FOOD OF BALEEN WHALES WITH REFERENCE
TO WHALE MOVEMENTS
TAKAHISA NEMOTO
The close relationship between foods and whales has long been recognized
and many works on the role of foods in the interrelationship between
foods and whales have been undertaken in many parts of the worldopen sea. In the previous report (Nemoto, 1957), I described the shortsummarized historical reviews on the problem and tried to discuss the
foods of baleen whales in the northern part of the North Pacific. In
the paper, the main foods of the northern Pacific baleen whales caught
by Japanese pelagic expeditions are described. But after the year 1956,
Japanese expeditions have covered broader areas in the northern Pacific,
and insufficient data in the paper have been complemented by the
successive researches. The previous paper of mine, at it was, should
be regarded as a preliminary report on this problem, and I would add
the more detailed discussions here but some discussion described in
my previous paper may be omitted for the convenience for the preparation of the paper.
Japanese investigation of foods of baleen whales are also carried out
in the waters adjacent to Japan as well as in the northern part of theNorth Pacific. Only a few works has been made on the subject, however, the works are not always quite satisfactory. Especially on thetaxonomy of food planktons in the adjacent waters to Japan, those works
were not so correct still in the very recent investigation, and I point it in
the previous paper that the insufficient taxonomy of food planktons has
made some confusions among the studies of foods of whales. I have been
trying to correct these mistaken species as well as possible except somespecies still remained to be corrected owing to the lack of materials. As
to the Antarctic waters, Japanese investigations on whales have operated
in some 14 years after the year 1945. These accumulation of researches
have proved the results done by Discovery Committee are quite satisfactory, and there are some other reliable informations of the whales
in Antarctic that they feed on other euphausiids and planktons thanEuphausia superba, the famous main food of baleen whales in the water.
Whales Research Institute's investigation on the biology of euphausiids
is in process now, but interesting results have been obtained throughthe course. Unfortunately, Japanese investigations only cover the sum149

150

T. NEMOTO

mer seasons of both high latitudes, and I could not examine the wintersamples of both areas at all. So I would like to refer to the Discovery
works (Bargmann, 1945; Fraser, 1937 etc.) about the biology of euphausiids in the Antarctic in some points, but I would state some new consideration on the problems of the relation between foods and whales inorder to add something to the recent knowledge of baleen whales. The
distribution of euphausiids is also studied in view of feeding condition forwhales in the ocean and local characteristics of euphausiids in growthand morphological points.
With regard to the migration and movement of whales, vast numberof researches should be done before the definite conclusion is obtained.
But I would try here, to comment the particular tendencies of whale
movements related to the food of whales mainly consulting with marking
results, catch statistics and oceanographical conditions.
Oceanographical studies on whaling ground do not show so rapid accumulation of materials that I can't fully discuss the migration of whales
only from the oceanographical conditions of view. But some baleen whales
show clear distribution in accordance with the water temperature of thesea, the shape, the topography of the sea and the abundance of the foods.
For comprehension of the relation between foods and whales, it is desirable to study body characters of whales. I examined these particulars as
feeding apparatus in order to add the appropriate consideration to the foodsof whales in this paper. Body structure examination of baleen whales showinteresting fact that the preference of whales for food are affected by
the body structure, external apparatus for feeding. Some ecologicalclassification of whales is given by Eschricht (1846 in Tomilin, 1945) andKilkenthal (1892 in Tomilin, 1945), and Tomilin (1954) states further
discussions on the classifications based on morphological and biologicalcharacteristics. In this report I also try to classify baleen whales into
typical types according to said features of whale bodies and feeding.
This paper is by no means a conclusive information on the foods ofwhales, because there are many unsolved question of foods of whales
remained. And these question will be discussed again after many examination and collection of materials are obtained.
Finally, I think it is of use to summarize the species of foods of whales
in many sea regions from many previous works on the problem here inthis paper to suffice the present inquiry of knowledge of foods of baleen
whales.
ACKNOWLEDGEMENT

I wish to express my sincere thanks to Dr. Hideo Omura, the Director

FOOD OF BALEEN WHALES

151

of the Whales Research Institute in Tokyo for suggesting this investigation as well as for constant guidance in the course of the work. Dr.
Masaharu Nishiwaki of the Institute has kindly given me valuablecomments on my draft of illustrations of the whales' body charactersand kind suggestions. The present work could not have been written
without the materials supplied and facilities by my colleague Mr. Kazuo
Fujino, Mr. Seiji Ohsumi, Mr. Keiji Nasu and Mr. Tadayoshi Ichihara.
They have kindly collected my stomach samples and net collections intheir expeditions on board both in the Antarctic and in the North Pacific.
Sincere thanks are also due to Dr. Yoshiyuki Matsue, Professor of the
University of Tokyo, for his kind and constant guidance throughout thecourse especially on the plankton study.
On the whale marking problems, I am much indebted to Mr. Takehiko
Kawakami of the Fisheries Agency of the Japanese Government. He
also furnishes me some valuable informations which have not been published by himself.
Dr. Yoshio Hiyama, Professor of the University of Tokyo, has kindly
suggested me methods for analyzing the feeding apparatus and quantitiesof stomach contents and gives me constant encouragement.
I would appreciate very much the helpful discussions on euphausiids
with Mr. Yasuhiro Honjo of the Tokai Regional Fisheries Laboratory and
Mr. Yuzo Komaki of the University of Tokyo.
I am also indebted Dr. Michitaka Uda, Professor of the Tokyo University of Fisheries for his helpful comment on the oceanographic problems.
To many member of the whaling companies, I am much indebted formany facilities on board and at the landstations in Japan throughout
my examination of whales.
Finally, I thank with very best regards Mr. Jinjiro Nakai, the chief
biologist of the Tokai Regional Fisheries Laboratory for his constantguidance in the plankton study from my school days at the Universityof Tokyo.
MATERIALS

The following materials are available for the present study throughout
the course. These data and samples are collected by biologists and inspectors on board in the North Pacific and in the Antarctic waters.
In the northern part of the North Pacific, Japanese pelagic expeditions
have caught following baleen whales which have been examined.
Periods covered

Blue

Fine

Sei

Humpback

1952-1958

569

7505

804

392

T.NEMOTO

152

Methods of the examination on these baleen whales is already statedin the previous report (Nemoto, 1957). Rough classification on species
quantity and freshness are determined on boards, and a part of eachstomach contents have been preserved in formalin sea water and broughtback to our Institute.
In adjacent waters to Japan, following investigations have made collections of materials, however, those materials and observations are notso sufficient. They are all partial collections of whales caught in thewaters adjacent to Japan. These are as follows.
Okhotsk Sea, in 1952, 1953, 1957 and 1958. Stomach samples andobservations by T. Nemoto and T. Ichihara.
North east area of Japanese coast, Sanriku and Hokkaido in 1952,
1953, 1956 and 1957. Stomach samples and observations by all staffs
of the Whales Research Institute.
South west area of Japan proper, Oshima, Wakayama in 1958. Stomach
samples and observation by T. N emoto.
West Kyushu area or East China sea, in 1955, 1956 and 1957. Stomach
samples and observations by K. Mizue, K. Fujino and T. Koga.
Bonin Islands waters, in 1948, 1949, 1950 and 1951. Stomach samples
and observations by inspectors and biologists on board.
The Whales Research Institute data on the baleen whales in the
Antarctic available up to date are made of following whales.
Period covered

Blue

Fin

Sei

Humpback

1946-1958

5449

28395

1502

975

These observations include the works on the stomach contents, species,
quantity, freshness and size of the foods of whales.
The following statistics are also used in this paper so as to get the
informations on the catch and seasons of whaling.
International whaling statistics
Japanese shore whaling statistics, seasons in 1910, 1911, 1914, 1919,
1921, 1922, 1926, 1932, 1934, 1940, 1941, 1942, 1943, 1944, 1945, andthose after the year 1945.
Japanese whale marking investigations have been carried out from1949 in the North Pacific and data of discovery of marks are all provided
by courtesy of the Fisheries Agency of Japanese Government. A fulllist of these marks returned from baleen whales from 1949 to 1958 is givenin the Appendix. Some interesting informations on the Antractic whale
marking carried out by co-operations of International whale marking
program are also very useful for the consideration of movements ofwhales. The note of those prepared by Brown in the Norwegian Whaling
Gazette is helpful for consideration of the movement of whales in recent

FOOD OF BALEEN WHALES

153

years too.
The materials of body proportion and body characters obtained throughthe northern Pacific, Bonin Islands and Antarctic waters expeditions andresults at the stations are referred to make the illustrations of whales.
The skeletons and baleen plates preserved in Japanese museums are measured in needs in order to get the comprehension of feeding mechanismsof baleen whales and body characteristics.
FEEDING APPARATUS

As already well known, all of the baleen whales take their foods with
their baleen plates or whalebone. The baleen plates of whales andsome other special features about mouth part of whales differ among
each species of whales considerably. It is considered that feeding habits
and their preference for foods are much affected by the character ofbaleen plates and other features. Here, I would state the summarized
discussion on feeding apparatus of baleen whales. However, the difference among internal organs of baleen whales is omitted in following.
BALEEN

Number of baleen plates. ,Number of baleen plates of whales is illustrated in Table 1, mainly based on the data by Discovery investigations
TABLE 1. AVERAGE NUMBER OF BALEEN PLATES OF BALEEN WHALES IN ONE
SIDE IN THE NORTHERN PACIFIC AND THE ANTARCTIC WATERS
HumpBlue
Bryde's Little
Sei
Grey
Fin
Right
piked
back
North PacificRange
300-400 300-400 260-370 260-300 320-380 300-370 230-260 130-180
Approximate
360
340
330
300
280
355
245
160
mean
Antarctic and Southern hemisphere260-400* 260-480* 250-280
Range
Approximate
320
360
mean

300-410* 300-370* 220-240*
345* After the data by Discovery research since 1929,

and Japanese expeditions. There is no significant difference between
the Antarctic and North Pacific whales except Bryde's whales. The dataof the North Pacific Bryde's whales are obtained in the Bonin waters(Omura, Nishimoto & Fujino 1952), and those of southern hemispheremay be gotten in Saldana Bay, though it is not certain. Bryde's whalesin these two localities are considered really the same species, Balaenoptera edeni (Omura, 1959 p. 24), but I have no further informationon the number of Baleen plates of Bryde's whales in the southern hemisphere.

154

T.NEMOTO

Generally speaking, the large whales have more numerous number ofbaleens, but the number of baleen plates does not bear such a great
efficiency for the selection of their food as the morphological characteristics of mouth part or the features of baleen plates and fringes. It
is noted, however, that the whales belong to BALAENOPTERIDAE have many
baleen plates ranging from 250 to 400, but whales belong to BALAENIDAE
from 220 to 260, and whales belong to RHACHIANECTIDAE from 130 to180. Above results may be due to the fact that whales belong to BALAENIDAE and RHACHIANECTIDAE lack the baleen plates rows at the topof palates in the mouth. Grey whales have the smallest baleen plates
in number, which is the half of the number of baleens of BALAENOPTERIDAE
whales. Another reason for the fact may be the heavy thickness ofbaleen plates of grey whales.
Right whales lack the plates row at the top position of palate and thenumber of baleen plates are comparatively small in number comparing
with other whales. Right whales have, however, the longer plates
which may enable the whales to tilt the micro-planktons successfully by
the broad baleen filter. This morphological feature is very important
for the feeding habits of right whales which I discuss later.
Shape of baleen plates. The shape of baleen plates also differ verymuch according to the whale species. It may be classified into following
three groups.
Balaena (Eubalaena) type
Balaenoptera type
Rachianectus type
Whales belong to BALAENIDAE (Balaena and Eubalaena) have long elastic
baleen plates with fine fringes. On the other hand, BALAENOPTERIDAE
whales have comparatively short and less elastic plates. Above distinctions give us very interesting suggestions. Tomilin (1954) considers in
his short but very excellent paper, the adaptive type of baleen whales
are classified according to the thickness of bristles and flexibilities ofthe plates. The latter point flexibilities of baleen plates may be very
useful for successive filteration in the sea. Generally speaking, the longelastic baleen plates mean convenience to skim the foods in the sea water.
Because the baleen plates are filtering foods on the surface of the inner
plane consists of fine baleen fringes, and long inner edge of baleen plates
is very effective in the successive filtering. Short and wide based plateis on the other hand very useful for filtering their foods in a very shorttime, with strong stress of flesh tongue to make the water run off
through the plates remaining the mass of food in the mouth.
Baleen plates of fin whales belong to Balaenoptera type show someocal difference. Baleen plates of fin whales caught in the northern

155

FOOD O.F BALEEN WHALES

part of the North Pacific have a strong resemblance to those of the
Antarctic waters but those of fin whales caught in the East China Sea
are shorter and of more coarse texture. The difference closely related
to the one between the baleen plates of sei whales and Bryde's whales.
I would also consider this difference means some local stock existenceof fin whales in the Pacific Ocean as considered by Omura, Fujino,
Ichihara and Kimura (1958) and Ichihara (1957) as well as some different
condition of feeding environment in the waters.
Grey whales have very characteristic baleen plates. Tomilin (1954)
describes it in following way, semi-elastic thick, short and coarse. The
baleen plate of a grey whale sent by courtesy of Mr. G. C. Pike (Canada)
bears such distinctions. But to my regret, the plate may be collectedin the anterior portion of baleen plates row, so that I can't imagin theBlue (adult)

1--------------1---------'----i. ()
Fin young1----11--------1
1----11-----------1
I-i--1----1

Blue (young)Fin (adult)

Bryde's (adults, Saldana Bay)
Bryde's (adult, North Pacific)
Bryde' s (young, North -Pacific)
Littlepiked (adult)
1 Sei (adult)~
Sei (young)
J--._:_:_~----1---~
Humpback (adult)
Grey
1--W-l Right (young)
Q.J

Q.5

J.Q

1.5

l 08

Diametre (mm)Fig. 1. Diameters of baleen fringes of baleen whales measured at the center
position of baleen plates. Black belts show the ranges of dominant sizes ofbaleen fringes. Adult-whales after the sexual maturity, young-sexual immature and baleen plates are not chipped.

shape of the plates exactly but it is short. Tomilin (1954) considers
further that grey whales can dig up and probable even to plow up thesilty benthic ground with these short and thick plates. The above
function can only be made by such a characteristic baleen plates ofgrey whales.
Fringes of baleen plates. I would consider that the baleen fringes
of baleen plates have comparatively importance for the selection of theirfood or feeding habits, though I state in the previous report (Nemoto,1957) that the degree of luxuriancy or thickness of baleen fringes are
considered not to be so important to decide food species of whales.
The diameters of baleen fringes of each baleen whales are illustrated inFig. 1. As clearly shown in Fig. 1, fringes of right whales are thefinest one ranging from 0.1 to 0.2 mm in diameter, the same result as

156

T. NEMOTO

Tomilin (1954). My data are, however, based on two young specimens
caught in adjacent waters to Japan, and they are all immature adolescent
whales, fringes of which may be far finer than old whales. Usually,
the baleen fringes of the older whales are more coarse than those of
the younger whales. It is very interesting that the baleen fringes ofBryde's whales caught in the adjacent waters to Japan show the samevalue as those caught in Saldana Bay, South Africa, and Bryde's whales
are famous for their selection of fish as their food (Ruud in Peters
1938). As to the species of whales in Bonin water before 1950, it is notcertain .if all sei whales caught are Bryde's whales, but Bryde's whalescaught along the coast of Japan take fish mainly with some occasional
occurrence of euphausiids with rough baleen fringes.
Fin and blue whales have comparatively coarse baleen fringes. Of
course the younger fin and blue whales have much fine fringes when
they are sucking the milk of mother whales. The smallest baleen whale,
little piked whale has still more course baleen fringes than sei whales.
Sei whales prefer small copepods to euphausiids in the northern Pacific(Nemoto, 1957), and there is no indication that sei whales take small
euphausiids or furcilia stage of euphausiids, which is as small as
cope pods. This fact suggests something to the selection of food by sei
whales. Tomilin (1954) simply considers sei whales, by reason of its
fine baleen bristles, may also be classified as ' Microplanktonphagi '.
But I would consider further the patch of planktons also bears characteristic distinctions, and the selection of food by whales is also much influenced by them because there are many circumstances that can't be
explained by simple diagnose of baleen fringes.
Humpback whales have coarse fringes too, but not so coarse as adult
blue and fin whales. As to the baleen plates of grey whales, I have
only one example of the North Pacific. The baleen is not suitable for mystudy as it is collected from the anterior position of the baleen platesrow. However, it may be concluded by works of some scientists(Andrews, 1914 ; Tomilin, 1954), that the baleen fringes of grey whales
is very coarse when we consider the moderate body size of grey whales.
Tomilin (1954) states in the whales feed on benthic and near-benthic
organisms (chiefly amphipods), the straining apparatus develops as a very
coarse structure consisting of relatively few semi-elastic, thick, shortand coarse plates with spine-like bristles. The plate and fringes arequite different from those of BALAENIDAE, but in the feeding method
there is a little resembrance considered.
From the Fig. 1, it may be concluded whales having baleen plateswith fine fringes ranging 0.1 to 0.3 mm in diameter can take evensmall copepods of 0.5 mm or less in cephalothorax length in the scattered

FOOD OF BALEEN WHALES

157

condition in the sea. Whales having baleen plates with coarse fringes
from 0.4 to 1.8 mm can take euphausiids or other macroplanktons favourably. Of course there are some other evidence and observations thatwhales with coarse fringes take small copepods. The fact is considered
to be due to feeding habits of whales and condition of food planktons,
on which I should discuss in the latter part of this paper.
Number of baleen fringes along the edge of plates. The luxuriance ofbaleen fringes also should be investigated. At the center part of inneredge of baleen plates, the number of baleen fringes are counted for
1 cm. Fig. 2 shows the results. It is clear, from Fig. 2, that blue, fin,
Bryde's, little piked and humpback whales are classified into the samegroup. Sei and right whales into another one group, and grey whalesis third group. With comparing the diameter of baleen fringes, thenumber of baleen fringes also shows interesting fact. Little piked whales
have baleen plates with fine fringes, but number of baleen fringes areBlue
Fin
Bryde's
Littlepiked
Sei
Humpback
~

Grey
Right

ro

20

30

40

Number of baleen fringes

50

60

70

/]cm

Fig. 2. Number of baleen fringes along the edge of plates of baleen whalescaught in the north Pacific. Black belts show the ranges of main range of
number. All specimens are collected from sexually mature whale except grey
and right whales.

S1!J:all in number owing to their thin plates. Usually baleen fringes arefound in double or more in some part of inner the edge of baleen plates
in other whales. Baleen fringes of little piked whales are rarely doubled,thus making a small number of fringes. Little piked whales often takefish in many parts of the world (Omura & Sakiura, 1956). It must be dueto the small number of baleen fringes along the inner edge of baleen
plates enabling to take fish or larger macroplanktons more often thanthey feed on smaller copepods. Sei and right whales have many baleen
fringes of the finest tissue. This character is very useful for slow filteration for the scattered small planktons. The heavy luxuriance of finebaleen fringes is considered not so effective the instantaneous filteration
for big organisms in the sea water.
Gray whale has the fewest number of baleen fringes. The baleen
fringe of grey whales also the most coarse one. This mechanism

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T. NEMOTO

must be very effective for rather rapid and successive filteration of foodamong mud in the bottom of the sea as considered up to these days
(Tomilin, 1954).
Baleen plates row. The baleen plates row of baleen whales on theplates has special peculialities too. As already stated, right and grey
whales lack the baleen plates or horny spines at the top of the plates,
inner rostrum, that is left and right rows of baleen do not coalesce.
So, when they open their mouth in swimming the sea water run into
the mouth and is then filtered by baleen plates. Right whales haverather broader space between the tip of the plates rows because of therows projecting in a certain angle. If we see the head of right whales
in front, it's shape resembles to triangle form, each side of which isbaleen rows. Among BALAENOPTERIDAE whales, the left and right rows
are jointed by means of numerous horny spines located near the tip of
the plates (Tomilin, 1954). This type of baleen plates row is observed
also in Megaptera humpback whales. The projecting angle of baleen
plates in these whales are nearly the same, but sei whales' baleen plates
are considered projecting in a little like right whales.
As to the spacing of the baleen plates row, Matthews discusses the
problem in his paper on sei whales (Matthews, 1938). He compares
the space between baleen plates of sei whales with those of blue andfin whales and concludes that the spacing of sei whales are not muchless than in fin whales. I also notice as the baleen fringes of allwhales are long enough to cover the space between baleen plates, thespacing does not mean the significant difference among the feeding typesof whales. There is another evidence that the spacing of young whale
are extremly narrow comparing with the older whales, and the baleen
fringes of the former are also comparatively shorter than the latter
The filtering area in a right whale formed by baleen plates row ismuch greater than in the other whales belong to BALAENOPTERIDAE.
These shapes of the filtering area exactly show the feeding type of whales.
Blue whales represent spindle shape filtering areas, and grey whales too.
But as grey whales have arched rostrum, they may be able to use thisnarrow filtering area also in successive skimming. Right whales have,of course, broadest filtering area as shown in Fig. 3. From this illustration, the more available position is located in about two-third of allrows from the tip of the plates in blue and grey whales, and about half
to two-third in right whales.
HEAD, MOUTH AND TONGUE

The head parts of whales are also divided into three types in first

FOOD OF BALEEN WHALES

159

stage of investigation according to their structure. Blue whale type,grey whale type and right whale type are them.
Those whales belong to Balaenoptera and Megaptera have related
structures of mouth parts. The head is less than one-fourth of the total
body length. The rostrum is pointed, but it is not so narrow as rightwhales, when the mouth is closed, the rostrum fits in between the twolower jaws. The rostrum of sei whales is pointed as in the blue whales,
but from lateral view, the rostrum is slightly curved. Fraser (1949)
describes this distinction that it recalls the acurate form of BALAENIDAE,
but of course in a much less degree, and other Balaenoptera whales areclosely related to each other. The distinction of sei whales must bear themeaning of the feeding method, which has a little resemblance to that ofright whales. The beak of humpback whales is comparatively short andbroad. But mouth part is apparently Balaenoptera type and feeding
method is also considered more related to blue and fin whales.

Fig. 3. Heads of baleen whales, A-Blue whale, B-Grey whale, C-Right whale.
Shading areas show baleen plates and filtering area of each whale.

The head of right whales is triangular in shape in front of view.
The lower edge of the triangle is made of space between two lower
jaws, and top of the triangle is the arched head bone. The fore partof the skull is arched. The arching of the skull is not so pronounced
as in the Greenland whales, and when the mouth is opend, the water
may rush into the mouth because the top of the inner rostrum lackcompletely whale bones. The lower jaws and sides projected above form
an efficient scope for gathering foods as stated in Fraser (1949).
Andrews (1914) states the full description on the body characters ofgrey whales. The head of Rachianectes is very characteristic. Its
shape, in some respects, is the intermediate form between that of the
BALAENIDAE and the BALAENOPTERIDAE. The rostrum is convex dorsally, narrow and very deep, but it is neither as narrow or curved as in
the former, but is much narrower and deeper than in the latter. From
the form of skull Rhachianectes is the intermediate between of skullsof the Eubalaena and Balaenoptera.
The lateral section of mouth parts of right and Bryde's whales are160

T. NEMOTO

illustrated in Fig. 4. Left illustration of Fig. 4 shows the right whale
mouth part in scheematic condition. When the mouth is opened, thewater rush into the mouth along the tongue and filtered in successive
motion. The rather tough tongue may keep the water spread on the
inner surface of filterning area of baleen plates row. The narrowerbase and long extension of baleen plates is very available for runningout of waters from cavity of mouth in the slow swimming. As clearlyshown in the illustration, to make a successful filteration of foods inswimming, the mouth cavity is widened by opening the mouth, because
the sides become U shaped boards from the triangle shape in a closed
mouth.

Fig. 4. The lateral sections of mouth parts of baleen whales at the center positionof baleen plates rows, Left-Right whale, Right-Bryde's whale.

The section of a Bryde's whale, typical Balaenoptera type is shown in
the right of Fig 4, the fleshy tongue and ventral grooves expansion makea large cavity to take large volume of water containing the swarms offoods. After the swallowing, the water come out through the space ofbaleen plates. The left shows the condition of this filtering. The baleen
plates in the base keep the baleen very effective in a stong filteration withpressure in a short period. Fleshly tongue is able to scrap all the remaining of food on the surface of coarse baleen fringes successively.
VENTRAL GROOVESThe number of ventral grooves also differ among baleen whale species,
and some of baleen whales lack absolutely these ventral grooves. Greenland and right whales have no ventral grooves. Right whales have noneof these ventral furrows like grey whales (Omura, 1958). Along the throat
and belly part of the body, whales belong to BALAENIDAE have none of

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161

throat furrows but grey whales have some thoroat furrows. These throat
furrows are comparatively deep and usually two of them are longer
than others. And as Andrews (1914) described, the most of grey whales
have only two furrows. The function of these furrows is considered tobear some significants to increase the throat capacity in also grey whales,
it bears a close connection to take foods or the air (Andrews, 1914).
Humpback whales have fewer ventral grooves than other whales of
BALAENOPTERIDAE. And the width of each ventral grooves is wider thanthe other whales, but the extension of grooves reach the position of 58
percent of the body length from the head in average, and there is nodifference from other BALAENOPTERIDAE whales. As shown in Table 2,
the number of ventral grooves is the most numerous in blue whales
and fin whales come next. According to the data by Omura, Nishimoto
TABLE 2. NUMBER AND EXTENSION OF VENTRAL GROOVES OFBALEEN WHALES IN THE NORTHERN PACIFIC

Megaptera

Balaenoptera whales
Ventral groove
extension
Approximate no. ofventral grooves
Range of number

Blue

Fin

58%

55%

Bryde's Little piked Sei

58%

47%
62

80

64

53

64-94

50-86

40-69

45%

Humpback

58%

52

22

40-69

18-24

& Fujino (1952) there is little difference in number between Bryde's
and sei whales in the north Pacific. The number of ventral grooves has
been considered as a taxonomic distinction of Bryde's whales from sei
whales, so it needs more examination on the point. I would consider
the number of ventral grooves of Bryde's whales is more numerous
than those of sei whales according to my recent observation.
The extension of ventral. grooves also differ among the each whale
species. Table 2 shows these values, and blue and Bryde's whales are
considered to have the most long extension of ventral grooves in general.
On the other hand, sei and little piked whales have comparatively
shorter extension of ventral grooves among whales of Balaerwptera.
The ventral grooves of sei whales do not rea:ch umbilicus, and sei whales
have only such a character in Balaenopterids. The shorter extensionof ventral grooves suggests something about the feeding of sei whales.
Sei whales which have the shorter extensions of ventral grooves may
have less convenience to gulp the water, or less throat and mouth
capacity when they are feeding. Sei whales often skim their foodsin the surface of the water is partly due to above reason, but I havenever noticed if the little piked whales usually take their foods byskimming of the water containing the foods scattered condition.

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T. NEMOTO

Above stated discussions are all indicating the ' type ' of whales in
feeding from the point of view of body structures. I would summarize
following the each subject. The Table shows four type of body structures for feeding. Those are, Blue whale, Sei whale, Grey whale andRight whale types.
The most important point may be the type of sei whales. Sei whales
are considered a little different from other Blue whale type whales,
which I describe before. These feeding apparatus type should be examined again by many stand points, feeding method, selection of food etc.
WhalespeciesBlue
Fin
Bryde's
Little piked
Sei
Humpback
Grey
Right

Baleen plates
Shape

FringeRow

Head, mouth
and tongue

Ventralgrooves

Apparatus
type

Blue

Blue

Blue

Blue

Blue

Blue

"

"
"

"
"
"
"
"
Grey

"

"

"
Sei (Blue)

"
Sei

Blue
Grey
Right

Hump.
Grey
Right

~-~~---~H""
Sei (Right)

"

Blue
Grey
Right

ff

Grey
Right

Right

"

"

ff

ff

"

Sei (Blue)
Blue
Grey
Right

I have no exact information on the body characters of Greenland whales,
however, they are apparently considered to belong to Right whale type.
FOOD OF THE BALEEN WHALES IN THE ANT ARCTIC WATERS
SPECIES OF FOODS

The reason why so many baleen whales swarm in the Antractic watersin summer of the southern hemisphere is up to now attributed to thevast propagation of Euphausia superba, which is the main food forthem. Many works of foreign and our own Japanese scientists provethat the almost all baleen whales feed on those krill E. superba(Mackintosh & Wheeler, 1929; Mizue & Murata, 1951 etc.). In my firstcruise to the Antarctic waters from 1954 to 1955, I found none but E.
superba in the stomachs of baleen whales in the Antarctic area IV.
Recent investigations, however, have collected some other very interesting
examples of stomach contents though I lack samples of stomach contents
in November and December owing to the whaling regulations. Oneof those food, Thysanoessa macrura is already described in a previous
report (Nemoto & Nasu, 1958). In the Antarctic whaling grounds VI
and I, which has been sanctuaries before 1955 whaling operation, Thysanoessa macrura, another kind of euphausiids, is considered to bearsignificans as a foods of baleen whales (Nemoto & Nasu, 1958).
Besides above two euphausiids, the plankton amphipod, Parathemisto

FOOD OF BALEEN WHALES

163

gaudichaudi is found as a food of sei whales in the Antarctic. There
are still other planktons which probably become foods of baleen whales.
Peters (1955) describes these planktons.
The recent Japanese collections of stomach samples show following
occurrences of Euphausia superba, Thysanoessa macrura and Parathemisto gaudichaudi in the each Antarctic whaling area. As described in
the remark of Table 4, the observations and collection of P. gaudichaudi
are not sufficient, but it has mainly been found in areas V and IV.
TABLE 3. OCCURRENCE* OF EUPHAUSIA SUPERBA, THYSANOESSAMACRURA AND PARATHEMISTO GAUDICHAUDI IN THE
COLLECTED SAMPLES OF THE ANT ARCTIC BALEENWHALES CAUGHT BY JAPANESE EXPEDITIONSIN 1955, 1956, 1957 AND 1958
Area

Species of foods---------~

III- - - - -

v

IV

VI

Euphausia superba
69
11
311
402
318
Thysanoessa macrura
15
2
2
20
Parathemisto gaudichaudi
14* Samples containing T. macrura besides E. superba are included in thecolumn of T. macrura, and sampling for P. gaudichaudi is not sufficient.
TABLE 4. OCCURRENCES OF ONE AND TWO YEARS' GROUPS OF EUPHAUSIA
SUPERBA IN THE STOMACH OF BLUE, FIN, SEI AND HUMPBACKWHALES CAUGHT BY JAPANESE WHALING EXPEDITION,
CHIEFLY IN AREA V AND IV IN 1958
Euphausiids group
2 years group
after· copulation
before copulation
1 year group
MixtureFebruary

January~-~-~'-...._

March_,---'~

~----

lst

2nd

3rd

lst

2nd

3rd

lst

2nd

29

58

52
2
25
16*

7

4

36
2

29
7
3
2*

11

26
7

2
1
27
4

8
2*

* Euphausia superba of two years group not copulated.

From said results and description by Marr (1956), Peters (1955), I may
describe following planktons of the foods of Antarctic baleen whales.
Euphausia superba
Euphausia crystarollophyas
Thysanoessa vicina
Thysanoessa macrura
Calanus propinquus
Calanus acutus
Parathemisto gaudichaudi
According to Japanese observation, the Antarctic Calanus has neverbeen observed in the stomachs of whales in dominant quantity. But
these copepods may play some part of a food for sei whales, because
sei whales can skim the scattered food like plankton amphipods in the

164

T. NEMOTO

sea (Nemoto, 1957). Euphausia crystarollophias is considered Antarctic
species, on which Marr (1956) describes that it becomes a food for blue
and little piked whales in the high Antarctic such as Ross Sea. Thysanoessa vicina has not be confidently known as a food of baleen
whales in the Antarctic but in the whaling area I, the occurrence inthe far off waters from the pack ice is probable from the distribution.
Euphausia superba is the most important food for the Antarctic
baleen whales as considered up to the present. E. superba is a by-ennial
euphausiid, and the investigation usually finds 1 year or 2 years groups inthe stomachs of whales. I would use here the term, 0 year group, 1
year group and 2 years group, after the classification by Ruud (1932).
In this case, 0 year group means the E. superba from egg to adolescent
within a year living, 1 year group after 1 year making comparatively
rapid growth and 2 years living, 2 years group after 2 years living. I
find E. superba of 1 year or 2 years group in the stomachs of baleen whales
in general, and 0 year group has never been noticed by my investigation. Recent observations of above classifications are shown in Table 4.
TABLE 5. OCCURRENCES OF ONE AND TWO YEARS' GROUP OF
EUPHAUSIA SUPERBA IN THE COLLECTED SAMPLES
OF WHALES' STOMACH IN 1957
Euphausiids group
2 years group
after copulation
before copulation
1 year group
MixtureJanuary

February

~~

~

March
_,,.--~~--"'-

lst

2nd

3rd

lst

2nd

3rd

lst

2nd

5

10
1
12
4

14

36

25

17

7

6
4

15
3

16
1
34
4

57
5

21
3

16
3

3

I get these observations in whaling area IV and V mainly, but the
samples in 1957 had been collected from the whaling area I and VI.
It is clear from these Table 4 and 5, that 2 years group is comparatively
dominant in the earlier decades and 1 year group in the later decades.
Of course as shown in Table 4, I observed many occurrences of 2 years
group in the late decades of March in the whaling ground V in 1953,
which is also illustrated in the next figure of Fig. 5. Generally speaking,E. superba of 2 years group is the better food for baleen whales than
1 year group of euphausiids. This has fewer oil contents than that,and further there are another reasons such as the beha vior of the dirnnal
migration. The adult 2 years group E. superba swarms heavyly in thesurface waters to take their foods and copulate. The swarms of theseE. superba are mainly restricted in the surface waters within the
10 meter depth (Marr, 1957). This condition is very favourable forbaleen whales to feed. It is also very interesting that the most of 2 years

165

FOOD OF BALEEN WHALES

group of E. superba has copuleted. There are, on the other hand,some occurrences of 2 years group E. superba in 3rd decade of January
in 1958. These 2 years group E. superba swarms are, however, foundalong the pack ice where the growth and spawning of euphausiids arecomparatively slower or later than those in the off waters. A example
of distribution of 1 year and 2 years group is given in Fig. 5, which isdrawn after the observation in 1958. This figure gives exact distribution of the two groups. The detailed explanation should be referred to the

.~v
•A

...

•• w .. -..wl<J(Jlll

6.M
I 5£

~x

r-

55

Fig. 5. A example of the distributions of pack ice line and foods of baleen whalesin the stomachs of whales caught by Japanese operations in the Antractic in 1958.
Open circles-I year group of Euphausia superba. Solid circle-2 years groupin January and February. Open triangle-I year group of E. superba in March.
Solid triangle-2 years group of E. superba in March. Cross-Parathemisto
gaudichaudi. Open square Thysanoessa macrura. Alphabet show the whaling
grounds and number and alphabet show the pack ice line of the date. }-waters
where no swarm of E. superba is obsered and no whale caught.

explanation, but in short it may summarized as follows. At first in theearlier whaling operation, fin whales feed on the 2 years group E.
superba, which is copulating, distribute in the off waters 200 miles fromthe pack ice as shown in Fig. 5. The feeding ground consists of 2 years
group of E. superba falls down in February which is due to the subsiding of gravid females of E. superba to spawn in deeper waters, as
Bergmann (1945) discussed in her paper. But the feeding grounds of

166

T. NEMOTO

1 year group flowerish still in the late of the summer season of the
Antarctic. This fact does not deny the another evidence that the 2, years groups of E. superba are found throughout the season. But inthis case successive appearance of 2 years group of E. superba is notdue to the same group of E. superba occurrence. Different E. superba
may come up successively into the surface waters with the retreat ofthe pack ice.
According to Ruud (1932), the Nowegian whalers well know 'Blue
whale krill' and 'Fin whale krill' meaning 1 year and 2 years groupsof E. superba respectively. Peters (1955) states, these early stages ofthe smaller E. superba occur dominantly at the beginning of the whaling
season from November to December. But my collections do not showsuch tendencies. I am not sure which is right, because my collection
only started from 1954, before which no available observation and collections of systematic research had been made on the stomach contents.
So I lack completely these earlier season samples. But the explanation
may be given by local characters of the Antarctic ocean. Except somewaters along the Ross sea, Japanese whaling has covered usually theground along the pack ice. On the other hand, the foreign Antarctic
operations sometimes have been conducting in the far off waters from thepack ice, where the drift of the euphausiids from the southern waters isobserved. The circulation of Weddle sea current may bring these younger
stage euphausiids to the ground, or 2 years group of small size appears
in the earlier seasons along the pack ice before retreating to the south.
Thus the foreign scientists found the small sfae euphausiids. According
to the Peters (1955, Fig. 3-6), the size of E. superba in the off waters
are comparatively larger than that in the waters along the ice, or thesmall size groups, that is 20 to 30 mm in length, are more abundant in
the latter areas than the former said waters. On the other hand, heconsiders the small E. superba is dominant in the earlier season. Blue
whales, the earlier comer to the Antarctic waters than fin whales, taketheir foods along the pack ice where the euphausiids of 20 to 30 mm
in length are mostly abundant. Fin whales feed, on the other hand,E. superba of 30-40 mm in length favorably. In my collections of 1957
and 1958, the dominant size groups belong to the larger body length
groups as shown in Fig. 6. From 15 mm to 40 or 45 mm length groupis considered to be 1 year group in 1957 and from 45 to 50 mm groups is 2
years group. As above measuring is given by the value from the tipof telson, these value may be a little different from the figures given
by Peters (1955). Anyway, the occurrences of 1 year group and 2
years group are about half and half of the total in my collections.
Bargmann (1945) measured the diameter of eggs of gravid female, and167

FOOD OF BALEEN WHALES

get the average of 0.55 mm, and my work also coinside with the result.
The heavy gravid female (stage 7 by Bargmann, 1945 p. 115 or Ruudstage 3-4) is found in the collections of stomach samples in January
and February. These stage of maturities of E. superba also show thehalf in total in consideration of swarms of euphausiids. Whether theswarms of E. superba in the stomach of whales copulated or not isalready given in the Tables 4 and 5, and the copulation date is late one
or not is shown by the condition of spermatophores in thelycum (Bargmann, 1945). The half of copulated swarms of E. superba out of 15
samples show the fact because there still remains the sparm-mass. This
discrimination is very interesting in order to examine the condition ofswarms of euphausiids as stated above. From the 14 years observations, the copulated females are dominant from January to Februarysuggesting that the pairing of E. superba occur mostly in this seasonof a year. Bargmann (1945) already refers to the point and describes
40
Q)

Ol

1958

1957

30

0

~ 20
u

Q;

a..

10

0

1s- 20- 25- 30- 35- 40- 45- so-

15- 20- 25- 30- 35- 40- 45- so-Body length (mm)Fig. 6. The size distribution of dominant group of Euphausia superba observed and collected by Japanese whaling expeditions is 1957 and 1958 in the
Antarctic waters in the whaling area IV, V. VI. and I.

the peak season of pairing comes in February when the greatest number
is found, and the gravid females become scarce in the surface waters
to spawn in the deeper waters. So before subsiding, the gravid E.
superba must be the most fovorable food for baleen whales, the peakseason of which is the same as the peak of the migration of baleen
whales in the Antractic waters. I have also noticed the swarms of E.
superba consisted of mostly dominant males in 2 stomachs of whales
and females with vacant ovary. One may think they are swarms ofeuphausiids after spawning.
The egg and the younger larva, from nauphi to furcilia, have neverbeen observed in the stomachs of baleen whales. The smallest E.
superba is about 20 mm adolescent, which is nearly the same length
as previous paper on the E. superba in the Antarctic (Marr, 1956).
The sex ratio of E. superba differs from those of the North Pacificeuphausiids. As described in a previous report 'cNemoto, 1957), males

~.

168

NEMOTOare less in number among the Northern Pacific Thysanoessa. On thecontrary to this fact, male E. superba is not less dominant in the swarm
collected from the stomach of whales. As to the body length of E.
superba, males are a little larger than females in general. This fact
is also different from that of the North Pacific Thysanoessa euphausiids(Nemoto, 1957, Fig. 20). The female of Thysanoessa euphausiids exceeds
the males in body length in the northern Pacific and in the Antarctic.
Thysanoessa macrura. Next to Euphausia superba T. macrura ismostly common in the Antarctic waters. It is also described as a staple
food of baleen whales in the Antarctic waters (Nemoto & Nasu, 1958).
T. macrura distributes more abundantly in the whaling area VI and I, only
few samples of which are observed in the whaling areas IV and V. In

40
Q)

u

~ 30
80
l'.l, 20

lJ
~

t'..

10

0
40°E

100°E

140°E

180°

140°W

100°W

Fig. 7. Occurrences of Thysanoessa macrura in the stomachs of Antarctic
baleen whales in 1956, 1957 and 1958. Open circles shows insufficient observations in number.

1958 whaling season, I examined euphausiids in the stomachs of whales
chiefly on the samples of whaling areas IV and V, but only 2 samplesof T. macrura are found in the area V and none in the area IV. From
three years investigations from 1955, I get a percentage occurrence ofT. macrura in the Antarctic whaling area from 40° east to 80° west
longitudes. As clearly given in Fig. 7, T. macrura shows dominantappearance in the waters from 140° west to 80° west longitudes.
Another dominant occurrence is observed in the west waters from 40°
east to 60° east longitudes, but it must be due to the insufficiency ofcollections. T. macrura swarms in the warmer waters than E. superba
and in off waters from the pack ice (Nemoto & Nasu, 1958), their mainoccurrences are observed in the last decade of January and the first
decade of February, and baleen whales are considered to concentrate

FOOD OF BALEEN WHALES

169

to take T. macrura in the off waters at these periods of the season in
the said waters.
T. macrura, showing the dominant appearance in the stomachs ofwhales, must make large swarms in the sea. In my collections, however,no copulated females appear. It is very difficult to explain if the pairing
season of T. macrura is earlier or later than that of E. superba,
because I lack the complete series of T. macrura throughout the whaling
season. From their distributional occurrences in the whales' stomachs,
it is considered that the spawning time and grounds differ a little fromthose of E. superba. Ruud (1931) discusses, however, spawning of T.
macrura may begun October and continue to February. Rustadt (1930)
also finds that the youngest stage of T. macrura are more common
among or near the ice. Rustadt (1930) and Ruud (1932) suppose fromabove observations T. macrura has the same spawning ground andseason as E. superba. T. macrura is considered to distribute in waters
with temperature about 0°C (Ruud, 1932, Nemoto & Nasu, 1958), andthe temperature distributes a little apart from the pack ice. So I
would consider the distribution and spawning season differ from thoseof E. superba according to above Japanese observation.
As it is pointed by Rustadt (1930) and Baker (1954), in the younger
stages, it is difficult to separate T. macrura from T. vicina. Still collected samples at my hand are considered all T. macrura by external
characters. But 'in the far off waters especially in the whaling area 1,
it is probable that T. vicina may be a food for whales.
Besides the dominant appearances of T. macrura, the mixed occurrence of T. macrura with E. superba should be examined. Because
the stomach samples of the Antarctic baleen whales have been classified
according to the size of euphausiids in the Discovery method. 'X' in
the classification of stomach contents means the mixture of the larger
and smaller sized euphausiids. It may sound strange, I have a evidence that some routine observations might cause mistaken description
as to the species of euphausiids. Jt is probable the small T. macrura
has not been noticed by routine workers only describing sizes of euphausiids. In this point, to my regret, I can't refer to any former works
especially carried out in Japanese investigations.
Euphausia crystallorophias. The Antarctic neritic species, E. crystallorophias has not been collected by Japanese investigations. However,Marr (1956, 1957) notes that in the high Antarctic, Ross sea, someblue and little piked whales may take E. crystallorophias as theirfood, and blue and fin whales fed on E. crystallorophias in the highAntactic caught by A. Larsen expedition in 1923-24 season because
along the Ross sea barrier, the patch of E. crystallorophias were oh-

170

T. NEMOTO

served very often (John, 1936).
Parathemisto gaudichaudi. P. gaudicha·udi has only been described asa local plankton in the Antarctic waters, and it bears no significance forthe baleen whales as their foods (Mackintosh & Wheeler, 1929). Also
by Japanese investigations, the dominant occurrence has never been
noticed up to recent time. (Mizue & Murate, 1951 etc.). P. gaudichaudi
has only been found among the euphausiids in the whales' stomach infew number. It has been considered insignificant diet for whales(Mackintosh, 1942). But in 1958, Japanese whaling expeditions have taken
considerable number of sei whales in the Pacific sector of the Antarctic,
when I was aboard on a factory ship to examine the whales as mysecond cruise to the Antarctic ocean. Some 1500 sei whales are caught
in the late season of March, which is a very interesting phenomena
since the Antarctic pelagic whaling opened. Other blue and fin whales
become comparatively scarce at that time and sei whales feeding on P.
gaudichaudi besides E. superba are found in the off waters from theTABLE 6.

Whale
species
Blue
Fin
Sei

OCCURRENCE AND QUANTITY OF E. SUPERBA AND PARATHEMISTOGAUDICHAUDI IN A CERTAIN AREA OF ANTARCTIC
AREA V, MARCH IN 1958

P. gaudichaudi

E. superba,-·--~----

--

None

--~---·/"

R

rrr

rr

r

1

5
2

14
1

6
1

R

rrr

5

rr

4

r

5

2
88
24

pack ice. P. gaudichaudi is exclusively found in stomachs of 14 sei
whales. Many sei whales with vacant stomachs also have darker excrement in their gut, showing that they had fed on P. gaudichaudi before
their being shot. Because the excrements of E. superba origin and P.
gaudichandi h~ve different colour and remaines respectively. At the sametime, fin whales caught in these areas have no trace of P. gaudichaudi
but the stomach contents of E. superba. This is the first descriptionof P. gaudichaudi as a staple food of sei whales in the Antarctic, suggests sei whales skim the water to take scattered patch of P. gaudichaudi.
Table 8 gives us the same data of feeding condition of whales in acertain period in March in 1958. Only sei whales take P. gaudichaudi,
and all fin whales feed on E. superba. In other time of the season,
the occurrence of the amphipoda has not been observed. But I would
consider that from the abundance of sei whales it is abundant in thewarmer waters of the Antractic. In the near waters of the Antarctic
convergence, sei whales must have been feeding on the amphipods orsome other organisms scattered in the sea. Foxton (1956) well describes

FOOD OF BALEEN WHALES

171

the total volume of zooplanktons from the north to the south crossing
the Antarctic convergence. The zooplankton concentration is observedin a region 0-200 miles south of the convergence. Of course, thisvalue is calculated without E. superba near the pack line, the former
waters must be one of the probable feeding grounds of sei whales consisting of scattered plankton such as P. gaudichaudi.
The concentration of Japanese catch of sei whales is located in thewaters of 140° east longitude and 140° west to 160° west longitudes.
In the former area, the peak of the occurrence of P. gaudichaudi is
described by Baker (1954).
Fish. Fish in the stomachs of baleen whales in the Antarctic waters
are appearently considered incident occurrences. There is no finding of fishin the stomach of baleen whales dominantly but a few specimens alongwith euphausiids. They bear no significant meaning for whales feeding,only being swallowed by whales with other food planktons. Those fishes
also often swallow E. superba of ten or more individuals in their stomachs.
Only the slender fish Notolepi coatsi Dollo has often been observed.
Those fish persure krills in the surface of the water, and one can see
the fish chasing E. superba. The fish is called as 'icy long nose fish'by Japanese whalers. Another fish belonging Myctophidae are sometimes
observed in the stomachs of baleen whales.
In 1955, I found a curious fish from the stomach of a fin whale in
the whaling area IV, which afterwards is named Xenocyttus ne1notoi
by Abe (Abe, 1957). This fish was found along with numerous E. superba,
but the fish fed exclusively on the copepods, contrary to the expectation.
As a conclusion from 14 years observation, it is safe to say there is
no important fish for baleen whales as their food in the Antarctic.
QUANTITY OF STOMACH CONTENTS

As a routine work, the stomach contents are classified into four groups
according to their quantities (Nemoto, 1957). It is, however, made by the
naked eyes and exact weighing has not been obtained. So it gives us only
a comprehension of the feeding condition. Figures 8 and 9 show the stomach quantity of each species. Generally speaking, blue whales show
higher feeding percentage than fin and sei whales, and there is nodifference between sei and fin whales. Humpback whales take their foodusually in their stomach, thus the percentage of vacant stomachs is less in
number, or show higher percentage of feeding than blue and fin whales.
In other localities, humpback whales also show higher percentage of
feeding food. Mackintosh (1942) already describes full stomachs are foundin 80% of blue whales, 50-60% of fin whales and 90% of humpback

172

T. NEMOTO

whales according to the observations by Major Spencer. When I compare above figures with Japanese result, the latter shows lower value
than the former by Mackintosh. I have some probable explanation tothis difference. To begin with, in the modern whaling, the prolong
chasing of whales may cause vacant whale's stomachs, because thelonger the chasing is done, the more the vacant stomachs of whalescaught we find (Nemoto, 1957). Really the diesel motor equipped catcher
boat chases whales in higher speed for longer hours in the recent operations. In second, the abundance of euphausiids may differ in each localities
50

Sei

Blue

50

Humpback

40

Blue

Sei

Humpback

40

" 30
g
c

30

"t' 20
"

20

0..

10

10

0

0
1958

1957

Fig. 8. Quantity of stomach contents of blue, sei and humpback whalesin the Antarctic waters in 1957 and 1958. White-vacant, Lateral-few,
Straight-moderate, Oblique-rich, Black-full.
Ill

IV

v

VI
VI

50

50
40

40

" 30
~
~" 20

1958

1957
30
20

10

10

0

0

Fig. 9. Quantity of stomach contents of fin whales in the Antarctic waters
in 1957 and 1958. Roman numeric shows Antarctic whaling secters.
White-vacant, Lateral-few, Straight-moderate, Oblique-rich, Blackfull.

of the Antarctic waters or owing to the fluctuations in each year. Japanese investigations carried out in 1940 and 1941 give also higher percentage
than recent results.
Based on the results of 1957 and 1958, the feeding percentage of fin
whales show the local differences among the whaling sectors of the
Antarctic waters. Comparatively many fin whales take their food in
the whaling ground VI. On the other hand, over 60% of the stomachs
of fin whales are empty in the whaling grounds IV and V. Although
no evidence is obtained as to the exact abundance of food in the sea fromabove figures, the result may be an indication that there are different

173

FOOD OF BALEEN WHALES

abundance of euphausiids in each Antarctic area. Peters (1955) also
describes that pelagically caught whales had more empty stomachs, ascompared with the whales off South Georgia. Mackintosh states (1942),
there was some indication that empty stomachs may be found a little
more often in the early and late part of the season. I also think it isprobable if a certain area is confined to examine, because whales follow
the waters where their foods are abundant, but it is rather difficult
to get the exact feeding percentage in seasonal comparison. Still, it isevident that the peak of Euphausia occurrence is observed in the midsummer of the Antarctic when the feeding percentage must show thehigher value throughout the season.
THE GROWTH OF EUPHAUSlA SUPERBA

Ruud (1939) and Bargmann (1945) state full discussions of growth of E.
superba. By their discussions, E. superba attains the sexual maturity

~
E

40

40

69S

...5
_c

Tu
~

30

30

__ .... .,,,.-~""·

>-

-0
0

• R

ro

. 20

20
A

B

Fig. 10. Growth of Euphausia superba of 1 year group along the pack line of the
Antarctic. A-The latitudes are nearly the same but the longitudes are different.
B-longitudes are the same but latitudes are different. R-see R of Fig. 5.

stage after two years. It makes comparatively rapid progress in earlier
and slower progress in later stages in general. The growth of E.
superba is considered to be different among each locality of the areasof the Antarctic. Bargmann (1954) already describe the very heterogenous
population of E. superba owing to the prolonged spawning seasons.
Generally speaking, E. superba in the off waters where the pack ice
melt in the earlier date of the Antarctic summer makes more rapid
growth at the same season of a year. As shown in Fig. 10, 1 year groupof E. superba in 155° west longitude area shows an advance of growthT.NEMOTO

174

in 20 mm, or the group of E. superba in 146° west longitude shows smaller
body length at the same time of the Antarctic summer. Going more east
waters, E. superba again recovers its body length in the waters of 126°
west longitude. Among the every group of E. superba, exact. divisionlines are considered, which is directly considered to be due to thedifferent spawning time in a year.
On the other hand, this fact is partly due to the melting time of packice when the rapid propagation of foods of E. superba diatoms andsome other zoo organisms have begun. The foods of E. superba aredescribed by Barkley (1940). According to his work the main food isa diatom Fragilariopsis antarctica and my recent investigation supports

-~-

50

40
-"

°' 30

~

'

>-

Ll
0

"' 20
10

M

M

s

N

M

M

s

N

Fig. 11. Growth curve of Euphausia superba along the pack ice of the Antarctic
waters, Solid line-female, Broken line-male, Shading area shows main Japanesecollections.

the fact. And in a favorable condition diatom will propagate so rapidly
as to support the vast growth of E. superba of 1 year group. Fromthe body length of 20 mm to 45 mm, the body weight of E. superba
becomes three times as big as the smaller stage of 20 mm. So thedifferent spawning time of each group should be considered as one
stable reason of different growth of E. superba in each locality. In
1958, I get two groups of E. superba which are swallowed by whalesat the same longitude but the latitudes of the positions are 69° and 72°
south latitude at 151° west longitude.
The pack ice at 69° south latitude melted away in the middle ofJanuary, but the pack ice at 72° south latitude melt in 30th of January.
There exists 15 days delay in melting of the ice. The body length of

FOOD OF BALEEN WHALES

175

E. superba in the former waters shows about 10 mm advance, the difference of which may be too big for the lapse of 15 days. But the figure
gives us evidence of difference in growth of E. superba in each locality.
If I consider the rather rapid growth curve of E. superba, as shown in
A of Fig. 10, it is probable that E. superba makes 10 mm growth in 15
days. Thus the difference in growth according to the food supply isalso evident.
The marked decrease during the winter months (Fraser, 1936) is attributed to scarcity of materials by Bargmann (1945). But I would consider from the growth of 0 and 1 year group of E. superba, the wintergrowth should show more decrease than that by Bargmann, because
I

I
I

].4

I
I

1.2

I

I

,......_

I-3 1.0I
I..:cOl

I

o.s
'iii

3:
>-0

I

I

o.6

0

co

0.4
0.2
10

Body length (mm)Fig. 12. Body weight and body length relation of EuphauB'ia superba
in the Antarctic waters along the pack ice, the sudden increase from
45 mm in body weight show a illustration of expansion and growthof ovary of euphausiids.

along the pack ice the growth of E. superba is very rapid after themelting of ice covering the surface of swarming area as shown in Fig.
10. As the maximum length of female E. superba is about 55 mm, andif they do not stop the rapid growth in the winter season, it goes too
far. With considering above points, I draw the growth curve of E.
superba along the pack ice in Fig. 11, which may have some resemblance
to that of Bargmann (1945).
The relation between body length and body weight of E. superba isillustrated in Fig. 12. This figure clearly shows the tremendous growthof E. superba in the weight in the latter part of its life. Especiallyafter copulating, the ovary of E. superba which contains more fat expand
remarkably, thus the increasing growth curve is obtained. Peters (1955)

T. NEMOTO

176

also considers the larger whale shrimps (2 years group of E. superba)
are the better food resource for the baleen whales than the small stageof E. superba owing to their fat content. The smallest copulated E.
superba is about 35 mm in length, which is, however, not real signalof coming maturity. The weight of it is not so heavy that it is considered to be only a external phenomena, because maturity of a female
euphausiid can be measured by the body weight of it. The increase ofweight in the later stage of E. superba is well given by the development of the egg in ovary.
·
The relation between body length and weight of euphausiids in the
different localities in the North Pacific is given by Ponomareva (1954),
but with regard to E. superba in the Antarctic waters, there is no
significant difference among the relation in each locality.
FOOD OF THE BALEEN WHALES IN THE NORTH PACIFICNORTHERN PART OF THE NORTH PACIFIC

Stomach contents of whales
The foods of baleen whales in the northern part of the North Pacificbased on the observations by the year 1956 are summarized in the previTABLE 7. STOMACH CONTENTS OF BALEEN WHALES CAUGHT
BY JAPANESE WHALING FLEETS FROM 1952 TO 1958 IN
THE NORTHERN PART OF THE NORTH PACIFIC
Whale species
Kinds of stomach
contents
Euphausiids
Eu. & Copepods
Eu. & Squids
Eu. & Fish
Eu., Fish & Squids
Eu., Fish & Co.
Cope pods
Co., & Squids
Fish
Fish & Squids
SquidsEmpty
No. of Stomachs examined
Not examined

Blue

Fin

Sei

Humpback

266
2

2222
137
6
8
1
7
965
3
247

10
1

203
2
1
11

286
5
8
1
15
473
799
5

1

298
566
3

22
3868
7486
19

53
1
120
392

ous report (Nemoto, 1957). The successive whaling operations havecovered broader areas than the former operations. In 1957 and 1958,
the expeditions have covered the off waters of Anadyr gulf, the most
northern part of Bering sea, Navarin cape, Anadyr gulf and Olutorskiy

FOOD OF BALEEN WHALES

177

Bay. From the two years' operations, I can get more detailed features offood of baleen whales and distribution of whales. Stomach contents ofbaleen whales caught during 1952 to 1958 are illustrated in Table 7. It isclear from the Table 7, that blue whales feed on only euphausiids,
but 2 occasions. Some 140 blue whales caught in 1957 and 1958 takenothing but euphausiids like the previous report. Fin whales caught
in the both years also feed on mainly euphausiids and copepods as previous
year. Still considerably many fin whales feed on fish swarms in the years.
Some 244 fin whales take fish in the North part of Bering sea, and fish isimportant as a food of fin whales. In the previous report, I consider

BERING \SEA"····""-. .:;-.. • PribiLofis,,KomandoY.IS.

.":#:,1''""'/:: .. ···,.Near Is.
0!#·, Paramushirl.
'o
160°£

Fig. 13.

·• ••f.~~,.

SS~,._,.p- ........... fOi-\S'And~eanof Is.

sp

PACIFIC OCEAN
170°£

180'

I

o·w

160 w

Whaling ground in the northern part of the North Pacific.

that fish is only a makeshift food for fin whales. But I would think
here fish is a main food for fin whales in the north waters of Beringsea above 58° north latitudes where the whaling operation had notoperated before 1957. Sei whales show the same tendency as previous
investigations. Calanoid copepods are the favourite foods of sei whales
with other occurrences of euphausiids, fish and squids. The main foodof humpback whales are euphausiids and fish, which is also the same
result as the previous investigations.
Thus the foods of baleen whales in the northern part of the North
Pacific, adjacent waters to Aleutian Islands and Bering sea are describedas follows.
euphausiids
Blue whale
euphausiids, copepods, and swarming fish
Fin whalecope pods
Sei whale

178

T. NEMOTO

Humpback whale euphausiids, and swarming fish
Besides above listed foods, squids are considered a makeshift food forfin and sei whales. From 1952, 22 fin whales and 15 sei whales have
fed on squids and 7 fin whales and 6 sei whales have taken the mixtureof squid and other organisms. There is a evidence that one main foodof sei whales in the adjacent waters to Japan is squids, but it is not
so important in the northern part of the North Pacific.
Species of food
Euphausiids. The previous studies on euphausiids are summarized in
the report (Nemoto, 1957, p. 44-52), and I add here further knowledge on
the problem. Following 5 species belonging to EUPHAUSIACEA have beencollected through the investigation. Among them, Thysanoessa raschii
is found in 1957 as a first record in the northern part of the Beringsea, and the successive collection in 1958 proves this.
One Euphausia and four Thysanoessa observed are follows.
Euphausia paciffoa Hansen,
Thysanoessa inermis (Krqiyer)
Thysanoessa longipes Brandt, Thysanoessa spinifera Holmes
Thysanoessa raschii Sars,
The distribution and occurrence of above species in the northern partof the North Pacific are already stated to some extent in the previous
paper (Nemoto, 1957).
TABLE 8. OCCURRENCES OF PLANKTONS IN THE COLLECTED SAMPLESOF STOMACH CONTENTS OF WHALES IN THE NORTHERNPART OF THE NORTH PACIFIC SINCE 1954
Whale species
Species ofplankton
Euphausiids
E. pacifica
T. inermis
T. longipes
T. spinifera
T. raschii
Cope pods
C. cristatus
C. plumchrus
M. lucens

Blue

Fin

Sei

.-J--..

~.-J--..

3
8
5

(3) *
(8)
(7)
(1)

(1)

12
95
86
2
7

(25)
(123)
(121)
(17)
(7)

116
11
1

(140)
(20)
(1)

9
1

(9)
(3)

9
2

(9)
(3)

Humpback

___,_

1
8
1

(1)
(10)

(3)
(3)

(2)

Total
~

16
114
93
2
7

(29)
(150)
(134)
(21)
(7)

125
13

(149)
(26)
(1)

* Number in bracket shows the subordinate and dominant occurrences in the stomachs
of whales.

Still, recent investigation reveals very interesting distribution of
euphausiids in the northern part of the North Pacific. Since the year 1954,
distributions and occurrences of euphausiids and copepods are obtained
as shown in Table 8. From the Table 8, it is clear Thysanoessa inermis
and T. longipes are the most important euphausiids in the waters.

FOOD OF BALEEN WHALES

179

When I compare the Table 8 with the data before 1957, it is evident
that Thysanoessa longipes become dominant in the collected sample of1957 and 1958. One of the reason for the fact is due to the fact thatJapanese whaling operation have caught considerably many whales in the'@~""' o•••• • •

.,.

0

®

.,

®

®

®

... .

'Vl>

0

•

®

" ®: '1.&..-

,&!

•

..

,,.,.

®

0

B /60"E

•

•q •
170"E

0

0

170"w

180"

Fig. 14. Occurrences and distributions of Euphausia pacifica in the northernpart of the North Pacific since 1952. •-Dominant occurrences in the stomach
contents, O-Subordinate occurrences in the stomach contents, (!)-Occurrencesby net collections.
1

ao·

170"W

0

•

:.:.. .
.o• •• ••

0

•

0

. ..

••

oe

0• •• -:'=·0'~• • •• •

.i

... .

~

0.
0

•

~'

0

•

'

I O"E

170 E

180"

•
•

0

0

•

••

.

~

I\ •

170 w

Fig. 15. Occurrences and distributions of Thysanoessa inermis in the northernpart of the North Pacific since 1952. •-Dominant occurrences in the stomachs
of whales, 0-Subordinate occurrences in the stomachs of whales.

--~

__J

180

T. NEMOTO

south water of the eastern Aleutian Islands, Andreanof Islands and Fox
Islands where the swarms of T. longipes have been mostly observed.
Besides above two species Euphausia pacifica and Thysanoessa spinifera
have been observed and the more detailed knowledge is obtained on thecharacteristic of distributions.
Euphausia pacifica has been observed comparatively warmer waters
in the northern part of the North Pacific. I describe as to the distribution of E. pacijica that it vanishes as a dominant food of whales in
the north waters of Aleutian Islands (N emoto, 1957). The recent collections add many occurrences of E. pacijica as illustrated in Fig. 14.
None of specimen is found in the collected stomach contents of baleen
whales north waters of 56° north latitude. The net hall collections also
show the same tendency, as no specimen of E. pacijica is collected in
the north waters. From above result, it is evident that E. pacijica plays
little role of foods of whales in the north waters of Aleutian Islands
and significance of E. pacifica is not so heavy as in the southern waters,
adjacent waters to Japan (Nemoto 1957).
Thysanoessa inermis is described one of the dominant foods in the
Aleutian waters. Japanese investigation clearly reveals the concentration of T. inermis is observed in the north waters of eastern AleutianIslands, Fox Islands. There are also scattered occurrences in the westernpart of the North Pacific. In the southern waters of Fox Islands, someoccurrences of T. inermis are observed. But the number is far smaller
if the comparing with the occurrences of T. longipes is made. On thecontrary to the distribution of T. inermis, T. longipes is mostly foundin the off waters of eastern Aleutian Islands. Few T. longipes distributes along the continental shelf of the eastern Aleutian Islands, but
the dominant occurrences. are observed in the off pelagic waters fromthe continental shelf. The relative abundance of T. longipes in eachside of the North Pacific has not been given yet, however, the data by theyear 1958 furnish us that the most dominant area of T. longipes is in
the south waters of the eastern Aleutian Islands. Before reaching
the definite conclusion, the alternation among the euphausiids should beconsidered. For example in 1954, T. inermis was very abundant along
the continental shelf of the north waters of the eastern Aleutian Islands.
The next year in 1955, T. longipes was comparatively abundant in theoff waters of the same area along with the dominant patches of Calanus
cristatus. Along the south edge of continental shelf of the eastern
Aleutian Islands, swarms of T. inermis was very numerous in 1954, when
the considerable number of blue and humpback whales had been caught
in the waters. In 1957 and 1958, on the other hand, T. longipes has
been very abundant in the far south waters from the shelf, and few

181

FOOD OF BALEEN WHALES

whales distributed along the shelf. Above alternate occurrences of
euphausiids give us the very illustration of annual variation among theeuphausiids abundance. This must partly be due to some oceanographicalconditions in the sea water which I discuss in the latter part of thepaper. Thysanoessa spinifera distributes along the Alaskan continental
shelf and is neritic species (Nemoto, 1957). Japanese recent collections
add few samples of T. spinifera to the Fig. 4 of my previous paper,
but all occurrences are found along or within the Alaskan continental
shelf. As discussed in the previous report, no swarm of T. spinifera
170 w..__,.,----'\...
\

•
.•

0
0

0

(,

0

0
0
0

e
0 00 0

•• •
~•
•
0

.::::.::~.

;;~·.:.;

0

0

•
•
0

/60 E

170

180'

170

w

Fig. 16, Occurrences and distributions of Thysanoessa longipes in the northernpart of the North Pacific since 1952. •-Dominant occurrences in the stomach
contents. Q-Subordinate occurrences in the stomachs of whales.

is observed in the western part of the North Pacific. As shown in Fig.
18, and Table 8. Thysanoessa raschii is observed in the stomachs of fin
whales in the off waters of Anadyr gulf. I am very pleased to havethe specimens of T. raschii in the waters because I have little expectationthat T. raschii plays the role of food of baleen whales in the Bering sea.
The distribution of T. raschii is restricted to the shallow and neritic
waters within 50 metre in depth as illustrated in Fig. 18. The waterof Anadyr gulf contains less salinity affected by the flesh water by theAnadyr river, and temperature and salinity are lower than that of thesouthern waters, T. raschii can live in such shallow waters so that fin

182

T.NEMOTO

whales in the waters successfully take the euphausiids in the day time,
though it may go down to the near bottom depth as it is observed on
the another euphausiids Euphausia pacifica (Saito & Mishima, 1953).
Besides above food euphausiids, a young specimen of deep water living
Gnathophausia gigas is found in a fin whale in the north waters of the·.

"... ·.
.

:.... --·-- ..

b

0

II..

•

••

.•o• •••

e ,

~-

0

··.'l:,·.
••

0~.oee;0. · __(),,,.

.d'J..,_"' ~l~.·~··/

do •

0

•

•

\ .. !.I. •••• :o00•• • •
• •
•

0

•
•

/60'E

•

170'

170'w

I O'

Fig. 17. Occurrences and distribution of Calanus cristatus in the collected samples
of stomachs of baleen whales since the year 1952. •-Dominant occurrences inthe stomachs of whales, Q-Subordinate occurrences in the stomachs of whales.
170 w.. __ ••• --.,<;):.·: .

•• ••... /som. -............ /.... -.... , ..
·:'----<~ 75m
'.

•
B

176°E

0

180.

/76'W

110 w

/66°W

51

/62'W

Fig. 18. Occurrences and distribution of euphausiids in the stomach of baleen
whales in the northern part of the North Pacific. A-Thysanoessa raschii inthe north part of the Bering Sea off Navarin Cape. B-ThysanoiJssa spinifera
in the eastern Aleutian Islands.

eastern Aleutian Island among the swarm of Thysanoessa inermis. I
consider the fact is not due to the deep diving of the fin whale but tothe coming up of the Gnathophausia gigas to the near surface waters.
Copepods. Two important copepods are observed in the previous researches in the northern part of the North Pacific.

FOOD OF BALEEN WHALES

183

Calanus cristatus and Calanus plumchrus are the main copepods consisting the food of baleen whales. In my collections C. cristatus is
more abundant than C. plumchrus. But as stated in my former report
C. plumchrus is very important for right and sei whales. In Japaneseroutine observations, inspectors do not classify copepods into above two
species. Only biologists on board have some chance to do so. According
to their reports, C. cristatus is dominant in three areas. As shown in
Fig. 17, in the western part of the Near Islands, Galanus cristatus is
usually found in the stomachs of baleen whales swarming there fromMay. The next whaling ground of C. cristatus is the north waters of Fox
Islands. I already stated this distribution of C. cristatus in the previous
report (Nemoto, 1957) that T. inermis is dominant along the shelf andC. cristatus is in the off water of about 3000 meters depth. As plankton
survey shows the adult C. cristatus is found in the deeper waters than
500 metres (Nakai, 1954) in the waters adjacent to Aleutian Islands, it
is reasonable that C. cristatus swarms in the off waters where the sea
depth is more than 500 metres.
The third place is the south waters of the eastern Aleutian Islands,
where also considerable fin whales feed on C. cristatus. According toJapanese collections, the most northern collections are obtained in thewaters north of Komandorskiy Islands at about 56° North latitudes.
On the other hand, I already cited the work by Brodsky that the mainfood of fin whales in Olyutorsky Bay, which situated at about 60° North
latitude, is Calanus cristatus (Brodsky 1955). It seems reasonable
to say, further, that Calanus cristatus plays a role of food for fin
whales in the waters around the Aleutian Islands and Olyutorsky Bay.
Along the Alaskan continental shelf, Calanus cristatus has not appeared
as a dominant food but few cases and of course it vanishes within the
shelf. With regard to the quantity of C. cristatus, it needs morecollections before definite conclusion is obtained. But as illustrate inTables 7 and 8, Calanus cristatus bears the very important part of foodsof fin whales in the Aleutian waters.
Another macro copepods Calanus plumchrus distributes dominantlyin the south waters of the chain of Aleutian Islands and Komandorskiy
Islands. The most common occurrences are observed in the south watersof the eastern Aleutian Islands and south waters of Komandorskiy
where considerable number of sei whales have been feeding on Calanus
plumchrus. In the Table 8, only 3 samples of sei whales take C. plumchrus in samples owing to the insufficiency of collections. There are
evidences, however, that sei whales are mainly feeding on Calanus
plumchrus by the observations of biologists on board.
Calanus finmarchicus and Metridia lucens are described in my former

184

T. NEMOTO

report (Nemoto, 1957, p. 53, 54), but the successive investigations in 1957
and 1958 add no occurrence of these copepods to the previous results.
Fish. As shown in Table 7, swarming fish is considered to be very important in the northern part of the North Pacific, the north part of theBering sea. Before the year 1957, baleen whales feeding on fish arecomparatively small in number (see the table 2 in the previous report,
Nemoto, 1957). Only 7 fin whales and 5 sei whales take fish or mixtureof fish and plankton, though considerable number of humpback whales
take fish. The successive operations, however, find many fin whales
feeding on the swarming fish. Table 9, shows the occurrences of fishin these waters. There are some differences among the fish species according to whale species suggesting the difference of feeding habits.
Fin whales take mainely herrings and capelin and Alaska pollack, andon the other hand sei whales take only saury. Humpback whales havea particular favourite for Atka mackerel as given in the Table 9. The distribution of the swarming fish also shows interesting tendencies. Generally speaking, capelin, Alaska pollack and herring distribute in the highTABLE 9. FISH FOUND IN THE STOMACH CONTENTS OF BALEENWHALE CAUGHT BY JAPANESE WHALING EXPEDITIONSIN THE NORTHERN PACIFIC FROM 1952 TO 1958
Fish species
Un-

Whale
species
Fin whale
Sei whale
Humpback whale

Alaska Sand
Atka known
Herring Capelin Saury pollack lance mackerel

16

172

1

70

4

9

3

2

2

54

3

latitude of 58° north, and capelin is found from the Olutorskiy Bay toAndyr gulf along the Kamchatka Peninsula coast but two occasions.
The latter samples are observed in the north waters of Fox Islands ofthe eastern Aleutian Islands. Main occurrences go as far as the nearwaters of St Lawerences Is., but the most congregated area in the twoyears is the waters off Nawarin cape. The water depth there is about
within 100 meter and as I described the neritic euphausiid Thysanoessa
raschii is the main food for fin whales in the water. Fin whales took
sometimes T. raschii with capelin, the stomachs of which were often
satiated with the former T. raschii. The size of capelin is about 15 cm
and females are dominant usually in the swarms and stomachs of fin
whales. Herrings demonstrate the same distribution as capelin. They
are observed along Kamchatka Peninsula, mostly in the waters around
Olutorskiy cape and south waters of Nawarin cape. Zenkovich (1934)
states considerably many fin whales took herrings and often chase theswarms of herring in the Bering sea. Those occurrence of herring is the

185

FOOD OF BALEEN WHALES

next one to the Zenkovich's description in the North Pacific. The largest
size of herring is about 25 centimeter. At this stage of growth, herringmust migrate in a very congregated swarm which attracts fin whales.
Alaska pollack shows the dominant occurrences among these fish. It
is observed those fin whales fed it appear along the Alaskan continental
shelf from 58° North to 61° North especially in 1957. The size of Alaska
pollack never exceed 30 centimeter in length. This small size Alaska
pollack swarms in the shallower waters than the adult Alaska pollack.
The larger size Alaska pollack is found in the stomach of humpback
whales in two occations (Nemoto, 1957). In this case, it is clear that two

,...

...
--~"

·.•'·,, .

__ /- ~)·-...:.

.

61!__ ..... ·--·:;;.

•.----·.........

"El>•·

00:""•, .. _,, ..._.e.::)"':.~
0'Oo

Fig. 19. Occurrences and distributions of fish in the stomachs of fin whales caught
from 1952 to 1958 in the northern part of the North Pacific. e-Cape!in, (!)-Herring, •-Alaska pollack, O-Atka mackerel, •-Saury.

whales have different preference of feeding. From 1952 to 1956, few
fin whale was caught in the northern part of the Bering Sea, and Japanesewhaling expeditions have mainly covered the southern waters where
many euphausiids are abundant. In recent years, however, the transition of the food from euphausiids to fish must be considered. In 1956
and preceding seasons, the scouting boats for whales seek the school ofwhales in the northern part of Bering sea. But not so many fin whales
have been observed and the locality is unfavourable for whaling operation.

186

T. NEMOTO

In 1957, fin whales swarming in the north waters of the eastern Aleutian
water swim further to the north waters of the eastern Aleutian water andswim further to the north part of Bering sea along the continental shelfand feed on Alaska pollack. The relative abundance of euphausiids there
is considered not so sufficient as in the preceding seasons. The whaling
ground where Alaska pollack is fed shows no single occurrence of
euphausiids in the stomachs of whales. In some years, T. inermis
which is very abundant along the Alaskan continental shelf may propagate to the northern water along the shelf. But I have no specimenof T. inermis in 1957. Alaskan pollack fed by fin whales take, in its
turn, mainly food of Calanus plumchrus. Small pelagic amphipods arealso observed in its stomachs in smaller quantities. Calanus plumchrus
distributes in the northern part of the North Pacific widely. But according to Johnson (1958), C. plumchrus (C. tonsus) is not so common
in the Bering strait and Arctic sea. So, it is considered the main occurrences of C. plumchrus are within 61° or 62° North latitudes. The
patch of Calanus plumchrus may be a food for fin whales sometimes,
but fin whales never take favourably Calanus plumchrus. On the other
hand, to the larval and adolescent form of Alaska pollack, Atka mackerel
and adult" saury, Calanus plumchrus is the most favourable food especially because the usual living depth of C. plumchrus is the same asthat of the swarming fish.
The swarm of herrings found in the stomachs of fin whales caught
in the Olutorskiy cape feed mainly on Thysanoessa inermis and small
appearances of Calanus cristatus and C. plumchrus. As already statedin the part of Thysanoessa inermis, T. inermis is found in the northpart of the Komandorskiy Islands as far as 58° north latitude and thedominant occurrences are observed 57° north latitudes as shown in
Fig. 16. Because within the continental shelf, T. inermis is usuallyfound in far smaller number and only herrings from Olutorskiy to
Nawarin cape take T. inermis as their food.
Humpback whales are famous for their fish feeding. I describe humpback whales are very fond of Atka mackerel, as comparatively many
humpback whales take Atka mackerel in the waters near Near Islands
and Andreanof Islands. As shown in Table 9, the most favourite foodfor humpback whales is Atka mackerel of 15 to 30 centimetre. Fin
whales never take, the Atka mackerel of the latter body length, 30 centimetre. But humpback whales sometimes take Atka mackerel of 30 centimetre or adult. In the same way, humpback whales feed on adult
Alaska pollack in two occasions, and none of fin whale take it. Small
Alaska pollack fed by fin whales and Atka mackerel fed by humpback
whales contained many specimens of Thessarabrachion oculatus besides

187

FOOD OF BALEEN WHALES

Calanus cristatus and Euphausia pacijica in their stomachs in thewaters of Near Islands. It is a very interesting fact that T. oculatus
never swarms in so close patches as Thysanoessa euphausiids, and fin
and humpback whales of 'swallowing type' whales cannot take them.
On the other hand, for the migrating swarm of fish, T. oculatus become a food for them.
Sei whales are surface feeders and feed on saury only according toJapanese collections from 1952 to 1958. Of course, other swarming
fish may be a food for sei whales in some occasions. In the adjacentwaters to Japan, many kinds of fish are favourite food for sei whales.
But the limitting facter of foods of sei whales is due to their verticalliving layer, that is, the surface swimmer is only considered as a foodof sei whales. Sauries distribute largely in the North Pacific (Kasahara& Otsuru, 1956), and by observations on foods of whales, saury is

l60"E

170'£

-180"[

170"[

IBO"E

/70"W

Fig. 20. Occurrences and distributions of fish in the stomach contents of humpback
whales in the northern part of the North Pacific. Black shading-Atka mackeral.
Open circle-Cod. Cross-Probably Capelin. Square-Capelin.

mainly found in the western part of the Aleutian Islands, where thenorthern limit of the distribution of saury is considered. The stomachs
of saury are often satiated with copepods Calanus plumchrus, and thedominant occurrence of saury coincides with the dominant season andplace of Calanus plumchrus occurrence.
I find no addition to the occurrence of sand lance and capelin in thesouth waters along the Aleutian Islands since I wrote the previous
paper. So it is considered the important fish for baleen whales arefollowings.
Fin whale
Herring (Clupea pallasi)
Capelin (Mallotus catervarius)
Alaska Pollack (Theragra chalcogranma)
Sie whale
Saury (Cololabis saira)
Humpback whale Atka mackerel (Pleurogrammus monopterygius)
Besides above species, Cod, whiting) rockfish and sea lamprey are

T. NEMOTO

188

noticed through the observations (Matsura & Maeda, 1942 etc.). Theiroccurrences are considered to be very incident one, though there is still a
possibility that those fish, swarming so heavily, attract whales in somecases. Rock fish (Sebastodes polyspinis) and sea lamprey (Entosphenus
tridentatus) are apparently swallowed with other planktons or incidently
because above rock fish take planktons of the same kind as foods ofwhales and sea lamprey attacks whales (Pike, 1952; Nemoto, 1954).
These swarming fish show some fluctuation of abundance, which affectthe distribution and migration of whales very much in the northernpart of the North Pacific.
Squids. Squids have been considered not so important as a food forfin whales, because only 0.5 percent of total fin whales have taken
them. Sei whales have taken them in 3 percent of all. Humpback whales
have never fed on squids before 1956, but 1 humpback whale takef"IO"E

180'/'/O'W

...

\0
6

•6
·~
.........

8
N
/60'E
~~~-------...J.1.Q];___------'-''8""'o_·------~~--~

Fig. 21. Occurrences and distributions of squids in the stomachs of baleen whalesin the northern part of the North Pacific. &-Squids fed by sei whales, ,6.-Squids& others fed by sei whales, e-Squids fed by fin whales, O-Squids & others fed
by fin whales, •-Squids fed by humpback whales, 0-Squids & others fed by
humpback whales.

squids dominantly in 1956. Of course, no blue whale has taken squids.
Ommastrephes sloani pacijicus is dominant through the survey. Smallsquids ( Watasenia scintillans) and opalescent squid (Loligo opalescens)
are observed too in less occasions. Especially sei whales often takeOmmastrephes sloani pacijicus in the western part of the Aleutian Islands. Squids come up to the surface waters in dark time of a day,and sei whales fed on squids are mostly found in the night, twilighttimes and heavey clouded days like fin whales.
Foods of fin whales in each localit'JJ" and year
As described in the former part, blue whales feed only on euphausiids,
humpback whales on euphausiids and fish and sei whales on copepods
mainly. These three species show no typical change among their foodsin the northern part of the North Pacific. But foods of fin whales bear

FOOD OF BALEEN WHALES

189

some local characteristics as partly considered from the illustrations ofTables 10 to 12. In the south waters of Komandorskiy Islands, eastof Kamtchatka and west of Near Islands, the foods of fin whales from1952 to 1958 are illustrated in Table 10. From the Table 10, the main
foods are euphausiids and copepods. The former consists of Euphausia
TABLE 10. STOMACH CONTENTS OF FIN WHALES CAUGHT IN
THE OFF WATERS OF KAMTCHATKA PENINSULA,THE SOUTH WATERS OFF KOMANDOR ISLANDS AND
THE WEST OF NEAR ISLANDS
Year
Contents
Euphausiids
Eu. & Copepods
Eu. & Squids
Eu. & Fish
Calanoid
Ca. & Squids
Fish
Squids
Empty
Total
Not examined

1952

1953

1954

1955

1956

1957

1958

79
4

83
15

182
18

32
1

149
17
1

57
8

64
1

19

1
105

92

48

69
3

37

272
564

67
148

47
1
1
7
114
337

143
280

166
268
1

1
1
110
213

252
457
13

TABLE 11. STOMACH CONTENTS OF FIN WHALES CAUGHT IN
THE ADJACENT WATERS TO THE EASTERN ALEUTIANISLANDS FROM 1954 TO 1958
North waters

South waters
Contents~

1954 1955 1956 1957 1958
Euphausiids
Eu. & Copepods
Eu., Co. & Squids
Eu. & Fish
Eu. & Squids
Co. & Squids
Fish
Fish & Squids
Squids
Copepods
Unknown
Empty

66
4

7

8

171
13
3

75
2

1954 1955 1956 1957 1958
306

421
22

264
13

45
2
1

70
9

137

172
1
323

42

63
1
155

2
4
2

1
1
1
1
23

1

71

27

37

2
26

12
56

285

290

4
3
269

597

196

pacifica, Thysanoessa longipes and T. inermis, and the latter of Calanus
cristatus mainly and a few occurrence of C. plumchrus. The annualchange among foods is also observed, suggesting there are 'Calanus
year' and 'Euphausiid year' (Nemoto, 1957), which I describe in next
part. Euphausiids are a little more important in this waters as a conclusion. In the south waters of the eastern Aleutian Islands eupha~siids

190

T. NEMOTO

also play considerable part of the foods of fin whales. In 1954, themost of the euphausiids are Thysanoessa inermis along the continental
shelf along the Islands. Fin whales swarm on T. inermis exclusively
in the areas. On the other hand, Thysanoessa longipes take theposition of T. inermis among the food euphausiids in 1957 and 1958
as I describe in the part of foods in the north Pacific. In 1957,
Thysanoessa longipes was very dominant and numbers of fin whales
taking Calanus cristatus were comparatively less in number. But T.
longipes becomes rather less than the preceding season, and number ofcopepods are more dominant in 1958. From the above number of
euphausiids occurrences and empty stomachs of fin whales, the feeding
condition in 1958 is considered not so favourable for fin whales as in1957. As other occurrences of stomach contents, 56 fin whales feed on
copepods mainly Calanus cristatus and 12 fin whales on squids, also suggesting the above scarcity of euphausiids in 1958.
TABLE 12. STOMACH CONTENTS OF FIN WHALES CAUGHT IN THE
NORTHERN PART OF THE NORTH PACIFIC IN 1957 AND 1958
Stomach content
Locality
Alaskan continental shelf
58°-61°N
1957
Anadyr gulf & Navarin
Cape
1957
1958
Off Olutorskiy cape
1957
1958

C elin Alaskan Herring Thysano~~sa Copepod Empty
appollack
raschii
2

70
6
141
23

8
5
3

47
11

86
113
120
1
21

In 1954, almost all fin whales take euphausiids (mainly Thysanoessa
inermi's) along the Alaskan continental shelf. But successive operations
show the considerable occurrences of copepods in the off waters. Especially copepods are important for fin whales in 1956. Fish and Squids
are rather scarce in the waters north of the eastern Aleutian Islands.
In 1956, Japanese pelagic whaling covered the north waters of Komandorskiy Islands. Fin whales caught in the waters were feeding on
euphausiids mainly and on Calanus cristatus resembling to the constitution of the south waters of the Islands.
In successive operations in 1957 and 1958, the waters north of 58°N
latitudes have been covered, where many fin whales were feeding on fish,
Alaska pollack, capelin and herring. In 1957, along the Alaskan continental shelf from 58° to 61° North latitudes, some 158 fin whales
were caught by the Japanese operation. These whales were feedingon Alaska pollack (Theragra chalcogramma) exclusively but 2 whales
on copepods. Fin whales caught a little northern waters of Anadyr

FOOD OF BALEEN WHALES

191

gulf and off Navarin cape waters, mainly take a euphausiid Thysanoessa
raschii, and the rest of about 20 percent of the total feed on capelin
and herrings. The 6 fin whales caught in the off waters of Olutorskiy
feed on herring only. The aspect of feeding in 1958 is a little deff erent
from above preceding year. In 1958, capelin (Mollotus catervarius) is
so dominant that almost all fin whales take it in the waters off Navarincape, and no fin whales feed on Alaska pollack. This fact apparently
suggests that there are, annual fluctuations of swarming fish, and thefeeding condition of fin whales is very much influenced by the fluctuation. In the preceding season before 1957, the swarming fish, capelin
and Aaska pollak were not so abundant that fin whales did not migrate
to the northern water of the Bering sea. It was probable almost all
fin whales remained in the southern waters of the adjacent waters
to Aleutian Islands in those years.
---------------0
ir ___ ..

<;b

r

100

~

-0

·~ 60

i

0

-""
().

@

I

I

rf 19s6

J

~ 40

@

'®

"

f' \'\
Ip\I./ ,i \ ,// \
i
~/ l

80

,:/

20

t---i"
,

,

'

I

' '•I

/

,'

,'

/

60 0

61952

1957

I

20

• 1954

May

80

June

July

Aug.

Sept.

Fig. 22. Occurrences of euphausiids and Calanus cri$atus in the west
part off waters of the Kamtchatka Peninsula from 1952 to 1957.

Euphausiid year and calanus year
I describe in the former report there are ' Calanus year ' when copepods(mainly Calanus cristatus) is abundant and 'euphausiid year' when
euphausiids are abundant (Nemoto, 1957). As a example, I would referagain to the stomach contents of fin whales in the west part of thenorthern Pacific from 1952 to 1958. In 1952, the occurrence of Calanus
cristatus is not so many as compared with the number of euphausiids,
and the year 1952 is considered euphausiid year. In 1953, 1955 and1957, the number of fin whales fed on copepods are dominant in number. These years are considered to be Calanus year. Especially in 1953,
fin whales took Calanus cristatus mainly or 80 percent of total catch
fed on C. cristatus at the beginning of the operation. To discuss the
problem more clearly, the seasonal change between euphausiids and copepods should be considered. Generally speaking, Cope pods are dominantat the beginning of the season in May and June, and euphausiids become

T. NEMOTO

192

dominat from July to September as it is seen in 1953. This is the typicalchange which ' Calanus year ' demonstrates. In euphausiid year in
1954, both euphausiids and Calanus are observed in stomachs of whales,
and there is no typical change from May to July. In the latter part inJuly, however, euphausiids become dominant and copepods are vanished.
The latter part of this curve is rather related to the curve of 1952 asshown in Fig. 22. It may be safe to say in some euphausiid year,
though the complete transition from Calanus to euphausiids is finishedin August, from May to August euphausiids are abundant throughthe seasons. Anyway, in the late decade of August and September,almost all whales feed on euphausiids or Calanus cristatus disappear
from the surface waters of the area in August and September (Nemoto,1957). This affects the migration of blue whales, euphausiids feeder,
llo

.

E 60
~

"'

c.

g> 40

1
20

0

Blue-

Humpback

Sei

A

c

B

D

Fin

Fig. 23. Feeding percentage of baleen whales in the northern part of theNorth Pacific waters from 1955 to 1958. White-1955, Straight-1956,
Oblique-1957, Black-1958. A-West waters of North Pacific, B-Southwaters of the eastern Aleutian Islands, C-North waters of the eastern
Aleutian Islands, D-North waters of Komandorskiy Islands, E-Waters
along the Alaskan continental shelf, F-North waters of the Bering sea.

very clearly. In 'Calanus year' the migration of blue whales to thewaters becomes later, and earlier in 'euphausiid year' (Nemoto, 1957,
p. 77).
From the Table, the years 1952, 1954 and 1956 are considered euphausiid years, and the year 1953 Galanus year. The both years comealternately about every 4 years by rough examinations on the net samplesof planktons.
This phenomena must have some relations to the variation of strengthof 'Kuroshiwo' current, but the present data are so scarce that I would
wait further investigation and refrain from the conclusion.
Quantity of stomach contents
The quantity of stomach contents of baleen whales also has been exa-

FOOD OF BALEEN WHALES

193

mined in the North Pacific. The recent result of the routine works is
illustrated in Fig. 23. As a general tendency humpback whales takemore foods than other whales like those in the Antarctic. But blue
whales indicate comparatively low feeding percentage in the northernpart of the North Pacific. The feeding percentages of above two species
show yearly changes as illustrated in Fig. 23. These yearly changes
may suggest the feeding condition of each year to some extent which
I describe in the later part.
The feeding percentage of fin whales domonstrates local differences aswell as the yearly changes. In the whaling grounds, in the off watersof Kamtchatka (A in Fig. 23), it indicates the higher value than that of
the south waters of the eastern Aleutian Islands (B in Fig. 23). As fin
whales in these two waters mainly feed on planktons of euphausiids
and copepods of the nearly same species, the difference of feeding percentage is considered to be due to some reason of whaling season orabundance of foods. In 1955 and 1956, the number of fin whales caught
in the south waters of the east Aleutian Islands were comparatively
small in number suggesting the scarcity of the foods with the low
percentage of feeding. But the successive operation in 1957 and 1958,
many fin whales have been caught in the same waters but a little more
southern position and the feeding percentage in both years increase.
Still, they are lower than those of western waters (A in Fig. 23).
One explanation for this is the season of whaling. Japanese whaling
usually begins its operation from the western waters when the darkhour of a day is longer which may cause the higher feeding percentage
as this make the less diurnal migration of food planktons of whales.
Fin whales in the northern part of the Bering sea (F. Fig. 23) show
the highest feeding percentage, which is apparently due to partly thesea depth and food species in ·the waters. Fish and a euphausiid,
Thysanoessa raschii are eaten by fin whales in also daytime in theshallow waters of the northern part of Bering sea, and this makes thathigh feeding percentage of fin whales.
Sei whales only show 30 to 40 percent feeding percentage of all whales,
and there is no significant yearly change. The fact will suggest thatthe favourite food of sei whale, the crop of Calanus plumchrus, hasbeen constant in the described years.
KURIL ISLANDS

In the pre-war seasons, Japanese shore whaling from the landstationsof Kuril Islands had caught many baleen whales, but only few observation
on foods of whales in the waters is remained. 'Krill' and fish were194

T. NEMOTO

described as their foods.
Recent investigations by a Russian scientist (Betesheva, 1954, 1955)
gives us the fairly good comprehension on the problem. Two Thysanoessa
species, T. longipes and T. raschii are the main euphausiids in thewaters according to his description in 1954. Besides above euphausiids,
Calanus cristatus and C. plumchrus (tonsus) are described from thecopepods as food planktons. Squid, Ommastrephes sloani pacijfous,anchovy, Engraulis japonica, Alaska pollack, Theragra chalcogramma
l50°_NorthKur:J.?_~<l,
:~

160'
N
50

- 40

35

30

Bon1nls25

Fig. 24. Whaling centres around the Japan proper. Solid circles-whalinglandstations only before 1945. Open circles-whaling landstations whichhave been operated after the year 1945 too. The name of the landstation
before 1945 is referred to the old Japanese name.

are also found in the stomachs of fin whales. The 42 percent of fin
whales of the total, take euphausiids and 20 percent is occupied bycopepods (Betesheva, 1954). Though examined number is few, sei
whales feed on mainly squid, Ommastrephes sloani pacificus and a
copepod Calanus plumchrus (tonsus). Only one case, they feed on the
mixture of Calanus and a euphausiid, Thysanoessa raschii.
The results on little piked whale obtained in Kuril waters in 1951 isvery interesting (Betesheva, 1954). Little piked whales are feeding on

195

FOOD OF BALEEN WHALES

fish, Alaska pollack. And euphausiid species is all Thysanoessa raschii.
This neritic species has not been observed in the stomachs of baleen
whales in the off waters of Kamtchatka Islands. As T. raschii play asubordinate food of fin whales in the shallow Okhotsk sea, it must also
distribute in the very coastal waters to Kuril Islands where the coastal
form little piked whales are feeding. The following data in 1953 givesomewhat different data on foods of baleen whales caught in the adjacentwaters to Kuril Islands (Betesheva, 1955). Thysanoessa inermis is also
observed in the investigation. Fish Cololabis saira and Podonema
N

E

I

144.

i OKl1otsk

Seo

s·

/43"

144.

145° ENN:f

OK hot K Sea;zoom:'.20om

Fig. 25.~ Occurrence(and distributions of foods of fin and little piked whalesin the northern part of the North Pacific. 6-Euphaull'iids, JJJi..-Thysanoessa inermis, •-Euphausia pacifica, O-Vacant stomachs, •-Thysanoessa longipes and T. raschii. Left-little piked whales, Right-fin
whales.

longipes are added to the list of previous season in 1951. Fin whales
also feed on euphausiids, Euphausia pacifi,ca, but no Thysanoessa raschii
is described. With other occurrences of fish, Podonema longipes andCololalis saira, some annual changes among the foods may be considered.
Though sei whales show no typical change of constitutions among thefoods between 1951 and 1953, little piked whales feed only Alaska
pollack in 1953. It is desiable that the further accumulation of observations on stomach contents will be 9btained to explain above annualchanges and feeding habits of baleen whales in the waters adjacent toK uril Islands.
OKHOTSK SEA

In the Okhotsk sea, fin whales have been caught mostly, and a few
catch of sei and humpback whales are observed. Baleen whales in thearea mainly feed on euphausiids. From 1946-48, the biological observa-

196

T. NEMOTO

tions had been carried out, summary of which was already described byMizue (1951).
According to his descriptions, the main food for baleen whales is Krill andno other food is described. In recent operations, the number of whalescaught has been decreasing considerably. Owing to those small number of the catch, examinations on the stomach contents have been carriedout are not so satisfactory. I have 13 samples of stomach contents fromfin and little piked whales from the Okhotsk sea. Euphausia pacijica
and Thysanoessa inermis have been observed as a dominant food andThysanoessa longipes and T. raschii are also found among above two
species. The distribution of food euphausiids are not certain owing to
TABLE 13.

STOMACH CONTENTS OF FIN WHALES CAUGHT IN
THE OKHOTSK SEA IN 1955 AND 1956
1955

1956
,,,-----.·-------" ~-~--~·~

Euphausiids
June

"
"

Aug.

lst
2nd
3rd
lst

10

9
6

None Unknown
5
4
3

4
4

Euphausiids
1
6
2

Squids

None

1

1
2
2

Unknown
3
6

TABLE 14. FOOD EUPHAUSIIDS OF BALEEN WHALES CAUGHT IN
THE OKHOTSK SEA COLLECTED FROM 1953 TO 1956
r---· -

Occurrences

Euphausiids- - -----

E. pacifica T. inermis T. longipes T. raschii
Fin whale dominant
subordinate
Little piked whale dominant
Humpback whale subordinate*

3

4
2

2

1

1

7

1

* Dominant species is unknown, because the whale is flensed the day before myarrival at the landstation.

the scarcity of collections yet. But I would think that ' Krill ' contains
in this case only euphausiids though I can't insist on the staple food isonly euphausiids in the Okhotsk sea.
Euphausia pacijica distributes in shore waters and Thysanoessa
inermis in off waters. Fig. 25 shows little piked whales take mainly
Euphausia pacijica in the shore waters. There is the Abashiri river
running into the sea. The shore waters along the coast has less salinity
than the off waters. Euphausia pacijica is more neritic species in the
Okhotsk sea than Thysanoessa inermis or E. pacijica may be moretolerable in the less salinity waters. On the other hand, the main currents in this part of the Okhotsk sea may be divided into two origins.
One of the warm current from Tsushima current, and the other is theFOOD OF BALEEN WHALE

197

cold current of Sahalin current. From the distribution of water temperatures, E. pacifica appear in the warmer waters, and T. inermis in
the colder waters. Thysanoessa raschii is also observed with T. longipes
and T. inermis in the colder waters. As it has been considered as a arctic
neritic species I have found none of T. raschii in the oceanic whaling
ground of the North Pacific but the waters of Anadyr gulf (see p.
181). The fact that T. raschii is found in the stomach of fin whales isapparently due to the shallow waters of the Okhotsk sea. As in the
neritic waters along the Kuril Island, T. raschii is already noticed by
Russian scientists, as a food of baleen whales (Betesheva, 1954, 1955).
T. raschii and T. longipes are not so abundant as E. pacifica or T.
inermis in the Okhotsk sea, considering the occurrence in the stomachs
of baleen whales. Above occurrences and distributions are quite thesame as some previous paper on the subject (Iizuka, Kurohagi, Ikuta &Imai, 1954). These euphausiids must play the role of food for fish too.
Squid (may be Ommastrephes sloani pacificus) is found once in 1956 asa food.
As to humpback whales in this waters, I have no exact information on
about their food. But I have a chance to examine the scattered euphausiids on a flensing deck of the landstation. The whale is consideredfeeding on Thysanoessa species, T. longipes, T. raschii and T. inermis.
There is a evidence that baleen whales in the Okhotsk sea are sometimes feeding on swarming fish. From 1943 to 1945, 3 occurrences offish in the stomachs of fin whales, and in 1945, 9 little piked whales areobserved as fish feeding occurrences. The species of fish is following.
Fin whales
Sand lance (Ammodytes personatus)
Herring (Clupea pallasi)
Cod (Gadus macrocephaus)
Little piked whales Sand lance (Ammodytes personatus)
Alaska pollack (Theragra chalcogramma)
Regarding to the foods of little piked whales, Omura (1956) summarized
them. In his report, plankton organisms are described as 'Krill' containing copepods. But it is certain to consider 'Krill' means usuallyeuphausiids only in the Okhotsk sea owing to the shallow sea and thewarm current habitats. According to his report, saury and sardin likefish are described besides above species as foods of little piked whales.
It is probable that saury is found in the stomachs of whales in the
Okhotsk water along the coast, but I am not sure the sardin occurrencein the Okhotsk sea.

198

T. NEMOTOSANRIKU AND HOKKAIDO

Along the Pacific coast of north east part of the Japan proper, many
baleen whales have been caught and examined until now. Omura (1950)
and Mizue (1950) state the summarized consideration on the foods of
TABLE 15.

STOMACH CONTENTS OF SEI WHALES IN THE ADJACENTWATERS TO JAPAN IN THE NORTH EASTAREA FROM 1955 TO 1957

StomachContents
Euphausiids(Anchory)
Anchory
MackerelMackerel & Anchory
Saury
Saury & Anchory
Saury & Mackerel
Horse mackerel
SquidsSquids & Saury
Squids & Anchory
Squids & Euphausiids
Fish sp.
None
Unknown____,._,

May____,._,S * N**

S
14
21
7

13

June

1

10
1

Aug.

July

S

N
3
2

__,_
S N

N

13 24
6 11
4
1 3
1
3
1

3

Sept.

____,._,

S

S

7

2

6
6

1

Oct.

____,._,
N

N
10

6

8

9

3
7

5
11

7
2
1

25

9

1
1
6

1 27
1

11

4

21

38

4

3

3 92

13 23
3 89

1

36
65

5
1

103
104

* S-Southern waters of 40°N latitude.

2
1
25 16416 122

7
8

15 34
21 20

6 106

** N-Northern waters of 40°N latitude.

TABLE 16. FOODS OF WHALEBONE WHALES IN THE ADJACENTWATERS TO JAPAN OF SANRIKU AND HOKKAIDO AREASCOMPILED AFTER THE DATA BY MIZUE (1951)
Blue

Krill
SardinSaury
MackerelRock fish
Squids
Octopus
Empty

Fin

Humpback

Sei*

s

H

s

H

s

H

s

16
1

34

43
1

90
1
1

253
103
25
1
2
10
1
547

103
32
16

2

1

1
11

23

2

41

34

H
1

10

135
1
145

4

6

* Apparently include Bryde's whales in Sanriku waters.
whales in those waters. Their descriptions, however, are not so satisfactory, because the identifications of foods comprise many mistakes
as I discussed in a previous report (Nemoto, 1957, p. 45). To my greatFOOD OF BALEEN WHALES

199

regret, the recent investigations have added few observation and collections of the stomach contents owing to the cutting of whales' bodyto preserve the meat fresh. Especially very little knowledge has beenobtained after the paper by Mizue on the stomach contents of blue, fin
and humpback whales which have been caught also in few number inrecent operations. With regard to sei whales, comparatively many results show the same tendencies as that iilustrated by Mizue (1951),
though there are many unknown and empty (considerable part is considered broken stomachs) stomachs.
Sei whales in the Sanriku and Hokkaido areas feed mainly on euphausiids, anchovy saury and squids. Euphausiids consist of Euphausia
pacifica, Thysanoessa longipes and T. inermis in the northern regionof the water off Hokkaido. But latter two species are observed in only
a few occasion. In the southern waters from 35° to 40° north of theoff waters of Sanriku, Euphausia pacifica play a role of foods of baleen
whales. E. pacifica is considered rather abundant from spring to thesummer season in the southern waters and little piked whales migrating
to those areas from May to June also feed on Euphausia pacifica too.
Sei and little piked whales also feed on it, and fin, blue and humpback
whales caught in pre-war seasons must have fed on E. pacifica along
the coast of these areas. Among the fish, anchovy (Engraulis japonica)
sardin (Sadinops melanosticta) and saury (Colorabis saira) are the mostimportant species. As shown in Table 15, anchovy occurrs throughout
the season, but saury becomes dominant in the later part in September
and October. It coincides with the height of saury in these areas. Besides above two species, mackerel (Scomber japonicus) is found in aconsiderable number in September. The size of mackerel is not so large,
ranging about 7 to 20 cm in length.
Squids is also important for sei whales, especially in the northernarea. Mizue describes further that all the species of whales eat, besides"Krill", squids, the proper food for sperm whales in this sea area (Mizue,
1951, p. 88). But his consideration should be corrected. Because thespecies of squids on which sperm and sei whales feed are quite different. Sperm whales feed on mainly Onychoteuthis squid, Onychoteuthisbanksii, and sei whales seldom or never feed on it. Sei whales on
the other hand feed on large squids, Ommastrephes sloani pacificus
which is very abundant in the Sanriku and Hokkaido waters. There issome reliable evidence that the former squids distributes in so deeper
sea waters that sei whales, shallow water divers, can't take it.
As to the food of blue, fin and humpback whales, I would refer tothe results by Mizue, (1951) as summarized in Table 16. These three
species mainly feed on ' Krill '. Though the species contain two kinds

200

T. NEMOTO

of planktons, Calanus copepods and euphausiids, it must be Euphausia
pacijica from its abundance in these waters. The 10 stomach samplesof planktons collected from these areas are all E. pacifica, Thysanoessa
inermis and T. longipes. Although the main food plankton is Euphausia
pacijica, there are another evidence that sei whales are feeding on
micro-copepods Calanus helgolandicus too. I have 3 occurrences of it
in 1953 and also 3 occurrences in 1956 in the northern area of Hokkaido
region. Other copepods, Calanus cristatus and C. plumchrus have notbeen observed definitly, but it is probable that the whalebone whales takeabove two copepods in the northern Hokkaido waters where the cold
current planktons dominate abundantly. Food of Bryde's whales in
the Sanriku waters are mainly euphausiids and anchovy (Engraulisjaponica), and some Bryde's whales also take the larva of anchovy(Shirasu in Japanese) squids and mackerel.
TABLE 17. FOODS OF BRYDE'S WHALES IN THE OFF WATERS OF
OSHIMA, WAKAYAMA PREFECTURE IN 1955 AND 1958
Stomachcontents

lst

Euphausiidg
1955 { Anchory
Empty
StomachcontentslEuphausiids
Anchory
1958
Post larva of fish
Unknown & Empty

June

May
~~--~

2nd

1

3rd

lst

14

3

2nd

3rd

....,

2

May

July

June
~~

3rd

lst

1

2

2nd
8
1

1

-

2

1

18

3rd

7
23

~-~-

lst

2nd

6

3

3

Two right whales caught in the adjacent waters of Sanriku and Hokkaido in 1956 show the trace of the feeding Calanus plumchrus mainly
as the scraps collected from the stomachs are mostly of remains of C.
plumchrus (Omura, 1958). A little fragments of Calanus cristatus, C.
finmarchicus and Euphausia pacijica are mixed in C. plumchrus. The
size of Euphausia pacijica is considered only 10 mm or less and these
Euphausia pacijica must have not swarmed so mackedly but in the
scattered in the sea along with copepods. The quantity of foods forbaleen whales in Sanriku and Hokkaido waters was considered very
abundant. The feeding percentage given by Mizue (1951) shows very
high value, and in the pre-war season many baleen whales with fullstomachs had been caught along the coast of Sanriku and Hokkaido.
As I said, recent operation prove no such tendency owing to the lackof the complete remaining of stomachs and internal organs.

FOOD OF BALEEN WHALES201

WAKAYAMA, OSHIMAAt the Oshima landstation in the Wakayama prefecture, comparatively
many Bryde's whales have been caught by recent operations. Of course,
sei and other baleen whales had been described (Andrews, 1916; Omura,1950 etc.) in the seasons before 1945 and earlier season· after 1945, very
little is known about the foods of whales in the waters.
Bryde's whales in the waters feed on euphausiids and anchovy (Engraulis J'aponica). A euphausiid Euphausia similis is considered as arole in the earlier season of May, and anchovy play a greater partin the later season of June and July. Bryde's whales also feed onanchovy (Engraulis australis) in the south western waters of Australia(Chitterborough, 1959). These facts prove the feeding ground of Bryde's
whales lies in the warmer waters as considered up to this time (Rund,
1952; Omura & Nemoto, 1955), because anchovy generally distributewithin the warm current in the northern and southern hemisphere.
BONIN ISLANDS

In the adjacent waters to Bonin Islands, the pelagic whaling had been
carried out, and caught comparatively many Sei and Bryde's whales.
The investigations on those whales, however, were not sufficient todiscuss the problem completely. I am very sad that there has beenremaining only few samples of stomach contents of baleen whales in
the Bonin waters. They are all incomplete collections. Especially I
noticed there are many notes about copepods as foods of Sei whales in
the Bonin waters at the earlier date of pelagic whaling (Mizue, 1950).
But to my regret, the species is not certain because I have none of
the collections owing to the insufficiency of the preserving. I would
only expect future chance to study.
Some of euphausiid and fish samples of the stomach samples are foundin my laboratory, which are of use for considering the main foods inthese waters. The euphausiids examined are Euphausia similis andE. recurva, both of which distribute from subtropical to warm waters
in the north Pacific. Nishimoto, Tozawa & Kawakami (1952) describe
the food of sei whales in the adjacent water to Bonin Islands in ourscientific report No. 7. In the report, the euphausiids is named Thysanoessa gregaria with the illustration of Fig. 1. I would think it isa serious mistake. The illustration clearly shows the distinctions ofEuphausia similis. I would consider it is Euphausia similis which appears dominantly among the remained collections of Bonin Islands waters.
Thysanoessa gregaria is also found in considerable number by net collections in these waters (Nakai & Honjo, 1953). But Thysanoessa gre-

202

T. NEMOTO

garia never swarms so markedly as Euphausia similis, and the relative abundance of E. similis is far greater.
Fish swallowed by sei or Bryde's whales are all Myctophyid and Gonostomid fish. Yarrella sp described by Nishimoto, Tozawa & Kawakami, (1952), is Yarrella microcephala which is commonly found from thesubtropical warm waters. Myctophum asperum is another fish foundmainly in the stomachs of whales but in a smaller number. Myctophum
asperum is not found alone in the stomachs of whales, it is foundamong the Euphausia occurrences. There is another question as to thespecies of sei or Bryde's whales in the waters from feeding of view.
Because Mizue's data based on the catch from February to early May.
On the other hand, the distinct Bryde's whales cited by Omura,
TABLE 18. STOMACH CONTENTS OF SEI AND BRYDE'S WHALESCAUGHT IN THE ADJACENT WATERS TO BONIN
ISLANDS IN 1947, 1948 AND 1949
Feb.

March

April
____
--

3rd

lst

2nd

{Plankton
1947 Fish
empty

1

1

42

{Plankton
1948 Fish
empty

3

13

1

2

3
1
3
5

1

3

2

2

r.nktoo1949 Fish
Decapoda
empty ·

2

May
Total

,

,,----'~~-,

3rdlst
16" . 20
5
5

2nd

3rd

lst

2nd

24
4

7

10

7

3
5
7
7
3
1
1

1
6
2
2
5

15

10
1

10
5
14

3
4
8
2
9

5
16

4
6

6

4

2

6

7

:i

128
15
7
49
20
35
25
57
1
32

Nishimoto & Fujino (1952) were taken from the early May to June. So
the catch from February to the early May may contain real sei whales
as suggested by Omura & Fujino (1954). So it is probable that somebaleen whales described as sei whales in the former investigations from1946 to 1949 take copepads (Mizue 1950). As sei whales can take thescattered copepods in the sea with fine fringes and in skimming feeding,Mizue's description should be examined again with regard to above
suggestions.
As I stated in the former part, copepods are found in the stomachs
of sei whales (Mizue, 1950) in the earlier seasons. According to his
description, 13 whales take euphausiids, 34 Calanus and 17 young
serdines. The last species, young sardines should be corrected as Yarrella microchephala. These species show single occurrences of eachspecies in the stomach of whale. From 1947 to 1949, the rough classification of stomach contents of sei whale including some Bryde's whale

FOOD OF BALEEN WHALES

203

are illustrated in Table 18. The most dominant occurrences are observed in planktons' part containing different two species, euphausiids
and copepods, but in 1949. Fish is twice as many as planktons in 1951
according to the data by Nishimoto, Tozawa & Kawakami (1952), andthe whales species at the whaling periods are considered to be Bryde
whales considered from the season. Thus no Calanus copepods are foundin those whales. Generally speaking whales with vacant stomach show
comparatively few number when we consider the locality of Bonin Islands
waters in 25° to 28° North latitudes, the southern unreproductive area.
The fact that so many whales fed, on the other hand, clearly suggeststhat the waters around Bonin Islands is very productive though it locatedin the south waters. Subtropical convergence run through laterally theBonin Islands waters and especially in the seasons between winter andspring (U da, 1954). I find out many small pelagic Copepods in thestomachs of Yarrella microchephala which has generally the small monthpart. The most dominant species are Candacia species living in thesubtropical to boreal warm waters. None of euphausiids has been foundin the stomachs of Yarrella microchephala. On the contrary to this,
Myctophum asperum, which have comparatively large mouth part, takeeuphausiids. Each of Myctophum asperum feeds on Euphausia similisof about 10 specimens. Candacia species are not so congregated into
swarms of plankton, and they will not become a food for baleen whalesin themselves. But if it is fed by Yarrella species as a favourite food,Yarrella species may become food of Bryde's whales in the waters.
EAST CHINA SEA AND WEST KYUSHU AREA

In the seasons before 1945, Japanese whaling had covered broad area of
the Yellow sea and adjacent waters to Korea. These whaling grounds
had not been operated after the war as we lost the landstation of all.
In 1955, Japanese whaling have commenced the operation in the East
China sea from the landstation of a little southern waters of the Yellow
sea and adjacent waters to Korea. The baleen whales caught in thisarea are mainly fin and Bryde's whales. The latter species are, however, descriminated only after the year 1955. Before 1955 and pre-war
seasons, comparatively many sei whales (may be Bryde's whales) had
been caught along the western coast of Kyushu. The main grounds
for sei whales (Bryde's whales) in these area is described in Fig. 26,
and season of pre-war seasons before 1945 are between June to September. The whaling ground of Bryde's whales in recent years is also thesame as the preceding seasons.
Fin whales, the main object in these waters have been caught in the204

T.NEMOTO

off waters from the landstations, where no whaling operation had been
carried out. The whaling grounds range from 30° to 32°50' North
latitudes and 125°30' to 128°56' East longitudes. The water temperaturein the area is comparatively high ranging from 21°C to 29°C and differs
much from other whaling grounds of the feeding type (Nemoto, 1957) in
TABLE 19. STOMACH CONTENTS OF FIN WHALES CAUGHT FROM
THE LAND STATIONS OF WEST KYUSHU, GOTO ISLANDS
IN THE EAST CHINA SEA IN 1955 AND 1956
July

Aug.

Sept.

Oct.

~

~

~

~

2nd

3rd

lst

2nd

3rd

lst

2nd

3rd

lst

2nd

{ Euphausiids
1955 Empty
Unknown

6
4

3
26

6
9

1
5

5

7
24
2
5

1
17
6

2

16
19
1
3

10
35
2

{ Euphou.ikl•

3
20
2
12
1
7
25

2
38

17
16

14
10

10
16

1
1
21

17

2

Flying fish*1956 Blind eel*
Empty
Unknown

3
47

2

The quantity is not so large
TABLE 20. QUANTITY OF EUPHAUSIIDS IN THE STOMACHS OF
FIN WHALES CAUGHT IN THE EAST CHINA SEA IN 1955
BASING ON THE DATA OF REMAINED STOMACH
Quantity

3rd
Full
Rich
Moderate
Few

Aug.

Sept.

~

~~

July

1
1
1
3

2nd

lst

3rd
1
1
2
12

1
1
2

2

2nd

lst

Total

3rd
2
6
10
28

3
2
5

1

3
4

TABLE 21. STOMACH CONTENTS OF BRYDE'S WHALES CAUGHT
IN THE WEST KYUSHU AREA IN 1957 AND 1958
July

{ Anchory
Horse mackerel
Anchory
1958 Horse mackerel
Empty
Unknown
1957

l

Sept.

Oct.

~~

~~

Aug.

3rd

3rd

1

2
1

5

lst

2nd

4
3
4
11

1
2
9

3rd

1
2

lst

2nd

1
4

the North Pacific. Fin whales in this area feed on euphausiids mainly
except two occasion of fish and 1956. The quantity of euphausiids inthese waters is not so abundant as in the northern part of the North Pacific.
Illustrated tables show, that the whales with vacant stomachs are foundmore. Owing to the long draging from the whaling grounds to the land

205

FOOD OF BALEEN WHALES

stations, whales are cut at the belly portion of the body to preserve themeats flesh. As the result, stomachs are often damaged or swollen andcontents are washed away by the sea water. Thus the unknown stomachs, thus amount to a considerably number. It is difficult to decide
the quantities of euphausiids exactly because of said reason, but asdescribed in Table 20, the euphausiids' occurrences are clearly less than
the quantities of the North Pacific whaling areas.
I have got some 20 stomach samples of fin whales caught in thearea from 1955. These euphausiid are all Euphausia pacijica which isconsidered dominant in the East China sea and the Yellow sea. Euphausia pacifica is commonly found m the waters from adjacent waters to
NE

122°

130°E

124°

..
som

N

CJ

' '

I
I

/

/20om
~~,/
I

124"

126°

128°

. ~.
130°E

28

Fig. 26. Whaling grounds showing sea depth in the east China sea. Shading
area-whaling ground of fin whales. Double shading-main ground of fin
whales. Black area-whaling ground of Bryde's whales.

Japan, but I think this is the first description that E. pacijica play the roleof foods of fin whales in these waters. Of course, E. pacifica is alreadya famous food for mackerel in the Yellow sea up to these days (Nakai,1942). The relative abundance of euphausiids is not certain, but thefed fin whales are exceedingly small in number comparing with thenorthern Pacific water regarding the long pulling and lost stomachs bywaves. There are still some fin whales fed abundand euphausiids, however, Euphausia pacijica is not so abundant considering the occurrencesof fin whales with few stomach contents. Besides Euphausia pacifica,
blind eel (Eptatretus burgeri) and flying fish (definite species name is206

T. NEMOTO

unknown) are observed in the stomachs of fin whales. They are considered not so important as the foods of fin whales because only one
occasion of each species is observed. The blind eel lives coastal andneritic shallow waters of south part of Japan. It is also found in thesouth waters of Korea (Matsubara, 1955). The name of flying fish is
not certain, but some flying fish swim in swarms in the surface of thewarm sea, it may be probable that they attract the fin whales in thewarm waters.
Another occurrence of very particular organism has been observedin the stomachs of fin whales in the East China sea. So many MoNOSTOMATRIDAE parasitic worm are found that one may consider themas a food of fin whales. This worm is determined as Ogmogaster plicata
Crepl. or the related form by courtesy of Dr. J. Senoo of the Tokyo
University of Fisheries. This is found in the caecum of Balaenoptera
whales by Jagerskiold (Senoo, 1958), but I have never noticed in thestomachs of fin and other whales in other part of the sea. Further
information on the parasitic worm is desirable to get the definite cycleof the parasitic worm. Bryde's whales in the adjacent waters to Kyushu
are confirmed since the year 1955. These Bryde's whales have beencaught in the coastal waters as illustrated in Fig. 26. They are mainly
feeding on fish. In 1955, 2 Bryde's whales fed on small sardins(Sadinops melanosticta) which distribute widely and abundantly in thesummer season in these waters. In next year's operation, 3 Bryde's
whales with vacant stomach content are caught. In 1957 and 1958, 3
and 47 Bryde's whales have been caught respectively, foods of which
are summarized in Table 21. These Bryde's whales are feeding on
anchovy (Engraulis japonica (Houttuyn)) and horse mackerels. Horsemackerels in these waters are classified into three species, Trachurusjaponicus (Temminck et Schlegel) T. argenteus Wakiya and T. declivis(Jenyno), and it is not certain that how horse mackerels found in thestomachs of Bryde's whales belong to above each species, but T. japonicus and T. declivis are considered mostly common in the waters. From
the observations in 1958, 5 whales take anchovy abundantly and 3
whales take horse mackerels moderately, suggesting that the swarming
fish such as anchovy and horse mackerels are abundant in the waters
and the waters are very favourable for Bryde's whales. In 1944, theprovisional investigation has operated on the stomachs of whales, that is
25 sei* (Bryde's) whales feed on big sardin, 37 whales feed on sardins(may consist of sardin and anchovy) and 38 whales with vacant stomachs
in the same whaling grounds as the recent seasons. Big sardins were

* In 1944, Bryde's whales had not been discriminated from sei whales.

207

FOOD OF BALEEN WHALES

mostly found in July, but I am not sure if the observations were satisfactory in taxonomy.
ADJACENT WATERS TO KOREA

In the pre-war seasons, Japanese whaling had operated from the landstation of the both sides of Korea, in the Yellow sea and the Japan sea.
The rough observations on the fin whales caught in the areas weremade from 1940 to 1945. The food found in the fin whales stomachs
are all ' Krill ' but one occurrence of squids. Above two categories offoods are not identified to belong to any species. There is a evidence,
however, that Euphausia pacifica is very abundant in the Yellow sea
and the Japan sea (Nakai, 1942), Especially it plays the role of foods
for serdin and mackerels adjacent waters to Korea. He also found thatfin whales and little piked whales in the off waters of south Korea
mainly took Euphausia pacifica as their foods. Considering the dominance of Euphausia pacifica in these waters by previous works, above
stated 'Krill' is on the whole considered to be Euphausia pacifica. The
TABLE 22.

Krill
SquidsEmpty

FOODS OF FIN WHALES CAUGHT IN THE OFF WATERS
OF CHANZEN IN KOREA BY AVAILABLE DATAFROM 1940 TO 1945
Jan.

Feb.

Mar.

April

May

10

9

5

4

2

13

17
1
7

Nov.
14

Dec.
6

1

fact that fin whales in these water feed on 'Krill' in winter and insummer, suggests Euphausia pacifica is occurring throughout the year,
though the cycle of Euphausia pacifica in the waters is not certain
yet. According to Nakai (1942), a copepod Calanus plumchrus is themost dominant plankton in the surface water of the Japan sea. As it isfound in the stomachs of fin whales in the northern part of the North
Pacific, it may also bear a little significance for fin whales in the Japansea.
A swarming fish Clupanodon punctatus is once found in a stomachs
of fin whales in the Yellow sea at about 38°N latitudes and 124 °E longitudes. This is only occurrence of fish in the stomach of a fin whales
described in the pre-war investigations in the waters adjacent to Korea.
OKINAWA (RYUKYU)

Many humpback whales have been caught by recent whaling operationin 1958 and 1959. These humpback whales take nothing in their stomach

208

T. NEMOTO(Nishiwaki, 1959). A humpback whale take few fragment of Euphausia
similis in its stomach, but none of humpback whale takes the bulk ofeuphausiids according to the observations carried in 1959. There is another observation on a occurrence of euphausiids in 1958, the size of
which suggests that the euphausiids may be Pseudoeuphausia latifrons
distributing in the neritic subtropical waters (Nishiwaki, 1959). Other
foods such as bentholiving sea slug are considered to be fed by whales
according to whalers. But it has been not certain if humpback whales
are feeding actively in the warm waters of reproduction and rearing.
JAPAN SEA

Very few observation has been obtained as to the food of baleen whalesin the sea of Japan. Only data on little piked whales are followings.
Little piked whales in Wakasa Bay (whaling ground II in Omura &Sakiura, 1956, Fig. 17) take Calanus jinmarchicus and fish, sand lance,
The whales in the Hokkaido of the Japan sea side also take sand lance
mainly with other occurrences of Alaska pollack and euphausiids (probably Thysanoessa inermis).
BRITISH COLUMBIA
Pike (1952) describes the foods of baleen whales in the off waters of British Columbia in
his progress report. Thysanoessa spinifera and Euphausia pacifica are observed in thestomachs of fin, blue and humpback whales. To my regret, the name of copepods is notsuggested by his descriptions, but one occurrence of it is described in a fin whale stomach.
CALIFORNIA
The foods of humpback and grey whales in the waters of California are given by Howell& Huey (1930). Humpback whales take shrimps (Euphausia pacifica) and sardins. Euphausia pacifica also play some part of foods of grey, fin and humpback whales in thesewaters.

NOTE ON THE FOOD IN OTHER WATERS
AUSTRALIAN WATERS
In some Australian waters, humpback whales feed on euphausiids or other shrimps though
the food quantity is extremly few. Dawbin (1954) says in his letter, the whaler sometimes
observes semi-transparent "shrimps" smaller than Munida gregaria in the stomach of humpback whales in the Australian and New Zealand seas. Generally speaking, the foods in theAustralian and New Zealand waters are considered to be not so abundant as in the adjacentwaters to Japan. He notes further, there has been also a few fragments macerated fishbone too far digested for identification, and very finely digested crustacean materials. The
latter remains mean certain euphausiids may play parts of humpback whales. Dall andFOOD OF BALEEN WHALES

209

Dunstan (1957) describe the fragmental occurrence of E. superba in the stomach of a humpback whale treated at Tangalooma whaling station. They describe this is the first recordof the food in the stomachs of 2, OOO humpback whales examined at the station during 1952
to 1955 seasons. This observation causes some enthusiasm discussion by Jonsgll.rd (1957)
and Marr (1957). They consider the occurrence must have been due to the remaining ofdigested E. superba from the Antarctic waters. On the other hand Dall & Dunstan think
it is probable that E. superba is not confined to Antarctic regions, and that it may befound as a bathypelagic inhabitant of Antarctic waters in lower latitudes. I would also
consider the explanation of Jonsgil.rd (1957) and Marr (1957) is the most probable case.
Besides the incident occurrence of E. superba, Euphausia hemigibba and Pseudoeuphausia latifrons were identified from a whale caught in September at Point Cloates ofwestern Australia (Dall & Dunstan, 1957). Sheard and Chittleborough report Euphausia
spinifera from a whale at Albany (unpublished report cited Dall & Dunstan, 1957). Above
many tropical and sub-tropical species of euphausiids, as they are, are comparatively little
in quantity in the adjacent waters to Australia, and their swarmmings are not sufficientfor humpback whales feeding.
Grimothea stage of crustacean has also been considered in the warmer waters in thesouthern hemisphere. Mathews (1932) compiled (1932) the previous knowledge on Grimothea
larva of Munida gregaria and he stresses on its importance bearing the migration of the
humpback whale in the New Zealand seas. Around the New Zealand coast, Ommanney(1933) describes the south bound whales have a greater or lesser quantity of food in thestomach, while the stomachs of the north bound whales are nearly always empty. But
satisfactory expalanation for the fact has not been obtained.
Recently, Chittleborough (1959) reports the food of Bryde's whales that they were feedingon anchovy (Engraulis australis Shaw) along with young mackerels.

NORTH ATLANTIC
With regard to the food of baleen whales in the North Atlantic, many previous works
referred to the problem as I described in the former report and Mackintosh (1946) states
well summarized comment on then. Blue whales feed on euphausiids exclusively as in the
North Pacific (Einarsson, 1945). Thysanoessa inermis and Meganyctiphanes norwegica
have great importance for blue whales in Norwegian and Irish waters. Fin whales feed on
mainly planktons and occasionaly on swarming fish too. In the winter seasons fromJanuary to April, fin whales feed on Thysanoessa inermis and herrings, and in 'Summer
fishing ' from the middle of May to the end of seasons fin whales live on the large Krill
Meganyctiphanes norwegica (Hjort & Ruud, 1929). Between above two winter and summer
seasons Calanus copepods are observed in April after the figures illustrated by Hjort &Ruud (1929). The whaling grounds of both two periods stand on the different geographicalareas. During winter season, fin whales are caught and inside of bank, on the other hand,
they are taken on the slope of the continental shelf and slope of the bank in summer.
Sei whales feed on Calanus copepods exclusively along the Norwegian coasts (Hjort &Ruud, 1929), but in the waters off Finmark T. inermis play a role of food for sei whales(Collett, 1886). Euphausiid, Thysanoessa inermis is also important for right whales andhumpback whales in the North Atlantic as summarized by Einarsson (1945).
These observations and investigations are rather old, and I would consider, the study on
foods of whales in the Northern Hemisphere of Atlantic requires further investigation. Still,there is another important result that distinct parallel between the catch of sei whales
and abundance of Calanus finmarchicus is obtained by Hjort & Ruud (1929, p. 51, Fig. 31)The preceding of Calanus finmarchicus by a short time (about 10 days after the illustration) should be noted as a general character showing the relation between food and baleen

210

T.NEMOTO

whales. Japanese investigations also endorse the fact but preceding is considered by 7days or a week.
SOUTH AFRICA
Mackintosh & Wheeler (1929) describe some comments on the food of whales caught tothe adjacent waters to South Africa. These species of euphausiids Euphausia recurva,
E. lucens and Nyctiphws africans were included in the stomach contents according totheir descriptions. And it seems reasonable that they consider all species of Euphausian
occurring in the locality are consumed without discrimination when they are congregatedinto swarms. Besides above euphausiids, fish are found in the stomachs of some humpbackand fin whales examined at Saldanha Bay, however, the names of which are not described.
In general, the quantities of stomach contents appear to be empty or contain a verysmall quantity of food. This apparently means, as well published by Mackintosh (1942),
baleen whales in warmer regions in winter are feeding little organism but a very meagre
diet of certain small euphausiid, some lobster krill and perhaps an occasional meal of fish
(Mackintosh, 1942, p. 212). Many species of euphausiids in the warmer waters are considered not so congregated into swarms as in the North Pacific but scattered in the sea.
This condition is unfavourable for the swallowing type of baleen whales.
SOUTH AMERICA AND MEXICO
Matthews (1932) states Munida gregaria and its Grimothea stage form the food of the sei
whale according to Captain Fagerli. Many sei whales were feeding M. gregaria or its
larva at the surface or near the surface waters. In 1926 at Magdalena Bay on the Pacificcoast of Mexico, sei, humpback and Pacific grey whales were found to be feeding on thesecrustacea shoals, Pleuroncodes planipes (Matthews, 1932).

FEEDING HABITSMETHODS

The skrilful collecter of plankton and some other organisms in the sea,
baleen whales have two kinds of method to take their foods. Ingebrigtsen (1929) and I (Nemoto, 1957, p. 57) described Skimming and swallowing (gulping) as methods of their feeding. The swallowing by fin andhumpback whales is described by Andrews (1909). When feeding, fin
whales turn on the side, the water spouting from between the baleen
plates as the mouth is closed, and they often turn of rolling their bodyat the surface of the water, Humpback whales also show the roll on
the side (Andrews, 1909, p. 221), and Ingebrigtsen (1929) describe theskimming of sei whales. From the feeding apparatus and food of whales,
baleen whales are classified into the above two groups as follows.
Blue whale
f Fin whale
Swallowing (gulping) type
. Bryde's whale
Little piked whale
Humpback whalelFOOD OF BALEEN WHALES

Skimming type

211

Right whale{ Greenland whale

Swallowing and Skimming typeSei whale
As discussed in the former part of feeding apparatus, baleen whales
belong to blue whale type whales take their foods by swallowing. The
main food for swallowing type of whales is euphausiids as discussed in
the former part on Antarctic and North Pacific whales. But in somecases, swallowing type whales feed on swarming fish and copepods as
fin, whales Bryde's whales, little piked whales and humpback whales dosometimes. Swallowing type whales have generally thick and coarse
baleen fringes, and are fitted to take macro-planktons and fish. Tomilin(1954) simply considers those whales belong to the family BALAENOPTERIDAE are classified into macro-planktonophagi, with short and less elastic
plates, thick setous bristles and other peculiarities described in the previous section. Tomilin also refers to the fine baleen fringes of sei whales,and states sei whales may also be classified as " microplanktonophagi ".
Rearlly they feed mainly on copepods, Calanus finmachicus (Hjort &Ruud, 1929) in the Atlantic and C. plumchrus in the northern part'of the North Pacific (Nemoto, 1957). Of course, those Calanus copepods
are smaller than the euphausiids in general, but there is a importantresult which should be examined. I would point out that Tomilin has
never considered the pecurialities of patch or swarms of planktons.
It is evident that baleen whales with fine baleen fringes can take thesmall planktons, and the smaller Calanus copepods may escape thecapture by some species of whalebone whales (Marshall & Orr, 1955).
On the other hand, there are considerably many illustrations that fin
whales sometimes take small copepods Calanus plumchrus with roughbaleen fringes, and blue whales feed on the small euphausiids smaller
than Calanus copepods in volume, weight and size. Accordingly, I would
discuss the size and volume of each food planktons to understand therelative volume for the baleen fringes of plates. These values arenearly the same as those by Nakai (1942) on the materials collected in
the Japan sea. As illustrated in Table 23, Calanus finmarchicus is considered to be the most small size, and it seems reasonable only thosebaleen whales with fine fringes can take them. Calanus plumchrus
comes next position to C. finmarchicus and may be fed by sei and rightwhales most favourably. Thysanoessa longipes of 6 mm size is, however, smaller than C. plumchrus both in size and volume. This stage
should be classified as 'microplankton' according to its size and volume,
but blue whales sometimes feed on it. A blue whale caught in 1954 in
the south waters of the eastern Aleution Island fed on Thysanoessa
longipes of this size which is far smaller than Calanus plumchrus.

212

T. NEMOTO

The next indication is the case of Parathemisto gaudichandi in the
Antarctic waters. I found P. gaudichaudi in the stomachs of sei whales
and no occurrence is given in the stomachs of blue and fin whales as
discussed in the part of the Antarctic food. The stretched length of P.
gaudichaudi is about 16 mm and from 8 to 15 specimens may be contained in 1 cc. As these values are higher than the Calanus finmarchicus and small copepods, P. gaudichaudi should be considered as a
macroplankton in the sense. To make clear the above two cases, theswarming condition of planktons in the sea must be examined. The
special water noise caused by planktons (Cushing & Richardson, 1956)
also should be considered as a factor to attract the baleen whales inthe sea water.
TABLE 23. SIZE, VOLUME AND WEIGHT OF FOOD PLANKTONS OF
BALEEN WHALES IN THE NORTH PACIFIC AND
IN THE ANTARCTIC
Species of plankton

No. of individuals
contained 1 cc

Approximate
average length

Calanus finmarchicus*
Calanus plumchrus*
Calanus cristatus*
Thysanoessa longipes

300-500
50-1108-25
180-220
13-18
3-6
10-15
8-15

3mm
5
"
9
"
6
"
12
"
28
"
15
"
16

"

Thysanoessa inermis
Euphausia pacifica
Parathemisto gaudichaudi* All copepodite V stage.

"

I consider those swallowing type baleen whales feed on euphausiids
or copepods according to the state of congregated swarms of them. If
the swarms of planktons are not so heavy, swallowing type of baleen
whales pay little attention to the patch. On the other hand, skimming
type whales take sparse patch of planktons. In my previous report(Nemoto, 1957, p. 53), I discussed the case of Calanus plumchrus in
the northern part of the North Pacific. With consideration on the point
it seems reasonable that if the patch of Calanus copepods congregated
so heavily, fin whales can take the patch such as Calanus cristatus.
Swallowing type whales prefer euphausiids, swarming fish and swarming copepods Calanus cristatus to scattered foods in the sea. Amongthem, fin, Bryde's and little piked whales are rather polyphagous animals. (I would not consider 'polyphagous' is suitable for the whales
in a strict sence as I described in my former report p. 56. Here
I use the term only in comparing meaning). But blue and humpback
whales are considered to be monophagous and biphagous whales. As

FOOD OF BALEEN WHALES

213

described in Table 7, blue whale feed on only euphausiids. The twocases of blue whale feeding on the mixture of euphausiids and copepods
suggest that the patch of the mixture bear both characteristics of'euphausiids and copepods, and blue whales take them as a euphausiids'
swarm (Nemoto, 1957). Humpback whales are also euphausiid feeder
and fish feeder, and only very few of them take squids and copepods intheir stomach in the North Pacific. Of course the fact that humpback
whales congregate to the shore waters and copepods Calanus cristatus
and C. plumchrus distribute mainly in the off waters may cause such tendency. But as a whole, humpback whales never prefer squids and copepods as their food, they can't take scattered planktons in the sea. Fin,
Bryde's and little piked whales are rather polyphagous animals according
to the recent investigations. They take euphausiids favourably if there
is a sufficient swarm for whales in the sea. In the case of wanting
euphausiids, they take fish, squids and copepods too, but they never feedon single swimming fish or scattered copepods in the sea. In the northern part of the North Pacific, a fin whale take Metridia lucens in one
occasion (Nemoto, 1957, p. 54). Metridia lucens, as it is very abundant in
the surface waters in the North Pacific, swarms not so heavily as
Calanus cristatus, and usually is considered unfavourable for fin whalesof swallowing type as a food. So above case means the very rare occasion that Metridia lucens swarms heavily so that fin whales feed on
it. Right and Greenland whales take their food by skimming the waterwith the foods. This method enables whales to take scattered micro
planktons in the sea, but fine baleen fringes and long elastic baleen
plates may not be effective for swallowing the foods in a short timewith the gulp of water mass containing foods.
In the North Pacific, Greenland and right whales had been caught inthe shallow waters of the Okhotsk sea and the Bering strait within the
Alaskan continental shelf where the swarming euphausiids and copepod
such as Calanus cristatus are comparatively scarce (Townsend, 1935).
Only Thysanoessa raschii, the neritic shallow water species, and scatteredcopepods such as Metridia species are considered as dominant planktons.
Right and Greenland whales must have taken there scattered copepods
or other planktons by skimming.
It is very difficult to explain the feeding method of grey whales because few investigation has been carried out up to now. I can refer
to only one or two foreign observations on the foods of grey whales.
First, it should be noted that grey whales feed the bottom living amphipods (Zenkovich, 1937; Tomilin, 1954). In this case, grey whales
may skim the amphipods in the the bottom of the sea with rough baleen
fringes and tough baleen plates. On the other band, Howell and Huey

214

T. NEMOTO(1930) write the evidence that some grey whales feed on Euphausia
pacifica along the California coasts. Swallowing methods is consideredeffective for the swarms of euphausiids, however, it is probable E.
pacifica comes down to the bottom of the sea and is caught by grey
whales. From the narrower space of baleen plates row the shape of theplate and structure of skull and shorter baleen plates, it is probable thatgrey whales also take their foods by swallowing like Balaenoptera whales.
When feeding, these swallowing type baleen whales are considered toopen the mouth and take in quantities of the foods, then turn on theside (Andrews, 1909; Gunther, 1948). But as to the skimming typewhales, they swim with considerable or moderate velocity below thesurface of the sea, with their jaws widely open, and the micro-planktons
are filtered to remain in the cavity of mouth (Scoresby, 1820; Nemoto,1957).
FEEDING TYPES

Preceding a paper by Tomilin (1954), Eschricht (1849) and Kiikenthal
discuss the ecological or feeding classification of CETACEA.
By
those authors, whales are divided into five groups, "Ichthyophgi "," Planktophagi ", " Sarcophogi ", " Teuthophagi " and " Phytophagi ".
Tomilin (1954) states, however, these classifications are based on foods
only, and do not consider the adaptive morphological characteristics ofthe organs used to obtain the food. According to his conclusion, amongwhalebone whales, three adaptive types can be distinguished. Those
are microplanktophagi, macroplanktophagi and benthophagi. I would
consider further his classifications are inadequate in some means. As
I state in the former part, the euphausiids smaller than copepods (apparently microplankton) are sometimes fed by blue and fin whales whichhave coarse baleen plates fringes and classified as "Macroplanktophagi"by Tomilin. I would explain that the case must be due to the swarmsof euphausiids which are congregated so heavyly that blue and fin whales
pay attention to the patch. Blue whales is considered to have special
preference for euphausiids to other planktons in nature as I discuss inmany parts, and they are not ' Macroplanktophagi ' in a strict sense but'euphausiid shrimp feeder' in general. 'Microplanktophagi' describedby Tomilin (1954) must mean nothing but the skimming type whales,
and the latter whales can take scattered planktons which are generally
small and do not offer attention to swallowing type whales. As to thefood of Greenland whales, one of the skimming type whales or 'Microplanktophagi ', very little is known up to these days. But copepods arealso favourite food for right whales, another skimming type whale,

FOOD OF BALEEN WHALES

215

and right whales are considered as a copepods feeder in the North
Pacific (Nemoto, 1957; Omura, 1958).
Humpback whales are generally euphausiids feeder as well as fish
feeder, and they are anything but cope pods feeder or squids feeder as
discussed in the previous part. These words, euphausiids feeder etc.
may sound too common. But the words ' Macroplanktophagi ' and'Microplanktophagi' are not so satisfactory to explain the delicate feeding types of baleen whales. To make summarized comprehension on the
problem, the latter detailed classification may be helpful for the purpose.
In the northern part of the North Pacific where the relative abundanceof food for whales are dominant, following feeding types are considered.
Euphausiids feeder
Blue whale, fin whale, Bryde's whale, little
piked whale and humpback whale
macro-copepods feeder
Fin whale
Copepods feeder
moderate and micro-copepods feeder
Sei whale and right wnale
Fish feeder
small swarming fish feeder
Fin whale, Bryde's whale and little piked
whale
moderate and small swarming fish feeder
Humpback whale
Squids feeder
Fin whale, sei whale
From above classifications, it is evident that there are selections bywhales for their food and if there are sufficient foods above listed foundin the sea water, whales follows their food selection orders as follows.
Arrows show the order and lines show equivalent orderBlue whale
Euphausiids
Fin whale
Euphausiids-macro-copepods--Swarming fish~
micro-copepods~Squids

Bryde's whale
Euphausiids-Swarming fish~Copepods
Little piked whale Euphausiids-Swarming fish~Copepods
Sei whale
Copepods~Euphausiids-Swarming fish-Squids
Humpback whale
Euphausiids-Swarming fish
Right whale
Micro and macro-copepods~Euphausiids
In the adjacent waters to Japan, the aspects of the feeding types may
be a little different from those in the northern part of the North Pacificwhere the planktons are abundant. Only Euphausia pacifica is available
for the baleen whales among euphausiids as a dominant food, and only
some occurrences of Calanus jinmarchicus are considered. But anchovy(Engraulis japonica) and saury (Colorabis saira) are so abundant thatcomparatively many sei whales feed on above fish as often as on planktons. One may think that sei whales in the adjacent waters· to Japan216

T. NEMOTO

proper are fish feeder. But other blue, fin and humpback whales do notshow such difference in their feeding from data of the northern waters.
The above difference of sei whales must be due to the feeding of
methods, taking fish and squids by swallowing as well as microplanktons
by skimming. As illustrated in Table 7, blue and fin whales werefeeding on " Krill", but many sei whales were feeding on fish andsquids too. Thus, the feeding type of baleen whales in the adjacentwaters to Japan may be described as follows.
Euphausiids feeder
blue whale, fin whale
Fish feeder
sei whale
Squids feeder
sei whale
In the Antarctic waters, the large euphausiid, Euphausia superba
is available for baleen whales, (Mackintosh & Wheeler, 1929). With
Japanese recent investigations, the southern baleen whales take also
Thysanoessa macrura and Parathemisto gaudichaudi. In the warmer
waters, Munida gregaria and some other euphausiids are described in
the previous parts of this paper. Accordingly the feeding method andtype of the baleen whales in the southern hemisphere are given as
follows by the"se recent observations.
Swallowing typeblue whale, fin whale, Bryde's
whale, and humpback whale
Skimming & Swallowing type sei whale
Very little is known as to the feeding of right and little piked whales,
and their feeding type is also unknown. The swallowing type whalesin the southern hemisphere feed mainly on euphausiids, but there is another evidence that Bryde's whales in the adjacent waters to west Australian waters feed on anchovy (Chittleborough, 1959), humpback whales
on Munida gregaria, and sei whales on Munida gregaria too. But as
the data on the foods of whales in the southern warm hemisphere is not
sufficient except those of the Antarctic, it seems reasonable, therefore,
to refrain from any conclusion. Tomilin (1954) proposed food preferences of baleen whales developed in the northern hemisphere and not in
the southern hemisphere. His explanation may be reasonable to someextent because the main food of the Antarctic waters is Euphausia
superba, and right and sei whales also feed on E. superba in the Antarctic (Matthews, 1938, a, c). With the compliments to his explanation
the feeding type in the southern hemisphere is as follows.
Euphausiid feeder blue whale, fin whale, humpback whale, sei whale
Fish feeder
Bryde's whale
Amphipods feeder sei whale
Referring to the possibilities of feeding, right and sei whales may be
Copepods feeder as well as Euphausiids and Amphipods feeder, because

FOOD OF BALEEN WHALES

217

some copepods are abundant in the southern hemisphere in a scatteredcondition but they attract the attension of skimming type whales.
FEEDING TIME

I already discussed the details of feeding activity of the baleen whales
in a day in a previous report (Nemoto, 1957, p. 56, Fig. 11-14), and successive investigations have proved the same result. These conclusions
are followings. In the pelagic whalfog grounds (meaning the whaling
ground with deep sea bottom), the feeding percentage is higher in themorning and in the evening, and it shows decrease in daytimes. This

80

ID
O>

60

~
~

)!;: 40g>·.:.a"'"' 20u..

HourFig. 27. Feeding percentage of baleen whales in the northern part of theNorth Pacific in the south waters of the eastern Aleutian Islands in 1958.
Solid line-fin whales, Chain line-blue whale, Dotted line-Sei whales.
Black dot indicate the occurrences of squids.

fact is considered to be due to the feeding activity of whales and partly
diurnal migration of zooplanktons, fish and squids (Nemoto, 1957). Another marine mammal, northern fur-seals also show the same feeding
activity according to the diurnal migrations of their main food, .Myctophidae lantern fish (Taylor, Fujinaga & Wilke, 1955).
There are also some differences of feeding percentage according to
the food species and the environment such as sea depth. In the pelagic
whaling ground, where the sea depth is over 500 m or more, whales
feeding on euphausiid show the said tendency that they feed dominantlyin the morning and in the evening. On the other hand, in the coastalor shallow waters such as Andyr gulf in the northern part of the North
Pacific where the sea depth is less than 50 m, fin whales take a euphausiid· (Thysanoessa raschii) in daytimes. Thysanoessa raschii also follow the218

T. NEMOTO

general habit of the diurnal migration in the sea, and it is considered to·stay in the bottom waters of the shallow waters. The fact suggests
the feeding of whales may attain to the bottom layer of the coastal
waters of shallow depth less than 50 m. Capelin (Mollotus catervarius)
is also heavily fed by fin whales in daytimes in the Anadyr waters.
These facts give us a comprehension that whales usually feed on theirfood as much and often as possible to nourish them in their feeding
season. If it is possible to take food, they feed also in daytimes andthe many vacant stomach directly mean the some unfavorable condition
for their feeding in general.
The interesting feeding percentage of baleen whales in the south
waters of the eastern Aleutian Islands is illustrated in Fig. 27. Blueand fin whales take their foods mostly in the morning and evening as
discussed in the former report (Nemoto, 1957), but the percentage of blue
whales is higher than fin whales as a general tendency. As the mostfavorite food of blue and fin whales is considered to be euphausiids,
this difference of feeding percentage between blue and fin whales ispartly due to the feeding habit of each whale such as diving depth or
the extent of feeding activity. The feeding percentage of sei whales
show a little difference of the feeding percentage. The main food of sei
whales in the waters is Calanus plumchrus which has been considered
not to show the more typical diurnal migration. This directly may mean
the higher percentage in the daytime as given by the illustration. As tothe squids, fin and sei whales take them as a food in the waters.
Those squids are fed only in the morning from 6 to 12 by fin whales
and no squid has been fed in the afternoon from 12 to 18. Squids arealso migrating rapidly according to the diurnal change of light intensity.
These squids occurrences in the stomachs of fin whales are describedby single marks in the Fig. 27.
WEIGHT OF STOMACH CONTENTS

As tlre quantity of stomach contents of whales decreases in accordancewith the polongation of chasing by catcher boats (Nemoto, 1957, p. 65),
and the exact weighing of stomach contents is so difficult that few reliable information has been described. The old description shows thata blue whale take more than 1000 liter of euphausiids in the Atlantic(Collett, 1912), and the full stomach of large rorquals has been considered to contains about 1000 kg of planktons or fish.
The recent investigations by Nishimoto, Tozawa & Kawakami (1952)
and Betesheva (1954, 1955) treat the problem, and their data well demonstrate the quantity of stomach contents of whales. The stomach

219

FOOD OF BALEEN WHALES

contents of Bryde's whales in the Bonin Islands waters weighed by Nishimoto, Tozawa & Kawakami are ranging from about 100 to 200 kg in
the case of full stomach condition. The contents are all considered tobe Euphausia similis, and its freshness indicates that it is swallowed in
the short duration of feeding. Thus the amount of stomach content of
200 kg is directly mean the heaviest food taking of Bryde's whales. The
stomach quantity of sei whales has been measured by Betesheva (1954),
and he describes the full stomach of a sei whale containes 600 kg of squids(Ommastrephes sloani pacificus). Other sei whales in the Kurile waters
have also 50 to 370 kg of Calanur; plumchrus (tonsus).
Fin whales take more abundant food usually in their stomachs according to his observation. They take more than 100 kg of foods in 65
percent of all observations. The most abundant volumes are 560 kg of
TABLE 24. WEIGHT OF THE FOODS OF FIN WHALES CONTAINEDIN THE FIR'i>T STOMACH OF CAUGHT WHALES IN THE
NORTHERN PART OF THE NORTH PACIFIC*
Body
lengthSex

Food species

Relativequantity

Weight
(kg)

57
62
65
62
64
58
60
64

Male

Alaska pollack
Euphausiids

R
R
R
R
rr
rr
rr
r

759.0
112.5
100.0
81.0
30.0
30.0
26.0
10.0

ff

Female
Male
Male
Male
Male
Femaleff

Calanus copepods
Calanus copepods
Calanus copepods
Calanus copepods
Euphausiids

Measured by the courtesy of Mr K. Nasu.

squids, 464 kg of saury and 425 kg of the mixture, Calanus copepods
and euphausiids.
The exact weight of the stomach contents of fin whales are measured
in the northern part of the North Pacific on contents of both euphausiids
and copepods. The full stomach contains about 100 kg of stomach contents of euphausiids and Calanus which is less than those given by
Betesheva (1954, 1955) in the Kurile Islands waters. The fact may
partly be due to the food species contained in the stomach. These
Japanese data are only based on the planktons, euphausiids and Calanus
copepods, but the heaviest stomachs of fin· whales in the Kurile Islands
waters containes squids and saury. The one example of a rather small
sized fin whale also take vast volume of fish food (Alaska pollack),
which show the heaviest weight of the stomach content of fin whalesin the northern part of the North Pacific. The fish is generally digested. slower than the said planktons and the weight of stomach contents

220

T. NEMO'fcJ

of fish is heavier than plankton contents, and the specific gravity offish is apparently heavier than that of the plankton. These reason may
cause such results. The former whaling ground in the high latitudes of
the North Pacific is considered to generally produce more abundant foodplanktons, so it is strange that. fin whales in the northern part of theNorth Pacific take only 100 kg of planktons at most. It is desirable toweigh more examples in the water to get exact measurements ofstomach contents. But it is evident that fin whales take foods fromabout 100 to 700 kg in weight in their stomach in the Northern part of
the North Pacific. The grade of the quantity decided by routine works
on whales also shows the typical degree of the quantity as given in the
Table 24, which well indicates the relative quantity of stomach contentsof the fin whales.
DISTRIBUTION OF FOOD PLANKTON

Euphausiid
As I have described in the previous chapters, vast number of foodeuphausiids' distributions are examined. Considering from the stomach
contents of baleen whales and net collections, each euphausiid has been
observed following locality as illustrated in Fig. 28. These euphausiids
distribute in relation to the two main facters in general. One is theoceanographical condition which is illustrated by the water temperature,
the other is the shape of the sea which is mainly connected with thedepth of the sea. I would treat the distribution of euphausiids mainly
from the abundance of them in the sea considered by their occurrencein the stomachs of whales and fish with other net collections. So, thezoo-geographical grouping may be a little different from previous works
by other scientists mainly according to net collections.
Ruunstrc;bm (1927, 1930) and Einarsson (1945) make the three grouping,arctic boreal, boreal and Mediterranean boreal forms. According to
Einarsson's excellent discussions, Thysanoessa raschii and T. inermis
bear the arctic-boreal or rather low-arctic-boreal character. This is thesame in the North Pacific waters. By recent years investigations,
Ponomareva (1957) writes the account for the distribution of main
euphausiids in the north-west Pacific, and she also classifies euphausiids
into three distributional groups. Arctic boreal, boreal and tropicalgroups are her classifications. The latter groups by Ponomareva is apparently following to the works by Ruunstrc;bm (1930) and Einarsson (1945).
Arctic and Cold boreal group contain, Thysanoessa raschii, T. inermis
and T. longipes by the grouping of Ponomareva (1945). T. longipes is somewhat warmer water specimens, and it recalls Thysanoessa longicaudata

FOOD OF BALEEN WHALES

221

in the Atlantic in this point. As considered in the paper by Einarsson on
T. longicaudata, T. longipes in the North Pacific belong to the higher
temperature group. The next species, Thysanoessa raschii has beenfound in the stomachs of whales in the most northern part of the Beringsea, adjacent waters to Kuril Islands, and the Okhotsk sea. With otherobservations, Thysanoessa raschii in the North Pacific distributes in thewaters lower than 16°C by the surface water distribution described by
Fleming (1955). This value 16°C is the higher limit of surface temperature which is nearly the same value 15°C described by Einarsson(1945). The most northern occurrence in the north Bering sea is coveredby ice in winter, and the dominant occurrences are considered to be as
south as the middle Kurill waters. The water temperature in the area
do not exceed 13°C in August. This value also coincides with 12°C ofvigorous spawning area by Einarsson. T. inermis inhabits in somewhat
higher temperature waters than T. raschii, as I find the dominantoccurrence of T. inermis in the stomach of a fin whale in the waters
42° north latitude and 143° East longitude in the adjacent waters toJapan.
The range of distributional water temperature of T. inermis is about
the same as T. raschii. The former, however, distributes in more colder
waters, because I have found no dominant occurrences in the stomachs
of whales but a few individuals in the stomachs of capelin in thenorthern part of the Bering sea. By the fact that, T. raschii distributes as far north as the edge of pack ice, it is probable that T. raschii
is found dominantly in the neritic arctic sea.
With regard to Thysanoessa longipes, the dominant occurrences are
considered not to exceed as far as 60° north latitudes. Japanese investigation shows that the most north collection of T. longipes are madein the waters north of Komandorskiy Islands. T. longipes is also foundin the sea of Okhotsk and the south east waters of Hokkaido a little more
south than T. inermis. In the sea of Japan, Komaki & Matsue (1958)
also describe the occurrence of T. longipes. The water temperature in
the sea of Japan is higher than the waters along the Pacific coast by
the 'Tsushima' warm current. Perhaps T. longipes in the Japan sea
shows the distribution of the most high limit of water temperature.
The spineless form of Thysanoessa longipes is considered to distributein somewhat different way. Namely the spineless form distributes alittle more southern waters than the original spined forms (Boden, Johnson& Brinton, 1955). The spineless T. longipes is observed in three occasions in the stomach contents of whales dominantly in the western watersof the northern Pacific. Other single or subordinate occurrences are
more found in the western part than the east as illustrated in Fig. 29.

T. NEMOTO

222

According to my collections, and Japanese observations the spinelessform has not been observed in Okhotsk sea though the original form is

D

.

24'~

0

~24'

21°

Fig. 28. Schematic illustration of the distribution of euphausiids of foods of whalesin the North Pacific. O-Thysanoessa longipes, e-Thysanoiissa inermis, 0Thysanoiissa raschii, +-Thysanoessa spinifera, /',.-Euphausia pacifica, 0Euphausia recurva, A.-Euphausia similis, x -Pseudoeuphausia latifrons.
The large symbols show the dominant, moderate symbols show usual occurrences
and small symbols show the subordinate occurrences as whales' foods.
170 E

N

180'

170 VI

N
\)

•

56

No 153(1957)

St

1\
""'

54

o.
0

51

0

"i?c-"
~

0

•

0

150

;0
0

Fig. 29. Occurrence and distribution of spineless form of Thysanoiissa
longipes. Open circle-subordinate occurrences and net collections,Black circle-Dominant occurrences in the stomachs of whales.

found in the waters by net collections and stomachs of whales. The
another different evidence that the spineless forms found in the southFOOD OF BALEEN WHALES

223

waters of the Japan sea is stated by Ponomareva (1957), however, thenumber of the spineless form of Thysanoessa longipes is considered very
scarce or nil by Japanese investigations (Komaki & Matsue, 1958).
Thysanoessa inermis is considered to show the distribution between
T. raschii and T. longipes from Japanese investigations. It is observedin the s~omach of fin whales dominantly in the off waters of Olyutorskiy
cape where T. longipes is not observed as a dominant occurrence. The
most north collection is also obtained from the stomach of capelin foundin a fin whale stomach in .the water near St. Lourence Islands, but I
found none of T. longipes in the stomachs of capelin and other fish in
the northern waters of the Bering sea. In the Japan sea T. inermis
also distributes in the more northern waters than T. longipes (Komaki& Matsue, 1958). Thysanoessa inermis has two forms according to theclassification of the presence of spines at the 6 and 5 abdominal segments (Nemoto, 1957, p. 46). The one spine form is found exclusively
in the Atlantic. But the two spines form is dominant in the North
Pacific. It distributes mainly in the adjacent waters to Aleutian Islands,
but I have found none of the two spine form in the Okhotsk sea.
Also in the J~an sea, Komaki & Matsue (1958) illustrate one spine form
only, suggesting that one spine form of Thysanoessa inermis preservedin the Okhotsk sea and Japan sea in the North Pacific.
Above three species of Thysanoessa do not distribute in the Yellow
sea and mainly inhabit in cold boreal waters. From the considerationof spawning area and its temperature, these Thysanoessa species areclassified as Arctic boreal group or low-arctic boreal group as describedby Einarsson (1945, p. 130).
The distribution of Thysanoessa spinifera is also very interesting.
As I stated in the previous report (Nemoto, 1957), it is mainly foundalong the w'est coast of American side, and it plays a role of foods forwhales at British Columbia (Pike, 1950). T. spinijera has never beenfound along the Asian side, in the Okhotsk, Japan and Yellow sea, but
it distributes as south as La Jolla of California (Boden, Johnson & Brinton, 1955) in American side. This species may be also classified as
Arctic boreal group though it is considered a little warm water living
species. Euphausia pacifica is considered to distribute a little different
from above four species. Ponomareva (1957) already states that Euphausia
pacifica belong to the boreal group in its distribution, a warmer water
form than four Thysanoessa group. I would also classify it into theboreal group. Though Einarsson (1945, p. 130) prefers to call the temperate group to the Mediterranean-boreal group described by Ruunstrq'>m (1927), but this cold temperate group is also the same meaning as
the boreal group by Ponomareva (1957, Fig. 1), I would use the term

T. NEMOTO

224

to make contrast to the other Euphausia, Euphausia similis. Euphausia
similis mainly distribute in the subtropical waters and it belong to thewarm temperate group. Its dominant occurrences are restricted fromsubtropical waters to the warm temperate zone of 35° North latitude.
Pseudoeuphausia latifrons is considered to play a role of foods forwhales in the tropical and subtropical waters in the North Pacific, alittle south waters from the warm temperate group. It belong to thetropical group as it is described by Ponomareva (1957). The excellent
schematic illustrations of latitudal distribution of the euphausiids species
are given by John (1936) and Einarsson (1945). Here I would repeat iton the North Pacific species. The main food euphausiids in the antarctic
are oceanic pelagic forms (Einarsson, 1945, p. 136). On the other hand

..

ep

ac
E. crystallorophias
E. superva
T. macruro
E. lrigida---- --,__ J

T. roschi

r::•
'--·~

E. triacantha
E. vallentini··"
E.

longirostri~I
I
I

E. recurva
E. similisantarctic
zone

I

1.
I
I

[
r-·---

I

zone

I
centralzone

suba retie
zone

borealzone

T. longipes~

T. spin·1fera

-;g

"

0

E. pacifica

...c

g.
Q)

I

I
I

subanfercfic

T. inermis

II

T. vicina

heI

P. latifrons

-0
0

.£

E. recurva
E. similisa retiezone

Fig. 30. Schematic illustration of euphausiid fauna of the North Pacific and theAntarctic basing on the data by Einarsson (1945), Johne (1936) and foods of whales.
he-high arctic, ac-Antarctic coast line, ep-edge of pack ice, horizontal shadingneritic species, vertical shading-neritic but some sometimes found in ocean,Black-surface species.

four main food euphausiids are rather neritic coastal species, which isapparently due to the nature of the sea in the North Pacific. Only one,
Thysanoessa longipes is considered as a probable pelagic form, because
it has been mainly observed in the oceanic water mass and not been
confined to the coastal waters. T. longipes may take the position of
T. longicaudata of the Atlantic in the Pacific. Euphausia pacijica
mainly distributes along the coastal waters, but another Euphausia
similis and E. recurva are considered as the oceanic form. Sometimes
E. pacijica drifts to the off waters where many baleen whales feed on it
especially in Sanriku waters, and it is more oceanic than Thysanoessa
raschii, T. inermis and T. spinifera,

FOOD OF BALEEN WHALES

225

Those five main northern species have not been found in the southernhemisphere, but Euphausia recurva, E. similis and Pseudoeuphausia
latifrons play some parts of foods also in the southern hemisphereaccording to the previous investigations (Mackintosh, 1942; Chittleborough, 1959 etc.).
Distribution of food copepods of whales in the north pacificFour species of copepods have been found dominantly in the stomachs
of baleen whales in the North Pacific. Calanus cristatus, C. plumchrus,
C. finmarchicus (helgolandicus) and Metridia lucens are them. Thereis another occurrence of Calanus copepods described by Mizue (1950),
but the species is still remained unknown. It is considered to be a subtropical copepod not to belong Calanus copepods of boreal waters.
The representatives of Pacific boreal communities of Copepods, Calanus
cristatus, C. plumchrus are considered not to distribute so abundantlyin the arctic region, and will not be favorite food of baleen whales.
According to the observation on stomach contents of baleen whales,
Calanus plumchrus and C. cristatus have not been described in thenorthern part of the Bering sea and within the Alaskan continental
shelf. As I said in the former report, Calanus cristatus need deep
waters to be mature, it distributes mostly in the off waters of the adjacent waters to Aleutian Islands and the shelf. Johnson (1956) describes only one specimens of Calanus cristatus in the collection of theplankton in the Beaufort and Chucchi sea areas, suggesting that it does
not distribute abundantly in the arctic sea. Body length of C. cristatus is generally considered to be large in the cold waters. The sizeof C. cristatus in the North waters of Aleutian Islands is larger thanthat in the south waters. From these size distribution of C. cristatus,
there are some main local groups in the North Pacific near AleutianIslands.
Calanus cristatus has not been observed stomachs of whales in theadjacent waters to Japan, and it is also observed in few occasion in the
Kurile waters (Betesheva, 1954 & 1955), the bio-mass of C. cristatus isconsidered to be only sufficient in north water from about 45°N latitudes.
Galanus plumchrus is considered a little warmer water form and thesouthern range as a food of baleen whales may come down to 40°N latitudes
in the western part of the Pacific. Calanus finmarchicus (helgolandicus)
is considered more warmer water form, but the helgolandicus form distribute more southern waters. The small Copepoda collected from thestomachs of whales caught in the adjacent waters to Japan of Pacificside are all Calanus helgolandicus, and its southern range as a foodof whales may attain to 35°N latitude in summer season of the North
Pacific.

226

T. NEMOTO

MOVEMENT AND MIGRATION OF BALEEN WHALESDISTRIBUTION OF BALEEN WHALES IN THE NORTH PACIFIC

Whaling centers
With regard to migration and distribution of baleen whales, Mackintosh
made very important consideration on the problems (Mackintosh, 1942).
His summarized Table (p. 229, Tab. 9) gives us clear comprehension on
the distribution of baleen whales in the southern hemisphere except
some Bryde's whales' occurrences. After the example of Mackintosh's
table, the northern Pacific whaling centres and catch may be describedas Table 25. Table 25 shows that there are clear distribution of baleen
TABLE 25.

NORTH PACIFIC WHALING CENTERS AND CATCH ACCORDING
TO THE SOME AVAILABLE DAT A FROM 1910 TO 1945

Whaling centre
in PacificWhale species
Approximate No. of
latitude N seasons Blue

Arctic pelagic
North of 65°
Eastern side
Alaskan coast
53°-60°British Columbia
50°
Washington
47°
California
35°-45°Lower California pelagic 20°-35°
Maxico GorgonaWestern side
Kamtchatka pelagic
Ca 50°-65°
North Kurile
50°
Middle Kurile
45°
Japan coast
40°-45°II
II

Okinawa
Bonin Islands
Formosajf

Probably Bryde's whale.

741

35°-40°30°-35°
28°
27°
22°

Fin Bryde's Sei

7
7
2
9
1
1

318
59
2
239
85

1

2
3
12
14
15
14
5
8
8

74
7
2
70
186
429
5
9

591
104
293
1683
737
98
7
2

2
100
5
31

1176
634
53
145
34

4~

Hump- Grey Right
back

101

56

1115
183
246
1181
498
565

1

13
5
727
2
1226
79
34
2661*
480** 89
1** 131180* 288
3** 206
9

3

7
42
19
2

18

1

3
12
18
14
2
9
4

* Including Bryde's whale.

** Probably almost Bryde's whale.

whales in each latitude according to summer and winter seasons ofwhaling.
Arctic sea. As to the Arctic ocean, Japanese pelagic whaling covered
Chukchee sea in 1941, and fin, humpback and grey whales were caught
along the Siberian coast. No other baleen whales was caught thoughsome Russian scientists consider the migration of blue whales reachto the Arctic sea (Sleptsov, 1955). Another observations made by Nikulin(1946) endorse the Japanese result. According to the data by Nikulin

FOOD OF BALEEN WHALES

227

fin, little piked, humpback, grey and Greenland whales had been observed, and no blue and sei whales are described in the adjacent waters
to Chukchee Peninsula. From 1937 to 1943, following number of baleen
whales, 1051 fin, 1904 grey, 687 humpback, 118 little piked and 12
Greenland whales had been observed. Thus fin, humpback, grey, rightand Greenland whales distribute in the Arctic sea as a conclusion. The
evidence if Greenland whale exists has not been given and I would notstate further comment on Greenland whales' distribution and occurrence
here. Kamchatka pelagic (western side). In the off and adjacent waters
to Kamtchatka peninsula in Pacific side, many whales has been caught byJapanese and Russian pelagic whaling. Fin whales are considered to be
most dominant in the waters with blue, sei and humpback whales.
Among them, blue whales has been caught only in the southern waters of
Komandor Islands (about 55° North). Grey whales' occurrences areapparently considered as a illustration that some grey whales may migrate along the coast of Kamtchatka peninsula from north to south in
the north waters of Bering sea. Though there is no evidence in theold statistics that Bryde's whales have not appeared, the recent investigation on Bryde's whales affirms that Bryde's whales never migrate
to the cold waters of Kamtchatka coasts.
•
Kurile Island. The catch of Kurile Islands situated between Japan
proper and Kamtchatka bears the intermediate character between above
two localities. In the Noth Kurile waters, the catch is the same asthat of Kamtchatka waters. Fin whales are the main catch of thewaters, but number of sei whales are not so dominant. The catch inthe middle K uril water region shows a little difference from the northern
Kurile waters. Sei whales become dominant in number and form themain catch of the waters.
Japan coast. Along the Pacific side of Japanese coasts, many baleen
whales have been caught both in the pre-war seasons and after theyear 1945. From those statistics, the differences among the catch in theeach landstations are observed. Fin and sei whales make the main partof the catch in the northern coasts from 40° to 45° North whereas sei
whales become more dominant in the south waters from 35° to 40°
North. Among the catches of sei whales in the waters, however, someconsiderable number of Bryde's whales should be considered. As Omura& Fujino (1954) and Omura & Nemoto (1955) state, Bryde's whales havebeen caught in the summer season in the waters along the Pacificcoasts of Japan from 35° to 40° North. Along the southern coasts ofJapan from 30° to 35° North, the considerable catch of blue whales
had been described from 1910 to 1923 in winter seasons at the Wakayama prefecture landstations. But after 1923, blue whales decreased

228

T. NEMOTO

in number and scarcely caught by recent operations. The recent investigations have proved that sei whales caught in summer season are
all Bryde's whales. But among the catches, before 1945 some occurrencesof sei whales also should be considered according to the paper by Andrews(1914), but above catches were obtained rather in earlier seasons of theyear when the migration of sei whales was probable.
Okinawa. Humpback whales are the main catch in winter seasons.
Number of blue and fin whales are extremly scarce in number in thewaters, suggesting that these whales do not come down to the subtropical water or do not approach the Islands. Sei whales caught insubtropical waters of Okinawa may apparently be Bryde's whales.
Bonin Islands. Humpback whales had been caught dominantly in theearlier seasons, but Bryde's whales become dominant in recent catches.
Few blue and fin whales have been caught as in the Okinawa waters.
TABLE 26.

Arctic sea
Bering sea
Sea of Okhotsk
Sea of Japan
Yellow sea
East China sea
South China sea
California Bay
Pacific coast

BALEEN WHALE OCCURRENCES IN THE PACIFICOCEAN AND ADJACENT SEAS
Blue

Fin

+
+
+
+

-!tt
-!tt
-!tt
-!tt
-!tt
-!tt

Bryde's Little
piked

+
+
-!tt
-!tt

+
+

*

+

Sei

+
+

Humpback

-!tt
-!tt

+
+
+
+
+
+

Right

Grey

+

-!tt
-!tt

-!tt
-!tt
-!tt

+

+
-!tt

+

*

+

*
-ttt*
-!tt
-!tt
-!tt
-!tt
-!tt
-!tt
-!tt
-ttt-whaling operated,* Only along the American coast of the Pacific ocean.
+-occurrence observed.
*-Considerable occurrences,

Formosa. Only humpback whales are the main catch. Still, there aresome captures of blue, fin and sei (Bryde's) whales, but they neverconsists the important catch of the warmer waters of Formosa.
American side of the pacific. Along the western coasts of Americanside of the Pacific, the same catch tendencies have been observed as
illustrated in Table 25. In the northern waters, fin whales occur inconsiderable number, and humpback whales in the southern waters.
Blue whales were caught in the off waters of Lower California by thewinter pelagic operations in a fairly many number with humpbackand grey whales. As a general observations, the distribution of baleen
whales and the catch in both sides of the Pacific are not different except
the local distribution and the migration of some whales which I would
discuss in the next part.

FOOD OF BALEEN WHALES

229

THE SHAPE OF THE SEA AND DISTRIBUTION OF BALEEN WHALESThe baleen whales migrate in the sea, following their foods and tocomplete their reproducting purpose. The catch and observations up tothese days give us the general tendencies about the distribution according to the shape of the sea and submarine topography. Krummel(1907) and Kuenen (1950) describe the seas, and I would summarize
the subject following above authors. The seas are distinguished firstas Oceans and Ad}acent seas. Adjacent seas (Dependent seas) are also
divided into Marginal seas (Fringing sea) and Mediterranean seas,
which are divided into in-continental sea and inter-continental sea.
When above classifications are used, the seas around the North Pacificmay be summarized as follows.
Ocean-The PacificMarginal sea-Bering sea, Okhotsk sea, Japan sea, East China sea,
South China sea, California Bay
Mediterranean sea-Arctic sea.
Baleen whales distribute in each sea locality as illustrated in Table
26. With regard to the distribution of blue whales, they are mostly
caught and found along the Pacific coasts (or the Oceanic coasts) of theeastern and western sides. Number of blue whales have been caught
in Marginal seas or Mediterranean seas is extremly limited numbers.
As it is shown by the catch statistics, no blue whale has been caught
and only few blue whales observed in the Bering sea, and no record ofblue whales in the Arctic waters through the Bering strait. In othermarginal seas, blue whales have been scarcely caught as described inTable 26. The same tendency is also considered as to sei whales. Sei
whales (some occurrences of Bryde's whales must have been included)
have never been caught so markedly in the Yellow sea, the Japan sea
and the Okhotsk sea. Some 44 sei whales illustrated in the Table 27
were obtained from the catch of the landstations situated near the Kuril
Islands, where some visitors of sei whales from the Pacific side throughKurile Islands were probable. Right whales show very little occurrencesin Table 27, but it should be considered to be due to the decrease of
the stock. By American whaling in 19th century, right whales had beenmostly caught in the Okhotsk sea and the sea of Japan (Townsend, 1935).
A right whale also occurred in the Mediterranean seas, at Taranto in Italy,(Capellini, 1877) suggesting that right whales occur in the Inter-continental sea. Thus right whales are considered not oceanic denizen only.
The coastal forms, humpback and grey whales are commoner thanabove BALAENOPTERIDAE whales, however, when the catch of otherlocalities are referred, the former species are not so abundant in the

230

T. NEMOTO

Marginal seas. Humpback whales usually congregate along the coastal
waters of the continent, around islands in the ocean and the archipelago
between the ocean and the Marginal seas. In winter seasons of theNorth Pacific, they swarm in the waters of Formosa, Marshal Islands,
Bonin Islands, and Okinawa Islands in the western side according to
the catch statistics. From California to Lower California and Mexico,
the winter catch of humpback whales has been demonstrated in theeastern side of the Pacific. Considering the catch in above districts,
humpback whales are rather oceanic coastal form and their occurrencesin the marginal sea and the mediterranean sea observed are temporary
one, though comparatively many humpback whales had been caught in
the Arctic sea region by Japanese operations in 1940.
TABLE 27. NUMBER OF BALEEN WHALES CAUGHT IN SOMEMARGINAL SEAS OF THE PACIFIC FROM 1916 TO 1949 BY
JAPANESE SHORE WHALING OPERATIONS
Whale species
Seas
Hump- Right Grey
Fin
Sei
Blue
back
Okhotsk sea
East coast of Korea
Yellow sea

4
13

1149
1977
3137

44
2
2

58
47
63

8

2

2

606
7

Grey whales have been only observed and caught along the coast of
the land, and continents at the oceanic side and in the adjacent seas
and the mediterranean sea. Of course, there still remain some questions
about the migration routes of grey whales. In some migration course,
they may swim in the far off waters from the American continent(Gilmore, 1955), but they are apparently coastal form and ne.ver regarded
as a oceanic form. The migration course should be examined by further
examination. Fin whales have been caught not only in the oceanic
sides, but also in the marginal seas and the mediterranean sea. In the
Arctic sea, Okhotsk sea, Bering sea, Yellow sea, East China sea, andsea of Japan fin whales demonstrate the highest catch among baleen
whales by whaling operations. Bryde's whales, on the other hand, havebeen caught and observed mainly along the Pacific sides of Japan andCalifornia. Recently the sei whales caught along the western side of
Kyushu prefecture (the southern main Island of Japan) and in theeastern part of the East China sea in summer seasons are proved to be
all Bryde's whales (Omura & Fujino, 1954; Mizue, 1956). And anotherevidence gives us the occurrences of Bryde's whales in the adjacent waters
to Borneo (Harnisson & Jamuh, 1958) and Singapore (Anderson, 1878).
These apparently suggest that Bryde's whales migrate to the south

231

FOOD OF BALEEN WHALES

waters of the South China sea, the Marginal sea. But if the numberof whales will be considered, Bryde's whales are rather oceanic form
as a conclusion. With regard to little piked whales, they are described
as a coastal form by Tomilin (1954). Really the Japanese investigations
prove (Omura & Sakiura, 1956) that little piked whales migrate along
the coasts of Japan proper in both sides, the Pacific side and Japan sea
side. Many little piked whales have been caught in the Okhotsk sea
and along the Japan sea coast and Korea (see Fig. 17 by Omura &Sakiura, 1956). Further in the Antarctic and other parts of the seas,
they penetrate into the gulf, bay and straits even into the pack ice
crevice. From above occurrences, little piked whales are not a oceanic
form, and they inhabit also in the Marginal and the Mediterranean seas.
Besides above baleen whales, Greenland whales had been caught in
172°E

180°

'

I

·-

172W

164W

•68W

6

I

Blue
Fin+ Blue

11-3.

8-1

13·9
70-6

6

22.2 26-2

24.7

39.2

62-1

loo.o

38· I

78-1

68-9

~-0

84-2

7

69.2

~

68

44,4

69

..... ___
___

42.9

19-6

52-9

-- - ---- ---- -----.:::::::::?'----·--

I/
83-3

"

/

172E

180

I

6

6

Pack line·Pa c k Ii n e
1
1

70

100/

/

I 6

I
l72°W

168°W

I
164°W

Fig. 31. Catch distribution of blue and fin whales by Japanese pelagic whaling
operations along the pack ice line in the Antarctic waters from 1949 to 1950.
High value show the domination of blue whales.

19th century in the Okhotsk sea and the northern part of the Bering sea,
Bering strait and Arctic sea. Especially in the shallower waters of theBering sea and the Okhotsk sea, the most dominant catch was observed(Townsend, 1935). Greenland whales are considered shallow marginal
sea form and not a oceanic form. Thus I would conclude following
distributional type of baleen whales in the northern part of the North
Pacific.
Blue whale, sei whale, Bryde's
Ocean denizen
whale
Pelagic form fin whale, right whale
Ocean and marginal sea
Coastal form
little piked whale,denizengrey whale, humpback whale
Greenland whale
Marginal sea denizen
Tomilin (1954) consideres the Antarctic whales are considered to be re-232

T. NEMOTO

cent emigrants from the Northern Hemisphere, because the close relationship between structure of the baleen and the nature of the food of
whalebone whales is disturbed in the Southern Hemisphere. The distribution of whalebone whales in the Antarctic is also very interesting tostudy. General aspects of the southern Ocean are rather simple in viewof the shape of the sea when the comparing with the North Pacificis made. The Antarctic continent is surrounded by the ocean and only
two Ross and Weddle seas make incisions along the coast of the continent.
Whalebone whales come to the Antarctic waters generally from September
to February and return to the North from March to July (Mackintosh& Brown, 1956), and the height is observed in February in the summer
season of the Antarctic. From the observations by whaling operations
which cover the adjacent waters to the pack ice edge, blue whales havebeen mainly observed along the pack ice and fin whales have been observedin the off waters. Whalers usually say, they hunt blue whales in thepack ice and chase fin whales in the off waters. By Japanese whaling
operation from 1949 to 1950, Japanese operations have caught blue andfin whales in the Ross sea area as illustrated in Fig. 31. It is clear
from the figure that blue whales were caught mainly along the packice and fin whales were caught in the off waters. Sometimes whalers
have noticed the big herds of fin whales in the off waters more than
200 miles from the pack ice. This fact bears some connection with the
distribution of food euphausiids. 'Blue whale krill' distributes mainly
along the pack ice, and 'Fin whale Krill' mainly in the off waters,
the fact of which suggests their distributions are restricted also by the
distribution of euphausiids.
As I stated before, little piked whales are often observed among thepack ice. They penetrate into the high Antarctic such as Ross sea in
the neighbouring waters of the Barrier of the Ross sea (see John, p.
223). In this case, little piked whales are considered to show the Marginal sea type of the distribution. Taylor (1957) and others also show
the evidence that little piked whale are sometimes restricted to poolsof sea ice near the land in the Antarctic. With regard to the distri. bution of humpback whales, I have little data as to th~ distributional
characteristics of them in connection with the shape of the pack ice line,
and the concentration of humpback whales in some special sea condition in
the Antarctic has not been observed. It is a evident fact, however,they are divided into five more or less self-contained stocks of humpback
whales in the Southern Ocean (Mackintosh, 1942). The charts by Omura(1953, p. 1 to 102) and recent recovery of whale marks also furnish us
the general comprehension about the distribution of humpback whalesin the Antarctic areas in. summer season of the southern hemisphere.

FOOD OF BALEEN WHALES233

OCEANOGRAPHIC CONDITIONS

Surface water temperature
As the first step, the water temperature is often considered as a limiting facter to decide the distribution and the migration of whales. In fact,
the distribution of some baleen whales such as Bryde's whales has
close relation with the distribution of surface water temperatures(Omura & Nemoto, 1955). Here I would discuss the problem so as toconsider the aspects of the whales' distribution according to the oceanographic conditions.
With consideration on the catch and observation of the whalebone
whales, the range of temperature in the North Pacific in which eachwhalebone whale mainly inhabits, may be summarized as follows.
25°C- 8°C in August from Sanriku to the southern
Blue whale
waters of Aleutian Islands
Fin whale
30°C- 5°C from the east China sea to the Arctic
sea
Bryde's whale
30°C-20°C up to Sanriku waters
Sei whale
25°C- 8°C from Sanriku to the southern waters of
Aleutian Islands*
Humpback whale 25°C- 5°C from Sanriku to the Arctic sea
Of course, some wanderers call warmer or colder waters, and there must
be above remainder in the subtropical or the tropical waters. But it isevident that Bryde's whales inhabit in the warmest waters, and fin
whales show the broader range of the distribution as a conclusion. The
details will be discussed in the special part of each whalebone whales.
Profile of water temperature
The profile of water temperature is considered to clearly show thewhaling grounds. Each whaling ground has peculial profile type, andthe profile of the North Pacific differs very much from that of the
Antarctic area, about which my colleague Mr. Nasu will discuss in his
paper. Here I illustrate the examples in the Sanriku waters. As it isclear from the distribution of surface water, sei whales congregate in
the waters a little apart from the sub cold current of ' Oyashio ', andsei and Bryde' s whales are scanty in the waters where the gradient of
the profile of the water temperature is not 'sharply, or the gradient isvery smooth. These profiles of the water temperature also indicate thatsei and Bryde's whales congregate into the waters of high plankton
production.

* Japanese whaling expedition in 1958 found some 60 sei whales in the middle part of_
the Bering sea, but the water temperature was little different from 8°C.

234

T. NEMOTO

Whaling ground
The whaling grounds of baleen whales are divided into feeding area
type whaling ground and breeding area type (Nemoto, 1957). The former
grounds consist of many planktons and their patches or swarms of fishand squids, and the latter is generally located in the warm tropical or subtropical waters. The feeding area type whaling grounds have following
main oceanographical surroundings.
c

s

s

0

100

i{/({f:~il

5
200

0

5

0

5

10

5

m

5

10

~

o
0

0

10° 2o'c

300mFig. 32. The profiles of temperature, at stations in the off waters of Sanriku whaling
grounds in 1952 and 1955. P-Sei whales congregated and plenty area, C-Abovethe cold water subcurrent, S-Sei whales scanty, SP-Sperm whales congregatedand plenty area, E-East stations of 160°E and 180°E in 1955 through 40°N.
1. Continental shelf wa;t;ers and its adjacent waters. As I described in the previous
report (Nemoto, 1957, p. 80, 86), waters along the Alaskan continental shelf produce alarge amount of Thysanoessa inermis distributing and form a very favorable condition forwhales. T. inermis also spawn vigorously above the coastal bank, bottom layer, which is
directly suggest the horizontal cycle from the bottom layer to the surface strata where thelavae develop. Einarsson describe the inermis type of distribution of euphausiids, andThysanoessa inermis and T. raschii are considered belong to this type. These inermis
type euphausiids propagate along the continental shelf or within the shelf, and fin whales
congregate to feed on them. As I described in the previous report, with the upwellingcurrent and vertical oscillations by wind blowing toward the continental slope, the adjacentwaters to the continental shelf become a very productive area. The most typical whaling
ground of this type in the North Pacific situated along the continental shelf is the northwaters of the eastern Aleutian Islands, and Alaskan continental shelf. I can find further
this type of the whaling ground along the shelf, situated the Yamato Bank in the Okhotsk
sea and in the East China sea along the China continental shelf.
2. Boundaries of water-mass and water convergence. Along the boundary of different
water masses, the whales are usually feeding and migrating. In this waters of convergence,the vertical mixing of water and accumulation of food planktons bring very favorable
condition for baleen whales. The most typical illustration is observed in the off water ofSanriku in the adjacent waters to Japan (Uda, 1954). The cold current 'Oyashio' meets' Kuroshio ' the warm current in the area. One example of these water convergence in
the Sanriku water in summer in 1952 may be illustrated in Fig. 33. The Fig. 33 demonstrates the clear parallel between the water convergence and concentration of whales. There
are those heavy water convergences (Fig. 33 middle A, B, C) where many sei or Bryde's
whales had been observed. Swarm of birds and 'bonitoes are also so congregated to thewaters that whalers and fisherman can find whales from birds and bonitoes in the waters0

235

FOOD OF BALEEN WHALESThe boundaries of different water masses or currents make the cyclonic water movements,
in the center of which the most heavy concentration of foods is observed.
3. Upwelling and thermal Anticline. Upwelling occurrs in the high latitude of theearth as well as in the tropical and temperate waters. Upwelling carries nutrient fertilizers
into the sulighted zone. Cromwell (1956) describes the mechanism of tuna fishing grounds
145"E

155'E

• Sei or Bryde's wholev Sea bird..,.\,0
yY

y

40iv

38iv

38°

140'£

o~-,-~""'"""'==--r~-:-r<~;..-.,"""":::!=-""'=:::;~~-.:.:::;:-=:-.,~--.~~~;-;:;-:?T"Jr-rr,........s:::i

100

10°

200
5•

300L-..~-'-...L-~--'-~~~~~~~~..L_~~~_;:,._~~-L~---'--'~~

mFig. 33. The distribution of sei and Bryde's whales, surface water temperatureand vertical section of whaling grounds in the Sanriku waters in summer in
1952. Upper-Observation of whales, sea birds and fish, Middle-Distributionof surface water temperature distribution, Under-Vertical section along thedotted line in the upper figure from surface to the depth of 300 m. (basedon data mainly Miyazaki Otsuru & Watase, 1953).
and that it takes time for biological products to develop after waters has upwelled, sothat planktons are found displaced in down stream from the center of upwel!ing. This caption and his illustration (Fig. 2, a, b).are very important and satisfactory as to the generalcomprehension of whaling ground. consists of the upwelling. Because the whaling groundis also situated. a little apart from the center of the upwelling in the sea in general. ..

236

T. NEMOTOAs the whaling ground due to the upwelling is often made by affection of the shape ofsea bottom, and the ridge or Islands situated in the sea current often produce the upwellingsuch as the waters around South Georgia Islands.
Thermal anticlines also bring the' nutrient rich waters to the surface sunlight zone allowing plankton to develop (Cromwell, 1956).
4. Back waters and the center of the cycloniv movements. The food plankton, fish andsquids are also concentrated by currents into the center of the cyclonic movement or
backwaters (Ruud, 1932). These conditions are formed by two causes. One is made by
the current and the other is made by the shape of the land, gulf, bank, ridge, islands, andcape etc. The backwaters or the center of the cyclonic movement are found in the offwaters as often as in the adjacent waters to the land, but the former whaling ground are
not so stable as the grounds made by the shape of land islands etc. in the adjacent waters
to the land, and the center of the plankton concentration move or is transported bycurrent strength along the boundary in the off waters.
5. Whaling ground in the pelagic waters. Ruud (1932) describes there are large quantityof Krill among the ice far away from land or any known banks like the waters along theslope of the continental shelf and banks. The Antarctic whaling grounds belong to thistype of whaling ground, which have the close connection with the ice melting in the summer season. Of course the cyclonic systems round the coasts of the Antarctic continent
bear the possible making of whaling ground in some waters (Ruud, 1932), this type of
whaling ground is mainly due to the sun shine into the waters in the summer melting of
ice and the supply of the nutrient rich waters from the deep by currents. It brings forth
the vast propagation of plyto-planktons and successive congregation and growth of Eu,phaiisia
superba in the surface waters.

MOVEMENT AND MIGRATION OF WHALEBONE WHALES

Movement and migration of the whalebone whales are so vast problems
that they need many accumulatio~s of investigation and observations
before any definite conclusion is obtained. Still there are many evidence
for believing that the whales undertake regular annual migrations, or
temporary movements and migrations both in northern and southernhemispheres. As to terms 'migration' and 'movement' in this part, I
would refer again to the work by Mackintosh (1942, p. 237). The
term 'migration' is also used here to imply long annual journeys between the cold feeding grounds and temperate or tropical waters.
' Movement ' means, I would consider, regular or irregular local movement or journey according to some oceanographical conditions, feeding
and breeding conditions. The relationship between foods of the whalebone whales and movement or migration of whales should be discussed
to get the reasonable explanation for the subject as a first step. Next,
the result of the marking of whales gives us also the direct evidence
about the movement and the migration of whales. The marking investigations carried out in the Antarctic waters has been examined by Rayner(1940) and Brown (1955). These works show some clear characteristics
as to the migration of the whalebone whales in the Antarctic.
Distribution and migration of Sei and Bryde' s whales
Kellogg (1929) well describes the migration and movement of sei whales

FOOD OF BALEEN WHALES

237

in his paper, but that Bryde's whales were included in the sei whale
in his description. So, I would discuss again it carefully here mainlyon the data of the North Pacific by Japanese investigation.
Sei and Bryde's whales have been caught in the adjacent waters toJapan by shore whaling and other sei whales have been caught in thenorthern part of the North Pacific by Japanese pelagic whaling. Aboutthese whales, many investigations and marking examinations are made,and some results are already published (Omura, 1950; Omura, Nishimoto & Fujino, 1952; Omura & Nemoto, 1955 etc.).
Generally speaking water temperature seems to be important in limiting the migrations of the sei whale (Clarke, 1957). Sei whales are
considered usually never to call the Antarctic high and cold waters as
far as the waters along the pack ice before 1954 seasons by Japanese
Antarctic observations. After the year 1955, sei whales have beencaught and observed in a considerable number as reported by the International Whaling Statistics. In the 1955 and 1956 season, only 6 sei
whales were caught by Japanese whaling operations, while comparatively
many schools of sei whales had been observed on these days thoughthese sei whales had not been caught.
In the years 1957 and 1958, 133 and 1466 sei whales have beee caught
respectively by Japanese whaling expedition. The higher water temperature in these years than previous seasons, and the abundant cropof Parathemisto gaudichaudi (p. 164) might have caused such migrations of sei whales, while the further investigation oceanographically is
now under examination by Mr. Nasu of my colleague. The surface
water temperature shows a little higher value in the waters where sei
whales caught than the waters where other blue and fin whales caught,
and sei whales have never been among the pack ice. There is anotherevidence, however, the surface temperature is going down a little in
the late of February to March in the waters of Antarctic convergence,
when the almost all sei whales have been captured. This tendency isclearly given by Mackintosh in his figures (Mackintosh, 1946, b, Fig.
A-E). The surface water temperature in the waters along the packice also declines in March, still it is not so cold as in April. Sei whales
have been mostly found along the warm water current from the north,and not in the colder current originated in melting of ice from thepack ice. So, sei whales migrate to the high antarctic waters in theheight of the surface water temperature in general.
Sei whales have been caught in a considerable number by recent
Japanese pelagic whaling expeditions in the northern part of the North
Pacific too, because they produce the high production of whale meats ineach blue whale unit. The dominant catch of sei whales in recent years

T. NEMOTO

238

is observed in two areas, south east off waters of Kamtchatka Peninsula
and the south waters of the eastern Aleutian Islands. The latter waters
range from 49° to 53° North latitudes and 165° to 175° west longitudes.
These catches of sei whales are all limited in the south waters of
Aleutian Islands. The observation of sei whales in the Bering sea has
been few, and directly it is considered that sei whales never migrate
in the high latitudes and the Arctic sea like the Antarctic. The most
northern record of the reliable observation on sei whales in Bering sea

61 Stiwhales·x.. \x\x\_..... ~-- .....

"·

t:'°ih

<!>,

~

0

"'

oo

••

Distribution of foods of sei whales in the northern part of the North
Pacific and the observation of sei whales. x Single observations of sei whale, eCalanus plumchrus, O Calanus cristat·us, 0 Saury, !::,. Squids, D Euphausiids.
The surrounded area shows the waters where Calanus plunwh1·us is dominant.

is obtained in 1958. Some 54 sei whales are feeding in the Andyr gulf,
off water of Navarin cape on 4th August. Other 3 and 4 sei whales
also described in the near waters in the same ranges as described inFig. 34. I have 8 other single observations in the Bering sea whichcontain less than 5 sei whales at each position. Above recent reliable
informations also endorse the tendency that few sei whale migrates tothe marginal sea as I state in the part of distribution of whales according to the shape of the sea. The migrating season of sei whales

FOOD OF BALEEN WHALES

239

in the waters is considered a little earlier in the eastern waters thanin the western waters. In the former waters of southern waters of theeastern Aleutian Islands, the main sei whales migrate in the middle ofJune to feed the vast amount of Calanus plumchrus and C. cristatus.
As the favourite food for fin whales, Calanus cristatus also becomesdominant a little earlier than Calanus plumchrus and the height of C.
plumchrus later in general (Vinogradov, 1956), fin whales are considered
TABLE 28. CATCH AND STOMACH CONTENTS OF SEI WHALES IN
THE WEST WATERS OF THE NORTHERN PARTOF THE NORTH PACIFIC IN 1953
Stomachcontents

June

July

Aug.

Sept.

r-''~

,,,---''~

~-~

~~

lst

lst

lst

lst

C. plumchrus
G. pl. & Squids
Euphausiids
Saury
SquidsEmpty
Uuknown

3rd

3rd

2nd

2

7

1

1

1

1

1

3rd
11
3
2
2
8
42
2

2nd

3rd

3

1

1

4
2

3

TABLE 29. CATCH AND STOMACH CONTENTS OF SEI WHALES IN
THE EAST AND WEST AREA OF THE NORTHERNPART OF NORTH PACIFIC IN 1954
West
Stomachcontents

May

June

July

~~

~~

~~

lst 2ndlst 2nd 3rd

2nd
C. cristatus
C. plumchrus
C. cri. & Squids
C. sp.
Euphausiids
Squids
Empty

East~----~ ....

3rd

Aug. May

June~

lst 3rdlst 2nd 3rd
3

2

2
13

1
2*

1*

9*

10* 20*

2*
1

1
3

1

1

19
* These species are considered Calanus plumchrus from some collected
samples, but no exact observation on board is available.
1

8

to migrate to the said area earlier than sei whales. Sei whales also
distribute in a little apart from the waters where other fin and blue
whales' school are feeding. This suggest the segregation of each species
in the feeding grounds, which is partly due to the different distributionof their favourite foods directly. Another explanation for the above
fact is 'balance' or distributional power among the whales.
Above migrational season is well illustrated in Table 28 and 29. Manysei whales were caught in 3rd decade of August, but few number was

T. NEMOTO

240caught in preceding decades in 1953 in the west areas, off waters ofKamtchatka peninsula.
In 1954, sei whales were caught from the 2nd decade of May feedingon Calanus cristatus and squids, and from the lst decade of June sei
whales are considered feeding on another Galanus plumchrus. Sei
whales become abundant in July in the west waters, on the other hand,considerable number of sei whales are caught in the 3rd decade ofJune in the east waters. These sei whales are feeding on Galanus
plumchrus as I described in previous report (Nemoto, 1957, p. 53).
Sei whales are feeding on squids (Ommastrephes sloani pacificus) andsaury (Cololabis seira) besides copepods. This fed positions are illustrated in Fig. 34. The squid distributes mainly in the Kamtchatka sideand saury too. As saury also distributes in the American side (Schaefer& Reintjes, 1950), and sei whales' feeding on saury in the eastern parts is
North

Fin
Sei

Middle

Fin
Sei

South

Fin
Sei

Month

F

M

A

M

A

s

0

N

D

Fig. 35. The whaling seasons of fin and sei whales along the coasts of Kurile
Islands by Japanese and Russian operations including the seasons before 1945.
Black-main season, White-range of the whaling season.

also probable. Squids and saury in their turn feed on Calanus plumchrus. The stomachs of squids and saury in the waters are satiatedwith Calanus plumchrus. The following relations are obtained by above
discussions.
Close

Sei whale---~Calanus plumchrus
Subordinatet---~Saury& Squids

Close

The Calanus year and Euphausiid year make some delay and theearly migration of blue and fin whales as I said in the preceding part. But
the Calanus cristatus and euphausiid are not so favourable for sei
whales in the northern part of the North Pacific, sei whales nevermigrate so early in Galanus year.
Sei whales in the northern part of the North Pacific must have close
relation to those of Kuril waters, Hokkaido and Sanriku waters. But

FOOD OF BALEEN WHALES

241

no mark hit in the adjacent waters to Japan has been recovered in thenorthern part of the North Pacific and vice versa. The facts that thecomparatively many marked sei whales in the adjacent waters to Japan
have been caught in the water suggest that they migrate to the waters
regularly to feed on foods, and the group may be different from thosein the northern part of the North Pacific (the term group is not used
in a strict sense).
The catch of sei whales in the Kuril waters which lies between Japanand the northern part of the North Pacific, vary in each localities of
the North and South Aleutian waters. In the northern part of theKurile waters at about 50° North latitude, number of sei whales caught
were not so large that the typical migration of the whales to the waters
has not been obtained. From the catch of pre-war seasons before 1945
by Japanese and after the war by Russian operations, the height isobserved only in August and of short duration, and very few sei whales
have been caught in July and September. Along the coast of Middle
K urile Islands, sei whales are also scarce, but they migrate to thewaters a little earlier than the north waters of Kurile Islands. Stillfrom July to the middle and the late of August the south Kurile Islands
show nearly the same tendency as the Hokkaido waters. Sei whales
migrate to the waters from June, and main herds come between the
middle of July and the middle of September. Some sei whales also
had been taken still in November in the pre-war seasons. Among thesei whales swarming in the South Kurile Islands, some sei whales passthrough the straits between Kurile Islands to the Okhotsk sea. Though
in the pre-war seasons before 1945, Bryde's whales had not been distinguished from sei whales by Japanese investigations, it is safe to
say that all sei whales in the waters are real sei whales (Balaenoptera
borealis), and they never include Bryde's whales (Balaenoptera breidei)
or include very few of them. Because Bryde's whales are warm water
living whales, and they are considered never to migrate to the northand middle K urile waters or mainly distribute within the range of surf ace temperature more than 20°C (Omura & Nemoto, 1955; Omura 1959).
Recent Russian investigations also report the occurrence of Bryde's
whales in the Kurile waters (Kleinenberg & Makarov, 1955), but it isconsidered to be restricted to the south waters of K urile Islands according to recent Japanese investigations.
In the adjacent waters to the north east part of Japan proper Sanriku and Hokkaido waters, Bryde's and sei whales have been examinedfrom the year 1952 at the landstations by the investigation mainly onbaleen plates and ventral grooves of whales. The result in 1953 is discussed by Omura & Nemoto (1954), and the fact that considerably many

242

T. NEMOTO

Bryde's whales are caught in the off waters of Sanriku suggest thatthe result obtained by the year 1951 were all unreliable to get thecomprehension of the migration and the distribution of sei whales in thewaters.
In the seasons before 1945 some whale already noticed the occurrenceof Bryde's whales, as they called 'Nitarsi' the vague sei whales (apparently Bryde's whales) and 'Triangle sei whale'. The baleen of thewhales are coarse and it was never bought so much high price as real
sei whales in the Sanriku landstations.
As the catch of baleen whales in the Japanese waters is permitted from
May to October, sei and Bryde's whales have been caught by recent
operation in the adjacent waters as described in Tables 30 and 31.
TABLE 30. NUMBER OF SEI WHALES CAUGHT IN THE ADJACENT WATERS
TO THE SOUTH EAST JAPAN PROPER FROM 1956 TO 1958
Sept.
Oct.
Aug.
May
June
July
~~

1956
1957
1958

40S
40N
40S
40N
40S
40N

,-----''-----..

~~

~-~

~

,,-----'~

1
3
5 20 36 70 43 19 3 2 41 13 5 4 7 5
6 65 169 43 13 22 20 23 33 37 32 23 18 28
3 7 11
3 43 51 36 15 1 2 4 6 14 15 4
1 1 2 38 18 11 9 13 46 14 18 31 3 11
38 21 67 1 4 11 2
2 3 49 42 26 37 20 3 2 4
1 2 1 7 9 31 59 46 12 32 9 22
5 6 6

TABLE 31. NUMBER OF BRYDE'S WHALES CAUGHT IN THE ADJACENTWATERS TO THE SOUTH EAST JAPAN PROPER FROM 1956 TO 1958
May
1956
1957
1958

40S
40N
40S
40S

3
1

2

2

1

Aug.

July

June
8

2
3
8 6 5
2 18 19

1

1

Sept.
1

2

1

1
1
5 12
9 74 48 5

2

40S means the South waters of 40°N latitude and 40N the North waters of 40°N
latitude.

From the Tables, Bryde's whales have been mostly caught in the south
waters of 40° north latitude, and sei whales are more abundant in
the latter part of the seasons, some sei whales are captured in thefirst decade of May in the south waters. But generally speaking sei
whales become dominant in the late of May to the late of June in thesouth water, but few Bryde's whales have been caught in May. Only 1
Bryde's whale is caught in 1957 and 2 Bryde's whales are caught in May
in 1958 (see Table 31) which show the early migration of Bryde's whales
to the Sanriku waters. The main herd of Bryde's whales migrate to
the Sanriku waters from the late of June, and the height is observedin July and August though there are some annual variations of

FOOD OF BALEEN WHALES

243

migrations among the years (see Omura & Nemoto, 1955, Table 1) as
illustrated in Table 32.
Of course, the annual change of the way of whaling operation isprobable and the number of Bryde's whales in each local waters also
varies annualy. The catch of Bryde's whales in 1955 shows some 85
Bryde's whales which is comparatively high value from 1953 to 1957.
The catch of Bryde's whales in 1958 demonstrates the tremendous
number of 298 whales, 179 of which are caught in the Sanriku waters.
Another catch of Bryde's whales in the adjacent waters is observed in
the waters of Oshima, Wakayama prefecture, and the catch of Bryde's
whales in each decades in the Oshima waters may be ref erred to thepreceding Tables 17 and 18. Bryde's whales in recent years have been

J
~ 30

0

-5c:

10

0

~.

:'

0 20

"

I

•'
''

=>

0

10

0

I

'"

E

<{

Ql

'

Si
'
'
l

'

I

I

I

I

\

I

, '

'

I•'
,.

,.

5

10

15

20

0

,," ..

25

(i;
..0

'--·

''

E

"

z=>
30

Date

Fig. 36. The relation between the catch of Bryde's whales and the amountof anchovy fished at the landstation of Wakayama prefecture along the
Pacific coast in June in 1958.

caught mainly from the late decade of May to June. This migration of
Bryde's whales bears close relation with the abundance of anchovy(Engraulis japonica) in the off waters of Wakayama. In the earlier
season, Bryde's whale are feeding on a euphausiid (Euphausia similis)
which distributes in the off waters of 20 miles from the land in general(Honjo, 1957). Later the main herds of Bryde's whales in the Wakayama
waters are feeding anchovy. The relation between the amount of theanchovy captured and the catch of sei whales is illustrated in Fig. 36,
which indicates that anchovy has the close bearing on the migrationof Bryde's whales. Anchovy is fished in the waters mainly from April
to November, and comparatively scarce from December to March. The
most abundant catch of anchovy does not always coincide with the244

T. NEMOTO

height of the migration of Bryde's whales, however, the catch of Bryde's
whales is increasing with the increase of anchovy. The amount ofanchovy fished in April and May in 1958 is very scarce, but the shoalsof anchovy come from the early of June and become very abundant in
the middle of June considered from the catch of anchovy fishing. Although the amount of anchovy shows only the part of anchovy in thewaters, there is a close parallel between the catch of anchovy and
Bryde's whales. Anchovy in the waters, fo its turn, is feeding on thewarm water living copepods, belonging to the Eucalanus, Sapphirina,
Oncaea, Candacia and Calanus. These copepods are considered to
distribute in the scattered condition, not to aggregate into swarms or patchin the sea. Bryde's whales are swollowing type whales and can nottake the scattered copepods in the natural sea condition. If the copepods
are fed by swarming anchovy, the latter make growth and become the
TABLE 32. NUMBER OF BRYDE'S WHALES CAUGHT AND IDENTIFIEDALONG THE ADJACENT WATERS TO THE JAPAN PRORER
Locality

1955

1956

1957

1958

Sanriku & Hokkaido
Oshima (Wakayama)
Goto (West Kyushu)
Total

57
26
2
85

24

41

2
26

3
44

179
72
47
298

favorite foods of Bryde's whales. Especially Sapphirina species are very
famous as a indicater of 'Kuroshio' current and Japanese fishermensometimes seek their fishing ground of bonito (Katsuwonns pelamis(Linne)) by the water colour containing these Sapphirina species. It isreasonable that the whaling ground of Bryde's whales lies in the nearwaters of bonito fisheries in these Wakayama waters, because Bonito
also feed on anchovy very often in the adjacent waters to Japan (Hotta& Ogawa, 1955).
Bryde's whale----+Anchovy----+Calanus spp.
/
Candacia spp.
Warm water living
Sapphirina spp. copepods.
BonitoOncaea spp.
etc. )
1

Above relation is observed in the off waters of Oshima, Wakayama
prefecture, and this tendency will be maintained to Sanriku waters too.
At Oshima in 1958, I noticed about 10 new open pits on the surface ofbody of the whale besides many healed scars. The open pits are notso fresh as they are observed in Bonin waters (see Fig. 6 in Omura,Nishimoto & Fujino, 1952). But the open pits are all more fresh thanthose observed in the northern Pacific waters of Sanriku waters. ThisFOOD OF BALEEN WHALES

245

healing stage of the scars is considered to closely resemble to Fig. 7,
Plate 36 illustrated in the paper by Mackintosh & Wheeler (1929). Thisis the very initial stage of healing frgm the open pits which is usuallyfound in the Bonin and South African waters. The fact clearly indicatesthe new coming of Bryde's whales to the Wakayama waters from thesouthern subtropical waters at that time.
From the catch statistics of the seasons before 1945, sei whales (apparently including Bryde's whales in summer seasons) had been caught
as illustrated in Fig. 37. Though there are some vague catch in theearly spring season and winter the main catch is divided into two heightsfrom winter to spring and from spring to summer. Kasahara (1950)
deemes the fact very simply, and summarizes them into one figure,which does not demonstrate the two peaks of the catch.
The former height of the catch is very interest, but the species is notcertain, however, it is probable that sei whales (Balaenoptera borealis)
come to the waters in winter season, and the latter height is undoubtedly
TABLE 33. SURFACE WATER TEMPERATURE RANGE OF THE
CATCH POSITION OF BRYDE'S WHALES IN THE
SANRIKU AND HOKKAIDO WATERS
Water temperature range, C
Year

14-16

16-18

18-20

1953
1956
1957

1
3

1
1

6
7

20-22

22-24

24-26

27
6
5

14
5
19

7
9

26-28

7

the catch of Bryde's whales. One of the explanation for above fact isthat sei and Bryde's whales are considered to migrate to the Boninwaters also separately. According to Omura & Fujino (1954) sei whales
are taken from November to April in the Bonin Island waters, and thecatch is mainly composed of Bryde's whales in May and June. Omura& Fujino (1954) and Omura & Nemoto (1955) already state the occurrences of Bryde's whales only in summer. Their northern migrationmust be different from sei whales. On the other hand, there is one
contradiction to the assumption. Andrews (1916) examined sei whalesat the landstation of Oshima in April in 1910, and his descriptions
are apparently those of sei whales (Balaenoptera borealis). To myregret, there is no explanation as to the ventral grooves of sei whalescaught at the Oshima landstation. But he examined carefully thedistinguishing points between sei and Bryde' s whales in the latterpart of his paper, and he further consideres Bryde's whales is distinct
from sei whales, so it is probably safe to say that the sei whales
described in April at Oshima, Wakayama prefecture, are real sei whales,

246

T. NEMOTO

and the occurrence in 1910 in Fig. 37, also shows the separation of
the migration of sei whales in winter seasons. As illustrated in Fig. 37,
there are clear two heights of the catch in 1911, 1919 and 1921, which
are probably due to the above migrational segregation of sei and
Bryde's whales in the off waters of Wakayama.
In 1921, the vague catch of sei whales is described as shown in Fig. 37,
but no sei whales had been caught in the winter season from January
to March after the year 1926 except some whales caught from October
to December. The water temperature still remains 20°C in winterseason in the off water of Oshima, so the catch of Bryde's whales in
the winter seasons can not be neglected perfectly. As a conclusion, thesummer catch of sei whales in the waters are apparently considered
5
1926
10

J?0 5
i 40
0
:. 30

10
1932

i----..._~~~~~~~~~~-----1

10

1919

..c

z 20

1934

10

'1940

5

1941
1942

5

1943

5

E.

10

A

s

0

N

D

Fig. 37. The catch of sei whales (including Bryde's whales) in the adjacent waters
to Oshima, Wakayama prefecture from 1910 to 1943. Solid lines indicate theprobable catch of Bryde's whales and dotted lines indicate the probable catch ofsei whales. The upper right shows the catch in 1922.

to be Bryde's whales, though the whales were described as sei whales.
In the seasons before 1945, some sei whales had been captured at
the landstations of west Kyushu waters from June to September. Alsothese sei whales have been caught after the year 1945, but recent
investigations prove that these whales are all Bryde's whales. Omura& Fujino (1954) state the sei whales measured at Okochi landstation in
Tsushima before the year 1945 season are all Bryde's whales considering
the extension of ventral grooves on the body. Along the west coast of
Kyushu, Bryde's whales are migrating to feed on sardin and anchovyin the summer season, and the northern limit in the west waters ofJapan is considered to be 35° North. Bryde's whales are considerednever to penetrate into the Japan sea.
In winter, as the west Kyushu waters is still warm by the ' Tsushi-

FOOD OF BALEEN WHALES

247

ma' current and their favorite food anchovy is abundant in somewaters, some Bryde's whales may pass the winter in the waters though
there is no evidence if the sei whale in the winter season is Bryde's
whales or not. Some whaler said 'Sendai iwashi' meaning 'Sendai sei
whale' had been caught in the west Kyushu areas. This whale may
be sei whale (Balaenoptera borealis), because Sendai is the city of
Sanriku prefecture where many sei whales (Balaenoptera borealis) havebeen caught by whaling operations.
As a conclusion the water temperature range is important for thewarm water living Bryde' s whales. As I discussed in the previous
column, Bryde's whales have been caught mostly in the surface watertemperatures more than 20°C. Of course, some yearly change among
the dominant occurrences of Bryde's whales in the water temperatures
range is observed as illustrated in Table 33. The catch of the year
1956 does not show the typical high water temperature range, but the
number of Bryde's whales show the smallest number when the comparison is made with recent other years. It is evident, however, that
Bryde's whales are migrating in the water temperature more than 18°C,
and never to call the colder waters under 15°C in general.
The whale. marking on sei whales began in the spring of 1949 in the
Bonin Islands and in the Sanriku and Hokkaido waters, and has been
conducted every year in the North Pacific. Recent marking also has
covered the northern part of the North Pacific and the recovered marks
are listed in the appendix. I would classify these marking data withconsideration of_ marked and captured season, marked and captured
whaling grounds and lapse of the year. The whale marking in the
Bonin Islands waters had been carried out between 1949 and 1952 and92 sei Bryde's whales had been marked and 6 of them captured. Threemarks were recovered in the same Bonin waters. The two marks were
found somewhat west waters of marked position after the lapse of 1day, and the last mark was recovered from the waters about 20 miles
north waters of the marked position after the lapse of 12 days. With
the consideration of the swimming direction and the catch of whales in the
Bonin Island waters, Bryde's whales stay in the waters from the earlyof May to July and gradually migrate to the northern waters from thelate of May.
Other 3 marks hit in the Bonin Island waters have been recoveredfrom the whales caught in the adjacent waters to Japan Sanriku waters.
One mark was recovered in the same year of marking. The whale wasmarked on 8th May, 1950 at 26°-43'N and 142°-40'E, and captured in theoff waters of Sanriku at 37°02'N and 143°02'E after 69 days lapse. The
other mark is recovered from a sei whale (The baleen plate is examined,248

T. NEMOTO

but they say the plate is a sei whale, Balaenoptera borealis. The species
should be corrected to be Bryde's whale by the recent investigation ofa whale of the same school. The baleen plate must be mistaken), andthe third is recovered from a Bryde's whale caught at 38°10'N and
145°20'E after the lapse of 8 years. These 3 marks prove directly the
migration of Bryde's whales from Bonin Island waters to the Sanriku
waters. The Bryde's whales usually call on the Bonin Island watersfrom the late of April to July and one part of Bryde's whales go northas far as off Sanriku waters, but one part remains longer in the Boninwaters (Omura & Fujino, 1954, p. 101) according to the observation bymarking cruises between the late of June and the early of July in 1952

775
35

• :,,·~.f, l... '! i ~ F

z5 2

25

·:.~:G'\'-r'1'*0.-----'----.,,'3~0"'"·-----'-'--rh->o_ _c___,.,1so' IJ""s"""·---,.ld+-o=·--1.-1s=·,.........-'1so'

Fig. 38. Left, Schematic illustration of migration course of Bryde's whales in
the adjacent waters to Japan. A, B, C, D-Recent whaling grounds of Bryde's
whales, E-Catch position of Bryde's whales before 1945, F, G-Probablewhaling grounds of Bryde's whales in the seasons before 1945. Dotted lines
show the northern range of the distribution of Bryde's whales in the adjacentwaters to Japan. Right, The recovery of whale marks bit in the Bonin Island waters and recovered in the Sanriku waters.

when some 74 sei whales (evidently Bryde's whale) had been observed.
The comparatively many Bryde's whales were observed swimming tosouthern direction suggesting some of them may be feeding aroundthe Bonin waters still in summer. The water temperature was very
high showing from 28°C to 29°C in the waters at that time. There issome data of swimming school of Bryde's whales obtained in the Bonin
Island waters. The single Bryde's whale predominated and the largest
school consisted of 5 Bryde's whales. The single occurrences of whales
mean to some extent the migrational special feature that they are dueto the initial stage of the migration.

249

FOOD OF BALEEN WHALESIn the northern part of the North Pacific, the number of sei whales
in a school have been observed in 1954 as shown in Table 35. Though
the observations number is not so sufficient, the sei whale school in theearlier time of the season consists of single swimmer, on the other handthe observation in July prove that more schools consist of two sei whales.
This fact suggests that some sei whales make rendezvous in the feeding
ground and it is probable they return to the south for mating.
The summarized data of whale marking in the Sanriku and Hokkaido
are given in Fig. 39. The 0 year group has three individuals, which
demonstrates the westward movement from the off waters to the rather
TABLE 34.

NUMBER OF SEI WHALES* IN EACH SCHOOL IN
THE BONIN WATERS IN 1952

No. of whales
No. of school

1
12

2
4

3
3

5
2

4
1

The whales are described as sei whales by lack of observation.

* These sei whales are considered to be Bryde's whales.

TABLE 35. NUMBER OF SEI WHALES IN A SCHOOL OBSERVED BY
JAPANESE INVESTIGATION IN THE NORTHERN PARTOF THE NORTH PACIFIC IN 1954
Number of whale in a school--~---

~

Month

1

2

3

4

May
June
July
Aug.

4
12
19
9

3
41
6

14

6

5

6

4

coastal waters. The mark (No. 3782) hit on 7th July of 1953 at about
42°N latitude is recovered on 12th September at 39°N latitude, andanother mark No. 2675 hit on 2nd September is recovered on 2lst
October. These two marks show some case that sei whales (in somecases, occurrences of Bryde's whales are probable) are feeding in theoff waters in summer, and then go to the coastal waters in autumn.
From the 1, 2 and 3 year groups, two sei whales marked in July andAugust are captured in a little more south waters in the early dateJuly, and two sei whales marked in September are caught also in the
more coastal adjacent waters, than the position they were marked.
Two sei whales marked in September are also caught in the nearwaters of the marking position in September. The tendency that whales
come back to the same water in the same season of the year is partly
demonstrated by these 1 to 3 years groups of sei whales.
4 years group or more elapsed group also endorse above tendency as
shown in C of Fig. 39. ·Two September groups are recovered in the

250

T. NEMOTO

near water after the lapse of 5 years. But another three marks
marked in September are recovered in the far coastal waters. The
marks, No. 2819 and No. 86 marked in July and September respectively
are caught in June after 4 and 6 years. Two 5 and 6 years groupcross the waters to the west coastal waters too. These marks all prove
the general tendency that sei whales are feeding in the boundary ofwater mass between ' K uroshio ' and ' Oyashio ' in the Sanriku andHokkaido waters. If the heavy 'Siome' (Current rip) moves by someoceanographic surroundings affecting the .sea condition of the whaling
ground, sei whales also move very rapidly to the next favorable feeding area where the heavy 'Siome' is occurred. A good example is obtained in 1956. From May to June, comparati.v.ely many sei whales
had been caught in the off waters of Sanriku, but the center of catchgoes to the north and few sei whales are caught in the Sanriku waters

E I 2'

I 6

150' .

I 2

I 6

I O'

E

Fig. 39. Marking results of sei whales in the Sanriku and Hokkaido waters by
Japanese investigations. Black symbols show the recovered positions. Opensymbols show the marked positions. Crosses cutting arrows show the elapsed
years. Cross-June, Triangle-July, Square-August, Circle-September, A-0
year group, B-2 and 3 years groups, C-groups more than 3 years.

in July. The typical moving of 'Shiome' is observed between June
and July. The catch of sei whales decreases in number in the late ofJune when the 'Shiome' declines, and sei whales may scatter to feed
their food. The sei whales are heavily feeding on Euphausia pacijica,
Ommastrephes sloani pacijicus in the ' Shiome ' in the Hokkaido waters
in the first of July. Again, the developed 'Shiome' down declines in thelate of July and the center of the catch of sei whales go to the south in
the late of July. These movements of the whaling ground can be explained by the intensity of Oyashio and Kuroshio current and their
movements as a conclusion.
In the northern part of the North Pacific, two marks are recoveredfrom sei whales (Balaenoptera boreali{J..) after the lapse of 4 years. The
sei whales are marked in June along the continental shelf south of

FOOD OF BALEEN WHALES

251

Unimak Islands. When they are marked, they apparently were considered to feeding Calanus plumchrus from the observation of othercaught sei whales. The sei whales taken in July in 1958 are also feeding on Calanus plumchrus but in the more off and western waters.
Though there has been no satisfactory explanation for the removal of
the whaling ground for sei whales consists of Calanus plumchrus, theextention and strength of warm current from the south and the colder
shore and northern waters make such a feeding grounds.
There are two evident peculiar features in the catch of sei whales in
the Antarctic. That the female is always dominant at the high rateis one, and the catch of mature whales are exceedingly dominant is the
TABLE 37. CATCH OF SEI WHALES IN THE NORTHERN PART OF
THE NORTH PACIFIC IN THE EAST AND WEST SIDE IN 1957
Decades
May late
June early
June middle
June late
July earlyAug. middle*

West

East

~

~

Male

Female

5
9

7
10

22

Male

Female

16
5
33

20
2
26

10

* Including 1 male caught in late August.
TABLE 36. CATCH OF SEI WHALES CAUGHT IN THE ANT ARCTICWATERS BY JAPANESE WHALING OPERATIONS IN 1958
Antarctic area

v

IV

VI

~
<!.)

....

Sex

....<!.)....,;:l....,;:l

:;s

.§

:;s

10
19

1

16
50

ro

Male
Female

ro

s

<!.)

....
;:l
....,
ro

<!.)
....
;:l
....,
ro

....<!.)....<!.)....,;:l

;:l
....,
ro

Ii

ro

s
s

1
1

114
257

1
9

s

- :;s -

~

c

~

0

c
c
::i
6
8
..>::

....<!.)....,;:l
ro

:;s
234
714

....<!.)....,;:l
ro

s
s

2
18

c

~

0

c
c
::i
..>::

Total
385
1076

other. Among the Japanese catch in the Antarctic in 1957 and 1958,
females and mature sei whales are very dominant. In 1957, only 4 immature
males and 21 mature males, 5 immature females and 103 mature femalesof sei whales were captured by Japanese expedition. Matthews (1938a)already noticed the female predominated tendency and thinks one reason
for the fact is due to the selection of large sei whales for capture. Kasahara (1950) also subscribes his opinion. But the sexual segregation in
the migration course also should be considered to explain the fact successfully, because from the sex ratio of foetus does not show suchfemale predominated tendency. As there is another interesting tendency

252

T.NEMOTO

like above segregation in the North Pacific, I would refer to the resultsin the North Pacific here. Omura (1950) illustrates the sex ratio of sei
whales caught in the Kurile and Hokkaido areas in past 18 years. Of
course, there must be some trespassers of Bryde's whales in the statistics, but the number is considered very few in above two local waters(Omura & Nemoto, 1955). Males of sei whales are predominated in the
Kurile waters, on the other hand, females are more numerous than males
in the Hokkaido waters (see Table 36, Omura, 1950). Kasahara (1950)
also consideres there is the segregation of migratlon between male andfemale of sei whales, and males go to the further northern waters if
it is simply considered. In the northern part of the North Pacific,
males are always predominated in the western part, off Kamtchatka andsouth of the Komandorskiy Islands. I would consider these facts aremainly due to the later season of whaling. This illustration is given
in Table 37, which show the tendency of male predominating in thelatter half season of July and August.
Fin whales
Northern part of the North Pacific. Fin whales have been considered
to be a long migratory whale. The recovery of whales' marks in thesouthern hemisphere proves the long migration between the Antarctic
cold waters and subtropical waters of Brazil and South Africa (Brown,1954). Like the case that the sword of a sword-fish (Xiphias gladius)
was found in the dorsal flesh of a blue whale in the Antarctic (Ruud,
1952), a sword of a sword-fish was found in the meat of a fin whale
caught on 19th July in 1954 in the adjacent waters to Aleutian Island.
The fin whale was caught at 54-35N, 165-35W longitude, where thePacific sword-fish also never inhabit. in such cold waters as Aleutian
region. This indicates the migration of a fin whale between the northernpart of the North Pacific and the subtropical waters of the Pacific.
'
In the northern part of the North Pacific near Aleutian Islands, fin
whales have been caught from May to September by Japanese andRussian expeditions. The catch has been observed along the Aleutian.
Islands, along the Alaskan continental shelf and Kamtchatka coast.
Generally speaking, fin whales come from the southern waters alreadyin May in the west part of the North Pacific. The height of Calanus
cristatus and euphaussiids, Thysanoessa inermis change their roll inthe middle of the season, and the fin whales usually migrate to thenorth or the east waters to seek the food from July in 'Calanus year'(Nemoto, 1957, p. 79). The catch height in the west waters of off
Kamtchatka is considered to be in June (see Fig. 23 Nemoto, 1957) and
fin whales become scarce in August owing to the scanty supply offoods in the waters. The height of Calanus cristatus shows some local

FOOD OF BALEEN WHALES

253

differences according to the latitudal locality in the northern part of
the North Pacific as stated in the former part.
In the southern waters of Aleutian Islands, Calanus cristatus become
dominant already from May, but in the northern waters, it become
a little later than May. Fin whales follow the height of their food, andif the food is sufficient they stay there for comparatively long time.
This cause surely the delay of migration (in this case movement ismore suitable) of fin whales to the north waters of the Bering sea,
especially in the North waters of Kamandorskiy Islands and in the offwaters of Anadyr gulf. The temporaly prosperity of swarming fish
such as capelin and Alaska pollack also attract many fin whales, theexamples of which are observed in 1957 and 1958. The waters where
Alaska pollack, was abundant in 1957, does not attract fin whales in1958 owing to the scarcity of Alaska pollack. But comparatively many
fin whales go to far north to feed on abundant foods of capelin in 1958.
Still, other fin whales feed on planktons in southern waters near AleutianIslands. This will partly demonstrate that number of fin whales are
restricted to the waters according to the abundance of foods in thewaters, and excessive number of fin whales may call other waters tofeed on their food.
Marking results in the North Pacific. The whale marking researchcommenced in 1953 in the northern part of the North Pacific, and has
been succeeded since then.
With regard to the result of marking investigations on the fin whalesin the northern part of the North Pacific, the periodical report andsummarized reports (Omura & Kawakami, 1956; Kawakami & Ichihara,
1958 etc) discuss the problem to soine extent. Here, I would make thediscussion mainly considering the seasonal migration and the movementof fin whales.
The recovered marks are classified into year and seasonal groups as
illustrated in Fig. 40. In the earlier season, the whaling operation
has been conducted mainly in the southern waters, and gradually covered
the North waters. As this directly indicates the early finding of marks
only in the southern waters, no marks has been recovered in the northwaters in the earlier season of whaling when no fin whales has beencaught in the north waters. It should be considered that fin whales notalways go to the north from the spring season to the summer season
because many fin whales have been caught in the southern waters of
the Aleutian Islands in the high summer season of the North Pacific.
My preliminary discussion based on the seasonal movement is as follows.
1. From May and June, the general tendency of fin whales migrating
north is observed. Fin whales come to the western waters of the south

254

T.NEMOTO

waters of Aleutian Islands, near waters of Komandorskiy Islands fromMay. These two marks hit on fin whales in the north waters of theeast Aleutian Islands in August and September have been recovered inMay, suggesting that these fin whales may migrate to the east and northwaters again. The marks connect the east and west groups of fin
whales in the northern part of the North Pacific in appearance. Twomarks (J. 6042 and J. 6834) are recovered as the May group, but theMark (3213) hit in May in the middle south waters of the AleutianIslands is recovered in July in the said waters.
The Mark (J. 6060) in Fig. D. hit in September in the northern watersof Aleutian Islands is found in the western waters of the Near Islands
in June, which indicates the same tendency as May group in Fig. A.
2. The marks hit in the north waters of the eastern Alutian Islands in
September and August, the rather late season, are recovered in the south
waters of the eastern Aleutian Islands. This also indicates the northward movement from the early season to the middle and late season of
whaling demonstrated by three marks (J 6799, JS 6987, J 5998) in Fig. D.
3. After the lapse of the time more than 8 months or in the next
year after the hit, the same month group show the capture position
situating the very near position of marking position. For example, themarks hit in August, rather in the late season, are recovered in Septemberin the near position of markings (Fig. C). The marking and recoveringin July and in August respectively also show the same tendency (Fig. B).
Above results endorse the consideration that fin whales migrate to
the same waters in the same season of the year as a rough conclusion.
The main reason for the tendency is due to the general plankton cropin the same time of every year though there are some yearly change
is observed. If there are any changes of oceanographical condition, or
amounts of planktons organisms, the different migration of fin whales
will be obtained.
4. The 'dispersal' of the whales also should be considered. The term
'dispersal' is used to describe the ultimate movement of whales east
or west from the position in which they are marked by Brown (1954,
p. 358-359). He made very excellent consideration on the problem in
the Antractic on the dispersal of whales. Here I would state somedifferent conditions between the Antractic and the North Pacific whaling
ground at first as regards the dispersal of whales. The whaling groundin the Antractic is situated along the pack ice surrounding the Antractic
continent. Of course, the currents of the Weddle sea, Ross sea and South
Shetland sea etc, make the drift of euphausiids into the off waters(Ruud, 1932) or bring forth the constant crop of plankton in the offwaters and show the strong latitudal distribution of baleen whales as

FOOD OF BALEEN WHALES

255

180°

170°E

A

19: Moy (J. 6042)

51°N.12 Mo;(3213)

57°N

170°W

"'
55°N

53°N

(J~\' .

59"N

~,

57°N

(JS. 6923)

c6,__,939~)~~•" /255°N/[.-JS.

53°N"O>...,.
B

\

52°N

.i. • "

.....

D

so N
0

51°N

(3243)

6987)
170°W

50°N

11. Aug.

55°N

54°N

60°N

8. Aug.

'8. July(J. 6511)"

19. July (JS. 7720)~,\
E

6. July (J. 6506).

2. Sept.
2. Sept.~J. July
, .,@~uly\,
24 Aug.
170°E
~

_180°

0

1zo w""'"

Fig. 40. Marking results by Japanese marking research in the nothern part of
the North Pacific: A-May group after the lapse of time more than one year.
B & D-June and July group after the lapse of time more than one year. CAugust and September group after the lapse of time more than one year. EJuly group within the same year of marking, 0 year group. F-August & September group within the same year of marking, O year group: Open symbols show
the marking position and Solid Symbols show the recovering position. The shortcrossing lines show the elapsed year. Circle-May & June, Triangle-July,
Square-August, Cross-September.

256

T. NEMOTO

described by Arseniev (1957) in the Weddle sea. But generally speaking
in recent times comparatively short whaling periods indicate the following
lateral movement more frequently than the longitudinal movement in
the whaling grounds of the Antarctic.
Thus the east and west-ward movements are generally observed andtypical seasonal movement is not observed in the North Pacific. On theother hand, the typical dispersal of fin whales has not been observed
if the seasonal movement is taken into consideration. For example considerably many fin whales hit in August or September in the North
waters of Aleutian Islands are caught in the south waters of AleutianIslands in the earlier season of May and June. As those fin whales
might have migrated to the north waters with advance of the season if
they had not been captured, fin whales in the course of migration or
movement should not be regarded as the dispersive movement. HereI would use the term ' dispersive movement*, to describe the ultimate
movement of whales without any relation of seasonal movements.
Up to this time, the real 'dispersive movement' has not been indicatedby the recovery of marks on fin whales as illustrate in Fig. 40. But it
is probable that fin whales make ' dispersive movement ' at some time in
the future. The one of the most reasonable explanation may be a changeof feeding condition according to the oceanographical surroundings.
5. The most important question about the migration and the movementof fin whales is that fin whales in the east and the west in the North Pacific are separate stock or not. There is already a reliable discussion thatfin whales from the waters of western Aleutian Islands and the northwaters of the eastern Aleutian Islands belong to the separate breeding
populations respectively (Fujino, 1956), however, it is safe to say thatfin whales in the northern part of the North Pacific migrate and move
eastward and westward to feed on the more profitable condition of theirfood. And further, there is no barrier between east and west waters
because fin whales have the peculiarity migrating to the marginal and the
mediterranean sea as well as the ocean. I would consider the evidence
that fin whales are separated by blood groups in the northern part of theNorth Pacific described by Fujino (1956) only support the tendency thatfin whales are divided into two or more population in the breeding ground.
But the segregation in the whaling ground is not so strong as it is givenby the brood type investigations. The satisfactory explanation will beobtained after the many accumulation of data are completed.
6. The northern limit of the migration has not been defined by Japanese* The term ' dispersal ' is already used by Brown in 1954, and the meaning is different
from my term. I would use ' dispersive movement. ' here in a different meaning to describe movements of whales.

FOOD OF BALEEN WHALES

257

investigations yet. But considering the distribution and amount of foodsof whales the Bering sea is considered the most northern feeding groundin the North Pacific for fin whales. The Japanese whaling in 1940
covered the Chukchee sea though Bering strait and caught 74 fin
whales. This phenomenon suggests the herd of fin whales attain to the
Arctic sea in their northward migration in considerable number in someyears. The food in the waters may consist of bottom living amphipods
and one euphausiid (Thysanoessa raschii) is considered only a euphausiid
which distributes in the shallow and cold waters. But the condition of
feeding for fin whales is not so satisfactory as in the Bering sea.
A mark (J 6506 in Fig. E) hit on a fin whale in the north waters of
the eastern Aleutian Islands on 6th July is recovered in the off watersof Anadyr gulf on llth August after the lapse of about one month as
a 0 year group. The mark apparently indicate the summer movementof a fin whale from the north waters of the eastern Aleutian Islands
to the most northern part of the Bering sea. This apparently means
the northward movement in the Bering sea, and the northern limit is
not situated along the Aleutian Islands. The pack ice of the Arctic sea
also restricts the feeding ground of whales. As ice is generally prevailing in the Arctic sea and the Bering strait by the early summer(Pilot chart of American navy) fin whales may penetrate the water
only in July, August and September. Japanese operation was operatingfrom 5th to 27th August in 1940, when fin whales were feeding in thewaters through the Bering strait.
7. The important mark (JS7002) is illustrated in Fig. D. The markhit on 8th September in the south waters of Aleutian Islands in 1955
was recovered on 12th July in 1956 in north waters of the same eastern
Aleutian Islands. Though the moving distance in the figure is short, thismovement is considered real ' dispersive movement '. The fin whalemight have migrated to the north waters fairly earlier season in thenext year or the fin whales was feeding in the south waters throughout the season, or came down to the south waters earlier than usual
when it was marked.
The movements of fin whales are also considered by the marking resultsof the lapse of time as well as the seasonal movement. The movement of
0 year group is illustrated in Figs. E, F and G. The marks of 0 year
group in August or September and recovered in September indicate
the summer feeding in the same waters. Some marks hit in July also
recovered in August and September in the very near waters of marking.
A mark (JS7720) hit on 19th July in the north of Komandorskiy is recovered from a little south waters on 24th August, which suggests thesummer staying in the south west waters to feed on the food. The most

258

T. NEMOTO

exceeding movements is given by the mark (J6506) which connects thesouth and North Bering sea. The fin whale may migrate along the
Alaskan continental shelf, one of the most profitable feeding course forfin whales. The short movement (J6511) of 0 year group of a fin whale
indicates also the month long staying in the water. In the year 1957 whenthe mark (J6511) was hit and recovered, Alaska pollack was the dominantfood in the waters in the late of July to the early of August. The
shoals of Alaska pollack must have swarmed in the water from July toAugust, which caused the stay of fin whales. In the next year of 1958,
fin whales migrates to the northern water off Andyr gulf and only a
few herd has been observed in the waters from 58°N to 60°N along
the Alaskan continental shelf. This fact apparently suggest the annualchange of abundance and distribution of food cause different distribution
and migration of whales. The year groups of fin whales also show
the movement, which is given in the figures with the one short crossing
the arrows. The definite catch of 1 year group in 1955 and 1958 isgiven by the next Fig. 41, but one mark (JS7243) which is illustrated
Fig. D. In 1954, 209 fin whales are marked in the north waters of theeastern Aleutian Islands, 7 marks of which are recovered within theyear, and 7 marks are found in the next year of 1955. The four marks
illustrated in Fig. B show the movement to the off waters. The fin whales
hit with marks are feeding on Thysanoessa inermis along the continental shelf, and the captured fin whale are considered to feed on
Calanus cristatus. This change of food condition make 1 year groupmove to the off waters, and the only consideration of the annual return
habit can not explain the problem satisfactory.
The next example, the recovery of marks in 1958 indicates somewhat
different movements. The marks were hit in 1957 in the off waters
where the fin whales were feeding on Calanus cristatus andThysanoessa longipes which show about two longitudes westward
transfer of the cristatus and longipes areas. Five of these fin whales
were caught in the same off waters and they are considered to feedon also Thysanoessa longipes and Calanus cristatus. These fin
whales were hit in September and are caught in July, the factof which suggests that fin whales stay from July to September withother data of 0 year group and the result of the year 1955. Twomarks (J. 6799 and JS. 7243) hit in 1957 show the comparatively long
movement which are illustrated in Fig. 40 D and Fig. 41 C. The former
mark is recovered in the same month of hit in the south waters, andthe latter hit in June in the east waters is recovered in the west
through the Aleutian Islands. The latter mark may be due to theseasonal movement from the east to the west from June to July as I

259

FOOD OF BALEEN WHALES

discussed in the former part. A mark (J. 6799) shows the 'dispersive
movement' that the fin whale hit in July in the north waters of theeastern Aleutian Islands come to the south waters of Aleutian Islands
in July in the next year. The fact also may be due to the feeding in thesouth waters from the spring, and the whale may not migrate to thenorth waters in 1958. The south waters whaling ground consists of
the large amount of swarms of Thysanoessa longipes, which had notbeen observed so often from 1954 to 1956.
The 2 year group shows rather long seasonal movement, the first
impression of which proves the fin whales dispersing with the progress ofyears. The 3 year group has been recovered in a few number comparing
with the 0, 1 year and 2 year groups, but the movement and 'dispersive

C. cristatusI&.

T tonglpes
B

AN

11~2~-~---.1~7~•. ~~1~6,,.----~--,-,6~6~.~

110·

168"

!66°

17/"

Fig. 41. The distribution of food planktons and recovery of 1 year group in 1955
and 1958. Left-Distribution of Calanus cristatus and Thysanoessa longipes
in the adjacent waters to the eastern Aleutian Islands. Middle-marking recovery
in 1955. Right-marking recovery in 1958.

movement' do not demonstrate so exceedingly as 1 and 2 year groupsin 3 year group. There has been only one recovery of 4 year group,
which was hit on 8th in August at the position 53-24N, 169-55W andis recovered on llth July at the near position of 54-23N, 169-55W in
the north waters of the eastern Aleutian Islands.
Swimming direction. About the swimming direction, Kemp & Bennett(1932) describe the swimming direction of fin and blue whales in thewaters of South Georgia and South Shetland. Those illustration drawn
by them do not demonstrate the clear seasonal tendency of swimming
direction but a general tendency of moving. On the other hand, therecent study on. the swimming direction of humpback whales in the Australian waters (Chitterborough, 1953), indicates clear seasonal swimming

260

T.NEMOTO

direction along the west coast of Australia. His result well demonstrate
the south and north migration along the coast of Australia from May
to October, which is directly connected with the migration of humpback
whales to and from the Antarctic.
The swimming direction of fin whales also observed by Japanese investigations after 1952. As a example, I describe here the observationin 1953 in the western part of the northern Pacific, the south watersof Komandorkiy Islands. From May to July, the northward movement
is the dominant tendency of the fin whales, but the southward movement become dominant from August to September. Besides above tendency, the fin whales feeding in the more northern waters also should
be considered because those fin whales will be feeding still in AugustToo~--,-----------~•

ff/- ,,"o.
I

I

'

I

'

I

' \

I

(J)
0)

\

I

\

I

0

I

~u 50

'
'

II

\

'

"'

B

A
\

\

a..

\
\

\

''

' ' 'b,

'-..

0

May

June

July

Aug.

Sep I.

May

June

July

Aug.

Fig. 42. Swimming direction of fin whales in the west part of the northern partof the North Pacific, south of the Komandorskiy Islands and in the off watersof Kamtchatka Peninsula. A-East and West component, Solid dots-West, Open
dot-East component. B-North compornent.

according to the recent observations in the northern waters. It is reasonable, however, the change of the moving direction is accepted as a
general tendency of the migration of fin whales.
The eastward movement from the earlier to the middle of the whaling
season may also be obtained from the Fig. 42 A. But many fin whales
move to the west-north, or to the Kamchatka Peninsula from the southeast, the Pacific Ocean in May. This fact suggests partly that the migration from the south waters does not always follow the coastal waters ofKurile Islands to the north. Kasahara (1950) consideres fin whales arecoastal form from the catch statistics of the location of capture, but
I would consider the fact is only due to the distribution of foods in theadjacent waters to Japan. When fin whales reach the Kamtchatkan coastand Aleutian Islands where the favourite food of Calanus cristatusis dominant, fin whales then migrate following two routes, along theFOOD OF BALEEN WHALES

261

coastal waters of Kamtchatka to the north and the Aleutian Island to
the east. Zenkovich (1937) describes that fin whales are migrating fromthe south Kamtchatka in April and distribute in Bering sea and Arctic
sea in August and September, and south moving schools of fin whales
are observed in October in the south waters of Kamtchatka peninsula.
The westward movement in May and the eastward movement in June
and July will support the recovery of whale marks as I discussed in
the former part. As a probable conclusion, fin whales migrating to thenorth already pass the waters south of Komandorskiy in July, thus thenorth moving component decreases in August, the high time of feedingin the northern hemisphere. Fin whales feeding on their food in thenorthern part of this water are also considered to come down from thelate of August as a general tendency. The east and westward movements also endorse the marking results, but if there is any change of
feeding condition the movement of fin whales may be much different one.
The result by Chittleborough (1953) indicates the much clear swimming
direction, which is apparently due to the fact that humpback whales
migrate along the very coast of Australian Islands. Fin whales in the
coastal waters of Kamtchatka and Aleutian Islands also migrate andmove rather coastal waters, because the food plankton and fish areconsidered rather scarce in the center to the Bering sea, and fin whales
seem not to move through the center of the Bering sea.
The swimming direction of fin whales is also considered to be affectedby the feeding of them. If fin whales are absorbed in feeding, theyshow no indication of definite swimming direction and they are alsochased more easily (Gunther, 1948). This is directly connected withthe dominant occurrences of swimming undefinitely in the heavy feeding
ground especially in the moving when fin whales are mainly feed on
their food.
Catch and distribution in the adjacent waters to Japan. Fin whales
have been caught in comparatively large number already in the pre-war
seasons before 1954 in the Okhotsk sea. The main catch of fin whales
concentrate to the summer season from June to September. As shownin the Fig. 39 the height is observed in July and August.
Fin whales caught in the Okhotsk sea may come from both sides of
the Pacific side and the Japanese side. Omura (1950) already considers
that those whales migrating northwards though the Japan sea in May
or June seem to enter into Okhotsk sea through the Soya strait. According to his description (Omura, 1950, p. 53) the thickness of blubber
and the diatom infection of fin whales in the Okhotsk sea differ fromthose of the Pacific side suggesting that there appears to be little likelihood of both groups migrating through the straits between the Kurile

T.NEMOTO

262

Islands. The latter distinction, however, is rather difficult to be explained
as a definate one. Because the whaling grounds in the Okhotsk sea aresituated on the shore waters from 10 miles to 60 miles, but those in
the Pacific side lie in the off waters. The long pulling of whales fromthe captured position to the landstation may cause the falling off ofdiatom covering on the body surface of the fin whales. Thus the latter
distinction may not be a reason for separating the groups of fin whales.
There is another interesting observation. When I visited the landstationof the Okhotsk sea, the healed oval scars are observed on the surfaceof fin whales. These oval scars are originated to the open pit formedin the southern waters (Nemoto, 1954, p. 76). As the fin whales caught
in the east China sea have only a few oval scars on the surface of the
body (Mizue & Fujino, 1957), the fin whales migrating in the Japan sea
Okhotsk

North Kurile%]

Ch"anzen

Ursan

-u15
u

South Tsushima· S:
fMAMJJ

Oshima (Wakayamd)

ASONDJFMAMJJASOND

Fig. 43. The catch of fin whales in the adjacent waters to Japan in the seasons
before 1954 according to available data by Japanese operations.

are considered to bear few scars. Because according to the catch statistics, those two groups of fin whales may not migrate to the subtropicalwaters of the Pacific Ocean where they may suffer from the open pits.
The fin whales with many open pits have migrated from the Pacificside, though there is no evidence of whale marks or some other direct
investigations.
Along the Pacific coast of Japan, fin whales have been caught mostly
in summer in the waters north of Hokkaido in the seasons before 1945.
As the recent operation has not caught the available data of fin whalesin the adjacent waters to Japan, I would use only the catch before
1945 on the problem here. The catch percentage is illustrated in Fig.
43. Though only a few fin whales had been caught in the Oshima

FOOD OF BALEEN WHALES

263

waters, Wakayama prefecture, but the main catch in Wakayama waters
is observed in the January in the winter season. The catch of fin
whales in the waters is not so abundant as blue whales in the very
opening seasons of whaling. This would indicate that fin whales distributing along the Pacific side of Japan may disperse in the off waters
more remarkably in winter season. In the summer season, fin whales
had been caught mostly from May to August in Sanriku waters andthe height is observed in July. From June to October, fin whales had
been caught, and its height is in September in the Hokkaido waters.
This difference of prosperous season of whaling for fin whale is considered
to be due to the delay of the, favorable feeding condition. Foods offin whales in th,e waters consist mainly of ' Krill ' (Mizue, 1951),
which is apparently Euphausia pacifica in the coastal waters. Kasahara(1950) states that fin whales are swimming in the coastal waters, but it
is difficult to estimate the fin whales migrate to the north along thecoast of Japan, because, the fact that the fin whales had been caught from
June to August in the off waters of Kamtchatka Okhotsk sea, South Kurile
Islands, Hokkaido, Sanriku and South Korea, indicates fin whales which
migrate early time to the north feed on their food in the north waters
and late comer feed in the southern waters. This habit of migration of
the fin whale has not been ascertained by recent investigations owing to
the scanty of data. It is probable, however, those fin whales which
had been visited the adjacent waters to Japan have decreased in number by the whaling operation or they have changed their migratory
course and have gone to the further north waters to feed.
The whaling season of South Kurile waters shows no difference fromthat of Hokkaido region, but that of the North Kurile waters shows
the height only in August suggesting short duration of migration.
The catch of fin whales in the Okhotsk sea is observed also in the
short duration of July and August. This will demonstrate the connectionof the group of Japan sea. Omura (1950, p. 53) considers fin whales
in Japan sea seem to enter in the Okhotsk sea through the Soya strait.
The catch along the coast of Korea seem to give the support to this.
As shown in Fig. 43, fin whales had been caught in two seasons a year
in the North Korean waters which are given by the catch of Ushin and
Chanzen. The heights are observed in May, October and November,but the summer catch has not been observed, suggesting that those fin
whales go to the north swimming into the Japan sea to the Okhotsk sea
as described by Omura (1950). The height of catch in the Urusan waters
is observed in October, a little earlier than the northern coast of Korea.
If those height mean the northward and southward migration of fin
whales as suggested by Omura (1950, p. 52), fin whales migration along

264

T.NEMOTO

the coast of Korea must have gone down in the very winter season,
December, January and February or disperse in the off waters.
The catch of South Korea and Tsushima straits are divided into threegroups, the South Korean waters, North Tsushima strait and South
Tsushima strait along the Kyushu and the most west part of Japan.
The north strait catch shows two peaks of heights. This summer
catch of fin whales is very interesting, because fin whales have been
considered as a migratory animals that they feed in the cold highlatitudes in summer. The water temperature in the South Koreanwaters is ranging from 25°C to 30°C July, August and September which
is very high as a feeding ground for fin whales. Kasahara (1950, p.
27) considers that fin whales of the late migratory herd may feed in the
TABLE 38. CATCH OF FIN WHALES IN THE EAST CHINA SEA BYJAPANESE OPERATION FROM THE LANDSTATION OF
WEST KYUSHU FROM 1955 TO 1957

1955
1956
1957

July

Aug.

~

~

34
14

2
20

10
18
13

25
36
26

29
45
12

Sept.
36
45
11

Oct.
~~

33
23
18

47
26
27

25
29
13

3
6

3
11

13
18

southern waters, but I would consider the fact is mainly due to the
local segregation of fin whales. The catch of fin whale in the Northstrait recalls me of the recent catch of comparatively many fin whalesin the East China Sea. The catch of fin whales in the east China sea
also concentrated in summer from July to August. The whaling groundof the East China Sea is considered to consist of 'the Krill' Euphausia
paci.fica, which is very dominant also in the Yellow sea and Koreanwater and become a very favorite food for mackerel (Nakai, 1942). This
abundant Euphusia pacific a and other fish feeding on it, may support
the stay of fin whales in the Yellow sea and the East China sea as wellas the surroundings of the lands and Islands.
From the body length at the sexual maturity and size compositionof fin whales, fin whales in the East China sea are rather related tothe catch of the Yellow sea. The Yellow sea landstation before 1945 had
distributed along the west coast of Korean Peninsula (see Fig. 24), at
which the described number of fin whales had been caught by the available data in the seasons before 1945. At the most southern landstation,
Daikokuzan Islands, fin whales had been caught in winter season from
November to June, and the height was observed from February to
April. This catch seems to have some relation with the catches of North
Tsushima Straits and Ursan. If this assumption is true, fin whales
migrated to the west along the South coast of Korea in winter may

FOOD OF BALEEN WHALES

265

spend winter in the waters, then migrate to the north along the coastof Korea, but this group of fin whales might have never been caught
as the summer catch of the North Tsushima Straits from May to the earlyof September. In the Yellow sea, fin whales had been caught from
November to July. It is very interesting that the catch of the most
northern part of the Yellow sea, shows its height in May, and considerable catch of fin whales also observed in April and June. These fin
TABLE 39. NUMBER OF FIN WHALES HAD BEEN CAUGHT IN
THE ADJACENT WATERS OF WEST COAST OF
KOREA AND IN THE YELLOW SEA
Month
LocalityJ
KaiyotoDaiseito
Tsingtao
Osei toDaikokuzanto

1
56
4
26

F
1
52
4
4
66

M
5
20

A
31
20

M
52

4
96

79

27

J
31

J

A

s

0

4

N
4

D
2
50

26

2

TABLE 40. CATCH OF BALEEN WHALES IN THE SOUTHERN
WATERS OF THE PACIFIC FROM 1920 TO 1954*
Blue
Formosa
Bonin Islands
Lower California

15
27
989

Fin

Hump.

Sei**

Grey

7
12

734
849
1581

10
1823
119

182

* Figured up from the data by Omura, Nishiwaki, Fujino & Kimura,
1957. ** Including Bryde's whales in the catch.

whales may come down to the southern waters of the East China sea
in summer. Kasahara (1950, p. 29) already noticed that the size distribution of fin whales in the Yellow sea was different from that of thecatch in winter season in the South Tsushima strait.
The latter catch shows the larger size distribution which is considered
to have connection with the early migrater of fin whales in the Japansea. They were different from the former Yellow sea group, which I
would consider the same group as fin whales caught in the East China
sea by recent operations. Mizue (1956) states fin whales caught in the
East China sea may belong to the group of the Yellow sea. As I said in
the former part, fin whales caught in the East China sea attain thesexual maturity in the shorter body length (Mizue, 1956), and the body
proportion of fin whales in the East China sea differ from those of thenothern part of the North Pacific (Ichihara, 1957). These fin whales inthe East China sea are considered as a ' local group ' in the North
Pacific. The local group of fin whales may be due to the oceanographical266

T. NEMOTO

separation by lands and islands as well as the abundance of their food
throughout the season. The depth of the Yellow sea is very shallow, andwater temperature and salinity show the very characteristic values,
however, Euphausia pacifica and Pseudoeuphausia latifrons bear possibility of dominant food for fin whales in the Yellow sea throughout
the season.
The whaling ground in recent Japanese operations in the East China
sea is found along the boundary of the warm current from the south
and the cold current from the north. The boundary between above twocurrent moves as illustrated in Fig. 44, which also indicates the move128

I O'

E 36'

125'

,

. ,;!' 2
6
B

Fig. 44. A example of oceanographical condition and the distribution of the water
convergence in the east China sea in summer, A-water currents and distributionof surface water temperature, Black-warm current, White-cold current, Ccold coastal waters. B-the center line of the water convergence in each month.

ment of favourable feeding position of whales. This means the movement of the swarms of Euphausia pacifica by the current as much as
physical condition of E. pacifica to come up to the surface waters.
The summer remainder of baleen whales in the low latitudes is also
observed especially among humpback whales in the Indian ocean (Brown,1957), and in the summer season of the southern hemisphere. Rouqual
whales in his report may be warm water living Bryde's whales, but someoccurrences of fin whales may be probable like the East China sea.
Winter catch. The winter catch of fin whales in the both side of the
Pacific ocean is also should be considered to get the exact distributionof fin whales in Ocean. Up to now, very few fin whales have been caught
in the southern Pacific Ocean. Namely only 7 fin whales have beencaught in the winter season in the Bonin Island waters, and none in the
Formosa waters (Omura, Nishiwaki, Fujino & Kimura 1957) according to267

FOOD OF BALEEN WHALES

Kasahara, 1950, 1 fin whales was caught). The catch of fin whales inthe Lower California along the American coast had been also very scarcein number. These catch results suggest that fin whales in the Pacificseem not to enter the subtropical waters of 25°N latitude and further
south waters or perfectly disperse in the subtropical waters not to accessthe coastal waters of islands and continents.
In the southern hemisphere, however, Moerch (1911) states that thegreat number of fin back whales congregate on the waters along the Brazil
coast between 12° and and 18° south latitudes during the period from
May to November. This winter catch of southern hemisphere is observed at the whaling stations of South Africa, but they are situatedat about 30° south latitudes.

:il 1000

30· -5

0

8

i

0
:;;

20

:g,
0

-"

c

z 500
E

"'~

10

Jan.

Feb.

Mar.

ri"

0

Fig. 45. Monthly catch and monthly percentage of baleen whales in the Antarctic
waters. Left-Catch by Japanese operation in the Antractic waters. Solid line
and symbol-Fin whales in 1957-8 season in the Antarctic area VI. Dotted line
and open symbols-Fin whales in 1956-7 season in the Antarctic area VI. Chain
line and triangle symbol-sei whales in 1957-8 season.: Right-monthly catch
percentage in the Antarctic waters from 1927-35. Open circle-Blue whale, solid
circle-Fin whales, Solid triangle-Humpback whale, Open triangle-Sei whale.

Antarctic waters. In the Antractic waters, the four large baleen whales
have been caught by pelagic whaling operations, but fin whales have been
the main catch in recent operations. And as the whaling regulation
restricts the commencement of the catch of baleen whales, I would consider that the real migration of baleen whales should refer to the catch
statistics of old operation in the Antarctic.
Mackintosh discusses (1942, p. 270) the monthly species ratio in the
Antarctic as well as in the waters of South Georgia. According to his
explanation, it is clear that there are some difference among the arrivalsof baleen whales. Blue and humpback whales migrate to the antarctic
waters earlier than fin whales, and sei whales come in the late of thesummer season. Based on the old seasons' catch between 1927 and '35,
the catch percentage of each whales species from October to April showsT. NEMOTO

268

said clear tendency. Humpback whales seems to migrate to the Antarctic
waters a little later than blue whales from the statistics. About the catchof the South Georgia waters, Mackintosh (1942) states the yearly changeof migration of blue and fin whales referring Harmers' discussion (1941,
South whaling. Proc. Linn. Soc. London, p. 69-83). This oceanographicalchange bears apparently the influence to migration of whales. Japanese
operation in the whaling ground of the former sanctuary, that is the
Antarctic area VI, also proves the yearly change. Fin whales have beencaught mostly in February like the result in 1956 and 1957 season. But
the height of the catch is observed in January in 1957 and 1958 season
when the catch of fin whales decrease in the late of the season in March.
s

160£______ .

~_____ 0°16F§r<:..____________
_
...

165 E

/6~4·~w~-~-'-~~~,6~0'=w--'-~-'--~'--1~6~/=w--''~

Fig. 46. Two examples of the distribution of pack ice line and food euphausiids.
Left-whaling ground near Baleney Islands. A-whaling ground of Blue whales
feeding the swarms of 1 year group of Euphauma superba. B-whaling ground of
fin whales feeding 1 year group of E. superba: Right-C-whaling ground of fin
whales consists of 1 and 2 year groups of E. superba. D-whaling ground of
fin whales due to 1 year group of E. superba. Arrows show the retreat of thepacle ice lines. Lines and date show the distribution of pack ice lines in the date.

In the latter whaling season, many sei whales were caught in March,
but not in the earlier season of January and February, which is thesame tendency as the usual year.
The ' balance ' among whales should be considered to get the exact
distribution of baleen whales. Fin whales come to the Antarctic waters
after the height of blue and humpback whales, and sei whales comeafter the height of fin whales in general. The recent abundant catchof sei whales in the Antarctic partly may be due to the decrease ofblue and fin whales by recent whaling operations as well as the oceanographical conditions.

269

FOOD OF BALEEN WHALES

If the waters where the swarm of Euphausia superba is abundant
are occupied by the early comer of whales. The followers were seem tobe obliged to seek their food in other waters. Of course their favorite
foods in the North Pacific are so different that the baleen whales may
congregate to different waters according to the distribution of foodspecies. But the food of blue and fin whales in the Antarctic is mainly
Euphausia superba in common, and the segregation of distribution ofabove two whales in the Antarctic is directly considered to be due tothe occupation of favorite waters by the difference of coming and biological strength.
The segregation of fin whales in the Antarctic into some groups isalready suggested by Hjort, Lie & Ruud (1933) and Mackintosh (1942, p.

0

50

~ 40.
-~'

.;.•
0

6

30

·0 20

0

;;;
>

;.:;

0

10

~.t

____________ ,,..

•
60°E

•
100°E

+
l40°E

+

180°

140°W

l00°W

Fig. 47. Vitamin A products from the whales' liver extract by Japanese whaling
expedition in the Antarctic waters in 1958. Solid circle-January, Open circleFebruary, Cross-March. Dotted line shows average curve in January.

258), and recent interesting results of whale marking compiled by Brown(1954) also subscribe that many fin whales are shown to return fromtheir migrations year after year to somewhere near the place where
they were marked. The evidences that the range of dispersal in fin
whales appear to be limited to within 50° east or west and the dispersal
is not necessary progressive are also considered to show the segregation
to some extent. The body length at the sexual maturity is considered
to be also somewhat different in the certain Antarctic areas (Purves &Mountfort, 1959).
Japanese whaling operations usually make vitamin A oil from the liverof baleen and sperm whales. The concentration of vitamin A extracted
from the liver differs very much in each Antarctic area and month. In
the western waters of Japanese operation in the Antarctic, the valueof vitamin A in the liver oil is very low showing about 10 · 10~ in 1 kg.

270

T. NEMOTO

The value is nearly the same in the Antarctic area IV, and considerably
higher in the Antarctic area VI and I of former sanctuary, where
Thysanoessa macrura has been observed in the stomachs of baleen
whales as a staple food. As a simple and bold explanation, thevitamin concentration may be due to the difference of the vitamin concentrations between Euphausia superba and Thysanoessa macrura, as
the difference among the vitamin A concentration of euphausiids isalready observed (Fisher, Kon & Thompson 1955). These differences ofthe vitamin A concentration of whales' liver suggest the local stocks ofthe fin whales in the Antarctic like the iodin value of whale oil differingin each Antarctic area (Lund, 1952). As the fatty acids of componentsof whale oil of the northern part of the North Pacific also differs fromthose of the Antarctic waters (Saiki & Mori 1956; Saiki, Shin-chen Fang
& Mori 1959), the physical condition affected by food must be consideredto suggest the food on which they feed.
A example of the local movement of fin whales in 1958 in the Antarctic
waters is following. The whaling ground in the Antarctic waters ismuch affected by the distribution of pack ice, and baleen whales canfeed on euphausiids smarming mainly in the near waters of the packice. In the early time of the Antarctic summer, the patch of Euphausia
superba of 2 years group already appears along the pack ice, and iscopulating and feeding in the surface. These patches consisting of 2 years
group Euphausia superba are left with the advance retreat of themelting of pack ice. The comparatively late commer fin whales feedon the left patches of swarming of E. superba in the off waters which
is illustrated in Fig. 46. The C whaling grounds in Fig. 46 are foundin the waters where the pack ice was prevailing still on 16th January
in 1958.
After the lapse of 10 days, the pack ice line retreats to the south
west in fairly rapid speed. The patch of Euphausia superba has been
observed in the C waters in the middle of February, but no fin whale
migrates to the waters at that time. After the first observations ofEuphausiid patch, fin whales come to the waters in the late of February.
The difference in day is about 7 days or one decade. In the late of
February, the pack line far draws to the maximum retreat, and fin
whales also feeding on the swarms of 1 year group distributing in thewaters of the pack ice line of 30th January. In the C'waters both 1
and 2 years groups of Euphausia superba are found in the stomachs ofwhales caught in the waters, but the adjacent whaling ground to C'
waters consist of 1 year group of Euphausia superba only. The samekind of whaling ground consist of 1 year group of Euphausia superba
is also observed along the most retreated pack ice line. These waters

FOOD OF BALEEN WHALES

271

attract many baleen whales from the middle of February to March,which is apparently one evidence that the swarms of 1 year group
Euphausia superba make the main food of baleen whales in the latterof the summer. In the C whaling ground, many fin whales come to thewaters with the delay of 5 days after the swarms of patch is observed.
Arseniev (1957) states the same observations with regard to the distribution of the patch of Euphausia superba and whales. Many schoolsof baleen whales usually congregate to the waters where many patchs of
Euphausia superba have been observed. And there is a direct relation
between the school of baleen whales and the distribution of food patchs.
The next illustration is shown also in Fig. 46. In 1958, a Japanesewhaling expedition operated in the waters of adjacent to Baleny Islands.
The pack ice line in pre-whaling season of 15th December lies still closing
the Islands, but on 9th February, the pack ice line retreats making theinlet of pack ice where the abundant of Euphausia superba of 1 year
group is swarming, many blue whales are observed staying and feeding
there for ~alf a week in the early of February. The pack ice line
retreats further in a week, and many swarms of Euphausia superba
observed in the waters between the pack ice and Baleny Islands.
Fin whales have been congregating to the waters for half a monthafter the melting of ice, and they become a large group consist of
many schools of fin whales. These two cases may be a illustration of
distributions of whales in the Antarctic in summer. Like the northern
Pacific waters, where there is a food, there come many whales. But
blue and fin whale do not seem to be mingled so closely with each otheras it is shown in the above illustrations.
Seasonal and local changes in compositions of fin whales. Mackintosh(1942, p. 259) discuss the seasonal change in the local composition of
the stock of Antarctic baleen whales, and it shows a general comprehension about the mode of the migration of whales. As it is illustrated inFig. 45, each species ratio shows very particular tendency in the Antarctic waters. But in the northern part of the North Pacific theseseasonal change in monthly species ratio has not been observed typically.
On the contrary to the fact in the Antarctic waters, fin whales comeearlier than blue whales in the western part of the northern part of
the Pacific in ' Calanus year', which is apparently due to the feeding condition. However, fin whales come earlier than sei whales in the feedingarea of the northern part of the North Pacific as a general result likethe Antarctic.
Up to this time, the difference in the sex ratio with the advance of
seasons has not been clearly observed in the North Pacific, but malesof fin whales are rather less in number in the early season of May.

T.NEMOTO

272

The number of male fin whales become gradually dominant in thelatter part of the season, and males are dominant in the total sex ratioof fin whales (Ohsumi, Nishiwaki & Hibiya, 1958, Table 1). But suchtendency is not observed in some years and localities. For example,
males do not become dominant in the latter part of the season in 1953,
but the fluctuation of male occurrences were observed throughout theseason. In the Antarctic waters, male fin whaies also increase fromJanuary to February, but decrease again in March in the whaling area
VI from 1956 to ·1958 (Ohsumi, 1959). This has also been observed in
the area I as illustrated in Fig. 48.
As a general tendency in the Antarctic areas, there is a marked
change in the summer season in the percentage of adult females which

c0
g, 70
Q)

Q:
so~~_._~~_._~~_._~~~~~~~~~~~~_,._~
1or-~~~~~~~~~~~.-~~~~~~~~~~

VI
~
Q)

0

~

50

.

,P~ .-----~'\..._,_ ../o----<S

o..._

A

I

~

30'-'-~-'-----.--"--'--"--'-,.....-L~-'-l--'-~-'---'--.,--..L---'-~_._,_._~F
M
M
Fig. 48. Catch percentage of pregnant female and male of fin whales caught byJapanese operations in the Antarctic areas of VI and I from 1955 to 1958 seasons.
Dotted line and open symbol-1955-6 season, Solid line and black symbol-1956-7
season; Chain and solid line without symbols-1957-8 season.

are pregnant (Mackintosh, 1942). Usually pregnant females decrease in
number with advance of the season as illustrated in Fig. 48. Thistendency has also been obtained in the northern Pacific in some years
though it is not so typical as in the Antarctic waters. In the northernpart of the North Pacific, near Bering sea, the pregnant female is considered to congregate in the southern waters and the pregnant percentage of female fin whales declines a little in the latter part of thesummer season. But the local difference in the occurrence of pregnant
female of fin whales shows the very reverse in 1958. Almost female fin
whales caught in the waters off Kamtchatka Islands show the pregnant
percentage of 77 and those caught in the center of the Bering sea show
44 percent in 1957. The successive operation in 1958 shows the following
figures. Pregnant percentage of 70 in the waters off Navarin cape andFOOD OF BALEEN WHALES

273

about 55 percent in the waters off Kamtchatka Peninsula. Above fact
will indicate that the migration of pregnant fin whales is rather elastic
in the northern part of the North Pacific mainly according to the complicated shape of the sea surrounded by lands and Islands.
Generally speaking, Antarctic feeding grounds are situated high latitudes and colder t4an those of the northern part of the North Pacific.
The decline of the pregnant female in the Antarctic may be due to thestart of female fin whales with larger foetuses to the breeding areasfor parturition (Laws, 1959). In the northern part of the North Pacific,
fin whales still may be able to remain in the waters in the latter partof the seasons, because the water temperature is not so severe as in
the Antarctic feeding area.
There is another tendency that the immature whales become comparatively numerous in the latter part of the season in the Antarctic
waters (Mackintosh, 1942, p. _274), which is also observed in the recent
Japanese operations also in the Antarctic areas of the former sanctuary.
In the northern part of the North Pacific, however, the distribution of
immature fin whales show the local differences. The sexual immature
fin whales congregate most typically in the north waters of the eastern
Aleutian Islands. On the other hand the number of immature fin whales
is less in the waters off Navarin and Kamtchatka peninsula. Further
the age compositions of fin whales in those waters vary through theseason, but the mature whales become dominant in the latter part ofthe season. The south waters of the eastern Aleutian Islands show thelower catch of immature fin whales than the north waters, whichindicates that the northern part of the eastern Aleutian Islands is thecenter of the congregation of immature and younger fin whales in thenorthern part of the Pacific,
These fragmental informations also demonstrate the general conclusionthat the seasonal and local composition of fin whales in the northernpart of the North Pacific is rather elastic and it needs further accumulation of materials before any conclusions are obtained. I would treat
the problem in the coming report in future.
School of fin whales. The school of fin whales are also examined according to the observation of operations and whale marking cruises.
Examples both in the Antarctic and the North Pacific are given in
Tables 41 and 42, The single swimming and pair swimming fin whales
are dominant in May, and schools consist of more than three fin whales
are rather few in number. With the proceeding of the month, single fin
whale become scarce and the rate of schools consisting of two and three
fin whales become dominant. This fact seems to show fin whales of theearly migration make couple or trio in the feeding grounds. There may

274

T. NEMOTO

be another explanation that the school consisting of more than two whales·
may migrate in the feeding ground later or the single whale comes earlier.
I would consider, however, the former explanation is probable according
to the other observation by Japanese expeditions. In the Antarctic
waters, Japanese whale marking cruises observe the number of fin whales
in a school as described in Table 41. As these marking observations
TABLE 41. NUMBER OF FIN WHALES IN A SCHOOL OBSERVED BY
JAPANESE AND NORWEGIAN WHALE MARKING CRUISESIN THE ANTARCTIC WATERS FROM 1955 TO 1958
Number of whales in a school

Cruise
2
12
24
4
6
34

1
25
27
56
3
22

Konan maru No. 12
Seki maru No. 16
Fumi maru No. 17
Kyo maru No. 5
Enern

3
5
10
2
2
19

5
1
10
1
2
5

4
1
4
1
2
7

6
1
3
2

7
1
1
1
1

8

9

10

3

0

2

2

TABLE 42. NUMBER OF FIN WHALES IN A SCHOOL IN THE
NORTHERN PART OF THE NORTH PACIFIC, OFF
WATERS OF KOMANDORSKII ISLANDS
Number of whales in a school,.r-- · - - - - - -

May
June
July
Aug.

1
58
135
40
26

2
64
190
86
78

3
18
64
49
44

4
5
14
10
5

5
7
6
6
4

6
1
4

7

8

9

1

1
1

1

TABLE 43. COMPOSITION OF SCHOOLS OF DIFFERENT SPECIES, BLUE
AND FIN WHALES OBSERVED BY JAPANESE WHALE
MARKING CRUISES IN THE ANTARCTICFROM 1957 TO 1958------- - - - ......

~-~

Fin

Blue

Number of whales
1
Estimated length of62
71
whales in feet
Total number of whales
2
in a school

1
72

Blue

Fin

~------Blue Fin~---------..__

Blue

Fin

~-~

Blue

Fin

3

1

4

2

4

63-65

80

65-67

73

64-65

60

6

Ca 12

4

5

2 Ca 1070

have been carried out in advance of the commencement of the catchof baleen whales, the results demonstrate the predominance of a single
and couple swimming fin whales alike in the northern Pacific waters.
The result by ' Konan-maru No. 12' and ' Seki-maru No. 16' wereobtained in 1955 to 1956, which shows the rather related tendency. Butthat by Fumi-maru No. 17 in 1956-57 clearly shows the excessive predominance of single swimming fin whales. These facts also seem to suggest
the coming time of fin whales to the Antarctic waters. In the whalingFOOD OF BALEEN· WHALES

275

season 1956-57, the whaling operation observed the late coming of fin
whales in the Antarctic area of VI and I. The catch result illustrated
in Fig. 43, also endorses the fact. The next season in 1957 and 1958,
fin whales come earlier to the Antarctic area I and VI as given by thesame Fig. 43. The exact observation on the constitution of fin whalesis, however, only given by a catcher boat 'Kyo-maru No. 5' on which
I was board. The data are so few that I can not draw any definite
conclusion here, but I would consider the single swimming fin whale isdominant in the earlier time of the Antarctic summer according to otherobservation throughout the season,
The interesting fact that fin whales make a school with other blue
whales have also been observed in the Antarctic. I noticed five schools
consist of blue and fin whales. The estimated size of whales' body gives
us the impression that comparatively small blue whales swim along withthe moderate fin whales. The number of blue whales are always thesame or less than that of fin whales as described. The smaller size
immature blue whales may not have special characteristics of species,
and migrate along with the fin whales of different species. The fact
will add something to the consideration of ' balance of whales ' that thestrength of each species will develop especially after the attainmentof the sexual maturity.
Diatom infection. Hart (1935), Karcher (1940) and Omura (1950, a)
consider that the whales with heavy diatom infection must migrated to
the Antarctic waters earlier than those without the infection, and thehabit of making school in fin whales is a favorable infectious condition
for diatom films. The main parasitic species of diatom infection is
Cocconeis ceticola Nelson both in the Antarctic and in the North Pacific.
As Cocconeis ceticola has not been found among planktons and on otherthings than the skim of whales, Cocconeis ceticola is considered the realparasitic diatoms and not holophitic. The variation of C. ceticola varies
according to the host species of whales (Nemoto, 1958). With regard
to the other species of infections diatoms, Stauroneis, Navicula andGomphonema diatoms are considered to be real parasitic diatoms. But
these species will not indicate the migration course or stage of whales
in migration so satisfactory as Cocconeis ceticola (Nemoto, 1956).
The whales with heavy diatom is considered to migrate to the highlatitudes of cold waters earlier than those without the diatom infectionor have a chance to be infected. But the chance of being infected bydiatoms is not so common for every fin whales. This mean the casethat fin whales early migrated to the high latitudes have not been infected by the diatom patches, and the late comer which has the directchances of infection bears heavy diatom patches.

276

T.NEMOTO

Examples for these propagation of Cocconeis ceticola and the migrationof fin whales in the northern part of the North Pacific are summarized
as follows.
1, In 1952, the percentage of infection shows the minimum degreein the late and middle of the August when the ratio between bodylength and thickness of blubber also decreases mostly. This would indicate the migration of lean fin whales of new coming to the waters.
2. In 1953, the same tendency that the number of fin whales withheavy diatom infection vanish in the late of August, and the whales
with heavy diatom infection have thick blubbers in general. But in theearly season of May and June, fin whales without diatom patches also
have rather thick blubbers.
3. In 1954, the whaling operation had covered the broader area. And
the result obtained in the year shows that the fin whales caught in thenorth waters of the eastern Aleutian Islands demonstrate the highpercentage of infection, and no decrease in the late of August. In thesouth waters of the eastern Aleutian Islands, the infection percentage isvery low in May and rapidly increase with the advance of seasons inJune and July.
After July, the percentage of infection is higher in the eastern waters
than in the western waters.
4. The infection percentage in 1955 is comparatively higher fromthe eal'ly season of whaling, and fin whales in the north waters of theeastern Aleutian Islands show no difference from those west waters in
the infection percentage. And there is no seasonal change throughout
the season.
5. In 1956, the diatom infection percentage is also higher among thewhales in the north waters of the eastern Aleutian Islands. The infection percentage of diatoms increase with advance of the whaling season, but the decrease of number of fin whales with heavy diatom infection is also observed in August.
As a probable conclusion, fin whales come to the Aleutian waters from
May, and many fin whales migrate to the waters by July. The schoolof fin whales are feeding on the food planktons and make northward
movements. If the food become scarce in sometimes, whales move toother waters at once. The decrease of number of whales with heavy
diatom infection in the off water of Kamtchatka Islands in August may
be due to the change of migration of whales owing to the scarcity offood planktons as I said in the former part. In the north waters of
the eastern Aleutian Islands, the food is comparatively much and fin
whales are congregated in the waters throughout the summer season.
Thus it is cQnsidered that the high percentage of diatom infection is ob-

FOOD OF BALEEN WHALES

277

tained. The school of fin whales with heavy diatom infections will
indicate the difference of the stage of movement for feeding from thosewith few diatom infection.
In the Antarctic waters these observations of diatom infection by
Japanese investigations also have been carried out and the results havebeen published in former reports (Omura, 1950 a, etc.). I found very
characteristic tendency that the fin whales which had been feeding forlong time in the definite school were infected with heavy diatom films.
The school of fin whales caught at the waters of B whaling groundin the left figure of Fig. 46 in 1958, and those whales were considered
to feed on 1 year group of Euphausia superba for a long time, as fin
whales caught in the near waters were different in the stage of diatom
infection. Some of the latter school of fin whales lacked completely
the diatom infection. Other biological characters such as the thicknessof blubber endorse the above suggestion. So it is very important totreat the diatom infection on whales in the Antarctic separately in each
whaling ground. The summarizing of the data may cause very elastic
conclusion.
Thus the infection of Cocconeis ceticola indicates the stage and condition of migrations of baleen whales to some extent, but the following
point should be considered to get the more definite conclusion.
a. As the observation on the diatom is made by the naked eyes infection, it is not so stable that the data of stage of infection may beuncertain in some cases.
b. It is not certain that Cocconeis ceticola propagates on the bodysurface of whales from spore or a cell in what speed. On the point,
Hart (1935) considers it takes about a month that the diatom film propagate on the surface of the body of whales by observations of sei
whales in the waters of South Georgia. But I would consider that thetime is shorter than a month by other observations on the propagationof marine diatoms.
c. The seasonal prosperity and decay may be observed also among
the propagations of parasitic diatoms. The height of the propagation of
diatoms is considered in spring and autumn in the sub-Arctic and Antarctic waters, but the height is concentrated in the summer in the highlatitudes. The fact would indicate the decrease of infection percentage
in the middle of the season in the comparatively lower latitudes.
d. The chance for the infection of Cocconeis ceticola is not similar
for each school of whales. For example some whales without diatom
infection have very fat body with heavy thickness of blubber. On theother hand very lean whales with new half healed open pits sometimes
bear diatoms infections.

278

T. NEMOTO

e. The diatom film of dead Cocconeis ceticola is also found on the
body surface of whales, which is very difficult to be observed. The
case show a indication of probable decrease of the infection percentage
in the latter part of the propagating season.
f. In the adjacent waters to Japan, the diatom infection is only observed on fin whales in high percentage in the Okhotsk sea, and whales
in other waters show very few infection of diatoms. As the towing ofwhales in the long run cause the coming off of diatom films completely,
and above fact is apparently due to the long towing of whales, because
the whaling ground in the Okhotsk sea is comparatively near the landstation, but those of other waters is in the off waters.
SUMMARY

The present paper is described mainly on Japanese investigation onwhales both in the Antarctic and in the North Pacific after the year
1945. And two subject of food of baleen whales and the movement of
whales are discussed, but the biology of food planktons is omitted inthis paper. The essential points are descr:ibed follows.
1. The feeding apparatus of baleen whales and preferences for foods
are discussed. Baleen characteristics such as number, shape and fringeof plates are examined according to former published reports and thepreserved specimens. These characteristics show the four types. Thoseare blue whale, sei whale, right whale and gray whale types. The typeof sei whales is included in blue whale type in one point, but is also
included in right whale type in another point.
2. The summarized description on head, mouth, tongue and ventral
grooves of whales body is described in order to get the comprehensionof feeding of baleen whales. These body structures are also divided
into above four types.
3. The Antarctic large baleen whales feed heavily on Euphausia superba.
But blue and fin whales also feed on Thysanoessa macrura in thewaters of former sanctuary. Sei whales take Parathemisto gaudichaudi
favorably, but other blue, fin and humpback whales never take it as amain food. Fish and squids are considered to bear no importance forbaleen whales in the Antarctic.
4. Feeding percentage of baleen whales is high in the morning and in
the evening in general. The percentage is higher ju humpback andblue whales than in fin and sei whales.
5. The growth of Euphausia superba described according to the localityand distribution of the pack ice. Euphausia superba in the low latitudes
or in the early ice melting waters grow more rapidly and in advancef<'OOD OF BALEEN WHALES

279

of the late ice melting waters. But there is no difference in the relation
between body length and weight of Euphausia superba in each locality.
6. The main foods of baleen whales in the northern part of the North
Pacific are described with successive investigations after 1956. These
are as follows:Blue whale
euphausiids
Fin whale
euphausiids, copepods, swarming fish
Sei whale
copepods
Humpback whale euphausiids, swarming fish
7. Five species of euphausiids are found in the stomachs of baleen
Euphausia pacijica, Thysanoessa
whales in the northern Pacific.
longipes, T. raschii, T. inermis and T. spinifera are those species.
8. Two copepods, Calanus cristatus and Calanus plumchrus are also
described as main foods of baleen whales. Calanus cristatus is important for fin whales and C. plumchrus is important for sei whales.
9. Swarming fish, herring, Alaska pollack, capelin, Atka mackerel andsaury are fed by fin, humpback and sei whales. A squid, Ommastrephes
sloani pacijicus is sometimes fed by sei and fin whales.
10. There are annual changes among the abundances of foods andthe distribution and fluctuation of foods which influence the migrationand movement of baleen whales in the North Pacific. These problems
are discussed to some extent in the paper.
11. There are 'Calanus year' and 'Euphausiid year', in the adjacentwaters to Aleutian Islands and the South Bering Sea.
12. The quantity of stomach contents in the northern part of the North
Pacific is examined. Humpback whales usually take more abundant foodthan sei and fin whales like whales in the Antarctic waters.
13. Along the coast of Kurile Islands, baleen whales also feed onplanktons, Thysanoessa longipes, T. raschii, T. inermis, Calanus cristatus and C. plumchrus. Thysanoessa raschii in the Kurile waters
should be noted. Squids and swarming fish are found in the stomachs
of baleen whales and these names are described.
14. Fin whales in the Okhotsk sea feed on mainly euphausiids, Euphausia pacifica, Thysanoessa inermis, T. longipes and T. raschii.
Little piked whales are also feeding on Euphausia pacijica in the
coastal waters. Some other fish, sand lance, herring, cod and Alaska
pollack are found in the stomachs of both species of whales.
15. In the Japanese main shore whaling grounds in Sanriku and Hokkaido, the food of sei whales are euphausiids, fish and squids. The
species of euphausiids are Euphausia pacijica, Thysanoessa longipes andT. inermis in the Hokkaido waters, and Euphausia pacijica in the Sanriku waters. Among the fish, anchovy, sardin, mackerel and saury are280

T. NEMOTO

the most important species. Anchovy is dominant in the early season
and saury is dominant in the latter season of the waters. Squid (Ommastrephes sloani pacijicus) is also important in the Sanriku and Hokkaido waters. Some occurrences of Calanus copepods are also suggested.
16. Bryde's whales in the Wakayama waters take a euphausiid Euphausia similis and anchovy, and the latter is dominant in June andJuly. Bryde's whales in Bonin water take also Euphausia similis andEuphausia recurva, Myctophid and Gonostomid fish ( Yarrella microcephala and Myctophum asperum). In the catch of probable sei whales
from December to April, the occurrence of some copepods is considered.
17. In the East China sea and west Kyushu area, fin whales feed ona euphausiid Euphausia pacijica. Bryde's whales caught along thewest coast of Kyushu feed on anchovy and horse mackerel dominantly.
18. Foods of baleen whales in the other part of the world are describedaccording to published papers. The foods of baleen whales in the subtropical waters and the North Atlantic need further investigations.
19. Basing on the data of stomach contents of baleen whales, the distribution of euphausiids is discussed. New consideration on the distribution of the spineless form of Thysanoessa longipes and one and two
spine form of Thysanoessa inermis is suggested.
20. Feeding habit of baleen whales is examined. Swallowing and Skimming types are considered as feeding types of baleen whales. Blue, fin,
Bryde's, little piked and humpback whales are Swallowing type andright and Greenland whales belong to Skimming type. Sei whales takeabove two feeding methods in general.
21. These feeding types of baleen whales show some effect on theselection or preference for their food. These subjects are discussed
and the examples are given in the paper. The favourite food of baleen
whales differ in the local waters, in each whale species, and there are
selection orders among foods. These feeding types are described on eachspecies.
22. Food patchs also have characteristic features, which affect thefeeding of baleen whales. The congregation, diurnal migration and inhabiting depth of food planktons and fishes are the main factors to haverelations to the feeding habits of whales.
23. Feeding activity is considered to be active in the morning andin the evening in baleen whales of euphausiids feeder. In the shallow
water regions, the feeding activity is still high in the daytimes. Squids
are also fed mostly in the morning and in the evening, but Calanus
plumchrus is fed still in daytimes at the surface of the sea.
24. The exact weights of the stomach contents of fin whales are obtained in the northern part of the North Pacific. Fin whales take foods

FOOD OF BALEEN WHALES

281

about 100 kg to 700 kg in the full stomach condition in the North Pacific.
Bryde's whales also take foods from 100 to 200 kg in the adjacent waters
to Bonin Islands and sei whales take foods from 100 to 400 kg in the
Kurile Island waters.
25. The distribution of baleen whales in the North Pacific is discussed
considering the catch of each whaling center and the shape of the sea.
Baleen whales migrate and distribute in the sea according to the shapeof the sea. These distributional types are ' ocean denizen ' (blue, sei
and Bryde's whales), ' ocean and marginal sea denizen ' (fin, right, little
piked and grey whales) and marginal sea denizen (Greenland whale).
Some oceanographical conditions are examined to make general comprehension of the distribution of baleen whales and special characteristicsof whaling grounds.
26. Migration and movement of sei and Bryde's whales are examinedand discussed by the catch statistics and whale marking research. The
migration and the movement of Bryde's whales cover tropical, subtropical and warm temperate waters more than 20°C and never go down
to waters under 15°C.
27. Sei whales are considered to be also warmer water species thanother blue, fin and humpback whales. The movement of sei whales in
the adjacent waters to Japan has close relation to the oceanographical conditions and the distribution of their foods. The probable segregation in the composition of migrational herds of sei whales is suggested
both in the Antarctic and in the North Pacific.
28. Seasonal movement and distribution of fin whales in the North
Pacific are discussed basing on the data of the food distribution and catch
statistics. The clear movement of fin whales in the northern part of
the North Pacific following the favorable feeding area is described. A
local group of fin whales in the east China sea, which does not migrate to
the higher latitudes is suggested by the catch statistics and other biological characters.
29. The results of Japanese marking research on fin whales in thenorthern part of the North Pacific are examined in view of the seasonal
movement. The term ' dispersive movement ' is used and discussed todescribe the movement of fin whales in the northern part of the North
Pacific. But the marking research in the waters needs further investigation to reach the definite conclusion.
30. The segregation in the migration of fin whales is examined by sex,age, pregnancy and maturity of whales and physical condition of whales,
and those physical factors have close connection with the migrationalsegregation of whales in the feeding area.
31. The diatom infection is examined to study the migration of whales,282

T. NEMOTO

and it is considered not to show the typical indication of the stage of
migration, but the infection shows some indication about the migrationof whales.
32. It is desirable to accumulate the further collection of data on foodsof whales and the whale marking research to get the definite informationof whales' migration. And it is hoped to examine foods of baleen whales
in many localities of whaling grounds in the world in connection withthe oceanographical conditions for some years.

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HONJO, K. (1957). Distribution of Euphausiacea in the 'Kuroshio ' Area, South of Honshu,
May 1955. Ree. Ocearwgr. Works Japan, Sp. No., 1957.
HOTTA, H. &. OGAWA, T. (1955). On the stomach contents of the skipjack Katsuwonus
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ICHIHARA, T., (1957). An application of linear discriminant function to external measurement of fin whale. Sci. Rep. Whales Res. Inst., 11: 127-189.
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Proc. Verb. Conseil Intern. l'Exploration Mer, 56.

284

T.NEMOTOINOUE, M. & OGURA, M. (1958). The swimming-water depth for anchovy shoals in Tokyo
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MARR, J. W. S. (1956). Euphausia superba and the Antarctic surface currents (An advance~FOOD OF BALEEN WHALES

285

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286

T.NEMOTONISHIW AKI, M. (1959). Humpback whale in Ryukuan waters. Sci. Rep. Whales Res.
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FOOD OF BALEEN WHALES

287

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T.NEMOTO

288

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(1937). [Foods of whales in the far eastern waters]. Cited by Betesheva, 1955.

APPENDIX I. JAPANESE MARK RECOVERY FROM FIN WHALESIN THE NORTHERN PART OF THE NORTH PACIFIC
Body Sex
Mark length
4266
4725
4270
3369
4802
4684
4560
4658
4516
4451
4281*
4604
4543
J 5966*}J 5968*
J S6989
J 6050J S7000*
4641
J 6060*}J 6061*3243
J S7002
4267
3213
4552
4461
J 6042
J S6987
J 5995
J S7269*
4558
J S6939
J S6923
J 5979J 6511*J 6506
J S7720
J 6834
J $7026

DatemarkedDaterecovered165-45W
167-36W
167-17W
167-40W
167-27W
166-56W
166-43W
166-23W
171-02W
169-30W

54-45N
54-32N

171-50W
170-55W

0
0
0
0
0
0
0
1
1
1
1
1
1

54-06N

167-04W 54-30N

167-20W

053-44N
9- 8
9- 9
53-37N9- 9-10 53-37 N
54-lON
9-16

168-08W
164-57W 53-42N
164-57W
166-58W 55-22N

F
M
F
M
F
F
M
F
M
M
?
M
F

54-29N
1954-7- 7 1954-7- 8
ff
8-24
54-08N
8-11
ff
54-29N
ff
9- 2
ff
7- 7
53-30N
ff
9- 6
8- 6
ff
ff
54-0lN
8-11
9-13
ff
ff
9-13
54-08N
8-11
ff
ff
9-22
54-22Nff
9-21
54-lON
8-10 1955-7- 6
ff
ff
54-20N
7-17
9-13
ff
ff
7-22
54-lSN
8-10
ff
7-14-22 55-09N
ff
ff
7- 7
8- 1
53-46Nff
ff
9-11
54-20N
ff
8- 2
9-13
ff

58

M

1955-7-18

?
56

M

60

M

55
58
63
63
62
59
64
62
65

F
M
F
F
F
M
F
M
F

62
64
64
58
?

M
F
F
M

66
61
62

F
M
M

9- 3
9- 8
9- 8
ff
1954-8-10
ff

ff

ff

ff
ff
ff

Year
group

54-35N53-55N54-09N
54-00N53-40N
54-lON
54-13N54-31N54-30N54-llN

62
59
63
65
65
61
59
58
61
56
?
61
66

ff

Positionrecovered

Positionmarked9- 2166-lOW
166-55W
166-lOW
169-50W
167-03W
166-55W
165-44W
166-58W
166-21W
166-40W
165-47W
168-lOW
168-llW

169-56W

1955-9-12 1956-6-18

54-15Nff
6-23
1953-6-23
ff
7-12
1955-9- 8
ff
1954-7- 5
7-13
1953-5-12
ff
7-25
ff
7-25
1954-9-19
8-29
ff
ff
7-31
1955-9- 7 1957-5-19
ff
9- 3
ff
6-20
8-11
ff
ff
7- 2
ff
1957-6-10?
ff
7-12
1954-9-19
ff
7-18
1955-8-10
7-28
ff
7-26
ff
ff
ff
7-29
8- 5
ff
8- 8
1957-7- 8
ff
8-11
II
7- 6
ff
8-24
ff
7-19
ff
9-11 1958-5-27
ff
1955-9-15
7- 3

50-25N 170-22E 53-14N
53-37N 164-57W 54-37N
54-16N 160-lOW 54-32N
51-16N 177-50E 54-02N
54-08N 167-45W 54-50N
54-38N 165-44W 54-32N
54-08N 166-51W 52-lSN
53-42N 167-17W 49-53N
52-49N 175-16W 49-48N
55-47N 169-04W
54-08N 167-45W 54-15N
53-24N 173-05W 55-19N
56-36N 173-00W 59-58N
59-20N 176-25W 59-48N
59-05N 176-06W
56-62N 170-45W
55-37N 168-35E 53-49N
54-49N 167-04W 52-00N
54-33N 166-lOW 53-34N

165-04W
167-34W

0
0
0
1
1

?
168-33E
165-45W
165-55W
170-31W
169-54W
166-28W
162-38E
167-20W
168-12W
169-50W
169-55W
176-46W
177-58W

170-lOE
171-26E
170-45W

3
1
2
3
2
2
2
2
2
0
3
2
2
2
0
0
0
1
3

FOOD OF BALEEN WHALESAPPENDIX I.
Mark Body Sex
length

J 6837J 6831J 6815J 6264J 6843J 6829*Datemarked289(Continued)

Date
recovered

PositionmarkedPositionrecovered

Year
group

58

M

1957-9-11 1958-7- 3

54-48N

167-04W 53-42N 169-54W

1

60
56
56

F
M
F
M

7- 4
7- 7
7- 8
7- 8
7- 8

54-40N
54-15N
54-48N
54-48N
54-29N

168-47W
166--55W
167-09W
167-04W
166--43W

54-llN 170-31W
55-56N 169--09W
54-21N 166--49W62
J S7745J 6801 } 58
J 6802" 9-101956-9- 4
1957-9-11" 9-11
1958-6-24

54-49N

166-28W

1
2
1
1
0

F

1957-9-10

7-11

54-41N

168--41W 54-28N

169-44W

1

"

"
"
"

"
"
"
"
"
"

?

1954-8- 6
7-11
53-24N 169-55W 54-23N 169--30W 4
54-40N 168-47W
1957-9-10
7-11
1
54-26N 160-50W
6- 3
7-11
1
J S7243*"
50-37N 168--33W
1958-6-170
J 6859*54-42N 159-25W
1956-7-18
2?
J 6149" 7-1654-30N 168-50W 50-53N 170-lOW 1
59
J 6799
M 1957-9-10"* These marks are found in cooker or refrigerator ship and the exact position of recovery is unknown but estimate data are obtained.
3391

64

M

J 6804*

APPENDIX II. JAPANESE MARK RECOVERY FROM SEI AND
BRYDE'S WHALE IN THE NORTH PACIFIC
Mark
0876
0916
0781
1772
2058
0910
2675}
2687
0086
3826
3782
3823
2761}
2762
2769}
2770
3027 }
3043
2691 }
2692
1365

Body eDateSpecies length
S x marked

*

*
*
*

*
*
*

Date
recovered

PositionmarkedYeargroup41ft M 1950-5-21 1950-5-22 27-14N 144-14E
27-lON 144-00E
5-21
5-22 27-17 144-08
42
27-15
144--03F" 5- 8 " 7-15 26--43 142-40 Ca37-02
43 or 39 F
Ca143-02""
44
143-4025-47
F 1951-5-15 1951-5-27 25-35 143-45
8--23 1952-7- 6 41-33 147-32
44
38--31
144-16M"
8--21 27-24 144-23
44
37-51
143-22
F 1950-5-21"

1952-9- 2" 10-21 38-46

43

F

*
*
*

47
45
43
42

F 1949-7-21 1953-6-25 39-15 149-36.5
9 1953-7-10 42-27.5 148-32
F" 77- 7 1953-9--12 42-19.3 149--37.5
F"
M 1953-7- 9 1955-7-10 42-27.5 148-32

*

40

F

1952-9- 7

*

50

F

*

47

*

*

*

Positionrecovered149--25

0
0
0
0
1
2

38-24

142-26

0

38-42
42-37
38-55
40-17

143-34147-57145-37147-434
00
2

8- 8 40-15

150-01

41-26

145-533"

9-11 1955-9-15 43-08

147-5442-26

146-28

3

F

"

9-12

"

9-17 43-54

149-0543-07

147-21

3

47

M

"

9- 3

"

9-25 39-33

153-17

41-07

147-593

42

M

1950-9- 7 1956-7- 9 40-10

155-5044-53

149-306"

290

T. NEMOTO

APPENDIX II.
Mark

Body
Date
Date
Species length Sex marked recovered

2852 }
2853 Sei
46
2854
3042 Sei
422819 Sei
450775 Bryde's 423783 Sei
45
2271 Bryde's** 442334 Bryde's** 414196 Sei
47
4201 Sei

F(Continued)
Positionmarked1950-9- 5 1957-8- 5 39-25

155-32

Positionrecovered

39-30

144-01

Year
group

5

II
9-12
II
9-17 43-54 149-05
42-10
F
149-30 5
II
9- 4 1958-6- 4 39-27 154-02
37-33
M
145-30 6II
8-10 26-43 142-40
38-10
145-20 8
F 1950-5- 8II
9-29 42-19.7 149-26
41-24
145-03 5
F 1953-7- 7
33-46
136-38 7
F 1952-6-29 1959-7- 9 25-08 142-06
II
II
32-45
7- 1
7-21 26-28 142-35
136-26 7M
177-49W 4
F 1954-6-13 1958-7-22 53-26 163-22W 49-58
II
II
6-13
7-12 53-26 163-22W Ca50-00 Cal78-00W 4?
* These whale species are sei or Bryde's whales, but exact examination has not been
made at their flensing.
** These marks are found after completion of the paper, which clearly show the
migration of Bryde's whales from Bonin Islands to Oshima, Wakayama prefecture.

EXPLANATION OF THE PLATE
Showing the relative size of each foods of baleen whales
Upper: Food fish from stomachs of baleen whales in the northern Pacific. Fig. 1-Herringfrom a stomach of a fin whale in the waters off Cape Navarin. Fig. 2-Alaska pollack
from a fin whale in the Bering sea. Fig. 3-Saury from a sei whale in the waters off
Kamtchatka. Fig. 4-Atka mackerel from a humpback whale in the adjacent waters
to the Near Islands. Fig. 5-Capelin from a fin whale in the waters off Navarin. Fig.
6-Alaska pollack from a fin whale caught in the waters in the middle of Bering sea.
Fig. 7-Atka mackerel from a fin whale in the waters of Near Islands. Fig. 8-Mackerelfrom a sei whale in the waters adjacent to Japan. Fig. 9-Anchovy from a sei whalein the waters adjacent to Japan. Fig. 10-Myctophum asperum from a Bryde's whalein the Bonin Islands waters. Fig. 11-Yarella microchephala from a Bryde's whalein the Bonin Islands waters.
Middle: Food planktons in the North Pacific. Figs. 1 & 2-Thysanoessa inermis from a
stomach of fin a whale in the Bering sea. Figs. 3 & 4-Thysanaessa longipes from afin whale in the waters off Kamtchatka. Fig. 5-Euphausia pacifica from a fin whalein the waters adjacent to the Near Islands. Fig. 6-ThysanoiJssa longipes from a fin
whale in the south waters adjacent to the eastern Aleutian Islands. Fig. 7-Euphausia
pacifica from a fin whale in the East China sea. Fig. 8-ThysanoiJssa longipes froma blue whale in the south waters adjacent to the eastern Aleutian Islands. Fig. 9Calanus cristatus from a fin whale in the waters off Kamtchatka. Fig. 10-Calanus
plumchrus from a sei whale in the south waters adjacent to the eastern AleutianIslands.
Lower: Food planktons in the Antarctic waters. Figs. 1, 2, 3 & 4-Euphausia superbaof 2 years group. Figs. 5, 6, 7, 8, 9 & 10 Euphausia superba of 1 year group. Figs.
11 & 12-ThysanoiJssa macrura. Figs. 13 & 14-Parathemisto gaudichaudi.

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