. - The establishment and behavior of skipjack tuna ( Katsuwonus

pelamis) in captivity

Nakamura, Hiroshi - An outline of the tuna longline grounds in the Pacific 32

Otsu, Tamio, and Richard J. Hansen - Sexual maturity and spawning of albacore in the

central South Pacific Ocean 32

Otsu, Tamio, and Richard N. Uchida - A model of the migration of albacore in the North

Pacific Ocean 33

Ridgway, George J. - Distinction of tuna species by immunochemical methods 33

Roedel, Phil M. , and John E. Fitch - Taxonomy and nomenclature of the Pacific tunas. . . 33

Rosa, H. , Jr. , and T. Laevastu - World distribution of tunas and tuna fisheries in re-

lation to environment.

34

Royce, William F. - A morphometric study of yellowfin tuna, Thunnus albacares

(Bonnaterre) 35

Seckel, Gunter R., and Thomas S. Austin - The association between Hawaiian skip-
jack landings and the oceanographic climate 35

iv

TABLE OF CONTENTS (con.)

Page

Sprague, LucianM. , and Leslie I. Nakashima - A comparative study of the erythrocyte

antigens of certain tuna species 36

Sprague, Lucian M. , and Leslie I. Nakashima - Studies on the erythrocyte antigens of

the skipjack tuna (Katsuwonus pelamis) 36

Sprague, Lucian M. - Blood group studies of albacore (Germo alalunga) tuna from the

Pacific Ocean 37

Strasburg, Donald W . - An aerating device for salt well water 37

Suda, Akira - Comparison of abundance between albacore and bigeye in the northwest

Pacific 37

Suzuki, Akimi - Blood types in tuna 38

Uchida, Richard N. , and TamioOtsu - Analysis of sizes of albacore occurring in vari-
ous Pacific fisheries - A preliminary report 38

Uda, Michitaka - Cyclical fluctuation of the Pacific tuna fisheries in response to cold

and warm water intrusions 39

Uda, Michitaka - Localized concentration of tunas in the eddies along oceanic fronts. ... 39

Watson, Margaret E. , and Frank J. Mather III - Species identification of juvenile tunas
(Genus Thunnus) from the Straits of Messina, northwestern Atlantic, and the Gulf
of Mexico 40

Yabe, Hiroshi, and Shoji Ueyanagi - Contributions to the study of the early life history

of the tunas 40

Yabuta, Yoichi, and Mori Yukinawa - Age and growth of yellowfin tuna 41

Yamanaka, Hajime, and NoboruAnraku - Relation between the distribution of tunas and

water masses of the North and South Pacific Oceans west of 160° W 41

Yuen, Heeny S. H. - Experiments on the feeding behavior of skipjack at sea 42

List of participants 43

PACIFIC TUNA BIOLOGY CONFERENCE

AUGUST 14-19, 1961

HONOLULU, HAWAII

Edited by

John C . Marr

U. S. Bureau of Commercial Fisheries

Biological Laboratory

Honolulu, Hawaii

INTRODUCTION

An informal Pacific Tuna Biology Confer-
ence, arranged by the U. S. Bureau of Commer-
cial Fisheries Biological Laboratory at Honolulu,
was held at the University of Hawaii, August 14-
19, 1961. Fifty papers were contributed to
the Conference; 79 persons attended from
11 countries.

The informal nature of the Conference
was stressed for at least three reasons: First,
so that it would be evident that this was in no
sense a government-to-government meeting but
rather a gathering of scientists with common
interests. Thus, any decisions taken would in
no way be binding upon governments but rather
would represent working arrangements between
individuals or between laboratories. Second, it
was hoped that the informal nature of the pro-
ceedings would encourage discussion and con-
tribute to the free exchange of ideas. This was
either not a real problem or the arrangements
achieved their intent, since discussions were
spontaneous from the start. Third, the infor-
mality allowed me, as organizing chairman, and
as a matter of convenience, to draw upon the
talents of my colleagues in the preparation and
conduct of the Conference, without regard to
representation by national groups or by special-
ties. This would not have been possible under
a more formal organization.

Virtually all of the contributed papers
were reproduced and distributed to the partici-
pants well in advance of the Conference. It was
thus not necessary for any papers to be given
orally at the Conference. Rather, the papers
were grouped according to the following subjects:
(1) Distribution, (2) Migrations, (3) Subpopula-
tions, (4) Behavior, (5) Tuna Oceanography, (6)

Taxonomy and Nomenclature, and (7) Background
Papers, and there were half -day discussions of
each subject, except (7). Each discussion group
was provided with a Discussion Leader and a
Rapporteur. Summary records of each discus-
sion were available on the following day, when
they were read, modified if necessary, and ac-
cepted by the Conference.

Resolutions were based upon problems
and needs identified during the course of the
Conference and upon the findings of the two
Working Groups, one on Taxonomy and Nomen-
clature and the other on Identification of Larval
and Juvenile Tunas. The Resolutions were read
on the last day of the Conference, modified if
necessary, and accepted by the Conference.

The physical record of the Conference,
i.e., the Discussion Summaries, the Resolu-
tions, and the Abstracts of Contributed Papers,
contained in the following pages may be judged
on its own merits. It is more difficult to judge
the intangible benefits which will accrue over
the years from the personal contacts established
during the course of the Conference, with re-
sulting improveme nts in communication between
widely separated laboratories.

The success of a Conference of this na-
ture is dependent upon those who participate in
it. I wish to express my appreciation to all who
found it possible to attend and who contributed
so freely to the discussions. I wish also to ac-
knowledge my debt to all of my immediate col-
leagues in the Bureau, without whom it would
have been impossible to arrange and carry out
the Conference.

PROGRAM

August 14 - Monday

9:00-10:00 Registration
10:00-10:30 Opening business

Chairman: John C. Marr
10:30-12:30 Taxonomy and Nomenclature

Discussion Leader: Phil M. Roedel
Rapporteur: Walter M. Matsumoto
12:30- 2:00 Lunch
2:00- 5:00 Distribution

Discussion Leader: Donald W. Strasburg
Rapporteur: Robert T. B. Iversen

August 15 - Tuesday

9:30-12:30 Migrations

Discussion Leader: Tamio Otsu
Rapporteur: Eugene L. Nakamura
12:30- 2:00 Lunch
2:00- 5:00 Behavior

Discussion Leader: John J. Magnuson
Rapporteur: Everet C. Jones

August 16 - Wednesday

8:00- 5:00 Demonstration cruise on CHARLES H. GILBERT; live -bait skipjack fishing, under-
water observation chambers

August 17 - Thursday

9:30-12:30 Subpopulations

Discussion Leader: Lucian M. Sprague
Rapporteur: Richard N. Uchida
12:30- 2:00 Lunch
2:00- 5:00 Available for working groups

August 18 - Friday

9:30-12:30 Tuna Oceanography

Discussion Leader: Thomas S. Austin
Rapporteur: Kenneth D. Waldron
12:30- 2:00 Lunch
2:00- 5:30 Open House, U. S. Bureau of Commercial Fisheries Biological Laboratory. Ex-
hibit of scientific illustrations by Tamotsu Nakata (Room 221)

August 19 - Saturday

9:30-12:30 Closing business

Chairman: John C. Marr
5:00-11:00 Luau, U. S. Bureau of Commercial Fisheries Biological Laboratory.

SUMMARY REPORT OF DISCUSSIONS

Taxonomy and Nomenclature

Discussion Leader - Phil M. Roedel
Rapporteur - Walter M. Matsumoto

Reference: Papers No.

VI - 1. Collette, B. B. - A preliminary review of the tunas of the genus Thunnus

2. Roedel, P. M. , and J. E. Fitch -Taxonomy and nomenclature of the Pacific
tunas

In spite of the tremendous amount of at-
tention given the tunas in recent years, the basic
problems of taxonomy and nomenclature are still
unresolved. Several things have contributed to
this; for example, many of the past descriptions
are too brief, the localities of capture are often
vague, and the taxonomy of the group is often
approached from a geographically narrow point
of view. As a result, a multitude of names ex-
ist for fish which could well be of the same spe-
cies but were simply taken in different parts of
an ocean or indifferent oceans. To further com-
plicate matters there are today two schools of
thought among taxonomists with regard to the
tunas: (1) those who recognize the existence of
numerous species indifferent parts of the world
and (2) those who contend that there are only a
few species widely distributed throughout the
world.

The purpose of the open discussion was
to identify the various problems concerning the
taxonomy of the tunas and to find solutions to
these problems or decide upon the best means
by which they could be solved.

Several problems, two in the form
of questions, were brought out during the
discussion:

1. How many genera are there among
the tunas ?

2. How many species comprise the
tuna?

3. Difficulty in defining genus.

1. It was pointed out and generally ac-
cepted that there is no reason to split the tunas
taxonomically to the point where each species is
given a generic name. This means that such ge-
neric names as Parathunnus , Neothunnus, and
Kishinoella should be replaced by Thunnus.
Other genera (Euthynnus, Katsuwonus, and Auxis)
were not discussed.

2. The single -species concept was
strongly advocated for yellowfin, bigeye, alba-
core, and skipjack. It was also felt that T.
tonggol and T. atlanticus are valid species . One
exception to this single -species concept was
pointed out in the bluefins. The Pacific T_.
orientalis and the Atlantic T. th_ynnus were sug-
gested to be subspecies on the basis of gillraker
counts. Here again, species of two other genera,
Euthynnus and Auxis, were not discussed.

3. While it was clearly recognized that
the problem is extremely subjective and, there-
fore, difficult for researchers to come to any
agreement on, it was pointed out that some de-
gree of objectivity was possible in taxonomic
works. Inthecaseof species there may be evi-
dence of reproductive isolation. The use of se-
rology in separating tunas on the generic level
was suggested. It was felt that this technique
has some possibility, even though the problem
is not solvable at this time.

Although there was general agreement
on the greater portion of the species and genera
discussed, evidence of some reservations was
clearly displayed when suggestions for carrying
out further work in clarifying the taxonomic
problem were offered. The consensus was to
appoint a well -qualified person or committee to
prepare a thorough background paper for the
FAO World Tuna Conference and to determine
whether or not there is need for more data.

In connection with the need for more
data, Hiroshi Nakamura kindly offered his co-
operation in collecting specimens of various spe -
cies of tunas from all oceans of the world in
which Japanese fishing operations are being
carried on at the present time.

At this point, with further work to be
done on some of the problems and in order to
formulate recommendations wherever needed, a
working group was appointed consisting of
Phil M. Roedel, Chairman, John C. Marr,
Hiroshi Nakamura, and Robert H. Gibbs, Jr.

Distribution

Discussion Leader - Donald W. Strasburg
Rapporteur - Robert T. B. Iversen

Reference: Papers No.

I - 1. Nakamura, H. - An outline of the tuna longline grounds in the Pacific

2. Kamimura, T., and M. Honma - Distribution of yellowfin in the longline fishing
ground in the Pacific Ocean, especially on the regional variation of the density
in each size group

3. Mimura, K. - Studies on Indo-maguro

4. Clemens, H. B. - The distribution of California bluefin tuna in the easternNorth

Pacific

5. Clemens, H. B. - The distribution of albacore in the North Pacific

The initial discussion centered on long-
line fishing in the Pacific and Indian Oceans. It
was brought out that the Pacific Ocean in general
is marked by a series of current systems extend-
ing in an east -west direction. These current sys-
tems are characterized as distinct environments
with distinctive fisheries. For example, the
North Pacific Current north of 28° N. is noted
for heavy catches of albacore, while the area
from 5° N. to 10° S. (parts of the Equatorial
Countercurrent and the South Equatorial Ourrent)
is noted for heavy catches of yellowfin. Migra-
tions of tunas in these current systems were
hypothesized as occurring (a) within current sys-
tems, where the movements are slow and easy
to follow, and (b) between current systems,
where they are rapid and difficult to follow. Evi-
dence for (b) is the abrupt seasonal change in the
size composition of the catch.

The next phase of the discussion pointed
out there was considerable variation in the abun-
dance of tunas according to years. For example,
the 1953 catch of albacore was good, relative to
the catch in an average year, and catches of big-
eye tuna were also good then. The 1953 catch was
attributed in part to the dominance of 5-year-old
albacore. It was also noted that 1953 was an
atypical year in many other ways. El Nino off
western South America was well developed, tuna
catches in the eastern Pacific were affected, the
Equatorial Countercurrent was weak, Chinook
and sockeye salmon catches were poor, and the
eastern Pacific was abnormally warm.

North -south hemispheric differences
were shown to exist in longline catches. In gen-
eral, catches of tunas and marlins were heaviest
in the Southern Hemisphere . The significance of
this is unknown.

The discussion then shifted to the length
distribution of yellowfin in various regions of the
Pacific longline grounds. Catch data were clas -
sified by length, area, and season. Yellowfin
smaller than 120 cm. were largely restricted to
waters of east longitude, while fish larger than
140 cm. were mostly distributed in waters of
west longitude. Intermediate -sized fish, 121-140
cm., were widely distributed, showing a rela-
tive shift inabundance to the east when compared
to the small fish. This shift in size was present
throughout the year, with no marked seasonal
differences. Three possible artificial causes
for it were evaluated: effect of fishing, gear

selectivity, and the location of the fishing grounds
with respect to land masses. The difference in
size groups was hypothesized as a migration of
the smaller yellowfin from west to east. It was
suggested that the shoaling thermocline to the
east in equatorial waters may be responsible for
bringing the larger yellowfin into the depth range
of the longline. It was further pointed out that
returns from tagging in the western Pacific have
been mostly short term (i.e., 1 year or less) .

Indian Ocean bluefin tuna, fished by the
Japanese in waters north and west of Australia,
have recently become the object of an important
longline fishery. There are two grounds for
these bluefin, clearly separated from each other.
The Old Fishing Ground is located between the
Lesser Sunda Islands and Australia and, since
1958, the New Fishing Ground off the Australian
west coast from 20° S. - 30° S. No bluefinhave
beenfound peripheral to these grounds, and only
scattered fish are found on the grounds outside
the months of September through April. The
catch rate in the Old Fishing Ground has two
peaks, one in September - October and the other
in February. On the New Fishing Ground the
single peak occurs in January - February and is
twice as great as those of the Old Fishing Ground.
The size of bluefin taken on the Old Fishing Ground
is uniformly large throughout the season, while
on the New Fishing Ground their size decreases
at the height of the season. Bluefin on the Old
Fishing Ground have relatively large gonads
(1,000 -4,000 g.) throughout the season, while
fish on the New Fishing Ground have gonads
mostly smaller than 1, 500 g. , with a change in
relative size at various times during the season.
It was pointed out that gonads from large western
Atlantic bluefin are difficult to evaluate by the
method of gonad weight because they contain a
large amount of fat. Western Atlantic bluefin
make a seasonal migration, a situation also hy-
pothesized for these two groups of Australian
bluefin.

The bluefin tuna of the eastern North
Pacific is taken primarily in coastal waters, in
contrast to the North Pacific albacore, which is
primarily a pelagic species . Both species range
from Baja California to Alaska, and both are the
object of seasonal fisheries off the west coast of
the United States and Baja California. The size
of bluefin caught in the last 50 years has changed
considerably. In the early 1900' s, many large
bluefin (200 - 300 lb.) were caught by sports

fishermen. During the last 20 years the catch
has been mostly fish of 25 - 30 lb. or less.
Since 1958, some large bluefin (>100 lb.) have
reappeared in the catch. California bluefinmay
inhabit either warm, high-saline water, such as
is normally occupied by yellowfin, or the cold,
low-saline water characteristically inhabited by
albacore, but they occur mostly in water with
temperature -salinity characteristics intermedi-
ate betweenthese two. In years when ocean tern -
peratures are unusually warm, the California
bluefin ranges hundreds of miles farther north.
It was agreed that a cause -and -effect relation-
ship between distribution and ocean temper-
ature should not be postulated without further
investigation.

It was stated that bluefin leave the
California coastal area for spawning, since there

is an absence of sexually mature adults, eggs,
and larvae in this area. H. Nakamura presented
evidence for a possible continuous distribution
of bluefin across the Pacific.

To further our understanding of tuna
distribution, it was felt that increased emphasis
should be given to tagging of small tunas in the
western and North Pacific, of albacore off South
America, and of southern Australian bluefin.
The design of exploratory fishing surveys uti-
lizing special equipment was recommended. We
can expect further knowledge to result from
studies on migration, subpopulations , behavior,
and oceanography, all of which relate to
distribution.

Migrations

Discussion Leader - Tamio Otsu
Rapporteur - Eugene L. Nakamura

Reference: Papers No.

II - 1. Otsu, T., and R. N. Uchida - A model of the migration of albacore in the North
Pacific Ocean

2. Clemens, H. B. - Migration, age and growth, and spawning studies of the North
Pacific albacore (Thunnus germo)

A model was presented of the migration
of albacore in the North Pacific Ocean, based on
tag recovery data, age and growth data, and dis-
tribution and size frequency data from the three
major albacore fisheries: the Japanese live -
bait fishery, the Japanese longline fishery, and
the American west coast trolling and live -bait
fishery. This model is consistent with the hy-
pothesis that there is a single population of alba-
core throughout the North Pacific Ocean.

Discussion of the albacore tagging data
brought forth remarks that young bluefin in
Australian waters ought to be tagged to see if
they would appear in the Japanese longline fish-
ery in equatorial waters. Agreement was
expressed by others with further remarks con-
cerning the desirability of tagging the young of
all species of tuna to help solve distributional,
growth, and taxonomic problems of the various
species .

Further discussion about small albacore
centered around the 35 -cm. modal group. It was
stressed that one should be aware of the fact that
even though 35-cm. fish are present they may

not be fished for economic reasons, particularly
if larger fish are available.

A suggestion was made that in viewof the
amount of information available from the various
laboratories studying albacore, a joint effort
should be made to define more clearly the prob-
lem of assigning absolute ages to modal groups.

The view was expressed that there may
be some danger in assuming that recruitment
occurs only in the eastern Pacific. There was
general agreement that the major spawning area
is in subtropical waters, but which way do the
newly hatched fish go? What size are they when
they enter the postulated migratory routes? At-
tention should be directed toward the smaller
fish, particularly the 35-cm. modal group.
These fish have been reported in the area of the
Japanese live -bait fishery by fishermen who do
not catch them for economic reasons. So per-
haps it may be better to hypothesize that recruit-
ment occurs in both the Japanese and American
fisheries. Plans are being made by the Japanese
to use special gear for catching these small fish
in the future.

The statement was then made that per-
haps discussions of recruitment involve a se-
mantic problem. One use means recruitment
into the fishery while the other means recruit-
ment into the temperate North Pacific Ocean.

The question of tagging small fish arose
again. It seems desirable to tag small albacore.
It was suggested that the salmon investigators
might be encountering small albacore in their
gill nets. However, it was believed that the
mesh sizes used for salmon were too big to
catch small albacore.

Serological evidence supports the hy-
pothesis that a single reproductive population of
albacore exists in the North Pacific Ocean.

The subject of depth of albacore occur-
rence was discussed next. In both the Japanese
live -bait fishery and the American fishery, the
fish are caught at the surface. In the longline
fishery, the albacore are caught with gear fish-
ing down to 100 meters . The depth of occurrence
may be associated with the depth of the mixed
layer. Japanese longline fishermen adjust the
depths of the hooks depending upon the area
fished.

In connection with depth of occurrence,
the suggestion was made to further develop the
idea of a depth gauge which could be attached
directly to the fish. If a miniature type of bathy-
thermograph could be developed, it could help
solve problems of vertical distribution. Such
depth gauges, which must be inexpensive, small,
and calibrated after recovery, were worked upon
by Bureauof Commercial Fisheries technicians
at Seattle, but lack of interest and research
funds brought an end to the project.

A method that has been used in Japan to
determine the depth of fish occurrence was de-
scribed. The gear consisted of a float attached
to each branch line. It was implied that the fish
could not have been caught at a depth deeper
than the length of the line. In the Celebes Sea,
yellowfin were caught as deep as 160 m. , but
most were caught at 100 m. Marlin catches were
best at 70 to 80 m. , and shark catches at 30 m.
However, the work of gear handling was increased
greatly so that not as many units could be fished
as normally.

The use of echo sounders for determining
hook depths was mentioned, and a design for a
sonic reflector tag for skipjack was described.

Vertical distribution of tuna in relation
to oceanographic factors was also discussed,

such factors being internal waves, the deep scat-
tering layer, and temperature discontinuities.

It was pointed out that there was basic
agreement between the two reference papers and
that the major difference was in the assignment
of absolute ages to the various modal groups.
Another difference was that Clemens' paper pos-
tulated that some albacore of all sizes remain
in the central Pacific without migrating either
eastward or westward. The paper by Otsu and
Uchida does not so postulate, although available
data would tend to support Clemens.

Clemens' estimation of albacore age is
1 year less than that of Otsu and Uchida. The
possibility of the difference being due to a differ-
ent assumed spawning season was expressed.
Clemens believes that the youngest fish entering
the American fishery are really about 15 or 16
months old. In addition to other data, Clemens
read scales from near the caudal peduncle to
estimate age. Slides were shown of albacore
scales from the peduncle of a 59-cm. fish which
had one annulus, a 69 -cm. fish with two annuli,
and a 75-cm. fish with three annuli. It was
stated that scale readings of albacore in
Japan were in agreement with the California
studies. The opinion was also expressed that
because scales in the peduncular area are the
last to develop in a young fish, the first annulus
may be so compact and small in radius that it may
be overlooked. A comparison was made of the
albacore growth curves of Clemens and of Otsu,
and both are nearly identical for fish sizes above
50 cm. A statement was made that in the Atlantic
yellowfin and bluefin the first year's growth is
in the neighborhood of 30 cm.

The discussion then turned to triggering
mechanisms for migration. Two areas of search
for this triggering mechanism were suggested:
in the environment and within the organism. It
was then suggested that the two probably inter-
act, that an environmental mechanism (extrin-
sic factor) interacts with an internal mechanism
(intrinsic factor). That extrinsic factors may
be temperature or length of daylight was dis-
cussed. An example of the importance of length
of daylight was given for the maturation of the
ayu in Japan. It was suggested that the intrinsic
factor is possibly associated with the endocrine
system, as has been shown in salmonids.

The final discussion involved the use of
commercial landings as indicators of presence
or absence of albacore. It was pointed out that
lack of commercial landings need not mean the
absence of albacore, but rather the lack of en-
counter between fishermen and fish, whether it
be due to inclement weather or something else.

Discussion Leader - John J. Magnuson
Rapporteur - Everet C. Jones

Reference: Papers No.

IV - 1. Strasburg, D. W. - An aerating device for salt well water

2. Nakamura, E. L. - The establishment and behavior of skipjack tuna (Katsuwonus

pelamis) in captivity

3. Yuen, H. S. H. - Experiments on the feeding behavior of skipjack at sea

Behavior has been defined as the total
movements of an intact animal. More recently
the field has been broadened to include the study
of these movements relative to physiology, ecol-
ogy, and phylogeny. From a practical view-
point, behavior studies may provide information
useful in developing fishing gear, in predicting
a tuna's location in time and space, and in under-
standing behavioral mechanisms which have con-
sequences in population dynamics.

Observations of skipjack both in captivity
and in the field indicate that certain color changes
and fin movements are associated with feeding.
Transient vertical bars observed on skipjack
appear to result from the contraction of melano-
phores in vertically oriented zones on the sides
of the fish, producing a pattern of alternate light
and dark bars. The speed of these changes indi-
cates nervous control rather than endocrinalcon-
trol. Such transient vertical bars have been
observed on other large pelagic fishes in the
living state, but fade on dead or dying fishes .
Vertical bars are a common non-transient pat-
tern on juveniles of many fish species.

Various people have observed reddish
colored skipjack; perhaps this is a spawning
coloration. A more commonly observed pattern
is one of bright blue horizontal streaks on the
dorso-lateral surface. It was suggested that
these blue streaks may be fluorescent or lumi-
nescent. Since this color is not observed on dead
fish the possibility of iridescence was questioned.
Transient color patterns, together with erection
of the first dorsal fin (resulting in the prominent
display of the white leading edge) and opening of
the mouth (resulting in the display of the silvery
tongue), may be social releasers . The possibil-
ity that these changes are involved in communi-
cation among fish opens up new fields of research.
Avenues of investigation included the use of arti-
ficial skipjack painted in appropriate colors to
test the reactions of both captive and wild fish.

The feeding response of skipjack at sea
appears to be influenced by the quality of the

stimulus, i.e., the characteristics of the bait
species used. It is possible that a sufficiently
attractive bait fish might actually attract the
tuna away from the hooks and result in a lower
biting rate. Experiments have been conducted
in Hawaii using dead bait fish because of the
scarcity of live bait. Both the catch rate and
feeding response of skipjack were less with dead
bait than with live bait, butyellowfin tuna in the
eastern Pacific react to such inanimate material
as macaroni, rice, or nails. The Galapagos
fishery was started on dead bait.

Large schools of many species of pelagic
fishes, including the tunas, have often been ob-
served to be associated with floating logs, boxes,
ordriftwood. In the Atlantic , blackfin tuna have
been observed associated with whale sharks,
and various tunas in the Pacific have been ob-
served associated with porpoises. It is a com-
mon practice of fishermen to investigate floating
material to locate schools of tuna. In Japan,
skipjack did not aggregate under driftwood which
was planted at sea for that purpose. Ahypothe-
sis putforwardto explain the association between
fish schools and logs or driftwood was that the
floating object attracted small fish which were
preyed upon by the large fishofthe school. Ob-
jections to this idea centered about the obser-
vation that the schools of predaceous fish under
floating objects were often too large t o be
attracted by a few small fish. A counter sug-
gestion was made that we do not know the rate at
which small fish accumulate and that it may be
greater than presently expected.

Skipjack schools in the Japanese fishery
have been observed to extend from 100 to as
much as 1,000 meters from the driftwood and
to move inandout from it. In Hawaii, 3 months
of investigation of floating wood resulted in no
observed association with skipjack. Dolphin
(Coryphaena) were often seen in such association,
but examination of stomach contents indicated
that they were not feeding onKyphosus, the small
fish most often found under driftwood, but were
feeding on trunkfish and flying fish.

In the Philippine fishey, floating objects
are used to help "lure" or guide skipjack toward
the mouth of large traps. This practice appears
to be associated with the presence of deep, nar-
row channels between islands.

Techniques of observation must be re-
lated to whether the investigator is studying the
behavior of individual fish or the behavior of
schools offish. For the former, direct obser-
vation of a detailed image is necessary; the use
of movies appears to be the best technique be-
cause it allows more detailed analyses. For
studying fast-moving tuna, fast shutter speeds
and fast film are required to prevent blurring.
The desirability of securing much more footage
of movies of tuna was pointed out. Vessels hav-
ing underwater viewing facilities are particularly
useful in this work.

In the observations of fish schools, sonar
instruments are useful. Other possibilities in-
clude the use of aerial observations with movies
of schools being fished. Airplanes are standard
equipment in the North American west coast
fisheries. In Hawaii, attempts to use aircraft
for scouting have not been successful because of

sea surface glitter and rough seas. In the At-
lantic, movies of tuna schools have been taken
from a slow-flying aircraft flying at 20 feet and
at 30 - 35 miles per hour.

Relating the studies of anatomy and be-
havior appears to be a useful approach, particu-
larly in the case of fishes that are difficult to
observe directly . Examples mentioned included
the hypothesis that the ratio of rods and cones
in the retina may be related to the amount of
light in the usual environment; that the presence
or absence of a swim bladder may be related to
diving behavior; and that the presence of vascu-
lar anastomoses may be a mechanism of blood
flow control related to diving behavior.

Studies of the internal body temperature
taken in live tuna indicate that it is consistently
1 to 5° C. higher than the water temperature.
Just what part of this difference is associated
with the unusual exertions of being caught and
what part is normal has not been determined.
Because it is difficult to take thermometer ob-
servations of "normal" fish, the use of infrared
heat detection was suggested as a useful tool.

Subpopulations

Discussion Leader - Lucian M. Sprague
Rapporteur - Richard N. Uchida

Reference: Papers No.

Ill - 1. Legand, M. - Biometric data on yellowtin tuna in New Caledonia

2. Suzuki, A. - Blood types in tuna

3. Fujii, Y., K. Mimoto, andS. Higasa -Biochemical studies on the races of tuna

base composition of testis deoxyribonucleic acid (DNA)

4. Marr, J. C, and L. M. Sprague - The use of blood group characteristics in

studying subpopulations of fishes

5. Ridgway, G. J. - Distinction of tuna species by immunochemical methods

6. Royce, W. F. - A morphometric study of yellowfin tuna Thunnus albacares

(Bonnaterre)

7. Hiyama, Y., and K. Kurogane - Morphometrical comparisons of tuna from areas

in the Pacific and Indian Oceans

8. Sprague, L. M. , and L. I. Nakashima - A comparative study of the erythrocyte

antigens of certain tuna species (Abstract)

9. Sprague, L. M. , and L. I. Nakashima -Studies on the erythrocyte antigens of

the skipjack tuna (Katsuwonus pelamis)

10. Sprague, L. M. - Blood group studies of albacore (Germo alalunga) tuna from
the Pacific Ocean

Legand, M. - Some biometric data on the albacore of the region west of New
Caledonia

The discussion was divided into three
main categories depending on the methodology:

A. Chemical methods

1. Biochemical

velopment of a suitable method for use in the
identification of larval forms of tuna. The study
has shown that the method of diffusion precipitin
analysis demonstrated the presence of species -
specific differences in serum antigens of adult
tuna.

2. Immunochemical

B. Morphometrical methods

C. Serological methods

A. (1) Discussion centered on the bio-
chemical studies on the races of tuna by analysis
of the base composition of testis DNA (deoxyri-
bonucleic acid). It was brought out that DNA is
implicated as the substance primarily responsi-
ble for the transmission of hereditary character-
istics at the molecular level. In most samples
of DNA, four heterocyclic bases predominate.
For the purines, these are adenine and guanine,
and for the pyrimidines, they are thymine and
cytosine. These bases are bound together on a
chain of deoxyribose sugar together with certain
phosphate residues, and the chain forms the
chemical backbone of the DNA molecule.

It has been demonstrated that the values
of the base pairs adenine and thymine divided by
the values of the base pairs guanine and cytosine
yield ratios which are quite different for some
tunas. Studies on bigeye, yellowfin, Indo-maguro
and Goshu-maguro yielded ratios which ranged
from 1. 26 to 1.75.

The conclusion was reached that the
ratio of the base pairs of the DNA molecule may
in the future provide an indication of the racial
relationships of the tunas .

It was noted that a similar study of differ-
entiating the racial stocks of tuna by electron -
micrographic comparisons of tuna spermatozoa
was being carried on by the Inter-American
Tropical Tuna Commission. In this study the
potentiality of telling racial stocks apart depends
on differences in sperm morphology.

Cushing endorsed further exploration on
the subject of DNA as a tool for differentiating
subpopulations of tunas . A paper model of the
DNA molecule was shown the conferees, and its
structure was briefly explained.

A. (2) Discussion centered on the im-
munochemical method. The study involved de-

The study has revealed that there is at
least one distinctive antigen which may be used
as a diagnostic antigen for individual species of
tuna.

The conclusion was reached that there
are definite possibilities in the application of
immunochemical methods to the problem of iden-
tifying larval forms. The usefulness of this
method, however, depends on the development
of species specificity in antigenic constitution
early in embryological development.

Discussion brought out that immuno-
chemical methods may be useful in studying the
taxonomic relations between species of fishes.
Their use may provide additional information in
distinguishing species and, when combined with
red blood cell studies, may be a very sensitive
and useful tool in taxonomic studies.

The question was raised whether this
method would be useful in distinguishing the tuna
larvae, which have only a very small amount of
blood. It was stated thatthereare refined tech-
niques for dealing with organisms with a small
amount of blood, but the techniques are very time-
consuming and expensive. It was stated that
fresh specimens should be used in immunochem-
ical studies, and sample size should be as large
as possible so that statistical tests can be made.

The conclusion was reached that sero-
logical studies can be useful in verifying the con-
clusions reached by systematic studies. The
suggestion was made that a study of the American
and European eel problem be carried out by
these methods.

B. Hiyama noted that there were only
small differences in the body characters of the
northwest Pacific albacore which form the basis
of the Japanese winter longline and summer live-
bait fishery. When northwest Pacific albacore
were compared to the albacore from the equa-
torial and southwest Pacific areas, there were
distinct differences. The albacore from the
equatorial and southwest Pacific were morpho-
metrically similar. The Indian Ocean albacore
were found to b e distinct from the northwest

Pacific albacore; however, the conclusion was
that there was possibly some mixing between the
Indian Ocean and southwest Pacific albacore.

In respect to yellowfin, Hiyama concluded
that morphometrically there are at least three
independent populations in the equatorial Pacific
betweenl30° W.andl30° E. Yellowfin in waters
adjacent to the Lesser Sunda Islands were found
to be distinct from fish of the equatorial Indian
Ocean.

No conclusions were made on population
differences in bigeye because of insufficient
data.

Discussion brought out that the albacore
has the widest distribution of any of the tunas in
the Pacific and also the smallest differences
between populations. The yellowfin apparently
has small independent populations scattered over
the Pacific; the bigeye distribution is larger than
the yellowfin but smaller than the albacore
distribution.

Royce compared yellowfin samples from
the Pacific, Atlantic, and Indian Oceans. In the
yellowfin along the Pacific Equator from the
eastern Pacific to the Caroline Islands, the ex-
istence of a cline or character gradient was
noted. A sample from the Atlantic closely re-
sembled a sample taken between Costa Rica and
the Line Islands. The Somaliland sample was
the most diverse, the specimens showing particu-
larly short fins, a deep body, and a long distance
from the snout to the insertion of the ventrals.

The conclusion was that east-west migra-
tion is limited, because the overlap of samples
from along the Pacific Equator is inversely re-
lated to distance between samples; the average
overlap between samples 1, 500 miles apart was
less than 50 percent, 3,000 miles less than25
percent, and 6, 000 miles less than 6 percent.

Royce concluded that the name for
the yellowfin should be Thunnus albacares
(Bonnaterre) 1788, because the yellowfin has a
continuous distribution and also because the full
range of characters which have been used to
distinguish species occurs in the series of sam-
ples from the Pacific Equator.

Discussion on yellowfin subpopulations
brought out that among the yellowfin in the east-
ern Pacific, ranging from Baja California to
Chile, there is evidence of isolation among the
stock, with intermixing on the order of about 20
to 25 percent. North of latitude 15° N. , the
stock responds differently from stock to the south

of 15° N. An example noted was that the northern
stock spawns in summer while the equatorial
stock spawns in winter.

Discussion brought out that plastic pheno-
typic characters c a n be modified by diet and
temperature . Conditions that modify growth may
change not only from place to place, but also
from year to year. As a result, we may be
measuring the changes in the fish or changes in
the environment. It was remarked, unfortu-
nately, there is no way to separate morphological
changes due to genetic factors from those due to
the environment. However, even if the charac-
ters are phenotypic, there is still an indication
that intermingling between fish from one area
and those of another area is highly unlikely.

It was stated that knowledge of the sub-
populations of the tunas is essential, since each
population unit will respond, perhaps uniquely,
to fishing effort. Such knowledge of the popu-
lation pattern can help materially in the manage -
ment of the fishery resources.

Discussion on genetic exchange brought
out that there may be intermingling between sur-
face and subsurface aggregations and also during
the early years of life. Yellowfin were noted to
be responsive to oceanographic changes and,
under conditions of abnormal warming or cool-
ing, they may move to other areas. Thus ex-
change of genetic material may occur through
the movements of a few fish. Further evidence
of possible genetic isolation was cited. Along
the Equator from 120° E. to 110° W. there does
not appear to be much variation in spawning.
Size at maturity appears to be at about 110 cm. ,
although a few individuals between 80 to 110 cm.
may be mature. Off the American coast, how-
ever, a very large percentage of fish over 80 cm.
were found to be mature. Therefore, one might
possibly conclude that the fish in t h e eastern
part of the Pacific are of a different population
than those of the western part.

Diversity of opinion was noted among
some contributors as to the extent of inter-
mingling of yellowfin population units in the
equatorial Pacific. Because of the possible
need for management in some yellowfin fisheries
in the near future, it was thought that the inves-
tigators concerned should make special effort
to resolve this problem.

Discussion brought out that the term
subpopulation should refer to reproductive units,
and that the use of this term for aggregates of
individuals apart from this framework would
lead to confusion.

Legand summarized his biometrical
analysis of yellowfin and albacore taken in the
region of New Caledonia. He remarked that
insufficient studies havebeenmade on yellowfin
to differentiate the sexes by biometric data.
There are, nevertheless, indications that the
length of the pectoral fin may differ significantly.
This possibility should be considered particu-
larly in a serious study of the population by mor-
phometric characters. Thus in New Caledonia,
yellowfin tunas tend to have smaller heads and
larger second dorsal and anal fins than fish
caught farther east.

For albacore, it was concluded that re-
sults similar to those of Kurogane and Hiyama
were obtained from data on the northern Coral
Sea, but results were different from those ob-
tained in the northwest Pacific. Both phenotypic
and genotypic differences have been observed in
the number of anal rays and vertebrae in the
medaka (Aplocheilus latipes).

C. Antigens discussed in this section
were defined as molecules on the surface of the
erythrocyte, or red blood cell, detected by
immunological methods.

Serological comparisons of North Atlan-
tic and North Pacific albacore have demonstrated
that serological techniques can distinguish repro-
ductively isolated tuna populations.

Two blood group systems in the skipjack
are recognized, namely the A and C system.
The C system has been found in all tuna species

thus far investigated. The A system was also
present in all the tunas except the yellowfin.

Systems such as the A and C system in
the tunas would be comparable to theA-B-Oand
M-N blood groups found in man.

Students of skipjack population units in
the Pacific recognize at least two reproductively
isolated units. There is good evidence that the
North American and Samoan stocks of albacore
are reproductively isolated.

Discussion of serological studies on Pa-
cific, Atlantic, and Indian Ocean albacore dis-
closed that the Atlantic forms had a very high
percentage of positive reactions with bigeye-
antigen-3. Samples from the eastern Pacific
and Indian Ocean had a significantly lower per-
cent of positive reactions. It was indicated that
further research will be carried out.

A background study on serology and its
implications to tuna research was discussed. It
was pointed out that this is just one of the useful
tools for identifying population units . Further
discussion focused on possible exchange of ma-
terial from various parts of the world to help in
determining whether similar population units
such as those that are now being discovered for
some of the tunas can be isolated.

It was recommended that a working group
be formed to attack one particular problem from
the standpoint of biochemical, morphological,
and serological methods and to present results
at the World Tuna Conference in 1962.

Tuna Oceanography

Discussion Leader - Thomas S. Austin
Rapporteur - Kenneth D. Waldron

Reference: Papers No.

V - 1. Rosa, H. , Jr., and T. Laevastu - World distribution of tunas and tuna fisheries
in relation to environment

2. Alverson, D. L. - Ocean temperatures and their relationship to albacore tuna

(Thunnus germo) distribution in waters off the coast of the States of Oregon,
Washington, and the Province of British Columbia

3. Inoue, M. - Relation of sea condition and ecology of albacore in the northwest

Pacific Ocean. Parts I and II

4. Blackburn, M. - Distribution and abundance of eastern tropical Pacific tunas in

relation to ocean properties and features

5. Yamanaka, H. , and N. Anraku - Relation between the distribution of tunas and
water masses of the North and South Pacific Oceans west of 160° W.

6. Johnson, J. H. -Sea temperatures and the availability of albacore (Thunnus

germo) off the coasts of Oregon and Washington

7. Uda, M. - Cyclical fluctuation of the Pacific tuna fisheries in response to cold

and warm water intrusions

8. Uda, M. - Localized concentration of tunas in the eddies along oceanic fronts

9. Austin, T. S. , and R. A. Barkley - Use of oceanographic stations in fishery

research

10. Seckel, G. R., and T. S. Austin - The association between Hawaiian skipjack

landings and the oceanographic climate

11. Brown, R. P., and K. Sherman - Oceanographic observations and skipjack dis-

tribution in the North Central Pacific

In the past, and to a lesser extent at
present, only a knowledge of the broad -scale
oceanographic features was needed to study the
distribution of tunas . Our present need for more
detailed knowledge of both the horizontal and ver-
tical distribution of tunas requires a more de-
tailed knowledge of oceanographic features and
the processes involved. Two aspects of tuna
oceanography can be considered: (1) distribution,
population size, and environme nt of tunas, and
(2) prediction techniques using oceanographic
data.

On a worldwide basis there is need for
more information concerning the distribution of
the different tunas. Exploitation of new fishing
grounds and extensive exploratory fishing, to-
gether with re -examination of taxonomic prob-
lems, requires continued evaluation and revision
of charts showing distribution. Parathunnus
obesus probably occurs in the western as well as
the eastern Atlantic; Euthynnus lineatus has a
continuous distribution in the eastern Pacific
within the limits shown; and both Sarda chilensis
and S. orientalis occur in the eastern Pacific,
with a break in the distribution between about
latitudes 7° N. and 15° N. Suggestions as to the
distribution of the different species would aid in
the completion of a world distribution paper being
prepared by FAOfor the World Tuna Conference
in 1962.

In the western half of the Pacific, tem-
perature-chlorinity curves for the upper 200
meters were useful in identifying water mass
subtypes and the associated distribution of tunas
andmarlins. Water mass characteristics, iden-
tified by temperature -salinity relationships, are
useful not only on an oceanwide basis, but also
for studies within the area of a fishery. There
is need for some means of portraying
temperature-salinity relationships as a single
index of water type on a time -space basis. An

approach worth considering would be the use of
the discriminant function analysis. However,
since temperature and salinity, as measured at
the sea surface , are not conservative properties,
it appears necessary to isolate the conservative
portion of each, i.e., that portion not due to
sea-atmosphere interaction processes at the sea
surface.

Availability and abundance of tunas are
related in various ways to different aspects of
temperature in the ocean. Processes in the at-
mospheric pressure system exert an influence
on the temperature distribution in the ocean.
Skipjack, albacore, and bluefin tuna in the west-
ern and eastern Pacific show certain variations
in abundance and availability which may be
temperature-controlled. Cyclical changes in
catch and temperature in the western and east-
ern Pacific appear to vary in a reciprocal man-
ner. The proposed reciprocal relationship,
particularly with respect to a potential prediction
technique, should consider the total American
west coast landing s of albacore. The reciprocal
trend in temperature has been observed in data
from monitoring stations. Commerical catch
records show that in some years the reciprocal
trend in catch does not pertain, i.e., there may
be good catches in both the American and the
Japanese fisheries. However, caution must be
exercised in using commercial catch records
because of changes in the economics and tech-
nology of a fishery. As an example, the poor
albacore catch off Oregonand Washington in 1957
can be accounted for by a glut of this tuna in the
American and world market, resulting in a
dearth of buyers for American albacore.

A study of the possible influence of the
waters of the Equatorial Countercurrent in sta-
bilizing the biota and environment in the eastern
Pacific yellowfin and skipjack fisheries would
be valuable.

In the western Pacific, tuna are to be
found along fronts, localized in cool or warm
eddies, and in zones of upwelling. Variations
in concentration and location of these tuna are
associated with the growth, decay, and change
in position of the eddies. Such eddies are found
to be associated with the Polar Front, Subtropi-
cal Convergence, and near the Equator . Individ-
ual eddies are probably more or less transient,
but may form and disappear in a regular pro-
gression. Certain areas may be classed as
"eddy -prone . " These areas vary with latitude
and with position of the North Pacific High. In
the eastern Pacific, there are very interesting
fronts, such as the one off Cape San Lucas at
the tip of Baja California, in which the tempera-
ture change is much more rapid than in the large
frontal zones described for the western Pacific.
While the Cape San Lucas Front is semiperma-
nent, many other such sharp temperature dis-
continuities are very transient . One explanation
for the aggregation of tunas in frontal zones is
that the tuna have converged to feed on forage
organisms associated with these surface
features .

Skipjack and yellowfin of the eastern
Pacific usually occur in waters warmer than
21° C. Skipjack may also be excluded from
areas in which the temperature is greater than
28° C. Annual changes in the position of the
21° C. isotherm produce corresponding changes
in the extent of the fishery in the northern
(California) and southern (Chile) extremes . The
central area of the fishery (roughly latitudes
5° S. to 22° N.) is characterized by a shoal
thermocline, and skipjack and yellowfin are
present, with some seasonal variation, through-
out the year. Island groups located at some
distance from the mainland form other areas of
good tuna fishing with some degree of seasonal
variation.

The reasons for the aggregation of tuna
near islands are not known. There is some evi-
dence that at Clarion Island tuna may forage on
detritus -feeders such as galatheid crabs, and on
trunk fish (Lactoria). Also near Clarion Island
in close inshore waters there is no significant
correlation between phytoplankton and zoo-
plankton such as is found in other areas of
the eastern Pacific. Near the Marquesas
and certain eastern Pacific islands,
zooplankton abundance increases with proximity
to the island. This may be associated with the
lack of a surrounding reef, which would tend to
filter the runoff and remove a significant por-
tion of the nutrients. Correlation among PO4,
carbon-14, zooplankton, and climax predators
may not be apparent unless the total standing

crop of climax predators is included, rather
than that of a single species or group of species.

When using commercial catch records
to evaluate productivity in a fishery it is neces-
sary, as was previously pointed out, to consider
change in fishing methods. As an example, cer-
tain islands and areas in the eastern Pacific are
not suitable purse seine grounds because of the
presence of sharks, strong currents, or other
reasons, but they are suitable for live -bait
fishing.

During the summer, albacore off Oregon,
Washington, and British Columbia (latitudes
42° N. to 50° N.) are normally found in waters
with temperatures between 54° and 63° F. (12°
and 17° C), with the greatest concentration be-
tween 58° and 61° F. (14° and 16° C), and in
areas where the top of the thermocline is 50 to
75 feet (15 to 23 m.) below the surface. Within
these general limits, the distribution of albacore
may be associated with feed or other biological
determinants. Control of distribution within
rather broad temperature limits by factors other
than temperature applies not only to albacore in
temperate waters but also to tunas in tropical
waters. To the south, off California, albacore
are found in waters with temperatures between
57° and 70° F. (14° and 21° C), with albacore
less than 20 pounds in weight most abundant in
57° to 65° F. (14° to 18° C.) water, and those
above 20 pounds most abundant in 65° to 70° F.
(18° to 21° C.) water. Thus the upper distribu-
tional limit of albacore in 62° F. (17° C.) water
in the northern area merely indicates a lackof
warmer waters. However, reduced commercial
catches during years of favorable water tempera-
tures, 58° F. (14° C.) or above, in the northern
waters should not always be construed to indi-
cate a scarcityof albacore. Economic or mar-
ket conditions may act to prevent or discourage
the formation of a fishery when albacore may in
fact be abundant. A particular problemconcern-
ing the use of commercial catch statistics is that
such records often indicate only the port of land-
ing, not the actual catch area, which may be
hundreds of miles away, e.g., albacore caught
off California may be landed in Oregon or
Washington.

The shallow thermocline mentioned above
may act as a physical barrier limiting the verti-
cal migration of albacore. It is likely that gill
nets and purse seines are most successful under
such conditions. In certain areas, as in the
eastern tropical Pacific, temperature may not
be the only barrier to vertical migration. Re-
duced oxygen content of thermocline waters
may also have an effect in inhibiting the descent

of tuna into this layer. It is thought that yellow-
fin are especially sensitive to decreased oxygen
pressure, and even under normal conditions are
near the upper threshold of oxygen utilization.
This latter hypothesis is based on a lowrecovery
rate for yellowfin tagged and released in very
warm waters. It h a s been hypothesized that
larval tuna entering the thermocline layer suffer
a high mortality due to low temperatures or lack
of oxygen. Another explanation could be a re-
duced growth rate, with a subsequent increase
in length of larval life and prolonged exposure
to the hazards of larval life. Whether or not
larval tuna have sufficient energy to overcome
the marked change in density at the surface
layer-thermocline interface should be consid-
ered as a factor limiting their vertical distri-
bution. Considerable evidence from larval tuna
collections indicates that most larvae are found
above the thermocline.

One of the objects, but not the only one,
of studies of oceanography as related to tuna is
to be able to predict the amount of tuna available
to commercial fishermen in a particular locality
and at a particular time. While studies have not
progressed to the extent that this objective can
be fully realized, prediction techniques have
been developed and are in use.

In studying the availability of albacore to
the Oregon and Washington fishery (latitudes 40°
to 50° N. , and west from the coast to longitude
130° W.) it was found that above average catches
were associated with above average August sea
surface temperatures . Similarly, below average
catches were made during years with below aver-
age temperatures for August. Further studies
suggested that the August sea surface tempera-
ture, and thus the potential availability of alba-
core, could be predicted from a consideration
of the temperature anomaly during May and June
(the amount by which the monthly temperatures
for the individual year differed from a 12 -year
monthly average). It is pertinent to note that
in at least one instance when the August
temperature -total catch relationship failed to
develop, 1957, it is likely that the low catch was
due, at least in part, to economic conditions
rather than to a lack of fish.

It has been hypothesized that albacore
available to the Japanese winter longline fishery
make a vertical migration in the spring and be-
come available to the Japanese summer live-
bait fishery. Horizontal distribution of tempera-
ture of the surface waters during the winter
appears to affect the migration of albacore from
the longline fishery into the pole -and -line fishery.
The variations and persistence of warm and cool

water, winter to summer, together with the lo-
cation of the winter longline fishery, appear to
form a basis for predicting the location and
abundance of albacore available to the summer
live -bait fishery.

During some years in an area south of
Japan (latitude 28° to 36° N., longitude 135° to
140° E.), cold inshore waters intruding from the
north force the winter fishery to operate in the
eastern and southern portions of the area. This
cold water also forces the spring migration of
albacore into an easterly and southerly direction,
and as a result the fish are available to the fish-
ery for only a short period of time, and catches
tend to be below average. In other years, when
warm water is adjacent to the coast, the winter
fishery develops close to land, and the spring
migration moves through the western and north-
ern portions of the area. As a result albacore
remain available to the pole -and -line fishery for
an extended period of time. A third situation in
which the relative persistence of winter condi-
tions may be used to predict the success of the
summer fishery involves a combination of the
two situations described above.

In the area east of Japan (latitude 30° to
40° N. , longitude 140° to 160° E.), a successful
summer live-bait fishery depends upon the ab-
sence of cold water inshore and the formation of
multiple pools of albacore in the winter longline
fishery. When these fish migrate to form a sin-
gle large aggregation in the western portion of
the area, a good fishery is likely to develop. The
catch from the live -bait fishery is likely to be
small when cold water is present in inshore
areas, when the winter aggregations of albacore
are in the eastern portion of the area, and if the
fish do not form a single aggregation in the
spring.

From these descriptions it can be seen
that in both the southern and eastern Japanese
fisheries a knowledge of winter temperature
patterns and winter fish distribution provides a
predictive technique for evaluation of the degree
of success which may be expected in the summer
live -bait fishery.

The magnitude of the annual catch made
by the Hawaiian live -bait skipjack fishery has
been shown to be related to the time of the late
winter reversal from cooling to warming of the
surface waters in the area of the fishery . It was
observed that when the time of first warming
occurred during February or earlier a better
than average skipjack catch in the Hawaiian fish-
ery could be expected. When the warming oc-
curred in March a poor catch could be expected.

Hindcasting proved this technique to be validfor ciated with the dynamics of the circulation sys-

an 8-year period. In addition the magnitude of tem in Hawaiian waters, it is not surprising that

the catch has been successfully predicted for 3 an index based on the first derivative curve of

years. Since fishing success seemsto beasso- the temperature has been the most reliable.

Background Papers
Reference: Papers No.

VII - 1. King, J. E., and R. T. B. Iversen - Midwater trawling for forage organisms
in the central Pacific

2. Otsu, T. , and R. J. Hansen - Sexual maturity and spawning of the albacore in

the central South Pacific Ocean

3. Legand, M. - Length, sex ratio, and sexual maturity of yellowfin tunas at New

Caledonia (Part 1 of Rapport Scientifique No. 11 of the Centre d'Oceanographie,
Institut Francais d'Oceanie). (In French)

4. Legand, M. , and R. Desrosieres - Preliminary investigation of the stomach

contents of yellowfin tuna of the coasts of New Caledonia (Part 2 of Rapport
Scientifique No. 11 of the Centre d'Oceanographie, Institut Francais d'Oceanie).
(In French)

5. Suda, A. - Comparison of abundance between albacore and bigeye in the north-

west Pacific

6. Yabe, H. , and S. Ueyanagi - Contributions to the study of the early life history

of the tunas

7. Yabuta, Y. , and M. Yukinawa - Age and growth of yellowfin tuna

8. Kikawa, S. - Studies on the spawning activity of the Pacific tunas Parathunnus

mebachi and Neothunnus macropterus by the gonad index examination

9. Matsumoto, W. M. -Identification of larvae of four species of tuna from the

Indo-Pacific region. I.

10. Iversen, R. T. B. - Food of albacore tuna, Thunnus germo (Lacepede), in the

central and northeastern Pacific

11. Uchida, R. N. , and T. Otsu - Analysis of sizes of albacore occurring in various

Pacific fisheries - a preliminary report

12. Bell, R. R. - The age composition of the California Pacific albacore catch

13. Watson, Margaret E. , and F. J. Mather, III - Species identification of juvenile

tunas (genus Thunnus) from the Straits of Messina, Northwestern Atlantic, and
the Gulf of Mexico

14. Legand, M. , and B. Wauthy - Presumed importance of Alepisaurus sp. in the

biological cycle of longline caught tunas in the neighborhood of New Caledonia
(In French)

15. Legand, M. - Stomach contents of albacores and yellowfins captured by long-

line by Orsom III (In French)

16. Legand, M. -Size, sex ratio, and seasonal cycle of maturation of albacore west

of New Caledonia (In French)

These contributions were not discussed course of the six discussion groups,

as a unit, but were drawn upon freely in the

Working Group Report on Identification of Larvae and Juveniles

W. M. Matsumoto - Chairman

S . Ueyanagi

W. Klawe

M. Watson (Mrs.)

H. Nakamura, Observer

W. G. Van Campen, Interpreter

Reference: Papers No.

VII - 6. Yabe, H. , and S. Ueyanagi - Contributions to the study of the early life history
of the tunas

9. Matsumoto, W. M. - Identification of larvae of four species of tuna from the
Indo -Pacific region. I.

13. Watson, M. E. , and F. J. Mather, III -Species identification of juvenile tunas
(genus Thunnus) from the Straits of Messina, Northwestern Atlantic, and the
Gulf of Mexico

Perhaps the phase of tuna life history
about which we have the least information is the
period beginning with spawning and ending prior
to the time the young enter the fishery . In order
to fill this gap, studies of tuna eggs, larvae, and
juveniles are undertaken. A prerequisite of these
studies is the positive identification of species at
the various stages of development. The purpose
of the Working Group meeting, therefore, was
to discuss the validity of species identification
of larval and juvenile tunas as presented in the
several papers, to point out differences of opin-
ion, and to make recommendations regarding
these differences. It was also the intention of
the committee to delve into the methods and gear
for collecting tuna in the early stages of growth.

Identification of Larvae

It was pointed out that the two papers on
larval tuna identification were not in agreement
concerning two species, albacore and bigeye.
Of the species which were described in both pa-
pers, general agreement was found for one spe-
cies, T. orientalis . Concerning the point of
difference, the authors of the first paper felt that
two types of larvae (A and B) could be distin-
guished from among the larvae which had no pig-
ment spots either on the dorsal or ventral edges
of the trunk (similar to yellowfin), primarily by
the locality (between 10° N. and 25° N.) and time
of capture, relative body width, and pigmentation
on the tips of the jaws.

Regarding locality and time of capture,
it was suggested that care should be taken not to
rely too heavily on latitudinal distance from the
Equator as a determining factor in species iden-
tification, because surface water temperature
in the western Pacific is high even in high lati-
tudes during summer and fall, so that, if spawn-
ing or larval survival were dependent upon
temperature in any way, then latitudinal desig-
nation might become meaningless.

The second paper had for identifying the
various species a different approach. Identifi-
cation was based on locality and time of capture
and the number of spawning species present, as
represented in longline catches for similar
months. Pigmentation on the dorsal and ventral
edges of the trunk and the position of the second
dorsal fin insertion, in the case of two species
(T. orientalis and T. tonggol) , also were used.

Results of X-ray technique failed, of
course, to corroborate either view regarding
the presence or absence of pigment spots on the
trunk. Since a large percentage of specimens
had no pigment spots and about 25 percent had
either one spot on the dorsal edge, or one spot
on the ventral edge, or one spot each on both
dorsal and ventral edges of the trunk, it was
felt that, although pigmentation is useful in iden-
tifying larvae, there may be enough variation so
that other characters should also be used.

The possibility of loss of pigment spots
from exposure to ultraviolet rays or from the
preservatives was mentioned, and care in han-
dling and storage of samples was stressed.

One character which might be useful for
larval tuna identification and, therefore, worthy
of study was the position of the eye relative to
the horizontal axis through the tip of the snout.

Identification of Juveniles

Ocean. Unfortunately, all the larvae died soon
after hatching. The failure to keep the larvae
alive was attributed to inadequate preparation,
as the opportunity to do this work was entirely
unexpected. Because such opportunities appear
unpredictably, it was suggested that adequate
preparations to do this type of work be made on
all future cruises. In order to ensure greater
success in keeping the larvae alive after hatch-
ing, it was suggested that antibiotics be added
to the water to keep bacterial counts at a low
level.

Results of preliminary trials with soft
X-rays indicate that this technique is a promis-
ing tool for identifying juveniles and adults of
certain tunas, particularly the smaller species
such as T. atlanticus. For the yellowfin, big -
eye, albacore, and bluefin, species determina-
tion was made by the position of the first ventrally
directed parapophysis . The position of the first
parapophysis in the juveniles, however, agreed
with that of the adults only in the bluefin. In
yellowfin this structure was on the seventh ver-
tebra in the juvenile and on the ninth vertebra in
the adult, as illustrated by Godsil and Byers
(1944)1/ and Kishinouye (192 3) .U In albacore it
was on the 9th vertebra in the juvenile and on
the 10th in the adult (Godsil; Kishinouye). Since
the total vertebral count of both species shown
by the X-rays was identical with counts obtained
from Kishinouye and Godsil, it was suggested
that perhaps the difference in the position of the
first parapophysis in these two species could be
due to growth. It was therefore suggested that
a wider range of sizes be X-rayed for each of
these species .

Realizing that identifications obtained
with the X-ray method would not be helpful to
other larval tuna researchers unless they were
interpreted in terms of external appearance of
the fish, it was recommended that descriptions
of external appearnace be supplied with X-ray
data.

In view of the preliminary status of lar-
val and juvenile studies and the fact that the re-
sults obtained are only tentative, it was agreed
that it was premature to arrive at any conclu-
sions concerning the positive identity of all the
species. It was therefore recommended that the
various investigators continue with their work
until more definite results are obtained.

Hiroshi Nakamura presented figures and
results of embryonic development of thebigeye,
which personnel of the Nankai Laboratory had
fertilized artificially aboard ship in the Indian

Methods and Gear

While it was agreed that standardization
of gear was desirable, there were contrasting
opinions as to whether this should be done at
the present time. Some felt that for the present
the collecting of larvae in large numbers was
still important and should be continued until
positive species identifications were attained.

Gear modifications were suggested for
sampling larvae. It was reported that attach-
ment of a light to the 6-foot Isaacs -Kidd trawl
and towing the net at slow speeds resulted in
large catches of forage organisms. It was also
reported that a plankton net attached to the float
line of the last basket of longline gear resulted
in large catches of larval fish. Finally,
Nakamura suggested a possible method of col-
lecting larvae and keeping them alive by attach-
ing a piece of bamboo, which was open at one
end and slit along the sides, to the cod-end of a
plankton net, with the entire cod-end enclosed
with netting. The larvae are less likely to be
injured when taken in this device.

Recognizing that more effective gear for
collecting juveniles is necessary, the Working
Group recommends increased effort toward this
end.

— Godsil, H. C. and R. D. Byers. 1944.
A systematic study of the Pacific tunas . Califor-
nia Dept. of Fish and Game, Fish Bulletin No.
60, 131 p.

Al

Kishinouye, Kamakichi. 1923. Contri-
butions to the comparative study of the s o -called
scombroid fishes. Journal of the College of
Agriculture, Tokyo Imperial University, Vol. 8,
No. 3, p. 293-475.

17

RESOLUTIONS

1. The Conference recognizes that there
are problems in the taxonomy and nomenclature
of the tunas and their allies (i. e . , family Scorn -
bridae of Fraser-Brunner) . The Conference
recommends that a review of the family be made
on the basis of existing knowledge and submitted
to the FAO World Tuna Conference to be held in
July 1962. Such a review would serve to identify
areas of common agreement and areas requiring
further study and material. The Conference
requests that R. Gibbs, Jr. and B. Collette
undertake such a preliminary review.

Realizing that additional specimens of
certain kinds and from certain areas will be
needed inany case, the Conference recommends
that such collections be instituted as soon as
possible (the details of kinds and areas to be
specified by Gibbs and Collette). The Confer-
ence requests the Bureau of Commercial Fish-
eries Ichthyological Laboratory to explore
sources of funds for the collection, shipment,
and storage of specimens and other associated
costs, including study of the material.

The Conference a c knowl e d g e s with
thanks and directs the attention of the Ichthy-
ological Laboratory to the generous offer of
H. Nakamura, Director, Nankai Regional Fish-
eries Research Laboratory, to provide speci-
mens from the worldwide Japanese tuna fishery.

Results of the X-ray method and other
internal characteristics would be most helpful to
other workers if the species so identified are
also described in terms of external characters.
The Conference recommends that this be done.

Recognizing the difficulty in capturing
the early juvenile stages , the Conference recom-
mends that concerted effort be expended in night-
light collecting by all research vessels on a
worldwide basis.

4. The Conference recognizes that there
remain many problems of population identifica-
tion and migration and urges all research groups
studying tunas to attack these problems through
tagging experiments, studies of blood groups, or
other appropriate methods. Examples of such
studies, but by no means a complete list, include:

A. Tagging small southern bluefin
off the south coast of Australia to determine if
recoveries are made in the "Old" and "New"
fishing grounds to the northwest and west of
Australia.

B. Tagging small albacore (lessthan
50 cm., especially the 35-cm. modal group) off
Japan, or wherever they may be found, to deter-
mine their subsequent movements into the com-
mercial fisheries of the North Pacific.

2. The Conference recommends that
there be established a World Center to promote
the exchange of tuna erythrocytes and reagents.
The Conference notes that the Bureau of Com-
mercial Fisheries Biological Laboratory at
Honolulu volunteers to act in this capacity and
requests that it do so.

Further, there is a need to standardize
the terminology now in use for tuna blood groups.
There is especial need to determine if identical
blood groups have been independently discovered
and given different names. The Conference
recommends that the World Center perform this
function and suggests that the consensus of work-
ers in this field be determined regarding stand-
ard rules of nomenclature.

3. Realizing that identification of tuna
larvae is in such an early stage of investigation
and that the results are no more than tentative,
the Conference recommends that both the Japa-
nese and American researchers continue with
their present work until a more definite basis
for establishing correct identification of species
is attained.

C. Tagging small -medium albacore
off the west coast of South America to determine
if they are subsequently recovered in the long-
line fishery of the tropical South Pacific.

5. The Conference notes the recent ad-
vances in the problems of determining the age of
albacore and recommends that those studying
this problem work together in resolving uncer-
tainties about the absolute ages to be associated
with particular sizes.

6. The Conference points out the sub-
stantial advances made in identifying year
classes in the North Pacific albacore fisheries
and the desirability of studying the individual
year-class strength and the individual year-class
contribution to the entire fishery with a view to
establishing a basis for the study of factors af-
fecting year-class contribution to the entire
North Pacific albacore fishery.

7. The Conference recognizes that
common attention to taxonomic problems by
immunogeneticists, biochemists , and classical
taxonomists would be fruitful and requests

A. Suzuki, R. Gibbs, Jr., G. Ridgway, and
L,. Sprague (Chairman) to identify problems in
tuna taxonomy which could most profitably be so
examined, to proceed with such examination in-
sofar as possible, and to report their findings
to the FAO World Tuna Conference.

8. The Conference recognizes the need
for identification of tuna subpopulations, urges
those studying blood groups to improve methods
for transporting and storing blood samples, and
suggests that the wide-ranging tuna fleets of the
world be used to collect blood samples.

9 . The Conference recognizes the impor-
tance of genetic identification of subpopulations
and urges that additional emphasis be placed on
the problem of how much mixing musttake place
between subpopulations before they are no longer
"independent. "

10. Studies which bring together research
workers engaged in biological and oceanographic
studies on the tunas and the seas inhabited by
them should be encouraged by international co-
operation. Such studies should include, for
example, research on the interaction between
sea and atmosphere, oceanic fronts, water
masses, current systems, changing oceanic
climates, year-class sizes, and interaction be-
tween fish and environment.

tuna resource and the potential sustained yield
of tuna.

12. The Conference agrees that abstracts
of submitted papers, summaries of discussion
sections, copies of resolutions, and a list of
participants should be published, if possible, in
the Special Scientific Report--Fisheries series
of the Bureau of Commercial Fisheries and di-
rects the Chairman to make arrangements for
such publication.

Further, the Conference requests the
Bureau of Commercial Fisheries Biological
Laboratory at Honolulu to supply copies of the
submitted papers upon request.

13. The Conference recognizes the ad-
vantages, especially in promoting the exchange
of information and in stimulating the rate of prog-
ress in fishery studies , of contact between scien-
tists from different laboratories and suggests
that, in addition to scientific conferences, ex-
change of scientists between laboratories be
facilitated.

14. The Conference recognizes the de-
sirability of a report from this Conference to the
FAO World Tuna Conference and directs the
Chairman to furnish FAO with copies of all con-
tributions, summary reports of discussions,
resolutions, and a list of participants.

11. In view of the ever-increasing world
need for protein and of the rapidly expanding tuna
fisheries of the world, attention should be di-
rected to estimates of the magnitude of the world

15. The Conference appreciates the meet-
ing facilities made available by the University of
Hawaii and directs the Chairman to prepare a
letter of thanks to the University.

ABSTRACTS OF PAPERS

Alverson, Dayton L.

Ocean temperatures and their relation-
ship to albacore tuna (Thunnus germo )
distribution in waters off the coast of
the States of Oregon and Washington,
and the Province of British Columbia.
/Conference Paper V - Z.J (See also
Alverson , Dayton L. 1961. Ocean
temperatures and their relationship to
albacore tuna (Thunnus germo) distri-
bution in waters off the coast of Ore-
gon, Washington, and British Colum-
bia. Journal of the Fisheries Research
Board of Canada, vol. 18, no. 6,
p. 1145-1152. )

Commercial albacore fishing offshore
from Pacific Northwest States and the Province
of British Columbia occurs during summer
months when offshore surface water tempera-
tures exceed 58° F. Fishermen have established
58° F. surface temperature as an indicator of
"tuna water," and this rule -of -thumb relationship
for surface water temperatures and albacore has
generally been substantiated by past qualitative
observations made during albacore investiga-
tions. Catch-per-hour data are also in accord
with this general relationship. However, catch-
per-unit-effort data do not indicate as marked a
decline in availability at temperatures between
54° and 58° F. as might be interpreted from qual-
itative observations. With the exception of one
albacore caught by gill net in 1956, all albacore
have been taken in Bureau of Commercial Fish-
eries investigations where surface temperatures
exceeded 54° F. , and the highest catch rates
have been obtained between 58° and 61° F. As
the thermocline depth averages about 60 feet in
the summer months offshore from the Pacific
Northwest States and temperatures fall well be-
low 50° F. at the bottom of the thermocline,
albacore probably inhabit o n 1 y the overlying
(mixed layer) lens of warm oceanic water. Con-
centrations of albacore appear to occur along
the interface of the warm oceanic waters and the
cooler waters adjacent to the coast.

Austin, Thomas S. , and Richard A. Barkley

Use of oceanographic monitoring stations
in fishery research. /Conference
Paper V - 97

With the support of data from monitoring
stations established by the Bureau of Commer-
cial Fisheries Biological Laboratory, Honolulu,

a plea is made for the establishment of simi-
lar monitoring station programs by other
laboratories.

Oceanographic studies in support of fish-
eries investigations should normally begin with
investigations of local midwinter and midsummer
conditions, which establish extreme conditions
at times of minimal rates of temporal change.
These studies should be followed by similar
broad-scale surveys, preferably synoptic, dur-
ing periods of transition. Later, the results of
these surveys lead to research on particular
features of the ocean thought to be ecologically
significant. At this point oceanographic studies
should progress from the stage of exploratory
surveys to the stage of research into mechanisms
and rates of change in the ocean, and conven-
tional surveys per se cease to be economical or
practical means for gathering data. Logically,
it is at this stage that monitoring stations be -
come most useful, in that they provide time-
series data at a series of points in space, making
it possible to determine rates and study proc-
esses. The final choice of sampling locations
for monitoring purposes will be determined by the
results of surveys, but it is a worthwhile risk
to establish monitoring stations in likely loca-
tions at the same time oceanographic surveys
themselves are begun, knowing that some sta -
tions may have to be relocated or discontinued
as knowledge accumulates, but that some will
provide data of interest for periods between
surveys and perhaps for indefinite periods
thereafter.

Examples of the value of data from moni-
toring stations are given. A station established
at Koko Head, on Oahu, Hawaii, has been in
operation for over 7 years. Data from this sta-
tion are now used to predict the year-to-year
changes in the catch of the Hawaiian skipjack
fishery, a prediction which has been successful
for the past 4 years and has been applied to
accurately hindcast the catches for 7 previous
consecutive years. A station at Christmas Is-
land was established in 1954, in time to detect
precisely the time at which unusual cooling of
the surface waters occurred, during 1955, and
the details of a subsequent warming trend which
reached a maximum in the early winter of 1957.
More recently, a networkof monitoring stations,
including eight island stations and two weather
ships, has yielded evidence of coherent changes
in surface salinity over distances of many thou-
sands of miles in the central North Pacific
Ocean.

Bell, Robert R.

The age composition of the California
Pacific albacore catch. /Conference
Paper VII -127 (See also Bell, Robert R.
196Z. Age determination of the Pacific
albacore of the California coast. Calif .
Fish and Game, vol. 48, no. 1, p. 39-
48.)

Recent development of the scale method
for aging albacore by marine scientists of the
California State Fisheries Laboratory on Ter-
minal Island has made it possible to determine
the age composition of the catch and measure
year-class strength and fluctuations within-
creased precision.

This paper reports on their preliminary
effort to determine the age composition of the
California commercial albacore catch.

The age composition of the California
albacore catch for the last 3 months of the 1959
season was determined by sampling the catch
and aging the fish by the scale method. Scales
were selected from the area of the fifth dorsal
finlet. The checks found on these were believed
to be annual innatuie largely because of the good
correlation between them and the length fre-
quency modes found in the commercial catch.

The smallest fish entering the California
catch (mean length for 1959 of 573 mm. ) had one
check and therefore were hypothesized to be fish
in their second year of life, most likely 16 to 18
months old. This hypothesis was also based on
the absence of a smaller mode either in the catch
or in survey collections.

The majority of the fish appearing in the
second mode, the most important in the Califor-
nia fishery, had two checks on their scales.
These fish, believed to be in their third year of
life, had a mean length of 657 mm.

The sample produced a class with a mean
length of 774 mm. for fish believed to be in the
fourth year of life, and two other age groups,
those in the fifth and sixth year of life having
mean lengths of 837 and 878 mm. , respectively.

The California tagging studies have since
verified assumptions that the length frequency
modes are 1 year apart in age. Tagging studies
have also verified the growth determined by the
scale aging method.

The California commercial albacore
catch in the last 3 months of the 1959 season
(September-November) amounted to 13, 978, 766

pounds. The catch in numbers was computed to
be 934,297 fish. Fish of age group II were found
to comprise 58 percent of the catch. Fifty-five
percent of the catch was supported by fishfrom
63 to 68 cm. in fork length. This is the second
mode in the commercial catch and composed of
86 percent age group II fish, 11 percent age group
I fish, and 3 percent age group III fish.

Blackburn, Maurice

Distribution and abundance of Eastern
Tropical Pacific tunas in relation to
ocean properties and features. //Con-
ference Paper V - \J

The coastal waters from southern Cali-
fornia to northern Chile were divided into 16
areas, 5 of which included offshore islands or
island groups. In explaining the generally high
abundance of skipjack and yellowfin in this re-
gion of complex oceanographic conditions, the
following generalizations about the region are
made:

1. Temperatures in surface waters are
generally > 21° C. (70° F. ) in the fishing
seasons.

2. Winds result in upwelling and enrich-
ment in certain areas and a shoaling of the ther-
mocline in the region as a whole.

3. Winds over very shoal thermo-
clines result in localized vertical mixing and
enrichment.

4. Seasonal changes are minimal; thus
favorable conditions for tuna aggregations may
persist for several months.

The 16 areas may be grouped loosely in
three general categories:

(1) The extremes of the region: areas
north of 22° N. and south of 5°S. Seasonal var-
iations in distribution of yellowfin and skipjack
tuna are rather pronounced and correspond to
the seasonal march of surface isotherms, par-
ticularly 21° C. in the northern areas. During
years in which the warm waters are found in
more northerly and southerly latitudes , tuna are
also found in more northerly and southerly areas.
Some areas are biologically productive because
of upwelling.

(2) The center of t h e region: coastal
areas from southern Mexico to Ecuador (22° N.
to 5° S. ). Surface temperatures are almost al-
ways > 21° C. Thermoclines are shoal in most
areas. Tuna (yellowfin and/or skipjack) occur
in most areas at most seasons. Skipjack may
be excluded from areas of surface temperatures
above 28° C. (83° F. ). Seasonal variations in
tuna abundance and ocean properties are smaller

than in (1). Results from the area most exten-
sively studied (Gulf of Tehuantepec), if extra-
polated to the other areas, suggest association
between depth ofthermocline, biological
productivity of the surface waters, and tuna
abundance. In areas of shoal thermoclines,
destratificationby the winds leads to enrichment
of the surface waters.

(3) Offshore islands. Tuna, yellowfin
and/or skipjack, occur at each island or island
group in greater abundance than in the imme-
diately adjacent ocean waters. It is not clear
why they do so, but little oceanogr aphic work
has been done except at Clarion Island. Sea -
sonal variations in tuna abundance are compa-
rable with those in (2).

Brown, Robert P. , and Kenneth Sherman

Oceanographic observations and skip-
jack distribution in the North Central
Pacific. /Conference Paper V - \lj

Recent investigations by the staff of the
Bureau of Commercial Fisheries Biological
Laboratory, Honolulu, have indicated that sea-
sonal fluctuations in availability of the com-
mercially important skipjack tuna, Katsuwonus
pelamis (Linnaeus), in Hawaiian waters are
related to seasonal movements of surface water
types within the Hawaiian region. Five cruises
were undertaken from January to October 1959
by the staff of the Laboratory within the general
area of the North Pacific bounded by latitude
15° N. and 26° N. , and longitude 150° W. and
170" W. , with two primary objectives: (1) To
delineate, by surface temperature and salinity
values, the boundaries between the North Pacific
Central, intermediate, and North Pacific Equa-
torial water types, and (2) to monitor the sea-
sonal movements of these water types and their
associated biota, particularly skipjack tuna.

Background material and sources of in-
formation concerning oceanographic conditions
in the Hawaiian Islands region are given. The
results of the five 1959 cruises were discussed,
and it was shown that a reliable description of
the seasonal movements of the surface water
types within the survey region could be obtained
by monitoring the surface salinity of these
waters. Tonguelike features noted in the sur-
face salinity distribution were discussed, and
possible causal mechanisms were discussed.
Salinity gradients associated with the boundary
zones between the water types were found to
move seasonally with the water types and to
undergo a widening as the year progressed. The
possible cause for this was discussed.

Available scouting data indicated that
skipjack sightings during January-February and
March- April prior to the summer appearance of
large fish, which comprise the bulk of seasonal
skipjack landings, were concentrated in the
boundary between the intermediate and adjacent
water types. However, additional observations
of skipjack distribution and boundary conditions
are needed before any definite conclusions re-
garding a relationship can be reached.

The greater frequency of occurrence of
skipjack schools west of longitude 155° W. sug-
gested movement of summer "season" skipjack
to the island region from the west.

Survey results showed no evident rela-
tion between water type and seasonal distribu-
tion of zooplankton. It was suggested, however,
that a relation may exist between the observed
increase in zooplankton abundance and skipjack
larvae during the summer months attributable
to a spawning periodicity of adult skipjack.

Distribution of large predators caught
during longline and trolling operations and
aquatic mammal sightings did not appear re-
lated to water types. Bird flocks were usually
associated with fish schools.

Clemens, Harold B.

The distribution of California bluefin tuna
in the eastern North Pacific. /Con-
ference Paper I - \]

California bluefin are caught by purse
seine from Cape San Lucas to Pt. Conception
primarily from May to November. The species
is taken mainly in coastal waters and favors
water with temperature -salinity characteristics
intermediate between the cold low-saline water
in which albacore occur and the warm high-
saline water in which yellowfin occur. In warm
years, the bluefin ranges considerably farther
north than normal. There has been a marked
change in size of the fish landed during the past
50 years, and there also are large annual fluc-
tuations in the catch.

Clemens, Harold B.

The distribution of albacore in the North
Pacific, /Conference Paper 1-57

Pacific albacore are creatures of the
open sea. They are most abundant in the tem-
perate regions, where they make far-ranging
seasonal migrations.

The most productive fishing grounds in
the eastern North Pacific are located between
central Baja California and the Columbia River.

During the last decade, heaviest catches have
been made south of Oregon within the 5-month
period June to October and predominate in small
(< 40 pounds), immature fish.

Sea temperatures greatly influence the
distribution of albacore on t h e eastern North
Pacific fishing grounds. This influence is char-
acterized by seasonal shifts of the entry route
into the grounds, and subsequent variation in the
patterns of northward movement within the
grounds as the season progresses.

Size distribution also is related to sea
temperatures. Small fish abound in tempera-
tures of 60 to 65° F. , while larger fish are
caught where surface temperatures range from
66 to 70° F.

Small (13 to 20 pounds) albacore are the
largest contributors to the eastern Pacific catch
while medium to large fish (>20 pounds) are
most abundant in the Japanese fisheries. Tre-
mendous numbers of youngster s (>10 pounds) re-
main undiscovered in the mid-Pacific.

Clemens, Harold B.

Migration, age and growth, and spawn-
ing studies of the North Pacific alba-
core (Thunnus germo). /^Conference
Paper II - 2] (See also Clemens,
Harold B. 1961. The migration, age,
and growth of I-acific albacore (Thunnus
germo), 1951-1958. Calif. Dept. of
Fish and Game, Fish Bulletin no. 115,
128 p.

This paper presents a brief summary of
part of the progress made from 1951 to 1958 by
California Department of Fish and Game marine
biologists in their study of North Pacific alba-
core stocks. Investigations were primarily on
albacore interchange between the major North
Pacific fishing grounds and changes in fish size,
accomplished by making oceanographic and ex-
ploratory fishing cruises, studying fishing fleet
activities, tagging albacore, and subsequently
recovering marked fish from which migratory
patterns and growth rates could be interpreted.

Data from exploratory cruises and fish-
ermen's logbooks showed that sea-surface
temperature is one of the important factors that
influence albacore movements and distribution.
The route used by albacore entering the West
Coast fishing grounds each season was transient
in nature, and its position was regulated prima-
rily by sea-surface temperatures between
58° and 68° F. After entering the southern
California-Baja California fishing grounds, the
albacore swing northward upcoast. The route
taken in this northward movement also is
transient.

During 15 cruises, 4,585 albacore were
tagged and released in the major fishing areas
south of San Francisco. There were 73 recover-
ies, representing 1.6 percent of the total released.
About 80 percent of the tags were recovered with-
in the first calendar year of release. Omitting
those, 7 percent of the remainder were recovered
in the central Pacific, 21 percent off Japan, 62
percent in the West Coast fishery the second
season, and lOpercent in the West Coast fishery
the third season.

The tagging data confirmed a northward
coastal migration as the season progresses.
Ninety-five percent of the marked albacore re-
captured during their first season at liberty had
moved northward from the release point, at an
average rate of 6 nautical miles per day (24
hours). Summarizing the data by distance. from
shore revealedthat albacore traveling within 100
miles of the coast averaged about 4 nautical
miles daily, while offshore migrants swam al-
most 4 times faster.

A hypothesis on the migratory pattern of
albacore was presented. The hypothesis is that
albacore from the American fishery (mostly
small fish under 20 pounds) cross the ocean in
late fall and early winter to enter the area of the
Japanese longline fishery, and intermingle with
medium-sized fish (20 to 40 pounds) that had
moved into the area during the late summer and
fall from the Japanese coastal fishery, and with
fish of all sizes that had remained in the central
Pacific. These fish then move south as the win -
ter season progresses. In the spring, the large
fish (over 40 pounds) continue south into the
North Equatorial Current and Equatorial Coun-
tercurrent areas, while the small- and medium-
sized fish reverse their course and begin moving
north. At this time, some of the fish (medium-
sized) travel up the Japanese coast, and some
(all sizes) may remain in midocean and travel
north and south seasonally. Others (small fish),
however, return from the mid-Pacific winter
grounds , enter the American fishing grounds,
and again travel up the coast and back across the
Pacific.

Albacore growth was estimated fromtag
recovery data. Data from 21 tagged albacore
that had been at liberty from 9 to 15 months were
used to calculate an annual growth curve. The
line of best fit for these data is described by the
equation Y = 210. 31 + 0. 845 X, and the asymp -
totic length attainedby the species is calculated
at 135. 6 cm. The results showed that albacore
averaging 52 cm. in June (start of the California
albacore season) grow to 65 cm. in 1 year, to
76 cm. in 2 years, to 85 cm. in 3 years, to93
cm. in 4 years, and to 100 cm. in 5 years. It

23

was postulated that the 52-cm. size group would
consist of 1-year-old fish (14 months), the 65 cm.
size group 2-year-old fish, etc.

Regarding spawning of the albacore, it
appears that first maturity may be reached by
some of the larger fish in the 85 -cm. size group
(4-year-olds), since examination of fish caught
near Guadalupe Island during July and August
1953 revealed that those in the 93- and 100-cm.
size groups had recently spawned. Apparently
these large albacore had spawned prior to their
coastward migration from the mid-Pacific,
which i s in progress primarily from June to
September for large fish and from May to August
for smaller ones. This means that albacore
spawning may occur in the west-central Pacific
during the period preceding an annual coastward
migration, for it seems unlikely that they would
spawn en route. Based on the reported capture
of small albacore, 23 cm. long, about 500 miles
west of Midway Island from January to May 1937,
139 albacore from 30 to 37 cm. long in the Japa-
nese coastal fishery in June 1951, and young
albacore 18.8 and 12.4 cm. long caught in May
1949 and June 1952, it is believed that spawning
probably takes place during the winter or spring.
Most of the albacore comprising the California
fishery originate between the longitude of Japan
and the Hawaiian Islands (probably nearer the
Islands) and migrate into the West Coast fishing
grounds during the first season they become
strong enough to school and endure along mi-
gration.

Collette, Bruce B.

A preliminary review of the tunas of the
Genus Thunnus. /Conference Paper
VI - 17

This is a first step in a proposed revi-
sion of the large tunas of the world. The arti -
ficiality of splitting the Scombridae into the
families Thunnidae, Cybiidae, and Katsuwonidae
and placing the Thunnidae and Katsuwonidae in a
separate order, the Plecostei, has been shown
by a number of workers. The differences be-
tween Thunnus South, Parathunnus and Neo -
thunnus Kishinouye , Germo Jordan, and
Kishinoella Jordan and Hubbs are specific, not
generic. The species of Thunnus have been
greatly split as a result of using even smaller
differences as specific differences, since spe-
cific differences were used to separate genera.

Although further and more detailed study
is necessary, present evidence indicates that
there are only six species of great tunas in the
world: albacore (T. alalunga), yellowfin (T.
albacares), blackfin (T. atlanticus), bigeye (T.
obesus), bluefin (T. thynnus), and longtail (T.
tonggol).

Synonymies are presented a s tentative
allocations of the many names that have been
applied to the tunas, both generic and specific.
The generic names Thynnus Cuvier, Orcynus
Cuvier, Orcynus Cooper, Albacora Jordan,
Germo Jordan, Parathunnus Kishinouye, Neo-
thunnus Kishinouye, Kishinoella Jordan and
Hubbs, and Semathunnus Fowler are placed as
synonyms of Thunnus Suuth. The six species
are designated as above with the recognition of
two subspecies of bluefins, T. thynnus thynnus
from the Atlantic and T. thynnus orientalis from
the Pacific, on the basis of gill raker counts.

Fujii, Yutaka; Koichi Mimoto, and
Shichiro Higasa

Biochemical studies on the races of tuna.
Base composition of testi s deoxy-
ribonucleic acid (DNA). /Conference
Paper III - 3.7 (See also Fujii, Yutaka
et al. Biochemical studies on the races
of tuna. Report of Nankai Regional
Fisheries Research Laboratory no. 9,
p. 136-142 (1958); no. 11, p. 1-6 (1959);
no. 12, p. 14-22, 23-32 (I960).)

Studies of the relative proportion of the
bases adenine (a), thymine (t), guanine (g) ,
cytosine (c), extracted from tuna testis deoxy-
ribonucleic acid have shown that characteristic
values of the ratio of (a+t) / (g+c) may be ob-
tained for bigeye, yellowfin, Indo-maguro, and
Goshu-maguro tunas.

A study to relate these values to sub -
populations within each species is being carried
out. There is some evidence that the ratio of
bases in the testis DNA is different for the same
species collected from different areas.

Hiyama, Yoshio, and Kenji Kurogane

Morphometrical comparisons of tuna
from areas in the Pacific and I n d i a n
Oceans. /Conference Paper III -77

Morphometric and meristic studies
were made of albacore, yellowfin, and bigeye
tunas. Five hundred ninety-six albacore were
examined, including 288 from the northwest

24

Pacific, 141 from the equatorial Pacific between
160° W. and 150° E. , 42 from east of Australia ,
and 125 from the Indian Ocean. Meristic charac -
teristics showed no differences. Differences in
morphometric characteristics lead to the con-
clusion that there exist distinct populations in
the North Pacific, the southwest Pacific , and the
Indian Ocean, although there exists the possi-
bility of some mixing between the latter two
areas.

One thousand fifty-seven yellowfin tuna
were examined, including 353 from the north-
west Pacific, 375 from the equatorial Pacific,
94 from the Coral Sea, 60 from the Banda Sea,
and 175 from the Indian Ocean. Similarities and
differences in morphometric characteristics
lead to the conclusion that there are a number of
independent or semi-independent populations
within each major area, somewhat restricted in
distribution, and probably intermingling with
adjacent groups.

Six hundred ninety-seven bigeye tuna
were examined, including 313 from the north-
west Pacific, 284 from the equatorial Pacific
between 130° W. and 120° E. , and 100 from the
Indian Ocean. Although some differences were
observed, no definite conclusions were drawn
owing to conflicting biological information and
the need for more data. It is probable that big-
eye population structure is intermediate between
that of albacore and yellowfin.

Inoue, Motoo

Relation of sea condition and ecology of
albacore in the northwest Pacific
Ocean. /Conference Paper V - i.J

(See also Inoue, Motoo. Studies on
movements of albacore fishing grounds
in the Northwest Pacific Ocean-I, II,
III. Bulletin of the Japanese Society
of Scientific Fisheries, vol. 23, no. 11,
p. 673-679 (19 5 8); vol. 25, no. 6,
p. 424-430 (1959); vol. 26, no. 12,
p. 1152-1161 (I960).)

It has been hypothesized that a 1 b a c ore
available to the Japanese winter longline fishery
make a vertical migration in the spring and be-
come available to the Japanese s u m m e r pole-
and-line fishery. Horizontal distribution of
temperatures of the surface waters during the
winter appears to affect the migration of alba-
core from the longline fishery into the pole -and -
line fishery. The variations and persistence of
warm and cool water, winter to summer, are
primary criteria for predicting the location and
abundance of albacore available to the summer
fishery.

To facilitate the prediction for the sum-
mer fishery, the patterns of temperature dis-
tribution for the periods January- June, 1951-58,
were classified into three types. In the first,
cool waters are found inshore, winter to summer.
The warm Kuroshio waters do not reach the main-
land. In the second, warm Kuroshio waters are
inshore with the cooler waters offshore during
the January-June period. In the third classifi-
cation, cool waters are inshore from January
to April or May and are then replaced by
warmer waters.

In the first category, winter albacore are
found east or south of the inshore cold water. As
the spring and summer fishery begins, these fish,
which tend to migrate northward , are barred
from doing so by the cold water, and so move
rapidly eastward through the 18°-20° C. water.
These fish remain available to the pole-and-line
fleet during April and May and then move out of
the area of the fishery.

In the second category (cold inshore water
lacking), winter albacore are found inmore west-
erly and northerly areas than in the first category.
Although the start of the summer season may be
delayed, good fishing may continue well into late
summer in areas close to land.

In the third category (cold inshore water
is present until April, then d i s a p p e a r s ), the
winter fishery develops to the south and east,
although not to the extent observed in the first
category. Albacore remain west of longitude
140° E. until May, and the pole-and-line fishery
develops during May and June, relatively close
to land.

Thus the knowledge of winter conditions
and the degree of persistence of these conditions
through the spring period provides a means for
determining the potential location and success
of the summer pole-and-line fishery.

The location of the principal summer
fishing grounds, whether westerly and inshore
or easterly and offshore, results not only from
the oceanographic conditions in the area of the
summer fishery but also from the fluctuations
of oceanographic conditions of the previous win-
ter and the associated variations in the migration
of the albacore. The terms "environmental
resistance" and "environmental induction" were
proposed. Waters with temperatures below
16.3° C. impede or deflect the migration of alba-
core and thus are in the category of an environ -
mental resistance; those between 16° and 22 " C ,
delimit the areas of migration and are termed
environmental inductance. Using 10-day sur -
face temperature charts for the period December

25

through May, it was possible to delimit areas
of environmental resistance and induction.
These areas were then considered for various
years along with the records for winter and
summer albacore catch records. The area was
then classified by two basic patterns. In the
first, the warmer waters are inshore; in the
second, the cooler waters are inshore.

From the data presented, it is concluded
that if the winter fish are concentrated in two
or three pools from which they move southerly
to form a single congregation during the sum -
mer close to Japan, good catches of summer
albacore may be expected. Concentrations of
winter albacore in the eastern portion of the
area, or lack of definite concentrations, result
in a poor summer catch of albacore.

volumes were highest to the east. There was
little seasonal difference in food volumes. Reef-
associated organisms appeared most frequently
in the diet of albacore caught near land.

Troll-caught albacore in the North Pacific
fed, prior to capture, throughout the day, but
evidence for distinct feeding periods was not
clear. Evidence is presented that albacore also
feed at night. The higher stomach content vol-
umes of troll-caught albacore occurred in waters
of mid-clarity. Some competition for food may
exist among albacore, yellowfin, andbigeye tuna
in the equatorial Pacific.

Checklists of the organisms identified in
stomach contents show the number of such organ -
isms, their frequency of occurrence, and aggre-
gate total volume.

Iversen, Robert T. B.

Food of albacore tuna, Thunnus germo
(Lacepede), in the central and north-
eastern Pacific. ^Conference Paper
VII - 107

The stomach contents of 544 albacore
tuna, Thunnus germo (Lacepede), captured in
the central and eastern North Pacific during the
years 1950-57 were analyzed to: (1) identify the
organisms eaten; (2) determine if the abundance
and distribution of albacore is related to the
abundance and distribution of their food; and (3)
relate feeding to size, method of capture, geo-
graphic location, season, distance from land,
time of day, and water clarity. The albacore
were captured by longline, gill net, and troll.

Stomachs of the larger albacore contained
more food than smaller albacore, but the larger
albacore contained less per pound of body weight .
Stomach contents consisted mainly of a variety
of fish, squid, and crustaceans, the percent vol-
ume of each differing according to the method of
capture.

Johnson, James H.

Sea temperatures and the availability of
albacore (Thunnus germo) off the
coasts of Oregon and Washington.
/Conference Paper V - bj

Wide variations exist in landings of alba -
core in Oregon and Washington. In 1944, Oregon
and Washington landings reached 34 million
pounds but dropped to 0. 6 million pounds a decade
later. Variations in landings may be a result
of fluctuations in availability. Investigators
have shown that distribution of albacore along the
North American coast is influenced by sea tem-
peratures. Although weather conditions and
economic factors are reflected inOregon-
Washington landing statistics, it inay be that
annual variations in sea temperatures are affect-
ing the success of the fishery by varying avail-
ability to the fishermen.

The latitudinal abundance of albacore in
the equatorial Pacific, determined from catch
statistics, was not related to the amount of food
eaten by albacore captured in this area. During
the summer in the temperate North Pacific, fish
with high volumes of stomach contents were
found south of successive peak volumes of organ-
isms captured by midwater trawls and zooplank-
ton nets. This suggests successive trophic levels
associated with an advancing oceanographic and
biological "frontier" in the Transition Zone. In
the equatorial Pacific, fish with highest volumes
of stomach contents were found to the west, while
in the temperate North Pacific , stomach content

Relations between sea surface tempera-
tures and landings were investigated for the
years 1947-60. In years of above normal tem-
peratures, landings were, in general, signifi-
cantly greater than in years of below normal
temperatures. Whereas warm water did not
insure a good fishery, widespread cold water
was detrimental to the success of the fishery.
The data suggest that in June, if the sea temper -
ature anomaly is large enough, it is possible to
predict whether or not sea temperatures will be
favorable for albacore at normal time of com-
mencement of the fishery in mid-July.

Kamimura, Tadao, and Misao Honma

Distribution of yellowfin in the longline
fishing ground in the Pacific Ocean,
especially on the regional variation
of t h e density in each size group.
^Conference Paper I - Z]

Yellowfin catch data for the years 1954-
59 were classified by area, season, and fish
size category. In general, fish smaller than
120 cm. were located in east longitudes, whereas
those larger than 140 cm. were in west longitudes.
Artificial causes of this pattern (effect of fishing,
gear selectivity, and land mass effect) were dis-
counted, and the distribution instead hypothe-
sized as caused by a west-to-east migration of
fish.

Kikawa, Shoji

Studies on the spawning activity of the
Pacific tunas Parathunnus mebachi and
Neothunnus macropterus by the gonad
index examination. /Conference Paper
VII - 87

This paper gives a general review of the
spawning of bigeye and yellowfin in the Pacific
Ocean. The "gonad index" is used to represent
degree of sexual maturity, and is defined as
follows:

G.I. = W /L3 X 104, where W is the
o o ->

weight of a pair of ovaries in grams, and L. is

the cube of the fork length of the fish in cm.
Frequency distributions of gonad indices were
used to evaluate group maturity of fish indiffer-
ent areas.

The frequency distribution of bigeye gon-
ad indices in a spawning area enables the sepa-
ration of spawning from nonspawning fish; the
former may be distinguished by having a mode
around 3. 5 to 5. 5 and a very wide range. The
nonspawning group has a mode centering between
0. 6 and 1. 5. The gonad index of 3. 1 was selected
to separate the two groups. In the case of the
yellowfin, the two groups were not as clearly
distinguishable. An arbitrary index of 2.1 was
chosen to separate spawning from nonspawning
groups.

In order to delineate spawning localities
of deep-swimming bigeye and yellowfin, the
monthly mean gonad index in unit areas was cal-
culated. It was assumed that spawning occurs
in the vicinity of areas showing high gonad
indices.

In bigeye tuna, the basin of the Equatorial
Countercurrent is a principal center of spawning
in the western Pacific. It is also a good bigeye
fishing ground. There are indications of pro-
longed spawning throughout this area, with a
probable peak during the summer. In the eastern
equatorial Pacific (110° W. to 150° W.), spawning
is likely to occur between January and June in
the area just south of the Equator. There are
indications of spawning in the South Pacific near
the Tuamotu Islands between 10° S. and 20° S.,
but very few indications elsewhere in the Pacific.

For yellowfin, it has been reported that
spawning occurs nearly throughout the year in
the equatorial Pacific (8° S. to 10° N. , 120° W.
to 180°), with peak activity between March and
July. The present study indicates that through-
out the areas between the Equator and 12° N. ,
peak spawning probably occurs between July and
September. In the eastern area (100° W.to
150° W.) spawning occur s largely between April
and June in the area between the Equator and
10° S. Spawning in Hawaiian waters has been
reported to extend from about mid-May to the
end of October. Another spawning area in the
North Pacific is found in waters from Luzon
Island to southern Japan, where the season is
between April and June. In the South Pacific
it is highly probable that spawning occurs in the
Coral Sea and its adjacent waters and in the
vicinity of the Tuamotu Islands (10° S. to 25° S. ,
130° W. to 150° W. ) betweenOctober and March,
It has been reported that spawning of yellowfin
along the coasts of New Caledonia is likely to be
between October and March, with a probable
maximum during the summer.

In general, it appears that yellowfin
spawning occurs over a broad area, but is cen-
tered in the area of the South Equatorial Current.
The spawning season of yellowfin seems to vary
withlatitude. It is extended in equatorial water s,
but confined to the early summer in waters off
southern Japan, and to the summer months in
the Coral Sea and the Tuamotu Islands area.
The spawning seasons in these latitudes coincide
with the periods of best fishing.

Near-spawning bigeye (over 100 cm. in
length) comprise under 40 percent of thetotal
catch throughout the year in the western equa-
torial Pacific. The percentage composition in-
creases from west to east, reaching as high as
90 percent during the peak spawning season in
the eastern area. This marked increase of
mature fish from west to east indicates that the
spawning potential of bigeye is highest in the
eastern Pacific.

27

In yellowfin, the percentage composition
of near-spawning fish (over 110 cm. , the size at
which most yellowfin reach first maturity) is no
more than 40 percent throughout the year inthe
entire equatorial Pacific. There appears to be
no tendency for the proportion of mature fish to
increase toward the east, as there is in the case
of the bigeye. Previously it was thought that the
main yellowfin spawning season changed grad-
ually from east to west, but presently it is con-
sidered that this change can be attributed to lati-
tudinal variations.

King, Joseph E. , and Robert T. B. Iversen

Midwater trawling for forage organisms
in the central Pacific. /Conference

Paper VII - 1.7 (In press as _a U. S.
Fish and Wildlife Service Fishery
Bulletin, number unknown. )

Collections from 274 midwater trawl
hauls made in the central Pacific Ocean by the
Bureau of Commercial Fisheries inl951-56 were
quantitatively analyzedto obtain estimates of the
abundance and distribution of forage organisms.
Their occurrence in the trawl catches was com-
pared with the occurrence of similar organisms
in the stomachs of yellowfin, bigeye, skipjack,
and albacore tunas. Four trawls were utilized
(6-foot beam trawl, 1-meter ring trawl, and 6-
foot and 10-foot Isaacs-Kidd trawls) in double
oblique hauls between the surface and 400
meters.

The largest catches by the Isaacs-Kidd
trawls were made in the Aleutian Current and in
the region of upwelling at the Equator, with the
poorest catches south of latitude 5° S. in the
North Equatorial Current between latitude 10° N.
and 18" N. , and in Hawaiian waters. The great-
est variety of organisms occurred in catches
made in the South Equatorial Current and in the
Counter cur rent.

The re was a poor correspondence between
the composition of trawl catches and the contents
of tuna stomachs; this was not unexpected since
most hauls were made at night and tuna fishing
occurred in the daytime. There was marked di-
urnal variation in the trawl catches. Night hauls
produced catches larger in volumes, numbers,
and sizes of organisms. Diurnal differences in
the composition of the trawl catches were strik-
ing.

The larger trawls generally produced the
largest catches, but in catch per unit of mouth
area the trawls were about equally efficient in
each geographic area. The largest catches and

greatest variety of organisms were obtained in
the catches of the largest and most frequently
used trawls. All four trawls sampled about the
same phyla, classes, and orders; the major dif-
ferences occurred in the families and genera of
fishes. Only six juvenile tunas, from 18 to 60
mm. in length, were captured, although juvenile
tunas were known to be present in the area at the
time of the trawling.

Trawl catch volumes were correlated
with various environmental factors and found to
be more closely related to zooplankton than to
inorganic phosphate or to the uptake of C by
phytoplankton.

Checklists of the organisms captured
show the percent occurrence and average num -
bers per haul of members of a large number of
taxonomic categories according to six latitudinal
zones. A table of references useful in identi-
fying organisms captured by midwater trawling
was presented.

Legand, M.

Donnees biometriques sur les thons
anageoires jaunesenNouvelle-
Caledonie. /Conference Paper III -
1.7 (In Legand, M. and R. Desrosieres.
1960. Premieres donnees sur le thon
anageoires jaunesenNouvelle-
Caledonie. Office de la Recherche
Scientifique et Technique Outre-Mer,
Institut Francais d'Oceanie, Rapport
Scientifique No. 11, p. 33-54.)

Data (16 morphometr ic and 2 meristic
characteristics) were collected on 504 yellowfin
tuna caught in the vicinity of New Caledonia.
The relationship of total length (L) to standard
length (Ls) was found to be L = 1.085 Ls. In re-
gression analysis of morphometric data, regres-
sion equations of the form y = a+bx and y = axb
were used, rather than polynomial equations.
Nevertheless, for each character it was neces-
sary to calculate two equations for the data; one
for fish above about 80 cm. total length and one
for fish below that size. The average number of
gill rakers was 28.96 + 0. 075. This is one of the
smallest values observed in the Pacific and is
in accord with the west (small) to east (large)
cline reported by Royce for yellowfin from the
equatorial Pacific. There is an indication of
sexual dimorphism in pectoral fin length. For
the larger fishes, the relative growth of fins and
middle and posterior parts of the body and
relative increase in weight tend to be faster
than for smaller fishes (less than 80 cm. ). For
the anterior parts, the reverse is true. Thus,

28

yellowfin tuna from New Caledonia tend to have
smaller heads and longer dorsal and anal fins
than fish from further east.

reported for yellowfin near Hawaii. The average
stage of maturation seems to be more advanced
on the east coast of New Caledonia than on the
west coast.

Legand, M.

Quelques donnees biometriques sur les
albacores de la region ouest de 1 a
Nouvelle-Caledonie. (Conference
Paper III - 11. J (In Legand, M. and
B. Wauthy. In Press. Premieres
donnees sur l'albacore et les poissons
de longue-ligne. Centre d'Oceano -
graphie, Institut Francais d'Oceanie,
Noumea, Nouvelle-Caledonie, Rapport
Scientifique No. 24. )

Data (8 morphometric and 1 meristic
characteristics) were collected on 143 albacore
tuna caught to the west of New Caledonia. There
is a suggestion of sexual dimorphism in pectoral
fin length, but not in other characters studied.
In general, results were similar to those of
Kurogane and Hiyama for the Northern Coral
Sea, but different from their results in the
Northwest Pacific. The average number of gill
rakers was 28. 7 + 1. 2.

Legand, M.

Longueur, repartition des sexes et mat-
uration sexuelle des thons a nageoires
jaunes de Nouvelle-Caledonie. /Con-
ference Paper VII - 3. J (In Legand, M.
and R. Desrosieres. I960. Premieres
donnees sur le thon a nageoires jaunes
en Nouvelle-Caledonie. Office de la
Recherche Scientifique et Technique
Outre-Mer, Institut Francais d'Oce-
anie, Rapport Scientifique No. 11,
p. 7-20.)

Most yellowfin tuna taken near New Cale -
donia are 55 - 85 cm. standard length; much
smaller numbers of larger fish occurred. The
ratio of males to females is 1:1. 3. This ratio
has been observed in similar size yellowfin in
other parts of the Pacific, whereas for extremely
large fish it is 1:0. 6. The proportion of females
is much higher at the beginning of the spawning
season and very low at the end. Sexual maturity
is achieved at a larger size in males than in
females. Minimum gonad development is ob-
served between April and August, but even at
other seasons the individuals observed were far
from complete ripeness. Spawning may occur
between October and March, with a peak during
summer; similar observations, with respect to
the Northern Hemisphere in summer, have been

Legand, M. , and R. Desrosieres

Enquete preliminaire sur les contenus
stomacaux des thons a nageoires
jaunes des cotes deNouvelle -
Caledonie. /Conference Paper

VII - 4.J (I_n Legand, M. and

R. Desrosieres. 1960. Premieres
donnees sur le thon a nageoires jaunes
en Nouvelle-Caledonie. Office de la
Recherche Scientifique et Technique
Outre-Mer, Institut Francais
d'Oceanie, Rapport Scientifique
No. 11, p. 22-31.)

The stomach contents of 148 yellowfin
tuna taken by trolling along the south coast of_
New Caledonia in December 1958 and April 1959
were examined. In 1958, average fish weight
was 7. 1 kg. , and average content volume 11. 2 ml.
Of identified organisms, 51.9 percent were fish,
22.5 percent cephalopods, and 25.6 percent
crustaceans. In 1959, average fish weight was
8.3 kg., and average content volume 26.1 ml.
Stomachs contained 71. 7 percent fish, 4. 3 per-
cent cephalopods, and 24.0 percent crustaceans.
Content composition varies diurnally. A mini-
mum of fish and a maximum of crustaceans
are found in the morning. The percentage of
almost completely digested material is practi-
cally nil in the morning and increases during
the day. Balistoidea, Ostraciidae, Tetraodon-
tidae, Diodontidae, Acanthuridae larvae,
Dactylopterus, and stomatopods were the main
food items.

Legand, M. , and B. Wauthy

Importance presumee d' Alepisaurus sp.
dans le cycle biologique des thons de
longue-ligne au large de la Nouvelle-
Caledonie. /Conference Paper VII -
14. J (In Legand, M. and B. Wauthy.
In Press. Premieres donnees sur
l'albacore et les poissons de longue -
ligne. Centre d' O c e a n o g r a p h i e,
Institut Francais d'Oceanie, Noumea,
Nouvelle-Caledonie, Rapport Scien-
tifique No. 24. )

In experimental longline fishing foralba-
core off New Caledonia, 76 Alepisaurus sp.
(probably A. ferox) were caught, making this
the second most numerous species in the catch,

29

after albacore. The vertical distribution of
Alepisaurus catches, as evidenced by longline
hook numbers, closely paralleled that of alba-
core catches. The abundance of the two species
in the longline catches, however, appeared to be
inversely correlated. Indications of a similar
inverse correlation were found in published
American data on experimental longline fishing
in the northern and equatorial central Pacific.

Legand has previously reported that
Alepisaurus sp. is an important component of
albacore stomach contents in New Caledonian
waters. Numerical and volumetric data on
Alepisaurus stomach content composition pre-
sented in this paper show that Alepisaurus is an
excellent collector of a wide variety of plankters
and bathypelagic fishes. Squid and fishpredom-
inate in volume; crustaceans are present in im-
portant numbers but in small volum.e. Sonne of
the leading constituents of Alepisaurus stomach
contents, such as Alepisaurus and Sternoptyx
diaphana, have also been prominent in the stom-
achs of albacore from New Caledonian waters.

No important seasonal difference in
either total volume or composition was seen in
either species. Yellowfin differed from alba-
core in the considerably greater proportion of
fish in their diet and in the greater relative as
well as absolute volume of their stomach con-
tents (1. 68 cc. per kg. of body weight as com -
pared with 0. 73 cc. for albacore). The average
amount of squid consumed by albacore appeared
to increase offshore but the opposite trend was
shown by yellowfin.

Alepisaurus sp. was the fish that occur-
red most frequently in the stomachs of both
albacore (60 percent) and yellowfin (40 percent) ,
and the bramid-pteraclid group of fishes was
important in the diet of both species. Ostracion
sp. , which is also prominent in the diet of troll-
caught yellowfin from the New Caledonia coast,
was found in 45 percent of the yellowfin stomachs
but in only 20 percent of the albacore.

The crustaceans eaten by both species
of tuna were primarily decapods.

The a u t h o r s suggest that the apparent
inverse correlation of albacore and Alepisaurus
catches may result from an exclusion due in part
to predation by the former on the latter and in
part to competition for prey between the two
species.

Legand. M.

Contenus stomacaux desalbacores et
yellowfins captures a la longue-ligne
par l'Orsom III. /Conference Paper
VII -15.7 Tin Legand, M. and

B. Wauthy. In Press. Premieres
donnees sur l'albacore et les poissons
de longue-ligne en Nouvelle -Caledonie .
Centre de Oceanogr aphie , Institut
Francais d ' Oceanie /NoumeaJ, Rap-
port Scientifique No. 24. )

The stomachs examined were those of
117 albacore and 43 yellowfin from the longline
catches dealt with in the author's paper "Taille,
repartition sexuelle, cycle annuel de l'albacore
dans l'ouestde la Nouvelle -Caledonie. " The
average weights of these tuna were 21 kg. for the
albacore and 45 kg. for the yellowfin.

The average total volume of stomach
contents for the albacore was 14. 7 cc. , the
composition by volume being 45.4 percent fish,
44. 6 percent squid, and 10. 0 percent crustaceans.
The yellowfin stomachs contained on the average
80. 6 cc. , of which 78. 2 percent was fish, 1 6. 4
percent squid, and 5.4 percent crustaceans.

Legand, M.

Taille, repartition sexuelle, cycle annuel
de l'albacore dans l'ouest de la
Nouvelle -Caledonie. /Conference
Paper VII - 16. J (In Legand, M. and
B. Wauthy. In Press. Premieres
donnees sur l'albacore et les poissons
de longue-ligne. Centre d'Oceano-
graphie, Institut Francais d'Oceanie,
Noumea, Nouvelle -Caledonie, Rapport
Scientifique No. 24. )

From 1959 to July 1961 experimental
tuna longline fishing from the ORSOM III at 24
stations took 140 albacore within 200 miles of
the southwest coast of New Caledonia, between
21°30' S. and 24° S. , using 7-hook units 500 m.
long. Numbers of albacore per 100 hooks fished
were 1.5 to 5.0, exceptionally 10.0.

The lengths ranged from 825 to 1075 mm.
There was a significant difference in size between
the sexes; the males averaged 966 mm. and
20. 6 kg. , the females 930 mm. and 18. 8 kg .
The average size of the albacore captured was
significantly greater in summer than winter,
although there was no important seasonal depar -
turefrom the overall average sex ratio, which
gave 27.5 percent females. One example of
hermaphroditism was found.

The seasonal trend of the ovary volume
to body length relationship indicated summer
(December- January) spawning. Five ovary

samples over 200 cc. in volume and over 300 cc.
were thought to indicate that the spawning area
was not far distant from the area of collection.

The distribution in depth of captures,
judged from the presumed relative depth of the
seven hooks on each unit of longline, indicated
that the albacorewere concentrated about 50 m.
deeper in summer than in winter. This differ-
ence corresponds roughly to the seasonal range
of vertical movement of the 19° C. and 21° C.
isotherms in the area.

Marr, John C. , and Lucian M. Sprague

The use of blood group characteristics
in studying subpopulations of fishes.
/Conference Paper III - 4. J (In press
in papers of the International Com -
mission for North Atlantic Fisheries
Tagging Symposium, Woods Hole,
1960.)

The necessity for studying .population
units of fishes, the desirability of using genetic
characteristics in such studies, and the nature
of blood group systems are briefly reviewed.

Examples are drawn from the M-N and
A-B-O blood groups in man. Examples are given
of blood group systems recently found in several
bony fishes, including western Atlantic herring,
northeastern Pacific sardine, sockeye salmon,
albacore tuna, and one elasmobranch, the spiny
dogfish.

Illustrations are given of how data on
blood group systems are useful in attacking the
kinds of problems encountered by fishery biol-
ogists. Such problems include (1) determination
of whether one or more than one subpopulation
is contributing to a fishery in a particular area,
(2) determination of whether fish from two fish-
ing areas belong to the same or different sub -
populations, and (3) determination of the con-
tributions of two known subpopulations to a
single fishing area.

It is suggested that blood group data will
also contribute to the solution of broader prob-
lems.

Matsumoto, Walter M.

Identification of larvae of four species
of tuna from the Indo-Pacific region.
I. /"Conference Paper VII - 9.7
(Published in 1962 by the Carlsberg
Foundation as Dana Report No. 55,
14 p.)

Examination of larval thunnids collected
from Indo-Pacific waters by the "Dana" during
the 1928-30 round-the-world oceanogr aphical
expedition resulted in the tentative identification
of larvae of four species of thunnids, Para-
thunnus sibi (Temminck and Schlegel), Thunnus
germo (Lacepede), T. orientalis (Temminck
and Schlegel), and Kishinoella tonggol(Bleeker),
which have hitherto been unidentified. Neo-
thunnus macropterus (Temminck and Schlegel)
has been identified and described by numerous
authors, soitwas not included in this discussion.
To avoid digressions concerning the nomen-
clature of the tunas found in different parts of
the world, the earliest generic and specific
names given to tunas from this region were
used.

Species identification was done by segre-
gating the larvae from three localized areas
into various "types" on the basis of number and
position of chromatophores on the body, partic-
ularly the chromatophores along the dorsal edge
of the trunk. The number of larval types in each
area was then compared with the species com-
position of adult tunas caught on longline fishing
gear, including a species (K. tonggol) which is
known to be present in the areas, but which is
not commonly taken on this gear.

All specimens examined had 40 myomeres
and had no pigmentation over the forebrain. Lar-
vae with no pigmentation along the dor sal edge of
the trunk, exclusive of the caudal fin, but with one
to five chromatophores along the ventral margin
were designated as P. sibi. Larvae similar to
P. sibi but having one chromatophore along the
dorsal margin of the trunk, at the base of either
the second dor sal fin or one of the dorsal finlets ,
were diagnosed as T. germo. Larvae similar to
P. sibi but having two or three chromatophores
along the dorsal edge of the body, the initial
chromatophore being at the base of either the
second dorsal fin or one of the dorsal finlets,
were identified as T. orientalis. On all these
three species, the origin of the second dorsal
fin was located on the 16th myomere. Larvae
similar to T. orientalis but having the initial
dor sal chromatophore anterior to the 15th myo-
mere or the origin of the second dorsalfin were
designated K. tonggol.

Mimura, Koya

Studies on Indo-maguro. /Conference
Paper I -3 J

Indo-maguro, or bluefin tuna, are caught
by the Japanese in two places off Australia, the
Old and the New Fishing Grounds. These grounds

lie to the northwest and west of Australia; no
bluefin occur in peripheral areas and few on the
grounds outside of the September-April season.
The catches differ in that there are two catch
peaks on the Old Ground and one on the New,
and the Old Ground fish are large through the
season whereas the New Ground fish are small
at the season's peak. The fish on both grounds
are thought to be spawning groups.

Greatest food consumption occurred at the first
feedings early in the day, and smaller amounts
were eaten through the remainder of the day.
Shrimp exoskeletons begin to occur in the feces
about 1. 5 hours after a meal at 74° F. They ate
little or nothing after dark and would not take
food particles from the bottom of the pool. The
size of food particles they would eat decreased
as they became satiated.

Nakamura, Eugene L.

Nakamura, Hiroshi

The establishment and behavior of skip-
jack tuna (Katsuwonus pelamis) in
captivity. /Conference Paper IV - 2.J

Skipjack tuna (2-6 pounds) were success-
fully maintained in an outdoor pool for 5-1/2
months at the Kewalo Basin docksite laboratory
of the Bureau of Commercial Fisheries Biolog-
ical Laboratory at Honolulu. The circular pool,
4 feetdeep and23 feet in diameter, was supplied
with 50 gallons of oxygenated salt water per min-
ute. Successful establishment was achieved by
transferring the fish from the place of capture
to the shore pool in a portable tank. The port-
able tank contained 620 gallons of water and,
while on the vessel, was supplied with 100 gallons
of new water per minute. Skipjack were caught
by pole-and-line , lowered into the portable tank
and allowed to shake out the barbless hook. On
shore the portable tank was lowered into the pool,
and the skipjack were allowed to swim out. The
fish fed in captivity, and recovered from minor
wounds received at capture. After 4 months one
fish had sunken eyes, but could still feed.

Skipjack swim with their mouths agape,
and erect their first dorsal and pectoral fins
when turning. All fins are erected to maximum
extension when the fish decelerate s u d d e n 1 y.
They demonstrate no rheotaxis. They schoolin
captivity, but schooling is disrupted when food
is presented. While the tuna are feeding or when
they are presented with a food stimulus, verti-
cal bands appear ontheir dor sal lateral surface.
When the fish were trained to associate a slap
on the water surface with food, the appearance
of vertical bars could also be elicted by the slap
alone. After the tuna had fed to satiation these
responses did not occur. When not in a feeding
state, the tuna is marked with horizontal bars
on the latero-ventral surfaces. Other noticeable
colorations are the silvery tongue and the lead-
ing white spine in the first dorsal fin.

When fed to satiation once a day they
ate 1.6 ounces of squid and shrimp per pound of
skipjack per day, but when fed 13 times per day
this increased to 3.2 ounces per pound per day.

An outline of the tuna longline grounds
in the Pacific. /Conference Paper

I - 17

The Pacific Ocean is characterized by a
series of current systems extending in an east-
west direction. These systems are distinct en-
vironments and have distinctive fisheries, for
example, the North Pacific Current north of 28°
is noted for its albacore, while part of the South
Equatorial Current is conspicuous for yellowfin.
In addition to stratification by current systems,
the fisheries show east-west gradients in length
composition, as well as variations in amount of
catch per unit of fishing effort. There is an over-
all tendency for tuna and marlin catches to be
heavier in the Southern Hemisphere than in the
Northern Hemisphere.

Otsu, Tamio, and Richard J. Hansen

Sexual maturity and spawning of albacore
in the central South Pacific Ocean.
/Conference Paper VII -Z.J (In press
as U. S. Fish and Wildlife Service,
Fishery Bulletin 204, vol. 62.)

Developmental stages of gonads of the
albacore, Thunnus germo (Lacepede), taken in the
central South Pacific Ocean by Japanese and
South Korean longline vessels based in American
Samoa were studied. The samples comprised
782 pairs of ovaries and 990pairs of testes col-
lected from 256 landings between August 1957 and
September 1958.

Occurrence of ova in late stages of de -
velopment indicates that the South Pacific alba-
core spawn during the southern summer, between
September and March, as opposed to the northern
summer spawning of the North Pacific albacore.
This difference in spawning periods is believed
to constitute evidence that the stocks of albacore
in the South Pacific and the North Pacific are
independent of each other. The data suggest that
the bulk of the spawning activity is confined to
the area between the Equator and latitude 20° S.

32

No east-west differences in occurrence of devel-
oping ovaries were discernible.

Otsu, Tamio, and Richard N. Uchida

A model of the migration of albacore in
the North Pacific Ocean. /Conference
Paper II - \J

On the basis of tag recovery data, age
and growth information, and distribution and
size frequency data from the various fisheries,
a model of the migration of albacore in the North
Pacific Ocean has been developed. This model
is consistent with the hypothesis that there is a
single population of albacore in the North Pacific
Ocean.

The migration of albacore within the
areas of the three major fisheries is in general
reflected by the seasonal shifting of the respec-
tive fishing grounds. The migration between
fisheries may be summarized briefly as follows :
A varying portion of the 2-, 3-, and 4-year-old
fish and nearly all of the older fish in the Amer-
ican fishery migrate westward each fall into the
Japanese longline fishery, and during the follow-
ing spring, into the Japanese live -bait fishery.
The remainder of the fish from the area ofthe
American fishery move westward to the mid-
ocean waters of the North Pacific, some as far
west as to the eastern fringe of the Japanese
longline fishing grounds. These fish, largely
young individuals, tend to return to the American
fishery the following summer. Thus, some alba-
core may be available to the American fishery
for as many as four or five successive seasons.

Of the more common sizes taken in the
Japanese live-bait fishery, only the 4- and 5-
year-old groups provide some fish that enter the
American fishery the following summer, but
these are few since 5- and 6-year-old fish com-
prise only a very small proportion in the Amer-
ican catch. This would explain why none ofthe
albacore tagged in the Japanese live -bait fishery
has thus far been retaken in the American fishery.

Albacore enter the winter longline fish-
ery from both the American fishery and the
Japanese live-bait fishery. A large part of these
fish migrate southwestward in the winter long-
line fishery and subsequently enter the live-bait
fishery in the spring, whereas a few separate
and migrate into the American fishery by sum-
mer.

A portion of the large adults occurring
in the Japanese winter longline fishery (6-year-
olds and older) move southward during the spring

into subtropical waters, where they makeup the
reproductive unit of the North Pacific population.

It is hypothesized that spawning occurs
in subtropical waters during the summer and
that the larval and early juvenile stages are spent
in these waters. When about 1 year old, the
fish migrate into temperate waters, but they do
not immediately join the exploited stock. The
albacore are generally not available to the com-
mercial fisheries until they reach the age of 2
or 3.

It appears that most of the recruitment
into the exploited stock takes place in the east-
ern rather than the western North Pacific. There
is a greater volume of migration of the commer -
cial sizes of albacore in the westerly direction
from the American fishery into the Japanese
fisheries than vice versa.

Ridgway, George J.

Distinction of tuna species by immuno-
chemical methods. /Conference
Paper III - 5]

Through the application of the Ouchter-
lony method of diffusion precipitin analysis, with
rabbit immune sera, the presence of species
specific differences in serum antigens of adult
tuna was demonstrated. The existence of these
differences was confirmed by absorption
methods.

In studies on soluble antigens of the
muscle tissue of tuna, evidence was obtained for
the distinction of skipjack from albacore, yel-
lowfin, and bigeye tuna.

No characteristic differences in their
soluble tissue antigens, allowing the mutual dis-
tinction of the latter three species, were found.
Technical problems in the study of soluble tissue
antigens, involving extraction media, stability
of extracts, and production of potent antisera
were encountered, and preliminary methods for
their solution developed.

The course was discussed whichfurther
developments in these and allied fields might
take resulting in possible distinction of larval
forms.

Roedel, Phil M. , and John E. Fitch

Taxonomy and nomenclature of the Pa-
cific tunas. /Conference Paper VI - Z]

The basic problems of taxonomy and
nomenclature of tunas still remain unresolved.
Even among American tuna research labora-
tories now studying eastern Pacific tunas, there
exist some differences in the usage of names.
Some uses stand on reasonably firm scientific
ground; others are based on custom and gener-
ally follow Kishinouye's lead.

In the category of true tunas are included
thebluefins, albacores, yellowfins, bigeyes, and
members of genera Kishinoella and Allothunnus.
Among the bluefins, the authors feel that (1) T.
maccoyi is a distinct species, (2) T. saliens is
at least subspecifically distinct from the Atlan-
tic form, (3) the relationship of T. saliens to
T. orientalis is unknown, and (4) until necessary
research is done, the best course is to call the
California bluefin T. saliens and the Japanese
T. orientalis.

There is but one species of albacore in
the North Pacific, but no one knows whether it
is in any way distinguishable from that in the
Atlantic. The Pacific albacore has been listed
as T. germo, G. germo, T. alalunga, and G.
alalunga. The question of specific names can-
not be properly resolved until a direct compari-
son of Atlantic and Pacific material is made.

The problem with yellowfins is whether
the various forms from the oceans of the world
are identical or whether they are specifically
and subspecifically distinct. This problem will
be resolved only by a global attack; pending that,
continued use of macropterus for the Pacific
forms is recommended.

For the bigeye, Pacific workers have
generally used sibi, and it seems wise to con-
tinue this practice for the present.

Serventy (1942)^'has documented the
case for the Australian northern bluefin, Kishi-
noella tonggol; the New Zealand fish, Allothunnus
fallai, rounds out the Pacific tunas.

In the category of the skipjacks are in-
cluded the skipjack, the black skipjacks, and the
frigate mackerels. The skipjack appear s almost
universally in the literature as Katsuwonus
pelamis. Such usage tacitly recognizes the
existence of a species worldwide in distribution .
K. vagans is used by some authors who regard
the Pacific form as separable from the Atlantic
form. There are no factual data to support
either view, and there is need for a direct com-
parison of specimens.

The black skipjacks are now universally
consigned to genus Euthynnus. The number and

definition of species are matters of debate, but
it is reasonably certain that alletteratus, linea-
tus, and affinis are valid names for valid species.
It is suggested that the name E. yaito be retained
for the western Pacific species until such time
as its confusion (it may be synonymous) with
affinis has been clarified.

As for higher classification, the
author s believe that Germo should be submerged
in favor of Thunnus and that Neothunnus would
have to be submerged in favor of Parathunnus,
on page priority, if their separation from
Thunnus seems advisable. Despite these opin-
ions, no changes are recommended at present,
except for Germo. Katsuwonus should be re-
tained as a separate genus because of the many
characters by which it differs from the three
black skipjacks.

These suggestions are offered for action:
(1) Determine the relationships of these fishes at
the specific or subspecific level and above all on
a worldwide basis as soon as sponsorship and
fundingcanbe arranged; (2) establish a commit-
tee which would submit a detailed proposal for.
actionto the FAO World Tuna Conference; and
(3) those concerned with the Pacific tuna resource
should implement the program through tuna re-
search agencies active in the Pacific basin, if
worldwide sponsorship cannot be obtained.

Rosa, H. , Jr. , and T. Laevastu

World distribution of tunas and tunafish-
eries in relation to environment. /Con-
ference Paper V - \J

Bluefin and albacore occur in the temper -
ate subtropical and tropical water s of the oceans
of the world, are often associated with frontal
zones, and have a narrow optimal temperature
range. Bigeye and yellowfin are mainly pelagic
and are found in the equatorial current systems
of the Pacific, Atlantic, and Indian Oceans.
Skipjack are found in the warmer temperate sub-
tropical and tropical waters of the world. Bo-
nitos and little tunas are found in the coastal
areas of the temperate subtropical and tropical
oceans.

Aggregations of tuna are to be found in
regions of shallow thsrmocline, cold and warm
eddies and intrusions, in areas of upwelling

37 Serventy, D. L. 1942. The tuna Kishi-
noella tonggol Bleeker in Australia. Journal of
the Council for Scientific and Industrial
Research, vol. 15, no. 12, p. 101-112.

34

along current boundaries, and in certain areas
near islands, sea mounts, and along continental
slopes. Each of these features may contribute
to enrichment of the surface waters. Although
temperature is a good indicator of each of these
features, it may not be the main factor directing
the behavior and distribution of tuna. Changes
in the environmental factors in the sea are the
result of interaction between the sea and atmos-
phere, and thus a correlation between meteoro-
logical factors and behavior of the tunas can be
found. A discussion of tuna fishing grounds and
methods is included.

Royce, William F.

A morphometric study of yellowfin tuna
Thunnus a 1 b a c a r e s (Bonnaterre).
/"Conference Paper III - b] (In press
as U. S. Fish and Wildlife Service
Fishery Bulletin, number unknown)

Morphometric measurements are com-
paredfrom 4,180 yellowfin tuna from 29 locations
in the Pacific Ocean, from the Atlantic Ocean
off Angola, Africa, and from the Indian Ocean
off Somaliland, Africa. The measurements used
are head length, pectoral fin length, second dor-
sal fin height, anal fin height, snout to insertion
of first dorsal fin, snout to insertion of second
dorsal fin, snout to insertion of anal fin, snout
to insertion ofventral fin, insertion ofventral to
anterior edge of vent, and greatest body depth.
Each measurement is related to fork length by
regression analysis, and each relationship is
called a character. Curvilinear regression due
to allometric growth is controlled bytransform-
ing some data to logarithms and by separating
all samples into small, medium, and large size
groups (< 80, 80-120, and > 120 cm. fork length ,
respectively). Mean character sizes are deter -
mined for each sample at lengths of 65 cm. , 100
cm. , and 140 cm.

A comparison of mean character sizes
from samples taken along the Pacific Equator
reveals a cline in most characters between the
vicinity of Costa Rica and the Caroline Islands.
The yellowfin from the eastern Pacific have
larger heads and greater distances from the
snout to the insertion of first dorsal, second
dorsal, ventral, and anal fins, a greater dis-
tance from insertion of ventral to insertion of
anal fin, and a greater body depth. On the other
hand they have shorter pectoral fins and much
shorter anal and second dorsal fins. The sam-
ples from the more temperate parts of the Pacific
and from off the coasts of Africa differ little
from some part of this cline.

A multiple character comparison of over-
lap among samples from near the Pacific Equa-

tor shows less than 50 percent overlap between
samples separated by 1, 500 miles, less than 25
percent overlap between samples separated by
3, 000 miles and less than 6 percent overlap be-
tween samples separated by 6, 000 miles. The
possibility of long intermigrations among the
equatorial stocks seems remote.

The full variation in length of pectoral
and heights of second dorsal and anal fins, which
most authors have used to separate the species
of yellowfin, occurs within the cline along the
Pacific Equator. This occurrence plus the con-
tinuous circumtropical high seas distribution of
the yellowfin indicates a single worldwide spe-
cies. The appropriate name is Thunnus alba-
cares (Bonnaterre) 1788.

Seckel, Gunter R. , and Thomas S. Austin

The association between Hawaiian skip-
jack landings and the oceanographic
climate. /Conference Paper V - 10_/

In an effort to relate the seasonal and
annual availability of Hawaiian skipjack to fac-
tors in their environment, it was found that the
season catch could be correlated with the per-
centage occurrence of northeast trades during
February through April for a number of years.
This correlation later failed. In the Hawaiian
Islands, low summer salinities (less than35 %a)
were also associated, although not without excep-
tions, with better than average annual landings.
Plotting the monthly rate of change of surface
temperature obtained at Koko Head, Oa h u,
against time, one obtains a heating curve with a
shape characteristic of the locality. Occurrence
of initial heating during February was followed
by an average or better than average fishing
season and initial heating during March by a
poorer than average season. This correlation,
which has held for the 10 years for which data
are available, is of predictive value.

In terms of environmental processes,
initial warming of the heating curve signifies the
beginning of the northward movement of the
boundary between the high salinity North Pacific
Central water and the lower salinity California
Current Extension water. Later, the boundary,
which during autumn and winter months lies just
south of the islands, moves into the island area
and accounts for the lower summer salinities.
Early northward movement of the boundary as
reflected by initial warming at Koko Head signi-
fies a well-developed circulation.

The 10-year Koko Head heating curve and
monthly skipjack landings show that catches

coincide with the summer cold advection period
and that the duration of the peak fishing is related
to the length of the summer cold advection period.

The excellent relations between environ-
mental factors and the availability of skipjack
indicate that changes in the magnitude of Hawai-
ian stocks due to changing magnitudes of year
class or fishing pressure may not be of major
importance. They indicate that, in addition to
a favorable type of water, favorable dynamic
conditions are necessary for a good fishing sea-
son. Since fishing success seems to be associa-
ted with the dynamics of the system, it is not
surprising that an index reflecting environmental
processes (initial heating at Koko Head) has
proved to be of predictive value.

Sprague, Lucian M. , and Leslie I. Nakashima

A comparative study of the erythrocyte
antigens of certain tuna species. /Con-
ference Paper III - 8_/

The C-system of the skipjack (Katsu-
wonus pelamis) was recognized by the action of
bovine normal serum containing natural anti-C
fractions on the cells of C-positive ski pjack
(Cushing, 1956).!/

C-like blood factors also occur o n the
erythrocytes of albacore (Germo alalunga), big-
eye (Parathunnus sibi),and yellowfin (Neothun -
nus macropterus). To date, absorption results
have not revealed C-system antibodies which
will differentiate subtyping relations between
the species, although such relations probably
exist. The relative frequency of occurrence of
C-positive individuals is quite different among
the members of the species tested. Albacore
(120) were 94 percent, bigeye (113) were 77 per-
cent, and yellowfin (37) were 98 percent positive
with standard C reagents.

The A-system of the skipjack is recog -
nized by specific agglutinates formed in extracts
of the seeds of Glycine max (soy). A-positive
bloods are also commonly found in the bigeye
and albacore tunas, but to date they have not been
recognized in the few yellowfin tested. Several
other inter specific serological relationships are
also under investigation.

Suzuki (1961)2/ has reported his find-
ings with regard to the serological cross
reactions of these species. At the present time
it is not known whether or not the relationships
described here fall within those described by
Suzuki.

Sprague, Lucian M. , and Leslie I. Nakashima

Studies on the erythrocyte antigens of
the skipjack tuna (Katsuwonus
pelamis). /Conference Paper III - 9. 7
(See also abstracts of Symposium
Papers, Tenth Pacific Science Con-
gress. Symposium on immunogenetic
concepts in marine population
research, p. 186. )

At least five blood factors, which form
four systems of blood groups, have been identi-
fied on the red blood cells of the skipjack tuna.

One, the C antigen, has been described
by Cushing (1956). _' C-positive individuals are
recognized by the action of natural bovine and
ovine heteroagglutinins.

Four additional blood factors are now
recognized by the use of saline extracts of legume
seeds. Extracts of Glycine max detect A-positive
bloods, extracts of Phaseolus vulgaris detect
D-positive bloods, and extracts of Virgilia di-
varicata and Caragana arborescens detect two
blood factors in the B system, Be and Bf. The
relationships of Be and Bf are not well under-
stood except that they are mutually exclusive
properties, Be-positive animals being Bf-
negative and vice versa. About 20- 30 percent
of the skipjack tested are Be -Bf-negative.

Of these reagents, those recognizing D-
positive individuals and those recognizing Bf-
positive individuals are not sufficiently definitive
for use in population studies.

R eagents detecting C -positive, A-
positive, and Be-positive animals, however,
may be used to explicitly categorize skipjack
erythrocytes. These reagents have been used
in tests of 688 skipjack from the island or island
systems of Hawaii, Johnston, Christmas, Mar-
quesas, and Rangiroa (Tuamotu).

4/ Cushing, John E. 1956. Observations

on serology of tuna. U. S. Fish and Wildlife
Service Special Scientific Report: Fisheries
No. 183, 14 p.

5/ Suzuki, Akimi. 1961. Serological studies
of the races of tuna - V. The blood groups of
yellowfin tuna. Report of Nankai Regional Fish-
eries Research Laboratory No. 13, p. 53-67.

6/ See footnote 4.

When the frequencies of the occurrence
of Be individuals from these areas were com -
pared, the relative proportion of Be individuals
sampled near Rangiroa was clearly distinct from
the frequencies of Be from all other areas sam-
pled (P < . 001; £- test).

The sample from the Marquesas Islands
is different from all other areas with respectto
the frequency of the occurrence of C-positive
individuals (. 05 < P < . 01; ■l- test).

On the contrary, samples taken from
Hawaii, Christmas, and Johnston Islands exhibit
marked homogeneity in the frequencies of the
characters A, C, and Be. These data indicate
the occurrence of at least two reproductively
isolated stocks of skipjack in the areas sampled.

Basin docksite laboratory of the Bureau of Com-
mercial Fisheries Biological Laboratory at
Honolulu. Such salt ground water is similar to
oceanic water but contains only 0. 15 - 0. 69 ml./l.
dissolved oxygen. A device was designed to in-
crease the amount of oxygen to 95 - 100 percent
saturation at rates of flow up to 100 gallons per
minute. The aerator was composed of three
stacks of 16 trays (each tray 2 feet x 7 feet),
spaced at 2 -inch intervals and perforated at half-
inch intervals by one-eighth inch holes. Well
water was directed onto the top tray and perco-
lated down into a collecting basin below. Speci-
fications of the aerator, such as number of trays
and distance between trays, were based uponthe
operation of a test aerator in which these dimen-
sions could be altered.

Further studies are in progress which
will attempt to delineate the range and character
of these stocks in greater detail.

Sprague, Lucian M.

Blood group studies of albacore (Germo
alalunga) tuna from the Pacific Ocean.
/"Conference Paper III - 107

Reagents designated as anti-C by virtue
of their reactions with the erythrocytes of the
skipjack tuna (Katsuwonus pelamis) also recog-
nize closely related antigens in the albacore.

Suda, Akira

Comparison of abundance between alba-
core and b i g e y e in the northwe st
Pacific. ^Conference Paper VII - 5. J
(In press in Nankai Regional Research
Laboratory, Report No. 14. )

The possibility of a correlation between
albacore and bigeye abundance is discussed
using recently accumulated data. Catch and size
data of albacore and bigeye taken in the North
Pacific Current area during winter longlining
operations were used in this study. The data
examined were for the years from 1949 to 1959.

The relative proportions of C-positive
individuals of albacore taken in the fisheries of
North America and Samoa are highly signifi-
cantly different. Of 325 fish taken from North
America, 97.5 percent were C-positive, and of
74 fish taken from Samoa 85.1 percent were C-
positive. These data are interpreted as evi-
dence for .reproductive isolation between the
North Pacific and South Pacific albacore.

Data were presented on a blood - group
system designated G, in which at least two G
blood factors, Gi and G, , are recognized. To
date the relative proportions of Gi, G, and " "
(the three phenotypes of the G system) are simi-
lar for the two areas sampled.

Strasburg, Donald W.

An aerating device for salt well water .
/Conference Paper IV - l]

Salt-water wells drilled through h a r d
packed coral and sand are used to supply water
for the experimental facilities at the Kewalo

The author used index-S to represent

relative abundance of fish, and calculated S as

follows: S =-L£ 5 x,-;, where x- ; is the hooked
n i ) XJ XJ

rate (catch/100 hooks) in the i-th month and in

the j-th area, and n is 15 for albacore and 12 for

bigeye.

For albacore, there is a strong tendency
for index-S to fluctuate with large amplitude
either at a high or a low level, which continues
for a period of about 3 years and then changes
to the opposite level for an approximately equal
period. In comparison, the index-S for bigeye
appears to be rather stable. However, the
annual changes in index-S for both species are
somewhat similar when smoothed by a moving
average of 3 years.

The index-S1 (lengthfrequencies weighted
by hooked rate) was used to represent relative
abundance of each size group, S1 being calcula-
ted as follows: S1 = j 5 (rx)-, where r is the

ratio of the size group and x is the hooked rate
in the ij-th stratum. Index-S' shows that the
abundance of both species is strongly influenced

37

bv the existence of a dominant size group. With
the occurrence of one dominant size group, good
catches can be expected for the following 2 or 3
years.

Index-P (formula explained in author's
previous report), used as a measure of the pop-
ulation size of each year class, showed similar
annual change in both species.

As both index-S and index-P in both
species show similar changes, it is suggested
that the changes in year class size of albacore
and bigeye are caused by intraspecific and inter-
specific fac tor s. Since the patterns of distribu-
tion and population structures of the two species
are rather similar, some changes in environ-
mental conditions may cause similar changes in
the two populations.

Suzuki, Akimi

Blood types in tuna. /Conference Paper
III -2. J (See also Suzuki, Akimi et al.
Serological studies of the races of
tuna, I, II, III, IV and V. Report of
Nankai Regional Fisheries Research
Laboratory no. 8, p. 104-116 (1958) ;
no. 11, p. 17-23, 165-172 (1959); no. 12,
p. 1-13 (1960); no. 13, p. 53-67 (1961).)

Investigation of the erythrocyte antigens
of albacore, bigeye, and yellowfin tunas by
means of normal and immune sera has shown a
variety of antigenic differences.

In the albacore, the Tgl and Tg2 antigens
are recognized by rabbit immune sera. These
two antigens form a blood group system with
four phenotypes Tgl; Tg2; Tgl Tg2; and O (the
absence of Tgl or Tg2). In the bigeye, three
antigens are recognized, two of them very simi-
lar to Tgl and Tg2 of albacore. The antigen
bigeye-3also occurs in albacore taken from the
North Atlantic. Yellowfin appear to have antigen
y similar to Tg2 of albacore and bigeye.

An investigation of the agglutinins in tuna
sera revealed that there area variety of "serum
types" reactive with human Aand/or B erythro-
cytes.

Uchida, Richard N. , and Tamio Otsu

Analysis of sizes of albacore occurring
in various Pacific Fisheries -A pre-
liminary report. /Conference Paper
VII - llj

Published and u n p u b 1 i s h e d albacore
length frequency data from foreign and domestic
sources were analyzed to determine the general
age structure of the species and the contributions
of the several age classes to the major albacore
fisheries in the Pacific Ocean.

Of the three major albacore fisheries in
the North Pacific, the U. S. West Coast fishery,
the Japanese winter longline fishery, and the Ja-
panese spring live-bait fishery, the last normally
accounts for the largest percentage of the total
catch.

The 3-year-olds compose roughly 70 per-
cent of the American albacore landings, while
the 4- and 5-year-olds constitute a large part of
the Japanese landings.

Australia and Chile have albacore fish-
eries, but they catch only a small portion ofthe
albacore landed in the South Pacific. The
smallest albacore are taken in waters around
Australia and New Zealand, and these are esti-
mated to be about 2- and 3-year-olds. In the
small coastal fishery of Chile, the 3-year-olds
predominate, making up roughly 71 percent of
the catch.

The only major fishery for albacore in
the South Pacific is the Japanese tropical long-
line fishery. Fishing is concentrated in an area
between the Equator and latitude 30° S. , and
the predominant age group taken is the 6-year-
olds, which compose 42 percent of the total
landings.

Tagging results have shown that the alba-
core of the temperate North Pacific belong to a
single population, but the relationship between
the North and South Pacific albacore has not
been determined. Evidence indicates, however,
that the stocks in the North and South Pacific
are independent of each other.

Comparison of North and South Pacific
albacore landings indicates that 93 percent ofthe
fish taken in the North Pacific fisheries are im-
mature fish under 5 years old, while only 35 per-
cent of the South Pacific fish were estimated to
be under 5 years old.

A commercial longline fishery compara-
ble to that found in the tropical South Pacific is
nonexistent in the tropical North Pacific. It is
hypothesized that one of the causes for this ab-
sence of a longline fishery in tropical waters of
the Northern Hemisphere is the fishing effort
expended on the immature stock (3- to 5-year-
olds) during its migration in temperate North
Pacific waters, with consequent reduction in the

38

number of fishreaching 6 years of age, the pre-
dominant age group in the South Pacific longline
fishery. This condition is reversed in the South
Pacific , which may be the reason why the 6 -
year-old and older age groups are abundant
enough to sustain a commercial fishery.

Uda, Michitaka

Cyclical fluctuation of the Pacific tuna
fisheries in response to cold and warm
water intrusions. /Conference Paper
V - 7.7 (In press (1962) in Journal of
Tokyo University of Fisheries. )

Peak landings of skipjack from Japanese
waters have occurred at irregular intervals
since 1912. A study of oceanographic conditions
showed that good catches were made during years
with warm water temperatures, whereas poor
catches were made during years with cooler
water temperatures. These differences in tem-
peratures were primarily relatedto the relative
strengths of the warm Kuroshio and the cool
Oyashio.

It was postulated that recruitment of
skipjack is favored by the enriched zones asso-
ciated with upwelling in the Equatorial Counter -
current and near the Equator. From these trop-
ical waters there is a migration of skipjack
(composed mainly of medium- sized fish) into
Japanese waters. When the warm Kuroshio
water spreads over a broad area, more skipjack
become available to the Japanese fishery.

Conversely a strong Oyashio current
(cold water) hinder s the migration, and catches
are low. However, good catches may also be
made when both the Oyashio and Kuroshio are
strong. Under the latter conditions skipjack
are concentrated along the boundary between
the warm and cold water (Polar Front). It is
postulated that the yield of skipjack from Japa-
nese waters varies inversely with that from
American waters.

Albacore catch records also show peak
landings at irregular intervals for both the Japa-
nese and the U. S. fisheries. It is postulated
that the variations between these two areas occur
in a reciprocal manner, as was the case with
skipjack. It is further postulated that the tern -
peratures in the eastern and western Pacific
vary in a reciprocal manner, with pulsations
traveling west to east in the region of the domi-
nant westerlies, returning in the lower latitudes
dominated by the northeasterly trades. Intru-
sions of cold and warm waters into the coastal
areas may be related to fluctuations in the at-

mospheric pressure systems. During 1955-59,
an increase in pressure difference among the
Siberian and North Pacific Highs and the Aleutian
Low corresponded with a period of cooler tem-
peratures in the western Pacific, warmer in the
eastern Pacific.

Geographical variations in the location
of the North Pacific High in winter and spring
also affect the temperatures. Movement to the
northwest results in warm intrusions in the
western Pacific and good albacore catches, re-
ciprocal in eastern Pacific. Movement of the
high to the southeast corresponds to cool water
in the west and poor catches, warm water in the
east and good catches.

Bluefin catches off the coasts of Japan
have also shown periodic fluctuations, with a
decline in catch associated with periods of cold
water intrusion, an increase in catch with per-
iods of warming. The cause of these fluctuations
maybe related to dominant brood strength during
periods of rising temperatures. When cool
waters intrude southward into the spawning
grounds, one or more year classes are seri-
ously affected. However, these cooler waters
are comparatively rich in nutrients and, with a
reversal in temperature toward warming, suc-
ceeding year classes find more plentiful food
and favorable temperature conditions for their
migration northward into Japanese waters. Thus
we have a cyclical situation — a reduction of
year-class strength and the fishery during per-
iods of cool surface waters, followed by an in-
crease in brood strength during the subsequent
period of warming and a more favorable eco-
logical situation resulting from the enrichment
of the surface waters during the cool period.

Uda, Michitaka

Localized concentration of tunas in t h e
eddies along oceanic fronts. /Confer-
ence Paper V - 8. J (In press (1962)
in Journal of Tokyo University of
Fisheries. )

Aggregations of tuna aretobe found along
fronts, localized in eddies, cool or warm, and
in zones of upwelling. Variations in concentra-
tion and location of the tuna are associated with
growth, decay, and change in position of the
eddies. Such eddies are to be found associated
with the Polar Front and the subtropical conver-
gence and near the Equator.

Albacore catch records for the period
1951-60 and surface temperature data were con-
sidered for the areabetween 140° E. and 154° E.

39

The albacore were in the cooler cyclonic eddies ;
the skipjack in the warmer anticyclonic eddies
along the front and the blue fin in the cooler
coastal waters.

In exploratory longline fishing (35°-
45° N. , 160° E. - 160° W. , May-October), alba-
core were found between 15° - 21° C. with the
peak catches centered around 175 ° W. The north -
south and east-west distribution of albacore in
the region north of the subtropical convergence
(30° - 38° N. ) was also investigated. In an east-
west direction the peak catches were centered
between 170° E. and 180°, decreasing sharply to
the east and less sharply to the west. The peak
catches were recorded during midwinter . As to
the north-south distribution, the peak catches in
the fall and winter centered about 38 ° N., moving
to about 30° N. in March. The secondary peak
in latitudes 30° - 20° N. , west of 140° W. sug-
gests to the author migration along the sub-
tropical convergence.

In the western half of the Pacific, yellow-
fintuna are caught along the Equatorial Counter-
current and are associated with areas of high
productivity, which are in turn related to a series
of eddies, i.e. eddies localized at about 135° -
145° E. , 155° - 165° E. , 175° E. - 175° W. , and
155° - 157° W.

In the eastern equatorial Pacific, the
rich yellowfin areas are associated with the
regions of shallow thermoclines. The equato -
rial convergence at latitudes 1° to 3°N. may
also concentrate yellowfin either through the
concentration of food or through a barrier
effect.

It i s proposed that secular changes in
oceanographic and fishery conditions are related
to climatological changes and the relationships
should be more fully studied.

Watson, Margaret E. , and Frank J. Mather III

Species identification of juvenile tunas
(genus Thunnus) from the Straits of
Messina, northwestern Atlantic, and
the Gulf of Mexico. /Conference Paper
VII - 137

Two vertebral characteristics visible in
soft X-rays of juvenile fish as well as in hard
X-rays of adult fish provide the first positive
identification of juvenile bluefin tuna(T.
thynnus), yellowfin tuna(T. albacares), blackfin
tuna (T. atlanticus), and albacore (T. alalunga).
Blackfin tuna are separable from the other spe-

cies by having 19precaudal and 20 caudal verte-
brae, a count which contradicts the work of
de Sylva (1955). U The other s p e c i e s having
identical vertebral counts,18 +21, are separable
one from each other on the basis of the position
of the first ventrally directed parapophyses. For
the yellowfin, this structure appears on the
seventh precaudal, for the albacore on the ninth,
for the bigeye and bluefin tuna on the eighth. A
juvenile bigeye (T. obesus) has as yet not been
X-rayed. It is presumed that the possible key
characters for separating a juvenile bluefin from
a juvenile bigeye would involve those also appli-
cable to the adults, the measurement of the orbit
diameter and depth, as well as comparing the
contour of the lateral line characteristic of each
species.

Yabe, Hiroshi, and Shoji Ueyanagi

Contributions to the study of the early
life history of the tunas. /"Conference
Paper VII - 67

Larval net tows, dip netting, and survey
of stomach contents of adult fishes since 1949
by the Nankai Regional Fisheries Research
Laboratory have resulted in collection of approx -
innately 2,000 tuna larvae, 1,000 istiophorid
larvae, and considerable numbers of juveniles
of these fishes. The areas covered include a
great portion of the Indian and Pacific Oceans.
Larvae were taken in 1.4 or 2.0 m. nets hauled
horizontally, either at the surface or at three
levels, the deepest at 40-50 m.

Larvae of Katsuwonus pelamis, Auxis
tapeinosoma, Neothunnus macropterus, and
Thunnus orientalis are described. In addition,
two types, A and B, suspected to belong to alba-
core and bigeye, respectively, are recognized
through their geographical and seasonal occur-
rence. These types are thought to be quite
similar to Neothunnus larvae with respect to the
absence of pigmentation on the trunk and late
appearance of chromatophores over the fore-
brain. Type A is characterized by the presence
of pigment on the tip of the upper jaw in speci-
mens about 8 mm. in fork length and the absence ,
or only very faint presence, of pigment on the
tip of the lower jaw. Type B is mainly charac-
terized by pigment on the tip of the upper jaw at
5.3 mm. and on the tip of the lower jaw at
7. 0 mm. in fork length.

7/ de Sylva, Donald P. 1955. The osteology
and phylogenetic relationships of the blackfin
tuna, Thunnus atlanticus (Lesson). Bulletin of
Marine Science for the Gulf and Caribbean,
Vol. 5, No. 1, p. 1-41.

40

Horizontal distribution of tuna larvae is
discussed with some mention of juveniles; how-
ever, these distributions are treated only quali-
tatively. In low latitudes between 10° N. and
10° S. , larvae seem to occur all year round, but
in higher latitudes they tend to occur in spring
and summer. Larvae of frigate mackerel (A.
tapeinosoma) also have a wide distribution,
however, their abundance is assumed to be high
in waters close to islands. Larvae of T. orien-
talis are taken in waters in the vicinity of Luzon
Island, Okinawa, and in the area to the north of
the Bonin Islands during May and June. They
are assumed to be abundant also in the area of the
Kuroshio Current. Most of the yellowfin (N.
macropterus) larvae are taken in tropical (equa-
torial) areas, and some are found in subtropical
areas which are under the influence of warm
currents. Larvae representing types A, taken
in July, and B, taken in December, are present
in the area between latitudes 10° N. and 25° N.
in the western Pacific.

Larvae of all five istiophorid species
distributed in the Indo-Pacific areas are identi-
fied. Shortnosed spearfish (Tetrapturus
angustirostris Tanaka), sailfish ( Istiophorus
orientalis T. and S.), and striped marlin
(Makaira mitsukurii J. and S. ) are characterized
by a long snout, and black marlin (Eumakaira
nigra Nakamura) and white marlin (Marlina
marlina J. and H. ) are characterized by a short
snout. The former three species are distin-
guished from one another by the profile of t h e
head and the number of dorsal fin rays, while
the latter two species are distinguished from
each other by the shape of the pectoral and dor-
sal fins.

Results of larval net hauls indicate that
both tuna and istiophorid larvae undergo vertical,
diurnal migration in the upper 50 meters of
water.

Yabuta, Yoichi, and Mori Yukinawa

Age and growth of yellowfin tuna. /Con-
ference Paper VII - 7.7 (See also
Yabuta, Yoichi et al. Age and growth
of yellowfin tuna. Rept. Nankai Reg.
Fish. Res. Lab. no. 5, p. 127-133
(1957); no. 11, p. 77-87 (1959); no. 12,
p. 63-74 (I960).)

Length frequency distributions of yellow-
fin tuna taken by pole and line and by longline in
waters adjacent to Japan were analyzed, and a
growth curve was obtained. The scale method
of age determination was also used to derive a

growth curve. Tag recovery data substantiated
the results obtained by the other two methods.

In the length frequency method, the
monthly modal mean lengths for each age class
were plotted for the years between 1953 and 1956,
and the progression in size was noted. Of scale
samples from 2, 087 fish examined in scale
studies, those from 1,204 (57.7 percent) were
unreadable. Unreadable scales, however, oc-
curred more frequently in larger fish. There
were 24 percent unreadable samples from fish
under 100 cm. in length, 68 percent from fish
between 101 cm. and 131 cm. , and 95 percent
from fish larger than 131 cm. Scale studies also
indicated that two rings are formed each year,
one in March and April and the other in Septem-
ber and October.

In general, the growth rates estimated
by the length frequency method and the scale
method and from tagging data were in good agree-
ment with one another. The results showed
that the yellowfin is a relatively rapid-growing
tuna and that growth during the early stage of
life is particularly rapid. The first major group
of fish entering the commercial fishery (at about
50 cm. ) was estimated to be 1-year-old as deter-
mined by the scale method.

Yamanaka, Hajime, and Noboru Anraku

Relation between the distribution of tunas
and water masses of the North and
South Pacific Oceans west of 160° W.
/"Conference Paper V - 57

A detailed examination of temperature
and chlorinity in the Pacific west of 160° W. ,
and in particular of temperature-chlorinity
relationships in the upper 200 meters, suggests
that the surface water layers can be divided into
a series of types having characteristic ranges
of temperature and chlorinity. The observations
are grouped into (Northern Hemisphere) winter
and summer classes, and the water types given
preliminary designations based upon the current
system which dominates the area in which each
occurs. Thus, for example, there is a type O
surface water, in the region of the Oyashio,
which is associated with the underlying Sub-
Arctic water mass, there are types K and N,
representing the Kuroshio and North Equatorial
Current surface water types which overlie the
Western North Pacific Central water mass, and
there are water types associated with the
Countercurrent, equatorial waters, the South
Equatorial Current, the Coral Sea, the Central
and southwest Tasman Sea areas, and the Sub-
Antarctic.

In general, the water types are relatively
uniform from east to west. There is evidence
of seasonal movement toward and away from the
Equator, and the area covered by each water
type varies seasonally. These movements are
interpreted as reflecting seasonal changes in the
location and intensity of the current system.

An approximate relation is shown between
the occurrence of tunas and the location of vari-
ous surface water types. The albacore in their
feeding stage appear in the western K (Kuroshio)
type, while albacore in the spawning stage are
found in the southern N (North Equatorial Cur-
rent) surface water type. Similarly, bigeye,
yellowfin, and striped mar lin appear to be asso-
ciated with specific surface water types, often
appearing in water of two different types without
being abundant in an intermediate third type
which geographically separates the two regions
of abundance.

Yuen, Heeny S. H.

Experiments on the feeding behavior of
skipjack at sea. /Conference Paper
IV - 37

These experiments were conducted at
sea from the Charles H. Gilbert, research ves-
sel of the Bureau of Commercial Fisheries Bio-
logical Laboratory, Honolulu, on skipjack
schools which had been attracted to the ship by

chumming with live bait and were being hooked
by pole and line. The influence of water sprays,
dead bait, various species of live bait, and glit-
ter (a material obtained from artist1 s supply
shops) on the feeding response of skipjack was
investigated. Response was measured by catch
rate (number caught per hook per minute) and
by feeding attack rate (number of attacks on bait
or hooks per fish per second). The latter statis-
tic was obtained from 16 mm. color film shot
with a cine-camera during the experiments from
the underwater viewing port at the stern of the
Charles H. Gilbert. Water sprays seemed to
increase the responses when anchovy (Stolephor-
ous purpureus), mountain bass (Kuhlia sandvi-

censis), tilapia (Tilapia m o s s a m b i c a), and
goatfish (Mulloidichthys samoensis) were used
as bait, to decrease the catch rate when mullet
(Mugil longimanus) was used, and to h a v e no
effect when silversides (Pranesus insularum)
were used. The sprays may change the bait's
behavior rather than stimulate skipjack directly.
When different bait species were used, caranx
(Caranx mate) and anchovy elicited greater re-
sponses than silversides, and equal responses
resulted from alternating anchovy and topminnow
(Limia vittata), tilapia and mullet, and tilapia
and mountain bass. Live bait was more effec -
tive than dead bait, and glitter seemed to raise
the attack rate slightly but not the catch rate.
Skipjack move toward shiny objects, but the
movement of the food seems to provide the
stimulus necessaryto result in a grasping of the
food.

LIST OF PARTICIPANTS

A. Dunbavin Butcher

Director, Dept. of Fisheries and Wildlife

605 Flinders St. , Extension

Melbourne C.3, Australia

British Columbia (Canada)

J. C. Stevenson
Asst. Director, Pacific Area
Department of Fisheries
Vancouver, B. C.

Yoshio Hiyama
Department of Fisheries
Faculty of Agriculture
University of Tokyo
Bunkyo-ku, Tokyo, Japan

Motoo Inoue

Fisheries Research Laboratory

Tokai University

149 Shimazaki-cho, Shimizu-shi

Shizuoka-ken, Japan

Nobuyuki Kawamoto

University of Mie

Mie Prefecture, Japan

Cesar L. Raza
Sub-Director General
Departmento de Pesca
Ministerio De Fomento
Quito, Ecuador

Hong Kong

J. Derek Bromhall

Director, Fisheries Research Station,

c/o Co-operative Development and

Fisheries Dept.
Li Po Chambers, 9th Floor
Central, Hong Kong

Jun Nakagome

Kanagawa Prefectural Fisheries

Experimental Station
Kanagawa, Japan

Keiji Takeda

Fisheries Section, Economic Dept.

Nagasaki City Hall

Nagasaki, Japan

Michitaka Uda

Tokyo University of Fisheries
Shiba Kaigan-dori, Minato-ku
Tokyo, Japan

Italy

Horacio Rosa, Jr.
Chief, Marine Resources Section
Fisheries Biology Branch
FAO of the United Nations
Viale delle Terme di Caracalla
Rome, Italy

Japan

Nankai Regional Fisheries Research

Laboratory
Sanbashi-dori, Kochi-shi
Kochi, Japan:

Katsumi Yamamoto
Fisheries Agency, Kaiyo 2-ka
Ministry of Agriculture and Forestry
2-1 Kasumigaseki, Chiyoda-ku
Tokyo, Japan

New Caledonia

Michel Legand

Institut Francais d'Oceanie

Office de la Recherche Scientifique

et Technique Outre-Mer
Noumea, New Caledonia

New Guinea

Hiroshi Nakamura, Director
Akimi Suzuki
Shoji Ueyanagi
Yoichi Yabuta
Hajime Yamanaka

A. M. Rapson

Division of Fisheries

Port Moresby, New Guinea

New Zealand

Seibin Arasaki
University of Tokyo
Tokyo, Japan

J. A. F. Garrick
University of New Zealand
Wellington, New Zealand
(Presently at the U. S. National Museum,
Washington, D. C.)

Maurice Newman
P. Feron and Son, Ltd.
P. O. Box 83
Christchurch, New Zealand

Philippines

Douglas Walton

Star-Kist Foods, Inc. and University of
Southern California
(Mailing address:

411 Caminodelas Colinas, No. 3
Redondo Beach, California)

Bureau of Fisheries, Department of

Agriculture and Natural Resources,
Diliman, Quezon City, Philippines:

V. Alvarez (Presently at the University
of Hawaii)

Inocencio A. Ronquillo, Chief

Hydrology and Fisheries Biology
Section

United States (Continental)

Maurice Blackburn

Scripps Institution of Oceanography

La Jolla, California

Charles R. Carry
Executive Director

California Fish Canners Association, Inc.

Ferry Building

Terminal Island, California

W. M. Chapman, Director
The Resources Committee
7 39 Golden Park Avenue
San Diego 6, California

John E. Cushing, Chairman
Department of Biological Sciences
University of California at Santa Barbara
Goleta, California

Robert H. Gibbs, Jr.
Department of Biology
University of Boston
Boston, Massachusetts

Robert W. Hetzler
Star-Kist Foods, Inc.
Terminal Island, California

Margaret Watson

Woods Hole Oceanogr aphic Institution

Woods Hole, Massachusetts

Stanley Watson

Woods Hole Oceanogr aphic Institution

Woods Hole, Massachusetts

Bureau of Commercial Fisheries:

Dayton L. Alverson

Base Director

BCF Exploratory Fishing and Gear

Research Base
2725 Montlake Boulevard
Seattle 2, Washington

James H. Johnson
BCF Biological Laboratory
P.O. Box 6121, Pt. Loma Station
San Diego 6, California

Stewart Springer, Chief
Branch of Exploratory Fishing
Division of Industrial Research
Bureau of Commercial Fisheries
Washington 25, D. C.

Inter-American Tropical Tuna Commission,
c/o Scripps Institution of Oceanography ,
La Jolla, California:

Witold L. Klawe
Douglas Vann

United States (Hawaii)

Herbert D. Hart

General Manager

Hawaiian Tuna Packers, Ltd.

P. O. Box 238

Honolulu 9, Hawaii

Phil M. Roedel

Marine Resources Manager

Marine Resources Operations

California State Fisheries Laboratory

Terminal Island, California

William Kanakanui

Manager

Tuna Boat Owners Association

P. O. Box 238

Honolulu 9, Hawaii

William F. Royce, Director
Fisheries Research Institute
Fisheries Hall No. 2
University of Washington
Seattle 5, Washington

Carl Nemoto

Division of Fish and Game

Department of Land and Natural Resources

P. O. Box 5425 - Pawaa Station

Honolulu 14, Hawaii

44

University of Hawaii
Honolulu 14, Hawaii:

William A. Gosline
Department of Zoology

Robert W. Hiatt

Dean, Graduate School and Director
of Research

Albert L. Tester
Department of Zoology

Bureau of Commercial Fisheries
Biological Laboratory
P. O. Box 3830
Honolulu 12, Hawaii:

Thomas S. Austin
Richard A. Barkley
Robert P. Brown
Mary Lynne Godfrey
Reginald M. Gooding
James R. Holloway
Robert T. B. Iversen
Everet C. Jones

Betty Ann Keala
Robert E. K. D. Lee
John J. Magnuson
Herbert J. Mann
John C. Marr
Walter M. Matsumoto
Frank A. Moriguchi
Robert A. Morris
Eugene L. Nakamura
Leslie I. Nakashima
Hazel S. Nishimura
Tamio Otsu
Charles J. Rollet
Gunter R. Seckel
Kenneth Sherman
Richard S. Shomura
Lucian M. Sprague
Donald W. Strasburg
William T. Tanaka
Thomas Y. Toyama
Richard N. Uchida
Wilvan G. Van Campen
Kenneth D. Waldron
Howard O. Yoshida
Heeny S. H. Yuen

45

MBL WHOI Libiary

5 WHSE 01542