FOOD OF SEI WHALE TAKEN BY JAPANESEWHALING EXPEDITIONS IN THE ANTARCTICSEASON 1967/68
AKITO KAWAMURAINTRODUCTION

The comprehensive study on the food of baleen whales caught in the Antarctic byJapanese fleets has long been treated and analysed chiefly by Dr. T. Nemoto, formerly a staff of the Whales Research Institute, on the materials collected since 1954/55
Antarctic whaling season until 1960/6l's, and several number of the important reports have beenpublished in these decades (Abe, 1957; Nemoto, 1959, 1961, 1962,
1966; Nemoto and Nasu, 1958). In addition to these studies a brief observations
on the food of baleen whales have been carried out as a part of the general biologicalinvestigations of whales (e.g. Nishiwaki and Hayashi, 1950; Nishiwaki and Ohe,
1951 etc.). One of those studies by Nemoto (Nemoto, 1959) was a summarized
fine piece of work which was comprised from the available data having been accumulated till then, which greatly contributed to increase our knowledge on thefood of baleen whales in both hemispheres. By a series of those elaborate works
several number of food organisms such as Thysanoessa macrura, Parathemisto gaudichaudii, and Drepanopus pectinatus were added to the diet list of baleen whales in the
Antarctic. However, no reports on the food of baleen whales by Japanese catchin the Antarctic waters have been appeared since 1961/62 Antarctic season onward
as well as those in the northern North Pacific.
In this report I will give a brief result of my observations on the general featuresof the food of sei whales recently taken in the Antarctic by reasons of as follows:
firstly, the catch ofsei whales in the Antarctic and also in the northern North Pacific
had been so small in proportion to the total catch of baleen whales in the earlier
days by which situation our knowledge on the food of sei whales was relatively
poor among the other baleen whales; secondly, recent increase of the sei whale
catch (see Gambell, 1968) especially by the Japanese fleets resulted a northerly or
southerly shifts of the main whaling grounds both in the Antarctic and the North
Pacific. The shift of main whaling grounds brought some new situation on the foodof sei whales there, and thirdly, there are a gradual tendency to increase the catchof fin whales in place of sei whales in the very recent operations, which may leads
to some difficulties of getting a food materials of southern sei whales in near future.
MATERIALS

In 1967/68 season of the Antarctic whaling four Japanese fleets operated in thefollowing areas (Fig. 1):
1) Area III and IV between 49°E and 100°E, chiefly in the surrounding
Sci. Rep. Whales Res. Inst.,
No. 22, 1970, 127-152.

128

KAWAMURA

waters of Kerguelen and Crozet Islands.
2) Area IV and V between 83°E and 160°W, including Tasman Sea
3) Area V between 160°E and 160°W, in the vicinity of New Zealand160°

Fig. 1.

160°w~------i-------i70°

70°

s

1so·

40°E

60°

so·

100°

120·

140°

---------'-~~--'~~s

160°

1so·

160°w

A schematic map of the Antarctic whaling grounds operated by the four Japanese
fleets in 1967/68 season. Shade with cross shows the principal whaling grounds.

The total catch of sei whales by the Japanese fleets throughout the season was
7,119 whales, from which 117 samples of stomach contents were collected, i.e. 15
samples by" Nisshin Mam No. 3" (Area IV & V), 3 samples by" Kyokuyo Mam
No. 3" (Area V), and 99 samples by" Nisshin Mam" (Area III & IV). Being on
board of the F .S. "Nisshin Mam" in her 1967 /68 operation, I made the observationsof whales food on the deck as one of the items of the general biological investigations (e.g. Nishiwaki and Hayashi, 1950) to get a considerable amount of data concerning on the food and feeding habit of sei whales in addition to the food samples.
The food samples were usually collected from the first stomach of whales while
they were flensed on the deck. Sometimes the food samples were obtained from themouth where the stomach contents being retained on the baleen plates by vomit.
The stomach contents collected were washed by rinsing them in the clear running sea
water to remove the blood or oily materials, and then preserved in vials with 10
percent buffered formalin for later examination.
One of the another materials which I used in the report was a routine record of
biological observations on whales compiled by the whalers and by the whaling inspectors of the Fisheries Agency on board. In this record a rough classifications of foodorganisms such as 'Calanus' ( =copepoda), amphipoda, euphausiids, fish, squids etc.
were adopted as a result examined by naked eyes. The positions where the samples
were obtained were represented by the every day's position of mother ships at noon.
SPECIES OF FOOD ORGANISMS

Euphausia superba had long been considered as a initial food staff of baleen whales in
the Antarctic feeding grounds, for instance, Mackintosh and Wheeler (1929), andSci. Rep. Whales Res. Inst.,

No. 22, 1970.

FOOD OF SEI WHALE

129

Matthews (1938) found none but E. superba as a food of fin or sei whales in theSouth Georgian waters. However, as the study on the food of baleen whales has
been progressed since then with the advent of a shift of main whaling ground in accordance with the composition change of the whale species hunted, several numberof euphausiids, copepods, and amphipods were gradually added to the diet list of
baleen whales (Marr, 1956; Peters, 1955; Nemoto and Nasu, 1958; Nemoto, 1961,
1962; Bannister and Baker, 1967; Best, 1967; Brown, 1968; Pervushin, 1968).
TABLE!. SPECIES OF THE FOOD ORGANISMS OF SE! WHALESCAUGHT BY JAPANESE WHALING EXPEDITIONS IN
THE ANTARCTIC SEASON 1967/68
Copepods

Amphipods

Euphausiids

FishesOthersCalanus simillimus GIESBRECHT
Calanus tonsus BRADY
Drepanopus pectinatus BRADY
Clausocalanus laticeps FARRAN
Parathemisto gaudichaudii (GUERIN)
f. compressa
f. bispinosa
Euphausia superba DANA
Euphausia vallentini STEBBING
Thysanoifssa vicina HANSEN
Gymnospelus nicholsi (GILBERT)
Myctophum subasperum (GUNTHER)
Cleodora sulcata (PFEFFER)
Clione antarctica E. A. SMITH
Eukrohnia hamata (MOBIUS)

In the materials of 1967/68 season the kind of food staff found in the stomach
contents of sei whales was relatively poor in the number of species (Table 1). Among
those species, however, I may describe the following two copepod species as being
found firstly as a presumably staple food staff of sei whale in the Subantarctic waters,i.e., Calanus tonsus Brady and Clausocalanus laticeps Farran. Judging from the number ofwhales fed on both Calanus simillimus and Calanus tonsus, they were considered to be
the most important copepods as the staple food of sei whales in the Subantarctic
waters of relatively lower latitudes. As Calanus tonsus was already described as a foodof sei whales in the South African waters in the vicinity of the Cape Province (Best,1967), this species is known to occur very abundantly in the surface waters of the
Subantarctic regions (Brodskii, 1964), especially in the south or south-east waters
off New Zealand (Farran, 1929; Jillett, 1968).
Copepods
Although Calanus tonsus was firstly described by Brady, there were some taxonomical confusion between Calanus tonsus and Calanus plumchrus of the North Pacific(Tanaka, 1954; 1956). However, the comparative morphological study of thisspecies on more closer examinations, and the finding of an adult mature male from thesouthern hemisphere made it possible to distinguish Calanus tonsus as a typicalendemic species in the surface waters of the Subantarctic (Tanaka, 1954, 1956,
Sci. Rep. Whales Res. Inst.,
No. 22, 1970.

130

KAWAMURA

1960; Brodskii, 1964; V ervoot, 1965; Jillett, 1968).
In 1967 /68 season Calanus tonsus was found in 321 sei whales which were caught
at the areas lying in the north-east ofKerguelen Island during December 12-29, andalso in the Tasman Sea during January 4 to February 2, then in the south to southeast waters off New Zealand during December 12 to March 22 (Figs. 2a-b). In the70°

80°
ST. PAUL IS.

SIC-----_... -------

+

+ +

+

45°

45°
KERGUELEN IS.

S

---~C

L_~~_J_~...£·~::....:.-k=::==:::::::Jis::====~-::-~~.J_~~-::~--:::!

60°

Fig. 2-a.

70°

80°

Positions with Calanus tonsus in the Areas III and IV.
STC : Subtropical Convergence AC : Antarctic Convergence

180°

170°

170°

35°

\

I

CHATHAM IS.

•

0

·\

o':i.,,~

BOUNTY IS. oo

ANTIPODES

I

IS.

oCo

00

40°

',
/'

r ' ....

45°

--

50°

w

170°
Fig. 2-b.

Positions with Calanus tonsus (cross), and the possible occurrence (open circle)
in the Areas V and VI.
Sci. Rep. Whales Res. Inst.,

No. 22, 1970.

FOOD OF SEI WHALE

131

whaling area so called the Area IV sei whale fed almost exclusively on Calanus tonsus
at least in the early summer season.
Calanus tonsus found in the stomach contents was usually consisted of both adultfemale and copepodite V though sometimes copepodite IV was found with copepodite
V population but very few. The upper and lower extremes of body length in the
copepodite V were 4.0 mm and 2.8 mm, and those of adult female were 4.5 mm
and 3.4 mm respectively. These body length approximately agrees with the results
having been obtained by Vervoot (1957) and Brodskii (1964). As shown in Figs. 2a-b,
the principal distributional area of Calanus tonsus widely expands in the area between
the Subtropical and the Antarctic Convergences with surface temperature of 5°150C. According to Jillett (1968) the sea temperature at 25 m depth where thehighest number of Calanus tonsus occurred was found between 8.5°C and 12.3°C in
the waters off South Island of New Zealand. There were no clear differences in the
distribution of adult female and copepodite stages.
50°

60°

src
---- --------- __ --,
...

45·

0

,

.........

-- ------ ------

••

45°
0

0 0

,........-,-50°s
40°Fig. 3.

50"

Positions with Calanus simillimus in the Area III.
Copepodite IV (cross), Copepodite V (open circle),

Adult female (square)

From the number of whales fed on Calanus tonsus, this copepod would be regarded to make one of the most important food sources for the Antarctic sei whales
during late spring to early summer. However, since Calanus tonsus of copepodite V
as well as Calanus plumchrus in the North Pacific leave the surface water in late summer for wintering in deep water (Jillett, 1968), the whaling ground formed by thiscopepod would last for but relatively short period than that formed by anotherkind of food organisms such as Euphausia superba or Parathemisto gaudichaudii.
Calanus simillimus is one of the another important endemic species which also
predominantly distributes in the Subantarctic waters (Brodskii, 1964; Vervoot,Sci. Rep. Whales Res. Inst.,

No. 22, 1970.

KAWAMURA

1321965). In 1967/68 season this food species occurred in the surrounding waters of
Crozet Islands in late January to mid February when the temperature of surface water was about 5.0°-9.10°C (Fig. 3). In the stomach contents, adult female, copepodites IV and V were occurred together though copepodite V was usually predominantamong them as well as the case of Calanus tonsus. As shown in Fig. 3 there were no
characteristic features in the geographical distributions between adult female andthe young copepodite stages. The body length varied between 2.1 mm and 3.2 mm
while those obtained by Farran (1929), Vervoot (1951; 1957), Tanaka (1960), andBrodskii (1964), were 2.86-3.42 mm in the male and 2.62-3.65 mm in the female.
Relatively small body length found in the present study may be the result that thematerial was collected at relatively lower latitudes in the Subantarctic waters thanthose collected by other workers, since the body length of Calanus simillimus shows aconsiderable meridional variations in general (Farran, 1929).

1ao·
40°

,_...

/

.....

'\

,/
/

NEW ZEALAND

\

\

...'

CHATHAM IS .

5•

' ' '.s l'',c

BOUNTY IS .

•

0

0

ANTIPODES

50°

1ao·
Fig. 4.

Positions with Clausocalanus laticeps in the Area V.

Both Calanus tonsus and Calanus simillimus are generally recognized as the typical
Subantarctic copepods, and are equally found as a staple food staff of sei whales.
It is noticed, however, that there were distinct differences in the geographicaldistributions betwen these two species; i.e., Calanus tonsus was chiefly found in the morewarmer northern waters of the Subantarctic close to the Subtropical Convergence,
while Calanus simillimus was found in the more colder waters with southerly shift of principal distributional area. The sea temperature of 10 m depth at the positions where
the bulk of them were found was never overlapped each other (see also p. 131). According to Kawamura and Hoshiai (1969), Calanus simillimus in the Indian sector of theSci. Rep. Whales Res. Inst.,
No. 22, 1970.

FOOD OF SEI WHALE

133

Antarctic disappeared at about 45°S with sea temperature 7.6°C along the meridionalline which connects between the Showa Base and Cape Town, while Calanus tonsus begin
to occur in place of Calanus simillimus in the waters north of 45°S. This fact suggeststhat Calanus simillimus prefers more colder waters than Calanus tonsus, and that thelatter must be regarded as a important food staff in the early whaling season in
the Subantarctic waters throughout the area at least Areas IV and V. Calanus
simillimus, on the other hand, could not observe in the waters south of New Zealandthrough December to March while their fairly well occurrences have been recordedin the above region (Brodskii, 1964). This species may be regarded as slightly little
important than C. tonsus since there were another food sources such as Drepanopus
pectinatus, Parathemisto gaudichaudii, and Euphausia vallentini in almost the same region.
According to the Russian investigations on the food of sei whales in the area of
Crozet Islands, Pervushin (1968) found no whales which fed on Calanoida throughDecember to February. However, as it will be described in the later the sei whales
of Japanese catch exclusively fed on copepods; Calanus tonsus, Calanus simillimus, Drepanopus pectinatus and even a so small copeped, Clausocalanus laticeps though theamount of stomach contents of these copepods was relatively few when comparedwith more larger sized organisms such as euphausiids or amphipods.
60°

70°
40°

---- .... _.... _ -----SIC ---------

0

0

..

40°
Fig. 5.

so·

----

60°

E

Positions with Drepanopus pectinatus in the Areas III and IV.

The most small sized food, Clausocalanus laticeps was found in two whales whichwere caught in the waters east of Bounty and Antipodes Islands (Fig. 4). This food,
like others was exclusively consisted of Clausocalanus laticeps of adult male, female andcopepodite V. The body length were 1.15-1.37 mm on an average. This factsuggests that Clausocalanus laticeps, like other food species, sometimes occurs in a quite
dense shoals, so called 'patchy distribution ' as to be fed by baleen whales. In
the waters off Cape Province, South Africa, the copepod, Clausocalanus arcuicornis
was fed by sei whales (Best, 1967). In South Georgian waters this species isregarded as one of the important copepods (Hardy and Gunther, 1935), and vast
numbers of occurrence was reported from the Bouvet Area and from Tasman
Sci. Rep. Whales Res. Inst.,
No. 22, 1970.

KAWAMURA

134

Sea (Vervoot, 1951, 1957). From these facts the copepods genus Clausocalanus could
be considered to have a important role as the food sources for sei whales in the Subantarctic waters or at least in the lower latitudes of the whaling Area V.
One of the another small copepods, Drepanopus pectinatus was firstly introduced
to the diet list of sei whales caught in the surrounding waters of Kerguelen Island(Nemoto, 1962). It is proved that this food was found again in 1967/68 season being
fed by a considerable number of sei whales caught in the waters between Crozet and
Kerguelen Islands. The occurrence of this copepod was more distinct in the Crozet
whaling ground than the Kerguelen's (Fig. 5 ). In the east of the Area IV and V nowhales fed on this species. It is considered that Drepanopus pectinatus make up apart of important food sources in the Kerguelen-Crozet whaling ground. It
could be said in general that the epi-planktonic copepods in relatively lower latitudesof the Subantarctic waters in the Areas III to V carry out a quite important role as
the staple food sources of sei whales which entered into the region from the north.

Amphipods
Both Parathemisto gaudichaudii forma compressa and forma bispinosa, were found in
the stomach contents of sei whales. In contrast to the northerly occurrence of copepod food, Parathemisto gaudichaudii was fed preferably in the more southerly waters
especially in the out side from the Antarctic Convergenge (Figs. 6a-b ). This species
50'

40'

60'

70'

S'\c
...... ... ---

---

-

+

40'

45'

45'

50'

50'

Fig. 6-a.

Positions with Parathemisto gaudichaudii f. compressa (cross), and f. bispirwsa (opencircle)
in the Areas III and IV.

is well known by its cosmopolitic bipolar distribution (Stephensen, 194 7) extending
far to the Hudson Strait where the northern most occurrence of P. gaudichaudii f compressa was found at 60° 23.5' N, 64° 50.5' Win Forbes Sound (Dumbar and Grainger,
Sci. Rep. Whales Res. Inst.,
No. 22, 1970.

FOOD OF SEI WHALE

135

1952; Dumbar, 1954). In the southen ocean, Baker (1954) showed its circumpolar
distribution which covers far north to the Subtropical Convergence. In the latitu~
dinal distributions, however, Kane ( 1966) demonstrated a quantitative discontinuity ofoccurrence where Parathemisto gaudichaudii is scarce at the Antarctic Convergence,
160°
45°

,.
.... ,.

,.

,, ,,

,

170°

170°

180°

•

NEW ZEALAND

BOUNTY IS.

' '§..~c

45°

---

E!)

ANTIPODES IS .

•0

CAMPBELL IS.

\

IS.

--.
0

55°

IS.

170°

Fig. 6-b.

60°

SCOTT IS.

180°

170°

160°

150°

140°W

Positions with Parathemisto gaudichaudii f. compressa (cross), and f. bispinosa (opencircle) in the Area V.

while they are rich in the north or south from the convergence. However, there
were much cases of the sei whale to feed Parathemisto gaudichaudii in the south of
the Antarctic Convergence while it is expected more abundant distribution in thenorth of the Antarctic Convergence. There are no fact to explain this curiosity.
One of a possible causes is the selective feeding by sei whales as observed between
E. recurva and Thysanoessa gregaria in the South African waters (Bannister and Baker,1967), i.e., the sei whale feed preferabley on copepod than amphipod when they occur in the same water bodies.

Euphausiids
Three species of euphausiids which were reported previously were found in thestomach contents (Table 1) though the occurrence of Thysanoessa vicina is in somedoubtful because of the ill condition of materials due to heavy digestion. Euphausia
vallentini was recorded in 1960/61 season as a principal food of pygmy blue whale(Balaenoptera musculus brevicauda) in the Kerguelen whaling ground (Nemoto, 1961),
though Mackintosh (1960) had mentioned the importance of E. vallentini as a foodSci. Rep. Whales Res. Inst.,
No. 22, 1970.

136

KAWAMURAof blue whale in the Kerguelen waters preceeding to Nemoto's report. At any rate
Euphausia vallentini could be regarded as quite important food for baleen whalesin the neritic waters of the Subantarctic as well as copepods.
60°

50°

so·

70°

35°

IS.

---

40°

0

45°
45°
0
0

'

50°

HEARD IS.

s50°
Fig. 7.

60°

70°

50°

so·

Positions with Euphausia vallentini in the Areas III and IV.

In 1967/68 season Euphausia vallentini was found chiefly in the waters between
Kerguelen and Crozet whaling grounds especially in the waters north of Crozet
Islands (Fig. 7). It was also found in the Area V between 51°-53°S and 166°1670W though very few. The northern and southern extremes of the occurrence of
Euphausia vallentini through the Areas III to IV were 43°44'S, 51°26'S, and those in
the Area V were 51°22', 53°20'S respectively. The result of Russian investigationsin the waters of Crozet Islands also shows the occurrence of Euphausia vallentini in thestomachs of sei, fin and blue whales (Pervushin, 1968). It is considered from thisfacts that Euphausia vallentini is quite important as a staple food source for sei whalesin the surrounding waters of Crozet Islands.
Euphausia superba, on the other hand, seems to be minor importance as a food of
sei whales when it is compared with Euphausia vallentini since the most sei whales werecatched in the far north apart from the principal distributional area of Euphausia
superba. In the Area IV Euphausia superba was exclusively found in the far more southof the Antarctic Convergence between 53°S and 59°S than the area of Parathemisto
gaudichaudii. In the Area V close to the Antarctica near by Balleny Islands there
were only four feeding records of Euphausia superba.

Others
The small fish, Gymnospelus nicholsi, Myctophum subasperum and other organisms;
Cleodora antarctica, Clione antarctica, and Eukrohnia hamata were found in the stomach
Sci. Rep. Whales Res. Inst.,

No. 22, 1970.

FOOD OF SEI WHALE

137

but very few. They showed only a occasional occurrence such as Electrona fishes
observed in South Georgian waters (Brown, 1968), and are considered to be a minor
importance among the food of copepods or euphausiids since these organisms were
presumably fed by a chance while they were swarming in the surface waters to feedon those copepods or euphausiids in such a situation as Currie (1953) showed in
his report.
COMBINATION OF FOOD ORGANISMS

The stomach contents of baleen whales usually consisted of a definite organisms which
TABLE 2.

STOMACH CONTENTS OF SEI WHALES CAUGHT IN THE ANTARCTICOCEAN DURING DECEMBER 12, 1967 TO MARCH 20, 1968

Kinds of stomach contents*

Number ofwhalesexamined

Calanus tonsus
C. tonsus-Parathemisto gaudichaudii f. compressa
C. tonsus-P. gaudichaudii f. bispinosaC. tonsus-Euphausia vallentini
C. tonsus-Euphausia sp.
C. tonsus-E. vallentini-Eukrohnia hamata
C. tonsus-P. gaudichaudii f. compressa-E. vallentini
C. tonsus-E. hamata-Clione antarctica & Cleodora
sulcataCalanus simillimus
C. simillimus-Drepanopus pectinatus
C. simillimus-E. vallentini
C. simillimus-Euphausia sp.
C. simillimus-P. gaudichaudii f. compressa
C. simillimus-P. gaudichaudii f. bispinosa
C. simillimus-Gymnospelus nicholsi
C. simillimus-P. gaudichaudii f. compressa-E.
vallentini
Drepanopus pectinatus
D. pectinatus-C. simillimus
Clausocalanus laticeps
P. gaudichaudii f. compressa
P. gaudichaudii f. bispinosa-f. compressa
P. gaudichaudii f. bispinosa-E. vallentini
P. gaudichaudii f. compressa-P. gaudichaudii f.
bispinosa-E. superba
P. gaudichaudii f. compressa-P. gaudichaudii f.
bispinosa-E. vallentini
P. gaudichaudii f. bispinosa-E. vallentini-C.
simil!imus
Euphausia superba
E. superba-Myctophum subasperum & Gymnospelum
nicholsi
Euphausia vallentini
E. vallentini-D. pectinatus

23
I
1

2
2

4

3
2
1

2
2

4

2
2
9
18

Dominant forms of thefood organisms
I

II

III

CV&F
CV
CV
CV& F
CV&F
CV
CV

F
F
F &Juv
FurciliaF
F

M, F &Juv

CIV& V
CV& F
CIV& V
CV
CV
CV
CV
CV
CV
M, F &Juv
Juv
F &Juv
F
FF

Juv
M, F &Juv
M & Furcilia
M&F
F

M&F
CIV, V & F

F
M&Juv

M&F

M&F

M&F

F

F

M, F &Juv

F

Juv

CV

14

M, F &Juv

10l

M, F &Juv
M&F
Juv* Quantitative importance of each food species is on decrease from left to right.

Sci. Rep. Whales Res. Inst.,
No. 22, 1970.

Juv

Juv

138

KAWAMURA

are liable to swarm in a dense shoals as Hardy and Gunther (1935) called 'patchy
distribution'. However, it is often observed that several kinds of food organisms
distribute in the same feeding ground to make the stomach contents be complex ashaving been observed in Japanese waters (Nemoto, 1959), or in the waters near to theCape Province, South Africa (Best, 1967). The sei whales, different from the case ofblue and fin whales, are considered as ' microplanktonophagi ' (Tomilin, 1954), anda considerable kinds of organisms might be an object for feeding.
In the Antarctic as shown in Table 2, most of sei whales caught in the Areas III
and IV were found to feed chiefly on small copepods such as Calanus tonsus, Calanus
simillimus, Drepanopus pectinatus, and an amphipods, Parathemisto gaudichaudii come to
the next then euphausiids, Euphausia superba and E. vallentini follow them. It isnoticed in the table that the following four species, i.e. Calanus tonsus, Parathemisto
gaudichaudii, Euphausia superb a, and E. vallentini are more likely to be fed as a monotonous
population in many cases, while the others are fed as the mixture composed of morethan two species. However, those mixture food being mingled in parallel relationship in terms of the quantity of each species are scarecely found but usually occurredwith a remarkable dominant forms among them. So it can be said that the food of sei
whales in the recent Antarctic feeding grounds or at least in the Areas III and IV, isrepresented with Calanus tonsus, Calanus simillimus, Parathemisto gaudichaudii, Euphausia
superba and Euphausia vallentini. The preference of food organisms by sei whale has
been known in the northern North Pacific (Nemoto, 1957). Nemoto (lac. cit.)
described that sei whales prefer to feed on small copepods than euphausiids, and in
the subsequent report he (Nemoto, 1959) gave the order for sei whales on this matter,i.e. small sized Calanus preferred firstly then euphausiids, small fishes or squids
follow them. In South African waters, Best (1967) demonstrated the same order for
sei whales though there were so scarce instances of mixture of food more than two
species. My result agrees in general with the result of those previous workers
though I consider that Parathemisto gaudichaudii should be added and placed in thenext to euphausiids at least in the Indian sector of the Subantarctic waters.
FEEDING PERCENTAGE

The kind of stomach contents of each baleen whales is usually observed by eyes, andrecorded according to a rough classifications, i.e. Calanus (=copepoda), amphipoda,
and euphausiids as shown in Table 3. A symbol " Calanus " in the table does notmean exact taxonomical nomenclature but actually means " copepoda ". Euphausiids are divided into three classes according to their body length after themanner adopted by Mackintosh and Wheeler (1929) and other Japanese workers
thereafter; L: large (50 mm-), M: medium (40-50mm), and S: small (-40 mm).
It can be considered in this report that the large and medium sized euphausiids aremostly represented by 1 or 2 year group of Euphausia superba, and small one by Eupahusia vallentini. Although " empty", the whales of no stomach contents was the mostcases among examined whales, it is noticed in the table that the feeding percentage
of Calanus gradually increases toward the Pacific sector of the Antarctic (Areas V andSci. Rep. Whales Res. Inst.,
No. 22, 1970.

FOOD OF SEI WHALE

139VI) from the Indian sector, while amphipoda makes a important food sources in
the Indian sector of the Antarctic (Areas III and IV). It must be noted that relatively low feeding percentages of Calanus in the Areas III and IV are the result
from a short duration of whaling in the Subantarctic waters. By supposing the caseabove mentioned, it might be nearly as same with other food species. Euphausiids
are also more important in the Areas IV to VI than the Areas III and IV. No
occurrence of large and medium sized euphausiids from the Areas V andIV suggests the complete absence of Eupahusia superba from these two whaling
grounds. It is interesting that the sei whales in the south of New Zealand almost
exclusively fed on small sized euphausiids which were consisted of Euphausia vallentini. Sei whales in the Areas III and IV chiefly feed on copepods in December.
TABLE 3. NUMBER OF SEI WHALES IN RELATION TO THE KINDS OF FOOD
AND WHALING AREAS IN THE ANTARCTIC SEASON 1967/68.
THE PERCENTAGES TO THE TOTAL NUMBER OF WHALESEXAMINED ARE GIVEN IN ITALICS.
Kind of stomach contents
Area & Sector

Area III & IV
(Indian Ocean)
Area IV & V(Tasman Sea & Pacific
Ocean)
Area V & VI
(Pacific Ocean)
1)
2)
3)

"Calanus"

Amphipoda

207 1 >
13.64
357 2 >

Euphausiid

Unknown•>

Empty

Total

59
3.89
203

919
60.54
537

1518

16.27

43.03

L

M

s

191
12.58
73

115
7.58
61

23
1.52
17

28.61

5.85

4.89

1.36

888
34.82

70
2.75

575
22.55

9
0.35

1008
39.53

1248

2550

Including Drepanopus pectinatus.
Including Clausocalanus laticeps.
Not examined.

A considerable high percentages of empty stomach in those areas suggests a poor
availability of copepod food, since there is a fact that the Russian investigation madeon the sei whale caught in the vicinity of Crozet Islands showed low feeding percentages due to the proportional increase of Calanoida among other food organisms(Pervushin, 1968). It is also noticed that relatively high percentages of amphipoda
and large sized euphausiids in the Areas III and IV mean the formation of staple
feeding ground of sei whale in relatively higher latitudes. These are, however
do not always be accompanied by the distribution of sei whales since they liable tofeed on copepod in the lower latitudes by ' skimming' even if the population densityof copepods is poor. The most of sei whales caught in the Calanus ground in lower
latitudes of the Areas III and IV had a small quantity of stomach contents less than
50 percent, and no whales with the stomach of" full" were observed. As it is shownin the Figs. 2a to 5, a chief diet in the lower latitudes of the Area III and the surrounding waters of Crozet Islands during December and late January to mid February was represented by Calanus tonsus, Calanus simillimus, Drepanopus pectinatus and Euhausia vallentini. Pervushin (1968) on the other hand, demonstrated a quite different
Sci. Rep. Whales Res. Inst.,
No. 22, 1970.

140

KAWAMURA

result. Mentioning on the feeding behavior of baleen whales in the area of Crozet
Islands, he (Pervushin, 1968) showed that 63.0-88.5 percent of sei whales wereproved to feed on euphausiids such as Euphausia vallentini and E. frigida during December to February. He also showed that the real Antarctic copepods, Calanus
propinquus and Calanoides acutus were found as a food of sei whale in the Crozet whaling
ground. However, judging from the negative records of those two species in my collection from those waters, and also the negative record shown by Brodskii (1964),
and positive records in the southern waters far beyond the Antarctic Convergence bymany workers (e.g. Tanaka, 1960, 1964; Kawamura and Hoshiai, 1969), the occurrence of Calanus propinquus and Calanoides acutus in the surrounding waters of Crozet
Islands is considered in some doubtful, since they are regarded as a real endemic
species in the high Antarctic (Ottestad 1932, 1936), and C. propinquus is found usuallyat the depth of 100-250 m in the north of the Antarctic Convergence where the sea
temperature lies between -l.6°C and 0.3°C (Vervoot, 1957). On the other hand,the observed temperature in the waters of Crozet Islands during January to February in 1967/68 season was quite high between 5.0°C and 9.0°C, where Calanus
simillimus, a typical subantarctic species was exclusively fed on.
LATITUDINAL SUCCESSION OF FOOD ORGANISMS

Among four Japanese fleets operated in 1967/68 season two of them fished aroundso as to cover a relatively wide area in meridional direction. In Figs. 8-9, thesuccession of food organisms in the north-south direction in terms of the feeding
percentages is shown with approximate positions of the Subtropical and the Antarctic
Convergences in the area concerned. In the Subantarctic waters of lower latitudesof the Indian sector of the Antarctic, only" Calanus "was fed by sei whale. " Calanus " in this area was represented by a typical Subantarctic endemic species; Calanus
tonsus, Calanus simillimus and Drepanopus pectinatus. Although Calanus tonsus andCalanus simillimus showed somewhat similar charactor in their geographical distribution, it must be kept in mind that there was a time lag about a month in the time of
their occurrence, i.e., Calanus tonsus was found exclusively in December while Calanus
simillimus was in mid January to February. Still more, there are the fact to suggest
the presence of some ecological differences between these two copepods; the former
prefers more warmer water (7.0-13.4°C) than the latter (5.9-9.1°C). According to theplankton data obtained by the 7thJapanese Antarctic Research Expedition (Kawamura and Hoshiai, 1969), the boundary where alternation of the successive occurrence of Calanus tonsus to Calanus simillimus takes place was found at approximately
45°S with temperature and salinity of 7.5°C and 34.07°/00 respectively. The highfeeding percentages at 45°S as shown in Fig. 8 would be due to the result fed on
Calanus simillimus and Drepanopus pectinatus in the Crozet whaling ground. The
dominant occurrence of copepods in the Subantarctic waters is clearly shown in
Figs. 8 and 9 though Euphausia vallentini makes one of another chief food sources in
the Pacific sector of the Antarctic.
An amphipoda, Parathemisto gaudichaudii comes next to copepods in fairly narrow
Sci. Rep. Whales Res. Inst.,
No. 22, 1970.

141

FOOD OF SEI WHALE

latitudinal zone which lies in the slightly north of the Antarctic Convergence. It
must be noted that almost complete alternation of chief diet of sei whales from
copepods to Parathemisto gaudichaudii takes place in the south of Subantarctic waters,

STC
80
70

AC
-·--·- Eu ( L)--Total- - - Calanus-----Eu(M)------ Amphipoda------- Eu ( S )~60

I"'~ 50

I

("

\ f.

(.)

I

~40

\I

,.
'<

'

"'-....

'i

bO

:6 30
"' 20
LL

-,

\.

/\

Q)

1·

'I

\

I ',
I

I

/"....

\

/

I

•'

'

I . •

/·-:!_----~~
'·

u 59°

55°

50°

45°

11,~
1

'

.i
I
•

Lat. ( S)
Fig. 8.

Latitudinal succession of the food organisms of sei whales in the Indian sector of the Antarctic.
STC : Subtropical Convergence AC : Antarctic Convergence

STC-Total--Calanus-----Amphipoda

Cl)

AC

17

---Eu( L)---·-·-Eu ( M )----Eu( S)

bO

"'c

I

~

Cl)

60
Cl. 50
bO
c 40
"D
30
LL
20
10
0
42
u

~

A

Cl)

i

/\,

i

, • I
\ '

1\·'

/I

ii ..c

;i

-B

"'U

Cl)
Cl)

~

i

I

;

I

-'
65
/

45

50

55

60

68

Lat.(S)
Fig. 9.

Latitudinal succession of the food organisms of sei whales in the Pacific sector of the Antarctic
including the Tasman Sea.
STC : Subtropical Convergence AC : Antarctic Convergencei.e., both amphipoda and copepoda hardly coexist with each other so as to makeup a food of sei whales in the same area. One of the causative reasons for a quite
high feeding percentages in Fig. 9 would be in the curious distributional featuresof Parathemisto gaudichaudii which was demonstrated by Kane (1966, p. 176, Text-fig.
6). He (1966) describes on this matter, "but there are evidently two zones in which
it is particularly abundant. These are separated by a belt in the vicinity of the
Antarctic Convergence in which the population is small ".
Sci. Rep. Whales Res. Inst.,.No. 22, 1970.

142

KAWAMURA

In the south of the Antarctic Convergence higher than 53°S, the large sizedeuphausiids consisted of Euphausia superba begin to appear in place of Parathemisto
gaudichaudii in the Areas III and IV though sometimes small or medium sized individuals which are represented by adolescent of Euphausia superba appear as a supplemental food sources. In the Area IV and V, chiefly the Pacific sector of the
Antarcic the general features of latitudinal succession of food organisms could beconsidered to follow the same pattern with those observed in the Indian sector. It
is also noticed in Fig. 9 that small sized euphausiids consisted of Euphausia vallentini
seems quite important food sources in the Subantarctic waters in the vicinity of the
Antarctic Convergence where the sudden diminution of population size of Parathemisto
gaudichaudii takes place. Brown (1968) thought that Parathemisto gaudichaudii fed by
sei whales in South Georgia might have been fed in the far northen waters than
the food of euphausiids such as Euphausia superba. In the southern water far beyond
65°S, a considerable number of medium sized euphausiids consisted of I-year groupof Euphausia superba were fed by sei whale.
FEEDING TIME

General features
The fin and blue whales were the main species having been caught previously,
and fin whales were the most well studied on their feeding habit. Sei whales on theother hand, were known a little due to so quite few catches among the baleen whales.
It has been known that the feeding activity of baleen whales in a day in terms of thepercentages varies in general with a bimodal curve which has a maxima in the earlymorning and in the evening (Nemoto, 1957, 1959). One of his results (Nemoto,1957) suggests that baleen whales somewhat actively feed twice a day in many cases
though each patterns of feeding activity are variable with the kind of food partaining
to their diurnal vertical movement, seasons, latitudinal positions, or sometimes withthe bottom topography of whaling grounds. Finding myctophid fishes, Electrona
subasper and Electrona normani, Brown (1968) suggested that sei whale is more likely tofeed actively in the twilight evening in the South Georgia. Sometimes, however, thebaleen whales show a evidence suggesting to feed only once a day (Nishiwaki andOhe, 1952). In any case, it is considered to be quite important to accumulate theevidences on the feeding habit of baleen whales especially of sei whales in relation toestimating the nutritional budget among the food webs in their feeding grounds.
However, it is also nesessary to figure out the feeding patterns of baleen whales bytheoretical and experimental methods by assuming such a feeding model as
Klumov (1961) instituted for this purpose.
The daily change offeeding activities in terms of the percentages of the stomach
with food against the whole number of stomach examined is supposed to be affected
chiefly by the diurnal vertical migrations of food organisms, because the most of
all food organisms listed in Table 1 were known as to show a quite distinct diurnalvertical migrations in the South Georgian whaling ground (Mackintosh, 1934,
1937; Hardy and Gunther, 1935; Ommanney, 1936). Accordingly, it is necessary
Sci. Rep. Whales Res. Inst.,
No. 22, 1970.

FOOD OF SEI WHALE

143

to examine the whales food by the species since each food organisms has their own
peculiar migratory patterns in a day. The feeding activity by the five kinds offood organisms is shown in Figs. 1Oa-b. Fig. 1Oa demonstrates the feeding activity

Cl-Total- - - Eu( L)60- - Ca/anus- - - Eu(M)50----- Amphipoda--·-··- Eu( S)

DO

2

c

(])

40

~

~

30

bO

~ 20
(])

(])

lL

9

10

11

12

13

14

15

16

17

18 19

20

Hour
Fig. 10-a.

Feeding percentages of sei whales by the kinds of food organisms in the Antarctic, Areas
III and IV.

90

Total

---Eu(L)80

Ca/anus----- Eu(M)Amphipoda------- Eu( S)

70
(])

bO

<U
......

60

c

(])
(.)

'"-

50

(])

Cl.

bO

c

<::>
(])

(])

40
30

lL

20
10
0
5

6

7

8

9

10 11

12 13 14 15 16 17 18 19 20 21

22

Hour
Fig. 10-b.

Feeding percentages ofsei whales by the kinds of food organisms in the Antarctic, Area V.

in the whaling Areas IV and V, while Fig. lOb does the Areas III and IV. It
is noticed in the figures that a quite high feeding percentages are observed in the earlymorning, and no distinct recovery occurs in the evening. It is also noticed that themost causative organisms to bring on the daily variation of feeding activity are chiefly
responsible in the case when amphipoda, large sized euphausiids or " Calanus" were
Sci. Rep. Whales Res. Inst.,
No. 22, 1970.

144

KAWAMURA

fed. Medium or small sized euphausiids seems to be fed whenever they are available.
The upper and lower extremes of feeding percentages were 57 percent and 28 percent
in the Areas IV and V, and that in the Areas III and IV were 82 percent and 25 percent respectively. The general trends offeeding activity ofsei whales in the Subantactic waters differ considerably from those of fin and sei whales obtained in the northern North Pacific where it varied between 0 to 100 percent in most cases (Nemoto,1957). This may be attributed partly to the differences of the kind of food organisms
taken iri both whaling grounds. From the figures, it is naturally considered that themost of sei whales in the Antarctic heavily take a dense population of food once in themorning possibly by ' swallowing ' or ' skimming ', and take a relatively scatteredpoor population of food organisms by ' skimming ' during the daytime towards theevening, as the manner described by Ingebrigtsen (1929) and Nemoto (1957, 1959).

The case of Calanus tonsus and Calanus simillimus
The components of the " Calanus " food are represented by two dominant
species, Calanus tonsus and Calanus simillimus. In the Indian sector of the Antarctic
a considerable number of both Calanus tonsus and Calanus simillimus occurred as
principal food sources of sei whales while only Calanus tonsus was observed in the
Tasman Sea and in the Pacific sector of the Antarctic (Area IV and V). As there
Calanus simillimus

10 Ur"'(f)Q)

0
10 "rr"

30

0

20

'--

;;:

0

10 "rrr"

E

:J

.D

c:

E

z

'--

Q)

.0

Q)

:J

"'

-"'

"';;:

-"'

0

(f)
Q)

0
10 "R"
0

4

10

(ii

0

I-

5

6

7

8

9 10 11 12 13 14 15 16 17 18 19

0

Hour

Fig. 11-a.

Frequency of the number of whales fed on Calanus simillimus by the four different
degrees of stomach repletion in a day.
Degree of repletion :" r" : less than 25 percent"rrr ": 50-75 percent"rr": 25-50 percent"R" : 75-100 percent

are considerable differences of the behaviour of diurnal vertical migration between
Calanus tonsus and Calanus simillimus the extent of the repletion of stomach contents by
the time was also differed in these two copepod species (Figs. l la-b ). In both Calanus
tonsus and Calanus simillimus, the repletion of stomach was relatively small with theSci. Rep. Whales Res. Inst.,

No. 22, 1970.

FOOD OF SEI WHALE

145

quantity of food less than 50 percent during the daytime. It is noticed clearly that thealmost fully repleted stomachs (" rrr "-" R ") with Calanus tonsus occurred more frequently than Calanus simillimus, and the former was fed with a same feeding percentages during the daytime while the bulk ofCalanus simillimus was exclusively fed onlyin the evening. This fact would be the result from being exactly followed to thedifferences of the migratory habit of both species. According to Hardy and Gunther(1935), Calanus simillimus is regarded as one of the quantitatively important copepods
in the South Georgian waters, and this species shows a distinct diurnal verticalmigration as well as Drepanopus pectinatus; the bulk of Calanus simillimus population
begins upward movement at about 1700 hours in the evening and reachs to 10-20 m
depth at 1800 hours. They remain at the surface layer during the night then begin
to move into the deep down to about 100 m depth in very early morning at least
02-03 hours. This behavior leads to the consideration that there would be only achance for sei whales to feed on Calanus simillimus in the evening in a day. It isinteresting to find that the stomach of " full " occurred very frequently in theevening so as to support the consideration of feeding ' once ' in a day.
Calanus tonsus

10

([)

~
CU

40

"r"

CJ)

0
10 "rr"30 <ii"'

0
10

20

.s::

:;:;

.s::
:;:;

0
~

"'E

0
"rrr"

.Q

::l

z

~

"'E

.Q

::l

c

0
10 "R"
0

CU

10 0

f-

0
4

5

6

7

8

9
Hour

Fig. 11-b.

Frequency of the number of whales fed on Calanus tonsus by the four different
degrees of stomach repletion in a day. Legend as in Figure 11-a.

Calanus tonsus, on the other hand, is a comparable species to Calanus plumchrus
in the northern North Pacific, and this species is recognized in general to show nosuch a distinct diurnal vertical migration as Calanus simillimus. Judging from its
hydrological and taxonomical affinities to Calanus plumchrus (Tanaka, 1954, 1956;
Jillett, 1968) at least in the 5th copepodite stage, it might presumably be consideredthat Calanus tonsus of 5th copepodite stage does not show any distinct diurnal migration. The occurrence of" full" or "rich " stomachs of Calanus tonsus during thedaytime suggests a quite well availability of this copopod in the surface waters so as tobe fed by sei whale throughout a day.
Sci. Rep. Whales Res. Inst.,

No. 22, 1970.

146

KAWAMURAAMOUNT OF STOMACH CONTENTS

It has long been the obscure mystery or the matter of interest how much thebaleen whales take a food in a day. According to Nemoto (1959). Collet (1912)
earlily estimated the amount of food taken by the Atlantic blue whale, and showedthat they had taken at least 1,000 liters of euphausiids. Betesheva (1954) showedthat the North Pacific sei whale can feed 600 kg of squids or 50-370 kg of Calanus
plumchrus, while Best (1967) given 59 kg of zooplankton from South African waters,
and 175 or 305 kg of krill for Antarctic sei whales (Brown, 1968). There are somemore data about this problem which has been accumulated on the whales of northern hemisphere though most of them were on fin whales (e.g. Nishimoto, et al.,1952; Nernoto, 1959; Klumov, 1961). Nemoto (1959) demonstrated that the fin
whales of 57 feet in the northern North Pacific fed on 759.0 kg. of Alaska Pollack
and found a considerable variations in the amount of stomach contents (91.0759.0 kg) notwithstanding the fact that the majority of all stomachs concerned wererepleted as " full " by eyes. His result also suggests that the weight of stomach
contents filled with copepods usually very little than those by fishes or euphausiids.
TABLE 4. AN AVERAGE AND THE MAXIMUM AMOUNT OF STOMACHCONTENTS OF SEI AND FIN WHALES IN THE ANTARCTIC
AverageWhalespecieslBodylength(m)

13.0-13.9
14.0-14.9

Sei whale
115.0-15.9
16.0-16.9

j18.0-18.9l20.0-20.9

Fin whale

21.0-21.9
22.0-22.9

Sex

Numberof whaleexamined

F
M
F
M
F
M
F
M

2
0
2
5

F
M
F
M
F
M
F
M

0

3

MaximumTotalweight(kg)

Volume(1)

Totalweight(kg)

Volume
(1)

171

202

182

204

118
116
152
159.2
196.5

149
140.4
200
208.5
255

141.3
154.6
152
228
196.5

180
200
200
312
255

301.3
567

391
700

301.3
567

391
700

510
133

700
238

885
133

1000
238

0

0
0
2
1
0

In the Antarctic, as I showed in a brief note (Kawamura, 1968) the amount of
stomach contents of 14 sei whales which fed on Calanus tonsus, Parathemisto gaudichaudii,
Euphausia superba and Euphausia vallentini was measured (Table 4). The weighingof stomach contents were carried out on the stomachs being judged as "full" byeyes, and full data including fin and minke whales were given in Appendix. The
Sci. Rep. Whales Res. Inst.,
No. 22, 1970.

FOOD OF SEI WHALE

147

highest value observed was 228.0 kg of Parathemisto gaudichaudii, which was fed by
15.2 m of male, while it was only 68.0 kg in the Calanus tonsus food. Nemoto (1962)
mentioned that there were quite well agreement between the weight and the degreeof replation of stomach judged by eyes. However, as shown in Appendix there
were considerable variations in the case of the Antarctic sei whale. It can be said
in general that the whales caught before 0900 hours carry somewhat fresh and large
amount of stomach contents, and their proportional weight of water gradually increases toward the noon due to digestion.
The highest and averaged amount of stomach contents show that the males ofboth sei and fin whales likely to feed on much food than the females though feeding
percentage seems to be high in the female (Brown, 1968). It is noticed that thestomach is hardly repleted when the whales feed on copepods than fish or euphausiids. This fact leads to a consideration that the larger the size of food organisms, thelarger amount of stomach contents is expected. Such a tendency is also shown in
the North Pacific fin whales (Nemoto, 1959, Table 24). From my result I may
describe the following weights as an approximate amount of stomach contents
usually seen in the Antarctic:
Sei whales:
Fin whale:
Minke whale:less than 100 kg
Copepoda
Amphipoda 150-250 kg
Euphausiids 150-200kg
Euphausiids 300-900kg
Euphausiids 30 kg

1

By comparing these values with those obtained by other workers (e.g. Klumov,
1961; Brown 1968), the amount of stomach contents of sei whale in the Antarctic
does not differ so much from those obtained in the northern North Pacific.
SUMMARY

1. . In the Antarctic whaling season 1967 /68 four Japanese fleets operated in
the whaling Areas III-V, and 7,119 sei whales were caught during the season.
2. · The general biological observations such as the body length, thickness of
blubber, mammary gland etc., including the stomach contents were carried out
on every whales. In addition to this 117 samples of the stomach contents of sei
whale were obtained from three fleets for taxonomical and biogeographical study offood organisms.
3. The quantitatively important food organisms found in the samples were:
Euphausia superba, E. vallentini, Thysanoessa vicina( ?), Calanus tonsus, C. simillimus, Clausocalanus laticeps, Drepanopus pectinatus and Parathemisto gaudichaudii. Two of them,i.e., C. tonsus and Clausocalanus laticeps seems to be recorded for the first time here as
the staple food sources of the Antarctic sei whale.
4. Both C. tonsus and C. simillimus are recognized as a endemic species of Subantarctic waters. C. tonsus, however, seems more characteristic in the northern warmer
waters with sea temperature of9.50-12.0°C while C. simillimus is distinct in the more
Sci. Rep. Whales Res. Inst.,
No. 22, 1970.

148

KAWAMURA

colder waters with sea temperature of 5.0-9.l0°C.
5. In the whaling grounds south of New Zealand and in the Tasman Sea,
Calanus tonsus is the most important food species for sei whale while C. simillimus, C.
tonsus, Drepanopus pectinatus and Euphausia vallentini were important in the surrounding waters of Crozet Islands.
6. The occurrence of Calanus propinquus and Calanoides acutus as the food of sei
whale in the waters near to Crozet Islands by Russian investigation seems to be lessprobable or quite unusual by the fact that those two copepod species are the real
Antarctic species being found in more higher latitudes, and also no reports mentioning on the occurrence of these copepods in such a northern warmer waters as 46°S.
7. Judging from the general composition of stomach contents the sei whale
chiefly feeds on a monotonous population of food organisms, i.e., there were so few
cases of mixture food.
8. The feeding percentages of sei whale were relatively low especially in thecase of "Calanus" food. "Calanus" is, however, the most important food in the whaling Area V, while it was replaced by Parathemisto gaudichaudii in the Areas III and
IV. Euphausia vallentini, on the other hand, was preferably fed throughout the Areas
III to V.
9. The chief diet of sei whale showed a clear latitudinal succession from thenorth to the south in the following order: Calanus tonsus-(Clausocalanus laticeps)Calanus simillimus, Drepanopus pectinatus, Euphausia vallentini-Parathemisto gaudichaudii-(P. gaudichaudii, E. superba)-Euphausia superba
10. Sei whale actively feeds twice a day in general though the feeding activity
varies considerably with the kind of food species which have a peculiar pattern of
diurnal vertical migration. The sei whale when feeds on C. simillimus could presumably feed them once in the evening while it is expected to feed twice or anytime ina day in case of C. tonsus food.
11. The amount of stomach contents of sei whale usually large when euphausiids or amphipods are fed. It is considered that the larger the size of food organisms the larger amount of stomach contents are expected. The Antarctic sei
whales with " full " stomach proved to carry a crustacean food of approximately
150-200 kg.
ACKNOWLEDGEMENTS
I am greatly indebted to Dr. H. Omura of the Whales Research Institute who gave
me a chance to participate in the Antarctic whaling expeditions in the season 1967/
68. My hearty thanks are also due to the kind considerations of the Fisheries Agencyof the Ministry of Agliculture and Forestry, and Taiyo Gyogyo K.K. through which
I could make my biological investigations quite smoothly on boad of the factory ship
" Nisshin Maru " throughout the expedition. To examine and collect the foodmaterials on the ship, I got a extensive assistances from Messrs. M. Kosaka and G.
Izumi, the whaling inspectors from the Fisheries Agency, and their kind co-operation
is greatly appreciated.
Sci. Rep. Whales Res. Inst.,
No. 22, 1970.

FOOD OF SEI WHALE

149

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ABE, T., 1957. Notes on fishes from the stomachs of whales taken in the Antarctic. Sci. Rep. Whales Res. Inst.,
12: 225-33.
BAKER, A DE C., 1954. The circumpolar continuity of Antarctic plankton species. Discov. Rep., 27: 201-18.
BANNISTR, J. L. and A DE C., BAKER, 1967. Observations on food and feeding of baleen whales at Durban.
Norsk Hvalfangst-Tid., 56 (4): 78-82.
BEST, P. B., 1967. Distribution and feeding habits of baleen whales off the Cape Province. Invetl. Rep. Div.
Sea Fish. S. Afr. 57: 1--44.
BETESHEvA, E. I., 1954. Nekotoryye dannyye o pitanii usatykh kitov rayone Kuril'skoy gryady. (Data on
the feeding of baleen whales in the Kurile region.) Trans. Inst. Oceanogr. Acad. Sci. USSR, 11 : 238--45.
BRODSKII, K. A., 1964. Distribution and some morphological features of the antarctic species of Calanus(Copepoda). Issled. Fauny Morei 2: 189-250.
BROWN, S. G., 1968. Feeding ofsei whales at South Georgia. Norsk Hvalfangst-Tid., 57 (6): 118-25.
CuRRIE, R., 1953. Food resources of the sea. The Time Sci. Rev.,: 1-8.
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No. 22, 1970.

150

KAWAMURA

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AUTHORS' NOTE
In the course of this paper being submitted for publication a quite interesting paper by D. E. Sergeant (Feeding rates of cetacea. FiskDir. Skr. Ser. HavUnders., 15: 246-58, 1969) appeard. Following
Ivelev (1961) Sergeant proposed to use the term "Feeding rate" as a index daily ration expressed aspercent of body weight.
"Feeding percentage" used in this paper and also in Nemoto (1957, 1959) basically differs from
Sergeants', i.e., the term means the ratio : number of whales with food/total number of whales examined.
Although both terms differ as they are, it is considered that Sergeants' proposal would be reasonable,
and much care will be payed to avoid any confusion when those matters are expressed in "Feeding
percentage".

Sci. Rep. Whales Res. Inst.,
No. 22, 1970.

::;.

S<

~

~
:>:I

;;:, "::::i ~""~!'V~......

?:
~
~ ~·

M
M
M
M
M

M

M

M

F

F

Species

Sei

Sei

Sei

Sei

Sei

Sei

Sei

Sei

Sei

Sei

No. ofwhales

300

427

609

324

462

612

1397

554

1477

534

Sex

APPENDIX.

13.2

13.0

15.l

14.7

15.1

15.2

14.6

14.2

14.1

14.4

Body
length
(m)

Eu-S

Eu-L

Eu-S

Eu-L

Amphipoda

Amphipoda

Amphipoda

Amphipoda

Amphipoda

CalanusStomachcontents

51°12's
72°5l'E
51°05'S72°25'E
56°14'S
81°00'E
47°50'S
70°36'E
57°10'S
83°38'E
47°52's
70°33'E

86°061 E

I '68

12

23

13

21

15

7

I '68

II '68

I '68

II '68

I '68

I '68

30 XII '67

15

I '68

28 XII '67

45°25'S85°39'E
50°37'8
74°05'E
51°05'S73°25'E
47°2l'S
6

Date
taken

Position
taken

1940

0830

1345

1050

1455

0925

1105

0800

0600

1115

Time
(L.T.)

135.6

149.0

149.6

142.0

57.6

200.0

98.0

73.5

136.5

54.0

Net
weightof food
(kg)

24.4

33.0

28.6

0.0

13.8

28.0

30.0

14.5

18.l

14.0

Water
(kg)

160.0

182.0

178.2

142.0

71.4

228.0

128.0

88.0

154.6

68.0

Total
weightofstomachcontents(kg)

AMOUNT OF FOOD TAKEN BY THE ANTARCTIC FIN, SEI AND MINKE WHALES.
(" NISSHIN-MARU" FLEET IN 1967/68)

204

200

220

200

93.6

312

156

109.2

171

66

d)

d)

a)

c)

b)

a)

Volume Remarks
(I)

l'Tj

'-"

--

i:'1

>-I:""

::r:

~

rJ:>

i:'1
......

0l'Tj

t:I

0
0

;""·

?-

S'

~

.,.,

~"'
~

~~

-""._ ~

""~

~

~~

F

F

Fin

Minke

706

6

F

Fin

1384

Eu-L

8.0

56°24'8
80°46'E
47°52's
70°33'E
57°IO'S
83°38'E
55°10'878°2l'E
57°1 l'S
72°22'E
54°36'S80°42'E
54°12'8
79°35'E
56°14'8
8! 0 00'E
57°1 l'S
72°22'E
57°1 !'s
72°22'E
I '68

I '68

II '68

I '68

II '68

21

21

21

20

1115
1805

I '68

0550

0640

0820

1015

0855

0540

1745

0925

I '68

II '68

II '682 III '68

21

18

23

12

22

37.5

159.0

22.4

127.4

556.5

286.0

785.0

4.0

5.6

10.5

28.0

100

27.6

4.0

148.0

273.7

15.4

12.6

79.1

128.7

26.4

133.0

567

314.0

885

301.3

196.5

152.0

94.5

141.3

31.2

238

700

400

!OOO

391

255

200

119

180

e)

e)

e)

Calanus: Calanus tonsus, Amphipoda: Parathemistogaudichaudii, Eu-L or -M: Euphausia superba, Eu-S: Euphausia 111llentini (except no. 665)a) Approximate values.
b) Estimated by the stomach volume averaged on 13 sei whales.
c) Calculated by the mean weight of a unit volume of amphipod food of 4 sei whales.
d) Calculated by the mean weight of a unit volume of small-sized euphausiids taken by no. 532 sei whale.
e) Calculated by the mean weight of a unit volume of large-si;:ed euphausiids taken by 6 fin whales and I minke whale.

Eu-L

Eu-L

Eu-L

22.1

20.2

21.l

M

Fin

1376

Eu-L

21.0

M

Fin

1608

Eu-L

!8.6

Fin

699

M

F

Sei

665

Eu-LMS

Eu-L

15.6

F

Sei

1471
16.2

Eu-S

14.7

F

Sei

532

Eu-L

14.3

F

Sei

1437

(Continued)

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-

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c:::

~

~

~

N>