THESCIENTIFIC REPORTS
OF

THE WHALES RESEARCH INSTITUTE
No. 26

THE WHALES RESEARCH INSTITUTETOKYO· JAPANNOVEMBER 1974l--;;~~lRu. Inst., No. 26~~~-........---

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THE
SCIENTIFIC REPORTS
OF
THE WHALES RESEARCH INSTITUTE
No. 26

THE WHALES RESEARCH INSTITUTETOKYO, JAPANNOVEMBER, 1974

THE WHALES RESEARCH INSTITUTE
1-3-1, ETCHUJIMA, KOTO-KU, TOKYO

THE SCIENTIFIC REPORTS OF THE WHALESRESEARCH INSTITUTE
CONTENTS OF NUMBER 26Page

OMURA, H.
Possible migration route of the gray whale on the coast of Japan . . .
SATAKE, Y. and OMURA, H.
A taxonomic study of the minke whale in the Antarctic by means of hyoidbone . . . . . . . . . . . . . . . . . . . . . . . .
. . . . .
15
KAWAMURA, A.
Food and feeding ecology in the southern sei whale .
25
McCANN, C.
Body scarring on cetacea-odontocetes . . . . . . . .
145
KAsUYA, T., MIYAZAKI, N. and DAWBIN, W. H.
Growth and reproduction of Stenella attenuata in the Pacific coast of Japan.
157
MIYAZAKI, N., KASUYA, T. and N1sHIWAKI, M.
Distribution and migration of two species of Stenella in the Pacific coast ofJapan . . . . . . . . . . . . . . . . . . . . . . . . .
227
KAMIYA, T. and P1RLOT, P.
Brain morphogenesis in Stenella coeruleoalba
245
CASTELLO, H.P., ToMo, A. P. and PANIZZA, J. S.
First Antarctic record of a killer whale stranding .
255
KAMIYA, T. and MIYAZAKI, N.
A malformed embryo of Stenella coeruleoalba . . . .
259
KAMIYA, T. and YAMASAKI, F.
Organ weights of Pontoporia blainville and Platanista gangetica (Platanistidae) .
265
McHrnA, S.
Surface temperature field in the Crozet and Kerguelen whaling grounds . .
MACHIDA, S.
The voyage of the Konan Maru No. 16 to the Antarctic whaling grounds .
I TOH, S. and TsuYUKI, H.
Fatty acid component of different blubber oil of finless porpoise .

271

289
303

I TOH, S. and TsuYUKI, H.
Fatty acid component of Senegal manatee fats . . . . . . . . . .
307
NAITO, Y.
The hyoid bones of two kinds of harbour seals in the adjacent waters of Hokkaido . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313

POSSIBLE MIGRATION ROUTE OF THE GRAY WHALE
ON THE COAST OF JAPANHIDEO OMURA
Whales Research Institute, Tokyo.

ABSTRACTThe gray whale occured on the south coast of Wakayama and Kochi
prior to the turn of the century. The calving ground of this stock was possibly in the Seto Inland Sea. It migrated to and from the feeding ground in
the Okhotsk Sea, along the east coast of Japan. With the increasing industrial
development and boat and ship traffic this stock of the gray whale was driven
from the Inland Sea and probably joined to the Korean stock or even to the
California stock. A case of stranding of the blue whale is also reported.

INTRODUCTION

Occurrence of the gray whale on the coast of Japan is described by many authorsof old Japanese books and picture scrolls of whales. In Geishi (The treatise of thewhale), written by Jiemon Kandoriya of the castellany of Wakayama in 1758 andprinted in 1760, which is the earliest printed monograph of the cetacea in Japan,
is shown a drawing of Kokujira with a brief description (Fig. 1). This whale isdrawn rather slender, but it has a series of knobs instead of a dorsal fin and bears
many circular and semicircular scars on the surface of the body and tail flukes.
It has bristles spreading over the entire head. He also describes that this species
is the smallest among whales. He has a reason because the minke whale was nottaken in these days (see Table 1).
Kiyonori Otsuki (1773-1850), a famous scholar in the Tokugawa era, left an
undated manuscript on whales and whaling, entitled Geishiko (A draft of a historyof the whale). It remained unpublished till 1925, when it was printed in a seriesof various collections in Sendai. It is by far the most systematic survey of whales
and whaling that was written in the Tokugawa period (Hawley, 1958). In thisbook he notes that Kokujira has baleen plates of white in color. Other descriptions agree in general with those in Geishi, but he mentions the body form of
Kokujira is more fat than the drawing in Geishi and gives two figures of Kokujira
which resemble more to the gray whale (Fig. 2).
From the above it may safely be concluded that Kokujira is identical with thegray whale (Eschrichtius robustus) and it had occurred in the past at least on the coastof Wakayama. Further there remains some statistical data which show Kokujira
or the gray whales were taken on the coast of Kochi, southern part of Shikoku, by
the so-called net whaling prior to this century.
Modern whaling was introduced to Japan in 1897. Operation of this typeSci. Rep. Whales Res. Inst.,
No. 26, 1974, 1-14

2

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GRAY WHALE

3

CATCH OF THE GRAY WHALE IN THE DAYS OF NET WHALING
The method of taking whales by net was invented by Kakuemon Taiji in
1677 at Taiji of the castellany of Wakayama (now Wakayama-ken), and then it
spread to fishing villages on the south and west coast of Ja pan, including Shikoku
and Kyushu, where whales came in shore in winter.
This method is a combined method of driving, netting and harpooning.
When a whale was sighted by Yamami (watch on the hill), they make a signal
informing species, position and swimming direction of the whale with flags orrockets. Various kinds of boats waited and went into action in orderly fashion assoon as the commander gave the order. The basic organization of whaling fleet
was as follow.
Sekobune (for driving and killing whales). One group of about tenboats or more, 13 m long and 2.2 m wide with 8 oars, occasionally with sail.
Crew consists of 15 men.
Amibune (netting boats). One group of about 6 boats, 13 m long and3.5 m wide with 8 oars. Crew of 10 men.
Mossobune (tug boats). A group of 4 boats, nearly same as Sekobune
but with a little broader beam. Crew of 13 men.
Sekobunes drive the whale to the place called Amiba (netting place) near
the shore, producing underwater sounds with wooden hammer, where Amibunes
are waiting to set the nets. Net is set sometimes two or three-fold in order toprevent the whale's escape and to check its action by entanglement.
Various kinds of harpoons, made of iron, were used. Their weights are notheavy and usually 1.0-2.0 kg in weight. Attached with harpoon a slender woodenpole and a rope with float at its end. Harpoons are thrown high up in the air sothat they drop on the back of the whale from the air. When the whale has been
sufficiently weakened by a number of harpoons, and later by the help of heavy
swords thrown to the thorax, a sailor swims and climbs up on it and makes a holeat the blowholes with his knife in order to pass a rope through it. Then the whale
is wound by several strands of rope around the body in order to tie the whale
body between two Mossobunes before the whale was finally killed. Then it is stabbed at the heart with long swords.
In this way not only the right whale but also the balaenopterid whales weretaken by the net whaling. This type of whaling was conducted by villagers forming
groups. In these days two groups were in operation on the coast of Kochi andfour groups in Wakayama. Shibusawa (1930) gives catch statistics of Ukitsugumi, one of these groups in Kochi, during 22 years from 1875 to 1896, by speciesof whales (Table 1). As seen in this table 64 whales or 17 percent among the totalof 370 whales taken during this period were gray whales. From this table it isclear that the gray whale was hunted regularly at least until 1896 in these regions,as stated briefly by Nishiwaki and Kasuya (1970).
Further Hattori (1888) presents some data on details of operation and sightingof whales by the same whaling group in three years of 1880, 1882, and 1883 (Table
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

OMURA

42). A total of 43 gray whales were sighted in these years, in which 12 were taken,
24 escaped from taking and 7 were not pursued due to unfavorable weather.
In general the rate of the catch against total whales sighted is very low andthis is thought to be the main reason why the net whaling could survive morethan 200 years. Among whale species other than the gray in Table 1 were also
taken later by the modern whaling on the coast of Kochi and Wakayama.
CATCH OF WHALES BY UKITSU WHALING GROUP, 1875-1896.
(Cited from Shibusawa, 1939)

TABLE I.
Year

Blue

1875
1876
1877
1878
1879
1880
1881
1882
1883
1884

3
2

Fin

2

3
5
3
5

1885
1886
1887
1888
1889

4
5

1890
1891
1892
1893
1894

5
2
4

1895
1896

2
5

2

Total

55

23

9
3
2
3

Bryde's

Humpback

Right

Gray

4
5
3
4
2

2
6
19
4
9

I

I

II

2

17
33
18

8
5
2
3
2

2
10
4
7

4
3
4
4
7

5
6
13
6
4

6
3
2

11
I

7

22

6
5
3
3

23
23
12
14
12

3

19
20
26
15
15

2
2

I

4
I

2

4

3
3

4
I

8
15
8
13
10

6
6

3
2

17
19

64

370

9
3
4
5
4
81

Total

126

21

Note: Japanese name of the above whale species in these days are:Blue whale-Nagasukujira, Fin-Nosokujira, Bryde's-Iwashi or Katsuokujira,
Humpback-Zatokujira, Right-Semikujira, Gray-Kokujira.
But now the blue whale is called Shironagasukujira, and the fin Nagasukujira. Iwashikujira
means usually the sei whale, but Iwashikujira in these districts is possibly the Bryde's whale.

SUPPOSED CALVING GROUND IN THE SETO INLAND SEA

Shindo (1970) proposes the "east Kyushu migration route" of whales. He isa clinical doctor, but concurrently a historian and has much interest on whales
and whaling, especially on whales in the Seto Inland Sea. His conclusion is based
upon his study of tombs and memorials of whales and old documents concerningthese whales. He also visited villages and made interviews with people concerned.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

5

GRAY WHALE

In old days it was a general custom to errect a tomb or a memorial whena whale stranded on the beach or occasionally killed by fishermen, like human being
following after buddhism. These tombs or memorials are most abundantly remaining on the northeast coast of Kyushu and west coast of Shikoku (Fig. 10).
Among 34 tombs or memorials, he investigated all over Japan, 15 are situated inthese districts. They were errected within a period of about 100 years from 1809
to 1907. It is suggested from these facts that whales have passed frequently thisstrait and some of them were killed occasionally or stranded.
TABLE 2.

SIGHTING AND WHALING OPERATION BY UKITSU WHALING GROUP,
1880, 1882, AND 1883.
(Cited from Hattori, 1888)

Year
1880:

Blue

Catch
Escaped, A
B

Fin

Bryde's

Humpback

Right

Gray

Total

2

1

2
3

7*
5
15

4

2

6
4
8

22*
12
41

4
5
15

4

3

12

4
3
34

7

21

26
22
123

4
2

2

2
6
11

3

4
1
24

3
6
16

3
6
22
5
2
6
44

7
5
16

3
2
5

26
46
100

3

5

9

c

1882:

Not operated, DE
Total, sighted

5
14
34

Catch
Escaped, A
B

3
3
4

"

c

Not operated, DE
Total, sighted
1883:

6

Catch
Escaped, A
B

3
2
15

9

c
Not operated, DE
Total, sighted

3
5
18

3
4
4
1
4

9

9

13

12
15
23
1
16
9
76
14
14
52
5
34
58
177

* One whale difference from Table 1.
Escaped, A-breaking net, B-beneath net, C-round net.
Not operated, D-due to rough weather, E-offshore.

He (1968) also ascertained that Beppu-wan, a small bay on the northeast
coast of Kyushu, was a calving ground of whales. Fishermen applied in vain
several times for permission of whaling to the local government. These documents
are remaining, but the reason of the rejection has not been made clear. Comingof whales to this bay has lasted until about 1887. With regard to the whale species
he notes as Nagasukujira, mainly based on old papers left in Usuki, a city facing
to a small bay next to Beppu-wan, and where a memorial of a stranded whale
remammg. The story of this stranding is described later in this report.
Waters around Iwaijima, Yamaguchi-ken, was also a calving ground of whales.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

6

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GRAY WHALE

7

sibility of the balaenopterid whales, but this is hardly be thought. No baleen
whales other than the gray whale give birth to a calf in such shallow coastal waters.
It is highly possible, therefore, that the Shindo's proposal of migration route is
only applied for the gray whale. There is a possibility of other species entering
into the Seto Inland Sea through this passage, but it is not for calving. In facta skull of a balaenopterid whale was dug out from sea bottom off Onoda in 1926.
This skull was identified as a minke whale by Dr. T. Ogawa (Shindo, 1968).
Shindo (1968) reports two gray whales were taken at Kawanoe, Ehime-ken,in 1864. The official records or diary of the local government (Yakuyoki) in thesedays are still being kept at the city library. The first whale was taken on 20
February 1864 by nets and harpoons. This whale came in shore of the city several
days before the hunting was done, during which period villagers prepared catchingequipment. Shortly after the catch of the first whale the second whale came andthis whale was taken on 26 February of the same year.
Attached with the official records there remains sketches of two whales (Figs.
3 and 4). Both are without doubt the gray whale, having several knobs insteadof a dorsal fin and the head is small and not arched, unlikely to the right whale.
The first whale was marked with white color on the dark gray of the body theinfection of barnacles, but lacking the pale patches. The second whale bears palepatches all over the body, in addition to the barnacles. The body length of thefirst and the second whales were recorded as having 4 Biro (1 Biro approximately
1 Fathom) and 6 Biro respectively. This length does not mean the total length,
because it was a custom in Wakayama and Kochi to measure the length of thewhale body from the blowholes to the insertion of the tail flukes. In any case thefirst whale was smaller and younger than the second whale. The first whale isnoted as Kokujira, but the second whale as Kokujira or Aosagi. Two types of
Kokujira were noted in these days. One is Aosagi and another is Share, but thedifference between two types is not clearly described in most of the old books.
Should the first whale grouped as Share, then the difference is based on the color
pattern of the whale body caused by the infection of barnacles, or it can be said
that Share is younger than Aosagi. Both whales are thought to be females, because
teats are noted in addition to navel, genital grooves, anus and blow holes in theirright positions.
One scapula from one of these whales has been preserved. It has been kept at
Bachiman shrine in the city (Fig. 5). There is a custom in Japan to donate Ema
to a shrine in memory of big event or from some other reasons. Usually Ema isa painting on a wooden plate. In this case a scapula was used instead of wooden
plate. At the center of the scapula a big Japanese (or Chinese) character whichmeans a whale is written with powdered gold. On both sides and below thischaracter a brief descriptions of this whale is also written with paint by small
characters. This Ema has been hanged more than a hundred years on the wallof the shrine with other wooden Emas.
These two whales were the only whales taken at Kawanoe in the history, but
at Takuma, a small town east of Kawanoe, whaling had been conducted with nets
Sci. Rep. Whales Res. Inst.,
No. 26, 1971

OMURA

8

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nt
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e
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i
o
ns
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l
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h
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l
e
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s
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h
er
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t
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r
eadth oft
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l
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ns
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r
ound 1.
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l
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in whales.
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r
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s. Thes
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5Hi
r
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r
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tboth
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s
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a
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nap
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、

TABL巳 3
. MEASUREMENTS OFSじAl'UI.
AE OF'I・
HE USUll八N(
)＂
八I
へ
J
八NOi
:
・W H八LE
S
.
(
1
1
1mm
Us
u
k
i whaleMeasurements

Ka、vanuじ、、・
h
a
le

，
ー
ー
ー
ーー
目
ー
ー《ー
ー
ー
ー
ー
ー
ー
−、

Gr
e
a
t
e
stb
r
e
a
d
t
h
G
r
e
a
t
e
s
th
e
i
ght
Lengthofa
cromion,i
n
f
'
c
r
i
o
1
l
:
l
1
・
ca
dtho
facromi
on,d
i
s
t
a
l end
Lengtho
fc
o
r
a
c
o
i
d
しcn
gthofgl
c
n
o
i
df
o
s
s
a
Thic
kne
s
so
fs
upe
r
i
o
r margin
a
ta
n
t
e
r
i
o
rend
a
tmiddle
a
t po
s
t
e
r
i
o
rend
Ratioo
fb
r
e
ad
t
ha
g
a
i
n
s
th
e
i
g
h
t

Gray A~ーーーーーーー，、ーーーーーーーー、

R
i
g
h
t

しc
r
t

しc
f
t

R
i
g
h
t

Lef
t

980
615
260
121*
40
235

970
600
220
1
2
0場
55
220

990
7
4
0
290
1
3
9
1
00
2
1
0

7
5
7
495
1
93
1
3
2
58
253

7
6
1
514
1
9
0
1
4
5
62
245

29
9
42
1
.
5
9

29
8

2
7
1
5
5
2
l.
31
1

44

I
.
6
2

I.
5
3

I,
4
8

Gray B
l1
2
5
85
6
335
1
8
0
1
4
6
268

I.
3
1

*G
r
e
a
t
e
s
t
.
Gray A. Cited from N
i
s
h
i
w
a
k
i and l《~asuya, l970.
Gray B. Ci
ted from Andrews, 1
91
4
.

F
i
耳
.8
. Rightscapulaoft
h
eU川 k
iwhal
e
.

DISCUSSION

Althoughp
r
a
c
t
i
c
a
l
l
yn
o
t
h
i時 wa
sde
s
c
ri
be
dbyAndrews(
1914),Miz山（ 1
9
5
1)and
I9
7
1)
,t
h
egr
aywl
叫 eo
c
cu
r
e
dont
hec
oas
tofWakayamaandRiceandWolman(
Kochii
nt
heda
y
soft
h巴 ne
twhal
i
n
ga
sal
re
adys
t
at
e
d
. I
ti
spo
s
s
ib
let
h
a
tt
h
ey
S
c
i
.Re
/
J.Whale
sRe
s
.I
ns
t
.
,
λr
o
.2
6
,1974

2
1

A
Ol¥lUR

.
u
k
o
k
i
fSh
to
he westcoas
ng t
o
, al
g
n
vi
rcal
o
o Inland Sea f
heSet
to t
n
di
e
r
te
n
e
f
o
t
s
a
o
hc
t
ou
es
h
‑wanandont
eBeppu
h
nt
sti
a
e
tl
oundswerea
nggr
vi
Theircal
s
ara
sf
da
che
a
e
stand r
a
oe
dt
ne
r
u
nt
e
h
hem t
omeoftys
blsi
Yamaguchi. Pos
he
ot
nt
di
e
r
e
eent
hewhal
tt
ha
yt
it
l
bi
i
s
s
spo
s
e
sl
ei
r
. The
KawanoeandTakuma
e
h
st
isi
h
rt
o
nf
o
s
a
e
. Onerama
ystofWaka
a
o
tc
s
e
hew
ongt
landSeaal
n
oI
t
e
S

.
e
iwhal
uk
eUs
h
aoft
l
l
u
icb
n
a
. Tymp.9g
Fi

tofWakayamaandsaohewestc
ngont
emaini
sr
li
a
i
mor
omborme
tnot
a
h
tt
c
a
f
t
a
h
dt
e
v
ie
l
g be
n
i
hal
w
t
e
n
e
h
nt
di
e
g
nga
n whoe
rme
he
s
. Fi
oku
k
i
tofSh
stcoasae,
tofWakayamaniotp
outhmos
hesi,tak
onomist仕omo汀 Shi
gh
i
a
r
t
scomes
e
whal
.
0
.1
g
i
nF
howni
ss
tei
u
o
nr
o
i
at
dmigr
e
s
. Suppo
u
k
ko
i
tofSh
s
oa
ec
h
ot
t
o
t
eSe
h
stoft
a
o
hec
ong t
l
opment a
el
v
alde
i
r
t
dus
n
fi
ng o
si
a
e
ncr
hei
With t
e
c
n
i
es
r
e
h
n仕om t
ive
r
end
e
sb
sha
e
i
c
pe
hes
ct
i
f
f
a
r
pt
i
h
tands
a
aandbolandSe
n
I
nwhy
o
i
nat
a
eexpl
l
b
i
s
tpos
s
hemo
tbet
gh
smi
. Thi
y
ur
t
n
e
isc
h
ot
rt
o
i
r
ep
m
i
omet
s
.
n
a
p
a
J
f
o
t
s
a
o
c
e
h
nt
o
時
i
l
a
wh
nbymodernkeasbeentehallynograywha
a
c
i
t
c
a
r
p
om・
ngc
i
sofwhal
rd
co
e
chr
t
a
ec
l
b
la
gavai
n
ti
a
ig
t
s
nve
ri
氏e
,a
s
t
r
o
ep
)r
1
5
9
I
Mizue(tAyukawaandoneat
na
ke
a
et
ewer
e
r
h
,t
2
93
o1
1t
91
sfrom1
r
ea
eny
v
e
ns
si
e
pani
s
e
c
n
re
eu
toe
n
e
c
e
betwor
i
cr
s
)de
0
7
9
1
ya(
u
s
iwakiandKa
h
s
. Ni
do
i
,Hokka
muro
Ne
.
ayama
fWak
f
o
n
yi
lewasprobabl
a
ywh
ra
heg
ft
ko
c
o
t
es
s
e
n
a
heJap
oundoft
r
gg
n
i
ed
e
Thef
.
)
1
7
9
1
,
n
a
m
l
o
W
d
n
a
e
c
i
R
(
k
c
o
t
s
n
a
e
r
Ko
e
h
t
f
o
e
s
a
c
e
h
t
n
i
s
a
a
e
S
k
s
heOkhot
t
t
s
a
o
c
t
s
a
e
e
h
t
n
o
y
l
b
i
s
s
o
p
s
a
w
d
n
u
o
r
g
ng
edi
e
ef
h
iomt
oandf
et
t
u
o
ionr
at
r
Themig
m
o
r
f
en
iv
r
erd
t
f
). A
0
7
9
1
uya(
s
iandKa
ak
hiw
s
dbyNi
e
t
a
t
adys
re
sal
pan,a
ofJa
an
e
heKor
ot
dt
ine
o
sj
yha
l
tprobabandSeai
nl
oI
heSet
nt
nggroundi
vi
al
hec
t
gSea
n
i
r
h巴 Be
nt
ki
c
o
t
ias
n
or
f
l
e Cai
h
ot
ngt
i
n
oi
yofj
t
i
il
b
si
s
rapo
he
. Furt
k
oc
t
s
s
s
e
malandl
obes
ughtt
o
h
st
ki
c
o
t
iss
h
eoft
z
i
nals
igi
r
d. Theo
ie
n
tbede
o
cann
.
t
s
e
g
r
a
hel
tt
anda
us
o
h
hanat
t
heSeaofnt
rii,oh
stofYamaguc
a
o
hc
t
r
o
hen
andontlsmali,asAtOmijima
,
a
imur
K
(
g
n
i
l
a
wh
t
e
n
e
h
t
f
o
s
y
a
d
e
h
t
n
i
n
e
k
a
ot
ls
sa
ewa
aywhal
hegr
,t
n
a
p
Ja
.
s
e
i
c
e
p
s
y
b
,
0
5
8
o1
802t
om I
r
iodf
r
gape
n
i
dsdur
or
c
e
hr
c
nscat
mai
e
er
r
. The
)
6
5
9
1
.
s
e
l
a
nwh
e
丘e
o日
d 仕om onet
e
uat
t
uc
l
,wasf
s
e
i
c
pe
eofals
v
i
us
l
c
n
ch,i
at
lc
a
u
Ann
,
.
t
s
n
s.i
.WhalesRe
.Rψ
i
c
S
974
匂. 26~ 1
1
1/

GRAY WHALE

13

The total catch during this period was consisted of the fin (38 %), the humpback(34%), the right (19%), and the gray whale (9%). The catch of the gray whale
has decreased since 1812. A question remains whether these gray whales belong
to the Korean stock or they are stragglers from the Japanese stock.

!J

0

Fig. 10. Possible migration route of the gray whale on the coast of Japan.
Hatched area: Supposed calving ground.
Black dots: Positions where whale tombs or memorials located.
Names of the places refered to in the text are following.
1. Taiji
2. Ukitsu
3. Usuki
4. Beppu
5. Omijima
6. Onoda
7. Iwaijima
8. Kawanoe
9. Takuma

ACKNOWLEDGEMENTS

Sincere thanks are due to Dr. N. Shindo who helped me greatly in this study. He
joined my trip to Usuki and Kawanoe and made all possible arrangements forme. My thanks are also due to Mr. S. G. Brown of the Institute of Oceanographic
Sciences, England. He gave me the old Japanese book, he found at an old bookstore in London, and from which Table 2 in the text was refered.
REFERENCES
ANDREWS, R. C., 1914. Monographs of the Pacific cetacea. I. The California gray whale (Rhachianectes
glaucus Cope). Mem. Amer. Mus. Nat. Hist. (New Ser.), I: 227-287.
ANDREws, R. C., 1916. Monographs of the Pacific cetacea. II. The sei whale (Balaenoptera borealis Lesson). Mem. Amer. Mus. Nat. Hist. (New Ser.). II: 291-388.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

14

OMURA

HATTORI, T., 1888. Nikon Hogei Iko (Monograph of the whaling in .Japan). Part II. Tokyo. 210 p.
(In Japanese).
HAWLEY, F., 1958. Whales & Whaling in Japan. Vol. 1, Part 1. MiscellaneaJaponica, II. Kyoto. 354 p.
HIGASHI, K., 1944. Z,oku Manyo Doubutsu-ko (Further studies of animals in the Manyo period). Kyoto.
(In Japanese).
KANDORIYA, J., 1760. Geishi (The treatise of the whale). Kyoto. (In Japanese).
KIMURA, S., 1956. Kujira no Kakocho (Buddhistic records of the dead whale). Geiken-tsushin. 63: 144150. (In Japanese).
M1zuE, K., 1951. Gray whales in the east sea of Korea. Sci. Rep. Whales Res. Inst., 5: 71-79.
NISHIWAKI, M. and T. KAsUYA, 1970. Recent record ofgray whale in the adjacent waters of Japan and aconsideration on its migration. Sci. Rep. Whales Res. Inst., 22: 29-37.
0TSUKI, K., 1925. Geishiko (A draft of a history of the whale). Sendai. 169 p. (In Japanese).
RICE, W. D. and A. A. WOLMAN, 1971. The life history and ecology of the gray whale (Eschrichtius robustus).
Amer. Soc. Mamm. Special Publication No. 3. 142 p.
SHIBUSAWA, K., 1939. Tosa Muroto Ukitsugumi Hogei Shiryo (Records of the Ukitsu whaling group, Tosa
Muroto). Attic Museum Iho 36. Tokyo. 371 p. (In Japanese).
SHINDO, N., 1968. Seto Naikai no Kujira no Kenkyu (Studies of whales in the Seto Inland Sea). Kobe. 135 p.
(In Japanese).
SHINDO, N., 1970. Kujira-zuka no Kenkyu (Studies on whale tombs and memorials). Kobe. 161 p. (InJapanese).
ToMILIN, A. G., 1957. Cetacea. Mammals of the U.S.S.R. and adjacent countries. IX. English translationin 1967. 717p.
YAKUYOKI, 1864. An official records of the local government of Kowanoe (hand written).

POSTSCRIPT
After completion of the manuscript I read a paper on the Korean stock of the graywhale by Bowen (1974). The author states that the 1968 specimen (Nishiwaki andKasuya, 1970) resembled members of the California stock in morphological features,without mentioning the character in question. As seen -in Table 3 the ratios of breadthagainst height of scapulae in three specimens of the gray whale are: the Kawanoe
whale 1.34, Gray A (Nishiwaki and Kasuya, 1970) 1.48-1.53, and Gray B (Andrews,
1914, Korean stock) 1.31. Thus in this respect the Kawanoe whale resembles more to
the member of the Korean stock than the whale reported from the coast of Japan.
But the latter whale is a young female and this is thought to be a difference due tothe growth.
As regards the distribution of the Korean stock Dr. K. Uchida (1964) describes agray whale sighted by him towards the end of May 1930 on the west coast of Korea,
in the Yellow Sea, at a position close to 38°N.
REFERENCES
BowEN, S. L., 1974. Probable extinction of the Korean stock of the gray whale (Eschrichtius robustus).
J. Mamm. 55 (I): 208-209.
UcamA, K., 1964. Chigyo wo motomete (My study on fish fry). lwanami-shinsho. Tokyo. 207 p.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

A TAXONOMIC STUDY OF THE MINKE WHALE IN THE
ANTARCTIC BY MEANS OF HYOID BONE
YUKO SATAKE AND HIDEO OMURA
Whales Research Institute, Tokyo

ABSTRACT

Hyoid bones of the minke whale in the Antarctic were studied fromthe standpoint of taxonomy, comparing those in the North Pacific. A distinction was noted in the length and thickness of the stylohyals. Greatest
height of the ankylosed bone of basihyal and thyrohyals as well as the heightat middle of the right and left wings are greater in the specimens from theAntarctic than in those from the North Pacific. But there is a possibility
that this is a difference according to age of the whale. Hence samples fromthe Antarctic are biased towards older ages and those from the North Pacifictowards younger ages, no conclusion was reached in this respect.

INTRODUCTION

The minke whale in the Antarctic, though most closely related to Balaenoptera
acutorostrata, differs from the latter in having flippers of a uniform pale gray colour
instead of showing the characteristic white band of the true minke whale. Furthermore the baleen of B. acutorostrata is of a uniform yellowish-white colour whereas
the baleen of the minke whale in the Antarctic is white at the front of the series
and gray and white at the back (Williamson, 1959, 1961; Utrecht and Spoel,
1962; Kasuya and Ichihara, 1965; Ohsumi et al., 1970).
Williamson (1961) describes that it is uncertain whether they (B. bonaerensis)
represent a true species, or a subspecies of B. acutorostrata, but Utrecht and Spoel(1962) and Ohsumi et al. (1970) report that B. bonaerensis is a synonym of B. acutorostrata, mainly based on studies on the external characteristics.
In this report the hyoid bones of the minke whales in the Antarctic are compared with those of the North Pacific (B. acutorostrata) from the taxonomic standpoint, following after the method adopted by Omura (1964).
MATERIAL

In the 1971-72 whaling season Dr. Seiji Ohsumi went to the Antarctic on board
Jinyo Maru, a minke whaling expedition. He collected hyoid bones from 25
minke whales and made them at our disposal. These whales were taken in the
Antarctic area IV and the sex and body length of each whale are shown in Appendix Table.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974, 15-24

SATAKE AND OMURA

16

MEASUREMENTS

After extraction of oil and cleaning measurements of various parts were made.
These are compared with those from the North Pacific, cited from Omura (1964).
There is rather a wide difference in body length of samples between both hemispheres.
Samples from the Antarctic range from 710 cm to 980 cm in length, with an averageof 850 cm, whereas those from the North Pacific are from 500 cm to 768 cm andin average 624 cm. Thus samples from the Antarctic are biased towards older
ages and those from the North Pacific towards younger ages, which should be bornin mind in direct comparison.

I !pi
Fig. 1.

Showing positions of the measurements.

The following measurements were made on each hyoid bone collected (seeFig. I).
A. Ankylosed bone of basihyal and thyrohyals.
a. Overall length. Curved length measured along the outer surface andpassing centers of basihyal and thyrohyals.
b. Straight length. Straight length between tips of right and left wings.
c. Greatest height. Greatest height between tips of the anterior and posterior
projections of the basihyal.
d. Height at center. Height measured at the center of the bone.
e. Forward notch, depth. Depth of the notch between right and left forward
projections of the basihyal.
f. Height at middle of wing, right. Height measured at middle between thecenter of the basihyal and tip of right wing.
g. Height at middle of wing, left. Height measured at middle between thecenter of the basihyal and tip of left wing.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

MINKE WHALE

17

Thickness at middle of wing, right. Thickness of right thyrohyal on the lineof measurement f.
i. Thickness at middle of wing, left. Thickness of left thyrohyal on the lineof measurement g.
j. Height at distal end, right. Height of right thyrohyal at its distal end.
k. Height at distal end, left. Height of left thyrohyal at its distal end.
Stylohyal.
1. Total length, right. Straight length between tips of right stylohyal.
m. Height at middle, right. Height at middle of right stylohyal.
n. Thickness at middle, right. Thickness of right stylohyal on the line ofmeasurement m.

h.

B.

Measurements

no.

h

,.

g

e

'

,

E\:J

d

c
0

10

20

30

40

% against overall length
Fig. 2. Measurements of various parts of the ankylosed bone of basihyal andthyrohyals of the minke whale, expressed as percentages against its overall length.
For measurements no. see text. Horizontal line indicates ranges of measurements, vertical midline the arithmetic mean, square the 95% confident limitsof the mean. Square with hatched lines denotes samples from the minke whalefrom the North Pacific and white square those from the Antarctic.

o.

Degree of curvature, right. Greastest distance between the straight line
passing the most prominent parts of right stylohyal and its forward surface.
p. Total length, left. Straight length between tips of left stylohyal.
q. Height at middle, left. Height at middle of left stylohyal.
r. Thickness at middle, left. Thickness of left stylohyal on the line of measurement q.
s. Degree of curvature, left. Greatest distance between the straight line passing
the most prominent parts of left stylohyal and its forward surface.
Results of these measurements are shown in Appendix Table, together withthe serial number of the whale, sex, and body length.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

18

SATAKE AND OMURA

These measurements were then calculated of their percentages against overall
length in the case of the ankylosed bones of the basihyal and thyrohyals. For the
stylohyals also percentages against overall length were calculated for total length,
but in other measurements percentages against the length of stylohyals were calculated. Further for each measurement the arithmetic mean, its standard deviation
and 95 % confident limits of the mean were calculated.
DISCUSSION

The results of the calculations are shown in Figs. 2-4, comparing with those fromthe North Pacific. As seen in these figures differences are noted between the minke
whales from the different oceans in the following measurements:
Measurements no.
p

45

50

55

60

65

70

% against overall length

Fig. 3. Measurements of stylohyal of the minke whale, expressed as percentages
against the overall length of the ankylosed bone of basihyal and thyrohyals. For
explanation see Fig. 2.
Measurementsno ~------------------,
s
0

_r

·~

n

·Eb

q

·•·
'

m
5

10

15

Eb

20

25

% against length of stylohyal

Fig. 4. Measurements of various parts of the stylohyal of the minke whale, expressed as percentages against its total length. For explanation see Fig. 2.

A.

Ankylosed bone of basihyal and thyrohyals (Fig. 2).
c. Greatest height.
f. Height at middle of wing, right.
g. Height at middle of wing, left.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

MINKE WHALE

19

B.

Stylohyal (Fig. 3, Fig. 4).
I. Total length, right.
p. Total length, left.
n. Thickness at middle, right.
r. Thickness at middle, left.
In the other measurements 95 % confident limits are overlapping each otherand they cannot be said as distinct. In conclusion above the minke whales in the
Antarctic have more higher combined bone and larger and thicker stylohyals,
hence more massive hyoid bones than those in the North Pacific.

~ 20

E
u

"'c
0

-"'
-0

"'

<ll
0

>.

-"'
c

"'

£"'

0

...,

..c:

·~10
..c:

0

500

600
700 800
Body length (cm)

900 1000

Fig. 5. Relative growth of the greatest height of the ankylosed bone of basihyal
and thyrohyals and body length of the minke whale. Circles indicate minke whalesin the North Pacific and black dots those from the Antarctic.

As already stated average body lengths of the sample whales are widely different between the two oceans. More larger or older whales were sampled fromthe Antarctic than from the North Pacific. The reason for such discrepancy inbody length should be sought in the segregation of the minke whales according to
the size or age. Samples from the North Pacific were collected at Ayukawa on
the east coast of Japan where sexually mature animals are far less than in thewaters of higher latitudes (Omura and Sakiura, 1956). Also in the Antarctic
similar segregation by age groups was noted in males (Ohsumi et al., 1970).
Consequently there is a possibility that the above noted differences in hyoid bones
are in fact due to differences according to age.
In Fig. 5 the greatest heights of the ankylosed bone of basihyal and thyrohyals
have been plotted logarithmically against body length of whales. In the figure
different symbols were used for the minke whales from both hemispheres. This
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

SATAKE AND OMURA

20

figure shows that there are significantly different gradients for regressions of log
height of the bone on log length between whales from the different oceans, and thelines of regression intersect at the body length of 709 cm.
In Figs. 6 and 7 relative growth of the height at middle of wing of the combined bones and body length are shown. In these cases two regression lines in

•

11
10

/

9

'

E
(.)

·~

8

bJJ

c

'j;

-0 7

"'

'O

~ 6

4

/'
500

600

700 800 900 1000
Body length (cm)Fig. 6. Relative growth of height at middle of right wing of the ankylosed bone
and body length of the minke whale. For symboles see Fig. 5.

11
10

'E

-'.:. 9
bJJ

c

'j; 8

.....0

"' 7

'O

-0

.E
~

"' 6

~

.s::

bJJ

·a;

:r:

5

4

500

600
700 800 900 1000
Body length (cm)Fig. 7. Relative growth of height at middle ofleft wing of the ankylosed bone andbody length of the minke whale. For symbols see Fig. 5.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

MINKE WHALE

21each figure intersect at a body length of 761 cm (right side, Fig. 6) and 727 cm(left side, Fig. 7) respectively. Ohsumi et al. describe that the sexual maturity ofthe minke whale in the Antarctic is attained at a body length of 710 cm in maleand 790 cm in female. According to Omura and Sakiura (1956) in the minkes
on the coast of Japan these lengths at sexual maturity of male and female are 660690 cm and 720 cm respectively.
One possibility, therefore, is that the antero-posterior growth of the combinedbone becomes greater proportionally after the attainment of the sexual maturity.
But this cannot be concluded at present due to lack of sufficient materials. Morematerials, i.e. in the case of the minke whale in the Antarctic samples from immature animals and in that in the North Pacific more samples from mature animals,
are needed.

35
E

~ 30

/

/

15
500

600
700 800 900 1 OOO
Body length (cm)Fig. 8. Relative growth in length of right stylohyal and body length of the minke
whale. For symbols see Fig. 5.

In Figs. 8 and 9 relative growth of the stylohyal and body length are shown.
As clearly seen in these figures two lines of regression are nearly parallel and wemay safely conclude that the minke whale in the Antarctic has more longer stylohyals than the minke in the North Pacific, though there is rather a wide individual
variation.
We are not in a position, however, to conclude at present whether the minke
whale in the Antarctic, Balaenoptera bonaerensis, represent a true species, or a subspecies of B. acutorostrata, as stated by Williamson (1961). Further studies especiallyon the skull and other postcranial bones are needed in order to reach a more de.finite conclusion.
Omura (1964) made a key to the genera and species of mystacoceti by meansof hyoid bone. In the key he separates B. acutorostrata from B. borealis and B. edeni
by percentage of the greatest height of the combined bone against its overall length.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

SATAKE AND OMURA

22

The critical proportion is 29 percent and those less than this value was assigned toB. acutorostrata and others to B. borealis and B. edeni. B. bonaerensis has more greater
value than this and the key should be or should not be revised in this respect,depending upon the final conclusion.

.

•

/

/

0

15
500

600
700 800 900 1000
Body length (cm)Fig. 9. Relative growth in length of left stylohyal and body length of the minke
whale. For symbols see Fig. 5.

ACKNOWLEDGEMENTS
Our sincere thanks are due to Dr. Seiji Ohsumi who collected hyoid bones of theminke whale in the Antarctic for the present study. The crew of Jinyo Maru andthe staff of Taiyo Gyogyo K.K. are deeply acknowledged for their cooperation insampling and also in transportation of the material.
REFERENCES
KASUYA, T. and T. IcHIHARA, 1965. Some informations on minke whales from the Antarctic. Sci. Rep.
Whales Res. Inst., 19: 37-43.
0HSUMI, S., Y. MASAKI and A. KAWAMURA, 1970. Stock of the Antarctic minke whale. Sci. Rep. Whales Res.
Inst., 22: 75-125.
OMURA, H., 1964. A systematic study of the hyoid bones in the baleen whales. Sci. Rep. Whales Res. Inst.,

18: 149-170.
OMURA, H. and H. SAKIURA, 1956. Studies on the little piked whale from the coast of Japan. Sci. Rep.
Whales Res. Inst., 11: 1-33.
UTRECHT, W. L. VAN, and S. VAN DER SPOEL, 1962. Observations on a minke whale (Mammalia, Cetacea)
from the Antarctic. Zeit. Siiugetier., 27(4): 217-221.
WILLIAMSON, G. R., 1959. Three unusual rorqual whales from the Antarctic. Proc. Zoo!. Soc. (London).

133: 134-144.
WILLIAMSON, G. R., 1961.

Two kinds of minke whale in the Antarctic. Norsk Hvalfangst-Tid., 50(4): 133-

141.
Sci. Rep. Whale Res. Inst.,
No. 26, 1974

MINKE WHALE

APPENDIX TABLE.

23

MEASUREMENT OF HYOID BONE OF THE MINKE WHALE
IN THE ANTARCTIC.
Measurement in mm*. I Body
Senalength Sex
no.
(m)
a

b

c

d

e

f

g

h

j

k

m

n

o

p

q

r

71]2721 7. I F 364
71J2692 7. 5 F 446
71]0188 7.8 F 459
71J2849 7.9 M 489
71J2685 7. 9 F 414

334
404
425
452
399

127
125
127
126
132

98
86
88
87
105

21 62
38 66
37 65
40 67
24 62

61
64
65
65
62

30
32
30
32
29

29 34
30 38
30 43
31 35
30 36

34
38
45
35
33

220 46 23
266 55 21288 54 22274 62 20271 47 23

18
25
35
17
30

219 45271 56292 55276 63
275 48

22
20
22
21
23

19
26
35
18
28

71J2727 8.1
71]2323 8.371]2324 8.471]0157 8.4
71J0312 8.4

F 478
F 450
M 503
F 466
F 433

451
420
435
438
405

161
166
131
171
171

106 52 76 77
138 23 87 84
107 19 76 77
96 70 79 77
129 35 79 77

49
41
32
37
31

306 62285 63289 59275 61
318 64

32 25
34 33
23 33
38 50
30 52

311 64286 65289 62
280 62324 60

31
33
24
37
33

25
30
31
52
55

71]0459 8.4
71J0174 8.5
71J2415 8.5
71J2793 8.5
71J2322 8.6

F 477 425
M 522 475
F 502 462
M 514 491
F 427 397

143
164
147
155
153

90 43 69 71 34
Ill 49 65 66 30
94 52 65 65 38
113 40 66 66 31
123 31 73 73 38

34 32 32 285 55 29 27 287 57 30 24
29 30 29 294 61 24 37 298 66 26 36
39 39 41 267 62 24 17 272 63 24 18
32 35 39 294 61 30 41 302 60 30 45
37 37 36 257 59 34 22 256 60 36 21

71]0165 8.671]2373 8.671]2667 8.671]2197 8. 7
71J2228 8.7

F 506 460
M 471 438
M 507 453
F 505 460
F 480 435

148
124
150
151
159

97 46
96 27
99 46
105 43
121 38

73
71
76
72
71

31
24
47
34
31

32 29
26 36
46 41
34 44
31 29

30 294 67 23 25
37 286 65 25 23
41 315 69 35 23
41 300 67 29 33
30 290 61 20 18

299 70308 65316 70307 68292 64

23
25
36
30
21

26
26
25
34
18

71]0145 9.0
71]0154 9.2
71J0276 9.4
71J0458 9. 7
71J2883 9.8

F 503 454
F 511 479
F 485 433
F 556 489
F 543 493

145
162
176
184
207

106 35 70 71
104 49 75 76
147 22 91 94
130 44 89 88
157 48 111 107

38
32
39
46
40

41
32
40
46
40

38
41
44
53
40

296
312
314
346
336

27
22
27
28
28

23
20
24
47
39

* For measurement number see text.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

72
70
76
71
73

38 36
42 41
32 31
42 41
35 36

48
41
32
34
33

37
39
47
51
38

297
306
318
335
339

62
63
84
69
63

27
24
29
27
27

24
19
23
43
33

62
62
82
67
64

24

SATAKE AND OMURAEXPLANATION OF PLATESAll the photographs were taken from the ventral side.
PLATE IThe ankylosed bone of basihyal and thyrohyals of the minke whale from the Antarctic.
Fig. I. specimen 71]2721
Fig. 8. specimen 7 IJ2324
Fig. 2. specimen 71]2692
Fig. 9. specimen 71]0157
Fig. 3. specimen 71]0188
Fig. 10. specimen 71]0312
Fig. 11. specimen 71]0459
Fig. 4. specimen 7 IJ2849
Fig. 5. specimen 71]2685
Fig. 12. specimen 71]0174
Fig. 6. specimen 71J2727
Fig. 13. specimen 71]2415
Fig. 14. specimen 7 IJ2793
Fig. 7. specimen 7 IJ2323
PLATE II
The ankylosed bone of basihyal and thyrohyals of the minke whale from the Antarctic.
Fig. 21. specimen 71J0145
Fig. 15. specimen 71]2322
Fig. 22. specimen 7 IJ0154
Fig. 16. specimen 71]0165
Fig. 17. specimen 71]2373
Fig. 23. specimen 71]0276
Fig. 18. specimen 71]2667
Fig. 24. specimen 71J0458
Fig. 19. specimen 71]2197
Fig. 25. specimen 71]2883
Fig. 20. specimen 71]2228
PLATE III
Stylohyals of the minke whale from the Antarctic.
For explanation see PLATE I.
PLATE IV
Stylohyals of the minke whale from the Antarctic.
For explanation see PLATE II.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

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FOOD AND FEEDING ECOLOGY IN THE
SOUTHERN SEI WHALE*
AKITO KAWAMURA
Whales Research Institute, Tokyo

ABSTRACTThe sei whale is an important stock of whales which has currently been
hunted in the Antarctic region taking over the decreased catch quotas of fin
whale. However, its biology and ecology as a whole are poorly studied being
compared with those in another whale species due to relatively recent development in commercial whaling.
This study aims to add some habitual and ecological knowledge on thefood and feeding in southern sei whale being based on the materials obtainedby the Japanese floating factories and by the research ships through 1967/68
to 1971/72 seasons.
The sei whaling ground is formed throughout the circumpolar seas, but
it is centered approximately between 40°S and 50°S under the surface sea
temperature of about 8.0-18.0°C, particularly in a zone along the Subtropical Convergence of under 10°C or more in temperature where more than
70% of whales is caught.
A total of 23 species of food organisms was found, of which the following species being arranged with the order of importance consisted main foodstuff of sei whale: Calanus tonsus, Euphausia vallentini, Parathemisto gaudichaudii,
Calanus simillimus, Euphausia superba, Drepanopus pectinatus, Clausocalanus laticeps,
and Euphausia lucens; and, the following 7 species were newly known as sei
whale food in the Antarctic region: C. tonsus, Cl. laticeps, Thysanopoda actifrons,
E. diomedeae, E. lucens, Penaeus sp. and Scomberesox saurus though Penaeus sp. is
still doubtful in identification. However, C. tonsus of copepodite V stage was

fed by more than 70% of600 animals examined, and its nutritional importancealong with its influence on the formation of whaling ground would be distinct.
The food organism changes successionally with the shift in whaling groundfrom northern extreme along 40°S toward south by following the order ofcopepods, small sized euphausiids or amphipods, then again euphausiids.
The baleen plates furnished in a row as feeding structure of filtering
apparatus are formed by the various sized baleen plates which are furnishedwith 0.93-1.4 plates/cm, and the figures do not vary with the body lengthand the sex. The averaged number of bristles on the baleen plate was 45.5
bristles/cm. An example of a total area for the filtering apparatus was 3.59 m 2
in the animal of 14.4 m in body length, and relative ability in filtering thewater by a row of baleen plates was considered to be placed somewhere between that in balaenopterid whales other than sei whale and balaenid whales.

* This work was submitted in partial fulfillment of the requirements for the degree of Doctor of Fisheries
Science at the Hokkaido University in 1974.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974, 25-144

KAWAMURA

26

Comparison of the filtering ability in sei whale with others revealed the sei
whale to be poor in those ability being 1/5 of the fin whale, and 1/8 of thebolting silk cloth GG54 (0.33 mm mesh aperture, 46% in porosity).
The analysis on the fulness of stomach contents by hours revealed that
20-30% of their amounts reduced within 5-6 hours, from which it is supposed that the sei whale feeds fully once in a day. The amount of stomach
contents usually found in fully repleted sei whale was 150-200 kg but wasless than 100 kg when they were consisted by Calanus tonsus. The daily rationin sei whale was calculated as 4.43% of body weight by using the formulation; Heart weight X 100/body weight· I/daily ration"=;:0.11 (const.), thenaverage sized sei whale requires about 900 kg of food daily. The figures bothamout of stomach contents and daily ration in sei whale lead to a consideration that the whale would hardly be filled its nutritional requirements by C.
tonsus food alone, that is, the whales seem to be kept under starvation to someextent in the natural environment.
A possible population density in C. tonsus patches being based on both theamount in the stomach and the filtering ability was calculated as approximately 103 -10 4 inds./m 3 , and it was proved in .this calculation that feeding byskimming type would be much advantageous for sei whale than by swallowing
or gulping type feeding. After examining on the net samples of C. tonsus
patches being composed of similar population structure, it was proved thatthe population density under patchiness was 2.4 x 104 inds./m3, which agreed
quite well with the figures assessed by the theoretical calculation.
The distribution of whales in connection with the environmental conditions would be understood by a high concentration of phosphate alongwith the presence of rather deeper layered thermocline where larger standing
crops of organisms were found. However, since the swarming of zooplankton
into patchiness would be essentially important character as the food of whales,
none of organisms which widely occur with larger biomass such as tunicatesand chaetognaths induce the concentration of whales. The geographicaldistribution of C. tonsus may essentially be influenced by the physico-chemical
conditions of the sea. They may, however, be of no use for considering on
the causation of swarming phenomenon of, say, the patchiness of prey organisms since aggregating habits in animal including zooplankton seem to
be strongly controlled or released by some less known biological factors suchas the density effect under crowding.
CONTENTS

l.
2.
3.
4.

5.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Material and method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Biological observations of whales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recent catch and whaling ground of sei whale . . . . . . . . . . . . . . . .
4-1. An outline of the whaling ground . . . . . . . . . . . . . . . . . . . . . . .
4-2. Catch distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-3. Surface sea temperature in sei whaling ground . . . . . . . . . . . .
Food of sei whale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5-1. Kind of food organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

28
32
34
36
36
37
40
45
46

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

6.

7.

8.

9.

10.

11.

12.

5-2. Composition of the stomach contents ................... . 48
5-3. Geographical distribution of food organisms ............. . 53
5-4. Latitudinal change in the distribution of food organisms ... . 56
5-5. Distribution of food organisms by the whaling area ....... . 58
Distribution of whales, and its relation to physical, chemical andbiological environment factors ............................... . 61
6-1. Distribution of whales and the environmental factors in the
Pacific and Antarctic Ocean ........................... . 61
6-2. Whaling ground of sei whale and the distribution of zooplankton ........................................... . 64
Body size of Calanus tonsus ................................... . 72
7-1. Composition of body size in C. tonsus population ......... . 72
7-2. Discussion .......................................... . 74
7-3. Patchiness of C. tonsus and the density effects ............. . 76
Feeding apparatus of sei whale ............................... . 77
8-1. Oral cavity ......................................... . 78
8-2. Baleen plates ....................................... . 79
8-3. Bristles on baleen plates ............................... . 81
8-4. Area of filtering apparatus ............................ . 82
Filtering ability in the row of baleen plates ................... . 84
9-1. Porosity in the meshes of filtering apparatus of sei whale ... . 84
9-2. Relative filtering ability in a row of baleen plates ......... . 85
Amount of the stomach contents and the population density of foodorganisms ............................................... . 87
10-1. Influence of chasing time to stomach contents ........... . 88
10-2. Amount of stomach contents ......................... . 89
10-3. Daily variation in feeding activity ..................... . 91
10-4. Possible cause induces a decrease in the fulness of stomach
contents ........................................... . 94
10-5. Daily ration in sei whale ............................. . 96
10-6. Estimation of population density in the food organisms ... . 101
Swarms of Calanus tonsus Brady ............................... . 105
11-1. Zooplankton swarms as whales food ................... . 106
11-2. Material and method ............................... . 107
11-3. General hydrology in the investigated region ........... . 110
11-4. Shape, color, and size of C. tonsus swarms ............... . 110
11-5. Distribution of C. tonsus swarms ....................... . 112
11-6. Frequency distribution by hour ....................... . 115
11-7. Population density in the C. tonsus patches ............. . 116
118
11-8. Zooplankton abundance in the back ground waters
11-9. Some biological characters in the C. tonsus patches ....... . 119
11-10. Possible cause of swarming in zooplankton ............. . 121
General discussion and conclusion ........................... . 125
Summary ............................................... . 129
Acknowledgments ......................................... . 133
References ............................................... . 134
Appendix ............................................... . 143
Plates ................................................... . 144

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

27

28

KAWAMURA

1.

INTRODUCTION

The way to the modern pelagic whaling from the early North Atlantic whaling inSpitzbergen through those sperm whale whaling by the American ships in the southseas was a story of exploring the unknown seas by mankind who pursued for the
undeveloped stock of whales which move in search of rich food concentrations in
the vast ocean. In the ecological views it was a activity of mankind to increase
the knowledge by the aid of accumulated experiences on the breeding and feeding
behavior of whales, since those two are the essentially important factors in controlling the whale movements in the sea.
The famous whaling grounds which are formed during warmer season havebeen found where rich accumulation of food organisms is expected, or whale
movements and the formation of whaling ground were recognized generally as
a function of the distribution of food organisms in the sea. For instance, Scoresby(1820) in his cruise to the East Greenland waters early noticed that a "small crustaceans " was fed by the bowhead whale Balaena mysticetus, which indicates thewhaleman at that time had been interested in whales food in relation to the whale
movements although his observation was not biologically tangible. According
to Collett (1886), however, the food of sei whale caught in Varangerfjord, Finmarkin July 1885 was consisted of Calanus finmarchicus and of also Euphausia inermis, andthey might be an important diet of sei whale in some seasons while fishes were lessavailable as their food. Collett (1912) suggested an importance of the oceanic
front as whaling ground where rich planktonic organisms occur due to confront
the warm Atlantic and cold Arctic waters, and later Lillie (1915) called the sei
and blue whales in the North Atlantic would be a "plankton feeder". In the
North Atlantic the distribution pattern of herring and euphausiids, or and copepods
during fishing season closely relates to the movements of baleen whales which
feed on those organisms. Concerning with feeding habits of baleen whales, it has
been also known that they follow to two different ways to collect the food organisms,
say, "skimming" and "swallowing" or "gulping" by boltering the body whilefeeding, and they are so shy and agile when there are no foodstuff in the stomach(lngebrigtsen, 1929).
Returning from the 2nd exploring voyage into the southern seas during 17721775, Captain]. Cook brought an information that the bulk of pinnipeds and whales
were accumulated in the Ross Sea region, and since then the Antarctic region
became an indispensable whaling ground after passing several tenth years as heavy
sealing places (Fraser, 1964). When C. Darwin made a famous voyage on boad of
the H.M.S. "Beagle", he sighted of many whales in the vicinity of Tierra del Fuego,South America where the surface of the sea was discolored into red-brown by the hugeswarming of small crustaceans (Darwin, 1906). At this sight he (Darwin, 1906)
thought that those swarming crustaceans must be the food of whales. According
to Hinton (1925), Hamilton in his investigations at South Georgia had took notethe importance of planktonic " swarming life " as Risting early had pointed out
the matter in relation to whales food. It is important to take into account that
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

29

the movement of whales had been considered as a function of food available there,
especially as its distinct distributional pattern of so-called the plankton patchiness(Hardy and Gunther, 1935), and these recognitions of whales and their movements in connection with food organisms must be highly valuated ecologically apartfrom a qualitative knowledge on the whales food by species. In the investigation
on southern whale stocks, much are owe to the works done by the Discovery
Committee, especially to its bulk ofresults having been accumulated, and also to theestablishments in methodology for biological examination of whale carcasses (e.g.
Kemp et al, 1929; Hardy, 1967). In the matter of whales food, the records ofthe stomach contents by defining the size of food organisms present an importantmaterials for considering geographical distribution of food organisms and theirdistribution pattern (Mackintosh and Wheeler, 1929; Marr, 1962; Mackintosh,1973). By examining the stomach contents of blue and fin whales in the South
Georgia whaling ground and in Nathal, South Africa, Mackintosh and Wheeler(1929) found only E. superba as a pricipal foodstuff, and has long been believed that
only above species was the food organisms of southern baleen whales (Harmer, 1928,1931). However, E. superba population which is actually fed by the whales is consisted of both matured adults and small or medium sized immature and adolescent individuals, and they occurred different ways by the places, seasons and by the kindof whale species which prey upon them. By noticing these difference, Norwegianwhaleman called them from their experiences as " blue whale krill " for small
sized E. superba and " fin whale krill " for larger sized one. This would be analogous in the case of Meganyctiphanes norvegica and Thysanoessa inermis which occur in
the Norwegian waters, and they have called them as "star-krill" and "smaakrill" respectively. These also suggest that the seasonal movements of whales andtheir spring run close to their own shore have been considered in connection with thecharacteristic occurrence of food organisms. Hamilton who conducted biologicalobservations on whale carcasses in 1913-14 season at South Georgia found" shrimp"
in the stomachs of fin and humpback whales (Hinton, 1925). It is note worthy
that Hamilton clearly separated them from usual krill, and this leads to a supposition that his " shrimp " might had not been larger E. superba but Galatheid shrimp
such as Munida gregaria (Matthews, 1932; Dawbin, 1955; Tabeta and Kanamaru,1970). In 1913-14 season at South Georgia a total of 90 sei whale was caught(Hinton, 1925). There were, however, no notable biological observations on thisspecies except a mere note as " plankton eating species " since sei whale had lesscommercial value at that time. The food habits of sei whale have not known well
until recent years by reason of little catches as above mentioned (Mackintosh,1947). During the whaling seasons from 1960/61 to 1964/65 a total of 1223 sei
whale was caught at South Georgia whaling ground, and food organisms such as
Parathemisto gaudichaudii, Electorona sp. were newly found in addition to E. superba(Brown, 1968). He (Brown, 1968) also mentioned on the feeding habits of sei
whale being based on the observations on the stomach contents.
With development of pelagic whaling operation in contrast to declining inprincipal whale stocks, the whale species commercially hunted for were greatly
Sci. Rep. Whales Res. Inst.,.No. 26, 1974

KAWAMURA

30changed from fin to sei whales after 1964/65 season. This caused also the geographical change and expansion of the whaling ground itself, and the knowledge
on the biological characters of sei whale gradually increased in relation 1.o theneeds for stock assessment. The kind of food organisms of southern sei whale which
known recently in addition to E. superba are:- Euphausia vallentini (Marr, 1956;
Mackintosh, 1960), E. crystallophias (Marr, 1956), Thysanoessa macrura (Nemoto andNasu, 1958), E. recurva, E. diomedeae (Bannister and Baker, 1967), Parathemisto
gaudichaudii (Nemoto, l 962a ), Calanoides acutus (Peters, 1955 ), Drepanopus pectinatus(Tanaka, 1964), Ca/anus propinquus and E.jrigida (Pervushin, 1968), C. tonsus (Best,
1967; Kawamura, 1970a), Clausocalanus laticeps (Kawamura, 1970a) and so forth.
In this report more several species of food organisms would be added. Among
those above mentioned records, one by Best (1967) would be interesting since hismaterials were obtained in South African waters far outside from the so-called feed-

25
SEI

"" 20

;::

x

Fig. 1-1. Total catch of fin, blue, humpback, and sei whales in the Antarctic
pelagic whaling during the past 28 seasons. Catch of sei whale by the Japanese
fleets is shown by the hatched area. Whales taken under special permit after
1966/67 season; 3 humpback whales in 1971/72, 7 blue and 5 humpback whales
are excluded.

ing ground in southern oceans. He (Best, 1967) reported a total of more than 44
species of food organisms in sei whale stomachs. Although the principal food was
represented by a small number of species such as Calanus tonsus and some euphausiids,
his result suggests us that sei whale would feed on even the organisms which do notswarm patchily in those temperate waters. Nemoto (1959) early suggested thatsome copepods would be fed by the sei whale in some place in the Antarctic region,
but his suggestion was proved earlier than was expected as I have described above.
Recent study on the food and feeding habits of whales tends towards the analysisof both the formation of whaling ground and whale movements along with the
distribution of their food organisms (Slepzov, 1955; Nemoto, 1957, 1959; Pervushin,
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

31

FEEDING HABITS OF SEI WHALE

1968; Kawamura, 1973a), and nutritional physiology based on feeding rate ofwhales (Klumov, 1961; Sergeant, 1969; Nemoto, 1970; Kawamura, 1970a, 1971a).
Commercially important whale species in the Antatctic region have been
blue, fin, sei, humpback, right and minke whales respecitvely. However, recent
status of some those stocks are not always kept under hopeful level, and only three ofthem are currently opened for regal catches. Fig. 1-1 demonstrates the numberof catches in the Antarctic by species after 1945/46 season. The figure of the fin
whale clearly shows its distinct importance among the total catches but it was took
over by the sei whale since 1964/65 seasons. In these figure the history of the Antarctic whaling could be seen in another way as a history of shifts in commercially
important species such the circumstances as shown schematically in Fig. 1-2. The

Fig. 1-2. A rough figure showing the change in whale species which have beencaught in the Antarctic.

TABLE 1-1. CATCH OF SEI WHALE AMONG TOTAL ANIMALS IN THE PAST 28
ANTARCTIC SEASONS EXPRESSED IN PERCENTAGE FIGURES.
Seasons

Percentage

Seasons

Percentage

1945/46
1946/47
1947 /48
1948/49
1949/50
1950/51
1951/52
1952/53
1953/54
1954/55
1955/56
1956/57
1957 /58
1958/59++++

1959/60
1960/61
1961/62
1962/63
1963/64
1964/65
1965/66
1966/67
1967/68
1968/69
1969/70
1970/71
1971/72
1972/73

8.9
11. l
12.7
18.3
28.6
63.3
71.9
61.2
68.7
50.3
49.0
50.9
47.4
39.3

0.3
1.2
0.1
0.4
0.8
0.4
0.8
2.2
6.6
3.9

'+' less than 0.1 percent
Discovery Committee aimed to manage and control the Antarctic whale stocks
under scientific basis (Kemp et al, 1929). In the days of blue and fin whaling,
Matthews (1938) noted the forth comming situation that large catch effort would
be added onto sei whale in the furture, and stressed the necessity of biologicalinvestigation on this species as much as possible. When we consider the present
whaling status his anticipation must be greatly valuated. In 1964/65 season the total
number ofsei whale catch (19874 animals) exceeded that of fin whale, and showed
63.3 % among total catch in that season. In 1971/72 season the minke which
Sci. Rep. Whales Res. Inst.,.No. 26, 1974

KAWAMURA

32

had not entirely been regarded as commercially exploitable resources turned tosome importance for whaling by the pelagic floating factories, and 3000 animals
were caught successfully although it was still exploratory whaling. Under thesecircumstances in the Antarctic whaling as having been mentioned above the purpose and reasons which made me study the sei whale could be summerized asfollows:1) Food and feeding habits in the animals can be generally recognized asa whole as one of the most important event along with their breeding behavior
throughout their life history. The baleen whales are very characteristic in ecological niche through marine food chains where the very primary herbivorous organisms are connected directly with the animals in the highest trophic levels. In
connection whh these circumstances the sei whale was in need of knowledge about
its food and feeding habits and ecology since these factors in general strongly relate
to the change of animal population and the movements of whales.
2) Catch of sei whale in enormous numbers began relatively recently, andthe biological characters were poorly known particularly in sei whales. There
have been done almost no observations and analysis on sei whales food but abrief discusion by Nemoto (1962) since then the main whaling ground in the
Antarctic region shifted to further northern waters up to the Subantarctic region.
3) In connection with the shift and vast expansion in the region of main
whaling ground, several kind of food organisms began to occur newly in the dietof sei whale (e.g. Kawamura, 1970a).
4) It is hoped to recognize the mechanisms of formation of whaling ground
not only by the hydrodynamical process but also biologically through the foodconditions of baleen whales.
5) It is expected to make clear the actual distribution characters of planktonic
food organisms, especially their uneven distribution in the feeding places throughthe formation of dense swarms so-called plankton patchiness, which seems to be
ultimately responsible for the formation of feeding spot of whales.
6) The knowledge of patchy distribution of some planktonic organisms would
be useful for developing the plankton fisheries (e.g. Hempel, 1968; Parsons; 1972).
7) The study of sei whale food is desirable to be conducted while larger
number of catch of this species would be expected since the history of shifting
the whale species which have been commercially hunted teaches us the importance of properly partinent investigations.
2.

MATERIAL AND METHOD

The material used for analytical treatments were obtained from various source,
namely, pelagic whaling both in the Antarctic and North Pacific, and some werefrom land based whaling in the Japanese coastal waters. One of others wereobtained in the cruises on board of the research ships. The material can be divided
into two principal categories, namely, row material of both whale food and plankton
samples, and data in the field chiefly compiled by the Fishery Agency, Ministory
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

33

of Agriculture and Forestory and by the personnel on the floating factories.
Although the material and the method of analysis in particular will be discribed
more in detail elsewhere in the following each sections, the principal sources ofmaterial obtained are as follows:
The stomach contents of sei whale caught in the Antarctic waters were collected continuously through 1967 /68 to 1971 /72 seasons by the Japanese floating factories
and those materials were treated chiefly for examining the kind of food organisms,
their geographical and seasonal distribution. Some results obtained on the material
in 1967/68 season concerning to the food habits of sei whale has already beenreported by the author (Kawamura, 1970a).
In the seasons of both 1967/68 and 1971/72, I was on boad of the floating
factories, " Nisshin Maru " of Taiyo Gyogyo Co. and " Tonan Maru No. 2 " ofNippon Suisan Co. respectively, and engaged in general biological observationsof whale carcasses as routine work and also collected the samples of the first stomach
contents of sei and fin whales.
In the course of this study I made theoretical estimation on the population
density of Calanus tonsus, the principal prey crustacean of the sei whale, when it forms
the patches being based on both the amount of this organism found in the firststomach and relative filtering ability in the row of baleen plates (Kawamura, 197la).
To prove this result I cruised down into southern waters off Western Australia in
1971/72 season on boad of M.S. " Eiho Maru " of Hokoku Suisan Co., andmade quantitative sampling of C. tonsus by spotting its patches in the surface waters.
After finishing these investigations, I moved to the F.F. "Tonan Maru No. 2" asabove mentioned when both ships met each other on high seas.
The row materials concerning to examining the relation between the distributionof whales and of their prey zooplankton along with sea conditions were obtained in
1968/69 season by the R.V. "Hakuho Maru" during her KH 68-4 cruise down to the
Antarctic (Ocean Research Institute, University of Tokyo, 1970). With this material a quantitative and qualitative study on the food organisms of sei whale in
the Pacific sector of the Antarctic and Subantarctic waters was made, and at thesametime the distribution of sei whale and the occurrence of the DSL in relation
to that of physico-chemical elements in the region were discussed. A part ofthese results were preliminary reported (Kawamura, 1969a; 1970b, c; Kawamura
and Kureha, 1970).
Mechanisms of feeding as a function of the structure of filtering apparatus ofsei whale and its food habits were also studied. In order to estimate the capacityof oral cavity in sei whale the amount of air used for making afloat the whale
carcasses was measured on the whale boat, "Toshi Maru No. 18" which belongs
to the Nisshin Maru fleet of Taiyo Gyogyo Co. in the summer of 1969 when she
engaged in the North Pacific whaling operation, and a row of baleen plates wascollected too by that fleet to assess its relative filtering ability of the water. Whether
or not the whale vomits its stomach contents under continuous chasing was an important matter which have to be clarified when we consider the amount of stomach
contents in carcasses, and the observations for this purpose were made by six whale
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

KAWAMURA

34

boats, of which each two belonged to K. K. Kyokuyo, Taiyo Gyogyo Co. andNippon Suisan Co. respectively (Kawamura, 1971a).
To know the daily ration of sei whale theoretically the heart weight which
was proposed by Sergeant (1969) as a useful index for this purpose was weighedin 1970/71 Antarctic season at the floating factories, "Tonan Maru No. 2" and"Nisshin Maru No. 3."
There is bryde's whale Balaenoptera edeni Anderson (Olsen, 1913), which isvery similar to sei whale dealt in this study though the former has currently been
separated clearly as completely different species (Omura, 1966). According toOmura (1966) the bryde's whale distributes in the offshore waters of South Africa,
Brazil, Japan and western Australia, and a considerable number of this whale wascaught in the north-western North Pacific in recent operations. Japanese whalemen have been noticed some specific differences by calling it as the sei whale of"southern origin " or " southern type " which means the warm water species, but
it has not been treated separately in the old catch statistics of Japanese coastal
whaling. The bryde's whale are usually found in the warm waters of sea temperature higher than 20°C and its food habits also differs to some extent from thesei whales (Omura and Nemto, 1955). Best (1970), on the other hand, observed
two allopatric forms in this species in the South African waters, namely, "inshore " form which distributes in the waters within 20 miles of the coast whereas
the " offshore " form is found 50 miles or more from the coast. They differ eachother in some biological characters such as external appearance, breeding andfeeding habits.
Accordingly, it is supposed to be caught the bryde's whale along with thebulk of sei whale catch especially in the whaling area III in the Antarctic since
the sea conditions in that area are much complicated, and sei whale is widely
pursued for by the whaling fleets. Of 945 sei whales taken by the Russian fleets in
1972/73 season 5 bryde's whales were included (Intern. Whal. Stat., 1973). However, the morphological and ecological characters of bryde's whale as mentioned
above are well known currently by the whalers, and sei whale treated in thisstudy can be considered as B. borealis Lesson exclusively.
3.

BIOLOGICAL OBSERVATIONS OF WHALESThe Japanese whaling fleets which engage in the Antarctic and North Pacificwhaling operate under an obligation to record and collect the materials of every
whale carcasses treated after the instructions of whaling inspectors on boad; theactual items and the way of the observations are essentially based on those establishedby the Discovery Committee (see Mackintosh and Wheeler, 1929). The personnel
who engages in this scheme is a governmental whaling inspectors and some deck
workers of the whaling company, and the following items are observed: that is,whale species, sex, body length, foetus (body length and sex if present), stomach
contents (kind of organisms by rough grouping, the amount of food and freshness),condition of mammaly gland whether lactating in any degree or not, and its thickSci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

35ness), thickness of blubber, weight of both testes, number of corpora albicans andcorpora lutea (but they are collected for later examination if counting them on
the deck was impossible), collection of the ear plug on every carcasses and thestomach contents about every tenth of carcasses if any food present. In addition
to these, the position, date and time of catch and treatment as supplemental data.
All these data are compiled in the seibutsu-chosa-daicho, a kind of official fieldnote of the Fishery Agency, which can be reffered for statistical analysis.
The data treated in this study other than those obtained on row materials,
chiefly based on this field note. The position of catch, however, is not actual but
represented by the noon position of the mother ship. Accordingly, the positionsof catch may differ to some extent particularly those in the morning and evening.
It is, however, recognized empirically that the difference in the position is within
tenth miles, and none of those seems to cause any confusion in analysing the data
except particular cases such as the catch occurred fairly close to the convergencezone.
It is recognized anatomically and histologically that the stomach of whale iscomposed of four compartments arranged in series: the first compartment or
stomach with no digestive glands, being a kind of dilated sack of the oesophagus
origin to the fouth stomach by the extraordinarily developed ampulla (Slijper,
1958a; Hosokawa and Kamiya, 1971). The second and the third stomachs arereal gastric compartments provided with digestive glands. Accordingly, thestomach of whale carcasses is usually examined only on the first stomach since thecontents remain being undigested for long time and the second or the thrid stomachs
are examined only when there was no food remains in the first stomach. In thiscase, however, the condition of the stomach contents is recorded as " empty "( =0) in the field note above mentioned.
The food conditions of the first stomach in the whaling ground give an important suggestions for whalers to judge whether or not the whaling ground isunder suitable sea conditions as long lasting whaling ground. In the observations
on the kind of food organisms in the field, the following rough calssifications andabbreviations are adopted as have been described previously by Nemoto (1959)
and Kawamura (1970a), namely, 'Calanus' (Ca), 'Amphipoda' (Am), 'Euphausia' (Eu), 'Fish' (F), 'Squid' (Sq), 'Munida' (Mu) and so forth. Since
the stomach contents are consisted of so many species of food organisms, it is hardto distinguish all of them after the classifications especially in ' Calanus ' and ' Euphausia ', then both of which actually mean copepods and euphausiids respectively.
As for' Euphausia 'the group is divided into three sizes by the body length; ' Large '(L) for larger than 5 cm, 'Medium' (M) for 4-5 cm, and 'Small' (s) for smaller
than 4 cm., and they are recorded by one of a dominant forms in the official record.
This definition for classifying the size of euphausiids was supposedly adopted after
the way having been employed by the Discovery Committee. In those days there
had not been the problems of mixing the food organisms with more than two species
since only E. superba had consisted of foodstuff in higher latitudes (Mackintosh andWheeler, 1929). As mentioned before the sei whale is currently the most important
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

KAWAMURA

36

species, and they seem to prefer copepods or small sized euphausiids such as E.
vallentini being found in more northern waters. It may hard to distinguish thesekind of small euphausiids from young E. superba or from some another euphausiids
species expressed as 'Eu-S' in the data record. However, it is possible with considerable preciseness by reffering the result obtained on row food materials to identify
the kind of food organisms in those field record. There are no euphausiid species
that correspond to the body length of' L' and 'M' in the northern North Pacific,
but the occurrence of ' L ' and ' M ' of Euphausia was recorded in 1969 season, andwas proved later by examining the row materials collected that they were a kindof Sergestid shrimp, Sergestes similis Hansen (Kawamura, 1970d; Omori et al,1972). This fact suggests that the observations by defining the size as ' L ', ' M'
and ' S ' would be still methodologically efficient for the field work.
One of another items of observations is the fulness of stomach with food against
the capacity of stomach itself. This is recorded by five different degrees alongwith the freshness; these are, ' empty' (0 %), 'r' (less than 25 %), 'rr' (25-50 %),'rrr' (50-75 %) and' R' (75-100 %) respectively. The freshness of food organisms
therefore usually corresponds well to the fulness of stomach by its order such as'R' for 'F ', very fresh.
Food organisms as row material were collected on the every tenth of flensed
carcasses when the stomach contents were kept under good freshness for the later
examination in the laboratory. The collection of row material, however, is also
conducted to make the material characteristic in time and space when the kindof food organisms seemed different from others, when the floating factory changed
its position, and when the sei whale was caught sporadically during the period of
fin whale hunting in higher latitudes. A considerable part of this study is greatly
based on the statistical material having been compiled like this way by the J apanese floating factories during 1967/68 to 1971/72 seasons.
TABLE 4-1.
Area

Longitude

Main land and ocean included

I
II
Ill
IV

120°W- 60°W
60°W- 0°0° - 70°E
70°E -130°E
130°E -170°W
l 70°W-120°W

Eastern Pacific, South America, Falkland Is.
South Georgia Is., South Sandwich Is.
Bouvet Is., Marion Is., Crozet Is.
Kerguelen Is., Heard Is., Western Tasman Sea
Tasman Sea, New ZealandCentral Pacific

v
VI

4.

4-1.

THE ANTARCTIC WHALING AREAS ROUND THE SOUTH POLE CAP.

RECENT CATCH AND WHALING GROUND OF SEI WHALE

An outline of the whaling ground

The Japanese pelagic whaling in the Antarctic region is operated under the regulations by the IWC's arrangements, by the recommendations under the Antarctic
Teaty, and by the measures ofJapanese Government. Under these circumstances,
four species of baleen whales, i.e., fin, sei, minke and sperm whales are hunted.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

37

The whaling place is found throughout the whole circumpolar seas but it is divided
longitudinally into six whaling areas, from I to VI(Table 4-1). These whaling
areas were defined being based on the catch statistics of the blue whale for the
purpose of clarifying its sub-populations or stock units by the sea areas (Hjort andRuud, 1932; Mackintosh, 1942). The whaling areas defined thus seem to well
represent the stock unit of whales especially in blue and humpback whales whereas
they seem rather less convenient for sei and fin whales. It is, however, still con
venient to compare the catch statistics of sei whale with those other whale species.
Fig. 4-1 shows the distribution of whaling ground along with the whaling
areas where the Japanese floating factories have operated through past five seasons,
1967/68 to 1971/72. In recent whaling with quite larger number of sei whale
catch, most of whaling ground is found in the zone along the Subtropical Convergence between 40°S and 50°S, and little number of sei whale is caught alongwith larger number of fin whale in more higher latitudes, south of 50°S in theareas IV and VI. In the area VI a southerly expansion of the Subtropical Convergence toward higher latitude is very distinct particularly in the east of New
Zealand but sea conditions in this area as whaling ground of sei whale do not differ
much on the whole from other areas of mid-latitudes. In contrast to those situations the whaling ground close to the pack-ice in the south of 60°S as whaling in
1940's to 1950's when a larger number of blue, fin and humpback whales werecaught (e.g. Nishiwaki and Hayashi, 1950; Nishiwaki and Oye, 1951; Mackintosh,
1965; Nasu, 1966). Comparing with those distribution pattern in the whaling
grounds, it is clear that the sei whale is caught in the far northern waters north of
the Antarctic Convergence, and its whaling ground could be considered as the" Subantarctic" whaling ground instead of the historical "Antarctic " whaling
ground.
The whaling activity was most heavily conducted in the areas III, IV, and V
throughout the Antarctic whaling grounds, and the areas I, IV in the south ofAustralia and a part of the area V seems rather less important as sei whaling
ground due to a monotonous sea conditions there along with a prevaliling bad
weather especially in the area I. Since the bulk of the catch in the southern zone
between 45°S and 50°S is consisted of fin whale almost exclusively, and the proportion of sei whale catch among them is so little that the distribution of sei whaling
ground in the southern zone does not always represent well the status of sei whale
distribution. The center of sei whaling ground can be seen in general close to thenorthern boundary of the subantarctic region being related to a hydrodynamical
upwelling (Nasu, 1966) and the bottom topography.

Catch distribution
Fig. 4-2 shows the number of sei whale caught during 1966/67 to 1968/69
seasons by the Japanese floating factories being arranged in five degree square ofboth latitude and longitude. The region where the floating factories operated
usually correspond to the whaling ground itself, and the latter represents theregion where large number of sei whale have been spotted by the scouting boats
4-2.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

KAWAMURA

38

belonging to the fleet. Accordingly, the whaling ground itself could be consideredto agree with the distributions ofsei whale with high population density. However,it must be also taken into consideration that there are the case of small catch by
artificial reasons due to weather condition, geographical position, and less catch
effort on sei whale due to balancing relation with the period of fin whaling. It isclear in Fig. 4-2 and Table 4-2 that the sei whale is caught chiefly in the Subantarctic waters between 40°S and 50°S as a whole, and the 5 degree squares
with catch more than 100 animals distribute in the narrow zone along both northand south sides of the Subtropical Convergence. The sei whale catch in the southof the Antarctic Convergence is seen in the areas IV to VI but the actual numberof catch was relatively small except those in the area IV. The bulk of catch in
the area IV is found in 52°-53°S, the northern waters of Heard Island, and a 5
TABLE 4-2. NUMBER OF SEI WHALES CAUGHT AND ITS PERCENTAGE FIGURES(ITALICS) BETWEEN EACH 10 DEGREES OF LATITUDE IN THE ANTARCTIC.
Latitude (S)

66/67

67/68

68/69

69/70

70/71

71/72

72/73

40°-50°50°-60°60°-70°8775 71.0
2270 18.4
1315 10.6

5114 49.0
3373 33.0
1863 18.0

4178 72.4
870 15.1·
722 12.55112 87.4
212 3.6
528 9.05644 91.8
186 3.0
321 5.25329 97.7
105 1.9
21 0.43633 94.0
151 3.9
79 2.1TABLE 4-3.

CATCH OF SEI WHALE BY MONTH.
Whaling season

63/64

64/65

65/66

66/67

67/68

68/69

69/70

70/71

71/72

72/73

Dec.
Jan.
Feb.
Mar.
Apr.

552
3204
2451
1867
182

1001
7116
7690
3870
161

3202
5701
5579
2923
153

3168
3615
3673
1880
24

1812
3351
3055
2113
19

2358
1779
1484
694

2435
2055
792
570

2760
1958
875
520
38

2348
2098
540
441
28

1347
1681
488
346

Total

8256

19838

17558

12360

10350

5770

5852

6151

5445

3864

degree squares between 80°-85°E seem to be a particular case. The most distinct
trends of northerly shift in the distribution of whaling ground is found in the areas
II to IV between Folkland Islands and the Indian Ocean sectors, and the locationof these whaling grounds well agree with the mean position of the Subtropical
Convergence (Deacon, 1937). The catch of sei whale in such waters as to be considered warm temperate region greatly owe to the formation of feeding place by
the dense swarms of Calanus tonsus in the surface during mid-December to January,on which the sei whale feed voraciously. The fin whale, on the other hand, usually
preferably feeds on euphausiids and supposedly enters into the more higher latitudes
in early austral summer. It could, therefore, be considered a habitat segrigation inboth fin and sei whales. In those days when blue and fin whales were hunted exclusively, the catch of sei whale in February and March was quite sporadic (Hinton,
1925). However, by examining a long-term catch distribution, it is noticed that
Sci. Rep. Whales Res. Inst.,

No. 26, 1974

...

60

w

PALMER PEN.

~

403 230 244

30

SOUTH GEORGIA IS.

66 138 3

60°

7 15
10

0

60°

120°

.

El80°

...

48 14460

7 972 633 422 76

44 130 1135 1703

3790

338 1017 106

28 284 11 49 103.,, KERGUELEN IS.
35 1859 213 87 44

52 264 291 764 390 172 203 106

Fig. 4-2. Number of sei whales caught by the Japanese floating factories in every 5 degree squares of
the Antarctic whaling ground during the seasons from 1966/67 to 1968/69.

30

22

102 312 1012 193 503 609 223

Fig. 4-1. The Antarctic whaling ground occupied by the Japanese floating factories during the seasons
from 1967/68 to 1971/72.

o·~\60"1-------'--~~~-+-~~-~---L__:_:~~-+-~~~~~ll~I~~~~~-!--~"'-""'~

50°1------~

"•

\

180°

120°

FEEDING HABITS OF SEI WHALE

39

there are some catch of sei whale in higher latitude south of 70°S in the Ross Sea
region of the areas V and VI (Kashida, 1972; Omura, 1973).
As season goes by the feeding place formed by C. tonsus will fade out due totheir wintering migration down to some deeper waters, and the sei whale moves
into more colder region where several kind of cold water food organisms of copepods,
amphipods and euphausiids occur in swarms. The representative species of thosewaters are Calanus simillimus, Euphausia vallentini, E. superba, and Parathemisto gaudichaudii. In recent whaling operations, however, the whale species of being hunted
shifts almost to fin whale in these cold waters after catching such vast number ofsei whale in the northern waters as to fill the catch quota for the season. By
considering both the number of monthly catch as shown in Table 4-3 and thesurface temperature of the whaling ground under about 3° -4°C in March, it is suggested that the region in higher latitudes as above mentioned would be far outsidefrom the usuall distribution range of the sei whale.
The catch of sei whale by pelagic whaling during the seasons of 1931 /32 to1968 /69 is shown in Table 4--4 by separating each whaling areas. A fairly little catch
TABLE 4-4. TOTAL CATCH OF SEI WHALE IN SIX WHALINGAREAS DURING THE SEASONS FROM 1931/32 TO 1969/70.
Area

Number of animal

Percent

I
II
III
IV
VI

3708
42109
20776
12774
15066
9207

3.6
40.6
20.0
12.4
14.5
8.9

Total

103640100.0v

in the areas I and VI would be due to the treatments of total banning of the catchup to 1962, and relatively small in stock size there (IWC, 1969; 1970), and also due
to some difficulties in an actual operation by ill weather condition. The most distinct
catch is seen in the areas II where one of the most productive regions in the Antarctic, say, South Georgia and Folkland Islands waters, are included. In 1964/65
season, a total of about 2000 sei whale was caught in this area. It has been reported that the cold Weddell Current extends northward distinctly, and this would
be responsible along with a complexity in bottom topography for quite highstanding stocks of zooplankton which causes high potentials in availability offood organisms for both whales and pinnipeds (Hardy and Gunther, 1935;
Ommanney, 1936; Mackintosh, 1934, 1937; Marr, 1962). However, a quite heavy
catch in this whaling area might possibly caused a considerable local decline in
the population of sei whale, and the catch was actually very poor when two
Japanese floating factories operated again in 1969 /70 season. This fact suggests
a little rcovery in sei whale stock up to today (IWC, 1970), andt herefore the sei
whale is caught principally in the whaling areas IV and V in recent operations.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

40

KAWAMURA

The schematic distribution of sei whale based on the position and the numberof catches indicate that there are trends of efficient catch particularly in the regions
under some complexity in bottom topography which responsible for arrousing the
upwelling under the distinct meandering of the Subtropical Convergence. These
general features in distribution patern of sei whale are comparable to those foodorganisms, that is, the dense swarms or aggregations into the patches in C. tonsus(see section 11). Mentioning on the formation of whaling ground in the North
Pacific, Nemoto (1957, 1959) and Nasu (1963, 1966) pointed out the close relationships between the distribution of food organisms and the upwelling by various
origins and the situation in the Antarctic region seems to be essentially analogous
in the structure of whaling ground formation.

Suiface sea temperature in sei whaling groundThe distribution of surface sea temperature of sei whaling ground in theareas II-VI during 1969/70 season is demonstrated in Figs. 4-3a-4-3f, but the

4-3.

40°

45°S

Fig. 4-3a. Surface temperature in the Area II, December, 1969. Solid line indicates the isotherm in the first decade of a month, and dotted and chain lines
indicate those in the middle and last respectively. Both MPSTC and MPAC are
the mean positions of the Subtropical Convergence and those of the Antarctic
Convergence.

general sea conditions in the areas V and VI of the same season has already beenreported by Nasu and Masaki (1970). The surface sea temperature treated here
was observed at the ship's noon position during the period of whaling operation being measured by electric thermometer which has its sensor on the ship's bottom
about 10 meter depth. There are so much measurements of sea temperature in
actual operation, but most of them are hardly obtainable for outside use except one
as mentioned above.
Fig. 4-3a-Fig. 4-3f cover the region between Folkland Islands and western
Australia, that is, 55°W-120°E, and this region represents the principal sei whaling
groud in recent operations. An outline of the monthly temperature distribution
is as follows:
December (Figs. 4-3a-4-3b): Since the whaling ground of baleen whales is
opened in nearly mid December the material treated here covers late half of theSci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

41

month. The sei whaling ground spreads over in latitudinally narrow zones along
40°S, and the temperature of 15° -18°C occupies exclusively even in the areas
II (Fig. 4-3a) and IV (Fig. 4-3b). The whaling ground in Folkland region may
be formed by an oceanic front which originates from both the cold Folkland Current and the warm Brazil Current. Accordingly, the coeanic front distinctly
extends northward at 50° -55°W longitudes, and its position agrees in generalwith the mean position of the Subtropical Convergence in summer (Deacon, 1937).
In the whaling ground off southwest Australia the sea temperature principally
showed between l4°C and 16°C. The distribution pattern of isotherms does notdiffer much in general within the same month exept a slight southerly shift
about I 0 latitude on the whole in late December. This indicates the gradualgrow of warming conditions toward south during this month. Discussing on thesea conditions of sei whaling ground in the areas II and VI in 1969 /70 season,
Nasu and Masaki (1970) concluded that the sei whaling ground in the area II wasformed in the waters north of the Antarctic Convergence with temperature higher
110°E

40°

15.0

45°

Fig. 4-3b. Surface temperature in the Area IV, December, 1969.
Fig. 4-3a.

40°

45°S

Legends as inthan 4.5°C, but it was found also between 8°C and 10°C in the area VI. A slighttemperature differences in the whaling areas also found in the Folkland region andin the southwestern Australia region where the difference was 1°-2°C in the centerof the whaling ground. These suggest that there are some different hydrologicalconditions for the formation of whaling ground among those areas.
January (Figs. 4-3c-4-3d): Following to December the whaling was operated through the areas II to IV. In accordance with northerly extension of the
Subtropical Convergence beyond 40°S between 10° W and l5°E, the principal
whaling ground was covered with 15° - l 7°C waters during first half of January in
the Folkland region whereas it was 11° - l 4°C in the area III. In the area IV there
found l4°-l6°Cwaterscloseto the Subtropical Convergence zone in January. In
the regions south of South Africa between 10°E and 30°E, however, the distribution of sea temperature showed rather complicated features supposedly due to theformation of local fronts, some of which must have been formed by a confronting
both the warm Agulhas Current and the cold Benguela Current. These hydroSci. Rep. Whales Res. Inst.,
No. 26, 1974

~

~ S<
~.;~

·°'""'~~::> "'

?: ~

~

~

::,_,

Fig. 4-3c.

Surface temperature in the Areas II and III, January, 1970.

Legends as in Fig. 4-3a.

/ , , '->. > >, 0 ' , '"''°',_\,,,,\\\\\\\\\\\\\\\\\1\)\111i\)\l\\111il111i/111r/u,,/,,11/1111b111/1u1/11u/ru·rUrrr/,.ccc/r / / / / , . , ... ,.,IS

40'

~

~

~

~

FEEDING HABITS OF SEI WHALE

43

logical condition would be responsible for high productivity due to upwelling in theregion where forms another fertile whaling ground far outside from those in the
Antarctic region especially in the western coast of South Africa (e.g. Best, 1967).
By refering the Fig. 4-2 it is noticed that the regions of high density in the catch
number of whales in early January are found in relatively warmer waters in thenorth of the Antarctic Convergence up to 40°S., and the center of heavy catch liesin the zone of temperature above 14°0. The expansion of warmer conditions
towards the south is weakened gradually toward late January although there arestill slight trends getting warmer as being seen in the behavior of 8°0 isotherms
at 10°W. However, the temperature of the main whaling ground during January
showed 8°,..., 13°0 on the whole.
80°E

90°£

110·£

MPSTC

11. 0
10. o-.....
45°

Fig. 4-3d.

9.0-· ....
8. 0-· ....

Surface temperature, January, 1970.

Legends as in Fig. 4-3a.

February (Fig. 4-3e): There was no whaling activity in the area II in February, but the area II and a part of the area IV where involve Marion, Crozet
and Kerguelen Islands has been formed a well staple whaling ground through past
several seasons. In contrast to northern positioning of whaling ground close to 40°S
during December to January, it is found rather mid to higher latitudes with 45°460S as its center in February. The 7°0 isotherms along 35°E was found near to
45°S in late January, and it still continued shifting down to about 47°-48°S in
early February. The southerly shift of the isotherms, however, decreased graduallyduring mid to late February as observed in the feature of 7-8°0 isotherms at 40°500E and at 60°E, and the sea condition seems as a whole to be in the state of thosetypical one of mid summer. The whaling ground is found in the temperatureof 7°,..., 10°0, which was slightly colder than that prevailed in preceding month but
agreed with the result obtained by Nasu and Masaki (1970).
In view of the kind of food organisms which is responsible for forming principal sei whaling ground, the areas II and VI during December to January would
strongly be due to the mass occurrence of copepod, C. tonsus whereas more cold
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

KAWAMURA

44

water species such as E. vallentini, C. simillimus and P. gaudichaudii are responsible in
the areas III and IV. The whaling ground in the area IV along 80°E is usually
under very cold sea conditions with temperatures of 4° -6°C, where much fin whales
are caught than the sei whale. The principal food organisms are consisted of E.
superba and P. gaudichaudii, but they were replaced to D. pectinatus in the slightly
northern waters under the temperature of about 7° ....... 9°c.

Fig. 4-3e.

Surface temperature, February, 1970.

Legends as in Fig. 4-3a.

Fig. 4-3f.

Surface temperature, March, 1970.

Legends as in Fig. 4-3a.

March (Fig. 4-3f): The catch of sei whale distinctly decreases in March in the
recent operations. In the regions of Marion, Crozet and Kerguelen Islands there
was a sign of retreating the warm water toward north particularly in the region between 70°,.., 75°E. The sei whaling ground was formed under relatively colder sea
conditions of 4°,.., 7°C but the catch of sei whale was very little in contrast to thatof fin whale (Table 4--3).
Studying on the food habits of sei and fin whales of the North Pacific Ocean,
Nemoto (1957) reported a distinct preference to copepod food in sei whale. In the
Antarctic region, on the other hand, the large standing stocks of copepod species isSci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

45

usually found in relatively warmer waters in the north of the Antarctkc Convergence (Kawamura and Hoshiai, 1969; Kawamura l 969b; l 970a, b; Kawamura andKureha, 1970). Accordingly, the principal sei whaling ground during December
to March is found usually in the northern zones of the Subantarctic region, andthen it would be hardly expected a bulk of feeding concentrations of sei whale
population in the regions south of the Antarctic Convergence even in the midst of
austral summer.
5.

FOOD OF SEI WHALE

In order to know the kind and distribution of food organisms of sei whale a totalof 462 food samples was collected from the first stomach of 462 animals. The 462
food sample is comprised of both the 117 samples collected in 1967 /68 season andthe 345 in 1969/70. These row material geographically covers for the most Antarctic
TABLE 5-1. FOOD ORGANISMS OF SOUTHERN SEI WHALE
CAUGHT DURING 1967/68 TO 1971/72 SEASONS.
COPEPODAAMPHIPODA

EUPHAUSIACEAFISHES

DECAPODAOTHERS**

Calanus simillimus GIESBRECHT
Calanus tonsus BRADY
Clausocalanus laticeps FARRAN
Drepanopus pectinatus BRADY
Parathemisto gaudichaudii GUERIN
f. compressa
f. bispinosaf. intermediate
Euphausia superba DANA
Euphausia vallentini STEBBING
Euphausia lucens HANSEN
Euphausia diomedeae ORTMANN
Euphausia similis G. 0. SARS
Thysanoessa vicina HANSEN
Thysanoessa gregaria G. 0. SARS
Thysanopoda actifrons HOLT & TATTERSALL*
Gymnospelus nicholsi (GILBERT)**
Myctophum subasperum (GUNTHER)**
Scomberesox saurus (WALBAUM)
Notolepis castsi DOLLO**
Vinciguerria attenuata (COCCO)
Gonostomatid fishes**
Penaeus sp.***Cleodora sulcata (PFEFFER)
Clione antarctica E. A. SMITH
Eukrohnia hamata (MOBIUS)* Although the bipolarity of this species is reported, the occurrence isdoubtful.
** The species gathered to feed on amphipods or copepods, and are notimportant as a staple food of sei whale.
*** Doubtful in identification.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

46

KAWAMURA

whaling areas, say, the areas II-VI, and gives us well the general knowledge concerning to the distribution of food organisms within the circumpolar seas exept a
sector which involves the eastern Pacific and the Folkland Islands region.

Kind of food organisms
Although the food habits ofsei whale in 1967/68 season has been reported previously (Kawamura, 1969b, 1970a, 197lb), some of which were also treated in thisreport to make the scheme more clear in detail. In the previous repeort (e.g. Kawamura, 1969b), it was pointed out that the sei whale principally feeds on copepods
such as C. tonsus more preferably than euphausiacea in accordance with the distinct
northerly shift in the center of sei whaling ground through recent operations. The
kind of food organisms along with those admixed by a chance are enlisted by species
in Table 5-1. As having been mentioned above the food organisms in Table 5-1
can be considered to cover the almost all foodstuff of the sei whale which distributes
within the circumpolar seas in the south of 40°S. By comparing with the foodstuff known in the northern North Pacific and Bering Sea, (Nemoto, 1957, 1959),
Kawamura (1973a) showed that those in the Antarctic region seem to be quite monotonous as a dietary environments for baleen whales, i.e., the Antarctic environment
lacks some micronectonic organisms such as the fishes molluscs, and crustaceans like
Sergestid shrimp (Omori et al., 1972). Although Nemoto (1962a, b) early reported
the newly known food organisms as found in sei whale stomachs, the principal foodstuff of sei whale in the Subantarctic waters is consisted of both copepods and small
sized euphausiids, and this fact is far different from the previous recognitions ofdepending solely on euphausiids. The following species could be considered as
newly known food orgnaisms in the Subantarctic and Antarctic regions in addition to those reported previously. They are: C. tonsus*, Clausocalanus laticeps,
Thysanopoda actifrons, Euphausia diomedeae, E. lucens, Penaeus sp. and Scomberesox saurus.
Among those food organisms given in Table 5-1, the following four species
might be the most important throughout the Subantarctic waters from their distinct occurrence in the sei whale stomach: C. tonsus, C. simillimus, E. vallentini, andParathemisto gaudichaudii. In addition to these species both Clausocalanus laticeps andDrepanopus pectinatus could be considered to be particularly important in a local sea
reg10ns.
Nemoto (1962a) early suggested that E. similis which had not been reported
as whales food would be found in the whale stomach when the whaling groundshifted to another place in the future, since E. similis forms dense swarms in thesurface water. By examining the foodstuff of minke whale, Balaenoptera bonaerensis
caught in 1967 /68 season, I found the occurrence of E. similis as food in several
number of animals (Ohsumi et al, 1970) and again in sei whale caught in 1969/70
5-1.

* Salinikov (1953, Table 4) described C. tonsus as a food of baleen whales in the North Pacific waters.

However, it is obvious in the studies by Tanaka (1954, 1956) that Salinikov's C. tonsusmust be separated from theso-called C. tonsus, the endemic species in the southern hemisphere. C. tonsus was also reported as sei whale
food from the Cape Province, South Africa (Best, 1967) but I enlisted the species again in this report since
Cape Province is located at about 33°8 being far outside from the Antarctic region proper.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

47

season. These facts strongly suggest that the food organisms of baleen whales
would supposedly form the dense swarms or aggregations into patchiness. These
results lead to a consideration that the southern saury, Scomberesox saurus andPenaeus sp., both were found in this study, also seem to form the swarms in the surTABLE 5-2.

COMPOSITION OF FOOD ORGANISMS IN THE STOMACHS OF THE
SOUTHERN SEI WHALE 1967/68.
No. ofKind of food organisms
whalesexamined

C. tonsus (CV & Female)
C. tonsus (CV)-P. gaudichaudii f. compressa (Female)
C. tonsus (CV)-P. gauchichaudii f. bispinosa (Female)
C. tonsus (CV & Female)-£. vallentini (Female & Juvenile)
C. tonsus (CV & Female)-£. sp. (Furcilia)
C. tonsus (CV)-E. vallentini (Female)-£. hamata
C. tonsus (CV)-P. gaudichaudii (Female)-£. vallentini (Male, Female & Juvenile)
C. tonsus (CIV & CV)-E. hamata-Clione antarctica & Cleodora sulcata
C. simillimus (CV & Female)C. simillimus (CIV & CV)-Drepanopus pectinatus (Juvenile)
C. simillimus (CV)-E. vallentini (Male, Female & Juvenile)
C. simillimus (CV)-E. sp. (Male & Furcilia)
C. simillimus (CV)-P. gaudichaudii f. compressa (Male & Female)C. simillimus (CV)-P. gaudichaudii f. bispinosa (Female)C. simillimus (CV)-G. nicholsi
C. simillimus (CV)-P. gaudichaudii f. compressa (Male & Female)-E. vallentini (Juvenile)
D. pectinatus (Male, Female & Juvenile)
D. pectinatus (Juvenile)-C. simillimus (CIV, CV & Female)
C. laticeps (Female & Juvenile)23

P. gaudichaudii f. compressa (Female)
P. gaudichaudii f. bispinosa (Female)-£. compressa (Female)
P. gaudichaudii f. bispinosa (Female)-E. vallentini (Male & Juvenile)
P. gaudichaudii f. compressa (Male & Female)-P. gaudichaudii f. bispinosa (Male & Female)E. superba (Male & Female)
P. gaudichaudii f. compressa (Female)-gaudichaudii f. bispinosa (Female)E. vallentini (Male, Female & Juvenile)
P. gaudichaudii f. bispinosa (Female)-E. vallentini (Juvenile)-C. simillimus (CV)918
1Euphausia superba (Male, Femal & Juvenile)
E. superba (Male, Female & Juvenile)-Myctophum subasperum & Gymnospelum nicholsi
E. vallentini (Male & Female)
E. vallentini (Juvenile)-D. pectinatus (Juvenile)

14

1

2
2

1
4
3
2
1
2
2

4
2
2

10

Degree of dominancy is on decrease from left to right in the left column and the dominant formsof each organisms are shown in parentheses.
Note: CIV-the fourth copepodites, CV-the fifth copepodites.

face waters. A little number of myctophid fishes, chaetognatha, and pteropods
were also found as contaminants. They must have been fed by a chance when theygathered in the surface waters in search of their prey organisms such as copepoda
and euphausiacea, and have little importance as sei whale food. This kind of
mixture not only occur in the mid latitudes but also occur in more higher latitudes.
Sci. Rep. Whales Res. Inst.,

No. 26, 1974

KAWAMURA

48

According to Brown (1968) the sei whale caught in the South Georgian waters
had fed on Electorona subasper and E. normani along with E. superba, and he (Brown,1968) called them as " occasional occurrence ". By discussing the diel vertical
distributions of those myctophid fishes, Brown (1968) also supposed that the bulk of
sei whale feeds actively in the evening since those fishes usually come up near to thesurface in the night. It might, however, rather difficult to know the active feedingtime of sei whale like this way since there are also the fact that the sei whale does
not seem to feed at any definite time of a day but feed whenever there are a foodstuff
available (Kawamura, 1970a).

5-2.

Composition of the stomach contents
As mentioned before the most important food organisms for sei whale in the
Subantarctic and Antarctic waters are C. tonsus, C. simillimus, P. gaudichaudii, E. valTABLE 5-3.

COMPOSITION OF FOOD ORGANISMS IN THE STOMACHS OF THE
SOUTHERN SEI AND FIN WHALES, 1969/70.
ParaCalanus
Calanus Drepa- Euphausia Euphausia Euphausia Euphausia themisto Notolepis
tonsus simillimus p ntopust
lucensvallentini superba diomedeae
gaudicastsi
ec ina uschaudii,.-"-.., , . - " - . . , , . - " - . . , , . - " - . . , ~ ~~Sei Fin Sei Fin Sei Fin Sei Fin Sei Fin Sei Fin Sei Fin Sei Fin Sei Fin--------- ---------

C. tonsus
203* 3
C. simillimus
2
Th. vicina
Th. gregaria
1
Th. sp.
3
E. lucens
E. vallentini
E. superba
E. similis
E. diomedeae
Th. actifrons
1
P. gaudichaudii 19
Penaeus sp.
4
S. saurus
1
V. attenuata
N. castsi

5**

2

10 38

8

8

20

2

I & II : Order of dominancy.
* Including a mixture with Pseudochirella sp. in the Order II.
** Including a mixture with a few individuals of P. gaudichaudii, E. vallentini, Th. gregaria and E.
hamata in the Order II.

lentini and E. superba, whereas in Saldanha Bay, South Africa there has reported
more than fourty five food species; seven euphausiids, twenty of copepoda,
six of amphipoda, four of fishes, six of pteropoda and some others such as
megalopa larvae, and Vellella sp. (Best, 1967). However, there were only 8-9
species which seemed to be actually indispensable as food of sei whales there.
The most of other species might have found as "occasional occurrence", thoughSci. Rep. Whales Res. Inst.,
No. 26, 1974

9+

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52

organisms. It was also known that the number of species contaminated does notexceed more than two, and they also never exceed the major species in quantity,
except when the fishes were contaminated; that is, the food of sei whale usuallyformed with a species which occurs dominantly in the sea concerned. As far as theindividual numbers observed are concerned, the sei whale in the Antarctic waters
feed selectively with prefering orders of copepoda-euphaussiid, amphpoda, orboth of them-other crustaceans, and then fishes or squids as has been reported in
the North Pacific sei whale (Nemoto, 1957; 1959). However, the food preference
in sei whale varies to some extent by the case. For instances, they feed chiefly on
E. lucens, E. recruva in the South African waters, and copepods such as C. tonsus, C.
carianatus, Clausoclanus arcuicornis f. major follow to the former (Bannister and Baker,
1967; Best, 1967). Although the "selection" by the kind of food organisms inbaleen whales is still in need of more discussion, there seems to be no other ways tobelieve it possible by adding more facts observed in the North Atlantic baleen
whales where Howell (1930) described the selective feeding habits with the orders
TABLE 5-4.

MONOSPECIFIC DEGREE IN THE STOMACH CONTENTS OF SEI WHALE
IN FIVE MAJOR SPECIES OF FOOD ORGANISMS.
No. ofNo. ofmonospecific mixed
samplessamplesSpeciesCalanus tonsus
Calanus simillimus
Parathemisto gaudichaudii
Euphausia superba
Euphausia vallentini

1967/68
1969/70
1967/68
1969/70
1967/68
1969/70
1967/68
1969/70
1967/68
1969/70

23
203
4
4
27
20
14
8
10
10

9
34
12
2
4

No. of species
mixed
~

1

2

6
34

3

11

3

No. of Monospecificsamplessamples
examined
(%)
32
237
16
6
31
21
15
8
11
10

71.9
85.6
25.0
66.6
87.1
95.2
93.4
100.0
91.0
100.0

of small shrimps, anchovy, smelt, and then mackerel. In the Antarctic waters, on
the other hand, many sei whale actually feeds on C. tonsus at first then P. gaudichaudii or E. vallentini and finally E. superba notwithstanding the fact that there must be
exist so rich distribution of E. superba in the higher latitudes when they enteredinto the southern feeding place in early summer. According to my unpublisheddata the surface swarms of young euphaudiids and amphipods are observed often
in the Subantarctic waters of relatively higher latiturdes, but they never found in
the stomach contents of sei whales there. They feed exclusively on the adult formsof E. vallentini or P. gaudichaudii. However, it is still unknown that these are dueto the size of food organisms as particles. By examining the sei whale food andfeeding in South Georgian waters, Brown (1968) reported a opposite opinion that
there were no facts to believe the selective feeding habits in sei whale.
As shown in Table 5-1 the most important food organisms of the sei whale wascopepods but an actual feeding habit of sei whale seems slightly more complicatedSci. Rep. Whales Res. Inst.,

No. 26, 1974

FEEDING HABITS OF SEI WHALE

53

when Penaeus sp., Scomberesox saurus, and several another organisms occur locally as
being found in 1969 /70 season. The feeding habits of sei whale can be considered
as a whole that they feed on any kind of swarm forming organisms which dominantly
occur within their migratory regions. Bannister and Baker (1967) have also been
pointed out on this character by examining the feeding of baleen whale at Durban.
However, it must be noted that both chaetognatha which does not swarm into socalled patchiness, and tunicates which is not preferable organisms, are avoided atleast by sei whale notwithstanding the fact that they usually occur quite abundantlyin the feeding place of baleen whales.

Geographical 'distribution of food organisms
Since considerable large number of sei whale is caught by the floating factories, it is hardly possible to examine or collect the row materials of the somach contents on every carcasses. So the the food samples are usually collected with someintervals in time and space such as every tenth of carcasses, or every shifts in noon
position of the fleets. As mentioned in the foregoing section the kind of foodorganisms are recorded on the every carcasses regardless the collecting samples.
By comparing both row and data materials together, it is possible to figure out
the general geographical distribution of food organisms. The results are shown in
Figs. 5-1 to 5-3, each of which represents the distributions of copepods, amphipods, and euphausiids respectively.
In the overall distributions of copepod food, Calanus tonsus not only occurreddominantly in the south of 40°S covering vast circumpolar regions throughout theareas II to VI, but also was fed most frequently in the region. Its occurrence as
sei whale food well agrees with the distribution of patches in the surface waters underclose relation to the Subtropical Convergence (see also section 11 ). As has mentioned in the foregoing section, it must be noted that only swarm forming organisms
could be fed by the sei whale, i.e., the distribution of C. tonsus as described above
supposedly present a little different figures from those known as geographical distribution range of this species. The biomass usually found in its patches is maintained such high density as to be hardly comparable to that known in general, andhas been considered to be a characteristic niche in the marine ecosystem. Since thewhaling in the Antarctic region is opened in the south of 40°S the northern boundary in the distribution of C. tonsus in Fig. 5-1 does not show its natural habitat but
artificial. The center of rich distribution of C. tonsus is usually found in the vicinity of the Subtropical Convergence (e.g. Kawamura and Hoshiai, 1969) but its
northern most boundary may extends beyond upto 30°S or thereabouts.
According to Brodskii ( 1964) C. tonsus occurs under the temperature of 5 °,..,
l5°C, and its rich occurrence is observed between 8.5°C and 12.3°C off Otago
Peninsula, New Zealand (Jillett, 1968). In this study the surface sea temperaure
at which C. tonsus occurred as food of sei whale during December was between 9.5°
and 18.0°C. Judging from feeding percentages by sei whale the most preferable
temperaure for this species was supposed to be 9.0°,.., 13.0°C, and these sea condi-

5-3.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

54

KAWAMURA

tions correspond to the Deacons' mean temperature of the Subtropical Convergence during austral summer (Deacon, 1937).
A distinct southerly extension in the distributions of C. tonsus down to 55°S between 160° and 170°W longitudes would be comparable to the southerly shift of
the Subtropical Convergence. Actually, the Subtropical Convergence at 170°W
in 1968/69 season was located in the vicinity of 55°S latitude (Ocean Res. Inst.,
1970).
In the plankton communities of South Georgian waters including northeast
Weddell Sea and Scotia Sea, C. tonsus does not occur (e.g. Mackintosh, 1934;
Hardy and Gunther, 1935), since these regions are influcenced under a northward
movement by the cold Weddell Current lower than 5.0°C. In general C. tonsus distributes abundantly throughout the subantarctic regions so as to be fed by the sei
whale under relatively warmer conditions, i.e., 10°,..., l5°C, and no other kind of organisms which are comparable with C. tonsus as whales food were found. In thispoint of view C. tonsus could be considered ecologically most important species
being comparable with C. jJlumchrus or C. finmarchicus in the northern hemisphere.
Following to C. tonsus the secondly important food copepoda is C. simillimus.
However, as it is seen in the distributions, C. similliums occurred in the Indian sector
where both Crozet and Kerguelen Islands, and also a part of Atlantic sector are involved. So the occurrence of C. simillimus is considered rather local and hardly
comparable with that of C. tonsus as food of sei whale. This species distributes on
the whole in the slightly southern waters than C. tonsus with the distribution center
between 45° and 50°S. It is note worthy that the distibutions of C. simillimus and
C. tonsus is closely located geographically but never overlaps each other. In contrast
to rather earlier occurrence through December to January in C. tonsus, C. simillimus
occurred mostly around February. Accordingly the sea temperature when theyoccurred was also different: C. simillimus food was found under the temperaures of
5.0° -9.1°C in 1967 /68 season. According to the distributions of copepods obtained by the Japanese Antarcic Research Expedition (Kawamura and Hoshiai,1969), the successive occurrence of C. tonsus was replaced with C. simillumus at about
45°S in the southern waters of South Africa, when the surface sea conditions were
7.5°C with salinity of 34.07%0. These facts suggest that the lower most temperature for C. tonsus distribution may be 7.0°C or thereabout whereas it may be
the higher most temperature for C. simillimus. Although both C. tonsus and C. simillimus are the Subantarctic species, the former could be regarded as northern warmer water species while the latter as southern cold water species.
D. pectinatus occurred only in the waters around Kerguelen and Crozet Islands.
In the waters in the vicinity of Crozet Islands distribution of this species agreed
well with that of C. simillimus but not in Kerguelen waters where none of C. simillimus occurred at all. Nemoto (1962) also reported D. pectinatus as sei whales foodonly in the waters around Kerguelen Islands. Kerguelen Islands is located on the
Kerguelen-Gausberg under water ridges and forms a shallow depth zones which
are rarely found in the high seas in the Antarctic region. The characteristic occurrence of D. pectinatus as above mentioned may supposedly due to a local hydroSci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

55

logical conditions caused by a kind of upwelling of deep waters in the IndianAtlantic Basin.
Clausocalanus laticeps is one of newly found food species in the Pacific sector ofaround 180° meridian. Although its distribution area agrees with that of C.
tonsus, C. laticeps occurred as monospecific population without mixing with anyother food species. Among the euphausiid species shown in Fig. 5-2, both E. vallentini and E. superba are the most important species in the feeding percentages andlarge shares as biomass in a stomach contents. In the mid-latitude zones theeuphausiid food represented almost exclusively by E. vallentini. Nemoto (1961)
added this species in the dietary list of southern baleen whales after finding its occurrence as food of pygmy blue whale, B. musculus brevicauda (Ichihara, 1961: Omura
et al, 1970) in the Kerguelen waters. Mackintosh (1960) had early suggested an ecological importance of E. vallentini when there had not been any scientific evidences on
the role of this species among marine food-chains. In the areas II and III E. vallentini is fed in a narrow zone between 45° and 47°S but in the areas II and IV, theIndian sector, this species was frequently found under admixing with P. gaudichaudii. Although the most E. vallentini as the case in copepods is usually fed during
December, its distribution centered in rather southern waters within the Subantartic zone. A completely isolated occurrence of E. vallentini was seen in thesoutheastern waters off New Zealand. Since its distribution is clearly isolated
from that of C. tonsus, E. vallentini could be considered a typical Subantarctic species, and these facts agree with the result by Nemoto (1962a), in which he suggested
that the distribution pattern of E. vallentini as whales food seems to agree to someextent with the distributions of shallow zone by continental shelf and under waterridges. In the environs of New Zealand particularty in its eastern regions the continental shelf develops well, which might be responsible both for the upwelling anda local swarming phenomena by E. vallentini.
As the whaling season proceeds the sei whaling ground also shift gradually
toward south. In accordance with this shift the food organisms of sei whale alsochanges into E. sujJerba which distributes in the waters south of the Antarctic Convergence, a representative of the whales food in the region. However, it seems
rather less important as sei whale food since relatively small number of sei whale
migrates into the higher latitudes in the south of the Anatrctic Convergence. Other
euphausiids species such as E. lucens, E. similis, E. diomedeae, Thysanoessa vicina, Th.
gregaria and Tfrysanopoda actifrons, were also found in slightly northern regions thanE. vallentini as sei whale food, but their occurrence was quantitatively small andrather sporadic. In this sence they seem less important as sei whales food. According to Nemoto (1957), Th. macrura was one of other kind of important species asa food of fin, blue and humpback whales but none of individuals of Th. macrura
was found in the sei whale stomachs in this study. Nemoto (1957) also had not
found its occurrence in sei whale. These facts are characteristic when comparedwith the case in E. superba since Th. macrura also distributes in the waters near to
ice-pack (Nemoto, and Nasu, 1958). One of a possible explanations is that Th.
macrura shows rather sporadic and local distributions than E. superba in addition
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

56

KAWAMURA

to its habitat in higher latitudes.
Parathemisto gaudichaudii, one of the most important food organisms for sei
whale which widely distributes in the Subantarctic waters with the center between
45° and 50°S, i.e., relatively southern waters near to the Antarctic Convergence(Fig. 5-3). Accordingly its general features of the distribution resemble with thatof E. vallentini. However, it would be noticed by comparing the distribution character with E. vallentini that the occurrence of P. gaudichaudii as food of sei whale ismuch sporadic, that is, P. gaudichaudii forms the patches so as to be fed by the whale
but distributes sporadically. P. gaudichaudii occurred most distinctly in the Indian
sector of the areas III and IV where the bottom topography is complicated by thepresence of many islands such as Kerguelen, Crozet, Marion and Heard Islands.
So its distribution resembles to that of E. vallentini. Although Nemoto (1962)
found P. gaudichaudii in the stomach contents of fin and pygmy blue whales, thisfood species would supposedly be preferred much in sei whale from the general
selecting feeding habits of baleen whales. The general agreements in the distribution of both E. vallentini and P. gaudichaudii suggest a possibilities of their co-existingin time and space. Actually they occurred in the food of sei whale by admixing
each other in some sea regions of the Indian sector (see Fig. 5-2).
Penaeus sp., Scomberesox saurus, Vinciguerria attenuata and some other kind of
myctophid fishes occurred in relatively larger quantities but were found to be lessimportant since they were considered as the contaminants mixed with the principal
food zooplankton populations. Among those above mentioned organisms, Genus
Vinciguerria, a kind of gonostomatid fishes, would be regarded relatively importantsince it forms a potential foodstuff of the skip Jack, Katsuwonus pelamis at times in
the Pacific Ocean (Kubota and Kawamura, 1972).

Latitudinal change in the distribution of food organisms
In 1967 /68 season two of four floating factories operated relatively widely
through latitudinal zone, and the materials obtained from those two fleets madeit possible to analyse the change in geographical distribution of food organisms
in terms of the feeding percentages. The general features of latitudinal change
in the Indian sector is demonstrated in Fig. 5-4 and those in the Pacific sector alongwith the Tasman Sea region is in Fig. 5-5. The feeding percentages are expressedby the ratio of the number of animals with food in the first stomach against the
total number of animals examined. " Calanus " in the figures does not mean the
Genus Calanus in taxonomical sence but represent the copepod although most of
the case in " Calanus" is represented by C. tonsus and C. simillimus (Tables 5-2 and
5-3).
In both figures it is noticed clearly that " Calanus " food being represented
by C. tonsus and C. simillimus occurs exclusively in the waters south of 40°S, down
to amidst of the Subantarctic region of about 47°S i.e., the northern half of the
Subantarctic waters of the main sei whaling ground of the copepod richwaters. Getting closer to southern region of the Subantarctic waters close
to 50°S., the representative food organism gradually changes to small-sized eu5-4.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

57

phausiids such as E. vallentini, but P. gaudichaudii was also fed by the whale in someplaces under both monospecific composition and mixture with E. vallentini. P.
gaudichaudii increased gradually in the share of occurred food organisms toward
the Antarctic Convergence. In the south of the Antarctic Convergence the dominancy of E. vallentini in a stomach contents replaced with P. gaudichaudii but thelatter is again replaced gradually with euphausiids of adult and adolescent forms
80

70

"'""

60

AC

STC
Total
-·- Euphausia (LJ--- Calanus-·-·- Euphausia (M)•••••• Amphipoda --·· Euphausia (S)

~ 50
2l

£ 40

:.a"" 30"'

Lf 20

LatitudeFig. 5-4. Latitudinal change in the occurrence of food organisms for sei whale in
the Indian sector of the Antarctic. STC: Subtropical Convergence, AC: Antarctic Convergence.

Fig. 5-5. Latitudinal change in the occurrence of food organisms for sei whalein the Pacific sector of the Antarctic and in the Tasman Sea region. STC: Subtropical Convergence, AC: Antarctic Convergence.

of E. superba. In the waters south of65°S I-year group of E. superba occurs sporadically in the stomach of sei whale. Thus the occurrence of the food organisms distinctly changes in latitudinal direction. It is note worthy that these successivechanges occur within the narrow zone of about 20° degrees of the latitudes.
The food organisms of sei whale in the waters of the both Subantarctic andAntarctic occurred toward higher latitudes in the order of copepod, euphausiid,
amphipod, and then again euphausiid. In the waters north of the Antarctic
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

KAWAMURA

58

Convergence E. vallentini was fed more preferably than P. gaudichaudii notwithstanding the fact that the former is less abundant than P. gaudichaudii in the region, andfeeding on P. gaudichaudii by the whale was distinctly increased in the south of the
Antarctic Convergence (Fig. 5-5). According to Kane (1966), P. gaudichaudii
distributes most abundantly in the waters around the Antarctic Convergence especially in its northern side. These facts lead to a consideration that the sei whalefeeds more preferably on euphausiids than amphipods while the former seems tobe less abundant than the latter in the region concerned as a function of selective
feeding habits, although it is still unknown whether the food selection is caused bymechanical process or some kind of biologically potential preferance. It may also
be possible that the selection of the food organisms in feeding habits would released
only when rich food organisms were available in the region. The selective feeding haibts in sei whale also corelate to the distribution pattern of the food organisms
whether they form the patchiness or not.

5-5.

Distribution offood organisms by the whaling area
As mentioned in the foregoing section, the food organisms of sei whale changes
one to another in a narrow latitudinal zone. The general circumpolar hydrologicalconditions in the surface waters of the Antarctic Ocean shows rather monotonous
TABLE 5-5. FEEDING PERCENTAGE (ITALICS) AND ACTUAL NUMBER OF WHALESIN THREE MAJOR FOOD ORGANISM GROUPS BY THE WHALING AREAS
III TO VI IN 1967/68 SEASON.
Kind of food organisms
Area & Sector

Calanus Ampdhipo a

Areas III & IV
191
207*
(Indian Ocean)
13.64 12.58
Areas IV & V
357**
73(Tasman Sea & Pacific Ocean) 28. 61
5.85
Areas V & VI
888
70
(Pacific Ocean)
34.82
2.75

E h "dUnE~known*** mpty

L

M

S

115

23

59

919

7.58

1.52

3.89

60.54

17

203

537

1.36 16.27

43.03

61

4.89

575

9

1008

22.55 0.35

39.53

Food/
Total

No. of
inds.
Total
1518

39.46
1248

56.97
2550

60.47

* Includes Drepanopus pectinatus.
** Includes Clausocalanus laticeps.
*** Not examined.

features (Deacon, 1937), that is, the hydrological conditions are less variable by
the whaling areas in contrast to those in latitudinal direction. In order to figureout the change in the occurrence of food organisms by the whaling areas, the composition figures were given in Tables 5-5 and 5-6. In the tables the occurrenceof food organisms by each whaling areas were expressed in feeding percentages
along with the number of animals examined. To make comparison with the caseof fin whale its figure was also given in Table 5-6. The kind of food organisms
expressed in the tables would be known by refering the foregoing sections. Bothlarge (L) and medium (M) sized euphausiids represents the 1- or 2-year group of
Sci. Rep. Whales Res. Inst.,

No. 26, 1974

FEEDING HABITS OF SEI WHALE

59

E. superba and small (S) sized one is represented mostly by E. vallentini or E. lucens
in mid-latitudes and by the young E. superba in higher latitudes. Only P. gaudichaudii corresponds to amphipods (Am).
The feeding percentages in 1967 /68 season showed 52.3% on an average andthose in 1969 /70 was 48.6 % through the whaling areas II to VI whereas fin whale
showed 58.6%. Their percentage figures suggest that an approximately 50%
of sei whale caught in the whaling operations carries food contained stomachs.
The feeding percentage of fin whale was slightly higher than that of sei whale.
The feeding percentage by the whaling areas in both 1967 /68 and 1969/70 seasonsvaried 39.46-61.22%, which suggests the different feeding conditions to someextent by the whaling areas. In the feeding percentages by the kind of foodorganisms, "Calanus" (=copepods) food showed only 13.64% in the Indian
sector of the areas III and IV in 1967 /68 season while they increased gradually
toward the Pacific sector where the feeding percentage attained at 34.82% (Table
5-5 ). The " Calanus " food through the areas II to IV in 1969 /70 season showed
a quite high percentage being higher than 60% in the area II whereas they
decreased about one half in the areas III and IV.
TABLE 5-6. FEEDING PERCENTAGE (ITALICS) AND ACTUAL NUMBER OF FIN AND
SEI WHALES IN FOUR MAJOR FOOD ORGANISM GROUPS BY
THE WHALING AREAS II TO IV IN 1969/70 SEASON
AreaSpeciesofwhalesCalanus Am~hipo a

675

Euphausiid
~

L

M

s

2

8

0.18

0.71

Sei

60,32

Fin

30,00

Sei

29.68

Fin

1.10

Sei

579

47

34

35.76

2.90

2.10

Fin

9

445

16

18

1.34

66.12

2.38

2.67

II

III

IV

12

30.00
42

61
7.77
4
0.37

5.35

1

0.06

2

0.26

Food/
Total

No. of
inds.
Total

38,78

434

61.22

1119

8

40.00

60.00

20

446

56.82

43.18

785

UnEmpty
known**

6

6

233

Fish*

1

0.13

486

1

585

44.67

0.09

53.77

46.23

1088

950

58.67

41.33

1619

184

72.66

673

6

0.37

2

0.12
1

0.15

27.34

* Notolepis castsi.
** Not examined.

These results as observed in both seasons suggest that " Calanus" food might
be relatively less important in the Indian sector especially in the environs of Crozet
Islands. The relatively low feeding percentages of " Calanus " food in thesewaters well agree with the result obtained by Pervushin who studied on the materials during 1961/63 to 1964/65 seasons (Pervushin, 1968). On the other hand,a relatively high percentages in the areas II of Folkland Island sector and theareas V and VI indicate a potentential importance of " Calanus " food in thoseregions. However, the "Calanus" food can be regarded potentially important
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

60

KAWAMURA

diet for the sei whale whereas they seems less important for the fin whale throughout
the whaling areas. The general trends to feed more on euphausiids than copepod
in fin whale are clearly seen in Table 5-6.
Although the importance of "Calanus" food for sei whale may be quite
evident in general, the fullness of the first stomach with " Calanus" food proved
less than 50%, and none of fully repleted stomachs were observed. This fact indicates that the population density in terms of the biomass in " Calanus " foodwould be less than that in euphausiids and amphipods even when they aggregated densely to show the patchiness. Copepods as food of sei whale have been wellknown early (e.g. Collett, 1886; Ingebrigtsen, 1929; Nemoto, 1957; 1959; Kawamura, 1970a, b) and their more importance for southern sei whale than any otherorganisms is proved in this study. Accordingly it would be possible that the sei
whaling at least in December to January was determined primarily by the distribution of" Calanus" food.
Different from" Calanus" food, amphipods (P.gaudichaudii) was fed by 12.58%
of sei whale in 1967/68 season and by 7.8% in 1969/70 season. These figures
are rather lower when compared with the case of " Calanus " food. Among thewhaling areas concerned relatively high feeding percentages were observed in
the Indian sector of the areas III and IV in both seasons. However, the feeding
percentages in 1969/70 season leveled cosiderably lower than in 1967 /68 season as
well as having been noticed in " Calanus " food. These phenomena are still notproved yet, but supposedly due to the variation in geographical distribution alongwith year to year fluctuations in the population size of the food organisms. The
low feeding percentages in 1969/70 season also agree with those observed ineuphausiids. Since these trends are quite similar through the three kinds of foodorganisms, it is supposed that they must had not been influenced under theenvironmental control onto their developmental stages.
Large and medium sized euphausiids, say, E. superba had been fed quite little
by the sei whale in 1969/70 season. The feeding percentages showed only 2.16%
for large sized euphausiid in the area IV whereas it was 7.6% in the Indian sectorof 1967 /68 season. The latter was the highest feeding percentages through bothseasons. In 1967 /68 season euphausiids showed relatively higher feeding percentages than copepods and this relationship reversed in 1969 /70 season. A relative low feeding percentage in large and medium sized euphausiids supposedly due
to the geographical location of main sei whaling ground, and the varations between
whaling seasons would be due to the environmental factors which are responsible forthe development of young copepods. The sei whale might have fed on E. superba
when copepods such as C. tonsus was poorly available. Studying on the food ofbaleen whales in the North Pacific, Nemoto (1959) concluded that there must be
both Calanus rich year and euphausiids rich year in those region. A similar phenomena may be considered in the Antarctic whaling ground.
In small sized euphausiids, however, the general circumstances seem different
to some extent. Different from large sized euphausiids the small sized one ischiefly represented by E. vallentini and E. lucens, and their feeding percentages inSci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

61

the Pacific sector of the areas V and IV showed 22.6%, a relatively high ratio
though it decreased gradually toward the west through Tasman Sea, Indian sector
and then Atlantic sector respectively. In 1969/70 season the feeding percentages
were distinctly low throughout the areas II to IV, and no areal variations wereobserved. The occurrence of small sized euphausiids may also be related to theabundance of copepods as having been suggested in the large sized euphausiids.
According to Baker (1954) the circumpolar distribution of zooplankton in the
Antarctic region shows a monotonous features on the whole through the three
oceans whereas they distinctly change in the north-south direction, and both of thesecircumstances agree well with the general hydrological conditions. The geographical changes in the feeding percentages of sei whale also agree as a whole withthe results reported by Baker (1954). A local but distinct occurrence of C. simillimus and P. gaudichaudii in the sei whale food agrees too with their general distribution patterns, that is, the distribution of food organisms does not differ fromthat of zooplankton.
6.

DISTRIBUTION OF WHALES, AND ITS RELATION TO PHYSICAL,CHEMICAL AND BIOLOGICAL ENVIRONMENT FACTORS

Studying on the food and feeding of sei whale caught in the 1967 /68 and 1969 /70
seasons, it was considered that the regions where feeding ground is formed in the
Subantarctic zone would closely related to the characteristic features in the distribution of food organisms. For instances, the feeding ground being formed by
the copepodite V stage of C. tonsus during early summer diminishes gradually as totheir seasonal vartical migration into the deeper waters (Jillett, 1968), and theseenvironmental changes make the whale move into more higher latitudes in searchof another foodstuff such as C. simillimus, E. vallentini and P. gaudichaudii. Thus,
the geographical shift in the whaling ground closely relates to the ecologicalcharacters in the distribution of food organisms.

6-1.

Distribution of whales and the environmental factors in the Pacific and Antarctic Ocean

Apart from the biological examination on whale carcasses, the oceanographical investigations along with plankton sampling and whale sighting were madeduring the KH-68-4 cruise of the R. V. "Hakuho Marn" of the Ocean ResearchInstitute, University of Tokyo, and a part of biological works made in this cruise
have already been reported (Kawamura, 1969a, 1970b, c; Kawamura and Kureha,1970). Leaving Tokyo on November 14, 1968, the research cruise ofKH-68-4 wasmade along two transections, i.e., l 70°W from 30°N down to 70°S and 155°E from
38°S to 70°S. The track along l 70°W crossed in the midst of main sei whaling
ground where one of the Japanese floating factories operated for two successive
seasons through 1967 /68 and 1968/69 (Ocean Res. Inst., Univ. Tokyo, 1970). A
total of 61 oceanographic stations were occupied during the cruise, and the plankton
collection from 150 m depth upto the surface was also conducted routinely with
the North ]Jacific standard net, and also several series of divided hauls from great
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

62

KAWAMURA

depths with the Petersen type vertical closing net. Of approximately 9,000 miles
cruise 2,100 miles of the track was sighted for counting the number of whales andseabirds.
The number and the kind of whales sighted along l 70°W were demonstrated
in Fig. 6-1 along with the profile of the environmental factors. In general the dis-Fig. 6-1. Whales sighted and profile of the environmental factors along 170°W,
30°N-70°S during Nov. 22, 1968 to Jan. 19, 1969. Sp: sperm, B: blue, F: fin,
S: sei, D: small toothed, U: unidentified.

tribution of whales shows close relation to the bottom topography in the feeding
place (Nemoto, 1957; 1958), but the depth along the track covered by the R. V.
"Hakuho Maru" varied between 2,000 and 3,000 m, and possibly no influences on
the distribution of whales. It would be noticed in Fig. 6-1 that the distinct accumulations of whales were found in the south of 30°S especially in the Subantarctic region between 30°S and 50°S. A rather less number of sighted whales between 50°S
and 60°S was supposedly due to rough surface of the sea by stormy weather.
Sci. Rep. Whales Res. Inst.,

No. 26, 1974

FEEDING HABITS OF SEI Vl'HALE

63

An approximate physicochemical conditions in the Subantarctic waters along 170°W
were; 10°-20°C (temperature), 34.5-35.5%0 (salinity) and 0.25-0.5 µg-at/l(phosphate) and 5.5 ml/I (dissolved oxygen) respectively. On the charactersin chemical properties of the Subantarctic regions, Rochford (1961) demonstrated
35.4%0 of salinity and 0.2-0.4 µg-at/1 in phosphate as its indicators in the waters
off Western Australia, and he distinguished the water masses under the names of"south transitions zone". By taking these results into considerations it would benoticed that relatively denser consentration of whales are located not in the midstof the Subantarctic waters but in rather northerly located transition zone between

so·

40°

60°S

50°

40°

g
:5
c.

500

Q)

0

D. Oxygen (ml/ll

:5
c.
Q)

0

Phosphate-P(µg-at/l)

Silicate-Si(µg-at/ll

Nitrate-N(µg-at/ll

Fig. 6-2. Whales sighted and profile of the environmental factors along 155°E,
63°S-38°S during Jan. 23 to Feb. 1, 1969. Abbreviations of whale species are
as given in Fig. 6-1.

warm and cold waters. As clearly noticed in the distribution pattern of the environmental properties, those transition zone corresponds to the upwelling zone ofrich zooplankton standing stocks. In the south of 60°S, the proper of the Antarctic region, a great number of whales distribution was also found.
On the other hand in the Antarctic and the Tasman sea regions along 155°E
longitude, the whales were spotted only twice for sei and fin whales, which showeda poor distribution of whales in general (Fig. 6-2). The relationship between theSci. Rep. Whales Res. Inst.,
No. 26, 1974

KAWAMURA

64

distribution of whales and the environmental factors in this region was less clear
than those in l 70°W. However, relatively rich distribution of whales was foundin the Antarctic and Subantarctic waters, particularly in the transition zone ofnorthern waters.
Apart from the Antarctic regions it was note worthy that there were also distinct accumulations of whales in the region of equatorial divergence between 10°N
and l0°S, where a quite high concentrations of zooplanters were found (Fig. 6-3).
The zooplankton in this region would possibly be supported by the high primary
productivity due to upwelling (Nasu, 1972) which provides a quite rich accumulation of tuna (Sette, 1955 ). Although it is recognised in general that the baleen
whales do not feed much or entirely in the tropical seas (e.g. Mackintosh, 1965),
but those above mentioned results lead to a consideration that the whales would
potentially be in search of foodstuff even in those warmer waters.
-

400

:1=

:=:
----z, 300

c.

c

.8

"'"'

"''-'c

~

c

Cl

"'""
~

"' 200
g.

g

~

'-'
~

~ 100
;:

"'
:;::

0

0 ---'-~2~0°---'--;;;:30·0 N
0 ---'------;2~0°;---"~l~0~0 -~)-----;:0°0l~--;-;l0~0 -L----?::40~
0 -'----:C30~
70L0_S__,__~6~0°=----"~5~0~

1

)\~~

)I uJIU2~s1 )~

1

sp 1
)
lo30 s p1
SplU2 S2 Fl 01 020 01 S2 D2 050/ Sl 050
Spl Fl050 S4 01 Sp9
030
U2
Fl
05

1

I\

02
Bl 015 02
Sls~1 s~1

Fig. 6-3. Whales sighted and wet weight ofzooplankton in the upper 150 meter ofthe water column between 30°N and 70°S along l 70°W during Nov. 22, 1968 toJan. 19, 1969. Abbreviations of whale species are as given in Fig. 6-1.

Whales sighted at 40°,...., 50°S might have been on their migration toward south
since most of them were spotted in the early January. According to the catchrecords in the past 40 years (Omura, 1973), some individuals of the sei whale
spotted at higher latitudes in early summer are supposed to be as the stranger
from over wintered population.
In summerizing the above mentioned results both baleen and toothed whales
distribute in more favourable environments of the sea, where the feeding conditions
as having been indicated by the zooplankton abundance would be the most important role not only in the Antarctic region but also in the tropical seas.

Whaling ground of sei whale and the distribution of zooplankton
The whaling grounds of sei whale both in 1967 /68 and 1968/69 in the areas
V and VI of the Pacific sector were shown schematically in Fig. 6-4, and the dis6-2.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

65

tribution of food organisms found in the stomach of sei whale caught in the above
mentioned whaling grounds were demonstrated in Fig. 6-5. Black spots on themeridians of l 70°W and 155°E in the figures represents the oceanographic observation stations occupied by the R. V. "Hakuh6 Mam" during her 1968/69 cruise.
The track by the "Hakuh6 Mam" crossed over the whaling grounds although themain body of whaling ground in 1968 /69 season located somewhat eastward. The
mean position of both the Subantatctic and Antarctic Convergences are indicatedby the solid lines along with those observed by the R. V. "Hakuh6 Mam."

Fig. 6-4. Whaling grounds of sei whale in the Antarctic, Areas V and VI. Shadeby hatch indicates the region where the sei whale was heavily catched. Black
spot shows the position at which plankton sampling was made by the R. V. Hakuh6
Maru during her KH-68-4 Cruise in 1968/69. O.S.T.C., O.A.C.: Observed
positions of the Subtropical and Antarctic Convergence.

The whaling ground of sei whale in these regions is formed in the north of
the Subantarctic waters with its center along the Subtropical Convergence andits transition zone. These hydrological conditions do not differ much from thosein the Falkland region (area II) and the Indian sector (areas III and IV).
The food organisms which occur regularly in the whaling ground around New
Zealand are C. tonsus, Clausocalanus laticeps, E. vallentini, E. superba and P. gaudichaudii
among which E. superba is found only in the vicinity of Balleny Islands. This
species seems less important as sei whale food being compared with other foodspecies. Both E. vallentini and Clausocalanus laticeps as well as E. superba showed
local occurrence. In Fig. 6-5 it is considered that the whaling ground of theareas V and VI is largely formed solely by C. tonsus.
On the other hand the quantitative distributions of net zooplankton species
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

66

KAWAMURA

which were collected by the Norpac net at each stations were demonstrated in
Figs. 6-6 to 6-12. In Fig. 6-6 it was observed that the approximate number ofindividuals of C. tonsus population was 10 4 inds./1000 m 3 along the l 70°W whereas
it was 105 inds./1000 m 3 along 155°E. The figures of 104 - 105 inds./1000 m 3 ,can be considered quite distinct in abundance as the distribution density of copepods, and are still more higher density than that of C. tonsus in New Zealandwaters where they showed 0.52-83.5 inds./m3 (Jillett, 1968). The general features

Fig. 6-5. Distribution of the food of sei whale in the Areas V and VI, 1967/68.
O.S.T.C., O.A.C.: Observed positions of the Subtropical and Antarctic Convergences.

of the C. tonsus distribution in Fig. 6-6 correspond well to the characteristic distribution of whaling ground shifting rather northerly or southerly close to the
Antarctic Convergence at l 70°W and 155°E respectively.
C. simillimus was one of an important food plankton for sei whale in the Indian
sector of the area III, but none in the area V. A considerable number of species,
however, occurred in the net samples throughout the Subantarctic region with theindividual density of 103 - 105 inds./1000 m 3 or more (Fig. 6-7). The most C.
simillimus population occurred was represented by the copepodite stages II and III
along with adult forms while C. tonsus population was almost exclusively by the
copepodite V, that is, the food of sei whale. Accordingly, it would be possiblethat their life history differs each other. C. simillimus is generally recognized asSci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

67
170'W

I s

I

35·

Fig. 6-6. Quantitative distribution of Calanus
tonsus in the whaling area V, 1968/69. MPS TC:
Mean position of the Subtropical Convergence,
MPAC: Mean position of the Antarctic Convergence, OSTC: Observed position of the
Subtropical Convergence, OAC: Observed
position of the Antarctic Convergence. Copepodites under IV are shown by the hatch.

Fig. 6-7. Quantitative distribution of Calanus
simillimus in the whaling Area V, 1968/69.
Legends as in Fig. 6-6.

Fig. 6-8. Quantitative distribution of Clausocalanus laticeps in the whaling Area V, 1968/69.
Legends as in Fig. 6-6.

Fig. 6-9. Quantitative distribution of Calanus
propinquus in the whaling Area V, 1968/69.
Legends as in Fig. 6-6.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

68

KAWAMURA

the Subantarctic species (Hardy and Gunther, 1935, Vervoot, 1951, 1957; Tanaka,
1960; Brodskii, 1964), and the center of distribution in this species were foundrelatively in the southern waters than C. tonsus and does not occur in those transition zone proposed by Rochford (1962).
As it was described by Brodskii (1964), C. simillimus distributes in the waters
around the Antarctic Convergence being centered between 50°S and 60°S. It was
the Kerguelen-Crozet regions of 43° -50°S that C. simillimus occurred in the sei
whale stomach in late January to mid February. In the environs of Crozet Islands
where the surface sea temperature during December to January was 9.0-13.4°C,
C. tonsus occurred as food of sei whale and it was replaced with C. simillimus in thewaters of 5.0° -9.1°C. These facts lead to a consideration that C. tonsus would berather northern warm temperate species in contrast to C. simillimus. According to
Kawamura and Hoshiai (1969) the boundary at which the distributions of both
C. tonsus and C. simillimus replaced one to another was found at 45°S in the area
between Cape Town and the Showa Base in Antarctica. The surface sea temperature and the salinity at 45°S were 7.6°C and 34.07%0, respectively. Since C.
simillimus does not occur under the conditions of low salinity lower than 33.88%0,
it would hardly be possible that C. simillimus occurs as food of sei whale in the higher
latitudes south of 60°S. Accordingly, C. simillimus would be fed by the whale in
the waters of 45° -50°S where relatively warmer water prevails although its distribution is positioned still southward than the case in C. tonsus. Therefore, the distribution pattern of C. simillimus is considered to be somewhat similar to that of
between C. propinquus and Calanoides acutus.
As the season goes by the copepodites II and III population of C. simillimus inJanuary develops gradually to copepodites III to IV while C. tonsus population of
copepodite V migrates into deeper waters (Jillett, 1968), and the feeding place forsei whale being formed by this species diminishes gradually. Then C. simillimus
forms the feeding place following to C. tonsus but it is somewhat local phenomenon;
none of C. simillimus was fed by sei whale in the waters around 155°E while a considerable number of C. simillimus occurred in net samples.
It was 1967 /68 season that Clausocalanus laticeps was recorded first in the foodof sei whale (Kawamura, 1970a). This species, as shown in Fig. 6-5 was fed by
the whale in the same region as C. tonsus, and therefore this species as food of sei
whale has not such importance as to C. tonsus because of its quite local occurrence. However, C. laticeps population occurred under monospecific composition
with high population density, and was considered locally important foodstuff forsei whale. C. laticeps distributes in the vincinity of the Subtropical Convergence,a slightly northern species, and they occurred abundantly in the Pacific sector
proper than in the Tasman Sea region. Although this species distributes upto
far north off Australia along the 155°E meridian, the population density showed
5x 10 2 inds./1000 m 3 at most. So the biomass of this species in the sea might berather small due to its body length. As a food of sei whale C. laticeps occurred in
the waters around Antipodes Island, 50°S, l 75°W,....., 180°, and the distribution ofthis species agreed well with that obtained on the net plankton samples. ThereSci, Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

69

fore, it is supposed that C. laticeps forms dense swarms in the surface waters as wellas other food species. In the South African waters near Cape Province, Clausocalanus
arcuicornis was fed by sei whale (Best, 1967). It was proved by this facts that atleast genus Clausocalanus would swarm into the patches as well as Calanus species,
and formation of the patchiness would supposedly be the general distribution characters throughout the genus.
Both Calanus propinquus and Calanoides acutus have not been recorded as thefood of baleen whales in the food materials collected by the Japanese floating factories (Nemoto, 1959; 1962a; Kawamura, 1970a). However, Peters (1955) reported C. acutus as the food of sei whale during the German whaling operations in1930's, and later Pervushin (1968) described both C. propinquus and C. acutus as
the food of the baleen whales. According to Ottestad (1932; 1936), C. acutus andC. propinquus are typically endemic species of the Antarctic waters, and they occurred only within the colder regions in the south of the Antarctic ConvergenceFig. 6-10. Quantitative distribution of Calanoides acutus in the whaling Area V, 1968/69.
Legends as in Fig. 6-6.

Fig. 6-11. Quantitative distribution of Parathemisto gaudichaudii in the whaling Area V,
1968/69. Legends as in Fig. 6-6.

(Figs. 6-9 and 6-10). In many locations these two species occured being accompanied with Rhincalanus gigas or dense vegetation of diatoms. Comparing withboth species C. acutus was more dominant than C. propinquus but the former was
represented by younger individuals of copepodites II to IV. Since C. acutus andC. propinquus distribute with a little numbers in the far southern waters apart fromthe main whaling ground of sei whale, it would be quite possible that none of those
two species occur in the diet of sei whale. However, Pervushin (1968) reported
their occurrence in the stomach contents of sei whale in the area III of Crozet
Islands and its environs although the case might be quite extraordinal. By summerizing the results on the distribution of those two species along with those reported
Sci. Rep. Whales Res. Inst.,

No. 26, 1974

70

KAWAMURA

previously (Mackintosh, 1934, 193 7; Ottestad, 1932, 1936; Hardy and Gunther,
1935; Vervoot, 1951, 1957; Tanaka, 1960, 1964; Andrews, 1966; Kawamura andHoshiai, 1969), the northern most boundary in their distribution would on the whole
be somewhere between 50° and 60°S except the case in the Indian sector where it
was 47°43'S, at 76°48'E (Vervoot, 1957). It seems therefore curious that both
C. acutus and C. propinquus occurred as the food of sei whale in the Crozet Islands
regions since the feeding by whale itself essentially requires an abundant distribution so as to form the patches. In this respect both C. acutus and C. projJinquus may
possibly be fed to some extent by the baleen whales in some locally limited timeand place, but it may also be impossible them to form the staple feeding groundfor whales since those two species occur usually by accompanying the thick diatom
population of Thalassiothrix antarctica along with totally poor standing stocks
themselves.
Since P. gaudichaudii is provided the strong ability of swimming by its pleiopods(Kane, 1966; Nemoto and Yoo, 1970), many adult forms of this species would haveavoided from the net collection. P. gaudichaudii population occurred in net samplesof this study were excusively consisted of small immatured individuals ·with bodylength less than 10 mm. In the Subantarctic waters south of New Zealand Hurley(1961) and Kane (1962) made zooplankton collections, and found that amphipods
in those waters were mostly represented by the larval and immatured young individuals. Their net avoidance during net hauling would be obvious.
A relatively small number of P. gaudichaudii occurred regularly in the waters
between 50° and 60°S along 170°W, where the individual density showed about
10 2 inds./1000 m 3 whereas they showed much poorer but steady density throughout
the 155°E. It is supposed that the center of distribution would be around theAntarctic Convergence. The results obtained by Kane (1966) in the area III by
R.R.S. "Discovery II" and those by Hurley (1961) and Kane (1962) in the Pacificregion agree in general with the present study.
In the row materials of the stomach contents of sei whale the most individuals of P. gaudichaudii were represented by the large sized individuals of adultand possibly adolescent forms. This is largely different from the population obtained by the net. However, it was observed that the general characters of the
distribution in both populations do not differ much. So it could be said that noneof the habitat segrigations are possible in adult and young immature forms.
It has been reported that a little number of P. gaudichaudii occurred in thestomach contents of blue and fin whales as an admixture among E. superba population (Nemoto, 1959; 1963). However, the importance of P. gaudichaudii as foodof baleen whales is much increased along with the proportional increase of sei
whale in the total catches. In this respect P. gaudichaudii seems to be indispensable
food for sei whale especially in the Indian sector of the Antarctic (Table 5-4).
According to Nemoto (1959) the fin whale in the area V fed exclusively on E.
superba whereas the bulk of sei whale fed on P. gaudichaudii. Following to C.
tonsus, P. gaudichaudii as found in net samples distributed widely through the whaling
ground as shown in Fig. 6-5. Since the net avoidance by euphausiids as well as
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

71

P. gaudichaudii may also be possible as Fleminger and Clutter (1965) have discussed
on this matter, a quantitative treatments on the net samples in this study would
be difficult. Fig. 6-12 demonstrates the distribution of euphausiids species
occurred in the net samples. The populations of euphausiid were mostly consistedof young individuals of the furcilia stages, and a little number of adult forms. A
total of thirteen species of euphausiids was identified, but it was only two or three
species that were actually important as food of sei whale, i.e., E. superba, E. vallentini,and E. lucens. In contrast to euphausiid populations in the net samples, those fedby the whale were mostly represented by both adolescent and adult forms. The
furcilia and some corresponding individuals were consisted of many species, andtherefore, the distribution of furcilia of euphausiids does not seem to have any direct
relationship to the formation of feeding ground.

40'

45'

e Euphausiids(furcilia)~ Euphausia simillis var. armata
e E. simillis~E. lucens~E. vallentini~E. frigid a
Cl E. spinifera~E. sp.
~ E. superba@ Thysanoessa parva~Th. vicina®Th. macrura@ Th. gregaria@ Nematoscelis mega/ops

Fig. 6-12. Quantitative distribution of euphausiids in the whaling Area V, 1968/69.
Legends as in Fig. 6-6.

E. vallentini, the main euphausiid species occurred at 52°S and 54°S alongl 70°W longitude, and again at 51°S and 54°S along 155°E. Although the numberof individuals occurred was relatively small, the distribution pattern of E. vallentini
in both whales stomach and net samples agreed well in the region along l 70°W.
E. superba also shown a similar relationships. In Thysanoessa populations, Th.
macrura and Th. gregaria were distinct in their individual numbers. The former has
been reported as the food ofhumback and fin whales in the areas I and VI (Nemoto
and Nasu, 1958), and they (Nemoto and Nasu, 1958) suggested its importance as
whales food particularly in the region of higher latitudes. The occurrence of Th.
macrura in this study was recorded only in the south of 60°S, and this species may
possibly be less important for sei whale which is essentially considered to be copopoda feeder in the mid-latitudes. None of Th. macrura was fed by the sei whalein the areas V and VI.
The biomass of euphausiids in terms of the number of individuals in the area
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

KAWAMURA

72

V showed 103 -5X10 3 inds./1000 m 3 , and there were no notably distinct differenceswere found between local regions. As mentioned before the net avoidance byeuphausiids would be quite possible, and the euphausiids species as demonstrated inFig. 6-11 might have been entangled by reason of their dominancy among zooplankters under those circumstances. If so, E. vallentini could be considered tohave distributed abundantly in the southeast region off New Zealand, and in the
Tasman Sea region. Supposing these circumstances the feeding on E. vallentiniby the sei whale agrees with the general distribution patterns of E. vallentini.
In general the distribution of sei whaling ground can be seen as a function of
the characteristic distribution of food zooplankters, and these corelations weremore clearly observed in copepods. The organisms fed by the sei whale are represented by the patch forming species, and an agreement in the distributions
between zooplankton and whaling ground strongly suggests that those food organisms aggregate so as to form the patches to some extent at least in some local
reg10ns throughout their geographical distribution range.
7.

BODY SIZE OF CALANUS TONSUS

In the previous sections it has been discussed and proved that the zooplanktersand micronekton as food of baleen whales have to be maintained such high population density as to aggregate into patchiness. This conception would be well recognized by refering to some previous reports (e.g. Collett, 1886; 1911-12; Hinton,
1925; Mackintosh and Wheeler, 1929; Slepzov, 1955; Nemoto, 1957, 1959, 1962a,b; Marr, 1962; Mackintosh, 1973) although non-patch forming organisms would
be fed at times when the whales migrate into the region far outside from the socalled feeding ground such as the case in the South African waters.
In the course of microscopic observations on the food organisms some differences in the body size of C. tonsus population by the whaling areas were noticed.
C. tonsus, as has been described previously, is the most important foodstuff for thesouthern sei whale since it heavily aggregates in the surface waters during the firsthalf of whaling season. In this respect the composition of body size in C. tonsus by
the whaling areas was discussed in connection with its aggregating habits what itmeans ecologically.

7-1.

Composition of body size in C. tonsus population

The materials examined were the stomach contents of sei whales which werecaught in 1967 /68 and 1969/70 seasons. A total of 5,706 individuals of C. tonsus
was examined for this purpose, and the results were compiled by separating themonth into three decades (Table 7-1). However, the materials were only available during mid December to mid January since the whaling operation for baleen
whales is opened on 12th of December thereafter, and also the season for sei whaling
lasts for only a month and half to somewhere around mid January due to afading out of the feeding ground formed by C. tonsus.
As shown in Table 7-1 C. tonsus of copepodites IV-VI (female) occurred asSci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

73

food of sei whale. Since adult male of this species is usually said as to be mostly
in deeper waters (Jillett, 1968), they hardly occur in the surface swarms and consequently, in the population of sei whale food. The body size was measured
on the individuals being preserved in good conditions, and they were selected
randomly. Then the number of measured individuals through copepodites IVVI could be considered as to represent the composition of food C. tonsus population, and they are represented by the copepodite V stage, since it occupied for81.9.-98.4%, with the average of 89.7% in the whole of C. tonsus populations
examined.
TABLE 7-1. MONTHLY OCCURRENCE OF C. TONSUS BY THE STAGES IN TERMS OFPERCENTAGE FIGURES. THE ACTUAL NUMBER OF INDIVIDUALSEXAMINED IS INDICATED BY PARENTHESES.
Stage

Mid-Dec.

Late-Dec.

Early-Jan.

Mid-Jan.

Total

C IV
1.6 ( 24)
CV
81.9 (1222)
C VI Female 16.5 ( 247)0.83( 20)
88. 5 (2135)
10.67( 258)

1.73( 17)96.4 (956)1.87( 18)0.62( 5)98.4 (797)0.98( 7)

1.16( 66)
89.7 (5110)
9 .14 ( 530)

2413

991

809

5706

Total

1493

In 1967 /68 season the whaling was mostly operated in the areas III, IV andV, but the area shifted rather westward in 1969 /70 season and the areas II, III andIV were occupied. The composition of body size of C. tonsus along with the averageand the number of individuals were demonstrated by regions in Figs. 7-1 and 7-2,
since the overall sea conditions as the habitat of C. tonsus are possibly variable by
the sea regions (Hempel, 1968). The body size of each copepodite stages was:
2.7-3.0 mm in copepodite IV, 3.2-3.6 mm in copepodite V, and 3.7-4.0 mm
in adult female respectively. The composition of body size in copepodite V showeda normal distribution pattern with highest frequency of occurrence at the midstof distribution range through the materials obtained in Falkland region to the east
Indian sector region. In the general trends of the variation by the ocean sectors,
the distribution range of the body size class widened gradually in the direction
from the Atlantic sector toward the Pacific sector, though the most distinct example
was in the Western Australian region. The body size of 3.5-3.6 mm usually
showed high frequency of occurrence, but in the regions both south of Western
Australia and South Africa as indicated by the letter of, D, H, J, K, M and N,
the body size of high frequency was found between 3.0 and 3.2 mm. These kind
TABLE 7-2. AVERAGE SIZE OF C. TONSUS IN THREE DIFFERENT AREAS IN 1967/68
SEASON. NUMBER OF INDIVIDUALS EXAMINED IS GIVEN IN PARENTHESES.

~MonthArea~
Average size (mm)Sci. Rep. Whales Res. Inst.,.No. 26, 1974

Late-Dec.

Mid-Dec.
III, IV
66°-82°E
C IV
CV
C VI (52)3.46 (294)3.85 ( 76)v
l 72°E-163°W

IV
83°-10l 0 E

IV
82°-87°E

3,23 (111)3.38 (78)1)
2.80 (
3. 38 (1335)
3. 78 ( 110)

74

KAWAMURA

of difference as a biological character of each swarming C. tonsus populations suggests that they might come from a different population as the reproductive units.
The pattern of body size composition following to that of the normal distribution
lasts for a month or so without any changes within the composition. The femaleof copepodite VI is considered to follow the similar way as copepodite V although
the former is much variable than the latter due to its poor number of materials.
The high frequency of the occurence in the adult female was 4.0--4.2 mm and nodifferences in the body size compositions between the whaling areas were observed.
This may possibly be due to their biological character of stopping the feeding
activity in the copopodite VI stage as it has been known in Calanus plumchrus andC. cristatus (Minoda, 1971 ). In the populations in the Indian sector as indicatedby the letters of C and G, the body size of high frequency of occurrence was 3. 7,..,
3.8 mm. In general the composition of the body size in the adult female showed
the range between 3.4 and 4.8 mm, a rather wider range in the distributions thanthe case in copepodite V. The variations of this range was most distinct in the
Atlantic sector.
TABLE 7-3.

AVERAGE SIZE 'OF C. TONSUS IN THREE DIFFERENT AREAS IN 1969/70
Mid-Dec.

Month~--Area·~
Average size (mm)C IV
CVC VI (2)Average by month

C IV
CV
C VI (2)IV
109°-ll8°E

II
33°-43°WII
37°-53°WIV
l 10°-l 18°E

2.72(5)
3.13(21)4.00( 5)

2. 78( 2)3.44(23)
4.11(19)

3.56(4)4.21 (4)

2. 77 ( 9)3.19(31)4.01 (15)

2.75
3.38
4.11

Discussion
Jillett (1968) studied the seasonal distribution of C. tonsus in the waters off
Otago Peninsula, New Zealand, and found that the C. tonsus population in thesurface water during the summer was represented by the copepodite V stage. He(Jillett, 1968) also shown that C. tonsus, as a biological characters through Calanoida,has two generations annually, and that the copepodites from the second generation of current year mostly occupy the summer population, which must be the foodof sei whale in the northern Subantarctic waters. The life history of C. tonsus
suggests generally that the individual of the copepodite V from two different
generations coexists at least during December. One comes from over winterd
population and the other from developing population in current year. The coexistence of two size groups of copepodite V from different reproductive sources
has been known in C. finmarchicus in the North Atlantic waters (Stormer, 1929,
Barnes and Barnes, 1953; Colebrook, 1963), and Barnes and Barnes (1953) considered that the difference in size composition would be due to different populations,although there is a possibility of potential male and female.
7-2.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

s
10

'\

_:ctfl

N=294
3.46

N=294

~

'

N=l335
3.38

3.46

30

N=l31
3.13

2.82.93.03.13.23.33.43.53.63.73.83.9

8-

20

40

F'f

No:

50

l_Z511

II

2'

..

•

3.23.33.43.53.63.73.8

60
IV

Ill

v

g-ow~~~~~~60~~~~~~~~~-B88811~~~~p,!j~~~~~~~~~~~~~~~70~~~~~~~~~~~~~13~0~~~~~~~~~~~~~LATE-DEC. ~EARLY-JAN. 2j MID-JAN.
00 10MID-DEC.
20 30 40 50 %170W

Fig. 7-1. Size composition of Ca/anus tonsus copepodite V in the whaling areas and months in 1969/70
season. Average body length is given above each figures, and an approximate longitudinal range
from which samples were collected is shown by the capital A to K ..

s
10

,..
N=l32

N=29

4.11

~

20

'

JiWL

4.04

,.{'

30

3.85

3.63.73.83.94.04.14.24.34.44.54.64.74.8

4015161.n8 C4.o4.t4.14.3.4.4'J

Bj

I~

N~.lljl~OL''
4.0

IP

~

50
0

3.43..53.63.73.83..94.04.14.1

.

"'

v

60
170W

Fig. 7-2. Size composition of Calanus tonsus copepodite VI (female) in the whaling areas and months
in 1969/70 season. Average body length is given above each figures, and an approximate longitudinalrange from which samples were collected is shown by the capital A to K.

FEEDING HABITS OF SEI WHALE

75

In this respects the differences in size composition of C. tonsus especially inthe copepodite V stage suggest that they should come from the different reproductive populations. It is also suggested as a whole that those different size compositions which are the distinct biological character not as individuals but as the population, would be the result of having been isolated each other. A quite few occurrence of adult male in the surface population of C. tonsus is similar to the results
by Jillett (1968). Those male occurred sporadically must be newly developed
individuals in the current season, which made Jillett (1968) consider a possibility
that the second generation would supposedly be due to a result by the parthenogenesis in the over wintered females. The small sized female populations found in the
Indian Ocean sector are considered to be the result of different environmental
conditions there, or of a complete isolation from the others. It is known in the
British waters that a local difference in environmental conditions influences on
the size of individuals which form a dominant population in those regions (Marshalland Orr, 1955). The geographical difference in body size in the Antarctic copepods also well known (e.g. Brodskii, 1964). Baker (1954) considered that many
SEASON.

NUMBER OF INDIVIDUALS EXAMINED IS GIVEN IN PARENTHESES.

Late-Dec.

Early-Jan.

Mid-Jan.

IIII

8°-46°W

36°-54WIV
99°-ll0°EIII
0°-l9°E

II
40°-51°WIV
90°-100°E

III
19°-27°E

II
14°.-52W

3.46(10)4.04( 8)2.60( 1)3.38(31)
4,23(16)2.50( 1)
3.20(23)
3.95( 7)2.89( 1)
3.18(11)
4.23( 3)3. 00 (2)3.48(5)4.30(2)

3.21 (13)2.91(3)3.13(6)2.80( 1)3.49(10)
4 .03( 3)

2.69
3.34
4.09

2.83
3.29
4.16

2.86
3.28
4.03

zooplankters would originate from the identical populations of species by species
since they show rather monotonous circumpolar distributions. However, as
Brodskii (1964) having been demonstrated in C. tonsus and other copepod species,
there is a distinct geographical differences in the composition of body size as the
local populations, and I have also shown these circumstances in the previous section of this report. Mackintosh in his recent report clearly shown that there should
be several number of distribution centers under quite high population density inE. superba while it shows a typical circumpolar distributions (Mackintosh, 1973).
The above mentioned facts indicate that the zooplankton in the Antarctic waters
distributes quite unevenly under the general circumstances of circumpolar distributions, and that their occurrence with different body size compositions invarious sea regions would perhaps belong to different reproductive populations
somewhat likely to a "stock unit ".
The largest and the smallest body sizes in female C. tonsus measured in thisstudy were 4.8 mm and 3.6 mm respectively, while the former by Brodskii (1964)
was 4.25 mm (female) and 3.40 mm (male). Although it is known that the bodysize both in copepodites V and VI (female) shows latitudinal variations as a whole,Sci. Rep. Whales Res. Inst.,
No. 26, 1974

KAWAMURA76

the body size seems to differ to some extent between the individuals from sei whale
food which have had been formed the patchiness and those taken by the net haul
which must supposedly been in a sporadic distribution without forming the patchiness.

7-3.

Patchiness of C. tonsus and the density effects
The body size of C. tonsus in Table 7-4 was based on the row materials whichwere collected by the net haul along with many other zooplankters. On the other
hand, C. tonsus being fed by the sei whale as has given in Tables 5-2 and 5-3, occurred as mono specific composition, which suggests that C. tonsus populatfon as
whales food might possibly have been in an aggregation, to show the patchiness.
Both C. tonsus populations, mentioned above therefore, can be considered to beecologically unidentical to show some differences in the size composition and theaveraged body size. The food C. tonsus population seems rather larger if not entirely in the body size of individuals.
TABLE 7-4. BODY SIZE OF THE SOUTHERN SPECIES, CALANUS TONSUSBRADY REPORTED PREVIOUSLY BY THE DIFFERENT WORKERS.
AuthorCV

CVI (~)CVI (d')Brodskii ( 1964) *Tanaka (1956)

3.40-4.25
4.07-4.24**
3.66-3. 75***

3.30-4.15

3.27-3.47

Tanaka (1960)
Vervoot (1957)

3.39-3.69
3.69-4.05* 3. 71 mm on an average.
** Sjze at higher latjtudes.
*** Size at lower latitudes.

The patchiness of zooplankton has been observed but a little. Studying on
the food of blue and fin whales in the South Georgian waters, Mackintosh andWheeler (1929) stated that E. superba occurs by a monotonous composition ofsame year class or same developmental stages since the species forms such patchinessseparately as to be fed by the whales. Hardy and Gunther (1935), and Mackintosh(1966) reported the results of their observations on the behavior of E. superba underpatchy aggregations in Cumberland Bay, South Georgia, and described as "Thereappeared some guiding ' principle '-almost as if there was some leader in commandof the whole! " (Hardy and Gunther, 1935). Mackintosh (1966) also describedlater that the patches of E. superba moved in a cluster as if they were an amoeba
like organisms as a whole, and the patch was quickly reorganized within tens seconds
after disturbance. These characters of E. superba patches as a kind of animal
aggregations strongly suggest their something socialized structure within the patches
as the theme having been suggested also by Clutter (1969) in Mysidacea. In general
the features of the plankton patches can be comparable though not analogous withthe aggregations in the insects such as the reproductive aggregation by male mosquitoes (Kawamura, 197lc). An ecological homology in a plankton 'patchinessSci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

77

could be imagined by the fact that the empty shells of E. superba were collected
abundantly in a net haul (Marr, 1962). This indicates that the development of
the individuals proceeds simultaneously among almost all members of the patches.
The patchiness of zooplankton can be considered as one of the distinct characters in the distribution of animals. Difference in generations could be responsible
for variable body size composition but on the otherhand it should be consideredthat there must supposedly be some ecological benefits for aggregating into patches
through the density effect. For example, it is well known fact in aggregatinginsects that the population density closely related to their relative growth rate
(e.g. Ishida, 1952; Uchida, 1952; Fujita and Uchida, 1952; Takahashi, 1956),
in which the density effect would role positively (Chauvin, 1962). In the population of cockroach, Blatella germanica the overall growth rate as the unit of population is more enforced quickly by keeping close the intervals between individuals(Ito, 1959; Ishii, 1970). This kind of function by the density effects have also
been indicated in Mysidacea population (Clutter, 1969). In the zooplakton population under aggregations, the population density is usually kept quite
high; E. superba shows one individual per cubic inch (Marr, 1962), and he described them as "jostling one another" under patchiness. Swarming E. pacifica
shows 1-2 cm of intervals between individuals (Komaki, 1967). These facts leads
to a supposition of tactile stimuli, that is, touching each other by the body or by theantennules would possibly occur to some extent during their swimming (Kawamura,
197lc). The differences in body size composition in C. tonsus populations could
be explained by this kind of density effect through their social behavior, but thescheme will be discussed more in section 11 where the C. tonsus patches were treatedon the basis of field observations and row materials obtained by net haul.
8.

FEEDING APPARATUS OF SEI WHALE

A quite characteristic adaptation in baleen whales is their specialized feeding apparatus to collect a bulk of zooplankton and some micronektons. The baleen plates
or whalebone as feeding apparatus has developed in various ways by species inplace of the tooth, and no similar feeding structures are found in any of other kindof animals. The baleen plates being arranged in a row on the upper mandible
are quite functional for gathering rather scattered foodstuff along with the specialization of oesophagus to form the first stomach which functions as a depositing sac
for swallowed foodstuff (Hosokawa and Kamiya, 1971). In this respects a row ofbaleen plates is indispensable apparatus for the baleen whales actually functions
whereas the teeth are not so functional in many toothed whales. When they werelost or heavily damaged by some desease or by an accident, a daily nutritional
requirements would hardly be filled. Rice (1961, 1969) reported the rudimentarybaleen plates in sei whale due to some microbial desease, and it caused the blubberof the whale quite thin from the insufficient food intake.
The amount of stomach contents under full repletion closely related to feeding habits of whales and to the population density of the food organisms, say, theSci. Rep. Whales Res. Inst.,.No. 26, 1974

78

KAWAMURA

patchiness of zooplankton. Since the patchiness of food zooplankton hardly be
studied by the net haul as has been pointed out by Mackintosh (1966), one of an
approaches to studying the plankton patchiness would be found in the stomach
contents of baleen whales. In this point of views Klumov (1961), Kawamura(1970b, 197lb), and Omori et al., (1972) reported on the population density of foodorganisms being based on the stomach contents of whales, and found a hardly believable high population density of zooplankton under the patchiness, which would
never be obtained or known by the net haul investigations. In regard to thiscircumstances it would be necessary to know the ability in filtering the water by
a row of baleen plates in sei whale.

Oral cavity
A row of baleen plates furnished on the upper mandible functions in collecting
the food organisms. This would be fairly comparable character with the sperm
whale whose lower jaw is fully functional against the upper jaw. The baleen plates
however would be functional actually with the supplemental aid by the lip on
lower mandible. After Ingebrigstsen's suggestion on the feeding habits in baleen
whales, Nemoto (1959) described on this scheme under three different feeding
types of baleen whales: swallowing or gulping type, skimming type, and the combined both swallowing and skimming. Then the shape of the lip which is characteristic by species closely related to the feeding type above mentioned. Both right andbowhead whales are furnished with so largely developed lips which are indispensablefor their feeding by skimming off the food contained water continuously, while
8-1.

160

E

~
3:

150

.~ 140-~0130
0:5 120Male
Females 12m;;::: + 12m:;:::• 13m
c, 13m
• 14m
o 14m
o
o
.,
0
0
• 15m
o 15m •"'~ 0 "0"' 16m:o;: 0 16m:o;:•o ~a rn.fo'da:O. oi:ia"" 0
& n
.-i..
121
... • c::r • <1
ocs;0 l:l:J ~ D D tl
D00•
.P~~,6ii ~ dl"~o~•o
.A.

"ji;

E

~ • .loDo,"s110·~ 100 «leE~::;;; 90"

..
260

~.<J

¥. '1' :<:'l:, ~~' ~~ '~o

,.+

<>

~,..,,OD0.a.•a•AM.:o""" M"C'""\1f•)o.oli9i>"~z. ot:..t~i ·£:..··A<i<;l,o0"

IZllZI

~

a.

"

e+c.

•t:.

~+"
280

340
320
300
Length of palatal ridge (cm)

360

380

400

Fig. 8-1. Relationship between the length of upper jaw and the maximum widthof lower jaw in sei whale.

balaenopterid whales are furnished with the poorly developed lip since they collect thethe foodstuff by swallowing the water although the lip of sei whale relatively welldeveloped among them. In California grey whale, the benthos feeder (Rice andWholman, 1971), the lip is rather poorly developed. It is worth taking into account that the sei whale follows after both feeding types according to the conditions of the distribution of food organisms.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SE! WHALE

79

In this respect the size of both upper and lower jaws were measured in connection with the potential ability in collecting the foodstuff. The relationships
between the sizes of upper and lower jaws against the body length of whales aredemonstrated in Figs. 8-1 and 8-2. The size of oral cavity varied to some extent
among the individuals examined, but it grows larger and larger in accordance withthe growth in body length. Dominacy of the female in the size oflarger than 330 cm
of upper jaw in sei whale and also 470 cm in fin whale is due to their biologicalcharacter that the female grows much larger than the male, and the former is preferably caught largely than the latter. In bryde's and minke whales the proportional length of the skull is larger in the female than the male (Omura, 1966;
Ohsumi et al., 1970). The sei whale which closely relates taxonomically to bryde's
whale showed considerable variations in the maximum width of lower jaw against
a definit length of the upper jaw, and in a definit width oflower jaw against the upper jaw length. The variations were more distinct in the latter. These variations
relating to the size of oral cavity along with the number of baleen plates indicate
a manifold character of baleen whales in their feeding mechanisms and in theability of collecting the foodstuff.

§ 220

Male

210

... 19mi:;; 200
;<

E

190

Ell

Female

18m~

• 20m
2lm

•
WI

22m~

+

18m~

6
0
D

19m
20m
2lm

0

22m~

0

...
0

"

:g
;< 170

...

E
§ 160

"'
><

360

+

"

t

::E 150

380., ~" o•o•E" .
0...... •... 6: ~:5 180

0

4 00

04

+6

0

6

8

4

0

0

0

I!

...

0

rn

00

oo 0

"'"

Jl, 0

0

D
0

'<lo

•

"'=
•

"" "

"

"
"s'"

" "'
0

"

"'

"' "
"'

•
400

480
460
440
420
Length of palatal ridge (cm)

500

520

Fig. 8-2. Relationship between the length of upper jaw and the maximun widthof lower jaw in fin whale.

8-2. Baleen plates
The number of the baleen plates in sei whale varies somewhere between 300
and 350 plates on one side, and two folds of this number of baleen plates functions
actually for collecting the food. However, the number of baleen plates varies by
the individuals and also by the observer (Williamson, 1973), since they are deformed
into a kind of hair-like bristles near at the tip ofrostrum and are randomly arranged.
The density of the baleen plates furnished in a row varies with the positions of themouth (Fig. 8-3, Table 8-1 ). The baleen plates (=bristles or hair) near the rostrum
were counted 1.4 plates/cm on average while they were 0.93 plates/cm at theirmaximum length as indicated by the arrow in Fig. 8-3, and they again showed ahigh density in the posterior part close to the angle of gape.
The relative ability in filtering the water per unit area of the inner surface
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

KAWAMURA

80of the apparatus is a function of meshes formed by the woven bristles. The meshes
are kept so as to show a definite filtering ability at any part of the apparatus,
since the overall ability for retaining the foodstuff might greately reduced if thefiltering ability was randomly variable by the part of the apparatus due to different
mesh sizes in its inner surface.
45

E

No. of baleen plates
286+18* /262 cm
14.1 m, Male

<..)

C>
M

•

>.

~ 40
Q)

Q)

0.

12 -

2"'

c.
"'
c:
Q)
Q)

E

10 .§.

35

"'
Q)

s%
6 "*

'°
..Q

c:
Q)

..Q

Q)

~
,, 30
z

4 "15

'°
22!
.5
>

i

2 5 LL-2L0-'--4k0-'-'60--1-~80--1-~10~0Ll~2~0Ll~4~0~1~60;:-'-;1~80;--'-;;2~00:-"-;;-22~0~24~0~
Distance from the anterior end of baleen row (cm)Fig. 8-3. Variation of the number of baleen plates in sei whale. Arrow shows the
spot where maximum length of baleen plates was found. (*bristles)
TABLE 8-1.

INTERVALS OF EACH BALEEN PLATES AT THEIR MAXIMUMLENGTH IN THE NOR TH PACIFIC SEI WHALES.

Body length
(m)

Sex

Interval(mm)

Thickness ofbaleen plate(mm)

Room between
baleen plate
(mm)

11.6
12.3
13.2
14.1
14.3
14.4

M
M
M
M
F
F

9.20
9.78
11.60
11.11
9.29*
9.40

2.2
2.2
2.15
2.2
1. 7*
2.5

7.0
7.56
9.45
8.91
7.59*
6.90

* Measurement on dried material.

The length of each baleen plates is usually measured along their outer margin
but it is the length along the inner margin to the base of palatal ridge that actuallyaffects on the total surface area of the filtering apparatus. As shown in Fig. 8-4
the unfolded shape of filtering apparatus varied by the animals along with their bodylength as a whole. Although the animals examined in Fig. 8-4 were caught inthe coastal waters of Japan, those unfolded shape is considered to be the same withthe animals throughout the oceans. The position of the maximum width does notcoinside with the position of the maximum length of baleen plates, but is found at
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

81

rather posteriorly of about 66.4 ....... 69.5 % in the total baleen row length, at which thehighest part of the lips oflower jaw is positioned. These general arrangement seems
as a whole to function effectively in collecting the foodstuff as much as possible
particularly when the whale feeds by skimming the food contained water with its
mouth half opened.
90~'E 80E~ 7o""'51 60~-E. 50'"'g 40
S? .c
7J 30

Minke
6.2m Male

~20
-0 0

2 t

5 ~

10

0'----2L0~4L0~6L0_·---1.80~1~0-0--'12-0~14L0~16~0-.-1~80~2~00~2~20'--'--24L0~26~0_,__28L0~3~00

Length along palatal ridge (cm}Fig. 8-4.

Unfolded figures of the filtering apparatus ofsei and minke whales.

8-3. Bristles on baleen plates
The bristles furnished on the inner margin of baleen plates form the fine meshedstructure as demonstrated in Plate I, and actually retains the foodstuff which havebeen skimmed off. The inner margin of the baleen plates is furnished with thebristles (Plate I, fig. 1 ), and the whole surface of filtering apparatus is covered bythis meshes although the number of bristles are considerably reduced at the tipof baleen plates (Plate II, fig. 1). Ruud (1940, 1945) examined the baleen plates
+-+
0%

t.-t.

0--0

--

25%

50%

75%

~ . . . . . .,.t_- -:~: . :.,i:6: .: ,:3c: : .m_ _: _ _u_

Lo: 54cm.-.._

Baleen plates

50

"'~~
0

U)

"'

40

~~

:g ;; 30
~~
-0 .c
"'

20
1:'>c: 0g~~~ 10. ___-+, ---------0
2

.4

12

14

16

18

20

Length of baleen bristles (cm)Fig. 8-5. Composition of the length of baleen bristles in 14.3 m sei whale caught
in the North Pacific in 1968.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

KAWAMURA

82

TABLE 8-2.

Location of catch
N. PacificJapan, coastal (off Kinkazan)"

Body length
(m)

14.3
13.5
12.3
11.6

MEASUREMENTS ON THE BALEEN

Sex

F
M
M
M

Length ofbaleen plates*

Lo/Li

~

Lo

Li

54.0
42.5
43.0
44.0

63.0
54.0
52.0
53.0

1.17
1.27
1.21
l. 21

* Length along outer edge of baleen plates (Lo), and those along inner edge (Li).
** Diameters of baleen bristles measured at the base (Db), middle (Dm), and at the tip (Dt).

of fin whale in detail and described that they are made of chitinous tissue which
is somewhat likely to a kind of fused bandage of many bristles. So the diameterof the birstles do not differ between wet and dried materials.
The length of the bristles varies with the part on the inner margin. Fig. 8-5
shows the frequency of occurrence in the bristles length in a sei whale of 14.3 m,
and the actual figures were given in Table 8-2. The number and the lengthcomposition of the bristles per unit length along the inner margin showed that
relatively longer lengthed bristles were poorly found. The length of the bristles
was measured at four parts, and was found that 3,....,5 cm long bristles were mostdominantly furnished. Accordingly the meshes in the surface of the filtering apparatus are chiefly formed with these length of bristles. It is clearly noticed thatthe length of the bristles did not show characteristic differences at any part of theinner margin. These suggest that the filtering ability in sei whale would be thesame at any part of the apparatus.
Table 8-2 represents relative abundance of the baleen bristles, their lengthand diameter. Although the triangle shaped baleen plates are well known, thelength along the inner margin of baleen plates is longer about 1.2 times than theoutside so as to form relatively larger surface of filtering area. The distribution
density of the bristles was 50 bristles /cm with the average of 45.5 bristles /cm, and thisdensity does not vary with the sex and the body length of whales. The shape of abristle itself seems rather slightly tapered: the diameter is larger at its base than
the tip. However the variation in diameter is such slight as to make them represent
the mean diameter at the mid point of the bristles.

Area of filtering apparatus
The total inner surface area of the filtering apparatus in five animals of different body lenth was measured from the unfolded figures as shown in Fig. 8-4,
and the results were given in Table 8-3. However, the filtering area given in
Table 8-3 is approximate figures, since an overall shape of the filtering apparatus shows a quite complexed features by the curved surface.
The surface area of the filtering apparatus was 2.37 m 2 in 11.0 m individual
and was 3.59 m 2 in 14.4 m individual. Then those areas seem to increase after ageometrical progression (Fig. 8-6). However, it is clearly observed that the surface
8-4.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

83

PLATES AND BRISTLES OF SEI WHALES.
No. of baleen bristles/cm
75%
44

Average length of bristles (cm)Average diameter ofbaleen bristles (µ)**

50%

25%

0%

75%

50%

25%

0%

Db

Dm

Dt

49

63

36

5.6

6.1

5.2

6.4

250
168
155
157

167
108
114
114

141
106
93
85

4.2
4.4
4.6

54
37
42

TABLE 8-3. AREA OF FILTERING APPARATUS OF SEI AND MINKE WHALESCAUGHT IN THE COASTAL WATERS OF JAPAN, MAY, 1971.
Species
of
whale

Body
length
(m)

Sex

Lk*
(cm)

Ld*
(cm)

Sei
Sei
Sei
Sei
Sei
Minke

11.6
12.3
13.2
14.1
14.4
6.2

M
M
M
M
F
M

268
236

256
228
271
262
300
102

Area of filtering
Length alongouter edge of apparatus combined
both sides
baleen plates
(m•)
(cm)
2.37
2.13
2.64
2.89
3.59
0.29

291
261
330
300
330
114

* Length of a row of baleen plates along the upper jaw.
** Strait length from the anterior end of baleen plates to the posterior end of them.
6.0
oEg• Kawamura (Present study)+ Williamson (1970)

5.0

0Nemoto (1970)
0

Bm
4.0

~ 3.0
"'"'

~

Bm Blue
Bp FinBe Bryde's
Bb Sei
Eg Right
Mn Humpback
Ba Minke

2.0
oBe

10

~
Ba
10

Fig. 8-6.

15
Body length (m)2025Area of filtering apparatus in baleen whales.

area of :filtering apparatus in sei whale is considerably larger m contrast to thebody length of animals. These sei whale's characteristics are quite interesting when
we compare the feeding habits of both sei and right whales with those of anotherbalaenopterid whales: the former two feed after skimming type with well developed
Sci. Rep. Whales Res. Inst.,.No. 26, 1974

84

KAWAMURA

filtering apparatus while the latter feed after swallowing type with poorly developed
apparatus. The area of filtering apparatus in sei whale showed moderate figures
between right whale and another balaenopterid whales. This fact will be reasonably
recogniged by supposing that the sei whale feed after the types of both skimmingand swallowing. In balaenopterid whales other than sei whale on the other
hand, the area of filtering apparatus changed rather linearly against the bodylength. In regard to these above mentioned facts it could possibly be consideredthat the feeding ability of the baleen whales would develop after geometrical progression since the body weight of whales is porportional to cube root of the bodylength (Nishiwaki, 1950) whereas the food requirement in terms of the daily ration
is linearly proportional to the body weight (Sergeant, 1969, Table 4).
9.

FILTERING ABILITY IN THE ROW OF BALEEN PLATESIn any types offeeding method the food contained water is pushed outside by the current pressure or by the co-operated functions of oral cavity, ventral grooves, andtongue. In sei whale as mentioned before the foodstuff is collected chiefly byskimming the food contained waters, and the filtering ability in the feeding apparatus may greatly affects on the overall ability for sieving the foodstuff.

Porosity in the meshes of filtering apparatus of sei whale

9-1.

The porosity, the mesh openings in filtering apparatus in terms of percentages
was calculated, and the figures were given in Table 9-1 along with those known
TABLE 9-1. POROSITY OF FILTERING APPARATUS OF SEI WHALE, WHICH IS
FORMED BY THE BALEEN BRISTLES. (MEASUREMENTS AT THE MAXIMUMLENGTH OF BALEEN PLATES AND THOSE AT THE MIDDLE PART OF
THE BALEEN PLATES ALONG INNER MARGIN).
Body
length(m)

Sex

Location ofcatch

11.6 M Japan coastal
12.3 M
13.5 M"
14.3** F N. Pacific pelagic

Porosity (%)
Total
Interval.Mean
length of of baleen dram.eter
bristles Possible thickness of filtering apparatus (mm)baleen1 t es ofbristlesPa
at Dm***
(mm)
(mm)
(mm)
2
3
4
5
1
1942
1111
2285
3000

9.20
9.78
11. 60*
9.29

0.114
0.114
0.108
0.167

72.6
81.97
77.0
1.0

86.3
90.98
88.5
55.0

90.87
93.99
92.33
70.00

77.5

82.0

* Measurement from 13.2 m, male.
** Measurements on the dried material.
*** Measurements at the middle part of baleen bristles.

in the bolting silk cloth for the comparison. The netting of the filtering apparatus
in baleen whales is structured by the following elements: the intervals between
each baleen plates (Fig. 8-3), the thickness of bristles in diameter, and the lengthof the bristles. As the measurements of these elements were given in previous
section, the calculation was made by using them (Table 9-1). Since the meshedfiltering apparatus in whales is formed with some thickness due to entangled bristles,
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

85

five cases of the thickness between 1.0 and 5.0 mm were supposed for the calculation. In sei whale, however, the actual thickness is considered about 1.0.-2.0mm(Plate I, fig. 4 and Plate II, fig. 2). The above mentioned thickness along with theintervals increase thicker and wider with the increase in body length although thelength of the bristles also grow longer.
The porosity which is usually examined in bolting silk cloth for plankton net(e.g. Anraku and Azeta, 1966) varied between 77.2% and 88.6% by the bodylength of sei whale concerned. Since the baleen plates and the bristles examined
were damaged to some extent due to ill treatment, the actual figures of the porosity
would be slightly more lower values. However it is note worthy that the overall
figures of the porosity do not seem to vary with the body length, say, the porosity
is nearly constant regardless the body length of whales.
By comparing the porosity in ballen plates with that in plankton net, the former
showed distinctly larger percentages than the latter (Plate II, fig. 2).
TABLE 9-2. POROSITIES OF JAPAN BOLTING SILK CLOTH
COMMONLY USED IN PLANKTON COLLECTION.
Kind of bolting cloth

Mesh aperture (mm)Open area* (%)

0.094
0.193
0.334
0.630
0.926
0.350

23.0
40.0
46.0
58.0
60.0
38.0
50.0**

xx 13
xx 7
GG 54
GG 32
GG 20
Pylen #60
Larva net (Cremona+Pylen #60)

* Data by the Nippon Bolting Cloth Co., Ltd. (S. Ueno pers. corn.).
** Anraku and Azeta (1966).

Relative filtering ability in a row of baleen plates
In order to know an actual filtering ability in a row of baleen plates, thefiltering ratio was measured experimentary after the similar ways employed inplankton net. The experiment was conducted at the offshore region in Suruga Bay
on boad of the R. V. "Tansei Maru" of the Ocean Research Institute, Universityof Tokyo. The general arrangements of the experimental instrument are shown in
Plate III. The dimensions of the instruments were 48.6x23.4x91.0 cm. A fl.owmeter was mounted on the inside of the instrument at about 1/3 distance posteriorly
from the mouth opening. A row of baleen plates was mounted on the bottom of the
instrument (Plate III, fig. 2). The slits between the mounted baleen plates andthe instruments, which may cause a leakage were filled with 5.0 cm thick of uretan
foam (Plate III, figs. 1 and 2). The surface of the filtering apparatus throughwater passed away in the experiment had an area of about 23.4 X 54.0 cm. The
two 10.0 kg of lead weights were mounted on the both outsides of the instrument,
which was towed by bridle. Before experiment a filter made 'of bolting silk cloth
GG 32 (0.63 mm mesh opening, 58% in porosity) was attached on the mouth of
the instrument so as to reduce the volume of passing water down to about 1 /3.
9-2.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

KAWAMURA

86

By this treatment the water entered into the instrument was well filtered off withoutcausing any overflowing. The experiment was conducted in Suruga Bay when thedepth was 426 m by towing the instrument vertically from 200 m to the surface
at the speed of 1.-1.2 m/second. The volume of water filtered by the row ofbaleen plates was calculated by the flow-meter's readings.
The results were given in Table 9-3. The relative filtering ability in baleen
plates of both sei and fin whales showed rather poor when compared with those in
the bolting silk cloth: the ability in sei whale was approximately 1 /8 of GG 54(0.33 mm mesh openings) while the fin whales' was 1 /5, and still more, it may beinteresting that those relative ability was poorer than the finely meshed XX 13
bolting silk cloth which can retain most of the representative diatoms in the sea.
From this experiments it can be safely stated that the filtering ability in sei and fin
whales, and possibly in any baleen whales is astonishingly poor than those in thebolting silk cloth. The filtering ability might reduced to some extent by ill treatment in mounting the row of baleen plates on the instrument, and even we takethese circumstances into account the results of 1 /5-1 /8 against the bolting silk
cloth are astonishing enough, that is, the filtering apparatus of baleen whales
TABLE 9-3. FILTERING ABILITY OF THE BALEEN PLATES IN SEI AND FIN
WHALES AND THOSE OF JAPAN BOLTING SILK CLOTH.
Exp.
No.
2
3
4
5
6

Item

No. of flow-meter
revolution/200 m

Relative
ability

Calibration
GG 32
GG 32+GG 54
GG 32+XX 13
GG 32+Sei*
GG 32+.Fin**

1842
610
893
648
105
184

17.55
5.81
8.50
6.18
1.0
I. 75

* 14.3m., female, caught in the North Pacific on July 18, 1969 at 45°-04 1 N, 171°-37 1 W.
** 16.8 m., female, caught in the North Pacific on August I, 1969 at 47°-55 1 N, 157°-10' W.

never exceeds in the ability of filtering off the water than in the plankton net.
These results give us some fundamentally important evidences concerningon the scheme of food and feeding habits in baleen whales: that is, there have been
two suppositions in connection with the population density of food organisms andthe amount of stomach contents acutually found (Klumov, 1961; Kawamura,1970b). They are: 1) the daily rations of baleen whales would be filled by their
extraordinal ability in collecting the foodstuff, and the ability have to be maintained
under a quite excellent functions, or 2) the food organisms have to distribute withvery high population density of such extent as hardly impossible to know it bymeans of an ordinal method being employed in plankton samplings by the net.
Those above mentioned results lead to a consideration that the food organisms
would distribute under a quite dense population in the sea to fill the daily food requirements of whales rather easily by those poorly developed filtering ability inthe row of baleen plates.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

10.

87

AMOUNT OF THE STOMACH CONTENTS AND THE POPULATIONDENSITY OF FOOD ORGANISMS

The amount of the stomach contents in three species of the baleen whales has beenreported previously though it was rather preliminary (Kawamura, 1968b, 1970a).
The predator-prey relationships which involve the baleen whales would be a characteristic scheme in the food chains of the sea, since the secondary producer are
directly connected with the consumers of the highest level in the ecological niche,that is, the energy flows quite effectively in the economy of the sea. Klumov (1961)
made a calculation and described theoretical population density of zooplanktonbasing on the amount of stomach contents which were actually measured, and heconcluded that the food requirement by the whale would hardly be filled fully withthe population density of zooplankton being widely found in the sea. After thescheme of Ivlev's "feeding rate" (lvlev, 1961), Sergeant (1969) confirmed on thedaily ammount of food consumed by the whales which has been reported previously
would be an appropriate figures, and Kawamura (1970b; 197lb) has discussed on
the population density of copepod, Calanus tonsus in relation to the amount of thisfood organism in the first stomach of southern sei whale. Prior to further examination on the population density of food zooplankton, the feeding habits such as
feeding cycle, feeding method, amount of stomach contents, speed in digestion, were
examined.
Most of whales usually spotted in the whaling ground are considered to beunder the movements in search of food, and such whales as being under feeding
activity in high seas are rarely sighted even by the whalers who had been engaged
in whaling for many years. These fact indicates that the whales feed intermittently within rather shorter hours. Under these circumstances the observations
by Ingebrigtsen (1929) on the feeding behavior in North Atlantic sei whale must be
an important. According to Ingebrigtsen's observations the sei whale under feeding shows rather dull and only pays a little attention to the surroundings. Farlater, Gunther (1949) reported a similar aspects in the southern fin whale, in whichhe (Gunther, 1949) described that the fin whale continued its feeding without
paying any attention to the approaching ship and was easily marked. The whales
fully repleted with food also show a similar behavior. When they are under starvation, however, they are quite shy and agile, and can hardly be approached within
the shooting distance. The sei whale quickly moves around in the surface withits mouth half opened when they are under feeding (Ingebrigtsen, 1929; Scoresby,
1820; Kawamura, 1972), and it is this occasion that bolting behavior was observed(Andrews, 1909; Gunther, 1949) though the whale sometimes feeds without bolting
its body (Millais, 1904-1906). In humpback whale it is also known that the whale
makes its food organisms aggregate into dense shoals by moving around them so as
to enable feeding himself more effectively (Howell, 1930).
On the other hand, the balaenopterid whales other than sei whale feed byswallowing the food contained water. However, the feeding type employed by
the whale is not always fixed but varies with case by case. In the North PacificSci. Rep. Whales Res. Inst.,
No. 26, 1974

88

KAWAMURA

relatively larger sized fishes such as the pacific saury, pacific cod, mackerel, sardines
and some squids are fed by the baleen whales in addition to the planktonic crustaceans (Nemoto, 1957; Kawamura, 1973a). Feeding by skimming type which
seems to be largely employed by sei whale may possibly be less effective against thesekind of well swimming food organisms. The sei whale, therefore, is considered tofeed by rather combined ways of both skimming and swallowing types, and this
supposition would be supported by the following fact: the variation or the change
in feeding method is known even in some plankton eating fishes. For example,
both biting and filtering types are employed in anchovy by the size of the prey organisms and their population density in the sea (Leong and O'connell, 1969).
The foodstuff swallowed is preserved temporalily in the first stomach, and thiskind of function is characteristic in baleen whales among the marine mammals. Studying on the anatomy of the first stomach of whales, Hosokawa and Kamiya (1971)
concluded after discussing on its ecological recognition that there might be need todeposit the food as far as the food is available since the whales in their feeding place
have been faced the competition with the others for a limited amount of foodstuff.
Under these above mention circumstances, the observations on the amount offood organisms in the first stomch would be an important materials in connection
with the feeding habits of whales and the distribution ecology in the food organisms such as their patchiness and the population density. However, Betesheva(1955), Nemoto (1957) and Bannister and Baker (1967) have pointed out that thewhales under chasing would possibly vomit their stomach contents supposedly fromfatigue after long and continuous chasing. If this occur actually, the amount of thestomach contents which is found in carcasses would be greatly decreased, andtherefore, before going further the matter was examined and discussed in the following section.

Influence of chasing time to stomach contents
Prior to further discussion on the amount of food in the first stomach, it was
examined and discussed that to what extent the chasing by catcher boast influences on the amount of stomach contents due to vomit. This however havebeen discussed fully in the previous report (Kawamura, 1970e, 1971a), then I will
redescribe here only an abstracts and conclusions by quoting my previous reports.
The duration of chasing time by catcher boats which might influence on thefulness of stomach contents of whales was examined on fin, sei, and sperm whalescaught in the northern North Pacific during the summer of 1969. Of 895 whales
observed only 28 whales (3.6%) vomited out their stomach contents while beingchased and sperm whale vomited most frequently (16.8%) whereas sei and fin
whales were 1.1 % and 0.78% respecitively (Table 10-1). The diet of the whales
concerned was consisted of boarfish, squids, copepods and euphausiids. It was often
observed that the whales likely to vomit out more larger sized foodstuff such as
boarfish than that of copepods and euphausiids. The amount of stomach contents vomited was negligibly few, and has no significant influences on the amountof stomach contents which have been obtained from carcasses. Most whales (80%)
10-1.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

89

FEEDING HABITS OF SEI WHALE

were caught within 40 minutes of chasing, and the number of whales which would
vomit out their stomach contents does not always increase in proportion to the prolongation in the duration of chasing time. There are one possibility left behhindthat whales may vomit the stomach contents in the subsurface waters during long
restless chasing by catcher boats, since it must be fairly difficult to detect any vomited foodstuff from the boats. The behavior of vomiting a bulk of foodstuff in thesubsurface waters, however, presumably causes heavy muscular activity for thosewhales, and they would not vomit any foodstuff in the subsurface waters since thewhales under diving likely to minimize the oxygen consumption as little as possible (Scholander, 1940; Slijper, 1958a).
TABLE 10-1. NUMBER OF WHALES OBSERVED BY SIX CATCHER BOATS WHICH
PARTICIPATED IN THE NORTH PACIFIC WHALING OPERATIONS IN 1969.
Floating factory

Kyokuyo Maru No. 3

Tonan Maru

Nisshin Maru

Catcher boats participated (day/month)
Kyo
Maru
No. 12(18/V25/VII)

Kyo
Maru
No. 15(6/V18/VIII)

Kanan
Maru
No. 25(19/V24/VII)

Kanan
Maru
No. 26(24/V8/VII)

VomitedNone
Unknown

22

74

55
15

VomitedNone
Unknown

4

25
8

Duration of operation

Sei whale

Fin whale

Sperm whale

Vomited
None

16

Toshi
Maru
No. 17(16/V4/VIII)

Toshi
Maru
No. 18(17/V4/VIll)

Total

102
13

175

5
174
6

6
427
209

16
7

24
28

85
43

1
23

21
104

20
81

* Sperm whale was not observed expect Kyo Maru No. 15 and Toshi Maru No. 18.
10-2. Amount of stomach contents
The amount of the stomach contents was measured on the animals whichwere appeared to be fully repleted with food. For the measurement in the field abasin of known volume was used to remove the stomach contents completely fromthe opened stomach, and the amount was calculated by multiplying the number ofbasin which was required for the complete removal. Since the stomach contents
removed by this way contain the water to some extent, the weighing of a basin-fullorganisms was made after draining away the water. I have reported on the amountof the stomach contents in three southern species of baleen whales (Kawamura,1970a). It is however, considered necessary to give the results for further discussions, I redescribed here a part of descriptions in the previous report.
In the Antarctic, as I showed in a brief note (Kawamura, l 968b) the amountof stomach contents of 14 sei whales which fed on Calanus tonsus, Parathemisto gaudichaudii, Euphausia superba and Euphausia vallentini was measured (Table 10-2). The
weighing of stomach contents were carried out on the stomachs being judged asSci. Rep. Whales Res. Inst.,
No. 26, 1974

90

KAWAMURA" full " by eyes, and full data including fin and minke whales were given in Appendix.
The 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(1962b) mentioned that there was a quite well agreement between the weight andthe degree of replation of stomach judged by eyes. However, as shown in Appendix
there were considerable variations in the case of the Antarctic sei whale. It canbe said in general that the whales caught before 0900 hours carry somewhat freshand large amount of stomach contents, and the proportional weight of water gradually increases toward noon due to digestion.
TABLE 10-2. AN AVERAGE AND THE MAXIMUM AMOUNT OF STOMACH CONTENTS
OF SEI AND FIN WHALES CAUGHT IN THE ANTARCTIC OCEAN.

Species ofwhale
Sei whale

Body length(m)13.0-13.9
14 .0-14 .9
15.0-15.9
16.0-16.9

Fin whale

18.0-18.9
20.0-20.9
21.0-21.9
22.0-22.9

Sex

AverageNo. of whale
Total
examined
Volumeweight(1)(kg)

FemaleMale
FemaleMale
FemaleMale
Female
Male

2
0
2
5

FemaleMale
FemaleMale
FemaleMale
FemaleMale

03

MaximumTotalweight(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

1
0
0
2
1
0

It has long been the obscure mystery or the matter of interest how much thebaleen whales take food in a day. According to Nemoto (1959) Collett (1912)
early 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; Nemoto, 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 andfound a considerable variations in the amount of stomach contents (91.0- 759.0 kg)
notwithstanding the fact that the majority of all stomachs concerned were repleted
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

91

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.
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 euphausiides. This fact leads to a consideration that the larger the size of food organisms,
the larger amount of stomach contents is expected. Such a tendency is also shownin 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 (Table 10-3).
TABLE 10-3. AMOUNT OF FOOD USUALLY FOUND IN THE FIRSTSTOMACH OF ANTARCTIC BALEEN WHALES.
Species ofwhale

Kind of foodorganisms

Amount of foodusually foundSei whale

Copepoda
Amphipoda
Euphausiids
Euphausiids
Euphausiids

less than 100 kg
150-250 kg
150-200 kg
300-900kg
30kg

Fin whale
Minke whale

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.

10-3. Daily variation in feeding activity
Although the daily variation in feeding activity in terms of the percentage
figures is rather well known in fin whales while not in sei whale, and in this point ofviews Kawamura (1970a) studied on sei whale. Since several facts found in his
report are considered to be suggestive on this matter, a section of the results wereredescribed: It has been known that the feeding activity of baleen whales
in a day in terms of the percentages varies in general with a bimodal curve which
has a maxima in the early morning and in the evening (Nemoto, 1957, 1959). Oneof his results (Nemoto, 1957) suggests that baleen whales somewhat actively
feed twice a day in many cases though each patterns of feeding activity are variablewith the kind of food partaining to their diurnal vertical movement, seasons, latitudinal positions, or sometimes with the bottom topography of whaling grounds.
Sometimes, however, the baleen whales show a evidence suggesting to feed only
once a day (Nishiwaki and Ohe, 1951). In any case, it is considered to be quite
important to accumulate the evidences on the feeding habit of baleen whales especially of sei whales in relation to estimating the nutritional budget among the foodwebs in their feeding grounds. However, it is also nesessary to figure out the feeding patterns of baleen whales by theoretical and experimental methods by assuming
such a feeding model as Klumov (1961) instituted for this purpose.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

KAWAMURA

92

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 5-1 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
to examine the whales food by the species since each food organisms has their own
peculiar migratory patterns in a day. The hourly change in the feeding activityof sei whale in the whaling areas III, IV and Vis demonstrated in Fig. 10-1. It isnoticed 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 thatthe most 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 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
90~Areas Ill & IV

80f

~Area V

70

60

~ 50
c.

~ 40
u
~ 30

P..
,-'

--'()..---o-.... -<:r.,,......a........ ,o--4 ..._._._.,,/
20 ....
1005'"Q. -calanus,'>f' ....""....X'"'"'-'().-~'~c~~.... rca1anus..................

.. ................................................ ._ ................'..

68....., ..",,'...... .......'I'.:\.

•,,
7

9

10 11

12

13 14 15 16 17 18 19 20 21

22

Hour

Fig. 10-1. Feeding percentage of sei whale in the whaling Areas III, IV, and V,
1967 /68.

and IV were 82 percent and 25 percent respectively. The general trends of feeding activity of sei whale in the Su ban tactic 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 tothe differences of the kind of food organisms taken in both whaling grounds. From
the figures, it is naturally considered that the most of sei whales in the Antarctic
heavily take a dense population of food once in the morning possibly by ' swallowing ' or ' skimming ', and take a relatively scattered poor population of food organisms by ' skimming ' during the daytime towards the evening, as the manner described by Ingebrigtsen (1929) and Nemoto (1957, 1959).
The components of the "Calanus" food are represented by two dominant
species, Calanus tonsus and Calanus simillimus. In the Indian sector of the Antarctic
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

93

a considerable number of both Calanus tonsus and Calanus simillimus occurred as
principal food source of sei whale while only Calanus tonsus was observed in the
Tasman Sea and in the Pacific sector of the Antarctic (area IV and V). Since there
are considerable differences in the behaviour of diurnal vertical migration between
Calanus tonsus and Calanus similimus the extent of the repletion of stomach contents
by the time was also differed between those two copepod species (Fig. 10-2).
Those differences due to diel migratory habits of food organisms have also been
known' in decapod crustacean, Sergestes similis which is locally important food ofsei and fin whales in the North Pacific (Omori et al., 1972). In both Calanus tonsus
and Calanus simillimus, the repletion of stomach was relatively small with the quantity of food less than 50 percent during the daytime. It is noticed clearly that thealmost fully repleted stomaches (" 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 of Calanus simillimus was exclusively
fed only in the evening. This fact would be the result from being exactly followed

Hour

Fig. 10-2. Number of whales fed on Calanus simillimus (black colum and solid line),
and C. tonsus (vacant col um and broken line) by the four different degrees in stomach
fulness. Degrees of fulness are as follows: 'r' less than 25 percent, 'rr' 25-50
percent, 'rrr' 50-75 percent, 'R' 75-100 percent.

to the differences of the migratory habits of both species. According to Hardy andGunther (1935), Calanus simillimus is regarded as one of the quantitatively important
copepods in the South Georgian waters, and this species shows a distinct diurnalvertical migration as well as Drepanopus pectinatus; the bulk of Calanus simillimus
population begins upward movement at about 1700 hours in the evening andreachs 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 a consideration that
there would be only a chance for sei whale to feed on Calanus simillimus in the evening throughout a day. It is interesting to find that the stomach of "full" occurred very frequently in the evening so as to support the consideration of feeding'once' in a day.
Calanus tonsus, on the other hand, is a comparable species to Calanus plumchrus
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

94

KAWAMURA

in the northern North Pacific, and this species of at least in the copepodite stage
V is recognized in general to show no such a distinct diel vertical migration as
Calanus simillimus. Judging from its hydrological and taxonomical affinities to
Calanus plumchrus (Tanaka, 1954, 1967; Jillett, 1968), it might presumably be considered that Calanus tonsus of 5th copepodite stage does not show any distinct dielvertical migration. The occurrence of " full " stomachs with Calanus tonsus during
the daytime suggests a quite well availability of this foodstuff in the surface waters
so as to be fed by the sei whale throughout a day.
In summarizing the above mentioned results, it would possibly be said thatthe sei whale feeds whenever the foodstuff is available within a reasonable spacial
range, and therefore its diel feeding pattern so far as it is expressed by the feeding
percentages concerned may be different by the kind of migratory habits of its
food organisms. Concerning to these food habits of sei whale, a recognition on theecological means of the first stomach by Hosokawa and Kamiya (1971) as mentioned
in the begining of this section would be well understood. Baleen whales in Patagonian waters (Matthews, 1932) and humpback whale in New Zealand waters(Dawbin, 1956) eat but little food, and later, Bannister and Baker (1967) considered that the whales under those circumstances would have to feed whenever
there some amount of accumulations of food organisms to fill their nutritional requirements.
10-4. Possible cause induces a decrease in the fulness of stomach contents
The number of animals well repleted with food decreased along with the duration of chasing extends over 40 minutes regardless the kind of food organisms (Kawamura, 197la). The whales with fully repleted stomach were foundup to 30 to 40 minutes of chasing time in the morning but they decreased gradually
down to less than 10 minutes chasing in the evening. The whales with moderately
repleted stomach, on the other hand, were found up to 70 to 80 minutes of chasingtime in the morning, then it remarkably prolonged to more than 120 minutes ofchasing during midday until it was shortened again in the evening. There observed to present two different kinds of varing patterns in relation to the dailychange of the duration of chasing time and the degree of the fulness of stomach.
One of possible explanations for those two different patterns would be found in
the proceed of digestion, that is, most whales with moderately repleted stomach in
midday might have had been fully repleted in the morning, and such whales would
shift to those moderately repleted stomach by digestion toward midday (Fig. 10-3).
The duration of chasing time which corresponds to the degree of the fulness of
stomach seems to be shortened from the morning toward the evening. There observed
more or less inversed relationship between the duration of chasing time and thedegree of the fulness of first stomach through three different time bands, i.e. themore the stomach fully repleted, the more shorter time of chasing is expected.
This fact makes us confirm the former observations (Ingebrigtsen, 1929; Nemoto,1957). So often occurrence of well repleted whales in the morning along withrelatively longer duration of chasing time and its hourly change lead to a consideraSci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

95

tion that the most whales take a bulk of foodstuff once a day in the morning.
The copepod and euphausiid foods were found in the whales which werecaught after more or less longer duration of chasing than those fed on squids orboarfish. This may be the result partly due to the vomit, i.e. the large sized foodorganisms likely to be vomited much easier than the smaller one.
It is also supposed from the figures that an approximate time required for thedigestion of foods may be estimated. The whales which carry a well repleted
stomach were found most frequently in the morning, and consequently they were
found being widely scattered up to the duration of 30 to 40 minutes chasing before
0900 hour. However, these whales were greatly decreased in the late afternoon,
and they were only found in 10 to 20 minutes chasing after 1500 hour. This must
be a result of decrease in the absolute number of whales which are well repletedwith food. If it is assumed that the whales with fully repleted stomach could be
expected to be caught by the same difficulties throughout the day, the time being'

R0 .,,......
"··'Y •. ·,..

rrr~.

. .........t.

~.

r••• ....

Q........... ..

........................._ . :::·-..

'·................;··....··········......

·-":-·-...
'·_·-·-·-.-.
·······...::::.~:.~::::~'.;i."'·
';),'

)

........

--

+~·-·

/

Decrease ---Duration of Chasing---Jncrease----0---- Sunrise - 0900 ----0900 - 1500-+-1500 - Sunset
Fulness of Stomach (o/o): R 75-100, rrr 50- 75, rr 25 - 50, r<25

Fig. 10-3. Schematic curves showing regressive tendency of the fulness of stomach
contents along with the duration of chasing in three different time bands. Curves
with circle and cross by four different degrees of the fulness of stomach show ashift of those degrees toward lesser direction of the fulness with the lapse oftime from sunrise to sunset.

required to catch them would give an index for estimating the speed of digestion.
The number of whales with fully repleted stomach reduce down to about 70 percent in the first half of day and then to 50 percent in the afternoon; the relative
abundance of whale with fully repleted stomach is considered to have decreased
down to about half in a day time. In another words, 25 to 30 percent of theirstomach contents would be.digested within 5 hours or thereabouts, and these whales
should be shifted to the stomach conditions of " r " to " rrr " of degrees. The
fully repleted stomach with foods would be emptied in this way by the proceed ofdigestion in the following 14- 15 hours.
It is known in the blue white dolphin (Stenella caeruleoalba) and Gill's bottle
nosed dolphin (Tursiops gilli) which were kept alive in aquarium that their stomachs
likely to be emptied within 10 hours or more (Tobayama, personal communication).
He (Tobayama) also observed that a small instrument swallowed by mistake was
excreted after 17 hours. The digesting speed proposed above for baleen whales as
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

96

KAWAMURA

found in this study does not seem unreasonable estimations by taking account of
the fact that high feeding rates in percentage figures are usually found twice a daywith intervals of 10 to 15 hours.
10-5.

Daily ration in sei whale
It is interest to know the amount of food required by a whale per day, say,the daily ration. It has long been subjected to determine the daily ration in smallerwhales in captivity (e.g. Takahashi, 1961; Tobayama and Tamura, 1964). In
larger whales, however, the daily ration has hardly been determined with precisenessalthough there were some assessment being based on the analysis of the fulness andits daily changes (Nemoto, 1957, 1959; Kawamura, 1970a). However, after
examining on the daily rations as function of body weight in small cetaceans,
Sergeant (1969) described the following equations which might be applicable tolarger whales. Firstly, the feeding rate is defined:.
Food per diem. h
X 100 ........................... (!)
Feedmg rate= B do y we1g t
The feeding rate which was found in smaller cetaceans varied 5.26- 13.67
with 8.26 on average, and the values were somewhat constant regardless the species
and the age of animals. Then the following equation was introduced.
Heart weight x 100
1
Body weight
Feeding rate = O.ll ........................... (2)The heart weight as a factor of the equation was found since its weight wellindicates the extent of activity of animals through their metabolisms. According
to these formulations Sergeant (1969) concluded that feeding of 2.0.-2.5 tons per
day in ordinally sized blue whale would be appropriate, and therefore the whale
have to eat fully twice a day. However, the relationships between heart weight
and feeding rate in larger whales are still little known when compared with another mammals (Ridgway, 1966; Ridgway and Johnston, 1966). To make thematter more clear I examined the heart weight of sei whales which were caught
by the floating factories, "Tonan Maru No. 2" and "Nisshin Maru No. 3" in1970/71 Antarctic season and the results were given in Tables 10-4 and 10-5. The
weight of animals were calculated after the following formulae by Omura (1969),
Ohsumi (1969), and Ohsumi et al. (1970):
Sei whale
W=0.0016L2·43
Fin whale
W=0.00024L2. 9
Minke whale W =0.04655L2.a 1
where W is the weight of animals in 103 kg, and Lis the body length in feet but inmeter in minke whale.
The heart weight/body weight in connection with body length and sex did not
differ much (Fig. 10-4). The difference in the latter was only 0.16% 0 , and was
almost no difference in the former which was in such body length as to be caught
regally by whaling, but some variations by age have been known in smaller cetaceans
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

97(Kleinenberg, 1956; Slijper, 1958b ). Table 10-5 was given under combined figuresof both sexes, and the following was found in sei whale.
Heart weight/Body weight = 0.00487.............................. (3)Although Sergeant (1969) found the figure 0.00404 in this relation, the above
described figure would be considered more appropriate since it was derived fromTABLE 10-4.
Body length
(m)
12.1
12.4
12.7
13.0
13.4
13.6
14.1
14.3
14.5
14.8
15.1
15.6
15.7
16.2
8.4*
8.1 *

BODY AND HEART WEIGHTS OF THE ANTARCTIC SEI WHALE
BY THE DIFFERENT BODY SIZES.

Sex
Male
FemaleMale
FemaleMale
FemaleMale
FemaleMale
FemaleMale
FemaleMale
FemaleMale
FemaleMale
FemaleMale
FemaleMale
FemaleMale
FemaleMale
FemaleMale
FemaleMale
Male

Body weight
(ton)
8.94
13.25
14.09
14.89
15. 72
16.56
17.51
18.42
19.35
20.35
21.40
22.40
23.55
24.75
5.38
4.96

Heart weight(kg)

Heart/Body(%0)

AverageNo. of whale
examined

53.2
45.2- 60.0
41.0- 65.1
58.0- 70.0

5.95
5.06-6.71
3.09-4.91
4.38-5.28

5.95
5.89
4.09.
4. 78

2
4
4

62.0- 66.8
61.2- 86.0
56.0- 75.0
62.0- 72.0
75.0- 89.0
70.0- 92.0
74.0- 89.0
90.0-106.0
76.2-106.0
68.0- 93.3
86.0-110.0
86.4- 97.0
83.0- 99.0
78.5-117 .o
90.0-126.0
97 .0-101.0
94.0-126.0
110.0-114.0
99.0-125.0

4.40-4. 74
4.11-5. 78
3.76-5.04
3.94-4.58
4. 77-5.66
4.23-5.56
4.47-5.37
5.14-6.05
4.35-6.05
3.69-5.07
4.67-5.97
4.47-5.01
4.29-5.12
3.86-5. 75
4.42-6.19
4.53-4.72
4.39-5.79
4.91-5.09
4.42-5.58

4.57
4.59
4.43
4.22
5.22
4.59
4.92
5.60
5.43
4.56
5.06
4.79
4.64
4.60
5.10
4.66
5.02
5.00
5.15

2
9
3
5
2
4
4
2
4
7
4
3
5
6
4
3
6
2
3

98.0-142.0

4 .16-6.03

4.91

10

102.5
21.3
22.2

4.14
3.96
4.47

4.14
4.21

* Minke whale.

more larger number of materials. Basing on the above described figures, the feeding per diem in sei whale is calculated by the equations (1) and (3) as follows:
Feeding per diem= 0.0443xBody weight ........................... (4)Then the daily ration in ordinally sized sei whale can be considered about
4.4% of body weight (Fig. 10-5), and that in fin and minke whales was 0.0407
and 0.384 respectively. The overall figures through baleen whales therefore would
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

KAWAMURA

98

be somewhere between 3.8% and 4.4%. These results as a whole agree withthose by Klumov (1963) whose figures were 3.0-4.0% though he expressed it by
the biomass basis, say, gr.-food/kg-muscle weight of animals. The food per diemdemonstrated in Fig. 10-5 shows relatively higher food requirement in sei whale,
and it gets lower gradually in fin and then in minke whales. A quite high food
• Maleo Female

•

'°
-'"".

<N

<N

~

N

~

""!

"?

...:..

~

M

<N

=

+ Male average- Female average... ....... ...,._- - - - - - -- -· -... ... -""?

=
~
=

a,

....;

.,.:,

....

.;.,

~

oO

'"".
.,.,

en

~
.,.,

.,;

..,,.

...:..

0

en

'"".

'°

.,;

Body length (mJFig. 10-4. Heart weight and body weight ratios in southern sei whale.
TABLE 10-5. BODY AND HEART WEIGHTS OF THE ANTARCTIC FIN WHALE
BY THE DIFFERENT BODY SIZES. BOTH MALE AND FEMALE ARE COMBINED.
Body length
(m)

17.3
17.6
17.9
18.2
18.5
18.8
19.1
19.4
19.7
20.0
20.3
20.6
20.9
21.2
21.5
21.8
22.1
22.5
22.8
23.1

Body weight
(ton)
29.33
31.05
32.45
34.20
35.85
37.54
39.30
41.25
43.25
44.99
47.25
49.20
51.40
53.60
55.7
57.9
60.8
63.2
65.4
68.1

Heart weight(kg)
105.6-156.0
102.0-193.0
134.0-150.0
132.0-205.0
138.0-185.0
144.0-200.0
136.0-179.4
158.0-224.0
165.0-220.0
158.0-239.0
185.0-245.0
196.0-280.0
160.0-258.0
195.5-278.0
206.0-350.0
235.0-258.4
180.0-330.0
203.0-379.0
240.0-375.0
276.0-343.0

Heart/Body(%0)

3.60-5.32
3.29-6.22
4.13-4.62
3.86-5.16
3.85-5.16
3.84-5.06
3.46-4.57
3.83-5.43
3.82-5.09
3.51-5.31
3.92-5.19
3.98-5.69
3. ll-5.02
3. 65-5.19
3.70-6.28
4.06-4.46
2.96-5.43
3.21-6.00
3.67-5.73
4.05-5.04

AverageNo. of whales
examined

4.35
4. 78
4.35
4.60
4.61
4.55
4.00
4.35
4.52
4.28
4.57
5.05
4.06
4.46
5.03
4.22
4.22
4.27
4.94
4.43

7
4
3
9
5
8
10
8
5
12
7
7
10
8
8
3
8
7
3
3

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

99

requirement in right whale along with similar trends in sei whale indicates that
their difference from fin and minke whales would be due to the feeding types;
skimming in the former whereas swallowing in the latter.
The amount of the first stomach contents which has been reported in sei whale
1.5

=
,g

1.0

E
Q)
'C
Q)

c.
-0
0

~ 0.5

OL-.L__.L___L__L__lLO_L___L__L_L~2~0-'---'---'---'---.:!:30:--'~~~'-;'40

Body weight (ton)Fig. 10-5.
whales.

Theoretical amount of food per diem in southern sei, fin and minke

TABLE 10-6. AMOUNT OF STOMACH CONTENTS OF SEI WHALE.
Kind of foodCalanus tonsus
Parathemisto gaudichaudii
Euphausia vallentini
Enphausia superba
Euphausia superba

Zooplankton
Calanoida
Pacific saury
Calanus plumchrus

Squid

Amount of food(kg)

Locality

Author54.0
57.6-200.0
79.1-149.6
128.7-149.6
175.0-305.0
59.0
300.0
500.0
50.0-370.0
620.0

Antarctic
Antarctic
Antarctic
Antarctic
S. Georgia
S. Africa
N. Pacific
N. Pacific
N. Pacific
N. PacificKawamura (1970)

Brown (1968)
Best (1967)
Klumov (1963)
Betesheva ( 1954)is given in Table 10-6. It is observed in the table that the amount of food in thestomach of ordinarily sized animal, i.e., 15-24 tons of sei whale is 200 kg or thereabout when they feed on planktonic crustaceans. It could also be said as a wholethat the amount in the stomach decreases with the size of food organisms, and thoseamounts actually measured are considerably low when compared with the daily
ration. If we follow to the daily ration in sei whale of 18 tons in body weight, theanimal requires about 800 kg of food daily, and the stomach of this animal haveto be fully repleted three to four times in a day. However, it seems hardly pasSci. Rep. Whales Res. Inst.,

No. 26, 1974

100

KAWAMURA

sible for the animal to feed 800 kg of Calanus within several hours because Calanus
remains in the surface only a few hours in the morning and evening. Therefore, thesei whale would have to eat even rather scattered food organisms which might haveremained in the surface being apart from the main body of the migrating population. According to Best (1967) the sei whale in South African waters fed zooplankton being consisted of many species, and a considerable number of them were
supposed to be non-aggregating species. This fact suggests that the sei whale can
TABLE 10-7. THE HIGHEST NUMBER OF FOOD COPEPODS PER 1000 M 3 OF
WATER IN THE UPPER 150 METER DEPTH OBTAINED BY THE NORTHPACIFIC STANDARD NET IN THE SOUTHERN WATERS OF
CENTRAL PACIFIC AND TASMAN SEA IN 1968/69.
Highest number ofindividuals by eachstages through all stations occupied ( x 10 3)SpeciesCalanus tonsus

Calanus simillimus

Calanoides acutus

Calanus propinquus

Clausocalanus spp. *Metridia gerlachei
Rhincalanus gigas

female
male
CV
C IV
C III
C II
female
male
CV
C IV
C III
C II
female
CV
C IV
C III
C II
C I
female
male
CV
C IV
C III
female & male
female & copepodites
copepodites & C I-C VI

4.53
0.51
118.28249.58
39.86
2.60
8.10
6.72
60.40
190.73186.69
72.30
1.64
38.07
51.84
103.63
51.84
89.94
1.17
0.97
4.27
6.95
11.45
3179.62384.1756.41

Highest numberof individuals ina haul by species( x 103)12.13
250.58
39.86
2.60
8.06
6.72
60.44
190.73
56.41
10.75
1.64
35.57
75.63
46.09
31.07
89.94
1.17
0.39
4.27
1.55

* Clausocalanus laticeps & C. paululus.
feed even those rather scattered food organisms by skimming type of feeding. It
may be considered anyhow that daily ration of about 800 kg would hardly be takenby the sei whale from its filtering ability and the population density of available
food organisms.
Sci. Rep. Whales Res. Inst.,
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FEEDING HABITS OF SEI WHALE

101

Estimation of population density in the food organisms
One of the most important food organisms of sei whale in the southern whaling ground is copepods, especially C. tonsus and C. simillimus. An ecological importance of these two are comparable to C. cristatus and C. plumchrus in the North
Pacific region.
The amount of food organisms in the stomach would be the result of functionsof both feeding ability of whales and the population density of food organisms.
Studying on the baleen whales in the Fareast seas, Klumov (1961) stated that theamount of stomach contents could not be understood unless the food organisms
distribute such high density as to be hardly known by the net sampling in the sea.
In the southern sei whaling ground the food organisms distribute with the density
as given in Table 10-7 and 10-8. The figures in the tables were obtained by theplankton net hauls through 27 stations in the Tasman Sea and in the Pacific Ocean,

10-6.

TABLE 10-8. THE HIGHEST NUMBER OF INDIVIDUALS OF EUPHAUSIIDS
AND AMPHIPODS PER 1000 M 8 OF WATER IN THE UPPER 150 METER
DEPTH OBTAINED BY THE NORTH PACIFIC STANDARD NET IN
THE SOUTHERN WATERS OF CENTRAL PACIFIC ANDTASMAN SEA IN 1968/69.
Species

Individual number(X 10 8)Remarks" spinifera
Euphausia
Euphausia superba
Euphausia sp.
Euphausiids furcilia

0.26
0.054
0.001
2.81
1.41
1.41
1.11
0.47
0.45
59.48

Immature
Immature
femalefemaleImmature male
Immature female
femaleImmature
Immature

Thysanoessa parva
Thysanoessa vicina
Thysanoessa macrura
Thysanoessa gregaria

0.30
1.09
8.10
7.80

Immature
Immatur;>
Immature

Nematoscelis megalops

0.11

femaleParathemisto gaudichaudii

0.21
0.26
3.42

female, f. compressa
female, f. intermediate
Juvenile

Euphausia simillis var armata
Euphausia simillis
Euphausia lucens
Euphausia vallentini
Euphausia frigida""
and the population density in each copepod species does not show that of underaggregations. The wet weight of copepods were obtained from the stomach contents which were completely consisted of mono-specific population. On the other
hand, the amount of stomach contents was given in Appendix. The amount ofcopepod food was larger in the North Pacific than in the South African and theAntarctic waters. The availability of foodstuff seems in general to be high in the
North Pacific.
Sci. Rep. Whales Res. Inst.,
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KAWAMURA

102

The quantitative distribution of food zooplankton in the subantarctic waters
varied between 15.10 and 426.12 gr./1000 m 3 in wet weight (Kawamura and Kureha, 1970). Since the composition of whales food usually found is monospecific,
the highest figures in the poplation density in net haul samples was given by separating each species (Tables 10-7). A distinct occurrence of copepodites IV and V
in C. tonsus, and adult Clausocalanus laticeps agrees with the composition of the stomach
contents although C. simillimus differed in this respect. Both C. acutus and C. propinquus showed a quite slight occurrence as none of them were found in the stomach
contents. The figures in euphausiids are quantitatively less important due to net
avoidance. However, the dominancy of an important food species; E. vallentini
is indicated. The population density of food organisms was estimated as follows
under two feeding types particularly in the case of C. tonsus, one of a leading foodstuff in the southern feeding ground:

Swallowing
The 14.4 m sei whale caught in the Antarctic feeds at least 54.0 kg of C.
tonsus of copepodites IV and V (Table 10-6), and the average body weight of C.
tonsus is 1.2 mg/individual. (Table 10-9). Accordingly, a total of 54.0 kg. of food C.
TABLE 10-9. WET BODY WEIGHT OF FOOD COPEPODS COLLECTED FROM THE FIRSTSTOMACH OF SEI WHALES CAUGHT IN THE INDIAN SECTOR OF THE ANTARCTIC.
SpeciesCalanus tonsus

Calanus simillimus
Clausocalanus laticeps

Drepanopus pectinatus

Stage
CV
CV
CV
C V +VI female
CV
C V +VI female
femalefemalefemalefemalefemaleWeightNo. of individual
Body
measuredweightNormal Damaged* (mg)
(mg)
200
200
1000
500
500
500
20
20
20
200
20

155
151
595
256
541
745
96
110
186
587
139

26
33
83
105
144
226
71
75
57
358
89

1.19
1.20
1.57
1.66
0.82
0.58
0.15
0.14
0.09
0.26
0.11

State of material

Moderately digested
Moderately digested

Heavily digested
Heavily digested
Heavily digested
Moderately digested* Damaged individuals are supposedly lost their body fluids, and they were regarded as one halfof those undamaged individuals in the wet weight.

tonsus corresponds to 45X10 6 individuals. In order to obtain this number of C.
tonsus under the population density of 262. 7 X 103 inds. /1000 m 3 which was the highest
figures actually found (see Table 10-7), a total of 171.2X10 3 m 3 of water have to
be filtered off by the whale. The volume of water in a gulp in fin whale is supposed
about 6.0 m 3 /30 sec. (Klumov, 1961) whereas in average sized sei whale (14.5 m:
Intern. Whal. Statistics, 1969) the volume of engulped water would be somewhere
between 2.0 and 3.0 m 3 /30 sec.
To examine these figures more clearly the volume of air which was sent into theoral cavity to make the animal afloat was measured (Fig. 10-6), and the average
Sci. Rep. Whales Res. Inst.,

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FEEDING HABITS OF SEI WHALE

103

volume of air used in fin and sei whales was 10.4 m 3 and 8.95 m 3 respectively. In
Fig. 10-7 the dots far above from main body would be due to a leakage of air. Since
the above mentioned air was pressured 3 to 4 times higher than natural pressure,
those amount of air in fin and sei whales could be converted into 2.6-3.5 m 3 , and2.24-2.98 m 3 respectively. It is clear that these figures agree well those above
mentioned. Therefore, a total of 54.0 kg. of C. tonsus could be obtained in 5.5 X
10 2 hours, say, 23 days! As it is noticed in Table 10-6, the amount of the stomach
contents in sei whale sometimes attains at 500-600 kg, and their theoretical daily
ration was 800 kg. Then if we assume 300 kg. of copepod food as their possible
daily ration since an availablity of copepod food would be considerably poor than
20

•

•

0

.6

15

"'.§.""'ill..
.........
_...... , •

=>
~

·o;

0

..,

• • •
•
•
• • ..,..

•• •
•

10

§
0

>

5

+•

0

06
0
0
0

0

Fin Av. 10.4
Sei Av. 8.95

0

0

0

•
11

Fig. 10-6.

12

13

14

15
16
17
Body length (m)

18

19

20

Volume of air used to make afloat the carcasses of sei and fin whales.

the others, a total of 54.0 kg. of stomach contents fills only 1/6 of the daily requirement in sei whale. Accordingly, it could be supposed that the population density of C. tonsus under an aggregation must be found somewhere between 3.4 X
10 7 and 5x 10 7 inds./1000 m 3 (Fig. 10-7).
According to Minoda (1958) the highest population density found in his study
in C. plumchrus in the North Pacific was 395X 103 inds./1000 m 3 , and later the another case revealed as 631X10 3 inds./1000 m 3 (Fae. Fish. Hokkaido Univ., 1963).
Comparing these figures with the density of 367.8X 10 3 inds./1000 m 3 in C. tonsus,
it is noticed that the population density in both cases agrees quite well while those
two are the phenomena in far separated regions each other. These facts indicatethat the upper extreme of population density in copepods would be about up to
4x 10 5 -6X 10 5 inds./1000m3 throughout the world seas though rarely found. The
Sci. Rep. Whales Res. Inst.,.No. 26, 1974

KAWAMURA

104

estimation described above seems quite high density which may almost unbelievable
but it is the patchiness of plankton that gives those high level of the population
density.
20
18

16

range
~ Reasonable
55338Xl0 - 504Xl0 inds./lOOOm'

~ 14
';;;-

""'
.5

8 12
c
z;.

-~

""'"'c:

:3

"'

10
8

"3
c.
0

c...

4

Volume of water filtered by a sei whale (m'/min.)Fig. 10-7. Theoretical estimation of the population density of Ca/anus tonsus patches
which fulfil! the 54.0 kg of C. tonsus within 4 hours.

Skimming
The feeding type actually and most frequently employed by the sei whale isnot swallowing but skimming (Scoresby, 1820; Millais, 1904-1906; Ingebrigtsen,
1929). The sei whale collects foodstuff by filtering continuously the food contained
sea water with the mouth half opened. The right and bowhead whale feed byskimming exlusively while sei whale does not always but frequently.
As it has examined previously a relative filtering ability in the row of baleen
plates in sei whale was l /2.2 against fin whale (Kawamura, 197la). A total
surface area of the inner surface of filtering apparatus in sei whale was about 3.6 m 2 ,and the filtering coefficient was 0.167. By these figures a sei whale can filter off
6.0 m 3 of water effectively by swimming for 10 meters. One of possible and acceptable parameters in regard to feeding by skimming would be; 3 knots in swimming speed, 4 hours in feeding duration and a total of 300 kg of food organisms
is fed. Then the population density of food organisms which fills enough above
mentioned parameters must be 2.13X103 gr./1000 m 3, that is, l.8X 107 inds./1000 m 3 •This figure as the order of density agrees well with the both estimations.
Sci. Rep. Whales Inst.,
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FEEDING HABITS OF SEI WHALE

105

According to Zenkevitch (1963) the biomass of zooplankton standing stockduring the summer in the Okhotsk Sea and Bering Sea rarely shows more than
1.0 gr./m 3 , and those exceeds 3.0 gr./m 3 would only be found in a limited regionof the northern Okhotsk Sea. Kurile region also rarely yields 1.0 gr./m 3 of zooplankton (Klumov, 1961). In the Pacific sector of the Antarctic the biomass ofzooplankton was usually between 0.5 and 2.0 gr/m 3 , and that more than 2.0 gr/m 3
was rarely found. One of the biomasses of C. tonsus in the subantarctic waters
ever found was 0.2.-0.5 gr./m 3 • (Dolgencov, 1970).
By comparing these figures with those estimations in C. tonsus, the biomass or
the population density in C. tonsus as food of sei whale seems considerable higher
numbers than those obtained by the net haul investigations. Those density infood C. tonsus would still under estimated since the 300 kg. of stomach contents
which was assumed in calculation should be doubled or more. However, it should
also be took in account that those extremely dense population would possibly befound only when C. tonsus aggregates into the patches. Manteufel (1939)
stated 9.0 gr/m 3 of population density in Calanus sp., then the biomass of about
21.3 gr/m 3 (l.8xl0 4 inds/m3 ) in C. tonsus population as estimated could be considered quite possible.
The population density of C. tonsus required to fill the 300 kg. of stomach contents by swallowing type feeding was 3.4x 10 7 .-5X10 7 inds./1000 m 3 whereas it was
l.8x 107 inds./1000 m 3 in skimming type. Comparing these figures it could be
supposed that the feeding by skimming type would be more effective to collect thesame amount of foodstuff. The scheme would also support the facts previously
known that the sei whale feeds almost always by employing the skimming typefeeding in the whaling ground.
11.

SWARMS OF CALANUS TONSUS BRADY

As has been mentioned in the previous sections, it was strongly suggested that the
population density in C. tonsus must be maintained at least in such the order of
103 .-10 4 individuals per cubic meter when they swarm into the so-called patches
as to be fed by the sei whale (Kawamura, 1971d). However, the population density
described above was an estimation being based on the amount of C. tonsus in thefirst stomach of whale carcasses and the filtering ability in a row of baleen plates asa function of feeding in sei whale. The theme therefore, was in need of being substantiated by the further evidence in the field, since the general features of swarming
copepods under patchiness along with their population density had been known
quite a few, while those swarm forming phenomena in copepods themselves had
been known in early 1800's in the North Atlantic waters, and have been relatively
well documented (e.g. Marshall and Orr, 1955).
In the following section I will describe some additional evidences on theswarming of C. tonsus in the surface waters. C. tonsus is a typical endemic species
in the Subantarctic waters and considered to be important in a role of marine
ecosystems of the southern waters. However, it is still unknown whether there
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KAWAMURA

were any socialized relationships among the swarming C. tonsus individuals. The
swarming C. tonsus populations are exclusively consisted of stage V copepodites
with a little mixture of adult females. A possible causations of surface swarming
behavior may perhaps be similar to those in mysids (Clutter, 1969) though there
must be some another pattern-forming agencies in copepods.
An uneven and spatial distribution of plankton species has been well known(e.g. Hardy, 1936a, b; Barnes and Marshall, 1951; Cassie, 1959a, b, c, 1960).
However, some recent works (Wiebe, 1970; Kuwahara et al., 1971)on this matterseem to give some confusion in the term of the plankton patchiness: Wiebe (1970),
for instance, defined the " patches " or " patchiness " when the overall concentrations of zooplankters under multispecies composition exceeded a central value
in a data set, which necessarily induce such a quite much occurrence of the" patches " as about 200 patches per a grid of about 100X100 m squares. Thesekind of" patchiness" are, however, considered rather usual phenomena as a distribution pattern widely seen in any localities of the sea. On the other hand, theplankton patches under considerations may be something different from thoseabove mentioned, and also may possibly be different from those quite large scaled
spacial distribution such as treated by Cushing (1962), but identical to those densemonospecific aggregations into swarms or rafts which by Marr's expression, scattered in a plane keeping 1 /3-1 /4 miles intervals of" krill-less" sea. As mentioned
in the previous sections, the composition of patch forming plankton population ismonospecific as known in Euphausia superba (e.g. Hardy and Gunther, 1935; Marr,
1955) or in copepod, Calanus .finmarchicus (Bainbridge, 1952; Kitou, 1956), whichmake the sea discolored by enormous number of swarming plankton species inthe very surface.
11-1. -?_ooplankton swarms as whales food
The swarming organisms as whales food have had been well recognized early
among British whalers in those sperm whaling days in the southern seas, and the"Brazil banks'', according to Beale (1839), is" only discolorations of water causedby myriads of animal cula:: which perhaps form the sustenance of the common
black whale's food; that consisted of" squillce" and other small animals", andBeale (1839) also called them as "submarine pastures". During the cruise on
boad of the H.M.S. "Beagle," Darwin (1906) sighted a fairely well discolored waters
by a huge number of copepod-like minute organisms, and considered that theymust have been the food of whales and seabirds. Apart from recognizing theswarming phenomena of plankton species, Klumov (1961) brought out a subject
under ecological considerations concerning to plankton patchiness that the daily
food requirements of baleen whales would never be filled by the standing stocksof zoplankton known in the Kurile region even by their uppermost extremes, andconcluded that the food zooplankton parhaps be maintained with a density of atleast about 1500-2000 mg per cubic meters. An approach to know the population density in whale's food zooplankton involved an important indications, andlater Omori et al (1972) made an estimation on the population density in swarming
Sci. Rep. Whales Res. Inst.,
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FEEDING HABITS OF SEI WHALE

107

Sergestes similis in the northern North Pacific.
At least the following zooplankton species except copepods have been observed directly as to form a dense swarms or so-called patches apart from those
uneven or spatial distributions of plankton species: Euphausia superba, E. crystallorphias (Marr, 1962), E. pacijica and many others (Komaki, 1967), E. nana, E. similis
Thysanoessa inermis, Th. raschii, Th. spinifera (Nemoto, et al., 1969), Mysid, Metamysidopsis elongata and Acanthomysis sp. (Clutter, 1969), Mysidium columbiae (Steven,1961), Galathea, Munida gregaria (Matthews, 1932; Tabata & Kanamaru, 1970),
Pleuroncodes planipes (Boyd, 1967), macruran, Sergestes lucens (Omori, 1969) andS. similis (Omori et al. 1972). The number of patch forming plankton species
would be doubled or more when we take into account the indirect evidences ofswarming such as the food of baleen whales, among which amphipods, Parathemisto
gaudichaudii is distinct. In these patch forming species the population density
under swarming is usually maintained quite high, say, 1 ind./inch 3 in E. superba(Marr, 1962), 100 crabs/m 2 in Galatheid shrimp, P.planipes (Boyd, 1967), or animals
swim as close as 1.-2 cm one to another in E. pacijica (Komaki, 1967). Patchinessin mysids are relatively well known as mentioned before. Recent biosociologicalstudy on the swarms of mysids, M. elongata and M. columbiae (Clutter, 1969) muchcontributed to our knowledge on the aggregations of zooplankton particularly on
swarming mechanisms along with possible but indicative biological cusations of theaggregation agencies such as density or grouping effects, role of sensory organs orunderwater vibrations and pheromones (e.g. Laverack, 1962; Horridge, 1966;
Ryan, 1966; McLeese, 1973; Dahl et al., 1970a, b).
11-2. Material and method
The freezer ship M. S. "Eiho Maru" (1153 ton) which was chartered by the
Nippon Suisan Co. Ltd., participated to the Antarctic whaling operation in 1971 /72
season, and made a exploratory fishing and scouting for whales on her way down
to the whaling ground. During her cruise in the south- to southwestern waters off
Western Australia in December 11.-26, 1971 when she was engaged in scouting
about for sei whales in advance of comming season, many patches of discoloredwaters by dense aggregations of copepods, Calanus tonsus Brady were observed in
the surface waters. Japanese whaleman calls them as" Uki-esa ",a floating whale's
food. The cruise track and the general hydrography are shown in Fig. 11-1. .
The ship cruised by following up the waters chiefly along the 12.0° .- l 4.0°C isotherms
since high concentrations of sei whales are usually expected under these sea conditions by the whaler's experience.
The surface swarms of C. tonsus which distributed within the range of about
2 miles of both sides of the ship's track were possible to distinguish by their darkbrownish, sometimes blick like reddish discoloration from the surrounding waters,
and the plankton sampling was conducted under inducement by the watchers who
were on the upper deck, since the margin or the boundary of swarms was hardly
visible in closer distance from foredeck. Marr (1962) suggested upon the decreasein detecting ability of the plankton patches when it is partly cloudy weather by
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108

KAWAMURA

Fig. 11-1. Track of the Eiho-Maru with approximate isotherms along the ships
cource during Dec.11-26, 1971andJan.2-11,1972. Blackspotrepresentsthe
ship's noon position. Numerals with arrow shows the serial number of patches
sampled as details are given in Tables 11-3 and 11-5.

confusion with the shades of cloud on the sea surface. However, it was usually
over cast or cloudy throughout this investigation, and any hard difficulties in spotting the C. tonsus patches were not noticed. The number of surface swarms which
occurred along the ship's cource were counted usually by three watchers.
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FEEDING HABITS OF SEI WHALE

109

While the ship cruised at the speed of about 10 knots, the shape and an approximate size of C. tonsus patches that passing through by the ship's course werealso determined as exact as possible by the author on the upper deck. As the eyelevel at the upper deck was relatively low (ea. 8 meters high above the sea level)
there was some difficulties to figure out exact shape of patches which spread out
far beyond in the surface waters where large swells and waves prevailed. The
shape of patches was determined by observing meandering margin of the patches
at least from three different directions, i.e. front, side and back as ship passing throughby them. The margin of far opposite side from the ship could be sometimes determined when the margin of the patches was on the top or on the slope of swells
and waves.
The swarming C. tonsus was collected by two kinds of sampler; the high speed
underway plankton catcher which was slightly modified from its initial model V(Motoda, 1959): 5.0 cm diameter in mouth opening, 72.7 cm overall length, Japanbolting silk cloth GG 54 netting (ea. 0.33 mm mesh apertures), and the RGS flowmeter was mounted inside the sampler for estimating the volume of water filteredby the sampler. The another one was Petersen type vertical closing net (Kawamura, 1968a), having 70 cm mouth opening with pylen #24 netting (ea. 1.0 mm
mesh apertures). The former was used exclusively for estimating the population
density itself, and the latter was for the relative abundance and qualitative analysis
of swarming population.
Towing of the sampling gear was made usually at the speed about 2.-..3 knots
by slowing down the ship's speed by keeping some distance before hand from theswarm in question. When the ship seemed to have crossed over the margin of theswarm and positioned inside, the sampling gear was thrown out in the sea. The
duration of towing varied from several tenth seconds to several minutes according
to the ship's speed and the size of each swarms. In most cases the gear was took inwhile the net seemed to be still amid of the swarms since the purpose of sampling
was focussed chiefly on to know the population density of swarming C. tonsus as
precicely as possible. Thus, ten samples from C. tonsus patches were obtained during
December 14 to 23 (see Fig. 11-1). Apart from these sampling on swarms surface
tows for ten minutes with under way plankton catcher were made routinely every
day, usually at 1000 and 1600 hours (LMT) as far as when there were no surface
swarms on the ship's passage. This sampling offered materials to know the standing stocks of copepods and other zooplankters during daytime as the overallplankton population of background waters.
The quantitative treatment on the samples obtained by the underway plankton catcher was made by the flow-meter readings by comparing them with thosein calibrations, and 80.-..90 percent of filtering coefficient under 2 knot towing was
adopted for the samples obtained by Petersen type vertical closing net.
The population density, however, varied considerably even within the identicalswarm judged by the pattern of discoloration, and those observed between manyother swarms. The underway plankton catcher might have been towed throughnon-swarming waters more or less, which would make the figures on population
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KAWAMURA

density small by dilution. So the results obtained were also variable by the patches
and the observed population density of C. tonsus must be considered as the " atleast " figures.
11-3. General hydrology in the investigated region
As shown in Fig. 11-1 the region investigated spreads over between the latitudes of 30°S and 40°S, and between the longitudes of 95°E and 122°E. The ship
had not equipped any research instruments, and the depth record of temperature
was not known. The general pattern of isotherm distribution was figured out by
refering to Rochford (1962) since the data obtained by the "Eiho Maru" was too
fragmentary and insufficient to show the overall pattern in temperature distribution.
The ship, however, took a cource mainly along the isotherms of about 12.0°,.., 14.0°C
in search for sei whale. The isotherms of these temperature are usually concerned
as a bounday between the Subtropical region and the Subantarctic region, say, theSubtropical Convergence. The most of surface swarms of C. tonsus were found in
this region. The isotherms run for west-east direction roughly parallel to the latitudinal lines although they showed rather complicated features in the waters southof Western Australia where the tongue-like warm waters intrude considerably fromthe north to make the surface temperature relatively high. According to Rochford(1962) the area in question can be regarded as the South Transision Zone where
distinct change in salinity is characteristic.
11-4. Shape, color, and size of C. tonsus swarms
As it is shown in Fig. 11-2 the shape of C. tonsus patches was manifolds.
However, they can be roughly classified into three types of the shape, i.e., meandering stream or streak bands, spindle shape, and quite irregular shape with many
tongue-like protorusions. The shape of patches can be said in general that they
are different to some extent in their complexity from those previously reported
in the patchiness of southern and northern euphausiids (Marr, 1962; Nemoto et al.
1969). Some of them were stream like shape being kept very long for several
miles as having been called the" plankton stream" (Nemoto, 1962). Most of thepatches ~ere formed in the very surface so as to perhaps be easily deformed by thewind and wave actions to show quite irregularity as some figures shown below in
Fig. 11-2. It is noticed in the figure that the C. tonsus patches keep more or lessdefinite shape when the sea surface conditions were smooth enough under slightwind. Movements of the whole body of patches as suggested in some euphausiids(e.g. Nemoto, et al. 1969) were unknown.
Orientation of patches in connection with the relative wind direction and force
were: the longer axis of patches against the wind direction kept at the angle ofabout 90°, or the longer axis kept nearly parallel to the wind direction, and or
incoherent by the mixed characters of the two formers. There seem, however,some another causes such as swells, tidal current or even the action by the Langmuir
circulations (Langmuir, 1938; Scott et al. 1970; George and Edwards, 1973) tobe present other than the wind action. The following fact is also note worthy when
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

111

we consider what causes the plankton patchiness, that is, C. tonsus patches kept
tightly even in the rough sea conditions such as the wind force 5 which seems roughenough to disturb the swarms. Mentioning on the patchiness of Euphausia superba,
Hardy (1936b) pointed out that their patches were kept under the sea condition
up to at least the wind force 7.

@-

..

~~
I
@

~i@

~

~

I~
I~®

®

~

~
t® .

.

:·-.

t

@

Fig. 11-2. Rough sketches of Calanus tonsus patches.
circle show the wind direction and the force.

Arrows and numeral in theSometimes a discoloration of waters by swarming was distinct, but it varied
considerably by patch to patch, or by part to part of even in the identical patch.
There were void or extremely poorly distributed spots in the midst of the patch
through which clear blue water was seen. It is also observed that there were clear
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

KAWAMURA

112

water whenever the discolored water was smashed and turned by the ship. This
seems to be due to " hop and sink" movements as observed in C. finmarchicus
swarms (Bainbridge, 1952). He (Bainbridge, 1952) observed it within 12 inch
depth, and the above facts suggest that the dense swarms in Calanus must be foundwithin very thin layer of the surface. The variations in discoloration character
were seemed to be caused maily by the variable change in population density ofswarming C. tonsus, followed by the character of at what depth the center of swarms
is kept in the surface layer.
The distinct difference in the size of C. tonsus patches from those of euphausiids
was much widely spreading out in the former. Most usual size having been known
previously in euphausiids were several tenth meters in diameter (Marr, 1962;
Ozawa et al. 1967, 1968; Nemoto, et al., 1969), while those in C. tonsuswere hundred
to several hundreds meters in their longer axis. One of the longest sizes under
stream like patches showed the length of about several miles. Kitou (1956) also
reported 15 miles long patches of Calanus finmarchicus in the North Pacific. Thiskind of difference in size might be caused something by nature of organism itself
because the sizes of swarming in patchiness have been known characteristic by theplankton species concerned, i.e. Parathemisto and Salpa sp. usually show 3 miles
wide (Hardy, 1967), and Galathea shows much larger size than Euphausia superba(Ozawa et al. 1967).

i

1-2 patch (s)/h3-5 patches/h

5 patches/hFig. 11-3. Schematic map showing the distribution of patches of C. tonsus during
Dec. 11-24, 1971.

11-5. Distribution of C. tonsus swarms
The number of patches occurred within about 2 miles of both port and starboad
sides along the ship's cource were recorded. As mentioned before the number ofpatches, however, must be regarded as " at least " or round numbers since thepatches of poorly discolored had perhaps been overlooked when they were far
enough from the ship to be detected by binoculars.
Fig. 11-3 demonstrates the general features of the occurrence of C. tonsus
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

113

patches which distributed along the ship's track during December 11-24, 1971.
The patches occurred every day during that period though the frequency in termsof the number of patches per hour was most distinct during Dec. 16-20 when thesea temperature was in 13.0°......, 14.0°C. However, a complete absence in some definite region during Dec. 16- 17 cannot help to be said curious because any unusualsea conditions in temperature were not observed in the region.
The highest number of patches per hour was recorded between 1600 and 1700
hours on Dec. 16 when it was 21 patches/hr. On the way down to the south after
calling Fremantle, Western Australia on Dec. 31, the ship again crossed over theswarm rich area of Dec. 20 at the position between 115° and 116°E longitudes withthe time lag of 11 days and 15 hours. The sea temperature was 14.6°C when crossed the previous track. However, none of signs showing the presence of C. tonsus
swarming were observed in this time.
As it is noticed in the poor occurrence on Dec. 11 and Dec. 24, the C. tonsus
patches usually do not occur in the region where the sea temperature of high above
TABLE 11-1. SEA TEMPERATURE AND THE NUMBER
OF C. TONSUS PATCHES OCCURRED.
Sea temperature(°C)

11.0-11.9
12.0-12.9
13.0-13.9
14.0-14.9
15.0-15:9

No. of patches
4
46

117
49
4

16.0°-l7.0°C prevails (see Table 11-1). According to Brodskii (1964) andJillett(1968), C. tonsus occurs at the sea temperatures between 5.0°......, 15.0°C in the southernwaters, and both Kawamura and Hoshiai (1969) and Kawamura (1970b) also confirmed those temperature as possible conditions of their habitat. Accordingly the distribution range of C. tonsus as a function of sea temperatures concerned would beconsidered as relatively wide ranged. However, the main body of early summer
concentration of sei whale which exclusively feeds on C. tonsus patches (Kawamura,1970a) in the Subantarctic waters is found at the temperature of 10.0°......, 16.0°C
accompanying distinct temperature gradient (Nasu and Masaki, 1970). These fact
and Table 11-1 suggest that C. tonsus prefers somewhat warmer waters, and its
patch would not have been formed much in the waters south of 40°S and in thewaters under the temperature of higher than 16.0°C.
To know the relationship between the occurrence of patches and the sea
temperature more precisely, Fig. 11-4 was arranged. As mentioned before, C.
tonsus patches occurred most frequently during Dec. 14-20, and the trends of sea
temperature change by hours in connection with the occurrence of patches during
those period were distinct; a very frequent occurrence of patches can be expectedunder the small-scaled variable temperature change. The sea temperature in
the figure represents the value measured every hour, but it varied very frequently
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

KAWAMURA

114

CD

15~ Dec. 12
14 -: '-I Dec. 20

13

ttt

'

@®CD

12

c.-----

0- - - - - - - 5 4------ 5 - 13
12

o
15
14

13t

tt t tt

12' ' ~__'.___'.. ~ -------~CDCD @

3---------~

®@CD@

p

c-

4-3 - - - - 4 --3 --Dec. 15

®

-

be

5-4---3----Dec 22
• '
•
.

~

'
~ d--. o _________..be -------... c - - - - 1'>
2 3 4 5114 q>j@~13

16

Dec. 23

15

I-

Dec. 24

16 ~······
15

o

2

be

3 -2 ---.1 2 1 -c2-

1:Dec.19?J~~
13t~, ,CD;~
c

~

c
14 0
3-4-5------65 6 7 8 9 10 11121314 15 16 17 18 19 20
Ship's mean timec o-

5 5 6 7 8 9 10 1112 13 14 15 16 17 18 19 20
Ship's mean time
Fig. 11-4. Sea temperature and the occurrence of C. tonsus patches along the ship's
track during Dec. 12-24, 1971. Arrow shows the time of occurrece and the numeral encircled shows the total number of patches occurred in every one hour.

TABLE ll-2.

TEMPERATURE VARIATION WITHIN VERY SHORT TIME.

Date

Time (SMT)

Dec. 171520-1600
1620-1730
13001200-1220
1350-1640
17000700-0800

Dec. 18
Dec. 20

Dec. 21

Temperature change (°C)

14.5
13.3
14.2
12.3
Very frequent change within the range of 0.2 ..... 0.3
12.3
14.7
12.0
11.9
15 .1
11.9
14.8
11.9
11. 7
14.8
12.4
11.9
Sci. Rep. Whales Res. Inst.,

No. 26, 1974

FEEDING HABITS OF SEI WHALE

115

through hours to hours as an example given in Table 11-2. This suggests that theoccurrence of patches would be closely related to the characters of sea temperature
distribution especially to the small-scaled local hydrological structures, which something likely to micro-distribution of plankton as demonstrated by Cassie (1959). Poor
occurrence of the patches during Dec. 23-24 would be attributed to an unfavourable
high temperatures for swarm formation, and those on Dec. 12- 13 should be notedas the result of monotonous hydrological conditions possibly due to relatively poor
temperature gradient.
The conditions of sea surface in terms of wind force varied from class 1 to 5
throughout the investigation though the most was in the class 3 to 4. During Dec.
16-20, when the patches appeared frequently, the wind of class 4 or 5 prevailed.
This fact suggests that C. tonsus patches never be dispersed or scattered away atleast under these roughness of the sea surface.

Frequency distribution by hourFig. 11-5 demonstrates the frequency distribution of C. tonsus patches by every
observed hour. A total of 220 patches was counted. As far as the figure concerned, the diel variation of occurrence makes us confirm that C. tonsus patches
which were consisted of almost exclusively by the copepodite stage V likely to movevertically, and a considerable number of patches come up to the very surface in
11-6.

50
al
>

~ 40

.c
0

"'
"'

! 30
""'

2"' 20
c.i
"O
ci

2:

'-'

10

04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20
Ship's mean time

Fig. 11-5.
1971.

Frequency distribution in the number of C. tonsus patches, Dec. 11-24,

the evening between 1700 and 1800 hours. It is also shown that there are twoother peaks in frequency distribution: early morning and daytime, although they
are hardly comparable to those found in the evening. By analysing the feeding
habits of southern sei whale which feeds on C. tonsus exclusively, Kawamura (1970a)
considered that C. tonsus of copepodite stage V does not make any diel verticalmigration. So it seems disagree with the above results each other. It is, however,considered that C. tonsus patches move slightly down to such the depth, say, 1 or 2
meters under the surface during daytime as to be hardly detected by eyes but still
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

KAWAMURA

116

remaining within the enough depth to be fed by the sei whale. This vertical movements in whale's food can be recognized as "Uki-esa ", a floating food and "Sokoesa," a bottom food which were introduced by the Japanese whalers. They are notscattered away but still keeping swarm during daytime since the routine samplingby underway plankton catcher at 1OOO and 1600 hours did not show any trends oftheir dispersal which may cause poor occurrence of C. tonsus patches during daytime.
The poor occurrence both in 0800......, 0900 hours and 1300 ,......1400 hours corresponds to 3,......4 hours of the time lag from astronomical twilight at 40°S in December(Japan Maritime Safety Agency, 1971) in the former and 4.7-5.9 hours for thelatter. This fact suggests that the light condition in or under the surface varies
considerably with both cases, and that the vertical movements of C. tonsus patches
may possibly not correspond to the light condition. Those small scale movementof patches would also differ from patch to patch themselves. The patches of E.
superba likely to occur more frequently both in the morning and evening, and thoseby Galathea are distinct in the daytime (Ozawa et al., 1967). The manifold charactors of movements by the kind of patch forming organisms make us confirm thatthe behavior of C. tonsus patches above mentioned may be, as Cassie (1960) suggested, by some internal behavior patterns within the species.
11-7. Population density in the C. tonsus patches
In the study on the food and feeding habits of southern sei whales, it wasestimated theoretically that the population density in C. tonsus patches have to be
maintained at least in the order of 10 4 individuals per cubic meter (Kawamura,
PATCHES OF CALANUS TONSUS AND PARATHEMISTOTABLE ll-3.
Position
No. ofpatches

Date

1
2
3
4
5
6
7
8
9
10
II
12
13
14
15
16

Dec. 14
Dec. 14
Dec. 16
Dec. 17
Dec. 18
Dec. 20
Dec. 21
Dec. 22
Dec. 22
Dec. 23
Jan. 3Jan. 4Jan. 5Jan. 5Jan. 6
Jan. 11I)2),..------.r'---

Lat.
(S)

Long.
(E)

37-14
36-26
37-56
38-37
39-31
38-59
39-21
39-36
39-54
38-19
49-40
53-09
55-40
56-22
57-17
57-14

99-36
101-21
106-39ll0-07111-56115-21
117-57120-22120-54120-48118-35
119-35l 19-57
118-50
117-07
97-03

Time
(SMT)

Sea
temp.

0801-0811
1845-1856
1730
1820
1556-1558
0715
0729-0730
0720-0722
1029-1032
1107-1108
1906-1916
1600
0740-0744
1500-1505
0341-0350
2029-2035

13.6
14.87
13.54
13.21
13.80
13.49
12.13
12.90
13.10
13.0
6.24
5.60
4.20
4.00
3.40
2.20

coq

Weather

0

c
c
0

c
0
0
0

c
0
BC
F
F
D

0
R

Wind
direct. &
force
NNW 3
NW 3
ENE 4
ENE 4
NNW 1
s4
SSE 5
SE 3
SSE 3
ESE 2
NW 4
NW 6
NNW 3
NNE 5
SSW 5
ENE 5

Petersen Type Vertical Closing Net (Kawamura, 1968a).
Simple Underway Plankton Catcher (Motoda, 1959).

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

117

FEEDING HABITS OF SEI WHALE

1971a). One of the purposes of the investigation on C. tonsus patches was to get
an evidense which directly supports those theoretical estimations.
Table 11-3 presents the details of ten C. tonsus patches which were sampledactually, and the quantitative results on the samples were given separately. In
the most of sampling in the field, the plankton catcher was towed as to cross overthe patches in their short axis. The duration of net towing varied from several
tenth seconds to several minutes since individual density varied both vertical andhorizontal plane even within the identical patch in addion to the variation of patch
sizes. As it will mentioned later, the patches were composed of almost solely by
C. tonsus, and the number of individuals in a haul was determined by sub-samplinga small fraction of materials such as 1.0 gram or so.
The individual number of C. tonsus patches per cubic meter of water varied
considerably by the patches: 330 inds./ms as the lower extreme and 23,680 inds./
ms followed by 21, 165 inds./ms as the upper extremes. So the individual
density found in this study was in the range of 102 to 104 inds./ms. Some ofthese figures would not represent an exact density because the sampling method
employed in this investigation was in danger of failure in quantitative treatment due
to the irregularity of individual distribution within the patch and also due to thosevariables in vertical section against the definite sampling level in the water. Accordingly the population density within the patches always tends to be under estimated as Fraser (1962) mentioned the difficulty on this matter. The population
density of 2Xl0 4 -3Xl0 4 mg/ms, which is equivalent to about 3.8-5.7Xl0 3 mg
dry weight/ms (after dry/wet weight ratio of C. tonsus by Bradford, 1972) would be
GAUDICHAUDII WHICH WERE SAMPLED BY THE NET.

Kind ofnet used
PVCN'

Kind of patchorganism
Calanus tonsus"

SUPC 2

"
"
"
"
"
"
PVCN
"
"
"
"

3)
4)

"
"

Approx.
size ofpatches 840x50030x12010x50010x400100x300
lOx 150
60x500150x100
6x500
IOOx 1000

Parathemisw gaudichaudii unknown

"
"
"
"

"
"
"

Wet weightper

No. of individuals
per
haul

m•

144633146545
4750
2884
16720
266
1525
5035
167
123
1688
389
565
353
2100
4273

670-761623-701 4
23680
4

21165
3446
6277
8626
330
350
8-9 4
36-41 4
7-84
3-44
8-94
3-44

haul (mg)m 3 (mg)

177900212690
5890
4710
27500

848-937 4
905-10184
29362

2990
9500

12305
16274

5800

27-31 4

32300
91900

129-1454
72-81 434810

Width X Length (m).
Upper and lower extremes of 80% and 90% fiiltering coefficiencies of the PVCN when towed
at the speed of 2 knots.

Sci. Rep. Whales l?es. Inst.,
No. 26, 1974

KAWAMURA

118

agreeable when compared with the previous estimations of between 3-6x 10 4
inds./m 3 (Kawamura, 197ld), and the result of 9x l0 3 mg/m 3 in Calanus (Manteufel,
1939). The above results also well agrees to the figure obtained in Calanus.finmarchicus patches by Kitou (1956), where 8,208 individuals per o,....., 1 meter haul(ea. 2X 10 4 inds./m 3 ) were recorded.

,(ooplankton abundance in the back ground waters
To compare the quite large zooplankton standing stocks maintained by C.
tonsus patches with those lying in the waters outside from the patches as a background, sampling by 15 minutes surface tow with underway plankton catcher was
conducted twice a day during Dec. 11-26, and the Petersen type vertical closing
net was drifted at times after sunset as supplemental sampling.
Table 11-4 gives the figure that zooplankwn standing stocks are very poor during the daytime when only 1-2 individuals per cubic meter of water was found. The
area investigated was so barren as a whole only maintaining organisms less than 10
mg/m 3 throughout the investigated period though they increased to about two folds ormore in the night; 1-60 mg/m 3 • Comparing a poor occurrence both in the numberof species and individuals during daytime, most samples in the night showed ratherrich zooplankton communities by C. tonsus of stages V and VI of female, Neocalanus
gracilis, Euphausia lucens, E. recurva, Ostracods, Doliolum sp. Salpa sp. and Sagitta sp.
11-8.

TABLE 11-4. AVERAGED ZOOPLANKTON ABUNDANCE COLLECTED BY UNDERWAY PLANKTON CATCHER IN 15
MINUTES SURFACE TOW DURING DEC. 11~26, 1971.
Organisms

Abundance

Calanus tonsus Copepodite V
Micro-calanoida
Amphipoda or euphausiacea
Doliolum or Sal,pa

0-1 ind./m 30-20 ind./m 3
0-1 ind./m 3
0-0.1 gr/m 8

However, in the region concerned to this study it has been known as relatively
poor in zooplankton population having been reported less than 25 mg/m 3 (Tranter,
1962), and euphausiids also distribute as poor as in the tropical region of the Indian
Ocean (Baker, 1965). The region under consideration can be noted quite characteristic where food rich waters float like a islands or rafts in the ocean which would
possibly give a quite different results in the estimation of plankton biomass by
sampling condition whether the patch or a part of it were collected or not. Baker(1965) stressed on this matter while he was studying on EujJhausia vallentini, one of
the another important whale's food in the Subantarctic region.
The occurrence of C. tonsus patches can be considered to make the region quitecharacteristic as an ecological environment particularly for the predators in higher
trophic levels such as Scomberesox saurus, Gonostomatid fishes (Kubota & Kawamura,1972) in the pelagic waters and basking sharks Cetorhinus maximus in offshore waters(Bradford, 1972).
Sci. Rep. Whales Res. Inst.,

No. 26, 1974

FEEDING HABITS OF SEI WHALE

119

11-9. Some biological characters in the C. tonsus patches
The size composition of C. tonsus population which formed patches is demonstrated in Fig. 11-6 which was obtained by examining 1152 individuals in all.
The size of C. tonsus in stage V copepodites through ten patches varied almost within
the range of 3.2-3.3 mm with an average 3.295mm (N: 1141). There were nostage V copepodites smaller than 2.8 mm and those larger than 3.6 mm. In contrast to dominant occurrence of stage V copepodite (99.2 percent on average) the
adult females occurred but very small numbers, 11 out of 1152 individuals. Theyvaried between 3.5 mm and 4.1 mm with an average 3. 764 mm, and their size
distribution agrees well to that of the populations usually found in 40°S latitude(Brodskii, 1964) where it seems about 3.78 mm as his figures concerned. A fairly
400

300

"'c:

·~
>

0

200

6

z

100

CVI
Female!

... .,.,;'"'"' '°.,.,; .,.,; .,.,;"' .,.,;.,.,; .,.,;
C'J

00

N=ll
0)

0

.,.,;

..;.

..;.

Range of body length (mm)Fig. 11-6.

Variability of the body length of Calanus tonsus which formed patches.

poor occurrence of adult females among patch forming population agrees to theresult on the food analysis in sei whales (Kawamura, 1970a) and it is also similar
to net samples obtained in circumpolar waters (e.g. Brodskii, 1964).
However, the size of C. tonsus by each patches as numbered 1 to 10 in Table
11-5 shows some interesting facts: the patches of Nos. 1 and 2 were consisted ofrelatively small sized individuals of 2.8-3.4 mm with an average 3.18 mm and of
2.9-3.5 mm with an average 3.28 mm respectively. In contrast to this figures,the patches of Nos. 3 to 10 were consisted of more larger individuals with the sizeof 3.1-3.6 mm with an average 3.32 mm. There seems two possible explanations
on the di:ffere nee in size distribution of stage V copepodites of C. tonsus:
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

KAWAMURA

120

During the austral summer it is known that two generations of C. tonsus instage V copepodites as summer population are present, that is, the individuals ofprevious year origin and that developed in the current season (Jillett, 1968), anddifferences in body length composition in the C. tonsus patches may be due to thisbreeding character. One of the anothers also could be considered. According toBrodskii (1964) there are latitudinal difference in body size of C. tonsus, and larger
individuals are usually found in higher latitudes. So it is possible that the patchesof Nos. 1 and 2 were relatively northern water origin accompanying with warm
water species of zooplankton (see Table 11-5 ). These facts suggests that both thepatches of Nos. 1 and 2 might have been isolated through their development fromothers of Nos. 3 to 10, which were possibly the offsprings from the same initial
population stock.
TABLE 11-5.
No. ofpatches

BIOLOGICAL CHARACTERS OF CALANUS TONSUS PATCHES.

Av. body Av. bodyweight
size
(mm)
(mg)

CVI ~/CV

1.23

1.65

3.18

(%)

Range of body size (mm)
CV

CVI~

2.8-3.4

3.7-3.8

2

3.28

1.45

3.22

2.9-3.6

3.6-3.8

3

3.34

1.24

0.77

3.1-3.6

4.0

4

3.35

1.63

0.87

3.1-3.6

3.8

5

3.35

1.64

16.23

3.0-3.6

3.5

6
7
8

3.28
3.39
3.25

1.96
1.89

0.78

3.0-3.5
3.0-3.7
3.1-3.5

4.1

9

3.30

3.1-3.6

10

3.27

3.1-3.5

Organisms occurredwith C. tonsus(No. of inds./haul)
Vellella vellella (18)Amphipoda (36)Cavolinia sp. (I)Dotiolum sp. (473)
and others*
Thysanoessa sp. ( 1)Amphipoda (2)Thysanoessa sp. (7)& juv. (9)Euphausia sp. juv. (2)Amphipoda (1)Copepoda (3)Amphipoda (1)* Diphyes antarctica (1), Cavolinia sp. (1), Combjelly (1), Cyllopus ?(l), Euphausia sp. juv. (6), Squid (1),and fish larva ( 1).

The geographical location where the patches Nos. 1 and 2 were collected wasin the waters far west from the others, and relative abundance of adult females islarge enough to distinguish them from another patches. The zooplankton species
entangled along with a bulk of C. tonsus seem also to be something different between
the patches Nos. 1-2 and Nos. 3-10. In the Nos. 1-2 patches there were foundsome warm water species such as Vellella vellella, Doliolum sp. and Cavolinia sp. whilethese species were completely absent in the others. Similar facts showing a different
biological characters by patches have been found in the population of Euphausia
sujJerba (Mackintosh and Wheeler, 1929; Marr, 1962), and these facts seem to be
essential characters widely found in zooplankton swarms.
The average body wet weights also varied between 1.23 and 1.96 mg. throughNos. 1 to 10 patches. However, they showed no parallel relationships to the body
Sci. Rep. Whale Res. Inst.,

No. 26, 1974

FEEDING HABITS OF SEI WHALE

121

length as noticed by comparing the patches Nos. 2, 4 and 8. The patch forming
individuals must be different in their physiological conditions even in the samedevelopmental stages.
It could be considered as a whole that the patches of C. tonsus keep their biological characters each other to some extent, and this means that they do not mingle
each other for some long time, and that they are controlled by some biological
functions to swarm or aggregate themselves, if not the patches and their biologicalcharacters could not be kept so distinctly under the continuous disturbance by strong
winds and smashing waves. Marr (1962) mentioned that patches of Euphausia superba
are maintained for long time through their life span, and rarely found mixed
populations with the individuals in different developmental stages among theidentical patches. Hardy (1967) also confirmed the similar evidence as a functionof strong self-swarming behavior by euphausiids. In the neritic waters, the planktonic larvae of Balanus and Mytilus sometimes show a dense patchy distribution, butthey dispersed over soon after as season proceeds (Raymont, 1963). The patchesof euphausiids, or copepods found in the pelagic waters would be considered different in their biological nature such as socialized function through swarming behavior
as Steven (1961) and Clutter (1969) confirmed it in the patches of mysid fromthose swarms by temporal zooplankton species.

11-10. Possible cause of swarming in zoojJlankton
The zooplankton does not evenly distribute throughout its habitat but distribute quite unevenly as has been known by an actual experience in the North
Atlantic cod fishing grounds. The swarms or the patches of zooplankton could
be seen as one of particularly distinct phenomena of spatial distribution, and thosesighted by C. Darwin in the Antarctic region near to Tierra del Fuego might possibly be the plankton patches (Darwin, 1906). The swarming phenomenon inzooplankton has been documented to some extent by Mackintosh and Wheeler(1929) who studied on the food habits in baleen whales, and also by Hardy (1936a,b) in his investigations by the continuous plankton recorder. Hardy (1936a, b)
also made it clear that the uneven distribution of zooplankton is not so special
phenomenon but rather general characters as a whole, which made him criticise
the recognition of even distribution of zooplankton by Hensen (1890). Through his
studies on the uneven distribution in plankton population, Hardy (1936a, b) called" patchy distribution " or " patchiness " of plankton when they swarmed densely
in a spacially limited region. For example, Hardy (1936a) found patchy distribution of SaljJa longicauda when they densely swarmed with more than 30-50% larger
in their population density to that of the back ground waters. The patchinessas one of a distribution patterns in animals, therfore could be considered a kind ofsociality in animals, and Imanishi (1941) called the theme as specific synusia an
ultimate pattern of population life as widely found in the insect communities.
lmanish (1941) considers these monospecific swarms or aggregations in animal community would be somewhat unusual in their daily life, but the patchy distribution
in organisms itself can also be considered rather usual distribution patterns sinceSci. Rep. Whales Res. Inst.,
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it is widely found throughout both animal and plant kingdoms.
One of the distinct examples of plankton patchiness is known in E. superba
and M. norvegica populations, and they swarm such densely as to make the sea
heavily discolored. It was this discoloration of the sea that has made whalers spot
the whales and whaling ground. The E. sujJerba population under patchiness is
exclusively monospecific composition, and it also clearly formed independently by
the individuals in the same developmental stages (Mackintosh, and Wheeler, 1929;
Mackintosh, 1973). Therefore, the zooplankton swarming into patches differs ina sence from the patchy or uneven spatial distribution. The latter would be widely
found in any kind of plankton communities. The E. sujJerba patches are quite important ecologically since they are voraciously fed by the baleen whales while
none of Sagitta spp. and pteropoda under similar patchiness are fed by the whales.
What whales feed exclusively on swarming organisms which form the patches
indicates that patch formation would be a staple distribution pattern through theevolutional ages since baleen whales must have adapted to develop specialized
apparatus, the baleen or whalebone so as to utilize those patch or aggregation forming organisms.
In the northern North Pacific and Bering Sea, Sagitta, Aglantha and Clione
sometimes show a distinctly larger biomass (Hokkaido University, 1962). In thesouthern seas Sagitta spp. also show a patchy distribution (Hardy, 1936a). However, a bulk of occurrence of these organisms is usually accompanied along with manyother plankton species to show a complicated zooplankton communities though
Sagitta occurs with patchiness. More recently, Wiebe (1970) observed on the small
scale spatial distribution of zooplankton in detail and he called "patchy distribution" against the plankton biomass of about 2.6-5.l times larger than the background, while Kuwahara et al. (1971) definited the patchy distribution as withthe biomass larger than the overall median value in a series of samplings. Thesepatchy distribution as definited above however may be similar but different fromso-called plankton patches by aggregating or swarming of organisms in view of
their community composition.
As it has been mentioned the population density in C. tonsus patches was maintained under somewhere between 10 3 and 10 4 inds./m 3 • These figures would belarger, approximately several thousands to several tenth thousands times than theback ground waters, and this somewhat similar to the case in E. sujJerba (Marr,
1962) and M. norvegica (Mackdnald, 1927) where it was larger about 200 to 300
times. Anyhow the zooplankton patches is quite important ecologically in themarine food chains. For instance, a squid, Nototodarus sloani sloani which distributes
in New Zealand waters feeds on the swarms of both Nyctiphanes australis and
P. gaudichaudii, and Todarodes pacijicus also feeds on E. pacijica (Kawakami et al.,
1973; Kawamura, 1974b). These facts suggest an importance of the plankton
patches other than the case in baleen whales since the squids supposedly distributeover the world oceans with great quantity.
For the convenience of further discussion on the patches in C. tonus, their
biologically important characters are given as follows: 1) a horizontal expansion
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of the patches is at least several hundred meters, 2) the shape is usually recognizedwith the scale in horizontal plane, i.e. stream, round or oval shaped, 3) the patches
and its shape firmly maintanined under a rough sea of 8.0- 10. 7 m/sec in wind speed
and 5 class of waves, 4) patches occur most frequently under the temperature of
13.0- 14.0°C, where distinct temperature gradient prevails, especially in the regions
under varying temperature, 5) higher population density of patches is mostly foundin the surface waters shallower than 1.0 m but some are in more deeper waters, 6) the
population density under patchiness would be 10 3 - 104inds./m3 , 7) the patches arecomposed of copepodite V though sometimes a little number of copepodite IV
and adult female are mixed up, 8) biological characters of patch forming C. tonsus
population are maintained for long period, 9) occurrence of patches varies withtime in a day, 10) patches may show a slight diel vertical movements without any
relations to underwater illumination. Among these characters, 3), 7) and 8) strongly
indicate that the patches are neither formed by random variation in the distribution nor physical conditions of the water but purely biological causes of internal behavior to aggregate themselves.
Various discussions have been stated on the possible cause to make zooplanktonswarm so densely, and the discussion could be divided into three opinions: one ofthem discussed the phenomenon as being a subject of zooplankton or organism
itself, so the environment, have somewhat the secondary importance for it (e.g.
Gurney, 1924; Russell, 1927; Hardy and Gunther, 1935; Watermann, 1958;
Colebrook, 1960a, b ), and the other considers an inorganic environments first suchas current, circulation of the water, underwater illumination which directly influences on the formation of swarms (Fraser, 1936; Bogorov, 1938; Beklemishev,1958), and the third is a combinations of the both above mentioned, and Colebrook(1960a, b) considered the surface swarming in Daphnia hyalina would supposedly
caused by whirling movement of water and swarming behavior of Daphnia itself,
whereas Russell (1927) insisted the purely biological factors of zooplankton toaggregate themselves after his observations on decapod larva. " Localize didtribution" in M. norvegica in the North Atlantic must be due to a seasonal change
in an availability of foodstuff along with being chased by predator and with aneffect by tidal currents. However, when we consider the biological characteristicsof the swarming or patchiness in E. sujJerba and C. tonsus, it does not seem to becaused by environmental conditions such as the current, upwelling, pack-ice and its
melted water but caused primarily only by the subject of those organisms, that is,1) a monospecific composition of swarming population is maintained for long period(Mackintosh and Wheeler, 1929; Marr, 1962), 2) each patches are composed ofindividuals in a definite developmental stages but it would possible to occur two
kind of patches each of which composed of different developmental stages in thesame sea region, 3) orientation of E. superba individuals within the patches is almostin the same direction and the patches are quickly reorganized after disturbance(Hardy and Gunther, 1935), and 4) patches are well maintained through even roughweather.
In this study I sighted at many C. tonsus patches even when the surface wasSci. Rep. Whales Res. Inst.,
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very rough under the wave class 5, say, 8.0-10. 7 m/sec in wind speed. According
to Sakamoto (personal comm.) a theoretical current speed which is possible under
the wave height of 1-5 m would be 62.5-140 cm/sec. Under these circumstances
C. tonsus could not maintain those high population density unless they swim actively
againt to the current. According to Marshall and Orr (1955) the swimming speed
in Calanus was 0.42 cm/sec. in long ascent movement, and 1.32 cm/sec. in descent.
Still more most C. tonsus patches occur in the convergence region where the water
sinks to some extent, which would require to make C. tonsus move upward to keep
their position within the surface layer. However, Jillett (1968) stated that thedense population in C. tonsus would be due to an accumulations caused by somecurrent dynamics, and it is in these points that I disagree with his consideration.
If C. tonsus forms dense swarms or patches not by a envirommental conditions
but by its habits of gathering closely each other into an aggregation, there would
be found some physiological and ecological benefits for them as Allee (1938)
and Lorenz (1963) discussed beneficial effects in many kind of aggregating animals.
The population density in C. tonsus patches was approximately 6X10 3 -2X10 4
inds./m3 though the figures as plankton biomass still much less than E. superba.
However, these above mentioned population density would be enough to make theindividual under the patchiness touch each other while they jostling one another,and the explanation on the plankton swarming by some factors such as the structualfeatures in a column of water, photo taxis, sensory for polarized light and grazing
could not possibly keep the individuals so closely for long time. The antennule
in crustaceans functions as a sensory organ (e.g. Dahl et al. 1970a, b), and the roleof the frontal organ in Calanus, and the setae on the antennule themselves would
function similarly. The stimulation induced by physical contact while jostling would
release the behavior of swimming at least toward the surface (Rudjakov, 1970).
Allee (1938), however, considered the absence of any kind of physical contact in
copepod aggregations, but also suggested their social habits.
Apart from that above mentioned, one of another possible cause being proposed
might be a chemosensory receptors furnished on the antennule although any kind of
the receptor had not known yet in Calanus. However, its presence in brackish water
amphipoda, Gammarus duebeni as receptor for sex pheromone (Dahl et al, 1970a, b)
and in decapod crustacean, Portunus sanguinolentus (Ryan, 1966) must function as
chemotaxis of a gathering attractant. The swarming in crustaceans particularly
under monospecific compositions therefore might possibly benefit as the density
or grouping effects in growth speed and shortening the larval period, such as known
in a kind of cockroaches (Ishii, 1970; Chauvin, 1967) and in oligochaetes (Brinkhurst et al, 1972). According to Ishii (1970) the swarming and settling in a nauplii
of Balanus sp. are controlled by chemical factors though only settling factor has been
known to induce their aggregation and simultaneous settling on the bottom. Stimuli
by physical contact through body touch would make copepods ascent toward surface(Rudjakov, 1970), which may explain the occurrence of densely aggregated C.
tonsus population in the very surface waters. However, since the C. tonsus patches
were found not only at the surface but also at several meters depth, some anotherSci. Rep. Whales Res. Inst.,
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causations to explain these circumstances have to be considered in the future. Bainbridge (1953) indicated the importance of vision and reotactic sence which might
explain the animal aggregations, but it would be still in need of examinations
to appropriate his indications at least on to C. tonsus population and other copepods
since visual sence in these organisms is poorly developed. Learning and practising
behavior found in the fishes may also be difficult to appropriate on to swarmingin zooplankton.
12.

GENERAL DISCUSSION AND CONCLUSION

The behavioral patterns of animals in time and space are so complicated features
as to hardly be understood even their outlines. However, when we consider amovement of animals in view of the population ecology as a whole, they could beapproached to some extent since they were mostly controlled by instinctive behaviorof both breeding and feeding as has been pointed out by Elton (1927), and thewhales do not differ essentially from another mammals but rather simple due totheir seasonal migratory behavior between cold and warm seas. One of the current problems to which the population ecology faces would be to understand thestructure and mechanisms of varying animal populations under the natural andartificial factors which affect on their population along with inter-specific factors.
Food arid feeding habits of animals much influences on the number and size of
population through the marine food web. Elton (1927) suggested an importanceof study on the prey-predator relationships in connection with the animal populations.
In baleen whales a minute crustacean animals had been known early as themain nutritional sources for the whales (e.g. Scoresby, 1820; Collett, 1929). However, it was until recent years that those food habits were considered from the view
points of production ecology in which the secondary producer connected directlywith the last consumer, say, a typically simple but effective shift in energy flows. At
the sametime, the relationships around food would be an important role on controlling the overall population size of the predators such as, say, catch of anchovata and the population of pelican, whale stocks and the abundance of euphausiids(Kawamura, unpublished data). All these are in need of quantitative treatmentin their preypredator relationships. Since the stock of whales is importantamong all, the study on their food and feeding habits have to be proceeded along withthe whales itself.
The sei whale in the Antarctic region distributes along the Subtropical Convergence, and the food organisms in that region are consisted of somewhat simple
zooplankton community although the oceanic conditions differ to some extent between the whaling areas. The important food organisms in the southern sei whaling
ground are: Calanus tonsus, C. simillimus, Parathemisto gaudichaudii, Euphausia vallentini,and E. superba. The shift of whaling ground during a season is mostly to the featuresof the seasonal distribution patterns of food organisms such as disappearance of C.
tonsus from the surface by its depth migration for wintering. In the formation
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of whaling ground the patchiness of zooplankton is important among all, since foodorganisms of whales are restricted in patch forming species. As has been mentioned
in the previous sections, the plankton patches as a whole are distinctly characteristic
population in general distribution and its movements being differed from the individuals outside the swarms. For example, patches of E. sujJerba usually shows diel vertical migrations to some extent (Marr, 1962), while many patches occur in the surface
layer throughout the night (Ivanov, 1970). The ecological importance of plankton
patches would be understood when we consider their biomass as shown in C. tonsus
patches where the biomass was 2 x 10 4 -3 x 10 4 mg/m 3 of water while it was only 25
mg/m 3 in the back ground waters. The patches of C. tonsus usually found under
the temperature of 13.0°,.., 14.0°C whereas the species itself is known to distributeunder wide temperature range of 5.0°,.., 15.0°C. (Brodskii, 1964). The whaling
ground formed by C. tonsus therefore could hardly be recongized only by the characters of its general distribution unless the knowledge on the ecological characters of thepatches was accompanied. The movements of whale within the feeding groundwould be well understood by studying the causations which make the food organisms
densely aggregate into the patches.
In the feeding types of baleen whales the filtering apparatus along with its
mechanisms and the feeding ability were considerably different in sei whale fromthose in blue and fin whales. The sei whale can recognized characteristic in thispoint though all these three belong to balaenopteridae. The baleen plates of sei
whale shows rather slim, and its bristles furnished on the inner margin of baleen
plates are fine as comparable with those of balaenid whales. The meshes which
cover the inner surface of filtering apparatus are quite fine with relatively larger
filtering area among balaenopterid whales. In regard to a selective feeding habits
in baleen whale (Nemoto, 1959; 1970), the sei whale prefers copepods at first theneuphausiids or amphipods in the Antarctic waters though the latter two are replaced one to another by the regions concerned (Best, 1967; Kawamura, 1970a). A
preference to copepods in sei whale also found in the North Pacific where C. cristatus
and C. plumchrus are the staple food (Nemoto, 1959; 1957) although they are replaced by fish and euphausiids in more southern waters (Kawamura, 1973a). The
food organisms of sei whale took over by C. finmarchicus in the North Atlantic (Collett, 1886). A boltering behavior is known well in fin and blue whales (Lillie,
1910; Gunther, 1949) but is less distinct in sei whale. These facts along with thefeeding mechanisms, apparatus, and habits lead to a consideration that the sei whale
is more closely related to right and bowhead whales. Nemoto (1959; 1970) however, thought the sei whale belongs to blue whale type feeding apart from right andgrey whales types. But when the above mentioned circumstances on sei whale
feeding are took into account, its feeding type would be rather much similar to thatof the right whale.
The over specialization such as elongated teeth in narwhal, Monodon monoceros
is usually seen to some extent throughout the order cetacea, and the developmentof the baleen plates could be considered as one of over specialization themselves (Howell, 1930). In this respect the gulping or swallowing type in feeding would be
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more general throughout many animals while the skimming type as employed in sei
and balaenid whales would be an over specialization. As I have assessed in theprevious section, the sei whale ·can collect more abundant foodstuff effectively byskimming the food contained water than swallowing, that is, the sei whale seems tohave aquired skimming type feeding as an more advanced habits for collecting thefoodstuff in marine biotope.
Marr (1962), Moiseev (1968) and several other workers assessed the stock sizeof E. superba being based on the consumption of E. superba by whales. Apart fromthe whales, Ryther (1969) also made an estimation of E. superba production fromthe view point of production ecology by supposing the energy coefficient of 10, 15,
and 20% in the shifts of the trophic level, and criticized the above mentioned method
as out of the discussion. Ryther's methodology itself is one of the subject in production ecology. However, it sometimes leads to a confusion or incorrect conclusions
unless the biological characteristics such as the dietary habits of prey and predator
were took into account. For example, E. superba, according to Barkley (1940) andMarr (1962) preferably feeds on diatoms, Fragilariopsis antarctica, and as a whole itseems to avoid larger or longer sized diatom and spinous diatomspecies. E. superba
likely to strongly avoids the water dominated by Thalssiothrix antarctica (Kawamura,
1973b; 1974). However, the biological aspects of feeding habits such as foodselection are omitted in the method by productivity which involves all of the organiccarbon produced. Hasle (1969) reported abundant distribution of Nitzschia spp.,
Fragilariopsis and Chaetoceros diatoms in the Pacific sector of the Antarctic but they
are supposedly less important as food of E. superba. This fact supports well a poor
distribution of E. superba in that region (Mackintosh, 1973). Marr (1962) considered the gaps or voids in phytoplankton abundance between the waters withrich E. superba patches and those separating the patches would be due to grazing.
The animals which distribute dominantly with the bulk of biomass and usuallyin higher trophic levels likely to prey on zooplankton species particularly thoseaggregate into the patches. These animals, for instance, are anchovata, gonostomatid fishes such as Viciguerria attenuata, Scomberesox saurus, squids, seabirds, crabeater
seal and whales. The role of those animals in the Antarctic ecosystem would be
distinct than any other kind of organisms, but none of them studied yet except
whales, and therefore the knowledge of food habits in those animals is considered
to be strongly in need of further investigations. However, it has been known thatthe southern blue, humpback, minke and fin whales feed almost exclusively on E.
superba though the fin whale utilizes copepods to some extent whereas the sei
and right whales feed copepods preferably, though the latter feeds much on euphausiids other than E. superba and amphipods, P. gaudichaudii. When we take
into account the ecological niche concerning to those prey organisms in quantitative and qualitative respects, it would be possible to suppose an outline of thestructure of the ecosystem in the southern ocean: the organic production in the
Antarctic regions proceeds as a whole under relatively lower trophic levels. Accordingly, the role of zooplankton in the southern ecosystem would be hardly comparable importance than that of any other places, and it seem to be almost imSci. Rep. Whales Res. Inst.,.No. 26, 1974

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possible to understand the ecology such as the movements and the inter specificrelationships among those important predators without studying on the swarming
habits of their prey organisms.
The swarming habits in zooplankton however have been poorly studied particularly in the biological and ecological knowledge except several observations as
an unusual distribution phenomena (e.g. Hardy and Gunther, 1935; Mackintosh,1967). As it has been stated in the previous section, E. superba and P. gaudichaudii
occur in patchiness which would be formed by the individuals of almost every developmental stages. On the other hand the patches in C. tonsus, E. vallentini, and supposedly in many another kind of copepods and euphausiids are formed by the individuals of some particular developmental stages such as the copepodite V in C.
tonsus. The swarming into patches in E. pacijica (Komaki and Matsue, 1958;
Komaki, 1967), The. inermis and 111. norvegica (Bigelow, 1924; Macdnald, 1927)
would be similar to the case in C. tonsus and E. vallentini.
Marr (1962) discussed on the possible cause which make E. superba aggregate
so densely but he did not figure out decisive conclusions after examining particularly
the effects by animal exclusion and the pack ice, and stated that the patchinessseems to spring from the lifelong habit of this species.
In the patchiness of C. tonsus, I have supposed a kind of density effects which
would benefit on C. tonsus not as an individual but a population to be kept staple,
since as mentioned before the aggregating or swarming phenomenon would be thesubject of ethological habits in organism itself. However, the surface swarms ofGalatheid shrimp, Munida gregaria seems to occur under some particular environments such as the depth or the front like structure of the waters (Tabeta and Kanamaru, 1970). Pleuroncodes planipes also swarms in the upwelling region accompanying the oxygen minimum layer (Anonymous, 1971). These facts however would
possibly be a phenomena which seem as if it were the causation for aggregationor swarms, that is, a kind of pseudo-factor, and the patchiness of zooplankton would
be induced purely by biological but still unknown agencies. Komaki (1967) and
Kawamura (197lc) have pointed out that the development or occurrence of socalled patches by swarms would hardly be forecasted by the figures of ordinal
physico-chemical environmental factors, that is, the swarming of zooplankton differs
essentially from the red tides.
Mackintosh (1967) stated on the behavior of E. superba patches that eachswarming individuals showed a synclonized swimming as if there were some leader
particularly in command of the whole. Their behavior as mentioned above
would be similar to " following reaction " in fish schools, which was proposed by
Crook (1961). In the school of scombid fishes, the distance separating each individuals and the movements of the tail flukes are the important factors to keep
the school tightly (Olst and Hunter, 1970). They (Olst and Hunter, 1970) also
found that the school was specially well kept tightly when the distance between
each fishes were one half of their body length. The population density in thepatches of E. superba and E. paci.fica show one individual per cubic inch or thereabouts(Marr, 1962; Komaki, 1967), and these facts make us suppose that the swarming
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in euphausiids would be similarly understood though the distance between theindividuals within the patches must be more important in euphausiids than the fishes
since visual sence is poorly developed in the former.
In the population of insects the density effects usually function in controlling
the population size (Ito and Kiriya, 1971), but it is also known in some insect
species that the density effects would be benefitial for promoting the relative growthrate by shortening the intervals between individuals, in which the density effects
make each individuals shorten their larval period being induced by the promoted
secretion of the moulting hormone possibly induced by tactile stimuli (Ishii, 1970).
The density effects are particularly more strongly functional in the earlier stages of
insect species (Chauvin, 1967). This fact indicates something analogy with thecase in swarming C. tonsus population composed of the copepodites IV and V, andalso the case in some temporal plankton species.
On the study of zooplankton patchiness, the followings are particularly hoped
to be known in the future: the geographical and the vertical distributions, theseasonal change, change within short time period, population density and its
structure, and the causations which trigger the behavior of swarming. In thisstudy a small underwater plankton sampler (Motoda, 1959) was used in collecting
C. tonsus patches, but the sampling gear seemed to be insufficient for the purposeof quantitative study since population density varied distinctly even within a patch.
In this respect the continuous plankton recorder which revealed clearly the uneven
distribution of plankton (Hardy, 1936a, b) must be revaluated. Wiborg (1971),
on the other hand, found the population density of 4000 inds./1000 m 3 in Th. inermis
and 5000 inds./m 3 in Th. raschii by towing the IKMT, and he (Wiborg, 1971)
considered these high population density would be due to their patchiness. Omori(1965) and his colleagues (Omori et al., 1965; Kawaguchi and Mammo, 1967;
Kawaguchi, 1973) have successively used the large sized ring net of 160 cm mouth
opening for collecting the micronektons, and proved that the net was considerably
effective for patchily distributed organisms such as Sergestid shrimps (Omori,1969; Omori et al., 1972). These facts suggest that the larger sized towing net
in its mouth opening would be more successive for collecting the fast moving orvery locally swarming organisms.
SUMMARY

1. The food and feeding habits in southern sei whale, Balaenoptera borealis
Lesson, which was caught during 1967/68 to 1971/72 seasons by the Japanese
floating factories were studied. The observations were chiefly focussed on the distributions of prey organisms by species through which the formation of whaling(feeding) ground was considered biologically. One of another focusses was to figureout a comparative structural characteristics of the feeding apparatus along withthe dietary habits in sei whale in connection with the patchiness of prey organisms.
2. The sei whaling ground in recent operations is found in the mid latitudesof the circumpolar seas, say, the Subantarctic waters of 40° ....... 50°S, where more
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than 70 %of sei whale have been caught among all. The formation of sei whaling
ground is closely related to the Subtropical Convergence, and the most important
areas are the Indian and the western part of the Pacific sectors between 0° and
170°W.
3. The general hydrological conditions of the whaling ground was as follows:
the favourable surface sea temperature was somewhere between 14.0°C and 18.0°C
during December though it was 8.0°C- 10.0°C by some whaling areas. As season
proceeds the whaling ground shifts to higher latitudes where the temperature was
14.0°-16.0°C in January, 7.0°-10.0°c in February and then 4.0°C-7.0°C in
March. The isotherm recede toward north with the speed of about l .0°Cf l 0
lat./month in the region concerned.
4. A total of 23 species or more of food organisms were found in the stomach
contents of sei whale, and the following 8 species were most important components:
Calanus tonsus, C. simillimus, Clausocalanus laticeps, Drepanopus pectinatus, Parathemisto
gaudichaudii, Euphausia vallentini, E. lucens, and E. superba. There were 7 species offood organisms, C. tonsus, Cl. laticeps, Thysanopoda actifrons, E. diomedeae, E.
lucens, Penaeus sp. and Scomberesox saurus which were newly known in this study as thesei whales food in the Subantarctic feeding ground though both E. diomedeae and E.
lucens had been known as sei whales food in the South African waters.
5. The composition of the stomach contents was monospecific in more than
72 % of the animals examined, and those of mixture with two or more species wererarely found. It was indicated from this fact that sei whale feed on the prey which
had so densely swarmed as to form the patchiness. Doliolum, Salpa, pteropoda andchaetognatha distribute abundantly in the region concerned, but none of themwere the important components of the stomach contents. A selective feeding habits
by species and size of the prey organisms were also observed in sei whale as has
been known in fin whale. The sei whale feeds preferably on crustaceans than any
other kind of foodstuff, and copepods were the most important among all. C. tonsus
of copepodite V stage was the main food species in the southern waters.
6. The distribution of the food organisms changed latitudinally: C. tonsus,
C. simillimus and Clausocalanus laticeps were the main composition of the stomach
contents throughout the zone between the Subtropical Convergence and about
4 7°S, although they were took over by E. vallentini or P. gaudichaudii by the sea regions, and then by P. gaudichaudii almost exclusively between 50°S and the Antarctic
Convergence. It was only E. superba that occurred in the stomach in the southern
most whaling ground close to the Antarctica. These geographical change in thecomposition of stomach contents was a phenomenon which occurred within a narrow zone of 20 degrees in latitudes.
7. In the feeding percentages in terms of the number of animals with foodagainst those examined, 28-59 % of animals in the Indian sector had carried thestomach contents whereas it was 25--82 % in the Pacific sector, and the availabilityof foodstuff would be considered higher in the Pacific. The scheme above mentionedby species was also varied with the whaling areas, that is, both C. tonsus and E. vallentini were dominant in the Pacific sector, while P. gaudichaudii and E. superba were
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important food in the Indian sector and in the Tasman Sea area. However,preference to the kind of foodstuff in sei whale was focussed first on copepods and,euphausiids and amphipods were secondarily important. The feeding percentage
by the species and seasons revealed that there might be both copepod rich year,
and euphausiid or/and amphipod rich year.
8. Sighting investigations revealed that both baleen and toothed whales seem
to take food even in the tropical seas, especially where upwelling along with abundant distribution of zooplankton prevails. The region of a relatively dense distribution of whales was indicated particularly by the distribution features of salinity andphosphate.
9. The sei whaling ground agrees on the whole with the abundant distribution of their food organisms particularly of C. tonsus and C. simillimus. Apart fromthis however, there was a local but abundant distribution of food organisms such
as D. pectinatus and Cl. laticeps, and the whaling ground formed by these foodstuff
hardly be spotted since there was no effective ways left behind to know very local
occurrence of the plankton patchiness by plankton net haul.
10. C. tonsus population is composed of copepodite stages IV, V, and adultfemale, but the population is represented by copepodite V since it occupied 89. 7 %on
average in overall compositions in individual numbers. There were two size
compositions of the copepodite V, say, 3.0-3.2 mm and 3.5-3.6 mm by the whaling
areas, and they were supposed to be the difference due to isolation by breeding
stock, and also the difference in generations.
11. The feeding ability in sei whale is a function of the mandible size which
grows proportionaly with the body length. However, the filtering structure infeeding mechanism is the row of baleen plates which furnished on the upper jaw withthe average density of 1.4 plates/cm near the rostrum and 0.93 plates/cm at the
distance of 66.4-69.5 % posterior from the rostrum where the baleen plates attainat their maximum length. The length of the bristles furnished on the inner marginof the baleen plates varied 3,...,5 cm with the averaged density of 45.5 bristles/cm
regardless to sex and body legth.
12. The total area of the filtering apparatus in sei whale was 2.37 m 2 in
11.0 m long animal, and 3.59 m 2 in 14.4 m animal. None of sexual variations
were observed. The area of filtering apparatus against the body length showedcomparatively larger figures in sei whale than the another balanopterid whales
though it was still smaller than that in balaenid whales.
13. The calculated porosity of the filtering apparatus varied between 77.2 %and 88.6 %. Comparing with the figure of 46 % in GG54 bolting silk cloth (0.33mm mesh apertures), the netting in sei whale was considerably coarsely structured
but its relative filtering ability was 1/8 of the GG 54 and 1/5 of the fin whales.
14. The number of animals which vomited the stomach contents duringchasing against the total animal observed were 6/642, 1/129, and 21/125 in theorder of sei, fin, and sperm whales respectively. This fact makes us confirm thatthe amount of stomach contents found in carcasses shows an actual figures at the
moment of animals being killed.
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15. By examining the fulness of stomach contents, it was known that 25-30 %of the stomach contents in volume reduces within the following 5-6 hours supposedly by digestion. This fact leads to tt consideration that the stomach of sei
whale would be repleted fully once in a day.
16. The amount of stomach contents which were actually found in carcasses
was 150-200 kg, 500-600 kg, and 30 kg in the order of sei, fin, and minke
whales respectively. These amount of food however, seems to be far insufficientas the daily rations of the whales. When C. tonsus was fed by sei whale its amountusually found in the stomach does not exceed more than 50-60 kg. This would
be due to a poorer availability as biomass in C. tonsus even when they form thedensely populated swarms than the case in larger sized prey organisms.
17. Feeding activity in sei whale as indicated by the feeding percentages
was high in the morning, but in some case it was unchanged throughout the day.
This suggests that many sei whales feed much once in a day, but they have to preyon continuously throughout the day to fill their daily rations particularly when
they feed on copepod. The habits of the diel vertical migration in prey organisms
also affect on the whale's feeding activity.
18. After the formulations by Sergeant (1969), the theoretical daily rationsin 3 species of the baleen whales were calculated as 4.4 %, 4.07 %, and 3.84 % ofbody weight in the order of sei, fin, and minke whales respectively.
19. The population density in C. tonsus patches was assessed being basedon the filtering ability, feeding habits, and the amount to stomach contents; andfound that C. tonsus swarms into patches with the population density of 103 -10 4
inds/m 3 • In these calculation it was also indicated that the sei whale can collectthe foodstuff more effectively by employing skimming type feeding than the caseby swallowing type.
20. A total of 220 patches of C. tonsus was investigated, and the following
evidences were found: 1) the patches showed spindle-, oval-, and stripe- or streamshape, of which the former two occurred most frequently, 2) the size was usuallysomewhere between hundred and several hundreds meters in their longer axis
though sometimes it was several miles long in stream-shaped patches, 3) the patchis maintained tightly for long period through rough weather, and each patches
are so completely isolated as to keep the overall biological characters as aggregatedpopulations, 4) the patches occurred most frequently along the Subtropical Convergence where the sea temperature was 13.0°-l4.0°C, 5) copepodite V of C. tonsus
population forms the main body of the patches with slight numbers of adultfemale, 6) the observed population density in collected samples varied between
330 inds./m 3 and 2.4x 104inds./m3 (=3X10 4 mg/m 3 ). These figures agreed withthose assessed theoretically, 7) possible causations of swarming behavior would
be the density effects which supposedly benefits to growing larger the population
as a functions of stimulation by physical contact of one to another, and then, 8)
the formation of patchiness would hardly be explained by the hydrodynamical
forces because what makes the organisms swarm or aggregate so densely would
be, after Cassie (1960), a internal behavior patterns between individuals of theSci. Rep. Whales Res. Inst.,.No. 26, 1974

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133

same species through a social habits, that is, the subject of organisms themselves.
ACKNOWLEDGMENTS

During the course of this study Prof. Teruyoshi Kawamura of the Faculty ofFisheries, Hokkaido University gave me an encouragement and valuable criticisms,
to whom I would like express my particular appreciation. I am also greatly
indebted to Prof. Tokimi Tsujita, Prof. Shun Okada, Associate Prof. Takashi Minoda, and Dr. Akira Taniguchi of the same university who have read and given
much instructive advice and comment on the original manuscript.
I wish to express my gratitude to Dr. Hideo Omura, Director of the Whales
Research Institute, who not only admitted my long research cruises down to the
Antarctic in 1967/68, 1968/69, and 1971/72 seasons, but also gave me well-timed
convenience and opportunity throughout the study. My colleagues, Mr. Saburo
Machida and Miss Yuko Satake of the same institute also assisted my work andgave the facilities.
Thanks are also due to Mr. Yoshio Takato of the Fishery Agency, Ministoryof Agriculture and Forestory at that time who admitted my participation to the
Antarctic whaling operations as a government inspector in 1967/68 season, throughwhich I started the present study, and Messers. Mitsuaki Kosaka and Kineo Kegasawa of the same agency who were on boad of the floating factories in 1967 /68 and1971/72 respectively gave me a helpful convenience for my work on the ship's deck.
One of my sources in obtaining the samples of the whales food was due to the kindarrangements of Dr. Seiji Ohsumi and his colleagues, Messers. Yasuaki Masaki
and Shiro Wada of the Far Seas Fishery Research Laboratory, Fishery Agency in
Shimizu, to whom I would like to extend my appreciation. In connection with
this, the collection of food samples in the field was made fruitfull by the kind arrangements and co-operations of the following companies and their personnel
concerned: Taiyo Gyogyo K.K., Nippon Suisan K.K., and K.K., Kyokuyo.
My participation to the R. V. "HakuhO Maru" Cruise (KH-68-4) to the
Antarctic was due to kind arrangements by Prof. Masaharu Nishiwaki and Prof.
Yoshio Horibe of the Ocean Research Institute, University of Tokyo, and Mr.
Kazuo Kureha of the same institute greatly assisted me in whale sighting andplankton sampling during the cruise. Without their helpful arrangements andco-operations I could not discuss on the population density of food zooplankton
and the formation of whaling ground. I am also greatly indebted to Mr. Ken
Ohturu, Capt. Teruhiko Furuno of the Nippon Suisan K.K., and Capt. Yuzo
Masumoto of the Hokoku Suisan K.K. who gave me an opportunity and convenience for investigating the disbribution of food organisms in the southern whaling ground in 1971/72 season.
One of my particular thanks is due to Prof. Toshiro Kuroki, Drs. Kouichi
Kawaguchi and Wataru Sakamoto of the Ocean Research Institute, University ofTokyo, who gave me many valuable advices and co-operated in constructing the apparatus for experimenting the filtering ability of a row of baleen plates. The exSci. Rep. Whales Res. Inst.,
No. 26, 1974

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periment in the field on boad of the R. V. "Tansei Maru" would have been impossible without judicious arrangements by Prof. Ryuso Marumo, Assoc. prof. Takahisa Nemoto and Dr. Makoto Omori of the Ocean Research Institute, Universityof Tokyo. Discussions exchanged at times with Drs. Keiji Nasu and Seiji Ohsumiof the Far Seas Fishery Research Laboratory, particularly on the formation of
whaling ground and feeding habits of whales were much instructive throughout
this study.
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MACKINTOSH, N. A., 1966.

The swarming of krill and problem of estimating the standing stock.

Norsk

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

139

Hvalfangst-Tid., LV, 11: 113--116.
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KAWAMURA

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Note:

References written in Japanese are idicated by parentheses.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

FEEDING HABITS OF SEI WHALE

APPENDIX.

Species
No.
of
whale
sei
sei
sei
sei
sei
sei
sei
sei
sei
sei
sei
sei
sei
sei
fin
-fin
fin
fin
fin
minke

2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20

143

AMOUNT OF FOOD FOUND IN THE FIRST STOMACH OF FIN, SEI AND
MINKE WHALES CAUGHT IN THE SOUTHERN OCEAN.

Sex

Body
length(m)

Kind ofstomachcontents

Date
of
catch

Time
of
catch
(SMT)

Net
weight
of
food
(kg)

Water
(kg)

M
M
M
M
M
M
M
M
F
F
F
F
F
F
M
M
F
M
F
F

14.4
14.1
14.2
14.6
15.2
15 .1
14.7
15.1
13.0
13.2
14.3
14.7
15.6
16.2
18.6
21.0
20.2
21.1
22.1
8.0

Calanus
Amphipoda
Amphipoda
Amphipoda
Amphipoda
Amphipoda
Eu-L
Eu-S
Eu-L
Eu-S
Eu-L
Eu-S
Eu-L
Eu-L,M,S
Eu-L
Eu-L
Eu-L
Eu-L
Eu-L
Eu-L

28/XII/67
6/1/6815/I/68
30/XIl/67
7/1/6815/1/68
21/Il/68
13/1/68
23/II/68
12/I/68
22/11/68
12/1/68
23/11/68
18/1/68
21/1/68
2/111/68
21/Il/68
20/Il/68
21/1/68
21/1/68

1115
0600
0800
1105
0925
1455
1050
1345
0830
1940
0925
1745
0540
0855
1015
0820
0550
0640
1115
1805

54.0
136.5
73.5
98.0
200.0
57.6
142.0
149.6
149.0
135.6
128.7
79.1
148.0
159.0
273.7
785.0
556.5
286.0
127.4
22.4

14.0
18.1
14.5
30.0
28.0
13.8
0.0
28.6
33.0
24.4
12.6
15.4
4.0
37.5
27.6
100.0
10.5
28.0
5.6
4.0

Total
weight of Total
stomach volume
contents
(1)
(kg)
68.0
154.6
88.0
128.0
228.0
71.4
142.0
178.2
182.0
160.0
141.3
94.5
152.0
196.5
301.3
885.0
567.0
314.0
133.0
26.4

66 1 >
171 2 >
109 3 >
1560
312
93.6
200
2204)
200
204 4l
1805)
119
200
255
391 5)
!OOO
700
4005)
238
31.2

Calanus : Calanus tonsus, Amphipoda : Parathemisto gaudichaudii, Eu-L or -M: Euphausia supera, Eu-S :Euphausia vallentini.

1) Approximate values, 2) Estimated by the stomach volume averaged on 13 whales, 3) Calculatedby the mean weight of a unit volume of amphipod food from four animals, 4) Calculated by the mean
weight of a unit volume of small-sized euphausiids taken by #12 animal, and 5) Calculated by themean weight of a unit volume of large-sized euphausiids taken by six fin whales and one minke
whale.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

KAWAMURA

144

EXPLANATION OF PLATES.
PLATE I
Fig. 1. Inside view of a row of baleen plates in sei whale, female, 14.3 m.
Fig. 2. Same as Fig. 1, but viewed from outside.
Fig. 3. Enlarged view of a row of baleen plates showing the intervals of the plates
neibouring with each other.
Fig. 4. Bristles furnished along the inner margin of baleen plate.
PLATE II
Fig. 1.
Fig. 2.

Bristles at the tip of baleen plate.
Enlarged view of the filtering meshes formed by the baleen bristles.
PLATE III

Fig. 1. An apparatus for measuring the filtering ability of a row of baleen platesof the sei whale shown in PLATE I.
Fig. 2. Same as Fig. 1, but small fraction of a row of baleen plates is attached on
the apparatus.
Fig. 3. Frontal view of the apparatus. Bridles and a flow-meter mounted on
the apparatus are shown.
Fig. 4. Flow-meter and the baleen plates attached on the bottom of the apparatus
are shown.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

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BODY SCARRING ON CETACEA-ODONTOCETESCHARLES McCANN
8 Kiwi Street, Heretaunga, H. V., New Zealand

ABSTRACTAn attempt is made to give some interpretation to the numerous andvarious scars found on the exterior of Odontocetes. Some of the scars are theresult of male contests; firstly, in play, establishing superiority, inter se, between
young males, and secondly, in the more serious combats to establish final
mastery in anticipation of the breeding season for possession of an harem. Other
causes of scarring are also discussed.
INTRODUCTION
Opinions vary in attempts to explain the cause or causes of scars frequently visibleon the body of the various species of Odontocetes. The scars may be ascribed tomultiple factors, such as: parasites, epizoans, predators (other cetaceans, sharks
and perhaps seals) and most of all to play and combat inter se. Dealing with thelast mentioned factors first, it is important to consider the behaviour pattern ofeach species and the differences between the sexes and the type of armament (teeth)in each species. A consideration of the play and battle scars is a good indicationof the extent of pugnacity exerted by the males of the species.
Most of the Odontocetes live in small or large schools. The size of the school
varies largely with the annual cycles of breeding, feeding, and migration. Similar
patterns are observable among land animals, as, Bovidae and other gregarious mammals; even among the primates (monkeys).
Bulls (males) engage in much combat inter se: at first the young in play,without inflicting much serious bodily harm, but with advancing age and eventual
sexual maturity, the play turns to greater violence and increase of scarring-it is
no longer sparring. It is in the young male schools that the future master bulls
establish their superiroity over all other bulls and finally become the prospective
masters to challenge the ruling masters and fight to the finish or the vanquishedbreaks off thF fight, perhaps, if not too badly wounded, to return to the fray atsome dista1 · ture or perish on the waves. In the case of an old master, once
he is defeated 1-i.e may survive for a while and lead a solitary existance, or succumb
to his wor
The form of the scars varies with the violence of the attacks and the extent
of contact of _,_1e teeth made at the time of impact. Many of the scars appear tohave been ugly wounds originally. Frequently, the wounds appear to be restricted
to the depth of the blubber alone, but deeper wounds result in fractured ribs anddamaged internal organs. Sometimes multiple fractures appear on the same rib
Sci. Rep. Whales P" Inst.,
No. 26, 1974, .
55
0

146

McCANN

when skeletonised. The fractures not being of the same age show the enduranceof the animals.
In considering the various forms of scars it is essential to refer to the dental
characters, food and enemy cycles. Few Odontocetes can open the mouth widely,hence the size of the food is restricted or of soft consistancy. This observation
appears to have some bearing on the form of the battle scars, as we shall haveoccasion to note.
All illustrations showing body scarring were drawn by me.

PHYSETERIDAE: (Figs. 1 and 2)
Both the genera in the Physeteridae have markedly undershot jaws containing
grasping teeth in the mandibles alone: when corresponding teeth are developedin the maxillae, they are invariably abortive and functionless. The food consists
almost entirely of cephalopods-animals with a slimy gelatinous texture. The
sharp teeth in the mandibles form a most efficient set of grasping teeth against theFig. 1. Physeter catodon Linn.
dorca crassidens Owen.

Fig. 2.

Kogia breviceps Blainville.

Fig. 3.

Pseu-

corresponding sockets in the maxillae left by the ' absent ' teeth. The tongue isrelatively short. Another remarkable feature of the family is the greatly enlarged
head with its enormous ' sac ' of spermaceti, particularly in the Sperm Whale, Physetercatodon Linn.

Physeter catodon Linn. (Fig. 1)
The enormous head of the Sperm Whale occupies almost one third of thetotal length of the animal. It is provided with the cushion of spermaceti, a waxy
looking substance already referred to. To speculate, this 'cushion' functions as
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

BODY SCARRING ON ODONTOCETES

147

a shock-absorber when the animal uses its head as a battering ram in offence anddefence. In addition, the array of large teeth serve as weapons of defence andoffence, and their function as grasping organs in dealing with the large slitherycephalopods (particularly, the Giant Squid) which form a large proportion of thefood of Sperm Whales.
In dealing with some of the larger cephalopods, there seems to be a suspicion
that the Sperm uses its head to pummel the squids after grasping them with its
jaws (the fleeing squid, going backwards as is its wont, would be grasped by its
tentacles). Evidence of battles with large cephalopods is impressed on the facial
region of the Sperms. The use of the head as a battering ram is well authenticatedin literature.
The use of the teeth in sparring and more serious battles inter se is exhibitedby the linear scars on the head and body of opponents.

Kogia breviceps Blainville (Fig. 2)
The Pigmy Sperm Whale is similar in some respects to the true Sperm Whale,
but it lacks the greatly exaggerated head. However, it possesses a small sac of
spermaceti which very likely serves a similar function to that met with in the larger
Sperm Whale. Its food consists largely of cephalopods. The sharp teeth in thelower mandibles only play role of grasping organs and of weapons of offence anddefence. Dental scars appear on both the head and body of the combatants. The
jaws appear to be used 'pigwise ', the scaring depending on the number of teeth
making contact at the time of impact.
DELPHI.NIDAE: (Figs. 3-10)
The Delphinidae are all provided with large or small teeth in both jaws, inboth sexes: the number and size vary according to the species. In some species
the anterior- and posterior-most 1-4 teeth are frequently unerupted. This peculiarity may lead to a variation in the field count. The form of teeth is a fair indicationof the food-mainly fish and cephalopods; the larger species, such as the Killer
and False Killer Orcinus (PI. I) and Pseudorca supplimenting their diet with larger
animals -seals, oceanic birds and chunks torn out of other whales.
Delphinids cannot open the mouth very widely hence true biting is limited
when faced with large objects (i.e. biting dog-fashion). However, dental scars, ofno great depth, are frequently visible, inflicted by an opponent's teeth in ' play 'or combat. These scars represent the dentition of one side of the lower jaw (mandible) only, they vary in number according to the number of teeth that madecontact at the time of the impact. The movement of the jaw is somewhat likethat of a pig when attacking an opponent. This form of scar is frequently seenon the head and body of stranded animals (males): Tursiops, Grampus, Lagenorhynchus,
Delphinus, Cephalorhynchus, Pseudorca, Globicephala, and Orcinus.
It is well-known that the delphinids are far more gregareous and 'playful'than most other cetaceans; also, that many of the species are capable of high speeds,
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

Mc CANN

148

Fig. 4. Grampus griseus Cuvier.
Orcinus orca Linn.

Fig. 5.

Globicephala melaena (Smith).

Fig. 6.

-· ·· ...

.

Fig. 7.'·_.ff" .

::..~_:_./~~-,- .

,....-'

Fig. 7. Tursiops truncatus Montagu. Fig. 8. Delphinus delphis Linn. Fig. 9.
Lagenorhynchus obscurus (Gray). Fig. 10. Cephalorhynchus hectori Breneden.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

BODY SCARRING ON ODONTOCETES

149

avoiding collision and attacks, but likewise capable of inflicting wounds on one
another whether in ' play ' or sexual combat. Scars arising form other causes, suchas epizoans and external parasites, are not frequent with delphinids, this may beascribed to the high speed which enables the surface of the body to remain clean.

ZIPHIDAE: (Figs. 11-22)
Scarring is more prevalent and pronounced among the ziphioids than thedelphinids. This marked difference between the two families may be explainedby the peculiarity of the dentition; smaller schools and slower speed than delphinids. Smaller schools undoubtedly give rise to a greater competion for the masteryof the harem., particularly, during the breeding period. Ziphioid males alone

Fig. 11. :(,iphius cavirostris Cuvier.
Berardius arnouxi Duvernoy.

Fig. 12.

Hyperodon planifrons Flower.

Fig. 13.

erupt specialized teeth for defence and offence. Teeth are found in the corresponding positions in females as those of the male but they are small- and unerupted.
However, there is one exception to this general rule, Tasmacetus, which, in addition
to the enlarged paired teeth possesses a series of smaller teeth (delphinidwise) inboth maxillae and mandibles. Occasionally, one might find rudimentary teeth
in the maxillae which are not embedded in the bone: example Mesoplodon.
In addition to the forms oflinear scarring on males of Ziphidae descirbed above,
ziphioids carry other forms of scarring common to both sexes. The commonest
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

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Mc CANN

forms of scarring being oval, elliptical or even circular. These white scars are to
be seen on almost any part of the head or body, including the flukes and flippers,
but they are most concentrated in the vicinity of the anal and genital regions.
These scars appear to be inflicted by prolonged attachment of some stercophagous
epizoans, such as, sucker-fish (Remora) or crustaceans. Some of the circular scars
may be attributed to lampreys or hag-fish, however, the last mentioned I would
regard as parasites. That the culprets which inflict the scars are seldom, if ever,(I have never come across them) taken still adhering to the carcases of stranded
individuals is quite understandible. (Hag-fish will be attracted to a carcase
during the process of cutting it up, if in a suitable depth of water.) The relatively
slower speed of ziphioids evidentally permit of prolonged attachment of these creatures to the whales, sufficently long to scar the delicate texture of the whale ' skin '.
I have examined many such scars and found that there was no evidence of themhaving penetrated to any great depth below the skin.
To the forms of scars described above attention must be drawn to scars inflicted by the jaws of large fish (sharks) marine mammals (seals?) and some of
the larger Delphinidae, such as Killer Whales (Orcinus).

Fig.140,,:"'"'·'~·~·:..·,:)/·,;";,,,·.·.·.·~~~=---

Fig.15

Fig. 14. Mesoplodon ginkgodens Nishiwaki & Kamiya (After Nishiwaki et al.,1972). Fig. 15. Berardius bairdi Stejneger (After Omura et al., 1955).

:C,iphius cavirostris Cuvier
This almost cosmopolitan species, like so many males in the family Ziphidae,
is virtually toothless except for a pair of defensive in the mandibles, erupted in
the males alone used in sparring or battling with other males. The corresponding
in the females are usually abortive and remain unerupted. The males appear tobe very pugnacious inter se if one may draw conclusions from the numerous scars
inflicted on each other by rival males. The scars appear as parallel wheals indiSci. Rep. Whales Res. Inst.,
No. 26, 1974

BODY SCARRING ON ODONTOCETES

151

eating, in the case of ,Ziphius, that both teeth make contact together normally. The
wheals are often of considerable length Pl. VI, fig. 2 and Pl. VII, fig. 1.
The food consists largely of squids. The tongue and palate are sufficently
roughened with small papillate projections to secure the soft, slithery textures, suchas cephalopod's.

MESOPLODON: (Pl. VI, fig. 2 and Pl. VII, fig. 1)
Excepting M. mirus, which has its defensive teeth at the extremity of the mandibles, like ,Ziphius, all the other species have the defensive teeth at the side of themandibles. Accordingly, I presume that M. mirus alone of the Mesoplodon would
inflict parallel scars on its opponent. Unfortunately, the only good photographI have does not show any scarring. The other member of the genus: Mespolodon
gervaisi, grayi, layardi, stejnegeri, densirostris and ginkgodens inflict single linear scars
at a time on their opponents.

. .. .-•"'·"·>'·•·>-··.·=--~··,.······~:··

Fig. 16. Mesoplodom gervaisi (Deslongchamps). Fig. 17. Mesoplodon mirus True.
Fig. 18. Mesoplodon grayi Haast. Fig. 19. Mesoplodon layardi Gray. Fig. 20.
Afesoplodon densirostris Blainville. Fig. 21. Mesoplodon stejnegeri True.

HYPERODON:There are two known species in the genus. The males of the species possessa single tooth at the extremity of the mandible, in some respects it resembles thatof ,Ziphius, but may be distinguished from it by its larger size and somewhat different
shape. Under the circumstances, I would expect similar parallel scarring but I
Sci. Rep. Whales Res. Inst.,
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152

Mc CANNhave not seen either of the animal in the flesh nor have I seen suitable photographs
showing the scars. However, I presume there would be a greater distance between
the lines in Hyperodon than in Ziphius.
As the female ziphioids seldom carry 'battle scars' it may be concluded thatthe males alone do all the fighting and in the melee may, perhaps, scar a female
accidently, which happened to be in the way.
The position of the ' battle-teeth ' in the mandibles and their shape varies
from species to species: the teeth may be at or near the extremity of the mandibles: between the extremity of the mandibles and the symphysis, or, yet again,
nearer the angle of the gape: The wheals made by the ' battle-teeth ' are almost
characteristic of the species. The species with the ' battle-teeth' at the extremityof the mandibles produce long or short single or double parallel scars equel to the
distance between the teeth, as in the case of Ziphius cavirostris, Mesoplodon mirus
and Hyperodon spp. Species with single teeth in each mandible at, or posterior to
the symphysis inflict deep snort or long linear scars; parallel scars may occasionly
appear by accident-Mesoplodon grqyi, M. layardi and others produce linear scars.
Then there is Berardius with two teeth in each mandible, one large anterior
one and a smaller one a few centimeters behind. Close examination of the carcaseof B. arnouxi and illustrations of the Japanese, B. bairdi resulted in the observationthat parellel scars do not appear to be inflicted by the two anterior teeth as in thecase of Ziphius, however, parallel scars appear which are made by both the teethof the same mandible, with this difference: the anterior tooth makes a larger anddeeper rip than the smaller: the parallel distnace between the scars being muchless than the distace between the two anterior teeth alone. This indicates that
Berardius fights in much the same manner as do the side-toothed Mesoplodon.
Finally, there is Tasmacetus. I have already drawn attention to its peculiar
dention. It is a rare species and no suitable specimens nor photographs havecome my way to make suitable observations on the scarring met with in this species.

BERARDIUS: (Fig. 15, Pls. IV and V)
There are two known species of Berardius.

The males of Berardius unlike themales of other ziphoids possess two defensive teeth in each mandible: one large
tooth followed by a smaller one, a short distance to the rear of the leading tooth.
Reading the scars as they appear on the males of the individuals, three different
patterns of scarring are made: a) parallel rips made by the two leading teeth alone,similar to those observed in the case of Ziphius: b) parallel scars, one more pronounced than the other, and closer together than those made by the leading teeth.
This second form of parallel scarring is produced by the two teeth of the one mandible raking the body of the opponent at the same time, independently of the second
mandible-" pigwise ". In addition to these parallel scars, single linear scars
may be seen gouged out by the leading tooth of one mandible alone. Further,scars similar to the segment of a wheel with short spokes, appear above and below
along the ventral and dorsal margins of the caudal region. These scars appear
to be inflicted large sharks or Killer Whales.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

BODY SCARRING ON ODONTOCETES153

TASMACETUS: (Fig. 22)
This curious ziphioid is rare and little is known of it. Unlike any otherziphioid T asmacetus possesses functional teeth in both upper and lower jaws inaddition to the defensive teeth usually present in the mandibles alone. Oliver(1937) records 19 teeth in each maxilla and 26 (27) teeth in each mandible plus
one large defensive tooth bringing the total number of teeth up to 93. (Mesoplodon grayi has been known to produce rudimentry teeth in the maxillae occasionally. Such teeth have no sockets but are merely imbedded in the 'gums'.)

..·

·~:

~=__,_.,~ 'i\'Fig. 22.

Tasmacetus shepherdi Oliver.·

Under the circumstances I would suspect that the defensive teeth at the exextremity of the mandibles produce similar parallel scars as do other ziphioids
with similarly positioned defensive teeth. In addition, I would suspect that following teeth would produce smaller scars, perhaps similar to some of those madeby some delphinids. At the moment the subject must remain speculative.

PLATANISTIAE: (Fig. 23)
This small but curious family of cetaceans embraces three genera, the distribution of which is no less curious: lnia (Amazons), Pantaporia (River Plate) and
Platanista (largest rivers of India, including Pakistan: Ind us, Ganges and Bramaputra ). In all cases the animals inhabit the muddy estuaries. In response to
the opacity of the muddy environment, the members of the family have little orno v1s10n. Many other adaptations have been evolved but their discussion here isbeyond the scope of this paper. I will restrict my comments to the Indian species,
because of the recent work done on the species by Japanese workers and my personal knowledge of some of the terrain of the species. However, I must confessthat I have only seen skulls but not an animal in the flesh.

PLATANISTA:A characteristic of Platanista is its prolonged maxillae and mandibles provided
with numerous grasping teeth, like Delphinus. These sharp teeth, like those ofDelphinus and Lagenorhynchus, leave scars similar to the series visible on the headSci. Rep. Whales Res. Inst.,

No. 26, 1974

154

Mc CANNand body of the two species mentioned above whether made in ' play ' or more
serious combat. Such scars are clearly visible in the illustrations by Kasuya(1972), Pl. III. In addition to the normal form of scars inflicted on one another,other scars and wounds appear on the snout and ' face ', some as though they had
been inflicted by true (dog-like) biting action, others, as scars inflicted during theprocess of capturing prey; such as fish armed with protective spines or teeth(?).

Fig. 23.

Platanista gangetica (Lebeck).

REFERENCES
KASUYA, T., 1972. Some informations on the growth of the Ganges dolphin with a comment on the
Indus dolphin. Sci. Rep. Whales Res. Inst., 24: 87-108.
NISHIWAKI, M., KASUYA, T., KuREHA, K. and OauRo, N., 1972. Further comments of Mesoplodon
ginkgodens. Sci. Rep. Whales Res. Inst., 24 : 43-56.
OLIVER, W.R. B., 1937. Tasmacetus shepherdi: A new genus and species of beaked whale from New
Zealand. Proc. :(,ool. Soc. Lond. 107, Ser. B, 371-381.
OMURA, H., FUJINO, K. and KIMURA, S., 1955. Beaked whale Barardius baidi ot Japan, with notes of:(,iphines cavirostris. Sci. Rep. Whales Res. Inst., 10: 89-132.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

BODY SCARRING ON ODONTOCETESEXPLANATION OF PLATESPLATE I

Orcinus orca Linn.
Fig. 1. Scars faintly seen on the dorsum.
Fig. 2. Scars more clearly visiible about the head and jaws.
PLATE II

Delphinus delphis Linn.
Series of teeth marks on the dark area of the dorsum.
PLATE III

Lagenorhpnchus obscurus (Gray)
Fig. 1. Scars clearly visible about the mandible and around the eyes.
Fig. 2. Scars seen about the region below the dorsal fin.
PLATE IV

Berardius amouxi Duvernory
Fig. 1. Head on view showing dorsal and lateral scarring.
Fig. 2. Lateral view showing scars, old and new : at the lower edge, note scar
possibly inflicted by ' Killer ' Whale.
PLATE V

Berardius arnouxi Duvernory
Fig. 1. Caudal region, note the several attempts of 'Killers' or perhaps sharks.
Fig. 2. Note the various types of scarring below the dorsal fin.
PLATE VI

Ziphius cavirostris Cuvier
Fig. 1. Dorsal view.
Fig. 2. Closeup of dorsum showing dorsal fin and scars, single parallel and elliptical scars.
PLATE VII

Ziphius cavirostris Cuvier
Fig. 1. Ventral aspect showing vent and genital apertures together with the associated scars.
Mesoplodon grayi Haast.
Fig. 2. Ventral aspect showings vent and genital openings with the types of scarring.
PLATE VIII

Globicephala melaena (Smith)Dorsal aspect showing the numerous series of scars inflicted by the teeth of the
opponent.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

155

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GROWTH AND REPRODUCTION OF STENELLAATTENUATA IN THE PACIFIC COAST OF JAPANTOSHIO KASUYA, NOBUYUKI MIYAZAKI
Ocean Research Institute, University of Tokyo, TokyoAND

WILLIAM H. DAWBIN
School of Biological Sciences, University of Sydnry, Sydney

ABSTRACT

Data collected from 7 schools of S. attenuata were analyzed. Body length
at birth is 89 cm. Sexual maturity is attained at 8.2 years in females and10.3 years in males. Physical maturity is attained soon after the attainmentof sexual maturity at a length of 194.9 cm (females) and 203.3 cm (males).
The pigmentation and size of the animals slightly differ from the corresponding species in the eastern North Pacific. Mating seasons are in February andMarch, July, and November. Gestation lasts for 11.2 months, and lactationfor 29 months on average. The mean length of reproductive cycle is about
50 months, but changes with the age of the animal. The annual mortality rate
is 0.074 in the mature female and about half of it in immature animals. Some
females live for more than 40 years, and have an average of 8.3 calves. The
mortality is higher in males than in females. Schooling behavior is discussed.
INTRODUCTION

Stenella attenuata (Gray, 1846) is distributed widely in tropical and subtropicalwaters of the ludo-Pacific Ocean. In the eastern tropical Pacific the probably
conspecific separate population (Perrin, 1973) S. grajfmani is often caught by tunaseine, and its biology is being studied (Perrin, 1969, Perrin and Roberts, 1972).
In the southern Pacific some biological study is reported by Dawbin (1966) basedon animals caught at Malaita (Solomon Islands). Though this species is alsocaught at Taiwan by hand harpoons for human consumption (Kasuya, unpublished),
it has not been studied biologically.
In Japanese coastal waters this species is common along the southern coastfrom Kyushu (Mizue and Yoshida, 1962) to Onahama (36°56'N, 139°55'E) (Kasuya,1971), and has been caught sporadically by fishermen with hand harpoons or thedriving method. On the east coast of Izu Peninsula S. attenuata is usually caught
in October and early November slightly before the peak of the season of S. coeruleoalba (Tobayama, 1969), and on the west coast of Izu Peninsula (Nishiwaki, 1965)
slightly after the spring season of S. coeruleoalba. However, on the coast of Kii
Peninsula a few animals have been captured with hand harpoons in all seasons ofSci. Rep. Whales Res. Inst.,

No. 26, 1974, 157-226

158

KASUYA, MIYAZAKI AND DAWBIN

the year, and recently fishermen have started to catch this species by the driving
method in both winter and summer seasons. This suggests that S. attenuata lives
in warmer waters than S. coeruleoalba, and in early autumn they move to the south
along the Pacific coast of Japan. As they are found in waters at more than 16.8°C(Miyazaki et al., 1974), they surely migrate up to 40°N but the information on
northbound migration is scarce (Kasuya, 1971, Miyazaki et al. 1974). The distribution of this species in the Japan Sea is also unknown.
The biology of S. attenuata was partially studied by Nishiwaki et al. (1965).
The present study is intended to clarify differences between the life history of thisspecies from that of a similar species, S. coeruleoalba, and to provide some information on relationships between ecology, environment, and certain species of delphinidae.
MATERIALS AND METHODSAll the materials used in this report were obtained, with a few ancillary materials,
from 7 schools caught by the driving method at Kawana or Futo on the east coast
oflzu Peninsula, or at Taiji on the coast of Kii Peninsula (Fig. 1, Table 1). One
48 cm fetus was collected in February from a female caught by hand harpoon at
Taiji, and 2 of the 4 sets of data on stomach contents of calves were obtained separately at Kawana.

~-~--~--~--~--~~:·-,~-~33"
Fig. 1. Map showing the positions of sampling, A indicates Arari, K Kawana, F
Futo, and T Taiji. Dotted lines indicate 200 m depth.

As shown in Fig. 2, school 1 was composed of adult males, females and newborn calves, but was lacking in calves of from 128 cm to 156 cm in body length.
The pregnant females had small fetuses. The length frequencies of schools 2 to
5 are more or less similar with calves and adult dolphins of various length, but the
fetuses were slightly bigger than those observed in school 1. School 6 was different
from schools 2 to 5, in the larger size of fetuses. In school 7, full term fetuses andnewborn calves were observed. It is difficult to know the exact composition of theSci. Rep. Whales Res. Inst.
No. 26, 1974

STENELLA ATTENUATA

159

larger individuals because of the limited material, but it may not be very different
from that of school 3.
Body length was measured in 1 cm intervals in a straight line from the tipof the upper jaw to the bottom of the notch of the tail flukes. In some cases 4
length measurements shown by 4n~L~4n+3 were grouped, where n is an integer
and L is body length in cm.
The mammary gland was observed in the field and classified into lactating
and nonlactating. In some cases its thickness was measured in a longitudinal cut
made by the fishermen, because they did not welcome transverse section of the
mammary gland. These data were used for reference.
7

..A

15 6
10
5
-~

20 4
Ill 15
c 10
a. 5

:c
0

"O

.....0 5

3. 25 2

~ 20

15
10

.

/\

,,;>.,\

5
15 1
10
5

l-.

0

.. A

. . -~!::. "
20

0

40

60

80

100

120

140

160

180

200

220

Body length in cm

Fig. 2. Length frequencies of S. attenuata in the 7 schools studied. Numbers at
the left indicate the school, open circles females, closed circles males, dotted lines
fetuses, and solid lines postnatal animals. The full term fetuses and newborn
calves in school 7 are not separated.

The ovaries were collected from most of the adult and immature females, andfixed with 10 % formalin solution. The number of corpora albicantia and lutea
was counted by Kasuya in the laboratory by slicing the ovary into about 1 to
2 mm thickness. The three diameters of all the corpora lutea and albicantia andthose of the largest follicle were measured. The volume index of the corpora orfollicle obtained by multiplying the three diameters was used in the analysis ofovarian activity. But in this report the mean diameter obtained as the cube rootof the volume index has usually been used.
Both testes were collected from the males in schools 1 and 2, but only the left
one in other schools. They were preserved in the same manner used for ovaries.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

160

KASUYA, MIYAZAKI AND DAWBIN

The weight was measured in the laboratory. As there is no significant difference
expected in the weights of right and left testes, usually the left side was used forstudy and the right was used only when the left testis was not available.
Several maxillary teeth were collected from the center of the tooth row witha pair of gardening scissors. The tooth section for age determination was preparedafter the method of Kasuya (1972) slightly modified to use a grinder. The growthlayers in dentine were observed by Kasuya under transmitted light with a binocular
microscope (x50).
TABLE 1.
School
no.
l

2
3
4
5
6
7

Dates of

MATERIALS USED IN THIS REPORT.
No. of dolphins*
~

catch

kill

caughtstudied23, X, '70.
10, XI, '70.
4, XI, '72.
13, XI, '72.
16, XI, '72.
12, II, '73.
2, VII, '73.

25, x.
15, XI.
4, XI.
13, XI.
18, XI.
12, II.
2, VII.

264
1381
189
192
67
146
Ca. 60

131
273
48
117
23
122
36

Locality

Researcher

KawanaKasuya and Miyazaki

"

"
Fu to
Taiji

Miyazaki"Dawbin* : Fetuses not included.

Some of the selected testes were studied histologically after staining with haematoxylin and eosin. In these cases samples were collected from the center of thecross section made at the midlength of a testis. In order to check the presence of
spermatozoa in a wider range, smears were taken from most of the testes on thesame cross section, and observed after staining with methylene blue. These testes
observations were made by Miyazaki and Kasuya.
AGE DETERMINATION AND GROWTH

Age determination
The growth layers in dentine were used to determine the age characteristics
as the cementum of S. attenuata is too thin to count the growth layers. The natureof the dentinal growth layers of this species does not differ much from that of S.
coeruleoalba (Kasuya, 1972), but counting is slightly more difficult because of theirregularity of the layers. The poorly calcified secondary dentine is observed inteeth with about 12 or more layers. This may indicate that the growth of the dentine becomes slower in these ages, when physical maturity of the animal is attained.
To find the annual accumulation rate of dentinal growth layer, the condition of
the last layer was checked on teeth which had 10 or less opaque bands and in which
the thickness of the layer was not too thin to estimate the relative thickness. Though
the relative thickness of the layer was estimated in comparison with the former layer
taking into consideration the gradual decreasing size of the layer, this observationis less reliable than the identification of opaque or translucent layers. As shownin Fig. 3, most of the animals killed in July, October and November were forming
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

STEJVELLA ATTENUATA

161

opaque layers, but almost all the animals killed in February were accumulatingtranslucent layers. In the present study it has been impossible to decide the datewhen the formation of the two kinds of layers alternate, but it seems probable thatthe alternations occur in December or January and in April or May, and thateach opaque and translucent layer represent about 6 months respectively.
In this study the number of opaque layers in dentine, excluding the fetal layer,
was counted together with observation of relative thickness and condition of thefirst and last layers. The layers were usually counted along the line set from the80......

~
60
u
c

a.

:J

g.... 40IJ...

X XI XIIII Ill IV

V VI VII VIII IX

X

Month
Fig. 3. Seasonal change of the formation of opaque and translucent dentine layers.
Black with white spots indicates thin opaque layer, the black thick opaque layer,
the white with small spots thin translucent layer, and the white with large spots
thick translucent layer.

TABLE 2.

CRITERION FOR CALCULATING THE AGE FROM THE
NUMBER OF OPAQUE LAYERS (n).

First and last layers

Possible range of age

Approximate age (x)tt-tt

n+0.50~x>nx~n+0.25

tt- t

n+0.25~x>n-0.25

x~nt- t }

n~x>n-0.50

x~n-0.25

n-0.25~x>n-O. 75

x~n-0.50

n-0.50~x>n-l

x~n-0.75

oo-tt
oo- t }
o-tt
00-00}'

o- t
oo- 0
o- 0

n-0.75~x>n-l.25

x~n-1

n-l~x>n-1.50

x~n-1.25

o : thin opaque, oo : thick opaque, t : thin translucent, tt : thick translucent

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

162

KASUYA, MIYAZAKI AND DAWBIN

middle of the neonatal line to the central portion of the pulp cavity, because thestructure near the distal tip is sometimes discontinuous especially in the young layers.
When the number of opaque bands (n) is counted the possible range of real age(x) is generally shown by the following formula.
n-1.5<x<n+0.5
In case of animals at 3.5 years or older, the approximate age was represented by
the value at the center of both extremities, orx:;=n-0.5
However, in the case of the younger animals, it was calculated from the criterion
shown in Table 2.
As indicated in the latter section the counting of the dentinal growth layers
is not reliable after the accumulation of secondary dentine, but the age of animals
obtained from dentinal growth layers by the above method has been used in thisreport without special comment.

Length frequencies
The length frequencies of fetuses and juveniles varies between schools. This
reflects the special schooling behavior related to the maturity and reproductive
cycle. These problems are dealt with separately. There is no significant difference observed between schools in the shape of the peaks for animals more than
184 cm in females or 196 cm in males. When all schools are combined, the highest
frequency is found in the length group 192 cm to 195 cm in females, and 204 cm
to 207 cm in males. The difference of the modal lengths is about 12 cm. Most
females are shorter than 212 cm and males less than 220 cm, but exceptionallylarge records of a female and a male were 220 cm and 234 cm respectively.
The above modal lengths seem to be slightly bigger than that of S. grajfmani
reported by Perrin (1969).
Petal growth and length of gestation
The mean body length at birth is estimated roughly from the 5 full term fetuses
or newborn calves in school 7. In this school 85 cm female, 85 cm male, and 88 cm
male were considered to be definitely prenatal because they were found with large
umbilical cord attached, or taken out of the uterus by Daw bin. The 89.0 cm male
was considered to be a newborn calf because it had no trace of umbilical cord,
but the umbilicus was the shape of an oval hollow with thin epidermis and thesize was larger than that of a fully healed umbilicus. Its stomach contained milkof about 13 g in weight. One 88 cm female animal was found in the pile of viscerawith the thin fragment of the external layer of the umbilical cord. However, thesize of the fragment was much smaller than that of the 3 specimens first mentioned.
The dorsal fin was not bent completely to one side as in the case of the fetus, butstood obliquely. On the lateral side of the body of the animal there were observed
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

STENELLA ATTENUATA

163

several transverse shallow grooves which are often found on the fetus. It had nomilk in the stomach. According to the observation of Nakajima et al. (1963) ona Tursiops truncatus born in an aquarium, it takes several hours for the dorsal fin
to stand vertically. Our observation on a newborn S. coeruleoalba, 100 cm in bodylength, shows that it had plenty of milk in the stomach in spite of features quite
similar to the above 88 cm S. attenuata in the umbilicus, dorsal fin, and grooves on
the flank. This suggests that the 88 cm animal was postnatal. However, we havesome query on the last specimen of S. attenuata as to whether it was delivered by theartificial action given to the mother in the period from the start of driving to thetime of kill. However, the present best estimate of the mean body length of S.
attenuata at birth comes between 88 cm and 89 cm. In this paper 89 cm has beenused as the tentative mean length at birth. Even if it is 88 cm in reality, the lengthof gestation is changed by only 3 days, which is negligible in relation to our tentative
estimate of the mean length of gestation obtained below.

140
E 120

u

c
~ 100

Oi
c
(!)

--;:_ 80
-0
0

CQ

60
40
20

Month
Fig. 4. Growth of fetus and juvenile calves. Length frequencies are grouped intomonths. The dotted area indicates fetuses, the white postnatal, and closed circles
the mean body lengths of fetuses in each school. A school caught in May (Nishiwaki
et al, 1965) is shown by solid line.

The length of gestation and fetal growth were calculated from the seasonalchange of fetal length. In Fig. 4, the mean fetal length in each school was plotted
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

164

KASUYA, MIYAZAKI AND DAWBIN

against the date of kill. In school 2 the fetal length is bimodal, but it was notseparated because the deviation from the main mode is not large. In other schools
the fetal length is unimodal. In school 7 all the full term fetuses and newborn
calves were combined in calculating the mean length. In addition to the 7 schools,
one record of a fetus caught at Taiji in Feburary is also plotted in Fig. 4. All theabove 8 points fall on a straight line, but the fetuses reported by Nishiwaki et al.
(1965) come on quite a different position. The latter are considered to represent
other mating seasons, and are dealt with separately. Laws (1959) showed inodontoceti that, except during the very early stage of growth, the relation between
fetal length and the elapsed time after conception is shown by a single straightline. If a straight line is calculated by least squares for the above 8 points, thegrowth of the fetus is shown by the following formula,y = 0.30094x- 76. 74
where y is the length of the fetus in cm and x is the number of days counted fromthe last lst of January. This formula shows that the daily increment of length at
the straight part of the growth is 3.0 mm. The extended growth line cut theaxis of time at day 255.01 or 12th of September, and attains the mean length atbirth, 89 cm, on day 550.73 or 5th of July. Accordingly the length from the datewhen the extended straight line crosses the axis of time to the date of birth is295.72 days.
If 0.135 X gestation period is tentatively used here for Lto of Laws (1959),
which is the time from the start of gestation to the date when the extended straightline of the fetal growth cuts the axis of time, the length of gestation (L) is shownby the following formula
L-Lto = 295.72 days
Lto=0.135L
Then Lis 341.87 days or 11.24 months and Lto is 46.15 days or 1.52 months.
The date of conception of the growth line in Fig. 4 comes on 28th of July. The
fetal growth rate of this species at the straight part of growth is close to that of
Tursiops and Phocoena reported by Fraser and Huggett (1973).

Postnatal growth
The relation between body length and age of 195 males and 239 females isshown in the scatter diagram of Figs. 5 and 6.
The growth during the first three years is rapid. The mean growth curveof this part was drawn by eye based on the mean lengths in each 1/4 year intervaland considering the distribution of each point in Figs. 5 and 6. As no sex differencein these age classes is observed, both sexes were combined.
The growth of males between the age of 3 years and 12 years, and of females
between the age of 3 years and 7 years seems to be almost straight. The growthline of this age range was calculated by least squares based on the mean body
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

STENELLA ATTENUATA

165

lengths, weighted by the sample size. As the sample is small and no significant
sex difference is observed in the age groups between 3 and 6 years, the data for

200

.

180

•

§

.

.£ 160·/:t:l-~~-1~: _i_:_~::J..::--f-• 'fr ·r.
~f. ·r "
I

~".:

·~
;

~

~

·!'
:

+

•--',------:

.

.

/" .

l.

140

~ 120tm

100.
800~~~~~-5~~~~~_.__,__._~____...---"~"---'--L--...L--i--'--1--'-----'--'

1015
Age in years

20

Fig. 5. Mean growth curve of female S. attenuata. Age was estimated from thedentine growth layers. Each spot indicates one animal and rod the mean bodylength.

!

*________________._
t_ _ :

200

...

_,,_

i.

E 150
u

.£

_;,

..... 160

.J::
01

c

~

140

>-

"O

-;-

.}
..

m 120 f
0

100!
80

0

10

20

Mean growth curve of male S. attenuata.

For symbols see Fig. 5.

5Fig. 6.

15
Age in years

females were included. Then, the the following relation is obtained between theyear after birth (x) and the body length (y) in cm.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

166

KASUYA, MIYAZAKI AND DAWBIN

y = 4.20x+ 153.8,

3.5~x~ 11.5

This indicates that the mean annual increment of body length is 4.20 cm
The increase of the mean body length finishes in males at the age of 11.5 years.
This is the age when most of the animals attain physical maturity. The asymptotic
length of males at 203.3 cm is obtained as the mean of 49 males with ages of 12.5
years or more.
The mean growth of females becomes slower after 6.5 years of age and thedifferences of length between the sexes increases. The growth of females seems tostop at the 1 lth year. The mean asymptotic length of females obtained from 137
females which are at the age of 11.5 years or more, is 194.9 cm. This is 8.4 cm
smaller than that of males. This difference results from the earlier slowing downof growth and the earlier attainment of physical maturity in females. Females
seem to attain physical maturity soon after the attainment of sexual maturity asin the case of males. This is confirmed by the fact that the mean body length atthe ovulation of 1, 2, 3, and 4 is 189.5, 191.4, 192.5, and 192.4 cm respectively,
and attains at 5 ovulations 195.1 cm which is approximate to the asymptotic length
194.9 cm. Then the mean lengths do not show the increase but fluctuate in therange between 192 cm and 198 cm. The mean body length of the sample in each
TABLE 3.

GROWTH OF STENELLA ATTENUATA.
Body Length (cm)Age(year)

mean of sample (sample size)

6
0
0.25
0.50
0.75
1.00
1.25
1.50
l. 75
2.00
2.25
2.50
2.75
3.00
3.5
4.5
5.5
6.5
7.5
8.5
9.5
10.5
11.5
12.5;;;;

Q

89.0 ( l)113.4 (17)124. 6 (18)
133 .1 ( 8)140.5 ( 2)
150.8 ( 4)149.0 ( 2)
160.2 (10)158.3 ( 4)165.3 ( 4)166.0 ( l)175.7 ( 3)168.8 (10)172.6 ( 8)177 .3 (13)182.6 (11)179.4 ( 7)185. 7 (16)186.2 ( 9)186.8 (18)187 .6 ( 20)193. 3 (16)191.5 ( 22)198.1 (19)194.0 ( 18)204.4 ( 9)194.9 ( 22)203.3 (49)194.9 (115)

on growth curve

6

Q

89.0
111.0
124.6
134.5
142.7
148.3
152.3
155.8
158.9
161.2
163.1
164.7
166.0
168.5
172. 7
176.9
181.1
181.1
185.0
185.3
189.5
188.3
193.7
191.5
197.9
194.0
202.1
194.9
203.3
194.9

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

167

STENELLA ATTENUATA

age group and the corresponding body length on the growth curve obtained in theabove are shown in Table 3.
Kasuya (1972) tried to adopt exponential formulae for the mean growth
curve of S. coeruleoalba, but the fit was never good. In the present study we could
not find a suitable formula to express the mean growth of the present species. For
comparison, the mean growth curve of S. coeruleoalba is shown in Fig. 7. This was
based on the 881 animals obtained by the end of 1972 including the data used by
Kasuya (1972), in which age determination was made by the same author. The
y=234.4

220 __2!~~---------------~C>~~----- -~t.P~~'l.i..

200 _JnQ__ _______ 0___...E-----0--·"--"--------'~10y"223.5:'y-203.3.

%- ------~------~--~-o-o-0-~-o--~-':

180 _J~'i,Q ___ -r--:~~~\<;,~~--:---,. ·_1· ..

y•194.9

r:: f/~.
Oi

c

~

120

"8>- 100
i::o

40

'

'

20

:
''

'
'

'
N: CO:~~
oo: oj:~:' ''O"'---'----'---'--'---'----'---'--'--...L...'~!,__-'-'-'---'---'--'---'----'---'--'---'--'
-1 0
2
4
6
8
10
12
14
16
18

Time in years
Fig. 7. Comparison of the mean growth curves of Stenella coeruleoalba (upper pair)and of S. attenuata (lower pair). The largest circles indicate the mean length represented by 25 or more animals, the intermediate from 11 to 24 animals, andthe smallest 10 or less animals. In both species closed circles and the upper line
indicate males and open circles and the lower line females. The age of female S.
coeruleoalba at sexual maturity was cited from Kasuya (1972). The slow growthstage at early pregnancy is not shown.

straight part of the male growth curve was calculated by least squares, but that of
the female was drawn by eye. The feature of this part is its strong resemblance
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

168

KASUYA, MIYAZAKI AND DAWBIN

to that of S. attenuata, except for the slight between sexes difference of length. If
enough data is accumulated, a similar pattern of growth seems likely to be observedin S. attenuata. The age at physical maturity of S. attenuata seems to be about 1
year earlier than that of S. coeruleoalba. The difference of asymptotic lengths between two species is mainly affected by the difference of growth in young stage.

Weaning
Direct information on the start of the weaning is scanty (Table 4). Ourdata suggest that some animals start feeding on solid food at the length of 115 cm
and the age of 1/4 year, but most of the animals start at about 130 cm, or about
half a year after birth.

~10

2 3 4, 3

~

~ .8

3 4 2

0

I- .2
00-

2

3

4

5

6

7

8

9

Age in years
Fig. 8. Relation between age and the thickness of postnatal dentine of S. attenuata.
Open circles indicate the mean of females, the closed males, and vertical andhorizontal rods the range and mean for both sexes. Numbers at the top indicate
sample size. The line was drawn by eye.
TABLE 4.
Body length
115cm
122cm
128cm
129cm
168cm

STOMACH CONTENTS OF JUVENILE STENELLA ATTENUATA.
Age
1/4
1/2

Sex

6
6
6
6
~

Milk

+

Food remains

Nematoda

+

+

+
+

+

The thickness of postnatal dentine measured in cross section at the level ofthe proximal end of prenatal dentine was compared with the growth of the animal.
As shown in Fig. 8, the increase of the thickness of dentine after 1 year of age showsa similar pattern to that of body length, but it shows a rapid increase at the age
between 0.5 and 1.0 year. When it is compared with the body length (Fig. 9), theSci. Rep. Whales Res. Inst.,
No. 26, 1974

STENELLA ATTENUATA

169

growth of dentine changes from a low rate to a higher rate at a body length ofabout 133 cm, which corresponds to the age of 0.7 year.
It is generally known that the baleen plates of mysticeti grow rapidly at theperiod of weaning. A similar feature is also expected in the growth of teeth,
because teeth would start to have a mechanical function in catching food after
the start of weaning. Probably the weaning of S. attenuata starts, in the average,
at an age between 0.5 and 0.75 year or at the length of 130 cm. However, theweaning period seems to last long in the case of toothed whales, and the start offeeding on solid food does not necessarily mean the cessation of suckling. The
duration of suckling is dealt with separately.
3 12

5

1 2

E t.4
E
.i;;; 1.2

12

g 5

(])

c

:.;;; 1.0

&;

"'C
-

0

3

.8

m.6

6

1
•

2

4

t

(])

c

i5 .4

:.c

I-

.2
0

2

100

1

120

140

160

180

Body length in cm
Fig. 9. Relation between the thickness of postnatal dentine and body length of
S. attenuata. The line was drawn by eye. For other symbols see Fig. 8.

The calf of Tursiops truncatus starts to take solid food at an age of from 6.3
to 9 months, or 0.5 to 0.8 year (Tavolga and Essapian, 1957, Nakajima et al, 1963).
This coincides well with the information obtained on S. attenuata.

Age at the attainment of sexual maturity of the female
As the left ovary of this species matures earlier than the right (Ohsumi, 1964),
it is reasonable to expect earlier development of the left ovary even in immature
animals.
Fig. 10 shows the difference of weight between the two ovaries of immature
females of S. attenuata. In young animals the weight of the left ovary is nearly
equal or slightly smaller than that of the right, but the growth of the left ovary
starts to exceed that of the right at a body length of about 170 cm. The age corresponding to this length is about 4 years. This may indicate the approach ofpuberty even if development of the follicle has not started. This age is about one
year later than the age of the male when the formation of spermatozoa in theSci. Rep. Whales Res. Inst.,
No. 26, 1974

KASUYA, MIYAZAKI AND DAWBIN

170

testis starts.
Fig. 11 shows the relation between age and the diameter of the largest follicleof mature and immature females of S. attenuata. The observed largest diameter
was between 10 and 11 mm. This size is considered to be close to the size at
ovulation. The development of the follicle in immature females is observed onlyin animals at the ages of 6.5 years or more. This means that puberty of females
starts at this age which is very close to the age at the attainment of sexual maturity,and that the growth of follicles is rapid to attain the size at ovulation.
The youngest mature female is found in the age class of 7.5 years and theoldest immature in that of 9.5 years. The percentage of newly mature females at

1.2

en .s
,£;
......... .6
0:
I

~ .3

-.3 ,_1_,_20_ __,____14.LO,---L---:-'.16~0:---'---;::18:.:;-0-~~

Body length in cm
Fig. 10. Relation between the difference of the weights of both ovaries and bodylength in immature S. attenuata.

TABLE 5.

MATURITY OF S. ATTENUATA BY AGE GROUPS.
Male*

FemaleAge
immat.
<1<2;;::;3
3.5
4.5
5.5
6.5
7.5
8.5
9.5
10.5
11.5
12.5
13.5
14.5

12
2
2

pub.

3
1
2
3
9
12
13
9
7
2
3

mat.

2
3
11

6
8
8
10

mat. (%)

immat.

mat.

mat. (%)

0
0
0
0
0
0
10.0
0
13.3
25.0
61.2
75.0
72.8
88.9
100

15
4
10
8
3
7
7
6
7
2
0
0
0
0
0

0
0
0
0
0
0
0
2
12
18
18
21
27
15

0
0
0
0
0
0
0
25.0
63.2
90.0
100
100
100
100
100

11

*: Based on testis weight when other information was not available

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

STENELLA ATTENUATA

171

the age of between 6.5 and 7.5 years, 7.5 and 8.5 years, 8.5 and 9.5 years, and
9.5 and 10.5 years are calculated from Table 5 as 25.0 %, 38.2 %, 26.8 %and 10.0 %respectively. This indicates that most of the animals attain maturity at an age
between 7.5 and 8.5 years. But as there are observed some females which are con10

E
Ee
,!;;;
.... 6

OJ

Q;

E4
Cj

i5 2
0 W-6.ll.5--6.l-5

105

125

145

165

165

20.5

22.5

Age in years
Fig. 11. Relation between the diameter of the largest follicle and age.
squares indicate immature females and black the mature.

Male

120

->.ae

White

100

u

80

c
~ 60
0-

....(!J

LL 40

20

I

"'g
8

10

_J
12

14

7

9

11

Age in years
Fig. 12. Age at the attainment of sexual maturity in S. attenuata. Open circles
indicate the cumulative frequency of immature animals, and closed circles thatof mature animals. For explanation see text.

sidered to be in the second cycle of reproduction in the age classes of 7.5 and 8.5
years, a few females seem to attain sexual maturity at an age between 5.5 and6.5 years (Table 19). The mean age offemales at the attainment of sexual maturity
was obtained after the method of Kasuya (1972) as the age where the cumulative
frequency of immature animals in older age classes is equal to that of mature
animals in younger age classes (Fig. 12). It gives the mean age of females at theSci. Rep. Whales Res. Inst.,
No. 26, 1974

KASVYA, MIYAZAKI AND DAWBIN

172

attainment of sexual maturity as 8.2 years.
on the mean growth curve.

The body length at this age is 187 cm

Age at the attainment of sexual maturity of males
The bilateral difference of testis weight was checked on 44 animals collectedfrom schools 1 and 2.
If the mean of the left weight minus right weight is equal to zero it is concluded that there is no bilateral asymmetry. As shown in Table 6, the mean difference in mature animals is small enough to consider that there is no significant
asymmetry of the testis weight. In testes with 68 g or less weight, the observed
deviation of the mean from zero is large enough to be expected at the probability
between 2 to5 %. But at present we consider that this does not prove asymmetryof testis weight, so the weight of the left testis was usually used in the following
discussion.

20.......·:·:
104

108

1.12
us
Ratio

1.20

....
:·:·
....
1.24

Fig. 13. Frequency distribution of the ratio of the weight of the heavier testis tothe lighter. Dotted area indicates the pairs where the right testis is heavier or
equal to the left.
TABLE 6.

T-TEST OF THE SYMMETRY OF THE TESTES WEIGHT.

Weight(left, g)

Range(L.-R.)

Mean
difference

SamplesizeStandard
error

Probability

68>-10.9- 1.4-30.0-30.0-30.0-30.0-1.2720+1.9053+0.100025
19
44

0.58083.6574
1.60750.05>p>0.02
0. 70>p>0.50
p>0.9068~

Total

The ratio of the heavier testis to the lighter comes between 1.00 and 1.28
(Fig. 13). However, about 93% of all the pairs observed show a ratio of less than
1.20. This means that if the left testis is weighed, the weight of the right side is
expected with a probability of more than 90 % to be between 1.20 and 1/1.20(0.83) times that of the left.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

STENELLA ATTENUATA

173

The maturity of the testis was checked by two methods. One is histologicalexamination of testis tissue taken from the center of the cross section at the midlengthof the testis. When spermatozoa were observed in this part, the testis was considered to be in full maturity. The smallest testis in this condition was 66 g, andthe largest immature testis was 71 g. Accordingly the mean weight of testis at
the attainment of full sexual maturity is considered to be about 68 g, and any
testis of this weight or heavier was classified as mature.
600
400
300

•

,f •

,f

8

o I oo J
oJ-ooooJ

200

8

• ~
•

I

..

.

g

• g·

I

:J> o 8

J,.... 100
.9 80
Ill

·~

~

60

-

40
30

0

20

2

\
\

8
6

\

\o

.
..

.... . \, .

~

\

I

0

L\1~6
~

•• ...
1:" \

~ ...

. . • ~. . t8 ~ ~:EOl·a; 10
3

\

~

0

\

••

:

\

o\

4
3 \ •\

"··:

2 ...
1

0

2

4

6

8

10 12

14

16

18 20 22

Age in years
Fig. 14. Scatter diagram of the weight of testis and age. The weight of testis
is plotted on logarithmic scale. Large closed circles indicate spermatozoa absent
in the smear, open circles spermatozoa present in the smear, small closed circles
no observation of the smear, rod at the upper left immaturity of the tissue at thecenter of testis, rod at the upper right the maturity, and solid line mean weightof testis at the attainment of sexual maturity.

Even if a testis is identified as immature by the above method, when the smear
taken from the cross section at the midlength of the testis is observed some spermatozoa are usually found. This probably means that even when the core of thetestis is not mature, some part, most likely the tissue at the periphery has alreadystarted the formation of spermatozoa. This phenomenon is the reverse of theobservation on sperm whales reported by Best (1969), and will need further confirmation. An animal which has the testis at this stage is considered to be in
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

174

KASUYA, MIYAZAKI AND DAWBIN

puberty. This stage of testis was commonly found among those with weight between 6.0 g and 68 g, so any animal with a testis of between 6.0 g and 67.9 g wasclassified as puberal.
Among animals which have a testis weight corresponding to the criterion ofpuberty, there are some which have no spermatozoa in the smear. The ratio ofthese to all puberal animals varies between schools. This can be related to thereproductive season or the school structure and will be dealt with separately.

600
JJ

400
300

0

0

200

1:
-~ 10
3 8
6

4

3

120

140

160

180

200

Body length in cm
Fig. 15. Scatter diagram of the relation between weight of testis and body length.
For symbols see Fig. 14.

As shown in Table 5 and Figs. 14 and 15, all males younger than 2.0 years
or 160 cm in body length are immature. Puberal animals first appear in the ageclass 2.0 years and are observed until the age of 13.5 years. Most animals in age
classes between 2 and 8 years or length between 160 cm and 187 cm belong to the
puberal stage.
Fully mature animals start to appear at the age of 6.5 years and all animals
attain sexual maturity by the age of 14 years. After this the weight of testis does
not increase with age.
The mean age at the attainment of sexual maturity obtained by the same
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

STENELLA ATTENUATA

175

method used for females is 10.3 years. This is about one year higher than that ofS. coeruleoalba, in spite of the larger weight of testis and smaller diameter of seminiferous tubules at sexual maturity of S. attenuata. The mean body length corresponding to this age, 197 cm, is obtained from the mean growth curve.
Fig. 16 shows the relation between mean diameter of seminiferous tubules
and weight of testis. The histological samples were taken from the center of asection at midlength of the testis. The mean of the measurements of 15 tubules
measured on a photograph was used as the mean diameter of tubules of the animal.
The relationship between weight of testis and the mean diameter of tubules isshown by two lines as calculated below.

D=24.94 W 0 · 22528, W <68
D=ll.11 wo.44692, W~68
In the formulae, D is the mean diameter of tubules in µ, and W the weight oftestis m g. The mean diameter of tubules at the attainment of sexual maturity
is between 60 and 70 µ, which is smaller than that of S. coeruleoalba (Hirose andNishiwak, 1971).
250
200

..

150
Cl>

:E 1003

0:__ .... ....:.··.....,, · .... --

70

,'

L..

,

2Cl>

.. tf>:".

E 50
0
i5 40

.

.30

..

.

...............
500

20L---L.:..-1..--1..:...1..L.Ll...Ll..-~l..--'-'-'-..L.U....LJ..L.~-'--"--'-

1.5 2 3.

5

10

20

50

100 200

Weight of testis (g)Fig. 16. Relation between the mean diameter of seminiferous tubules and the weightof testis, plotted on logarithmic scales. Lines are drawn by the least squares.

The weight is proportional to D 4 · 4 in immature animals but to D 2 · 2 in mature
animals. This suggests that the fluctuation of the weight of testis of mature animals
is affected by the change in diameter of seminiferous tubules.

The body length where half of the animals attain sexual maturiryThis length is defined as that where the number of immature animals above
this length is equal to that of mature animals below this length, and obtained by
the same method used in the former section in calculating the mean age at theSci. Rep. Whales Res. Inst.,
No. 26, 1974

176

KASUYA, MIYAZAKI AND DAWBIN

attainment of sexual maturity. It gives a length 181.9 cm for females and 194.3 cm
for males (Fig. 17). These values are slightly shorter than the body lengths corresponding to the mean age at the attainment of sexual maturity. The differenceis 5.1 cm in females and 2.7 cm in males. These discrepancies are reasonable,
because the growth of the animal stops soon after the attainment of sexual maturity
and the attainment of sexual maturity may be more dependent on age than on
body length. However, the absolute values of the differences obtained here are
not highly reliable. The body length where half of the animals are sexually mature
is strongly affected by the age composition of the sample or of the population.
If the ratio of sexually mature old animals decreases by the effect of exploitation,
the value may become higher. This value is useful only when the maturity must
be classified based on the body length frequency.
Female

160
<!J

120

Ol

0 80
......
cCl.I 40
u
,_
<!J
a. 0

172

180

188

196

204

212

<!J

>
:;;

Male

.Q 160
:J

E 120
:J

u

80
40
0

180

188

196

204

212

220

Body length in cm
Fig. 17. Body length of S. attenuata where half of the animals attain sexual maturity.
For explanation see text.

Body weight
Body weight of S. atteuata is known for 20 females and 14 males. These data
are plotted on a logarithmic scale in Fig. 18. As the data are scarce a difference
between the sexes was not demonstrated. The relation between body length (L,cm) and the weight (W, kg) seems to be expressed by two straight lines. If theformula W =aLb is calculated by least squares, the following constants are obtained.
For the samples between 86 cm and 130 cm
a 1 =0.0001901
bi=2.3638
For the samples between 110 cm and 207 cm
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

STENELLA ATTENUATA

177

a 2 =0.00001876
b2=2.8504
The two regression lines cross at the point L= 116.6 cm. This means that the
body weight of the newborn calf is heavier than the weight obtained by extrapolating
the length-weight relationship of the older animals, and that after birth the calf
grows more in length than in circumference and therefore becomes more slender.
After the attainment of a length from 110 cm to 130 cm or an age of about 6 months,
the circumference increases more closely in parallel with that of the body lengththan at the earlier stage. However, as b 2 is still less than 3, S. attenuata continues
to become slender with increase of body length.

200
170
150

-----'-·~--'---'~~-~~~~-=':c-::'='"

6

7

8

10

15

20

25

30

40

50

60 70 80

Body weight in kg
Fig. 18. Relation between body length and body weight (top), and weight without
viscera (bottom). In the former each mark indicates one animal, and in thelatter each mark the mean for each length group. Open circles indicate female
and closed male. Weight and body length are plotted on logarithmic scale.

The weight of the animal without the viscera was measured by the fishermen.
The mean weight in each length group calculated from 179 females and 148 males
are shown in Fig. 18. The relation between body length and weight (w) without
viscera in kg was obtained combining both sexes as follows:
For the data between 84 cm and 131 cm in body length
w=0.0001237L2· 4217
For the data between 112 cm and 220 cm in body length
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

KASUYA, MIYAZAKI AND DAWBIN

178

w=0.000009887L2· 9595
These two lines cross at a body length of 109.8 cm
If the ratios of the visceral weight to the total weight is calculated from the data
used in the top of Fig. 18, they are 17.5% (4 animals from 85 to 89 cm), 11.5%(10, 114-130 cm), 11.6% (9, 149-189 cm), and 9.9% (11, 190-207 cm). They seemto decrease with the growth of the animal, and the decrease is especially rapid at abody length between 89 cm and 114 cm. This feature is also presumed from thetwo sets of formulae in the above.
PIGMENTATION
The pigmentation of S. attenuata from the Pacific coast of Japan was studied on
100 animals in schools 1 and 2. The pigmentation was classified into 4 grades as
explained below, and compared with the body length or with the age determination based on the dentinal growth layers. However, the latter was used only
for reference, because age information is scanty. The body lengths were grouped
into nearest 5 cm units.
Males

.

Females. .

A. White tip of up. jaw

2••11111•1·11.tl•1·-.-j-!--'-•-•-r•iil· 11-1~-•Jl'lt•
I
I 11110 ·-:-1 •

I I

.

c....

.

B. White tip of lo. jaw

Cl.I

·•·"r
... .
. ........

•• 111•_!.!J~2
a.
·.-p.-:-f-1-tll 1 •.
I l-fttl
If-•~·• I 11 •c 0 ·-1-I• .111
0.Q

C. Pale spots in the dorsal

<ii

~2
E
.Qlo •-1-1
a...

•

•tlll

• • 11 .~.-.

•I~-~·· . 1l-•-·---f/I I I

•

2

I I

•I

~-·"

I

I spots in the ventralII• • & .+I t1-t+••y-1• t ~I ••of •fof-f-l I..D. Dark•·•••·

0 ·-·___..-/
150

of'.f

170

•.)1 I t-1-o"'. . v.
I I ..........

.

190 210150 170
Body length in cm

190

210

Fig. 19. Relation between body length and pigmentation of S. attenuata. Smaller
circles represent one animal and the larger 5 animals. Body lengths are grouped
into 5 cm intervals. Lines indicate the mathematical mean of the grades. For
further explanation see text.

Pigmentation of newborn calf
The pigmentation of a newborn animal is pale and the pattern is quite different
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

STENELLA ATTENUATA

179

from that of an adult animal. The dorsal surface is bluish gray with a pale band
extending postero-dorsally at the base of tail peduncle. Both jaws and the dorsal
surface of the flipper is bluish gray. A dark band connects the eye and the baseof the upper jaw, and a paler band connects the insertion of flipper and lower jaw.
A very faint wide dark band extends from eye to the anal region. This band iscovered, in the adult, by dark spots and becomes inconspicuous. Other parts oflateral and ventral regions are white. The border of the dorsal dark area and ventral
white area is shaped like an arch at the part from the chest to the forehead. Thispattern of pigmentation strongly resembles that of Delphinus.

White area at the tip of upper jaw
The white tip was classified into 4 patterns. Satage 0 represents no purewhite area. In many animals classified into this stage, there is observed a small
area of paler pigmentation at the tip of the jaw. Stage 1 is represented by the
animal which has the white area but it does not extend posteriorly beyond theanterodorsal corner of the upper jaw, stage 2 by the animal of which the white area
extends between the antero-dorsal corner and the midlength of the rostrum, andstage 3 by the animal of which the white area on the upper jaw extends beyond
the midlength of the rostrum.
FemalesMales

A. White tip of up. jaw

.

2

•••••

I

~1-1-.--.-:i

0

• I

•

I •

I

.

•

···~

-~-·
I I I
• · •··•... .
·~. ·-· .'.~.~·-·-·-·-·~·. . . ..
•.•~·---·-•..,:~:·~.....
.
B. White tip of lo. jaw

..

I

•
• ••

I I I

•

•

C. Pale spots in the dorsal

.

' I

•-•

................

2

0 •?

I • ' •

D. Dark spots in the ventral. I ·i·..
.••• I : -.
/·--·""" ~·-.-.

... . ····- .

•.

..

....

0 2 L. 6 8 10 12 14- 2 L. 6 8 10 12 14Age in years
Fig. 20. Relation between the pigmentation of S. attenuata and the age of the animal.
For symbols see Fig. 20.

The animal of stage 0, or the animal which. has no white tip at the upper
jaw is found only among animals smaller than 185 cm (male) or 195 cm (female)in body length. The white tip starts to develop at a body length of 155 cm andSci. Rep. Whales Res. Inst.,
No. 26, 1974

KASUYA, MIYAZAKI AND DAWBIN

180

the ratio of animals with a white tip increases with age. The body length where
half of the animals have a white tip is about 170 cm in both sexes. All animals havethe white tip at a body length of 190 or 200 cm. The length 170 cm mentioned
above corresponds to an age of about 3.5 years. According to age determination ofa few animals, the white tip of the upper jaw is formed at an age between 2 and 12
years. As stage 2 is found in animals of slightly larger length, it is supposed thatthe extent of the white area increases in some degree with the growth of the animal.

Females

Males
A.

c-

• •

2

I

•

• •

0 I

• I

I

• • I I• I • I
•

c.

•

I

•

D. •

• I

I

•

2

• I

•

I

I

I

""""
• .....

I

I

•

I

10 20 30 50 80200
Testes weightc-

I .. xII•-· - - -

• c-1

0 I
1

I

I

I

• I
•
• • I I I
I • •

c-

I

I

c-

•

c-

I

•

I I

.. • I . II

B.

I-·w ..

• I -6••-- - -- •

•
'
'
- -•
....•

a
1

-

1

I

I

I

0 1-2 3-4 5-910Ovulation number

Fig. 21. Relation between the pigmentation of S. attenuata and gonadal condition.
Open circles indicate 20 animals. For other symbols see Fig. 20.

White area at the tip of the lower Jaw
The 4 stages of the development of the white area on the tip of the lower
jaw were defined by the same method used above. The white areas on the tipof upper jaw and of lower jaw show good correlation, and both jaws showed thesame stage in almost all the animals observed (Fig. 19). Accordingly, the mean
body length where half of the animals have the white tip on the lower jaw is thesame as the corresponding figure for that of the upper jaw.
White spots on the dorsal surface
The stage of this character was classified into 4 categories of stage 0 of no
Sci. Rep. Whales Res. Inst.,

No. 26, 1974

STENELLA ATTENUATA

181

spot, of stage 3 of heaviest spot, and intermediate stages 1 and 2. The spot starts
to appear in the earliest individuals at a length of 165 cm (male) or 170 cm (female),
and all animals of more than 195 cm in body length have white spots on the dorsal
surface. The body length where half of the animals have dorsal spots is about
180 cm in males and 170 cm in females. According to age determination all animals
show the spots by the age of 9 years. The density of the spots increases withgrowth of the animal.

Male

Female

A

A

•

•

•

50 ----------•

•

c

-

•

•

••

c

Cl>

--- ·- -- -- ---~50 - - - --- -- --- -- -

Cl>

a..

•

.

50 --

:

•:

•

150

170

190

150

170

190

Body length in cm
Fig. 22. Body lengths where half of the animals start to develop the pigmentationof the adult. Lines are drawn by eye.

Dark spots on the ventral surface.
The density of dark spots on the ventral surface was classified by the same
method used for pale spots on the dorsal surface. The dark spots first appear on
the lower jaw and on the band connecting the lower jaw and base of flipper, thenon other parts of the ventral surface.
The age when dark spots start to develop shows a large sexual difference.
In males it starts to develop between 150 cm and 160 cm in body length or between
1 1/ 4 and 2 years of age. However in females all the animals show the spots at
175 cm or 5 years of age. The body length where half of the animals have dark
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

182

KASUYA, MIYAZAKI AND DAWBIN

spots on the ventral surface is about 153 cm in males and about 170 cm in females.
The former corresponds to an age of 1.5 years and the latter to an age of 3.5 years.
As shown in Fig. 19, the mathematical mean of the stages decreases after
190 cm in males and 180 cm in females. This does not mean the disappearanceof the spots, but indicates that the spots are so numerous as to have contact witheach other. In our method of classification this stage was not separated from theearlier stage because we checked mainly the density of independent spots. This
stage seems to corresponds to the fused stage of Perrin (1969).

Discussion
The typical development of pigmentation is shown schematically in Fig. 23,
and can be summarized as follows. The newborn male starts to develop dark
spots in the ventral and throat region at the age of 1.5 years. The female does not
Body
length Age

Sex(cm) (year)

120

0.5 M and F

153

170

>200
>190

>11
>9

M
F

Fig. 23.

Schematic figure of the pigmentation of S. attenuata at various growth stages.

have the spots at this age but show only slight darkening of the band connecting
the base of flipper and lower jaw. At an age of about 3.5 years the white mark at
the tip of both jaws of both sexes, and dorsal white spots and ventral dark spotsof females start to develop. The white spots on the dorsal region start to develop
in males at an age of about 6 years. Then both kinds of spots increase in density
to fuse with each other, and attain the final adult form at the ages of 11 years inmales and 9 years in females.
The age when the animal attains the pigmentation of the adult coincides wellwith the age at the attainment of sexual maturity. The formation of the white
tip on the jaws coincides with the age of the attainment of puberal stage, and with
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

STENELLA ATTENUATA

183

the time when the animals start to leave the breeding school and join the schoolof immature animals. This suggests that they may be formed by the influence ofsome kind of sex hormone. If there is any function in the white tips of jaws andin the mottled pattern, it seems to be a social and ecological function to help thevisual identification of the species or of the growth stage of the same species assuggested by Yablokov (1963) and Evans and Bastian (1969). However, the probable effect as camouflage suggested for S. plagiodon (Caldwell and Caldwell, 1966)
is not denied in S. attenuata.
The reasons for the delayed formation of dorsal white spots or of earlier formation of ventral dark spots observed in the male are not analyzed here. It may berelated to the difference of endocrinological condition between the sexes.
Table 7 shows the frequency of the pigmentation patterns of females in various
reproductive stages. Though other characteristics of pigmentation do not show
any difference between the reproductive stages of mature females, the density ofdark spots is slightly lower in lactating females. If these data really reflect theratio in mature females, it is supposed that dark spots become less conspicuous inanoestrous females.
In the present data, 96.3 % of sexually mature females and 100 % of sexuallymature males have the white part on the tip of the upper jaw. Animals withwhite tips are scarce in S. attenuata in the eastern Pacific (Perrin, 1969). This difference seems to indicate morphological differentiation between these two populations. In this respect the animals reported from Malaita (Dawbin, 1966) are closer
to S. attenuata in the Pacific coast of Japan. If observations on pigmentation are

TABLE 7.

Characterand stages•l

A

B

c

D

ii

[l
!l

[l
ll

See Fig. 18.

2l

ImmaturePregnant2l

LactatingResting.----'-----..

~.----'-----..

~

no.

%

no.

%

no.

%

no.

%

22
14
2
0
22
13
3
0
20
11
2
0
14
3
7
8

57.9
36.8
5.3
0
57.9
34.2
7 .9
0
60.6
33.3
6.1
0
43.7

0
10
9
0
0
13
6
0
1
8
5
5
0
3
7
9

0
52.6
47.4
0
0
68.4
31.6
0
5.3
42.1
26.3
26.3
0
15.8
36.8
47.4

3
25
18
0
3
30
13
0

6.5
54.5
39.0
0
6.5
65.2
28.3
0
2.2
23.9
39.1
34.8
0
41.3
32.6
26.1

0
8
8

0
47 .1
47.1
5.8
0
58.8
41.2
0
31.3
0
31.3
37.4
0
17.6
35.3
47 .1

9.4
21.9
25.0

11
18
16
0
19
15
12

Pregnant and simultaneously lactating females included.

Sci. Rep. Whales Res. Inst.,

No. 26, 1974

PIGMENTATION OF FEMALE S. ATTENUATA BY
REPRODUCTIVE CONDITION.

0
10
7
0
5
0
5
6
0
3
6
8

KASUYA, MIYAZAKI AND DAWBIN

184

made on many animals along the Malaita coast, it will give some information on
the identification of populations.
The pigmentation of other spotted species S. plagiodon in the Atlantic (Caldwell
and Caldwell, 1966) is distinguished from that of S. attenuata in the Pacific by theabsence of the fusion of ventral dark spots and by the larger size of the spots.
FEMALE BREEDING CYCLE

Graafian follicle
The frequencies of the diameter of the follicle obtained as the cube root of
the multiple of three dimensions are shown in Fig. 24. The ovaries of pregnant
females are inactive having no large follicles in any school or in any season. The
ovaries of all the lactating and the resting females in school 7, which was caught in

10

2

A

s

0

N

D

J

F

M

Month

Fig. 24. Seasonal variation of the diameter of the largest follicle in mature femalesof S. attenuata. Black squares and thick solid lines indicate the resting females,
dotted squares and thin solid lines the lactating, and white squres and dotted lines
the pregnant or pregnant and simultaneously lactating.

July, show high activity. On the other hand in schools caught in November or in
February, there were observed many lactating or resting females with inactive
ovaries. As a result the mean diameter of the follicles of females in the two categories is smaller than that of the schooll killed in Juy. However, even in schools
killed in February or in November the size of follicles of active females is not small.
Accordingly it can not be concluded that all females in February and November
are sexually inactive. It will need observations on more schools in various seasons
to draw conclusions on the seasonal variation of the size of follicles.

Diameter of corpus luteum
Even when we got the ovaries of pregnant female it was not necessarily possible
to obtain the fetus, because the fetus or fetus and part of uterus were sometimes
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

185

STENELLA ATTENUATA

removed by the fishermen and piled elsewhere. - In these cases the pregnancy waschecked by a fragment of uterus or by the condition of ovaries. Table 8 shows
the relationship between the size of corpora lutea and the presence of a fetus.
This table shows that if the corpus luteum is larger than 6000 mm 3 in volume index
it may be correct to consider that the animal was pregnant. The scarcity of corpus
luteum of the size between 4000 and 6000 mm 3 in volume index may indicate thatwhen the ovulation is not successful even if the corupus luteum may grow to asize similar to that of corpus luteum of pregnancy, it may regress very rapidly.
Accordingly, when other information is not available, we tentatively consisderedthat a corpus luteum smaller than 4000 mm 3 in volume index or 15.87 mm indiameter as the corpus luteum of ovulation.
26

14

0

20

40

60

80

Body length in cm
Fig. 25. Relation between the diameter of corpora lutea and body length of fetuses.
Solid line is drawn by least squares, and dotted lines by eye. Open circle indicates a lactating female.
TABLE 8.

SIZE OF LARGE CORPORA AND THE SEXUAL CONDITION OF FEMALE.

Range in volume
index (mm 3)

Diameter(mm)

1001- 2000
2001- 3000
3001- 4000
4001- 5000
5001- 6000
6001- 7000
7001- 8000
8001- 9000
9001-10000
10001-11000
11001-12000
12001-13000
13001-14000
15001-21000

12.60
14.42
15.87
17 .10
18.17
19.13
20.00
20.80
21.54
22.24
22.89
23.51
24.10
30.00

R

L

PL

p

PF

3

Total

3
2

2

1
4
2

2
5

3
1
2
6
2
2
2
6

R: resting. L : lactating. PL : pregnant and lactating, fetus not confirmed. P : pregnant, fetus notconfirmed. PF : Pregnant, fetus confirmed.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

KASUYA, MIYAZAKI AND DAWBIN

186

The relation between diameter of corpus luteum of pregnancy and the bodylength of fetus is shown in Fig. 25. The diameter of a corpus luteum of a pregnant
female with 1.0 cm fetus was so large as to be in the range of corpora with larger
fetus. Though the diameter of corpus luteum does not show a large change related
to the growth of the fetus, there seems to be a slight decreasing tendency. If theregression line is calculated by least squares for the 14 corpora corresponding to
the medium and larger fetuses, it gives the relation y= -0.01825x+23. 700, where
y is the diameter in mm and x is the length of fetus in cm. The mean diameterat the time of parturition is 22.08 mm on the above formula.

Regression of corpus albicans
Fig. 26 shows the frequency of diameters of corpora albicantia in each age
group. The modal diameter gradually decreases with the increase of the age ofthe animal until 14.5 years of age or the 7th year after the mean age at the attainment of sexual maturity. Then the highest peak of the mode stays between 2 and
2

13

11

13

16

12

B

9

4

5

0

17.5

19.5

0

0

14

12

E
E10
.!;
..... 8
<I.I
.....

E6

c
i5 4
2
9.5

115

13.5

15.5

215

235

Age in years

Fig. 26. Distribution of the diameter of corpora albicantia of S. attenuata. The
numbers at the top indicate the number of animals, and the dotted line the positionof the mode.

3 mm in diameter, and the ratio of the corpora number constituting the modeincreases with age. No corpora smaller than 1 mm in diameter were observed.
They indicates that the corpora albicantia attain a final size within several
years after the start of regression and may stay in the ovary all the lifetime. The
mean final diameter suggested by the shape of the mode is about 2.5 mm or slightly
more.
It is easily supposed that the size of corpora albicantia decreases rapidly after
the parturition. If the size of the largest corpora albicantia of lactating females
in each school are arranged by size, some modes are observed. These modes may
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

STENELLA ATTENUATA

187

represent some parturition season. The mean growth curve and the mean modal
length of calves caught in the same school give the time after parturiation. The
length frequencies of juvenile calves and the size frequencies of the largest corpora
albicantia of pregnancy of lactating female in corresponding schools are shown in
Fig. 27. In this figure the few corpora albicantia of ovulation were omitted and
0

I

0.5
I

1.0I

LJ~

14

12

13

11

I

30
40
I I I

I

(year)

D~

D

10
9
8
7
Diameter in mm

2.0
I

6

5

4

I

3

Fig. 27. Comparison of the frequency of the diameter of copora albicantia of thelast parturiation of lactating females and the length frequency of juvenile calves.
Scale in years was calculated from the growth curve. Numbers at the left indicate
the school. The length frequency of school 3 was calculated from the weightdata.
TABLE 9.

LACTATING FEMALES WHICH OVULATED AFTER LAST PARTURITION.

AnimalDiameter of corpus (mm) of

schoolno.

largestlast parturition

3
3
3
3
4
4
4
4
4
4
5
6

3
24
35
38
5
19
47
48
96
119
48
102

4.88
12.35
8.82
12.12
5.37
15.14
10.69
5.24
5.01
8.51
6.46
4.66

4.38
3.29
4.95
3.21
5.30
4.79
5.28
4.78
4.72
6.50
6.12
4.28

*: based on the criterion used in this study.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

No. of ovulation
postpartum

postlactum *

1
3

1
3

1
3

188

KASUYA, MIYAZAKI AND DAWBIN

the probable corpus albicans of the last parturition was used. These exceptional
individuals are shown in Table 9. The mean modal diameters of corpora albicantiaof the last parturition of lactating females are plotted in Fig. 28 against the timeafter parturition. It shows that the regression of the size of corpora albicantia is so
rapid that it regresses from the mean diameter of corpus luteum 22.08 mm to13.6 mm within 0.2 months. Then the speed ofregression gradually decreases, andafter 16th month the diameter decrease is almost straight. If this line is extended,
it reaches the mean final diameter of corpora albicantia at about 70 months. This
coincides with the information described above.
The elapsed time after the start of regression of corpora lutea was calculated

16
14 7

E12

E

,£; 10.....

a;CIJ 8

4

•2

E

.Q 6
Cl

4
2
00

4

8

n

IB

W

~

W

~

~

~

~

~

~

MonthsFig. 28. Regression of the diameter of corpora albicantia obtained from the combinations in Fig. 27. Larger circles indicate reliable combinations, number by theeach circle the school.

from the regression line of the corpora albicantia drawn for volume index andvolume indices of the corpora, assuming that the size of corpus albicans of pregnancy
and of ovulation is not significantly different. This assumption should not be unreasonable, because the corpus luteum of ovulation seems to attain a size near tothat of pregnancy and the regression rate is rapid in the first month. The corpora
albicantia of pregnancy were then identified based on the following assumptions
and considering the reproductive conditions at the time of death.
1. During pregnancy the female does not ovulate.
2. There may be some postpartum ovulations or postlactum ovulations.
3. The time from a parturition to next conception is usually more than one year.
Thus the age of corpora albicantia which started the regression within recent 5
years were calculated and the corpora albicantia of pregnancy and those of ovulation were identified. The real date of ovulation of corpora albicantia of pregnancy
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

STENELLA ATTENUATA

189

is roughly estimated assuming that the length of gestation is 11.2 months. The
date of ovulation of a corpus luteum of the pregenant female was calculated fromthe fetal growth curve and the fetal length. In a few cases where fetal length was
not available the mean feta] length of the school was used.

Postpartum ovulations
The postpartum ovulations were analyzed in relation to the time from thepreceding parturition based on the ovulation diagram prepared with regression
curve of the corpora. The source of information was classified into two. The
first (series A) is the ovarian activity after the last parturition ending at the death10'
f+-r~~~~-,-~~~~~~~~~~io~·_..,_~~~~~~~~~~~~~§ 30''.§:~r,---'.-~~~~~~~~~~~~~::J~101----Y-~_L__>.~~~~~~~-,_

10'o10r,,~L,-~~~~~~~~~~~~~~~~--or

Zd 10"

4~'"~"~--'-~-'--'--~~~--'H~~~~~~~~~~T-lf

Fig. 29. Seasonal variation of ovulation shown in relation to the date of the lastparturition. Females are grouped by the month of parturition (numerals at theleft). The females that are grouped into Jan., Feb., March, and Oct., show no
ovulation, but are included in the sum. Number of ovulations is shown permonth per 100 animals. Based on series A.
TABLE 10.

NUMBER OF POSTPARTUM AND POSTLACTUM OVULATIONS.
Postpartum ovulations

Postlactum ov.

No.
A
0
2
3
Sum
Mean

60
10
2
1
73

82.2%
13.7
2.7
1.4
100
0.234

36
6
9
0
51

B

Total

70.6%
11.8
17.6
0
100
0.471

96
77.4%
16
12.9
11
8.9
1
0.8
124 100
0.331

No.
2
3
4
Sum
mean

B
34
14
2

66.7%
27.5
3.9
2.0
51 100.1
1.412

of the animal, which is more reliable because the time after the parturition is usually,
but not necessarily, short and the reproductive condition of the female at the timeof death was taken into consideration in assessing the corpora albicantia of the last
pregnancy. The next (series B) is the ovarian activity from the parturition that
occurred one cycle before the parturition used in series A and ends at the last conception. The date of parturition of series B is usually earlier than that of series A.
Sci. Rep. Whales Res. Inst.,
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KASUYA, MIYAZAKI AND DAWBIN

190

At the first step the analysis was made on series A. The samples were grouped in accordance with the month of parturition, then the dates of ovulations werearranged chronologically. and the frequency of ovulation per month per animal was
calculated (Fig. 29). This only shows that the ovulations after the recent parturition had occured in various seasons of the year.
To know the range of the time when postpartum ovulations may occur, the relation between the time after the last parturition and the number of ovulations thatso~~~~~~~~~~~'-'-'-'~'-'-"-'...L.LI..LI..L.'-'-'-'-"-'-'-.L.U

0

6

~

a
~
E
Q
~
Months from parturition

IB

~

W

Fig. 30. Relation between the time from parturition and the number of ovulations undergone by each female (numbers at the right). Figure at the top indicates the number of females observed. Based on series A.

occurred after the parturition was analyzed based on the materials of series A (Fig.
30). In some animals ovulation occurs soon after parturition and the number ofovulated females increases. As a result the percentage of unovulated females decreases untill the 12th month, then the percentage becomes rather stable during thenext 12 months. After this the number of unovulated females again starts to decrease. We consider that the former period corresponds to the period of postpartum
ovulations and the latter probably to postlactum ovulations.
Thus defining postpartum ovulations, the time and frequency were obtained
from series A and B (Tables 10 and 11 ). About 20 % of the females have a post
partum ovulation but they seems to be all infertile. The mean number of post
partum ovulations is 0.331 per reproductive cycle.
As shown in Table 11 and Fig. 31 the time of the postpartum ovulation measured from the date of parturition shows some regularity. The first peak is in
the 3rd month after parturition, then next peaks come with the interval of 4 months.
These peaks may, as mentioned in a later section, correspond to the mating seasonof this species. But it must be noticed that some postpartum females do not ovulate
in the first season but in the 2nd or 3rd seasons. The length of interval between two
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

STENELLA ATTENUATA

191

postpartum ovulations was studied on the few females which have experienced two
or more postpartum ovulations. As shown in Fig. 31, if more than 1 ovulation are
made in one breeding season the minimum of the interval is about 1 month. The
longer intervals are approximately a multiple of 4 months.

Postlactum ovulation
The postlactum ovulation was tentatively defined as the ovulation occurring
after 12 months or ~ore from the last parturition, and analyzed only on the series
B because series A does not end at conception. It was not confirmed here whether
the animal has finished lactation by the first postlactum ovulation. However ourdata suggest that it is not necessarily so. As shown in Table 12 the intervil between
the last postpartum and the first postlactum ovulations, on animals where two or
more postlactum ovulations exist) is usually 12 months or more. This means thatthe ovarian activity usually stops for a long period after the last postpartum ovulation. However only in 2 cases among 73 animals the interval was 4.0 or 8.8 months.
In these cases the postpartum ovulation is almost continuous to postlactum ovulation. About 67 %of the females conceive by the first postlactum ovulation, and theremaining experience two or more postlactum ovulations. The mean number of
postlactum ovulations is 1.412 per one reproductive cycle (Table 10).
The peak of postlactum ovulations is observed in the interval of 4 months(Table 11 and Fig. 31). There are some females which do not ovulate at the 4thmonth before conception but do it at the 8th or 12th. The information on postpartum and postlactum ovulations are shown in the diagram of Fig. 32.
The cycle of postlactum ovulation of females which have two or more postlacTABLE 11.
Time in
month
(t)*
n=l
2
3
4
5

6
7
8
9
10
11
12
13
14
18

TIME OF OVULATION MEASURED FROM THE DATE OFPARTURITION OR OF CONCEPTION.
Postpartum ovulation

lst

2nd

2nd**

3

3

3

4
3

4
3

3

3
3
6
7

2

5

2

1
2

3

2
3

2

2

*: Time range (t): n-1 ;;;;t<n,* * : Nearest to postlactum ovulation of pregnancy or the first.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

4th

5
6

5

2
2
4
4
2

3rd

Sum

Sum

3
4

3rd

Postlactum ovulation

KASUYA, MIYAZAKI AND DAWBIN

192

3

2
>.

u

c

<I>
:J

g.... 3

2

lJ..

-1

2

0

3

4

5

6

7

8

9 10 11

12

Interval in months
Fig. 31. Intervals of postlactum ovulations (top) and of postpartum ovulations(bottom), in the animals where several of them are observed. Black indicatesunreasonable case, where the superficial date of ovulation comes after the date ofconception .

.09
.08

•

/\

» .07
:;; .06:.ad .05

{ i

.0
0 .04

....

a.. .03

.

.02
.01
op

2

4

6

8

10 12 14 16

, I:

!l
: !'ii
!\
\ !\:
\! \:
!~
20 18 16 14 12 10 8 6 4c2Time in months
Fig. 32. Diagram of ovulation in one reproductive cycle. The postpartum ovulation is at the left and the postlactum ovulation at the right. P indicates parturition, C conception, dotted lines postpartum ovulation nearest to parturition or
postlactum ovulation nearest to conception, chains the second, thick solid lines
the third, and thin solid lines the total of postpartum ovulation. Probabilityof ovulation is shown by the number of ovulations per animal per cycle. The
fertile postlactum ovulation, of which probability is 1, is not shown. The lengthof the reproductive cycle is set at 50.3 months, one of the estimate of mean reproductive cycle in S. attenuata.

TABLE 12.

INTERVAL BETWEEN LAST POSTPARTUM OVULATION AND
FIRST POSTLACTUM OVULATION.

Interval in month (n)*Frequency

4

9

11

12
2

13
2

17
1

20

24

2

1

29

31

*: Interval is shown by month, n-l<month~nSci. Rep. Whales Res. Inst.,
No. 26, 1974

STENELLA ATTENUATA

193

tum ovulations is classified into two types. One is the cycle of 4 months or a multiple of it. This may be the cycle related to the mating season. The other is shortand is an ovulation cycle in one breeding season. This probable real oestrous cycle
is of about 1 month. These features are quite similar to the cycle found in postpartum ovulations.
Accordingly it is concluded that S. attenuata is polyoestrous and the oestrous
cycle is about 1 month, and this oestrous cycle occurs m some of the breeding
seasons which have an interval of 4 months.

DJFMAMJ

JASON

50

40
30

20
10
,__

J)

---~--=

oiJ:::::::r11:

14

E

~ 12

10

8
6
4
2
OJ

FMAMJ

J

AS

ONO

Month
Fig. 33. Breeding season of S. attenuata. Top indicates the monthly frequency ofparturition calculated from the length frequencies of fetuses and juvenile calves
younger than 2 years of age. Bottom indicates the frequency of the date of conception calculated from the ovulation diagram. The scales of date of conception(bottom) and that of parturition (top) are moved apart for 11.2 months, thelength of gestation. White areas indicate conception within 1 year before thedeath of the animal, the dotted that between 1 and 2 years, the black that between 2 and 3 years, and the shadowed that between 3 and 4 years.

Breeding season
The parturition seasons are calculated from the mean growth curve and length
frequencies of juvenile calves and of fetuses (Fig. 33). As the apparent mating
season differs between schools, it is necessary to observe many schools and a wide
chronological range in obtaining the information on the mating season of the species.
Sci. Rep. Whales Res. Inst.
No. 26, 1974

KASUYA, MIYAZAKI AND DAWBIN

194

However after the attainment of 2 years of age, it is impossible to estimate the dateof birth because the growth of the calf becomes too slow compared with the range ofindividual variation of the body length. By this method the reproductive activityof the females in the most recent 3 years can be estimated. The date of conception
was obtained by sliding the chronological scale of the parturition season for 11.2
months.
In all the 7 schools the peak of conception calculated from the fetal length isin July and August. This strongly suggests that one of the mating seasons of thisspecies is in these months. The result calculated from animals born within one
year is almost similar to that obtained from fetuses, but there appears another small
peak of conception in January. Though the information obtained from the calvesborn between 1 and 2 years before death is inaccurate, there seems to be peaks ofconception in February, in May and June, and in September. But when all aretotaled there remain only two peaks of conception one in July and August, and theother in January and February.
The bottom of Fig. 33 indicates the frequency of conception in the past 4 years
obtained from the size of the corpora albicantia of pregnancy. In this figure the
100
90

24

80
0.S 70

22

0

?: 60
.....

<II

lL

50
40
20

0

.

'
'' ' 'D Jy·','/ "'· ...

'o'

30

Vl

c

20
0
18 s>

'

'\

,''

\,.-

~·

: 16 00
14 zcii
12

FMAMJJASOND

Month
Fig.' 34. Seasonal change of frequency of ovulations (solid line) and of the ratio of
fertile ovulations (dotted line). Ovulations in the recent 4 years studied are
combined.

date of conception corresponding with the corpora lutea of pregnancy was calculated
from the length of fetus. There seems to be three peaks in the conception occurred
between the past 1 and 4 years. However it is also possible to read in the totalheight two main peaks of mating between May and September, and between
November and March, each of which having one accessory peak in it. This feature
coincides with the seasonal change of the ratio of fertile ova to the total number ofovulations (Fig. 34 ). The ratio of fertile ova is higher in the two mating season.
However the frequency of total ovulation shows another feature. As expected fromthe 4 months cycle of ovulation, there are observed three peaks in January to
Sci. Rep. Whales Res. Inst.,
No, 26, 1974

STENELLA ATTENUATA

195

March, July, and October and November.
The above three sets of data on mating seasons do not coincide well. Between
the first two methods (Fig. 33), the peaks around February and that in July coincide.
This first method is good in accuracy but covers too short period. On the other
hand the second method covers a longer period and suggests the other peak in December, but the accuracy of dating is less reliable. The third method or the frequency of ovulation, which is similar to the second but includes all the ovulations,suggests a mating seasons of four months interval. To increase the accuracy of thesecond method, if the dates of the conception at each end of the series B or the selected reproductive cycles used in the former section is considered, there is observed
three clear peaks of conception (Table. 13). Two of these mating seasons coincide
well with those obtained from Fig. 33. The third peak in November coincides approximately with the corresponding peak in Fig. 33 (bottom) and frequency ofovulation in Fig. 34. Then the interval of the peaks are 4 months which is suggested by the postpartum and postlactum ovulations.
As a conclusion, though more confirmation is necessary, we are inclined to expect three mating seasons with the peaks in February and March, in July, and in
TABLE 13.
MonthFrequency

MONTHLY DISTRIBUTION OF DATE OF CONCEPTIONOBTAINED FROM SERIES B.

Jan.

Feb.

Mar.

Apr.

May

Jun.

July

Aug.

Sept.

Oct.

Nov.

Dec.

1

7

4

1

1

5

14

5

1

4

4

4

November. The last two mating seasons coincide with the seasons of just after thenorth bound and south bound migrations, and the first just before the north boundmigration. However it is probable that the migration is affected by the breeding
cycle and there is a segregation of '.females in different reproductive conditions.
The parturition seasons seems to be about one month ahead of the mating peaki.e. in Jannuary and February, in June, and in October.

Reproductive cycle
The mean length ofreproductive cycle can be obtained from the ratio of various
reproductive conditions assuming the 11.2 months for the approximate length ofgestation. When the data of all the schools are combined the number of pregnant
females is 64 or 25.6 % of mature animals, including each half of the number of animals which are simultaneously lactating and pregnant into both categories (Table
27). The length of lactation 140+64x 11.2=24.5 months is calculated. By thesame method the length of resting 8.1 months, and the length of one reproductive
cycle of 43.8 months or 3.65 years are obtained.
If the samples are obtained evenly from various seasons in a year and covers
schools of various reproductive stages, this method gives good information on themean length ofreproductive cycle. However, as can be seen in Table 27, the samples
were collected mainly in October and November, and the frequency of mature females constituting the reproductive stages shows wide between school variation. In
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

196

KASUYA, MIYAZAKI AND DAWBIN

this condition we cannot expect the accuracy of the method. Another problem
is the presence of females which are sexually mature but in which the reproductive stage was not identified. This kind of imperfect observation is usually madeon animals whose reproductive organs have been removed by the fishermen andprecise study was not made. On this case the identification of pregnant females isusually possible based on fragments of uterus. However it is very difficult to distinguish the resting animal from the very early stage of pregnancy. Accordingly
the real ratio of resting animals, which represent the sexually mature females other

100

9

21

22

16

15

21

14

4

7

5

5

7

4

7
9
11
No. of ovulations
13

7

a

5

3

3

17

13
3

2

o o

0

~ ~t~t~ Hlil\~l\ ~llfa@

1·::·:·:·:·:·:·····:·:·:·:·:·:·:

11.5

9.5

23.5

21.5

19.5

15.5
13.5
Age in years

Fig. 35. Change of the ratio of sexual conditions by age in mature females of S.
attenuata. Black indicates pregnant females, black with white spots those pregnant and simultaneously lactating, white with black spots those lactating, andlines those resting. The number at the top indicates sample size.
TABLE 14.

No. ovulations

1- 6
7-12
13-18
Total
Age (years)

7.5-11.5
12.5-17.5
18.5-23.5
Total

RATIO OF REPRODUCTIVE CONDITIONS AT THE TIME OF DEATH
AMONG MATURE FEMALES OF VARIOUS AGE GROUPS.
Pregnant

Preg. & Lact.

Lactating

Total

no.

%

no.

%

no.

%

no.

%

no.

%

Reproductive
cycle(Months)

24
8
2
34

23.1
19.0
20.7

5
0
0
5

4.8
0
0
3.1

55
30
8
93

52.9
71.4
44.4
56.7

20
4
8
32

19.2
9.5
44.4
19.5

104
42
18
164

100
100
100
100

40.2
58.8
100.8
50.3

15
13
0
28

24.2
16.9
0
19.4

3
2
0
5

4.8
2.6
0
3.5

33
44
5
82

53.2
57.1
100
56.9

11
18

17.7
23.4
0
20.1

62
77
5
144

100
100
100
100

38.6
57.5

Resting...------.. ---------... ---------... ---------... ---------...

II. I

0
29

52.9

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

STENELLA ATTENUATA

197

than pregnant or lactating, may be higher than that observed. Accordingly thereal mean reproductive cycle must be longer than 43.8 months.
Table 14 and Fig. 35 shows the change of the pregenant ratio accompaniedwith increase of age. They show that the ratio of pregnant females decreases andlength of reproductive cycle increases in the older animals. The length of reproductive cycle calculated by adding all the ovulation classes or age classes are 50.3
and 52.9 months respectively. As these calculations are based on observation ofreliable materials, the figures obtained are more reliable than the 43.8 months cycle
obtained from Table 27. Furthermore as the ovulation data used in Table 14 represent 96.5 %of all the available ovulation data, the figures obtained from it seems
to be the best estimate of the mean reproductive cycle of the present population of
Stenella attenuata in Japanese coastal waters. It gives the length of gestation 11.2
months, lactation 29.3 months, resting 9.8 months, and i:otal length of reproductive
cycle 50.3 months or 4.19 years.
The mean length of reproductive cycle is obtained separately from the frequency of ovulations of conception. It is generally observed in the ovulation
diagram that the presumed dates of ovulation are not very reliable in the case of 5
years or older corpora albicantia, and that it is almost impossible to distinguish thecorpora of pregnancy and of ovulation on the diagram of that part. This is clearlyshown in Table 15, where numbers of corpora albicanta of preganancy and of ovuTABLE 15. REPRODUCTIVE PARAMETERS CALCULATED FROM OVULATIONDIAGRAMS IN RELATION TO THE INTERVAL FROM THE DATE OF DEATH.
Year

lst

2nd

3rd

4th

5th

6th

A. Sample size (No. X Month)
B. Fertile ovulationc. Total ovulation
D. Pregnant ratio (BX 11. 2 7 A)
E. Mean annual ovulation (C7AX 12)

1159
21
40
0.20290.41421464
22
380.16830.31151424
24
440.18880.37081312
31
670.2646
0.61281162
37
1040.35661.0740673
27
89
0.4493
1.5869lation are shown together with the number of animals (no. X months). In thistable the pregnant ratio and mean annual ovulation rate show smooth fluctuation
until the 4th year from death, but they show higher fluctuation after the 5th years.
The mean of the pregnant ratios in the recent 4 years in Table 15 is 0.2062, which
gives the length of reproductive cycle as 54.3 months or 4.63 years. This figure isvery close to the figure 50.3 or 52.9 months obtained from the ratio of various reproductive conditions of individuals of known age.
The individual variation of the length of reproductive cycle is obtained,though it is unsatisfactory, from the ovulation diagram. Fig. 36 shows the relation
between the time after the last partutition and reproductive stage at the time ofdeath. It shows that some individuals finish lactation at about the l 7th monthafter parturition but some animals continue lactation for about 60 months or 5 years
after parturition. If the length of lactation means the length of the suckling
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

198

KASUYA, MIYAZAKI AND DAWBIN

period, the calf may continue to take both milk and solid food until the age of 17months in the shortest case or of 60 months in the longest case after starting to feedon solid food at the age of about 9 months. It is highly probable that the lactation
is finished in the usual shortly before the conception, and that the lactation lasts
longer on an animal of which interval between conceptions is long.
The length of lactation can be presumed from a direct comparison of thenumber of juvenile calves and that of lactating females caught together (Kasuya1972). This method does not give the mean length of lactation but the longest
range. At first step, the body length where the cumulative length frequency ofjuvenile animals coincides with the number of lactating females (Table 27) was obtained as shown on Fig. 37. Schools 5 and 7 were excluded here because the number
2
2(/'I 3.£1..c. ~"""'~"""'"""".......~~"--"'"'-'~~~~~~~~~
00.1 l----"""------=---=---=----'=---~..,.__ _ _---:i6-0 3

0 1~~_.E-l;,;;;;;;;____r""""L-"'"""'-...Efil-=""""'"-=---'""l,,,,---..,....,_---",,,_---1

zd 1 f"....."--.L'."'------"=q=---"'"'--=-- --"'"---""'"""'""'--------I
8

6
4
2

0

6

12

18

24

30

36

42

48

MonthsFig. 36. Relation between the sexual condition at the time of death and the lengthof time after last parturition, obtained from the ovulation diagram series A.
Black dots indicate lactating females, lines the resting, white dots the pregnant,and black the females lactating and simultaneously pregnant. Numbers at theright show the school.

of investigated lactating female was too few. On Fig. 35 the results obtained fromschools 2 and 6 give a very small length (correspond to 1.0 and 1.75 years respectively), so they will not give the real length oflactation but will show only that there
were no large suckling calf in the school. Accordingly the informations obtained
from schools 1, 3 and 4, or the length 169 cm, 178 cm and 175 cm respectively, wereused here. Then the modal lengths of the peak which includes the above bodylengths were obtained on Fig. 2. They are shown in parentheses in Fig. 35. The
ages corresponding to these modal lengths read on the mean growth curve are 4.0,
5 1/4 and 4.0 years respectively. For the comparison, same method was applied
for the age frequencies of the schools 3 and 6. In these schools the ages of all theSci. Rep. Whales Res. Inst.,
No. 26, 1974

STENELLA ATTENUATA

199

young animals of known length were determined. The length of lactation obtainedby it was 5.5 years (school 3) or 1.5 years (school 6), showing a good coincidence withthat obtained from the body length frequencies. These result indicates that in someanimals the lactation lasts for 4 or 5 years, even if there are many females whichfinish the lactation within a shorter period.
The date when the female starts the next pregnancy, or that enter into thenext cycle after weaning the calf, is calculated by estimating the date of conception
from the length of fetus. Fig. 38 indicates that some females enter into the next
pregnancy at about 18 months after the last parturition. After this date, the numberof females which enter into the next pregnancy increases rapidly. At 28th monthafter parturition there begins to appear the females which give birth to the next

100
<II
01
ctl

'E 80
<II
....
<II

'' ''

0. 60
<!J

''
''

~

.' ''

l)

I

.:::

:; 40

E
:::J
u

o

''
'I
'I

I'

20

,....,1

--.,1

QI

01

0) 1

~:

0

I~

1 00

B: t:.• .§?:
100

120

140

160

U")

1

I(()

:::: :;::::
180

Booy length in cm
Fig. 37. To ascertain the maximum length of lactation, the cumulative frequency
of calves is compared with the number of lactating females. Numbers at the top
indicate schools. For further explanation see text.

calf and complete one reproductive cycle. The time when all animals complete
the reproductive cycle is about 68 months. This information on the length of reproductive cycle coincides approximately with that obtained by other methods. In
this method, as the abundance of lactating female is underestimated comparedwith that of pregnant females, it is incorrect to presume the mean length of reproductive cycle as the time when 50 % of females finish the cycle.
Fig. 39 shows the length frequency of reproductive cycles based on 67 cyclesof 64 animals obtained from the series B. As the ovulation diagram covers only
about 65 months, the frequency of long reproductive cycles is underestimated andthe cycles longer than 60 months are entirely neglected. However this can give a
Sci. Rep. Whales Res. Inst.,
No. 26, 1971:

KASUYA, MIYAZAKI AND DAWBIN

200

C!>

g'50

.....c
C!>

u

Q; 40
a.
20

Fig. 38. Length of reproductive cycle calculated from the data in Fig. 36 andlength of fetuses. The dotted area indicates the females which have finished thecycle after giving birth to the calf. Scale at the top indicates the number ofmonths from last conception, and that at the bottom months from last parturition. L, lactating. R, resting. P, pregnant. PL, pregnant and lactating.
16r-----;=-----J.---------==i100
90
14

80

12

70

gi 10

60

c<II 8

50

C!>

u

40

~ 6.

a..

30

4

20

2

10

·:·:·:·:·:·:·:-::·:·:·:·:
56

60

Fig. 39. Frequency of the length of reproductive cycle in months obtained as theinterval between the dates of two ovulations of pregnancy (left scale), and its
cumulative frequency (solid line and right scale). Arrow indicates the positionof mean length of the cycle.

rough idea on the range of the length of reproductive cycle. An exceptionallyshort reproductive cycle is about 23 months, but most of the cycles are more than
29 months. This means some few females start the next pregnancy at the 12thmonth after the former parturition but more usually at the 18th or later months as
indicated in Fig. 38.
As the length of reproductive cycle changes with age, the reproductive parameters must be obtained in relation to the age of the animal. At first step theSci. Rep. Whales Res. Inst.,
No. 26, 1974

STENELLA ATTENUATA

201

number of animals, number of fertile ovulations, and total number of ovulationsin the recent 4 years were calculated on the ovulation diagram for each group of
females classified by the number of ovulations at the time of death. Then themean values of various parameters in the past 4 years were calculated (Table 16).
The constants of the regression lines calculated by least squares are shown in thesame table, and by the lines in Fig. 40. It shows that the mean length of a reproductive cycle increases rapidly from 3.6 years of the young animal to 6.5 years forthe old animal. This prolongation of reproductive cycle in old females is not produced by the cessation of ovulation, but by the increase of unsuccessful ovulations.
The fertility ratio of ova decreases from 64 %of young animals to 32 %of old animals.
On the other hand the number of annual ovulation shows a very slight increase
with age. Anyway such a long mean reproductive cycle of old females suggests
Calculated age

No. of ovulations
Fig. 40. Relation between age and reproductive parameters obtained from theovulation diagram. 1 indicates pregnant ratio (left scale), 2 annual ovulation
rate (left scale), 3 fertility ratio of ovum (left scale), 4 number of ovulations in a
reproductive cycle (right scale), and 5 length of reproductive cycle in years (rightscale).
TABLE 16. REPRODUCTIVE PARAMETERS CALCULATED FROM OVULATIONDIAGRAMS OF THE PAST 48 MONTHS IN RELATION TO THE
NUMBER OF OVULATIONS AT DEATH.
Number of ovulations at death
Sample size, No. X Month
Fertile ovulationc. Total ovulation
D. Pregnant ratio
E. Mean annual ovulation
F. Ovulation per reproductive cycle
G. Length of reproductive
cycle, Month
H. Fertility of ovumA.
B.

* y=ax+b.

13-15

16-18

1606
959
733
565
1474
23
21
12
12
36
50
67
33
26
28
0.2735 0.1604 0.2453 0.1834 0.2379
0.4071 0.5006 0.4129 0.4256 0.5947

288
3
10
0.11670.4167

1-3

4-6

7-9

10-12

b*

-0.00584 0.2584
0.00327 0.4286

1.389

2.913

1.571

2.167

2.333

0.333

0.0817

1.518

40.94

69.83

45.67

61.08

47.08

96.00

2.119

39.97

0.72000.34330.63640.64150.42860.3000-0.01923

0.6643

D=BX 11.2-;.-A, E=C-;.-Ax 12, F=C-;.-B, G=A-;.-B, H=B-;.-C.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974a*

KASUYA, MIYAZAKI AND DAWBIN

202

that their participation in reproduction is almost negligible.

Accumulation rate of corpora albicantia
The corpora albicantia with clear yellow or yellow brown colour and haveno internal structure typical of usual corpora albicantia nor typical external scar
were considered to have been derived from atretic lutealized follicles (Harrison
and Ridgway, 1971), and were not included in the number or corpora albicantia.
The number of corpora atretica was counted, if found, when the number of corpora
albicantia and lutea was counted. The relation between number of ovulations andof corpora atretica is shown in Table 17. However if they had been searched formore intensively, the number might have been more than that shown here.
No corpora atretica are observed in immature animals. However, in themature animals, corpora atretica ranging from 0 to 13 in number were observed.
It does not seem to increase with the age of animals. This may be because the sizeof corpora atretica decreases rapidly and many of them have been overlooked.
But at present the possibilities are not denied that corpora atretica are formed frequently in young animals or that very few corpora atretica are erroneously included
as corpora albicantia.
Ohsumi (1964) showed on S. attenuata that the left ovary is precocious and thenumber of ovulations in the left ovary usually predominates that in the right.
Among the present 171 pairs of mature ovaries, 162 pairs or 95. 7 % of the total females had the higher number of corpora in the left ovary. This supports his result.
TABLE 17.
No. ofovulations
0
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18'
Total

0
126
10
18
18
16
13
18
10
6
4
2
6
4

RELATION BETWEEN NO. OF OVULATIONS AND NO. OF
CORPORA ATRETICA OBSERVED.
2

3

4

5

6

7

8

9

10

2
3

2
3

2

2

3
2
2
260

20

6

0

2

3

2

0

0

13

mean
0
0.09
0.77
0.74
0
0.47
0.41
0.47
0.57
0
2.00
0.14
0.20
2.50
0.60
0.33
6.00
1.33
0.50
0.33

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

STENELLA ATTENUATA

203

However, the presence of 8 pairs (4. 7 %) of ovaries, in which the number of corpora
in right ovary exceeds that in the left, indicates that there may be few females which
do not show the precocity of left ovary. The same number of corpora in each ovary
was observed only in one (0.6 %) female. These few females should be dealt withseparately in analyzing the ovulation activity of the females with precocious leftovary.
Fig. 41 shows the mean number of ovulations in one ovary plotted against
the number of ovulations in both ovaries. It is considered from this figure that theright ovary of some of the females with a precocious left ovary starts to ovulate at
the age of 6 to 10 ovulations. But most of the left ovaries cease the ovulation at 13
or 14 ovulations when the right ovary take the place of left ovary. The mean number of ovulations at this stage calculated from 13 females with 13 or more corpora
is 13.5. The thick solid and dotted lines in Fig. 41 indicate the mean ovulation activity of the female with a precocious left ovary. On the other hand the bilateral
18

16

>- 14
~

i; 12
(!)

c 10

0

.!: 8

0"' 6
e-

8 4

-

1

a s m n~-~·ll-+--+---t--1

a

~

m

IB

n

IB

Total no. of corpora

Fig. 41. The asymmetry of corpora number in the ovaries of S. attenuata. Blacksquares indicates the frequency of corpora in left ovary, the white that in rightovary, closed circles and thick solid line the mean number of corpora in the leftovary of the female with precocious left ovary, and open circles and dotted linethat in right ovary in the same animal. Three thin solid lines indicate the casewhere all the corpora are in the left ovary or in the right ovary, and the cases
where both ovaries have the same number of corpora.

asymmetry is not clear in females in which the corpora number in the left ovary
does not exceed that in right ovary. This may mean that the right ovary of these
individuals starts to ovulate at a younger age, or that both ovaries ovulate equally.
Possibly both cases occur in these individuals.
The accumulation rate of corpora albicantia in one reproductive cycle wasshown to change from 1.6 of youngest animals to 3.0 of oldest animals (Fig. 40).
The mean accumulation rate of corpora in all the age groups is obtained by totalling the mean number of postpartum ovulations and that of postlactum ovulations(Table 10). This method gives the value 1. 743 for the mean number of ovulations
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

KASUYA, MIYAZAKI AND DAWBIN

204

in one reproductive cycle. This value corresponds in Fig. 40 to the value at the ageof 3 ovulations or 12.8 years of age calculated by the method mentioned in a later
section.
The number of ovulations experienced before the first pregnancy is obtainedby two methods. One is to use the ovulation diagram. In some recently matured
females the number of ovulations undergone before the first pregnancy is directly
counted on the ovulation diagram (Table 18). The mean of these ovulations is
1. 784, which is fairly close to the number of ovulations per one reproductive cycle
obtained as above and to the value obtained on Globicephala melaena (Sergeant,1962). The second is the method of Sergenat (1962). If the female attains thesexual maturity at age between 5.5 and 10.5 years of age and minimum length of
reproductive cycle is 2 years, most of the young pregnant or lactating females may bein the first cycle of reproduction (Table 19). In this table the animals shown by
italics were excluded from the calculation because they are considered to be in thesecond cycle. Then the mean number of ovulation 2.08 was obtained from 13 animals, which is too high compared with the values obtained by the above two
methods. This is possibly because some postpartum ovulations, or females in thesecond cycle are included.
Accordingly we conclude that, though it may change with the age of the animal, the mean number of ovulations in one reproductive cycle is between 1. 7 and
1.8, and that it will not be very different from the number of ovulations undergone
before the first pregnancy.
The relation between the number of ovulations and the age determined by
the dentinal growth layers is shown in Fig. 42. The highest annual accumulation
TABLE 18. NUMBER OF OVULATIONS UNDERGONEBEFORE THE FIRST PREGNANCY(FROM OVULATION DIAGRAM).
Frequency
No. of ovulations
1
2

3
4

TABLE 19.

no.

%

19
9
7
2

51.4
24.3
18.9
5.4

NUMBER OF OVULATIONS IN RECENTLY MATURED PREGNANT
OR LACTATING FEMALES.
No. of ovulations

Age
2
7.5
8.5
9.5
Total

3

4

5

6

7

8

9

10

1
3
3
4

2
1

2

5

3

l+l

1
1
2

1
1

1
1

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

205

STENELLA ATTENUATA

rate of the corpora is 3.0 on the figure and the lowest 0.50. The relation between
the number of ovulations (y) and the age (x) of the mature females, y=0.821 x-:3.967, was obtained by least squares. If this annual accumulation rate 0.821 15
applied to the mean length of the reproductive cycle 4.19 years, the number of ovulations in one reproductive cycle must be 3.44. Even if the shorter and less reasonable estimate of reproductive cycle 3.65 years is adopted the ovulation in one
cycle is 3.00. These values are higher than any other values obtained in this section, and considered to be unreasonable.
The open circles and dotted line in Fig. 42 indicate the mean age corresponding to each number of ovulations. This dotted line is almost vertical after the attainment of 12.5 years of age. As the annual ovulation rate does not change muchwith the age of animal (see Fig. 40), this tendency must indicate that the age of theanimals older than that point is underestimated. This age corresponds roughly ~othe time when the poorly calcified secondary dentine starts to be accumulated in
!
..-··

16

••• .114

l!! 12
0

B10
:;
>
oa
0

+
+

d6

z

4
2

0

I
7.5

9.5

115

13.5

15.5

17.5

Age in years

195

215

235

Fig. 42. Relation between number of ovulations and age of S. attenuata estimatedfrom the dentinal layers. Open circles and the dotted line indicate the mean age
in each ovulation number, closed circles and thick solid line the mean number ofovulations in each age class, thin solid line the relation between ovulation andage calculated by least squares, and cross marks the number of ovulations estimatedfrom the ovulation diagram.

the pulp cavity and age determination becomes difficult. As physical maturity ofthis species is attained by the age of 11.5 years, it will be concluded that after the attainment of physical maturity the secondary dentine is accumulated and reliable
age determination becomes impossible by the present technique.
A similar feature is expected even in Stenella coeruleoalba. Though K.asuya(1972) obtained the number of ovulation-age relationship y=0.69x-5.16, theSci. Rep. Whales Res. Inst.,
No. 26, 1974

206

KASUYA, MIYAZAKI AND DAWBIN

fitness is poor in younger animals. And the relationship between mean ages andnumber of ovulations is almost vertical after the age of 14 years. This is an indication of underestimation of the age. If 13 years of age or younger 15 females selected from his data (Kasuya 1972, Fig. 14), excuding one 10 years old female whichshows too high count of the corpora, are used, 0.325 is obtained as the annual
pvulation rate. This value is less than the half of the annual ovulation rate estimated by Kasuya (1972).
It is impossible to use a similar method to estimate the real ovulation rate ofS. attenuata, because reliable age determination is possible only for a shorter period.
The real annual ovulation rate of S. attenuata was calculated from the relation between the annual ovulation rate and the number of ovulations (Table 16).
Yt = 0.00327xt+0.4286

where Yt is the mean annual ovulation rate between the age t and t-4 years and Xt
is the number of ovulations at the age oft years. This formula means that the annual ovulation rate is approximately 0.432 at the first year after the attainment ofsexual maturity and 0.487 at the age of 18 ovulations which is the oldest animal
observed. These values are higher than the corresponding value obtained in S.
coeruleoalba, but coincides with our observation that simultaneous ovulation is rarein S. coeruleoalba. A Tursiops truncatus matured and died in captivity had undergone 7 ovulations in 15 years (Sergeant et al, 1973) showing an ovulation rate,
0.465/year, similar to that of S. attenuata.
The number of corpora albicantia and lutea at age t is obtained from the above
formula. If the constants of the above formula are shown by a and b, it is rewritten as follows.
or1b
Xt+l = - --xt+-- 1 -a
1 -aHere, if the age at sexual maturity is shown by m, the number of ovulations at n
years after sexual maturity is shown by the following equations,
Xm

=1
n

Xm+n

= rn+b 1:; rnn=lwhere n is interger and r is (l-a)- 1 •As a and bare obtained from Table 16, the number of ovulations at age m+n is
calculated from this formula. The age corresponding to each ovulation number was
obtained on the graph and shown in Table 24. The oldest animal observed had
undergone 18 ovulations corresponds the age of 45.2 years. However as an animal·with many corpora may have undergone an annual ovulation higher than the average, the observed real maximum age is considered to be less than 45 years.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

STENELLA ATTENUATA

207

LIFE TABLE
Litter size
Among 59 confirmed pregnancies, twins were observed only in two females inschool 1., the other 57 pregnancies were single. Accordingly the ratio of twins in
total pregnancy is 3.39 %, and the mean litter size is 1.034.

Sex ratio
The sex ratio is shown in this paper by the number of males per one female.
It is shown in Tables 20 and 21, and Fig. 43 that the number of males exceeds thatof females in the fetus and newborn animals. Then the ratio of male constantly
decreases to attain the sex ratio of 0.579 in the age groups of more than 10 years ofage where animals of both sexes have attained sexual maturity. As males attainsexual maturity 2 years later than females, the sex ratio of mature animals is very
low. When calculated from length frequency it is 0.380, and when calculated from
10 years or older males and 8 years or older females it is 0.440. Probably the former
figure is close to the truth because it is based on much more data. A similar ten-

TABLE 20.

Sex

Fetus

Juvenile 1l

Puberal2 l

Mature 3l

Total

2
J

5
3
0.600

10
0.700

13
14
1.077

58
29
0.500

86
53
0.616

2

2
J

14
19
1.357

38
33
0.868

22
44
2.000

105
31
0.295

179
127
0.709

3

2
J

0
2

3
7
2.333

2
5
2.500

18
11
0.611

23
25
1.087

4

2
J

0
2

3
10
3.333

11
16
1.455

45
32
0.711

59
60
1.017

5

2
J

0
3

3
4
1.333

1
4
4.000

11
0
0

15
11
0. 733

6

2
J

3
2
0.667

12
14
1.167

21
2.100

59
15
0.254

75
52
0.693

7

2
J

2
2
I.OOO

0
5

2
11
2.200

17
1
0.059

21
19
0.905

Total

2
J

24
33
1.357

69
80
1.159

52
115
2.212

313
119
0.380

458
347
0.758

SchoolIJ

SEX RATIO OF S. ATTENUATA BY SCHOOLS AND LENGTH RANGES.

7

up to 165 cm, 2> 166cm to 181 cm (2), or 194cm (J), 3> more than 182cm (2), or 195cm (J).

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

KASUYA, MIYAZAKI AND DAWBIN

208

dency of the ratio in relation to the age of animal is also found in Globicephala melaena(Sergeant, 1962).
There are three possible reasons for the fluctuation of sex ratio. One possibility is the segregation of adult males. Though it may exist in the puberal stage,
there is observed no rapid change of sex ratio at the ages corresponding to thesexual maturity of the animal. Accordingly this possibility cannot explain all thephenomena. The other possibility is the difference of catchability between sexes.
As males are always single, they might find more chances to escape from the chasing boats. However, the fact that the sex ratio continuously decreases with age
even before the attainment of sexual maturity denies this hypothesis.
The only certain reason is the higher mortality of the male. As physical maturity is attained slightly earlier in females and age determination by the dentine

200
1.60

.g0 120
.
....

.80

x

(!J

(j)

.40

0
30
(/)
c
:.c 20
.Q.
0

"0

Males

10
0
Females

zd 20
10
0

0

4

8

12

16

20

25

Age in years
Fig. 43. Relation between sex ratio and age of the animal presumed from thedentine layers. Crosses indicate the mean sex ratio in Table 21.

TABLE 21.

SEX RATIO OF S. ATTENUATA BY AGE DETERMINEDBY DENTINE LAYERS.

Age
range
0>
3;;:;,
8>,
10>,
13>,

> 0
> 3
> 8
>10
>13
Total

mode
-0.5
1.5
5.5
9.0
11.5

Female
no.

Male
no.

Sex ratio

24
29

33
45
39
34
31
46
195

1.375
1.552
1.114
0.810
0.517
0.630
0.816

35
42
60
73
239

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

STENELLA ATTENUATA

209

layer becomes difficult, if the mortality rate of both sexes is equal there must be observed more old males than the females. However as shown in Fig. 43, the numberof males of the age more than 16 years is only 6, whereas the corresponding numberof females is 34. This indicates that the mortality of the male is much higher thanthat of the female.
If the mortality of the male can be higher than that of female in any stage ofthe life, it is reasonable to expect that the sex ratio may change even in the fetal
stage. But this problem was not analysed in this paper. When the mortality
coefficient of male is shown by m, that of female by µ, and the sex ratio at birth bya, the sex ratio at the age oft years can be shown by the formula in the below.
Sex ratio = a·e-<m-µlt
The a and m- µ are obtained from the 5 mean sex ratios in Table 21. The data on
animals older than 12.5 years were not included because age determination bydentine growth layer is in some case unreliable. The a and m- µ calculated by theleast squares are 1.568 and 0.08348 respectively. This indicates that 38.94 % of
total number of newborn calves is female. The age when the both sexes are equalin number is 5.4 years of age. In other species of mammals such a high sex ratio
at birth is observed in red deer (Asdel, 1964).

JV!ortality and recruitment
Fig. 44 shows the age frequencies of the 239 females and 195 males based on theage determined by the dentine growth layers. The age is grouped into nearest
n+0.5 years, where n is an integer. Each half of animals at the age of 1.0, 2.0,
and 3.0 years were divided into age groups of younger or older animals.
The number of animals between 3 and 8 years of age is small. This categoryof animals may have left the breeding schools which we had the chance to study.
The highest frequency of females is in the age group of 12.5 years and that of males
10.5. If the mortality is constant after this year and the age determination is correct,
there is expected to be the following equation,
It = loe-µt

where t is the age of animal in years, It the number of animals at age t, and µ the
mortality coefficient. The mortality coefficient of the animals of both sexes morethan 12.5 years old were calculated by the least squares. It gives the mortality
coefficient,µ = 0.3545

or the annual mortality rate,
M = 1-e-µ = 0.2985

The mortality coefficient of mature females can be calculateed by anothermethod, based on the annual ovulation rate. The age frequency calculated with
the Number of ovulation-Age relationship is shown in Table 22 and Fig. 45. The
mortality coefficient and mortality rate of mature female, µ and M, calculated forSci. Rep. Whales Res. Inst.,
No. 26, 1974

210

KASUYA, MIYAZAKI AND DAWBIN

Fig. 44. Age frequency of S. attenuata based on the dentine layers. Open circles
and dotted line indicate females, and closed circles and solid line males. Crosses
show the total of both sexes including animals of unknown sex. Straight line wascalculated by least squares for all animals of more than 12.5 years of age.

TABLE 22.

No. of ovulations
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
No. of the mature

FREQUENCIES OF NO. OF OVULATIONS AND OF AGE
CALCULATED FROM NO. OF OVULATIONS.
School no.

Calculated
age
8.2
10.5
12.8
15.0
17.3
19.6
21.8
24.0
26.2
28.4
30.5
32.6
34.8
36.9
39.0
41.1
43.1
45.2

Total
22
1
9
4
4
5
6
3

2

3

4

5

6

64
4
2
5
5
2
3

5
2

15
3
2
4
3
5
3
2

5

13

2

4
4

5
5
3

7

3
3
2

1
2

2

5
2
2
2

5
2

1
2
2

2
35

29

20

2
36

6

31

13

124
11
22
23
16
15
22
15
7
4
5
7
5
4
5
3
3
2
170

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

STENELLA ATTENUATA

211

the ages corresponding to 2 or more ovulations are shown below.
µ = 0.07705

M = 0.07416

The catch of S. attenuata by means of the driving method is, on the coast of lzu
Peninsula, sporadic and small in number (Table 23). The catch of school no. 7 at
Taiji by the same method was the second case at least in recent several years.
Though the tuna seine is operated in the western North Pacific, as schools of tunaare usually found by the floating wood or flocks of birds in these waters, the catch

1 ~~~~~-'-'--'-'--'-'--'-L..l-1-1-L.L.L.Jl-LJ'--'-l_L..l__l....l...L.L..L.W
8~
IB
W ~ W ~ E~"

Age in years
Fig. 45. Age frequency of female S. attenuata calculated from the number of ovulations and estimated accumulation rate of corpora. Line was calculated by leastsquares excluding a point of the youngest animal.
TABLE 23.
Year
Drivingno. of school
no. of dolphin
Harpoon2>

NUMBERS OF S. ATTENUATA CAUGHT AT IZU AND KII PENINSULA.

1963

'64

'65

'66

'67

'68

'69

'70

'71

'72

'73 1>

1
37

l

470

0
0

2
322

2
373

0
0

437

7
2907
14

0
0
37

4
660
12

5+
1366+
17+

1963-1968: Tobayama (1969), 1l : Includes 206 animals in two schools caught at Taiji. 2l : Taiji.

of S. attenuata by tuna boats seems to be negligible (Ohsumi, 1972, Dr. Suda, personalcommunication). Catch by means of hand harpoon is operated off Taiji on the
coast of Kii peninsula. But the number caught is small.
Accordingly, the population of S. attenuata in the western North Pacific is considered to be close to virgin stock. In the stationary virgin stock, there must be an
equation shown below.
S·r- 1 ·f·l·e-µ't = S·(l-e-µ)where S is the number of sexually mature females, r length of reproductive cycle inyear, f ratio of females at birth, 1 the mean litter size, t the age at the attainment ofsexuall maturity, µ' the mean mortality coefficient before the attainment of sexual
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

212

KASUYA, MIYAZAKI AND DAWBIN

maturity, and µ the mean mortality coefficient of sexually mature females. Assuming t=8, r=50.3 months (=4.19 years), l=l.034, and f 0.3894, the following
values are obtained.
µ' = -0.14312, and M' = -0.13335, when µ = 0.3545µ' = 0.03240, and M' = 0.03188, when µ = 0.07705.

The values at the top are unreasonalbe, indicating that the mortality coefficient,µ=0.3545, obtained from the age frequency based on the dentine growth layer is toohigh. This is easily expected because the age of physically matured animal is often
underestimated by this method. Accordingly, one of the estimates of the meanmortality coefficient of immature females is 0.03240 when that of mature females
is 0.07705. The mean length of reproductive cycle 50.3 months used here is the best
estimate. Even when the less reasonable under- or over- estimates 43.8 months or
54.3 months are applied, the mean mortality coefficients of immature females are
0.04964 or 0.02264 respectively and still certainly lower than that of mature females.
Possibly the best estimate of the mean mortality coefficients of immature females
seems to be between the above two estimates or 0.023 and 0.049. This is about
half of the value for mature females.
The rough estimate of the morality of the male is calculated from the mortalityof female and the sex ratio at the age t. As m- µ=0.08348 was obtained in page
209, the mean mortality coefficient of the male at the age between 0 and 8 years is
m = 0.08348+0.03240 = 0.12588

and that at the age over 8 years is
m = 0.08348+0.07705 = 0.16053

The corresponding annual mortality rates are 0.118 and 0.148 respectivelty.
The present result shows that the mortality of immature animals is lower
than that of sexually matured animals. Brodie (1969) suggested that the long lactation of toothed whales will be effective as the period of education. This seems tobe true in S. attenuata. This species starts feeding on solid food at the age of about
3/4 years, but it continues to take both solid food and milk at least by the age of 1.5
years. This weaning period seems to work as the education or training period of thecalf, and work to lower the mortality of the young calf. The immature animals ofboth sexes aggregate after weaning, to have probable cooperative life. Of course
other than these special mode of life, the life of immature female free from thereproductive activity must keep the mortality lower than that of sexually mature
females.
The probability of survival in Fig. 46 and Table 24 is drawn based on thelowest mortality coefficients in the above and assuming 8 years as the age at theattainment of sexual maturity. It indicates that the number of females at attainment of the maturity is 83.4 % of that at the birth. The mean life expectancy of
newborn females is 14.6 years, and that of sexually mature females is 17.0 years.
The probable number of gestations experienced by a female is obtained by inSci. Rep. Whales Res. Inst.,
No. 26, 1974

STENELLA ATTENUATA

213

tegrating the relation between fertility rate of ova and number of ovulations (x) in
Table 16.

J~ (-0.01923x+0.6643)dx
The known highest number of ovulations, 18, suggests 8.3 gestations in the past.
The number of gestations, corresponding to the mean number of ovulations of adultfemales, 6.16, is 3.2.
The number of female calves (Rt) produced annually by the mature females(St) of the age t is shown by the following formula, assuming the start of conception
at the beginning of the year.
Rt = St ·r;;-1 • l ·f. P11.2112

to
0.8

()'
~ 0.6
:J
0-

~ 0.4
ll0.2

0

.... . . . . . . . . . . . . . .
0

8

4

12

16

20

24

28

32

36

40

Year after birthFig. 46. Calculated survival and reproduction in the female of S. attenuata.
dots at the bottom indicate the annual recruitment.

Small

TABLE 24.

LIFE TABLE OF FEMALES. ATTENUATA AT SELECTED AGES.

Year
after
birth

Probabilityofsurvival1 1

Total
ouvlation

Annualovulation
rate

0
4
8
12
16
17
20
24
28
32
36
40
44
48

1.00000.91340.83430.61300.45040.41700.33100.24320.17870.1313
0.09650.07090.05210.0383

0
0

0
0
0.432
0.437
0.443
0.445
0.449
0.455
0.461
0.467
0.473
0.480
0.486
0.492

2.7
4.5
4.9
6.3
8.1
9.9
11.8
13.7
15.6
17.5
19.5

Fertility
ratio ofovum

Ratio ofpregnant
femaleAnnualTotal
Reproductive cycle, reproduc- reproduc2
tion
tive rate >
year

0.645
0.612
0.578
0.570
0.543
0.509
0.474
0.437
0.401
0.364
0.3'32
0.290

0
0
0.253
0.243
0.232
0.230
0.222
0.211
0.201
0.189
0.178
0.167
0.156
0.145

0
0
0.10680.09840.09080.08930.08430.07870.07380.06920.0652
0.0616
0.05840.0553u lt=e-o.022Mt, 1 ;;;;t;;;;8. lt=0.834335e-o.onorn-sl, t;s8.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

2l RtfSt.

3.51
3.81
4.13
4.20
4.44
4.76
5.08
5.41
5.75
6.09
6.42
6.77

0
0
0.089
0.370
0.560
0.597
0.690
0.778
0.839
0.881
0.910
0.930
0.944
0.954

214

KASUYA, MIYAZAKI AND DAWBIN

where p is the annual survival rate, rt the length of reproductive cycle in year atage t, and 11.2/12 is the length of gestation in year. Other symbols are same withthe formula in page 211. rt is calculated from the relation between the number ofovulations and age (page 206), and that between length of reproductive cycle andnumber of ovulations (Table 16).
The annual recruitment thus calculated, and the total recruitment are shownin Fig. 46. Though the total recruitment must be 1 when the probability of survival
is 0, lt of the formula of survival, lt= 10e-µt, can be 0 only when t is infinite. In
Fig. 46 the probability of survival at the age 48 is 3.83 %, but the probability of total
recruitment is 95.40 %, and the recruitment seems to be slightly lower to keep the
population stable. But as this model is based on several assumptions, the above
defect is considered to be negligible at present.
If the population is depleted as the result of exploitation, the total reproductive rate ~Rt/~St will increase as the results of the increase of the ratio of young
mature female with high reproductive potential, and of the shortening of reproductive cycle of each age classes. The increase of the ratio of the female in the newborn
animals is also expected. This change of sex ratio works to increase the reproductive rate.

SCHOOLING BEHAVIOR

School size
The information of the number of dolphins constituting one school of S. attenuata
was obtained from the records of the catch by the driving method in the fishermen's
cooperative unions at Arari, Futo, Kawana, and Taiji. The records cover the years
from 1963 to 1973. As fishermen hope to catch all the animals they find, they may
sometimes drive to combine schools found at close distance. However, it is also
probable for them to lose a part of the school. However these problems are notdiscussed here, because the information at the time of driving is insufficient and thedefinition of a school is also unsatisfactory.
Table 25 shows the frequency of the size of the school. The smallest school
was composed of 37 animals, and the largest, 1,381 animals. The mean school size
is 281.0 animals. There are 4 modes observed in the frequency, or from 37 to 98,
from 120 to 437, from 509 to 617, and 1,381. The modal means are shown in thetable and they suggest that the basic unit of the school is less than 100 animals, andthat larger schools might be formed as the result of annexation of the smaller schools.
Immature animals
The age frequency of 7 shcools shows that the number of juvenile animals of
the age between 2 and 7 years is few (Figs. 44 and 4 7). It is lowest at the age of
3.5 years (male) or 4.5 years (female). Though we had no chance to confirm it, it
is suggested that the calves of the above age classes may have left the school of themother as in the case of S. coeruleoalba (Kasuya, 1972). The age when they leave theSci. Rep. Whales Res. Inst.,
No. 26, 1971:

215

STENELLA ATTENUATA

25
20
15
10
5
(/)

c

:c

6

.9-10
0
"'O 5

'5

5
.. o..,,,

d

z

4

5

3
2

5
0

1

2

3

5.5

105

15.5

205

Age in years
Fig. 47. Age frequency of S. attenuata by schools and sexes based on dentine growthlayers. Open circles and dotted lines indicate females, and closed circles andsolid lines males.

TABLE 25.

SCHOOL SIZE FREQUENCY OF S. ATTENUATACAUGHT BY DRIVING METHOD 0 •School size

No. of schools

Percent

1- 24
25- 4950- 7475- 99100- 124
125- 149
150- 199
200- 299
300- 399
400- 499
500- 599
600- 699
1300-1399
Total

0

0
4.8
9.5
4.8
4.8
4.8
23.8
19.0
9.5
4.8
4.8
4.8
4.8
100

2

I

5
4
2

l

21

Mean

)

65.5

)

235.9

}

563.0
1381. 0lJ 4 schools reported by Tobayama (1969) and Nishiwaki (1965)
included.

Sci. Rep. Whales Res. Inst.
No. 26, 1974

216

KASUYA, MIYAZAKI AND DAWBIN

mother's school is not directly known, but it may be soon after the weaning. It was
indicated from the length of lactation that calves of S. attenuata are weaned at theage between 17 and 60 months with an average of 29.3 months (2.44 years). As
the latter age is slighly before the age of lowest frequency, the above suppositionis supported. The age when the calf leaves the mother's school might be slightly
earlier in males than the female.
After the age of 3 or 4 years, the number of immature animals in the breeding
school increases. In females, the age of 4 years corresponds to the time when theweight of left ovary start to exceeds that of the right indicating the approach of the
puberty. And in males the age of 3 years is the time when the production of spermatozoa, an indication of the arrival of puberty, is started in many animals. Accodingly it is highly probable that the calves of both sexes which have left the mother's
school gradually return to the school of mature animals after reaching puberty,
and all the animals will return by the attainment of sexual maturity. However
some of the few calves which are accompanied by the lactating female for more than
4 years might attain puberty or sexual maturity in the same school.
The school of immature animals of S. coeruleoalba reported by Kasuya (1972)
was composed of the males between 1.50 years and 12.5 years of age (228 samples),and of the females between 2.75 years and 7.75 years of age (62 samples). The
modal age of that school was 4.5 years in males and 3.5 years in females. This feature strongly resembles the schooling behavior of juvenile animals of S. attenuata
presumed here.
The school of mature females usually contains puberal animals in it. The
only exception among 7 schools is school 5. In this school the animals of the age
corresponding to the puberal stage are only 2 animals. As the age determination
was made on only one third of the total number of the animals in the school, it is not
TABLE 26.

PRESENCE OF SPERMATOZOA IN TESTIS SMEAR.
Testis weight (g)School
no.

3

4

6

Spermatozoa

(
(
(

none
few
mediummanymean weight (g)nonefew
mediummanymean weight (g)nonefew
mediummanymean weight (g)

0-5.9
3

6-67.9
1
6

68~

5
3

4.8

10

2.2

23.4

281.9

8
7

2
9
17
195.6

17.3
17

18.1

7
6
2
158,6
Sci. Rep. Whales Res. Inst.,.No. 26, 1971

STENELLA ATTENUATA

217

conclusive at present as to whether there is a school of mature females which does
not contain puberal animals. However it is highly probable that the connection
between puberal animals and mature females is less strong and the former form
smaller groups when the school is dispersed or leave the latter school to join with aschool of immature animals.
If the sexual activity of the puberal males, or males from 6 g to 67.9 gin testis
weight, is shown by the density of spermatozoa in the testis smear, the activity is highin schools 2, 3 and 4 (Table 26). And a parallel relationship is observed between
the sexual activity of puberal males and that of mature males indicated by smears orby the mean weight of testes. However it was not conclusive as to whether it is related with the reproductive cycle of the male or with the schooling behavior.

Mature female
The age frequency of mature females in each school does not show the predominance of a particular age class, but seems to be evenly distributed and affected onlyby the mortality (Fig. 47).
As shown in Table 27, the breeding school of S. attenuata always contains bothpregnant females and lactating females. But the ratio of the latter to the former
varies widely between schools. The lowest ratio about 1.0 is found in the schools
I and 5, and the highest ratio 6.4 in the school 4. Most of the mature females inschool 4 were in lactating or resting stage. The abundance of resting females ismore variable from 0 in schools I and 5 to 3.5 times of the pregnant females in school

7.
The history of the reproductive activity of the females in each school is known
from the length frequency of the juvenile calves and of fetuses (Fig. 48). The simplest example is in school 6, where the mating peaks in the past are in March, January, and August (from left to right in Fig. 48). The intervals between the peaks
are 17 months and 12 months respectively. The feature of school 1 are very similar
to that of school 6, except for a small peak in October. The intervals between
the peaks in the school I are 16, 4.0, and 10.5 months.
School 2 shows complicated features. The peaks of conception are in February, late May, October, January, May, August, July, and October. The intervals
are 3.5, 4.0, 3.5, 4.0, 3.0, 11.0, and 3.0 months. Possibly the schools 4 and 5 belong
to a similar pattern with the approximate interval of the peaks of 4.0, 4.5, 4.0, and
9.0 months for school 4, and 4.5, 3.5, and 11.0 months for school 5. School 7 has
no small fetus, but the arrangement of mating peaks in schools 3 and 7 is notlargely different from that of school 2.
It is already suggested that S. attenuata in the Japanese coastal waters has 3mating seasons. If all the mature females stay in the same school for their life time,
there should be observed the peaks of 3 mating seasons in one school because thelength of reproductive cycle is highly variable between animals and it is difficult
for all the females to conceive synchronously in only one of the 3 mating seasons.
No such case was observed in any of 8 schools studied by us or by Nishiwaki et al,(1965). This strongly suggests that the member of mature females in any shcool is
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

KASUYA, MIYAZAKI AND DAWBIN

218

IV

VII

X

SJ,

z
3
4

=
n

Q--,
6

0

VII

X

IV

VII

X

I

IV

Vll

X

IV

x

VII

Month
Fig. 48. Frequency of date of conception (scale at the top) and of parturition(scale at the bottom). Dotted areas indicate the frequency obtained from the bodylength of postnatal animals, white from that of fetuses, and dotted lines cited from
Nishiwaki et al (1965). Numbers indicate the school.

TABLE 27.

RATIO OF REPRODUCTIVE CONDITIONS OF FEMALE S. ATTENUATA.
MatureDatekilledImmature* *25, Oct.
2
3SchoolTotal***

unknown

pregnant

p. & I.

lac tating

resting

total*

24
33.3%

12

15
41. 7

3
8.3

18
50.0

0
0

36
100

72

15, Nov.

67
42.7%

4

19
22.1

2
2.3

47
54.7

18
20.9

86
100

157

4, Nov.

5
20.0%

0

4
20.0

0
0

15
75.0

20
100

25

5.0

4

13, Nov.

15
26.3%

3

3
7.7

1
2.6

28
71.8

7
17.9

39
100

57

5

18, Nov.

5
33.3%

2

4
50.0

0
0

4
50.0

0
0

8
100

15

6

12, Feb.

13
18.8

8

14
29.2

0
0

21
43.8

13
27.1

48
100.1

69

7

2; Jui.

3
16.7%

2

2
15.4

0
0

4
30.8

7
53.8

13
100

18

132
32.0%

31

61
24.4

6
2.4

137
54.8

46
18.4

250
100

413

Total

* : Excluding the unknown.
* * : Percentage of total.

%***: Excluding the maturity unknown.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

219

STENELLA ATTENUATA

not fixed but some of them can be exchanged between schools.
The interval between two recent mating peaks is usually long, but the intervals
obtained from length frequencies of postnatal individual is often appears short.
This seems to indicate that the oestrous females assemble together to conceive as suggested in S. coeruleoalba (Kasuya, 1972), and this connection is retained during theperiod of gestation. However after parturition the connection becomes weakerwith the elapse of the time, and some of the lactating females may move to anotherschool accompanying the calf in some case. Possibly the shift of the lactating females between schools is related to the cycle of postpartum or postlactum ovulations.
The schooling behavior of resting females is probably similar to the late lactating
females, but the ratio of the between school movement will be much higher.
The frequency of interval between the two mating peaks in the present 7 schools
has 4 modes with the modal means of 3.8 month (13 examples), 8.1 months (4),11.2 months (4), and 16.5 months (2). These modal means are a multiple of 4months which is the interval of mating season of this species. If the combination of
the peaks of conception observed in the present schools are formed through therandom combination of each peaks, the frequency of each mode are expected tolie on the straight line shown in Fig. 49. However, the above data shows a higher
frequency of the 4 months interval. This means that the neighbouring two matingpeaks are not completely independent. Probably the females which failed to conceive in a mating season may often stay in the same school to conceive in the next
mating season. This case is represented by a smaller peak next to the main peak
TABLE 28.

MATURITY FREQUENCIES AND SEX RATIO OF MALE S. ATTENUATA.
Testis weight in g

Schoolno.

Datekilled25, Oct.
2

15, Nov.

34, Nov.

4

13, Nov.

518, Nov.

6

12, Feb.

7
Total

2, Jui.

unknown

Total

Sex ratioof themature

imm.*

mat.*

5.9;?;

6.067.9

16
34.0%
49
48.5%
1
4.3%
11
19.0%
8
100 %
2
4.0o/o
7
41.2%
94
30.9%

21
44. 7

0
0
4
4.0

2
4.3
20
19.8

8
17.0

3

50

0.605

11

7

108

0.311

0

23

0.450

58

0.762

0

8

0

12
24.0

30
51. 7
0
0
15
30.0

0

0

50

0.286

2.0
0
0
41
13.5

0

17

0.067

5.9
21
6.9

9
39.1
15
25.9
0
0
20
40.0
8
47.1
74
24.3

9
39.1

0
0

4
17 .4
0
0
0
0

10

314

0.409

17
16.8
0
0
2
3.4

* : Maturity of testis was identified by eye on the beach.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

68;£

10.9

5.9
74
24.3

220

KASUYA, MIYAZAKI AND DAWBIN

(;' 8

c

<II

:I 6
O'"

\

<II
....
l.L 4

'o----- -----0....

6

8

10

12

14

16

Interval in months
Fig. 49. Frequency of the interval of mating peaks in the 7 schools. Open circles
and dotted line indicate the total frequency in each mode plotted against themodal mean of the interval. Straight solid line shows the frequency expected whenmating peaks are independent.

Sum

50
40
30
20
lll

c

10

:ca.

:g 10

6

13 5
6

"""'--'""""--''"-~~~miZ'--~~~~~-"''--~~~--1

z
4

10

5
3

5
5
2

4
8
Diameter in mm

10

Fig. 50. Diameter of the largest Graafian follicle. White spots indicate pregnant
females, black spots the lactating, and lines the resting. Schools are shown by
the number at right.

observed in schools 2 and I. In some cases, oestrous females from other schools
exceeding in number the oestrous females in the original school, may join to thisschool. This is suggested by the 6th peak (from the left) of school 2, where thepreceeding 5th peak is smaller. Of course there can be the case where all females
which should have constituted the subsidiary peak shift to another school as sugSci. Rep. Whales Res. Inst.,
No. 26, 1974

STENELLA ATTENUATA

221

gested by the long intervals of peaks.
The origin of other peaks of short interval or of peaks of long interval might be
the result of the annexation of schools or random exchange of members between two
or more schools. The relative abundance of the 8, 12, and 16 months interval ofpeaks of conception decreases at the rate expected in random combination.

A1ature males
As the diameter of seminiferous tubules and the weight of testis show a linear
relationship, the weight of testis of mature male can be used as an indicator of re-

'E

£7
"'
~
~ 5

0
~

a;

6

3

~

E

Cl

15

200

300

400

500

600

700

Weight of testis (g)Fig. 51. Relation between the mean weight of testis of mature animal and mean
diameter of Graafian follicle of the female in a same school. Large closed circle
indicates the follicle diameter of resting female, open circle that oflactating female,and small closed circle that of pregnant female. Schools are shown by the numbers .

.

a~-~-~4-~-~-~-~-~~,,.....

,
.6

o·6
~

0
:;::;

e

0

,(\3

'- .4

.4

x

><
Cl>
VJ

2
6

Q)

lf)

.2

.2
----.'~
0'---~--'----'---~-~-~-~~

0

1

2

3

4

5

6

Diameter of follicle in mm
Fig. 52. Relation between the mean diameter of Graafian follicles of restingfemales and the sex ratio of matureindividuals in the same school. Schools
are shown by the number. The dottedline indicates the highest and lowest
range.

0 '--2~00-'~30~0_...~40~0__,_~50~0--L.-6~0-o~-7~0~0~

Weight of testis(g)Fig. 53. Relation between sex ratio of
mature animals and mean weight oftestis of mature males in the corresponding school. Schools are shown by
the number.

productive activity. The mean weight of testis of mature male was compared withthe mean diameter of the largest follicle of the mature females caught in the same
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

222

KASUYA, MIYAZAKI AND DAWEIN

school (Fig. 51 ). The mean weight of testis shows a positive correlation with thediameter of the follicle of resting females. As resting females with large follicles
are ready to ovulate, it is reasonable to expect males of high activity in the sameschool.
The sex ratio of mature individuals is small in schools containing resting femaleswith large follicles (Fig. 52). A similar but clearer tendency is observed when it
is compared with the mean weight of testis of mature males (Fig. 53). Though it
is not shown in Figs. 51, 52 and 53, school 5, which does not contain resting females nor lactating females with follicles larger than 1.0 mm in diameter and is considered to be in low mating activity, it has no sexually mature male.
These results suggest that in schools at the beginning of the approach of heat
many mature males may assemble in the same school, but at the peak of the heatmost of them except a few males of high activity leave the school. It is highly possible that there is intrasexual aggression between the males of S. attenuata as in thecase of another delphinidae species Globicephala melaena suggested by Sergeant ( 1962).

Fig. 54. Schematic figure showing one of the possible between school exchange ofmature females. Arrows indicate the annexation or the split of the school. White
spots indicate pregnant females, black spots the lactating, lines the resting. Mating
seasons in each 4 months inteval are shown by vertical rods.

Discussion
It is well reported in several species of delphinidae that their school is compact
in some cases, but in other cases it is composed of many smaller schools dispersed ina wide area. Sergeant (1962) and Saayman and Tayler (1973) suggested that it
will be related to feeding or sexual behavior of the animal. Our observation on alarge school of S. coeruleoalba, found in the evening of 24, Oct. 1972 at 34°52' N,
141°05' E, showed that it covered a wide area of about 21 km in one diameter andcomposed of numerous small groups of dolphins. This smaller groups had a distanceof about 3 km to 15 km from each other, and were composed of 10 to 200 individuals.
Some of them contained calves accompanied by the mother and several were composed mostly of smaller animals. This suggests that the larger schools of S. coeruleoalba contains smaller units.
It is probable that several small units leave the main larger school after whicha larger dispersed school again forms a compact school, or that the smaller units
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

STE.NELLA ATTE.NUATA

223

move to an other school when the two groups come to a close distance. Fig. 54
was drawn on the assumption that the exchange or shift of the members between
schools can occur through the procedure mentioned in the above. In this figure,though the composition of the reproductive condition at both ends of the diagram
is similar, the members are largely different. The immature animals are not shown
because their behavior is simple, the mature male was also excluded as its behavior
is not well understood.
ACKNOWLEDGMENTS

The collection of data and samples were made through the cooperation of thefishermen's cooperative unions at Kawana, Futo, and Taiji. We had the help of
Dr. T. Kajihara of the Ocean Research Institute and of Mr.]. H. Perano in collecting smaples. Dr. W. F. Perrin of the National Marine Fisheries Service kindly readthe draft. Dr. K. Tatsukawa of the Ocean Research Institute, and Dr. A. Ohsumi
and Dr. A. Suda of the Far Seas Fisheries Research Laboratory gave us valuablesuggestions. This study was technically assisted by Miss. S. Wada and Miss. K.
Nagayama and Mr. K. Kureha. These persons are deeply acknowledged.
REFERENCESAsDEL, S. L., 1964. Patterns of mammalian reproduction (2nd ed.), 670 pp. Constable & Co., London.
BEST, P. B., 1969. The sperm whale (Pftvseter catodon) off the west coast of South Africa 3. Reproductionin the male. Invest[. Rep. Div. Sea Fish. S. Afr., 72: 1-20.
BRODIE, P. F., 1969. Duration of lactation in cetacea: an indicator of required learning? Amer. Midland.Naturalist, 82(1): 312-314.
CALDWELL, D. K. and M. C. CALDWELL, 1966. Observation on the distribution, coloration, behavior andaudible sound production of the spotted dolphin, Stenella plagiodon (Cope). Contribution in Science, 104:
1-28, Los Angeles County Museum.
DAWBIN, W. H., 1966. Porpoise and porpoise hunting in Malaita. Australian .Natural History, 15(7):207-211.
EVANS, W. E. and J. BASTION, 1969. Marine mammal communication: social and ecological factors. The
Biology of Marine Mammals (ed. Andersen, H. T.), p. 425-475. Academic Press, New York and London.
FRASER, J. F. D. and A. ST. HUGGETT, 1973. Specific foetal growth rates of cetaceans. J. :(,ool., Landon.
169: 111-126.
GRAY, J. E., 1846. Zoology of the voyage qf H.M.S. Erebus and Terror, I (Mammalia): 44, pl. 28.
HARRISON, R.J. and S. H. RIDGWAY, 197 I. Gonadal activity in some bottlenose dolphins (Tursiops truncatus).
J. :(,ool., Land. 165: 355-366.
HIROSE, K. and M. NISHIWAKI, 1971. Biological study on the testis of the Blue white dolphin, Stenella
caeruleoalba. ]. Mam. Soc. Jap., 5(3) :91-98.
KAsUYA, T., 197 I. Consideration of distribution and migration of toothed whales off the Pacific coast ofJapan based upon aerial sighting record. Sci. Rep. Whales Res. Inst., 23: 37-60.
KASUYA T., 1972. Growth and reproduction of Stenella caeruleoalba based on the age determination bymeans of dentinal growth layers. Sci. Rep. Whales Res. Inst., 24: 57-79.
LAws, R. M., 1959. The foetal growth of whales with special reference to the fin whale Balaenoptera physalus
L. Discovery Rep., 29: 281-308.
MIYAZAKI, N., T. KAsUYA, AND M. NrnmwAKI, 1974. Distribution and migration of two kinds of Stenellain the Pacific coast of Japan. Sci. Rep. Whales Res. Inst. 26: 227-243.
Sci. Rep. Whales Res. Inst.,.No. 26, 1974

224

KASUYA, MIYAZAKI AND DAWBIN

MizuE, K. and K. YOSHIDA, 1962. Studies on the little toothed whales in the west sea area ofKyusyu-lX,
about Prodelphinus sp., so called "madara iruka" in Japan caught at Arikawa in G:lto Is., Nagasaki
Pref. Bull. Faculty of Fish. Nagasaki Univ., 13: 1-8.
NAKAJIMA, M., K. TAKAHASHI, M. 0GURA, AND K. SAWAURA, 1963. On the growth of infants of the small
size toothed whales. ]. Jap. Ass. :(,ool. Gardens and Aquarium, 5(1): 16-22. (in Japanese).
NISHIWAKI, M., M. NAKAJIMA AND T. KAMIYA, 1965. A rare species of dolphin (Stene/la attenuata) from
Arari, Japan. Sci. Rep. Whales Res. Inst., 19: 53-64.
0HsUMI, S., 1964. Comparison of maturity and accumulation rate of corpora albicantia between the left
and right ovaries in cetacea. Sci. Rep. Whales Res. Inst., 18: 123-148.
0HsuMI, 1972. Catch of marine mammals, mainly of small cetaceans, by local fisheries along the coast ofJapan. But. Far Seas Fish. Res. Lab. (Shimizu, Jap.), 7: 137-166.
PERRIN, W. F., 1969. Color pattern of the eastern Pacific spotted porpoise Stene/la graffmani (Cetacea, Delphinidae). :(,oologica, 54(4): 135-151.
PERRIN, W. F., 1973. Variation and taxonomy of spotted and spinner porpoises (genus Stenella) of the eastern
tropical Pacific and Hawaii. Dissertation Abstracts International, 33(10).
PERRIN, W. F. AND E. L. ROBERTS, 1972. Organ weights of non-captive porpoise (Stenella spp.) Bull. Southern
Calif. Acad. Sci., 71 (1): 19-32.
SAAYMAN, G. S. AND C. K. TAYLER, 1973. Social organization of inshore dolphins (Tursiops aduncus andSousa) in the Indian Ocean. ]. Mamm., 54(4): 993-996.
SERGEANT, D. E., 1962. The biology of the pilot or pothead whale Gtobicephala melaena (Trail) in Newfoundland waters. Bull. Fish. Res. Board of Canada, 132: 1-84.
SERGEANT, D. E., D. K. CALDWELL, AND M. C. CALDWELL, 1973. Age growth, and maturity of bottlenosed dolphin (Tursiops truncatus) from northeast Florida. ]. Fish. Res. Board Qf Canada, 30(7): 1009-1011.
TAVOLGA, M. C. AND F. S. EssAPIAN, 1957. The behavior of the bottlenosed dolphin (Tursiops truncatus):
mating, pregnancy, parturition, and mother-infant behavior. :(,oologica, 42(1): 11-31.
TosAYAMA, T., 1969. School size and its fluctuation in the catch of Stenella coeruleoalba in Sagami Bay.
Geiken Tsushin, 217: 109-119. (in Japanese).
YABLOKOV, A. V., 1963. On the type of color of cetacea. Bull. Moscow Sci. Experimentation in Nature, Biol.
Sec., 68(6): 27-41, (in Russian with English summary).

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

STENELLA ATTENUATA

EXPLANATION OF PLATESPLATE I
Fig. I. S. attenuata, female, 118 cm in body length. Pigmentation of newborn stage.
Fig. 2. S. attenuata, female, 178 cm in body length. Dark spots have started toappear only on the !ewer jaw, and the white area on the tip of jaws is also started.
The both characters are classified into stage I.
Fig. 3. S. attenuata, data unknown. The white tips of jaws are classified into stage
2, and the dark and white spots into stage 3.
Fig. 4. S. attenuata, male, 209 cm in body length, same animal with Fig. 4 in Plate
II. The white tip of jaws are classified into stage 2, white dorsal spots into stage 2,
and dark ventral spots into stage 3.
Fig. 5. S. attenuata, adult male. The white tip of upper jaw is classified into stage 3,that of lower jaw into stage 2, white dorsal spots into stage 2, and ventral dark
spots into stage 3.
Fig. 6. S. attenuata, dorsal view of left flipper of juvenile animal, showing the dark
spots on the surface.
PLATE II
Fig. I. S. attenuata, female, 117 cm in body length. Showing the pigmentation of
newborn animal. An animal in the other side is also newborn calf.
Fig. 2. S. attenuata, female, 189 cm in body length (center). The conditions of two
kinds of spots are classified into stage 3, and the white areas at the tip of jaws
into stage 1. An animal at this side is a juvenile male.
Fig. 3. S. attenuata, male, 181 cm in body length. Ventral white spots are classified
into stage 3, and other characters into stage I.
Fig. 4. S. attenuata, male, 209 cm in body length, ventral view. Same animal with
Fig. 4 in Plate I.
Fig. 5. S. attenuata, ventral wiew of an adult male.
PLATE III
Fig. I (top). Underwater photograph of a group of adult or subadult S. attenuata inthe school 5 enclosed in the harbor, showing the conspicuous white tip of beak.
(Photographed by N. Miyazaki)
Fig. 2(bottom). Mother and suckling calf in the same school, showing the differenceof the pigmentaticn of ventral region. (Photographed by N. Miyazaki)
PLATE IV
Tooth section of S. attenuata. photographed under transmitted light.
Fig. I. 104 cm, male, killed on 12th, Feb. A thin translucent layer is accumulated.
Less than 1/4 year.
Fig. 2. 112 cm, male, killed on 18th, Nov. A thick opaque layer is accumulated.
About 1/4 year old.
Fig. 3. 135 cm, male, killed on 12th, Feb. A thin opaque layer and a thick tramlucent layer of full thickness are accumulated. About 3/4 year old.
Fig. 4. 175 cm, female, killed on 13th, Nov. A thin opaque layer and 2 opaquelayers of full thickness are accumulated. About 2 1/4 years old.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

225

226

KASUYA, MIYAZAKI AND DAWEIN
PLATE V
Fig. !. 166 cm, male, killed on 2nd July. 3 opaque layers are accumulated. The
both first and last layers are thin translucent layer. About 2 3/4 years old.
Fig. 2. 177 cm, female, immature, killed on 2nd, July. 6 opaque layers are accumulated. The first and the last layers are the thick opaque layer. About
5.5 years old.
Fig. 3. 205 cm, female, two corpora in the ovaries, killed on 2nd, July. 11 opaquelayers are accumulated and the pulp cavity is still wide. About 10.5 years old.
Fig. 4. 195 cm, female, 11 corpora in the ovaries, killed on 13th Nov. 24 opaquelayers are observed, and pulp cavity is filled with secondary dentine. Real age
will be more than the number of the opaque layers.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

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DISTRIBUTION AND MIGRATION OF TWO SPECIESOF STENELLA IN THE PACIFIC COAST
OF JAPANNOBUYUKI MIYAZAKITOSHYO KASUYAAND
MASAHARU NISHIWAKI
Ocean Research Institute, University of Tokyo, Tokyo

ABSTRACTDistribution and migration of Stenella coeruleoalba and Stenella attenuata in
the Pacific coast of Ja pan were studied basing on the fishing data and the sighting data, and the relationship between them and the marine environment
was discussed. S. coeruleoalba and S. attenuata are distributed in the pelagic andcoastal waters influenced by the warm Kuroshio current. S. attenuata is
distributed in slightly warmer waters than S. coeruleoalba is. Their range ofdistribution seems to extend up to 46°N in summer season and retreats to
33°N in winter. The concentration of these species in the northern boundaryof the Kuroshio current is suggested.
INTRODUCTION
At least three species of Stenella are known from Japanese coastal waters. They
are the spinner dolphin S. cf. longirostris (Mizue et al., 1964), the spotted dolphin(Mizue et al., 1962, Nishiwaki et al., 1965) and the blue white dolphin (Okada,
1936, Ogawa, 1936). The first is rare and only known from the southern partof Japan, and the color pattern of these are very similiar to S. cf. longirostris described by Perrin (1972) from Hawaiian waters. The other two species are fairly
common and have been the object of the commercial hunting at several places on
the Pacific coast of Japan. These two species are caught at Taiji (33° 36' N,
135° 56' E) on the coast of Kii Peninsula, at Arari (34° 48' N, 138° 46' E) on thewest coast oflzu Peninsula, and at Kawana (34° 57' N, 139° 08' E) and Futo (34°
52' N, 139° 06' E) on the east coast of Izu Peninsula. The fishermen at Taiji huntthe dolphin with hand harpoon, or with hand harpoon and shot gun off the coastof Kii Peninsula, but they have introduced the driving method since 1973. The
people at Arari had captured the various species of dolphins in Suruga Bay withdriving method, but the operation has almost ceased since 1962. The two villages
on the east coast of Izu Peninsula operate the dolphin hunting with driving methodin Sagami Bay and the waters around Oshima Island (Tobayama, 1969, Kasuya,1972). Details of dolphin fishing is described by Ohsumi (1972).
Sci. Rep. Whales Res. Inst.,
No. 26, 1974, 227-243

228

MIYAZAKI, KASUY A AND NISHIWAKI

Tobayama (1969) analyzed the catch statistics of the two fishermen's cooperative unions at Kawana and Fu to, and suggested the influence of the marine topography in the formation of the fishing ground. Howeven, Kasuya (1972) suggested another factor the inflow of warm water into Sagami Bay. Ohsumi (1972)
analyzed the official statistics of dolphin fishing prepared by the Ministry of Agriculture and Forestry, and showed an estimated migration route of blue white dolphin.
This study intends to analyze the distribution and migration of Stenella coeruleoalba and of Stenella attenuata. This analysis is based on the catch records of thefishermen's cooperative unions and sighting records of these species collected by us
or reported by various authors.
10'

20·

30'

40'

50'

140 °

Sagmi Bay1 1
( 8 )( 9)31(8) ( 4)I z u °KawanaPen.
2 1 3 2(3) (3) (11 )(13)
14 5 2(22)(12) (9)3 3 10 2(R10)(31x1s)
11

50'

4

. (62)(32)
Oshima
2

~

(47)

40'
Fig. I. The number of schools of Stenella spp. sighted by the scouting boats in 3.3'
(6.1 km) squares during 8 seasons from 1964-'65 to 1973-'74. Numerals inparenthesis indicate the number of schools per 10 7 nautical miles of scouting.
(For Sagmi Bay read Sagami Bay)

MATERIALS

The statistics were collected by Miyazaki from four fishermen's cooperative unions.
The data collected at Taiji covers ten years from 1963 to 1972. Some of thestatistics were provided by Dr. Kajihara. The distinction of the two species of Stenella
is made only in recent three years. In this district " Mairuka" and " Haukasu "indicate S. coeruleoalba and S. attenuata respectively. All of that catch were madewith hand harpoon, or hand harpoon and shot gun.
The data collected at Arari covers the catch of fourteen seasons from 1950 to1970, but there are only sporadic catches after 1962. S. coeruleoalba and S. attenuata
are recorded by the name "Mairuka" and" Hasunaga or Arari-iruka" respectively.
The various informations on the dolphin fishing in Sagami Bay were colSci. Rep. Whales Res. Inst.,

No. 26, 1974

DISTRIBUTION AND MIGRATION OF STENELLA

229

lected from the fishermen's cooperative unions at Kawana and Futo. They comprise the number of dolphins and schools, position of sighting, and the hours and thenumber of scouting boats engaged. The number of dolphins is known for thetwenty seasons from 1949-'50 season to 1973-'74 season. But the statistics are fragmental before the 1961-'62 season, and do not give the total number of dolphinsof the genus Stenella caught in Sagami Bay. The two species of Stenella are recorded separately since 1969-'70 season. The main fishing area in Sagami Bay isshown in Fig. 1. The total scouting hours of the four high speed, 20 knot at maximum, scouting boats were available for eight seasons from 1964-'65 to 1973-'74
season. This was used as the indicator of the fishing effort. These scouting boats
leave the harbor, if the weather is good, at 5 o'clock in the morning. And if theyfind a suitable school, they drive it into the harbor with the help of other slower boats.
They usually find the school before the noon, but they sometimes continue the scouting until 3 o'clock in the afternoon. The fishing season in Sagami Bay starts inthe autumn season (October) and ends in the winter of the next year (January).
The sighting records of Stenella coeruleoalba and Stenella attenuata were obtainedby Kasuya and Miyazaki through five cruises of the research vessel the Tanseimaru.
They are used together with the many sighting records and sporadic catches of these
species reported by various authors (Tables 1, 2).
Oceanographical data obtained through two cruises of the Tanseimaru in 1971
and 1972, and that reported by Japanese Meteorological Agency, Japanese Maritime
Safety Agency, Tokyo Metropolitan Fisheries Experiment Station, and Shizuoka Prefectural Fisheries Experiment Station were used in analyzing the relation between
the distribution of the dolphins and the environment.

ANALYSIS OF THE STATISTICS

Annual .fluctuation of catch
Fig. 2 shows the annual fluctuation of the catch of Stenella spp. in each fishingarea.
Though the statistics are imperfect before 1961-'62 season, it is suggested thatthe number of the dolphins caught in Sagami Bay shows rapid increase after thatseason. This seems to be related with the introduction of the high speed scouting
boats. After this year the amount of the catch increases to record the maximum
catch of 15,649 dolphins in 1965-'66 season. As the two fishermen's unions started
the cooperative operation in 1967-'68 season to control the market price, the numberof dolphins caught decreased to about one third of the maximum catch. But thechange of the mode of operation cannot explain all the annual fluctuation of thecatch. Because the number of dolphins caught per one scouting hour shows thefluctuation parallel with that of total number of catch (Fig. 3). It is suggested thatthe annual fluctuation of the catch will indicate that of the abundance of thedolphins migrating into the fishing ground. Fig. 4 shows the relation betwem theannual catch of Stenella spp. in Sagami Bay and the distance from Oshima Island to
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

MIYAZAKI, KASUYA AND NISHIWAKI

230
4-

4

x10

x10

2

.c
u

0

0

u

1

'50
• Kawanoo Fut oe Ka wan a......
0. 50-51'60-61
SeasonFig. 2. The number of catch of Stenella coeruleoalba (left scale) and of Stenella attenuata(right scale) at each fishing ground. Solid line indicate S. coeruleoalba, and broken
line S. attenuata.

x 103
15

.c 1 0

u.i
::i

u

5

0

u

a.:
u

5

'
0

0
'61·'62'69•70'65-'66'73'74

SeasonFig. 3. The number of catch and the catch per one scouting hour (C. P. U. E.)
of Stene/la spp. in Sagami Bay. Closed circle and solid line indicate the catch, andopen circle and broken line catch per one scouting hour.
Sci. Rep. Whales Res. Inst.,

No. 26, 1974

DISTRIBUTION AND MIGRATION OF STENELLA

231

the nearest border of the Kuroshio current from October to December Qapanese
Maritime Safety Agency, 1961-'71). As the surface water temperature is highlyvariable by the effect of the meteorology or of the tide, the position of the l5°C
isothermal at the depth of 200 m was used as the indicator of the position of theKuroshio current. It is clear in Fig. 4 that the catch of Stenella spp. in Sagami Bay
has the negative correlation with the distance of the Kuroshio current from themain fishing area. This means that in the years when the Kuroshio current situatesclose to Sagami Bay, there migrates many dolphins of the genus Stenella. The catchor catch per unit effort changes affected by the abundance of the migrating dolphins.
Though the two species of Stenella are recorded separately in the statistics only inthe seasons from 1969-'70 to 1973-'74 season, as the catch of S. attenuata comprises
4,956 individuals or 16. l % of the total catch of Stenella spp. in Sagami Bay in theseseason, it is reasonable to expect the catch of S. attenuata even in the preceding years.
3

x 10
15

0

'65
0

'66

0

10

'61

..c

•

0

•
'70'67

u

0

'63

'62

Cl

0

u

5

'64

•

. 68

•

•

'69

'71

0
0

20

40

60

80

Distance(mile)
Fig. 4. Relationship between the number of catch of Stenella spp. in Sagami Bay,and the distance (nautical mile, 1.85 km) from Oshima Island to the 15°0 isothermal line at the depth of 200 m. Closed circle indicates cooperative operationand open circle competitional operation. The numerals indicate the starting
year of the season.

The catch of Stenella spp. in Suruga Bay was high until the early 1950's(see Arari in Fig. 2). But they had almost finished the operation since 1962. Thisage coincides with the time when the catch in Sagami Bay increased rapidly.
The other shorter cycle of annual fluctuation of the catch is expected to be affectedby the oceanographical conditions as in the case of Sagami Bay. Though Nishiwaki et al. ( 1965) reported the information from the fishermen's telling that the catchof S. attenuata in 1959 or in 1964 was the first case for them to catch this species. It is
Sci. Rep. Whales Res. Inst.,

No. 26, 1974

232

MIYAZAKI, KASUYA AND NISHIWAKI

difficult to trust their telling at the following two aspects. At first, after that year
the capture of several schools of S. attenuata within short period were reported fromthe village (Nishiwaki et al., 1965), and secondly the catch of S. coeruleoalba and S.
attenuata in the village seems to have been recorded by the different vernacular names
mentioned before.
The catch statistics off Kii Peninsula shown in Fig. 2 do not include the catchby driving method as it was started in 1973. The general trend of the catch of
Stenella is gradually increasing in recent years. The statistics of two kinds ofStenella were recorded separately only in the recent three seasons. As the result of
the difference of the price between two species in this local district, the fishermen
prefer S. coeruleoalba. So, the catch of S. attenuata in the recent three years was only
63 animals or 1.8 % of the total number of the catch of the two species. This ratio
is lower than that of the catch in Sagami Bay.

Seasonal fluctuation of catch
In Sagami Bay the fishing season starts in late September, and ended in theformer years in January or in early February but in recent years it ends in late
December (Figs. 5 and 6). Fig. 6 shows the difference of the fishing season of the
x10

3

x10

10

2

w

u

2
=i x10

5

5

1 0:

u

u

0

\

w

\...
0
Oct.

Nov.

Dec.
Season

Jan.

0

Feb.

Fig. 5. The seasonal changes of the catch of Stenella spp., of the catch per one
scouting hour (C.P.U.E.), and of the scouting hours (effort) in Sagami Bay.
8 seasons from 1964-'65 to 1973-'74 season are combined. Closed circle andsolid line indicate C.P.U.E., closed circle and chain line the total amount ofeffort, and open circle and broken line the catch.

two species. Though the season of S. attenuata seems to start almost at the same
season with that of S. coeruleoalba, the peak of the catch comes in early November andthe season ends by late November. On the other hand the peak of the catch of
Sci. Rep. Whales Res. Inst.,

No. 26, 1974

233

DISTRIBUTION AND MIGRATION OF STENELLA

S. coeruleoalba is in late November about one month later than that of S. attenuata.
The decrease of the catch of S. coeruleoalba in late October and early November
will be the effect of the catch of S. attenuata.
x 10

3

x1Q3

10

3

2
5

0
x10 2

0
3
x 1
10

o

2
0

.>::.

.>::.

u

u

5
0

0

0

u

u
0
x10

0
2
x 10
10

2
5

\

\
\

0------0.. ...

0

J

F

/'' ....

-M

/ /

/

' .,,_\\\,.......

0

A

M

A
J
J
Se a son

s

0

N

D

J

Fig. 6. The seasonal fluctuations of the catch of Stenella coeruleoalba and Stenella
attenuata at each fishing ground. Closed circle, solid line and left scale indicate S.
coeruleoalba, and open circle, broken line and right scale S. attenuata. Top:
Sagami Bay, Middle: Suruga Bay, B::ittom: Off Kii Peninsula.

The seasonal fluctuation of the catch per scouting one hour in Sagami Bay isshown in Fig. 5. The fluctuation shows three peaks, the first in early October,second in late November, and the third in late December or in early January. At
the beginning of the season, they often start the catch after obtaining the informationof sighting by other fishing vessels. And in the late December and early January
the scouting effort decreases, because the fishermen spend the time for the new year
festival or for its preparation. These two factors affect the catch per one scouting
hour and keep it high. Accordingly, the first and the last peaks are supposed not
to reflect the real abundance of the dolphins. The real peak of the migration of
S. coeruleoalba in Sagami Bay is considered to be in the late November, and that
Sci. Rep. Whales Res. Inst.,
No. 26, 1971:

234

MIYAZAKI, KASUYA AND NISHIWAKIof S. attenuata is in late October.
In Suruga Bay the catch of Stenella spp. was made in any season of the year, but
the peaks of S. coeruleoalba caught are in the seasons from April to July and from
December to January. The former peak is not observed in Sagami Bay, and thelatter is about one month later than the corresponding peak in Sagami Bay. The
spring peak of S. attenuata in Suruga Bay seems to arrive later than that of S.
coeruleoalba.
Fig. 6 shows the seasonal fluctuation of catch of two species of Stenella off Kii
Penisula. Though the catch of Stenella spp. in this area is made in any season of
the year, the peak of S. coeruleoalba are in the seasons from April to July and from
October to March. The former will correspond to that of Suruga Bay, and the latterto the winter fishing seasons in other grounds. The winter peak of S. coeruleoalba
arrives slightly later in the southern area than the northern. Similar feature isobserved also in S. attenuata. The catch representing the spring peak of S. attenuata
is too small to discuss the difference of the season. The fishermen say that thefishing ground in March becomes too far from the coast to operate the dolphin
fishing. This will be one of the reason of the smaller catch in spring season.
GEOGRAPHICAL DISTRIBUTION

All the available records of sighting or of sporadic catch of S. coeruleoalba and S.
attenuata in the Pacific coast of Japan are plotted in Fig. 7. The origin of these records are shown in Tables 1 and 2. The l 7°C isothermal line shows the surface water
TABLE 1.
No.

LIST OF RECORDS OF SPORADIC CATCH OF STENELLA SPP. IN
THE WESTERN NORTH PACIFIC.
Position

Date

AuthorComments

Ogawa, 1936

Purchased at the market

Okada, 1936

Purchased at the market

Okada, 1936

Possibly caught on Izu coast

Okada, 1936
Okada, 1936
Higashikawa
et al., 1966

Purchased at the market
Possibly caught on Izu coast

Ogawa, 1936

Purchased at the market

S. coeruleoalba

IX

'34

2
3

21

4
5

27
4

II
II

'35

6

26

I

'64

'35

Off Choshi(35°44'N, 140°52'E)
Off Onahama(36°53'N, 140°52'E)
Shimizu fish market(35°00'N, 130°30'E)
Off Choshi
Shimizu fish market
Kokufu(34°20'N, 136°52'E)

Stranded

S. attenuata

7

12

VIII

'35

8

20

x

'61

9

VIII

Nagasaki fish market(32°40'N, 129°50'E)
Arikawa(33°00'N, 129°06'E)
OnahamaMizue et al.,1962
Kasuya, 1972

Driven intemperature in the warmest and coldest months of 1970. This figure shows thatthe distribution of these species is not restricted in the coastal waters, but extends
into the offshore waters. The northernmost records in the summer season are beSci. Rep. Whales Res. Inst.,
No. 26, 1974

DISTRIBUTION AND MIGRATION OF STENELLA

235

tween 44°N and 46°N. This range approximately coincides to the 17°0 isothermalline in the summer season. Though the northern range of the two species in winterseason is not clearly indicated, it is suggested that they are distributed south of 17°0
isothermal line.
TABLE. 2.

No.

LIST OF SIGHTING RECORDS OF STENELLA SPP. IN THE
WESTERN NORTH PACIFIC.

Date

PositionTime

S. coeruleoalba
11
1
VIII
31
2
VIII
3
9
IX
4
8
VIII
5
18
VIII
13
IX
6
15
IX
7
22
IX
8
9
22
XI
10
21
XI
21
11
XI
19
12
13
19
14
19
15
21
I
16
5
II
17
24
x
18
8
x
19
8
x
11
20
x
21
10
II
22
JO
II
23
10
II

'51
'51
'51
'54
'54
'54
'54
'70
'70
'71
'71
'72
'72
'72
'72
'72
'72
'73
'73
'73
'74
'74
'74

Nemuro Bay
Ekacherina Bay
Laperyza Bay
38°18'N, 148°50'E
39°04'N, 153°30'E
41°28'N, 153°03'E
44°34'N, 149°5l'E
34°3l'N, 139°35'E
34°35'N, 139°38'E
34°48'N, 141°07'E
34°52'N, 141°05'E
29°36'N, 140°38'E
29°32'N, 140°42'E
29°07'N, 141°ll'E
26°39'N, 142°28'E
20°17'N, 152°12'E
34°52'N, 141°05'E
34°48'N, 139°54'E
34°44'N, 139°47'E
35°02'N, 139°18'E
32°05'N, 132°12'E
32°52'N, 133°08'E
31°28'N, 134°09'E

13: 45
14: 2011 : 10
10: 3608: 0509: 26
12: 1807: 55
11: 46
15: 34
10: 00
11: 2508: 0007: 00
12: 00
16: 40S. attenuata
24
10
25
22
26
22
27
22
28
7
29
7
30
8
31
23
32
23
33
24

'67
'72
'72
'72
'72
'72
'72
'73
'73
'73

26°40'N, 124°50'E
25°55'N, 143°38'E
25°32'N, 142°00'E
25°22'N, 142°43'E
23°30'N, 151°42'E
23°35'N, 151°35'E
24°05'N, 149°09'E
31°28'N, 134°36'E
32°03'N, 135°0l'E
33°19'N, 137°52'E

06: 40
09: 41
11: 22
12: 23
16: JO
16: 0006: 40
11: 0005: 05

XII
I

II
II
II

v
v
v

Surfacetemperature(°C)

Schoolsize

Author

150
50
20-30
2,000
400
150-200

Sleptsov, 1961

22.7
22.7
20.6

10
1,000
60-70

Present data

19.8
19.8
21.4
21. 7
25.5
20.5
24. 7
25.4
23.1

50
30
100
10
30
200
50
500-1,000
20-30
50-60
100
20

Masaki, 1972

22.2
21.9
21.4
24.3
24.5
24.8
19.0
19.0
16.8

50
50
50
20-30
20-30
20-30
30

Present data

Masaki, 1972

Present data

5

The similar feature is also observed in the water temperature at the positionsof sighting collected by us or reported by various authors (Table 2). The 32 records
of water temperature at the sighting position of S. coeruleoalba and the 9 records atthe sighting position of S. attenuata are in the range between 16.8°0 and 26.0°0.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

MIYAZAKI, KASUYA AND NISHIWAKI

236

These informations suggest that the two kinds of the dolphins are distributed, inthe western North Pacific, in the waters influenced by the Kuroshio current. Fig. 8
shows the oceanographical structure and the positions of sighting of S. coeruleoalba.
The schools of this species seems to be concentrated near the area where the warm
water intrudes into the colder water at the periphery of the Kuroshio current.
Similar oceanographical structure is observed at the southeast entrance of Sagami
Bay in the winter season (Kasuya, 1972; Miyazaki et al., 1973 ), and at the southeast

130°E

150°E

140°E

50°N

•9
40° N

•8

17°C On 1-1 O Mar.

30°N

~·1
0

•1 0

12
0

0

1

1 1
0

2

Oo

22

20°N
Fig. 7. Map showing the geographical distribution of Stenella coeruleoalba and Stenella
attenuata. The numerals by the symbol indicate the month of sighting or collecting. A; Arari, F; Futo, K; Kawana, T; Taiji. The l7°C isothermallines
are for 1970 (Japanese Meteorological Agency).

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

237

DISTRIBUTION AND MIGRATION OF STENELLA

area of Suruga Bay in winter and spring dolphin fishing season (Fig. 9). These
places coincide with the important fishing ground of the dolphins. Though thespecies was not identified, there is observed in October and December a peak of
landing of dolphins at the Choshi fish market (35°44' N, 140°52' E). This peak will
140°E

141° E

140 E

141°E

20'

35'N

40'

,....,, .........
'I

>\

,,-

'-)

\

}

"

e e

pp

On19-25 Nov.1971
20'

I

Fig. 8. The oceanographical condition and the sighting position of the dolphin
obtained through 2 cruises of the Tanseimaru. S; Stenella coeruleoalba, L; Lagenor-hynchus, T; Tursiops, D; Delphinidae, P; sperm whale, G; Globicephala, R;
Grampus, M; minke whale, Z; Zyphiidae. Solid line indicate surface water isothermal line, and broken line the 200 m depth.

40'

40'

20'

/

20'

40'

20'

21°
/

2:(o

Fig. 9. The oceanographical condition in Suruga Bay in 1967. Solid line indicatessurface water temperature. (Shizuoka Fisheries Experiment Station, 1967).

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

238

MIYAZAKI, KASUYA AND NISHIWAKI

probably represent the catch of Stenella spp. in the waters off Choshi, where the similar intrusion of warm water is observed (Fig. 8). It is interesting to note that there
occurs no intrusion of warm warter in the spring at the southeast entrance ofSagami Bay, and that this area has no spring dolphin fishing season.
DISCUSSION

Hubbs et al., (1973) summarized all known records of S. coeruleoalba in the North Pacific, and showed that this species is distributed continuously from the west coast of
North America to the central tropical Pacific. The sighting records reported by
Masaki (1972) now suggest that the continuity of the distribution can be extended
to the Japanese coastal waters. But this does not necessarily mean that S.
coeruleoalba in the both sides of the North Pacific belongs to one population. It will
be more reasonable to expect several separate populations in the North Pacific.
Stenella spp. and probably other tropical or subtropical dolphins seem to concentrate at the area where the warm water at the periphery of the Kuroshio current
intrudes into the colder water as suggested by Kasuya (1972) and shown on large
cetaceans by Uda (1954). This assumption can explain the mechanism concerning
the formation of the several fishing grounds and fishing season. We don't deny
all the possibility where the concentration of dolphins occurs on the steep slope
along the continental shelf (Tobayama 1969). But this hypothesis can not explain
the presence of the fishing ground near Choshi, because the sea floor off Choshi isflat and shallow.
The winter peaks for S. coeruleoalba and S. attenuata are observed in the earlier
season in Sagami Bay at the north, and off Kii Peninsula at the south they delay forabout one month. The time lag between Sagami Bay and Suruga Bay in closer
distance is larger than that between Suruga Bay and Kii Peninsula in larger distance.
This suggests that the time lag is related to the speed of the seasonal change of theoceanographical conditions or the seasonal movement of the area where the northernboundary of the Kuroshio current crosses the coastal waters. The spring peak observed in the catch at Taiji (Kii Peninsula) and Arari (Suruga Bay) will correspondto the northbound movement of the northern boundary of the Kuroshio current
and that of dolphins induced by it. These features of the seasonal migration of thedolphins are close to that suggested by Ohsumi (1972). But it must be noted thatthe migration of these dolphins seems to be the shift of the area of the higher densityof dolphins resulting in the expansion or retreat of the range of the distribution.
Compared with the peaks of S. coeruleoalba, the winter peak of S. attenuata arrives
earlier and the spring peak later. This indicates that S. attenuata lives in the warmer
waters and possibly in the lower latitudes than S. coeruleoalba does.
As the catch of the two species of the dolphins are strongly affected by the annual fluctuation of the Kuroshio current, it was impossible to analyze the fluctuation of the population based on the fishing statistics covering only a short period.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

DISTRIBUTION AND MIGRATION OF STENELLA

239

ACKNOWLEDGEMENTS

Sincere thanks are due to the members of the fishermen's cooperative unions at
Kawana, Futo, Arari, and Taiji, who are very helpful in collecting the data. We
extend our hearty thanks to the members of the Tanseimaru, who kindly supported
us in studying the dolphins on the vessel.
Dr. T. Kajihara and Dr. K. Numachi of The Ocean Research Institute, and
Mr. R. L. Brownell of The Smithsonian Institution are acknowledged for their cooperation and the valuable suggestions.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

MIYAZAKI, KASUYA AND NISHIWAKI240

REFERENCES
HmASHIKAWA, S., H. KITAMURA, Y. MoTOMURA, K. YAMAMOTO, and T. KATAOKA, 1966. Dolphins in
Mie prefecture. Mu Seibutsu 16: 49-52. (in Japanese)
HUBBS, C. L., W. F. PERRIN, and K. C. BALCOMB, 1973. Stenella coeruleoalba in the eastern and central
Pacific. J. Mamm., 54(2): 549-552.
JAPANESE MARINTIME SAFETY AGENCY, 1961-1971. State of the Adjacent Seas of Nippon. Vol. 2-4. Tokyo.
KASUYA, T., 1971. Consideration of distribution and migration of toothed whales off the Pacific coastof Japan based upon aerial sighting record. Sci. Rep. Whales Res. Inst., 23: 37-66.
KASUYA, T., 1972. Growth and reproduction of Stenella caeruleoalba based on the age determination bymeans of dentinal growth layers. Sci. Rep. Whale Res. Inst., 24: 57-79.
KAsUYA, T., N. MIYAZAKI, and W. H. DAWBIN, 1974. Growth and reproduction of Stenella attenuata in
the Pacific coast of Japan. Sei. Rep. Whales Res. Inst., 26: 157-226.
MASAKI, M., 1972. Tagging investigation of whale in Ogasawara and Mariana Islands. Geiken Tsushin,
249: 35-42. (in Japanese)
MIYAZAKI, N., T. KusAKA, and M. NISHIWAKI, 1973. Food of Stenella caeruleoalba. Sci. Rep. Whales Res. Inst.,

25: 265-275.
MIZUE, K., and K. YosHmA, 1962. Studies on the little toothed whales in the west sea area of Kyusyu
IX. About Prodelphinus sp. so-called "Madara iruka" in Japan caught at Arikawa in Goto Is.,
Nagasaki Pref. Bull. Fae. Fish. Nagasaki Univ., 13: 1-8. (in Japanese)
MIZUE, K., K. YosHIDA, and S. SONODA, 1964. Studies on the little toothed whales in the west sea areaof Kyusyu X. About Prodelphinus sp. so-called "Hashinaga iruka" in Japan caught in the sea areaaround Goto Is. Nagasaki Pref. Bull. Fae. Fish. Nagasaki Univ., 17: 10-24. (in Japanese)
NisHIWAKI, M. and T. Yagi, 1953. On the age and the growth of teeth in a dolphin (Prodelphinus caeruleoalbus). Sci. Rep. Whales Res. Inst., 8: 133-146.
NISHIWAKI, M., M. NAKAJIMA, and T. KAMIYA, 1965. A rare species of dolphin (Stenella attenuata) from
Arari, Japan. Sci. Rep. Whales Res. Inst., 19: 53-64.
OGAWA, T., 1936. Studien iiber die Zahnwale in Japan. Botany and Zoology, 4(7): 1159-1171. (inJapanese)
OGAWA, T., 1936. Studien iiber die Zahnwale in Japan. Botany and Zoology, 4(8): 1337-1344. (inJapanese)
0HSUMI, S., 1972. Catch of marine mammals, mainly of small cetaceans, by local fisheries along the coastof Japan. Bull. Far Seas Fish. Res. Lab., 7: 137-166.
OKADA, Y., 1936. A study of Japanese Delphinidae. Sci. Rep. Tokyo Bunrika Daigaku. Sect. B., 3(44-45): 1-16.
PERRIN, W. F., 1972. Color patterns of spinner porpoises (Stenella cf. S. longirostris) of the ea~tern Pacificand Hawaii, with comments on delphinid pigmentation. Fish. Bull., U.S., 70(3): 983-1003.
SAMPSON, W. F., 1970. Stenella eoeruleoalba in the northern Pacific Ocean. J. Mamm., 51(4) 809.
SHIZUOKA PREFECTURAL FISHERIES EXPERIMENT STATION, 1967. The report of working result for forecast OJ
fishing and oeeanographieal condition. Shizuoka Prefectural Fish. Exp. Station. 29 pp.
SLEPTSOV, M. M., 1961. Observations of small cetaceans in far eastern seas and northwest Pacific. Trudy
Inst. Morf. Zhivoth., 34: 136-143.
ToBAYAMA, T., 1969. School size and its fluctuation in the catch of Stenella eoeruleoalba in Sagami Bay.
Geiken Tsushin, 217: 109-119. (in Japanese)
TOKYO METROPOLITAN FISHERIES EXPERIMENT STATION, 1971. Surface water temperature data of stationary
observation in Izu Islands (1920-1970). Tokyo Metropolitan Fish. Exp. Station, no. 218. 108 pp.
UDA, M., 1954. Studies of the relation between the whaling grounds and the hydrographical conditions (I). Sci. Rep. Whales Res Inst., 9: 179-187.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

241

DISTRIBUTION AND MIGRATION OF STENELLAAPPENDIX I. THE NUMBER OF CATCH OF STENELLA COERULEOALBA AND
STENELLA ATTENUATA (IN PARENTHESES) IN ARARI.
Jan.

1950

60

1951
1952

2, 194
245

Feb.

Mar.

Apr.

May

June

July

10

4,794

3,293

47

93

1,321

1,990

1,231
(1)
826
1,321

(25)
88

19

759
(6)

62

125

1953
1954
1955

53

1956

1,390

69

1957

261

102

274

1958
1959

1,274
4, 117

79

151
76

Sep.

Aug.

Oct.

Nov.

646
11
153
(65)

245
69
611

48

68
(257)

275

(188)

1960
1961
1968
1970
Total

1,440

63
671
(83)
67

151

613

11

63 613
(188)

11

90
9,745

1,565

281
(25)

6,384

41
6,584
(6)

5, 104 1,180
(341)
(6'5)

67

Dec.

Total

4,236 13' 671(1)2,469 9,664
4,050 5,627
(25)
1,081
(71)
298
2,483 2,552
(15)
(15)
3,634 5,752(188)
1, 771 2, 751
(257)
1,567
6,304
(83)
67
775
90
41
18,643 50,240
(640)
(15)

APPENDIX II. THE NUMBER OF CATCH OF STENELLA COERULEOALBA AND
STENELLA ATTENUATA (IN PARENTHESES) IN TAIJI.
Jan.

Feb.

Mar.

Apr.

May

1963
1964
1965
1966
1967
1968
1969
1970

16
252
207
129
336
175
77
331

30
247
138
177
206
112
3
81

34
162
29
15
29
4

18
25
17
12
29
42
3
3

46
11

1971

423
(1)
288
(2)
2,234
(3)

178

11

1972
Total

28
(3)
1,200
(3)

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

2
286

(1)
1
150
(11)

June July Aug. Sep. Oct.

4
1
14

2
3

4

Nov.

Dec.

Total

3
5
(1)
35
(3)
5

63
93
78
7
97
6
74
114
(8)
327
(19)
68

120
131
121
77
105
27
237
444
(5)
730
(19)
239

104
(4)

927
(27)

2,231
(14)

331
934
642
422
819
400
499
997
(14)
1, 717
(37)
700
(12)
7,461
(63)

9
30

5
16
33
90
7
5
(4)
30
(3)
227
(7)

12
8

4

8
39
(4)
87
(4)

7

5

3

242

MIYAZAKI, KASUYA AND NISHIWAKIAPPENDIX III.

THE NUMBER OF CATCH OF STENELLA COERULEOALBA

Sep.
E
1949-'50
1950-'51
1951-'52
1952-'53
1953-'54
1954-'55
1955-'56
1056-'57
1957-'58
1958-'59
1959-'60
1960-'61
1961-'62
1962-'63
1963-'64
1964-'65
1965-'66
1966-'67
1967-'68
1968-'69
1969-'70

M

Nov.

Oct.
L

E

M

L

E

1,035

374

71

275
283
268
183
686
116
1,634
404

510

364

862
717
237

99
820
50
101
1,324

158
453
351
248
191

169

510
401

293

603
(881)

1971-'72

1,310
(159)
517

1972-'73

503

1,117

1973-'74

1,140

512

3,969
(159)

4,849

470

29

1970-'71

Total
*:

M

L

408

131

408

131

102
(213)
143
(786)
6,011
(1, 880)

11
145
(435)
0
(1, 657)
25
631
(189)
116
(376)
5, 151(2' 657)

162
952
160
173
1,229
251
162
1,643
1,840

279
310
210
1,903
1, 187
389
1,445
2,768
1,203
2,325
1,345
355

314

2, 197

776
815
(260)
3,277

4,067

12,335(260)

20,471

488

The total catch at Futo and Kawana, but only the catch at Futo is given by month.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

DISTRIBUTION AND MIGRATION OF STENELLA

243

AND STEJ'iELLA ATTENUATA (IN PARENTHESES) IN KAWANA AND FUTO.

Jan.

Dec.

Feb.
Total

E

M

L

E

M

L

E

327
1,515

168
605
3,248
1,477
467
135
3,253
504
948
389

148

2,755

146
6,257
1,401
637
1,084
843
1,500
542

973
452
160
68
0
2,846
1,675
1,967
50
131

903

1,094

1,805

100

378
870
738
892
107
62

47
420
229
119
533
109

129
612
106
36
74
56
33
24

1,557

1,070

69

4,534

459

975

148

15,597

13,609

L

735
1,515
2,235

2,235

1,127

M

11, 651

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

9,386

69

4, 1482,876
2,569
10,5898,269
8,535
6, 103
15,649*14,351*8, 1984,626
3, 130(435)
5,307(2,697)
3,315
(0)
7,235
(662)
6,799
(1,162)
118,939(4,956)

BRAIN MORPHOGENESIS IN STENELLA COERULEOALBATOSHIRO KAMIYA
Department of Anatomy, Faculty of Medicine, University of Tokyo, Tokyo

PAUL PIRLOT
Departement des Sciences Biologiques, Universite de Nlontrlfal, Montreal

ABSTRACT

Based on a series of 15 embryos and two new-born spcimens of Stenella
coeruleoalba, a description of the changes in shape of the brain as size increases
is given. Such changes involve strong brachycephalization and proliferationof transverse gyri. A temporary fetal pattern of the cortex in this species reminds one of a permanent adult condition in more primitive dolphins. The
prominent development of vestibulocochlear nerve and the temporal regionis also emphasized.

INTRODUCTION
One of the fundamental problems involved in any attempt at understanding thebiology of animals is that of the relations between structures and functions, that is
between morphology and physiology. Part of the treatment of that problem isan investigation of the ontogeny of brain structures, which is necessarily related tothe emergence of brain functions. This points to the value of studying ontogenetic
series i.e. embryonic and young animals.
The present paper is concerned with the gradual growth and differentiation of
the brain in a dolphin, that is with its morphogenesis. The complexity of that problem is well known. The study of the vertebrate brain raises particular and intricate question concerning the relation between size and shape in the course of specificontogenesis (see a review by Gould, 1966). We would like to contribute to the discussion with observations on a good series of brains from fetal dolphins. Both thesize and the structural complexity of the brain in these animals make it a particularly
favourable material; further, the well known high encephalization and corticalization of dolphins, as well as the sophistication of their sensory system (sonar) rendersuch a study especially interesting. Kamiya (1962) and Hosokawa et al. (1969)
have studied the embryonic development of the acoustic system with the myelinization method in Stenella coeruleoalba.
MATERIAL AND METHOD
The dolphin species dealt with here is Stenella coeruleoalba. Fifteen embryos ranging
in size from 3.6 to 74.0 cm in body-length and two postnatal young (115.5 and
135.0 cm long respectively) were used. This selection of specimens was made from
Sci. Rep. Whales Res. Inst.,

No. 26, 1974, 245-253

KAMIYA AND PIRLOT

246

a series of 67 individuals (48 prenatal and 19 postnatal) which is being used for another growth study (Pirlot and Kamiya, in preparation). All that material was collected by Kamiya from Kawana and Futo, Shizuoka Prefecture (Table 1).
The principle of this study is to compare the prenatal brains with the postnatal
ones and also to compare the prenatal brains with each other. The brains were examined from four distinct aspects: in lateral view (norma lateralis ), in sagittal section (norma media), in dorsal view (norma verticalis) and in ventral view (norma
basalis ). A series of photographs were taken for each aspect and will be commented upon below. In order to make the visual study as easy as possible, we used thefull area of the photograph in each case. Thus the brains are not shown to scale.
The real size, however, can be estimated readily from the small scale provided
with each picture. The dissecting work was done by Kamiya and the photographs
also taken by him on 35 mm film with a 55 mm Takuma 1: 2 lens or a 100 mm
Takuma 1: 4 lens mounted on a bellow attachment with Asahi body.
TABLE l.
Body length (cm)

3.6
6.0
7.5
10.4
19.0
24.0
26.0
31.0
32.0
35.0
38.4
42.0
42.5
51.0
74.0
115.5
135.0

Sex

MATERIAL.
Body weight (g)Brain weight (g)

3.4
7.0
11.0
26.8
115.0
300.0
362.0
460.0
500.0
640.0
870.0
930.0
1220.01780.04020.019450.0

0.2
0.4
0.8
1.6
5.6
15.0
18.0
21.0
25.0
32.0
37.0
51.0
58.0
110.0
228.0
680.0
740.0

F
F
M
M
F
M
F
M
F
F
F
M

RESULTS

The description follows the order of the four distinct aspects as defined above,with a preliminary note on the postnatal brain.
Postnatal brain. It is convenient to start with a rapid examination of thepostnatal brain of the 135.0 cm specimen (Plate I, 1). The caudad expansion of
the hemisphere is striking; in fact, the cerebellum is almost invisible from above
because it is covered by the telencephalon. Another impressive characteristic is
the relative cephalo-caudal shortness or the relative great transverse width of theentire brain (brachycephaly). The complex cortical folding resulting in numerous
Sci. Rep. Whales Res. Inst.,
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DOLPHIN BRAIN MORPHOGENESIS

247

gyri can be appreciated. It will be noted that no major sulci, either in a longitudinal or transverse direction, exist. In norma basalis (Plate I, 2), the bulging of thetemporal cortex is especially noticeable as well as the large size of the cerebellum.
One must also note the enormous vestibulocochlear nerve as well as the large trigeminal and optic nerves. In norma lateralis (Plate I, 3), the multiplicity of thegyri is also quite striking and the presence of a Sylvian fissure can be pointed to.
This must be compared with Platanista gangetica (Plate IV, 3) and also with the pictures in Pilleri and Gihr ( 1970, Plate 7) for Tursiops truncatus, and also in Gruenberger, (1970, Fig. 5) for Inia geojfrensis as well as in Pilleri (1972, Plate 4) for Platanista
again. One important feature that we shall have to comment upon later is theabsence in Stenella of the cephalo-caudally oriented and longitudinal sulci that are
typical for Platanista (Pilleri, 1972, Plate 1). The suprasylvian and ectosylvian
fissures are but slightly visible in our specimen; they seem to be somewhat clearer
in Inia (Gruenberger, 1970, Fig. 6) and in Pontoporia blainvillei (Pilleri, 1972, Plate
15, 3). On the other hand, the fan-shaped arrangement of the gyri, frontward andupward from the Sylvian fissure, is striking in Stenella, much more so than in Inia
(Gruenberger, 1970, Fig. 6). In norma media, the relatively strong antero-ventral
development of the hemisphere is noticeable. The genu of the corpus callosum
accordingly reaches fairly far forward and downward. Well marked are the mesencephalon roof (corpora quadrigemina) and the pontine transverse formation. The
colliculi inferiores, however, appear to be relatively smaller than in Tursiops (Pilleri
and Gihr, 1970, Plate 3) and Platanista (Pilleri, 1972, Fig. 10), if, as it seems, allthose sections are really comparable (sagittal). A great difference between thosespecies is the relatively poor distinctness of the gyrus cinguli in Stenella, whereas
this is so clear in Platanista and in Pontoporia (Pilleri, 1972, Fig. 5 and Plate 5, 10) as
well as in Inia (Gruenberger, 1970, Fig. 7).
All those features, briefly described for Stenella in comparison with other dolphins, especially Platanistidae, will be reconsidered hereafter in the ontogenetic sequence of prenatal and young postnatal specimens.
Norma lateralis in ontogeny (Plates II, III, IV). The first three figuresof Plate II refer to the same specimen. They firstly show the embryo before dissection(Fig. 1), with the two humps made by the bulging telencephalon and mesencephalon. In Fig. 2, one sees the dissection in progress, with the above named parts ofthe brain still in situ. The mesencephalic and cervical flexures are quite clear, andthe pontine flexure on the dorsal side as well. For the sake of comparison, it may
be mentioned that these three flexures are already present in a 6. 7 mm human embryo (about 34 days) according to Hamilton, Boyd and Mossman (Fig. 153).
Figure 3 presents the same brain after dissection. A comparison of Figs. 3, 4 and 6
reveals immediately the attenuation of the coiled, elongate and almost tubular aspect of the total brain as well as the relative increase of the telencephalon. The
overall shape becomes bulkier, the parts (telencephalon, mesencephalon, rhombencephalon) begin to telescope into each other. On Plate III, Fig. 1, the apparent
dilatation of the hemisphere increases. Between stages of Figs. 1 and 2 of Plate
III, the morphogenesis progresses considerably from a qualitative viewpoint in parSci. Rep. Whales Res. Inst.
No. 26, 1974

248

KAMIYA AND PIRLOT

ticular: this is remarkable since the total size increase between the two stages is about
37 % whereas it was over 80% between the two preceeding stages (Plate II, Fig. 6
and Plate III, Fig. 1) with less morphological differentiation. In this important
step (Figs. 1 and 2 of Plate III), the surfaces of the hemispheres and of the cerebellum begin to differentiate while their size increases. The mesencephalic roof sinks
and disappears beneath the overhanging cortex in lateral view. A Sylvian fissure
begins to appear. Figuers 4 to 6 show the formation of the gyri. From 3 through 6,
their fan-shaped arrangement above the Sylvian fissure becomes more marked.
The coiled aspect of the gyri is predominent from stage 5 of this plate. A certain
longitudinal orientation of the first groves may be seen temporarily in Figures 3 and4 but this is temporary. On Plate IV, Fig. 1, we have a view of the brain shortly
before birth while Figure 2 represents the brain shortly after birth. The questionof size set apart, the general aspect is very much similar in both specimens. The
gyri, however, are more tightly packed in the postnatal specimen than in the otherone. Contrasting with our postnatal example, one can notice the longitudinal(cephalo-caudal) orientation of the gyri in the brain of Platanista, Plate IV, 3. The
radial arrangement as seen in Stenella practicially does not exist in the platanistids.
Norma media in ontogeny (Plate V). We present on Plate V six sagittal
sections of fetal brains of Stenella, from 24 to 51 cm, that is through stages corresponding roughly to those of Plate III. The gradual formation of the corpus callosum canbe observed as well as the begining and complexification of the gyri on the medialsurface. One can appreciate the relative morphic stability of the brain-stem portion: there is little change of shape in it. The relative size of the mesencephalicbulge (colliculi) decreases from section 1 to section 6. The fissura splenialis is wellmarked but the fissura genui much less so and the fissura suprasplenialis also is quite
faint. In the early postnatal (Plate I, 4), the same fissurae are also difficult to trace,
except for the caudal half of the splenial fissure, contrarily to what can be observedin the platanistids brains shown by Pilleri (1972).
Norma verticalis in ontogeny (Plates VI, VII). Both the change in relative
size of parts and the change in shape can be fully appreciated from the fetal series
seen in dorsal view. This sequence (12 specimens) is particularly striking.
It starts with the predominence of the mesencephalon, which makes, with the
medulla oblongata, the main mass of the very early Mammalian brain, as shown
quantitatively by Pirlot and Bernier (in press). The lateral hemispheric lobes arestill quite small in Fig. 1 while the cerebellum is no more than an annular thickening.
Stages in Figs. 2 to 5 are characterized by the relative decrease of the caudal halfof the brain and the rapid increase of the hemispheres. The colliculi begin to shapeup clearly in Fig. 2. It will be noticed that, for a time, the cerebellum remains
almost unchanged in outline, a fact observed in bats by Pirlot and Bernier (in press).
The rapid and profound modification of the brain surface between sizes 19 and26 cm, already observed in the norma lateralis aspect, is also very striking in dorsal
view. It is important to note the longitudinal (cephalo-caudal) orientation of thesulci that appears in Figs. 6 and 7 of Plate VI. The first one seems to be the fissura
lateralis (fissura marginalis) (Fig. 6) while the fissura endolateralis begins to be visible
Sci. Rep. Whales Res. Inst.,
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DOLPHIN BRAIN MORPHOGENESIS

249

on Fig. 7. Both are better marked at the 35 cm stage (Plate VII, 1) but they become
somewhat less distinct soon after (38 and 51 cm, Plate VII, 2 and 3). In fact, thatis due to the rapid complexification of the gyri system in all directions: among thosegyri, the first fissures become less conspicuous. The foliation of the cerebellum iswell under way from 26 cm (Plate VI, 6). The sequence 26 to 74 cm corresponds
to a marked and rapid increase in both mass and suprficial area. That period must
be one of very active histological proliferation all over the surface of the brain. In
Plate VII, 5, the anterior cerebral artery is visible in the fissure lateralis (left side of
the picture with arachnoid membrane). Finally, another striking feature that canbe observed in the photographs (although these are not to scale) is the fast change
in the width/length ratio. This ratio passes roughly from 58 % at 3.6 cm to 82 %at 10.4cm, practically 100% at 19 cm, 114% at 31 cm, 133% at 74cm i.e. shortly
before birth and also soon after (115.5 cm). This of course simply reflects thechange from an elongate outline to a rather telescoped shape which occurs in all
developing Mammals but the modification is particularly strong in this dolphin.
Norma basalis in ontogeny (Plates VIII, IX). As seen from the ventral
aspect, the morphogenesis of the brain is mainly characterized by a gradual differentiation of distinct regions and thus a general structural compkxification. In thefirst four stages shown here (Plate VIII, 1 to 4), the main masses, that is prosencephalic and rhombencephalic, are visible, at first deeply then later shallowly separated
by the mesencephalic flexure. The lateral lobes and the cerebellum,' however,
begin to shape up in Fig. 4 (10.4 cm). Thereafter, the differentiation is fast: themodelling of the whole undersurface progresses rapidly while the hypothalamic andpontine regions begin to show theire spective specific structures (Plate VIII, 5 to 7;
Plate IX, 1 and 2). The hypophyseal mass is early visible in this series. The
cranial nerves posterior to the optic appear as early as stage 19.0 cm (Plate VIII, 5).
The trigeminal is first visible but the facial-acoustic-vestibular complex takes shape
as a large double root a little afterward and is clearly visible at 35.0 cm (Plate
IX, 1). Nervus vagus (X), nervus accessorius (XI) and nervus hypoglossus (XII)intermingled and nervus abducens (VI) are also formed in the 51 cm fetus. Nervus
oculomotorius (III) is visible at 115.5 cm but was probably lost in the dissection ofsmaller embryos. The inferior olive starts bulging from the 19.0 cm stage and isquite distinctly individualized at stage 42.0 cm or even before.
CONCLUSION
From the above study of a series of prenatal and early postnatal brains of Stenella
coeruleoalba, we can draw the following conclusions.
a) General morphogenesis. The changes in shape, as size increases, arevery striking, in the sequence under consideration. The brain of this species starts
its development with elongate outlines as is the case in all Mammals. But the modification is much more pronounced than in most other Mammals, in the sense thatthe final stage of embryonic life shows an exceptionally broad and short brain. A
detailed quantitative analysis of the components' growth could give a satisfactory
Sci. Rep. Whales Res. Inst.,
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250

KAMIYA AND PIRLOT

account of what really occurs from that viewpoint during that remarkable ontogeny; we have such an analysis in preparation.
b) Cortical morphogenesis Gross anatomical observations of the cerebral lobes reveal interesting features. Dolphins are probably amont the most strongly gyrencephalic Mammals outside the Primates. But, in this respect, they are notuniform. In the adult stage, the genus Stenella differs markedly from some Platanistid genera with which we were able to compare it on the basis of other material aswell as of published reports and pictures. Indeed, Stenella is characterized by the
predominence of transverse (in the broadest sense) or at least not longitunidallyoriented gyri and sulci. Its superficial cortical pattern is extremely complicatedwith a large number of oblique sulci. But, in young embryos, longitudinal groves
are the first ones to appear, as we have shown. They become more or less blurred or
obliterated later as the adult pattern gradually sets in. This raises the recurrent
question of repetitive processes in ontogeny. The platanistids show an obviously
longitudinal orientation of the gyri and, further, platanistids are considered, onvarious grounds, a primitive group among dolphins. Our observations thus raisea fundamental problem in ontogeny with respect to phylogeny and evolution in
general: are the temporary longitudinal sulci in Stenella a case of ontogenetic repetition? Only a new investigation along this line on the morphogenesis of dolphin
brain can throw some light on that problem.
c) Morphogenesis in relation to sensory functions. The relationships
between the rate of development of the sensory control centers in fetal life and thestart of sensory activities are a very intricate problem. We will not venture into
discussing its implications in the case of Stenella, but we must nevertheless insist upon
the importance of the two following observed facts. Firstly, we have stressed theenormous size of the vestibulocochlear nerve (VIII) and, at the same time, the relatively great development of the temporal region in Stenella, both becoming obvious
as growth proceeds. The possible correlation between an extensive use of hearing abilities, including sonar, and the development of the temporal cortical area
remains mysterious, as far as we know. But whatever the results of researches onthat point may be, our observations are of interest. Secondly, we would like topoint to the total absence of an olfactory bulb in the rostro-ventral region of the brain
in Stenella as seen in gross morphological aspects.
APPENDIX

Embryos smaller than 3.6 cm were too small to permit dissection and photographyof the brain in gross morphological view. Approximately sagittal sections, however,
could be prepared for some of them as shown on Plate X. It is probably easier tolook at them in a decreasing size order.
In all embryos, the neurocoele is still quite large as can be expected. In Fig.
4, the spinal cord is visible over most of its length and the cervical flexure at the
fourth ventricle level is strongly marked. The ventral portion of the neural tube
is thick, especially in the pons-oblongata region, while its roof remains thin except
Sci. Rep. Whales Res. Inst.,
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DOLPHIN BRAIN MORPHOGENESIS

251

where the cerebellum is forming. A thalamic mass has been cut parasagitally andthe mesencephalic flexure is well marked. The third ventricle is still wide and theparasagittal section also cuts a large lateral ventricle. The blow-hole is visible dorsally to the snout and mouth.
Figure 3 presents a much younger stage (about 2/3 of the former in length).
It is not quite so well centered but it shows about the same features as figure 4 in aless advanced state. The blow-hole can be seen again and the flexures are marked.
Figures 2 and 1 are definitely different in aspect. While the membranous roof of
the fourth ventricle is showing the concavity that will correspond to the pontine andcervical flexures, the more rostral structures do not show yet the various parts very
distinctly. The common neurocoele just begins to divide into distinct cavities.
In Fig. 1, the general tube-like appearance can be noted, the forming brain overhanging indistinct notochordal tissue.
ACKNOWLEDGEMENTS

We wish to express our gratitude to the Ministry of Education ofJapan for financing
the collection and study of the dolphin with a grant to the first author, and to theJapan Society for the Promotion of Science for a Visiting Professorship at the University of Tokyo to the second author. Thanks are also due to Mr. N. Miyazaki of
the Ocean Research Institute, University of Tokyo for his help in collecting thematerial and to Dr. John Nelson, Monash University, Australia, for checking theEnglish text.
REFERENCES
GouLD, S.J., 1966. Allometry and size in ontogeny and phylogeny. Biol. Rev., 41: 587-640.
GRUENBERGER, H. B., 1970. On the cerebral anatomy of the Amazon dolphin Inia geoffrensis. Investigations
on Cetacea, 2: 129-144.
HAMILTON, W.J., J. D. BoYD and H. W. MossMAN, 1972. Human embryology. Heffer, Cambridge, 646 pp.
HosoKAWA, H., 1955. Cross-section of a 12 mm dolphin embryo. Sci. Rep. Whales Res. Inst., 10: 1-68.
HosoKAWA, H., S. IGARASHI, T. KAMIYA, and K. HrnosAwA, 1969. Morphological characteristics andmyelinization of acoustic system in the dolphins (Stenella caeruleoalba). Sci. Rep. Whales Res. Inst., 21:
95-123.
KAMIYA, T., 1962. The acoustic system and the behavior in the dolphin. Rep. Res. Minist. Educ. Agr. (II)1962: 111-112. (inJapanese)
PILLER!, G., 1972. The cerebral anatomy of the Platanistidae (Platanista gangetica, Platanista indi, Pontoporia
blainvillei, Inia geoffrensis). Investigations on Cetacea, 4: 44-70.
PILLER!, G. and M. GIHR, 1970. The central nervous system of the Mysticete and Odontocete whales.
Investigations on Cetacea, 2: 89-127.
PIRLOT, P. and R. BERNIER, (in press). Embryonic brain growth in a fruit-bat.

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KAMIYA AND PIRLOT

EXPLANATION OF PLATESPLATE I
External form of the brain with arachinoid. Male, 135 cm long.
Fig. I. Dorsal view,Fig. 2. Ventral view.
Fig. 3. Laterial view of the left half.
Fig. 4. Medial surface of the right half.
VIII: Vestibulocochlear nerve
II: Optic nerve
V: Trigeminal nerve
PLATE II
External form of the embryo and brain.
Fig. I. Photograph of the left side of 3.6 cm long embryo.
Fig. 2. Same embryo with cranial bone removed and brain shown in situ.
Fig. 3. External form, left half of the brain of 3.6 cm long embryo.
Fig. 4. Embryo, 6.0 cm long.
Fig. 5. Embryo, 7.5 cm long.
Fig. 6. Embryo, 10.4 cm long.
PLATE III
External form of the left half of the brain.
Fig. I. Embryo, 19.0 cm long.
Fig. 2. Embryo, 26.0 cm long.
Fig. 3. Embryo, 32.0 cm long.
Fig. 4. Embryo, 35.0 cm long.
Fig. 5. Embryo, 38.4 cm long.
Fig. 6. Embryo, 51.0 cm long.
PLATE IV
External form of the left half of the brain.
Fig. I. Embryo, 74.0 cm long, with arachnoid.
Fig. 2. Female, 115.5 cm long.
Fig. 3. Platanista gangetica, male, 117 cm long.
PLATE VMedian section of the right half of the brain.
Fig. 1. Embryo, 24.0 cm long.
Fig. 2. Embryo, 26.0 cm long.
Fig. 3. Embryo, 32.0 cm long.
Fig. 4. Embryo, 35.0 cm long.
Fig. 5. Embryo, 42.5 cm long.
Fig. 6. Embryo, 51.0 cm long.
Figs. 2, 4 and 5 with midbrain removed and showing gyrus.

Sci. Rep. Whales Res. Inst.,

No. 26, 1974

DOLPHIN BRAIN MORPHOGENESISPLATE VI
External form of the brain in dorsal view.
Fig. I. Embryo, 3.6 cm long.
Fig. 2. Embryo, 6.0 cm long.
Fig. 3. Embryo, 7.5 cm long.
Fig. 4. Embryo, 10.4 cm long.
Fig. 5. Embryo, 19.0 cm long.
Fig. 6. Embryo, 26.0 cm long.
Fig. 7. Embryo, 31.0 cm long.
PLATE VII
External form of the brain in dorsal view.
Fig. I. Embryo, 35.0 cm long.
Fig. 2. Embryo, 38.4 cm long, left hemisphere with arachnoid.
Fig. 3. Embryo, 51.0 cm long.
Fig. 4. Embryo, 74.0 cm long, with arachnoid.
Fig. 5. Female, 115.5 cm long, left hemisphere with arachnoid and arrow show
anterior cerebral artery.
PLATE VIII
External form of the brain in ventral view.
Fig. l. Embryo, 3.6 cm long.
Fig. 2. Embryo, 6.0 cm long.
Fig. 3. Embryo, 7.5 cm long.
Fig. 4. Embryo, 10.4 cm long.
Fig. 5. Embryo, 19.0 cm long.
Fig. 6. Embryo, 24.0 cm long.
Fig. 7. Embryo, 26.0 cm long, right hemisphere with arachnoid.
PLATE IX
External form of the brain in ventral view.
Fig. I. Embryo, 35.0 cm long.
Fig. 2. Embryo, 42.0 cm long, right hemisphere with arachinoid.
Fig. 3. Embryo, 51.0 cm long.
Fig. 4. Embryo, 74.0 cm long, hemisphere with arachinoid.
Fig. 5. Female, 115.5 cm long, right hemisphere with arachinoid.
P: Pons
0: Olive C: Crus cerebrum VII: Facial nerve.
VIII: Vestibulocochlear nerve.
PLATE X
Longitudinal median sections of embryos.
Fig. I. Embryo, I. I cm long.
Fig. 2. Embryo, 1.7 cm long.
Fig. 3. Embryo, 2.4 cm long.
Fig. 4. Embryo, 3.5 cm long.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

253

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FIRST ANTARCTIC RECORD OF A KILLER
WHALE STRANDING
HUGO P. CASTELLO
Centro Nacional Patag6nico de Geo-Helioffsica, Puerto Madryn, Pvcia. de Chubut, Argentina

ALDO P. TOMO
Instituto Antdrtico Argentina, Cap. Fed., Argentina

JORGE S. PANIZZA
Depto. Cs. Biol6gicas, Universidad de Buenos Aires, Cap. Fed., Argentina

On the afternoon (6 P.M.) of 16 January 1973, during a "Zodiac" out motor rubber boat collecting trip from Palmer Station (64° 45' S, 64° 58' W), Antarctica, toCormorant Island, looking for the blue-eyed shag (Phalacrocorax atriceps) we needed
for neurophysiological research (Torno, Panizza and Castello, 1973) arriving to theshore of Cormorant Island through a short channel carved in the rocks, we were surprised to find, during low-tide, a stranded killer whale (Orcinus orca), 5.2 meters
long and approximately 1. 5 metric ton in weight (Fig. 1). We took color photographs immediately and also some notes. The stranded "orca" was of female
sex; time since death was estimated on two weeks or more. Black and white colorsof the tegument had been partially removed by floating ice debris abrasion, someof the 25 powerfull teeth were broken, possibly by crashing floating ice against the
open mouth (Fig. 2). It was possible to observe, also, "tooth wear" as it has
been previously described (Caldwell and Brown, 1964) and some blood clots on arock just under the tongue. Even though 0°C water temperatures are common
during austral summer, air temperatures, specially during sunny days, may reach
l0°C or more, thus the sun had heated the body and visceral putrefaction had greatly
progressed when we met the carcass.
Some gas bubbles sporadically escaped from a 3 cm wide circular hole on thetegument of the middle back. No other wound was seen in the carcass. The bodywas full of gas and increased in width, so it probably floated.
Floating and drifting dead whales like the Balaenoptera a.ff borealis (Fig. 3)
are not common in the Antarctic. Scientific reports on stranded cetacea or bones
collected in those latitudes are few, only one skull of the " cruciger dolphin "(Lagenorhynchus cruciger) has been found and recently described from Livingston
Island (Islas Shetland del Sur) (Fraser and Noble, 1968) and one Phocoena dioptrica
collected at South Georgia (Fraser, 1968).
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along the coast of the tiny island. We realized then what had happened: in thesame way as it probably reached the shore it went away, floating and drifting like
Sci. Rep. Whales Res. Inst.,
No. 26, 1974, 255-258

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258

CASTELLO, TOMO AND PANIZZA

about its distribution is not available or whether it migrates or if stocks in the north
are separate from those in the south.
The second of us spent 1967 at Estacion Cientifica "Almirante Brown" (64°
50' S, 62° 50' W) and carried among other works, a record of cetacean sightings.
Three different species were observed in 19 occasions with a total of 34 specimens
observed in front of the main building of the Station in the period March-July.
Only once, the 6 of April (08.50 A.M. ), 5 killer whales were observed at Bahia Paraiso. As something unusual a whale (Balaenoptera spp.) was observed the 23 of Julyswimming between broken ice, while the last two were recorded the 15 of May.
It is almost sure that during the austral winter, before thick ice covers coastal
areas of the Antarctic Peninsula, killer whales move to open waters, probably swimming to subantarctic areas. This hypothesis has to be proved and we must remark
what has been previously stated: " research in the Antarctic so far has contributed
but little to what is known of this creature " (Fraser, 1964).
Hershkovitz (1966) gives 80 bibliographic mentions on Orcinus orca only 5 arereferred to sightings in antarctic waters at different places (Hope Bay; between
Powell and South Shetland Islands; 70° 23' S, 85° 57' W; 78° S, 170° E; 77° 46' S,
166° E).
In the period December 1972-February 1973, killer whales were observed ineight occasions in the Gerlache Strait (Castello and Duguy, in press) and in our
opinion this strait must be selected as an area for studying the behaviour and biologyof this important and largely neglected species.
REFERENCESCASTELLO, H.P. and R. DuGuv, (In press). Observations sur Jes Cetaces de Patagonie, Subantarctique etAntarctique (novembre 1972-fevrier 1973). Mammalia.
CALDWELL, D. K. and D. H. BROWN, 1964. Tooth wear as a correlate of described feeding behavior by
the killer whale, with notes on a captive specimen. Bull. Soc. Calif. Acad. Sc., 63(3): 128-140.
FRASER, F. C., 1964. Whales and whaling. In Antarctic Research (ed. R. Priestley and others) Butterworth, cap., XI: 191-205.
FRASER, F. C., 1968. Notes on a specimen of Phocoena dioptrica from South Georgia. Brit. Ant. Surv. Bull.,
16: 51-56.
FRASER, F. C. and B. A. NoBLE, 1968. A skull of Lagenorhynchus cruciger from Livingston Island, South
Shetland Islands. Brit. Ant. Surv. Bull., 15: 29-38.
HERSKOVITZ, P., 1966. Catalog of living whales. Bull. Unit. Stal. Nat. Mus., 246: 1-259.
RrcE, D. W. and V. B. SCHEFFER, 1968. A list of the marine mammals of the world. U.S. Fish Wild!.
Ser. Spee. Scient. Rep. Bur. Comm. Fish., 579: 1-16.
TAYLOR, R.J. F., 1957. An unusual record of three species of whale being restricted to pools in Antarctic
sea-ice. Proc. Zoo!. Soc. London, 129: 325-331.
ToMo, A. P., PANIZZA, J. S. and H.P. Y CASTELLO, 1973. Neurophysiological research in fishes andbirds at Palmer Station. Ant.]. U. S., VIII, 4, 202-203.
WILSON, E. A., 1907. Cetacea. Nat. Ant. Exp. Nat. Hist. Zoo!., II: 6-8.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

A MALFORMED EMBRYO OF STENELLA COERULEOALBATOSHIRO KAMIYA
Department of Anatomy, Faculf(y of Medicine, Universif(y of Tokyo, TokyoNOBUYUKI MIYAZAKI
Ocean Research Institute, Universif(y of Tokyo, Tokyo

At the present time, the dolphin drive fishery, mainly Stenella coeruleoalba on theeast coast of lzu Peninsula is cooperatively operated at Kawana and Futo villages. At these two villages, the fishing season starts in early October and closes
in January. The mean annual catch of S. coeruleoalba for both villages has been
5,157 individuals during the past 5 seasons (1969-'70 to 1973-'74).
In 1972, 21 schools of S. coeruleoalba were driven ashore at these two villages
and 7,235 individuals were killed. In that season, we examined 2,299 individuals
and 467 foetuses taken from 20 schools. On October 17 a school of 187 individuals
was driven into the Futo Port. This was killed between the l 7th and 19th ofOctober. The composition of 115 individuals of the school is shown in Table 1.
This table indicates that 60.5 percent of the females and 33.3 percent of the males inthis school had attained sexual maturity, and the socionomic ratio was 0.28. In
the course of field examination of those 115 individuals at Fu to village, we collected
17 foetuses. One was a small malformed embryo. The mother of this embryo
was 220 cm in body length and was estimated to be 8.5 years old. The age wasdetermined by the number of opaque dentinal layers. The condition of the ovaries
was not observed. Kasuya (1972) stated that females of S. coeruleoalba attain sexual
maturity at 9 years at the length 212 cm, so that it seems that this mother was inher first or second pregnancy.
TABLE I.

SCHOOL COMPOSITION OF STENELLA COERULEOALBACAUGHT ON OCTOBER 17, 1972.

Sex

Pregnant

LactatingResting

Female17(22 .4)27(35. 5)

0

Male
Total

MatureImmatureTotal

2(2 .6)
13(33. 3)30(39. 5)26(66. 7)76
39
115

Figures in parenthesis indicate percentages.

The external characters observed in this embryo were the following: Body
length (cranio-caudal): 9 mm; greatest breadth: 7 mm; body weight: 2.0 gr.
In ventral view, the cephalic region appears to be almost normal (Fig. 1). The eye
is easily identifiable and so is the maxillary area. In the dorsal half of the head
there is a groove or depression that cannot be identified with certainty. The manSci. Rep. Whales Res. Inst.,.No. 26, 1974, 259-263

260

KAMIYA AND MIYAZAKI

dibular region is not clearly defined. The mandible is probably not developing.
The upper limb bud is nearly normal on the left side (Fig. 2). On the right side,
it is either not developing or in a state of abnormal formation (Fig. 4).
The abdominal region is not normal looking and, in particular, there is a stringlike fold that can be the umbilical cord but it is not typical. The tail, as comparedto that of a normal embryo, is too wide and placed with its tip in the oral region(Fig. 1).
In back view (Fig. 3), one can see the almost normal developing vertebrae andthe segmentation. The curvature, from this aspect, is abnormally sideward. Comparing the two lateral views, one sees that, on the left side (Fig. 2), the appearance
is almost normal (see above remark on mandible) but on the right side (Fig. 4 ),there is a mass of unidentifiable lumps of tissues.
Internal structures were observed in this embryo which was embedded in paraffin, sectioned longitudinally and serially 10 µ thick, and stained with hematoxylin
and eosin for microscopical study. Also, we used an 11 mm long normal embryo ofthe same species for longitudinal serial sections to compare with the malformed embryo.
Fig. 5 shows an approximately sagittal section of the 11 mm normal embryo
S. coeruleoalba. In this embryo, one clearly sees that the brain and spinal cord andall of the primordia of the cranial nerves are already present. Also, each visceralorgan is quite well formed: primordial thymus, thyroid gland, lung, heart and liverwith much blood, splenic primordium, gonad, primitive pancreas, mesonephrosand metanephros respectively etc. are present.
One the contrary, in the malformed embryo which is covered with simple epithelium and the inner structure of which is mainly composed of mesenchyme cells, organ
formation is extremely abnormal in comparison with the normal embryo. In the
cephalic region, one cannot recognize any brain structure: there is only a non-differentiated nervous cell mass. In figure 6, the optic vesicle is cut near its centerwith the optic cup and the lens vesicle can be seen. The optic cup has inner andouter layers. The outer layer already presents the pigmented epithelium but thelayer formation is irregular. In the thoracic and abdominal regions, we can mainly
distinguish four kinds of tissue masses. Heart muscles, liver cells, neural tissue andsegmental structures (Figs. 7, 8, 9). Bundle-like heart muscles with intercalated
disks can be seen. The usual blood-cells accummulations were not observed.
Nervous tissue is degenerated but spinal ganglion-like masses were identified andglia cells are abundant.
This case is one of the malformed embryos at an early developmental stage. A
malformed embryo of S. coeruleoalba has been observed by Kawamura andKashita (1971). That case was a double monster with body length of 16.8 and17.2 mm respectively along a transverse axis. Rudimentary hind limbs in a matureindividual were also reported by Ohsumi (1969) and the external development of
normal embryos was described by Ogawa (1953). The normal cross-section of a
12 mm long embryo has been observed by Hosokawa (1955). Each of the above
three embryos was from the same species.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

MALFORMED DOLPHIN EMBRYO

261

REFERENCES
HosoKAWA, H., 1955. Cross-section of a 12 mm dolphin embryo. Sci. Rep. Whales Res. Inst., 10: 1-68.
KASUYA, T., 1972. Growth and reproduction of Stenella caeruleoalba based on the age determination bymeans of dentinal growth layer. Sci. Rep. Whales Res. Inst., 24: 57-79.
KAWAMURA, A. and K. KASHITA, 1971. A rare double monster of dolphin, Stenella caeruleoalba. Sci. Rep.
Whales Res. Inst., 23: 139-140.
OGAWA, T., 1953. On the presence and disappearance of the hind limb in the cetacean embryo. Sci.
Rep. Whales Res. Inst., 8: 127-132.
0HSUMI, S., 1965. A dolphin (Stenella caeruleoalba) with protruded rudimentary hind limbs. Sci. Rep. Whales
Res. Inst., 19: 135-136.

EXPLANATION OF FIGURES
Figs. 1-4. External form of malformed embryo of S. coeruleoalba. (ea. X 10.5).
2: Lateral view of the left side
3: Dorsal view
I : Ventral view
4: Lateral view of the right side
Fig. 5. Longitudinal median section of the 11 mm normal embryo of S. coeruleoalba(ea. X 10).
Figs. 6-9. Histological structure of malformed embryo of S. coeruleoalba.
6: Optic vesicle, L=lens (ea. x300)
7: Heart muscles (ea. x500)
8: Liver (ea. x500)
9: Segmental structure (ea. x 120)

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

262

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ORGAN WEIGHTS OF PONTOPORIA BLAINVILLEI AND
PLATANISTA GANGETICA (PLATANISTIDAE)TOSHIRO KAMIYA
Department of Anatomy, Faculty of Medicine, University of Tokyo, TokyoFUSAO YAMASAKI
Department of Biology, Sapporo Medical College, Sapporo

Ninety-five specimens of the Franciscana Pontoporia blainvillei were collected. by
the University of Tokyo Cetacean Research Expedition at Punta del Diablo,
Uruguay, from December 1972 to February 1973. Various measurements weretaken on the visceral organs of 14 of those animals; they are shown in Table 1.
Most of the organs were weighed fresh at Punta del Diablo, but some of themwere weighed after fixation in 10 % formalin solution.
The same organization collected 15 Susu, Platanista gangetica in the Brahmaputra River (Bangladesh) in 1969-'70 and similar quantitative data were obtained
from 4 individuals (Table 2).
We wish to compare the figures obtained from the heart, the pancreas and thekidney of both species (Pontoporia and Platanista ), limiting this paper to short noteson the raw data and percentages.
Heart. The relative weight of the heart varies from 0.42 to 0.69 % in Pontoporia and from 0.22 to 0.28% in Platanista. The difference is notable. This may be
because it is related to the difference of habitats, Pontoporia living in open coastal
water and Platanista in quiet inland fresh water.
Pancreas. These figures also are higher in Pontoporia than in Platanista. The
relative weight of the former ranges from 0.12 to 0.35% whereas that of the latter
varies only from 0.04 to 0.09%. We should point out that, in Platanista, the pancreas
occupies the usual retroperitoneal position but that, in Pontoporia, the greater part ofthe pancreas is enclosed in a mesentery, hanging more or less freely in the abdominal
cavity. Also it is worth noticing that the organ is a bulky suboval mass in Platanista
whereas that of the Pontoporia is flat and enclosed throughout most of the dorsal
layer of the omentum majus.
Kidney. A similar difference is observed between the kidney of Pontoporia(0.30 to 0.43%) and that of Platanista (0.12 to 0.27%). Two specimens of Platanista,
117 and 199 cm long, had right kidneys weighing* 45 and 83 g respectively, but
two specimens of Pontoporia approximately of similar size (113 and 171 cm) had
right kidneys weighing 60 and 170 g, respectively. In the case of one Inia geoffrensis
specimen with a body length of 204 cm, the kidney weight was 150 g. We get the
impression again that the sea-living Pontoporia possesses a relatively larger organ* weight of renculi without interrencular connective tissue.
Sci. Rep. Whales Res. Inst.,

No. 26, 1974, 265-270

266

KAMIYA AND YAMASAKI

than the fresh water inhabiting Platanista and Inia. This fact is reinforced by the
figures obtained from three more sea-dolphins i.e., Neophocaena phocaenoides (bodylength 150 cm) with a kidney weighing 210 g, Delphinus delphis (177 cm) with a 154 g
kidney and Stenella coeruleoalba (207 cm) with one of 186 g.
Observation of the lobulation of the kidneys also showed differences between
the sea and river dolphins. We found 46 and 57 renculi in Platanista, 75 and 90 in
Pontoporia, but 138 in Neophocaena, 269 in Delphinus and 270 in Stenella. However,notwithstanding that Inia lives in fresh water, it has a richly lobulated kidney with
215 renculi.
We plan to present more data in a forthcoming paper on other organs of thesame species and to discuss more thoroughly the possible significance of the seahabhat vs. the river-habitat concerning the relative size of those organs.
ACKNOWLEDGEMENTS

We are greatly indebted to Mr. R. L. Brownell, Jr., Department of Vertebrate
Zoology, National Museum of Natural History, Smithsonian Institution, Washington, D. C., who arranged for us to collect materials and to the staff of the National
Museum of Natural History, Montevideo, who helped make this project possible.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

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RLB. 836* calculated from the value after preservation in 10% formalin solution.
Figures in parenthesis indicate percentagt>s of body weight.

------~~-------

Blubber
Skeletal muscle

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Thymus
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SpleenM
10.9kg84.5cm

RLB. 838

0. 15* (0.00103)
0.15* (0.00103)

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1.7* (0.0117)
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120. O* (0. 828)
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280.0* (I .931)
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83. 5 (0. 576)
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RLB. 805-- -· ---

Continued ...

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105.0 (0.515)
300.0 (1.471)
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130. 0 (0. 637)F
20.4kg120.0 cm

RLB. 801

BODY LENGTH, BODY WEIGHT AND ORGAN WEIGHTS OF 14 SPECIMENS OF PONTOPORIA BLAINVILLEI.

~~~~--~--~~-

Sex
Body weight

Specimen field
numberBody length·°'..... ~~·TABLE 1.

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-

-..)

Nl
O"l

ti:I

>

>-l
tl

en

>
>-l
z>

I:'"

"t)

":!

0

>-l

Cl
::r::

ti:I

-

~

~

?;!

0

~

~.;~

~~

__O)

~ !:tJ
~

~~

;§

~

!:tJ

{~

{~
{~

{~

{~

7250.0 (31.385)
8630.0 (37.359)

0.5 (0.00216)
0.4 (0.00173)
0.6 (0.00260)
0.5 (0.00216)

1250. 0 (5. 411)
650. 0 (2. 814)
58. 0 (0. 251)
72.0 (0.312)
73.0 (0.316)
0. 6 (0. 00260)
0. 7 (0. 00303)
3.0 (0.0130)
13.5 (0.0584)

8'610.0 (33.898)
8700. 0 (34. 252)

0.25(0.000984)
0. 2 (0. 000787)

215.0 (0.846)
130.0 (0.512)
4.2 (0.0165)
145 .0 (0 .571)
175.0 (0.689)
350.0 (1.378)
1600. 0 (6. 299)
620.0 (2.441)
75. 0 (0. 295)
90.0 (0.354)
88.0 (0.346)
1.1 (0.00433)
1.1 (0.00433)
3.7 (0.0146)
21 . 5 (0. 0846)
0.2 (0.000787)

Figures in parenthesis indicate percentages of body weight.

3.2 (0.0108)
3.2 (0.0108)
3.8 (0.0129)
3.2 (0.0108)

3.2 (0.0108)
8.5 (0.0288)

145.0 (0.492)
5.3 (0.0180)
173.0 (0.586)
235. 0 (0. 797)
500. 0 (1. 695)
1400.0 (4.746)
850. 0 (2 .881)
62. 0 (0. 210)120.0 (0.407)
115.0 (0.390)

9130.0 (30.949)
10300.0 (34.915)* calculated from the value after preservation in 10% formalin solution.

Blubber
Skeletal muscle

Mammary {l
gland
r

Ovary

Epididymis { ~TestisThyroid
Thymus
Pituitary

AdrenalKidneyStomachIntestine
Liver
PancreasLung

150.0g(0.649)
5.4 (0.0234)
150.0 (0.649)
160.0 (0.693)--------

8350. 0 (29 .196)
10400.0 (36.364)

0 .15 (0. 000524)
0. 20 (0. 000699)

140.0 (0.490)
4.3 (0.0150)
110.0 (0.385)
140.0 (0.490)
450.0 (1.573)
2150.0 (7.517)
700.0 (2.448)
63. 5 (0. 222)
95.5 (0.334)
91.0 (0.318)
1. 3 (0. 00455)
1.3 (0.00455)
6.0 (0.0210)
48.5 (0.170)

F
28.6 kg

M
29.5kgM
23.1 kg

Brain
Heart
Spleen132.0 cm131.5 cm

130.0 cm

123.0 cm

Sex
Body weightF
25.4 kg

RLB. 802

RLB. 808

RLB. 818

RLB. 807

Continued.

Specimen field
numberBody length

TABLE I.

Continued ...

8530.0 (29.414)
10140.0 (34.966)

0.2 (0.000690)
0. 25 (0. 000862)

230.0 (0. 793)
150.0 (0.517)
2 .8 (0.00966)
125.0 (0.431)
175.0 (0.603)
410.0 (1.414)
1700. 0 (5. 862)
800.0 (2. 759)
91. 0 (0. 314)
100. 0 (0. 345)
87 .0 (0.300)
1.1 (0.00379)
1.0 (0.00345)
3.0 (0.0103)
37 .o (0.128)
0 .15 (0. 000517)

F
29.0kg136.0 cm

RLB. 870

>-<

(f1

~
~
>
>
~

tJ

~
>
z

~
>-<

~

>

00

°'""

~

"'

'

~

::0

"""'~

~~

·°'.... ~~ :--·
""::0

~~

{~

c

c

c

{~

'"

8650. 0 (26 .133)
12700.0 (38.369)

2.0 (0.00604)
0. 3 (0. 000906)
14. 6 (0. 0441)
17 .9 (0.0541)---------------

10170.0 (28.729)
17200.0 (48.588)

12250.0 (26.982)
18400.0 (40.529)

4.8 (0.0106)
1. 6 (0. 00352)
220. 0 (0. 485)220.0 (0.485)

13320.0 (25.52)
22070.0 (42.28)

6.3 (0.0121)
0.8 (0.00153)
270.0 (0.517)
300.0 (0.575)

0.4 (0.000766)

5 .3 (0. 0102)

250.0 (0.479)
260. 0 (0. 498)
3. 4*(0. 00651)
300. 0 (0. 575)
350.0 (0.670)
800 .o (1.533)
2600.0 (4.981)
1350. 0*(2. 586)
110. O*(O. 211)205. 0 (0 .452)
235.0 (0.518)
7 .0 (0.0154)
315.0 (0.694)
255. 0 (0. 562)
750 .0 (1.652)
2400. 0 (5. 286)
1150. 0 (2. 533)
135. 0 (0. 297)
150. 0 (0. 330)
145.0 (0.319)
1. 3 (0 . 00286)
1.3 (0.00286)
5.6 (0.0123)
37 .2 (0.0819)
0. 6 (0. 00132)

240.0 (0.678)
170. 0 (0. 480)
3.5 (0.00989)
235. 0 (0 .664)
260.0 (0. 734)
500.0 (1.412)
2050.0 (5.791)
900.0 (2.542)
95. 0 (0. 268)
120.0 (0.339)
115.0 (0.325)
1.6 (0 .00452)
1. 2 (0. 00339)
5.0 (0.0141)
36.0 (0.102)
0.3 (0.000847)
4.1 (0.0116)
3 .5 (0 .00989)
1.2 (0.00339)
1. 4 (0. 00395)

235. Og (0. 710)
170.0 (0.514)
4.5 (0.0136)
160.0 (0.483)
165,0 (0.498)
500.0 (1.511)
2000.0 (6.042)
950.0 (2.870)
100. 0 (0. 302)
137 .0 (0.414)
125. 0 (0. 378)
1. 4 (0. 00423)
6.1 (0.0184)
50.0 (0.151)

F
52.2 kg

171.0 cm

RLB. 803F
45.4kg160.0 cm

RLB. 837M
35.4kg144.5 cm

RLB. 835F
33.1 kg

143.5 cm

RLB. 822* calculated from the value after preservation in 10% formalin solution.
Figures in prenthesis indicate percentages of body weight.

Blubber
Skeletal muscle___ ___

Mammary {l
gland
r

Ovary

Epididymis { ~TestisThyroid
Thymus
Pituitary

AdrenalKidneyStomachIntestine
Liver
Pancreas

Lung

Brain
Heart
SpleenSex
Body weight

Specimen field
numberBoday length

TABLE 1. Continued.

<.C

Nl
Cl

>
M

v

......

>-".]

[/).

;2
z
......

>

t""

>::!
"d

0

>-".]

:::c:

0

~
M
......

~

~

0

270

KAMIYA AND YAMASAKITABLE 2.

BODY LENGTH, BODY WEIGHT AND ORGAN WEIGHTS OF
4 SPECIMENS OF PLATANISTA GANGETICA.

Specimen field
numberBody length

No. 16

No. 18

No. 19No. 20120.5 cm

126.0 cm

122.0 cm

199.0 cm

Sex
Body weightF
17.0kgF
17 .Okg

M
22.5 kg

M
84.0kg47.6 (0. 280)

49.6 (0.220)
1. 7 (0.00756)
114.0 (0.507)
131.0 (0 .582)

210.9 (0 .251)
8.4 (0.010)
700.0 (0.833)
610.0 (0. 726)

300.0 (1.333)
10.2 (0.0453)
26.2 (0. 116)
27.8 (0.124)

1120.0 (1. 333)
34.3 (0.0408)
109.0 (0. 130)101.5 (0.121)
3.6 (0.00429)
3.2 (0.00381)

Brain
Heart
SpleenLung{~

StomachIntestine
Liver
Pancreas
KidneyAdrenal{~{~236.0 g (1.388%)
40.0* (0.235)
3.0* (0.0176)
170.0* (I.OOO)
154. O* (0. 906)
308. O* (1. 812)
460.0* (2. 706)
15.0* (0.0882)
45. O* (0. 265)
42.0* (0.247)

Thyroid
Thymus
Pituitary
Testis

101.8 (0. 599)
100.8 (0. 593)

420.0 (2.471)
30.7 (0.181)
36.2 (0.213)
0.3 (0.00176)
0. 6 (0. 00352)
1. 0 (0. 00588)

0.5 (0.00222)
3.0 (0.0133){~

520.0 (0. 619)
590.0 (0.702)

Epididymis { ~
Ovary

{~

0. 4* (0. 00235)
0. 4* (0. 00235)

0.8 (0.00471)
0.8 (0.00471)

Mammary {1glandr* calculated from the value after preservation in 10% formalin solution.
Figures in parenthesis indicate percentages of body weight.

Sci. Rep. Whales Res. Inst.,
No. 26, 1971

SURFACE TEMPERATURE FIELD IN THE CROZETAND KERGUELEN WHALINGGROUNDSSABURO MACHIDA
Whales Research Institute, Tokyo

ABSTRACT

Some oceanographic conditions in the summer season at the surface in the
Crozet and Kerguelen Ridge regions, where the good whaling grounds ofbaleen whales occur, are discussed on the basis of the distribution of the surface
temperature observed by the Japanese whaling fleets in the 1965/66 to 1972/73
Antarctic seasons.
The surface isotherms bend northwards over the submarine rising aroundthe Prince Edward, Crozet and Kerguelen Islands. These bends of the isotherms suggest to reflect the bending of the surface current, and that it ispresumably influenced by the bottom topography. They may be also suggested that the convergence efficiency of the current is comparatively intense
north and east of these submarine risings.

INTRODUCTION

It is well known that the good whaling grounds of baleen whales occur in the Crozet
and Kerguelen Ridge regions. In these two regions right whales were taken by
the old American whalers mainly in the 19th century and pigmy blue whales werealso taken there in the early 1960's. Recently the Japanese whaling fleets havebeen often searching for the favorite haunts of the sei and fin whales in the regions.
We have little knowledge of the general oceangoraphic conditions in the Crozet
and Kerguelen whaling grounds, though the oceanographic conditions are theclose living evnvironment to the whales. A knowledge of oceanographic conditions
is fundamentally necessary to think systematic study on the environment of thehabits of various marine organisms. From this point of view, therefore, the purposeof the present study is to discuss the oceanographic conditions at the surface in the
Crozet and Kerguelen Ridge regions on the basis of the surface temperature distribution, which was observed by the Japanese whaling fleets.
MATERIAL AND METHOD

The whaling fleets have been supplying us with the data of the oceanographic conditions in the different whaling grounds. They are temperatures observed by anelectric thermometer, of which sensor is fixed to the bottom of a factory ship (ea.
10 m depth) and a scouting boat (ea. 5 m depth). As the surface layer down to a few
Sci. Rep. Whales Res. Inst.,
No. 26, 1974, 271-287

272

MACHIDAten meters in the Antarctic Ocean is roughly homogeneous in temperature, it seems
to be reasonable to consider that there is no difference in the temperatures between
5 and 10 m depth. Therefore, they are taken as same and defined here as the surface temperature.
The surface temperatures were derived from " The survey report of the whaling grounds by a scouting boat" in the 1965/66 to 1972/73 Antarctic seasons and" The weather and oceanographic conditions at the noon position of a factory ship "in the 195 7/58 to 1972/73 Antarctic seasons. A one degree square grid was adopted
in making a monthly chart of the mean surface temperature, and isotherms weredrawn by interpolation.
The Far Seas Fisheries Research Laboratry, Fisheries Agency of Japan kindly
supplied me with the materials for this study.

50

s

0

0

Fig. I. Chart of the Crozet Ridge region showing general bathymetry.
in the 100 fathoms. (After U.S. Chart H.O. Misc. 15, 254-12).

DepthsThe Crozet and Kerguelen Ridge regions are shown with bathymetric contours in Figs. 1 and 2. Although the submarine rising around the Prince Edward
and Crozet Islands is not generally termed the Crozet Ridge (Herdman, Eiseman
and Overy, 1965 ), the Crozet Ridge is named in this study after "Atlas zur Ozeanographie" by Dietrich and Ulrich (1968).
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

CROZETAND KER
GUELE
N もVHALING GROUNDS

60

70

27
3

90E

40

60

s

F
i
g.2. Char
toft
h
eKe
r
gucl
enRidge1
egi
onshowingg
e
n
e
r
al
b
a
t
hymctr
y. De
p
t
h
s
OOfathoms
.(
A
f
t
e
rU.
S.ChartH.O.Misc.15, 254‑1
2
).
i
nt
he J

S
c
i
.Rψ.Wh
a
l
e
sR
e
s.
I
n
s
t.
,
λo
.2
6
,1974

＇

MACHIDA

274

LOCATION OF WHALING GROUNDS
Before discussing the features of the temperature distribution at the surface in the
Crozet and Kerguelen Ridge regions, the features of the catch distribution of the sei
and fin whales, which are the most important baleen whales as well as the minke
whale for the recent whaling industry, is summarized.
In these two regions right whales were abundantly caught by the old American
whalers mainly in the l 9th century, and pigmy blue whales also were bulkly caught
there in the early 1960's. The chart of the catch distribution of the right whale byTownsend (1935) and one of the pigmy blue whale by Ichihara (1966) are very usefull. According to them, the good whaling grounds of the right whale were locatedin the waters adjacent to the Crozet and Kerguelen Islands and ones for the pigmy
blue whale were rather distributed over the Kerguelen and Crozet Ridges. Sei
whales have been abundantly caught in these regions since the 1964/65 Antarctic
season and fin whales have been frequently caught in the north of 60°S since the
195 7/58 Antarctic season. The catch distribution of the sei and fin whales areshown in Figs. 3, 4, 5 and 6.
30

40
1-25
26-50
51-75
76-100
101 -

•

•

•• •·
•

•• ·•
•

SEI

..

•·
••••••••••••••

40.
·•·. . .
••••.
•••••••

050sFig. 3. Distribution of sei whales caught by Japanese Antarctic whaling fleets in
the Crozet Ridge region from the 1965/66 to the 1972/73 seasons. Light shading:
depths less than 1,500 fathoms (about 3,000 m).

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

CROZET AND KERGUELEN WHALING GROUNDS275

The Crozet Ridge Region
Sei whales were caught abundantly in the submarine rising around the Crozet
Islands, though their few catches are distributed widely on the Crozet Ridge. The
good whaling grounds of the sei whale are located in the adjacent waters to the
Crozet Islands. Although in the shallow waters around the Prince Edward Islands
it is somewhat similar in appearance to the Crozet Islands region, catches of sei
whales have been a little less than the former. The fin whale, on the other hand,also distributed widely on the ridge, and a great number of their catches is locatedon the far south-west waters to the Prince Edward Islands.
30

40

•

•••

1-25
26-50
51-75
76 - 100
100-

FIN

40

••
•

•

• ·•·

•••
••
•

••••••••••••••••••••••••••••..........
••

••••

• ••

• •

••

.

. ..

..

••
•• ••

.. ..

0

• ••

••

"

50

s

•• ••••••. . ..

·•·

•• ••

••

Fig. 4. Distribution of fin whales caught by Japanese Antarctic whaling fleets in
the Crozet Ridge region from the 1957/58 to the 1972/73 seasons.

The Kerguelen Ridge Region
The catches of sei and fin whales are widely distributed on the ridge, though
the features of their eatch distribution is to some extent different from one on thesouthern part of the ridge. There are two heavy catches areas of sei whales over the
ridge. It appears that the whaling grounds of the sei and fin whales between 40°
and 45° S are related to the Subtropical Convergence. The fin whales seem to be
distributed dominantly south of about 53° S. These two species of whales have a
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

276

MACHIDA

50

60

sFig. 5. Distribution of sei whales caught by Japanese Antarctic whaling fleets in
the Kerguelen Ridge region from the 1965/66 to the 1972/73 seasons. Light shading: depths less than 1,500 fathoms (about 3,000 m).

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

277

CROZET AND KERGUELEN WHALING GROUNDS

•

•

50

•
••••••.......•• ..
•• • • • • •

..
••

•
'

• •••
•• •

•

••
•

...

•

•

• 60

•••• s

•

••
• ••
•

•

••

•

•

••
Fig. 6. Distribution of fin whales caught by Japanese Antarctic whaling fleets in
the Kerguelen Ridge region from the 1957/58 to the 1972/73 seasons.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

MACHIDA

278

strong tendency to be distributed on to the eastern slope of the ridge and a few ones
have been caught on to the western slope of it, except in the higher latitudes southof about 56° S, where the fin whales are widely distributed from west to east of theridge.
The different features of the catch distribution of the sei and fin whales as mentioned above may be partly caused by the difference of their foods and habitat segregation. In the Subantarctic regions of these two whaling grounds, the quantitatively important food organisms of the sei whale is Parathemisto gandichaudii, andEuphausia vallentini is important as a favorite food of the fin whale (Nemoto, 1959,
1962, 1970; Nasu, 1966; Kawamura, 1970). I do not intend to mention furthera pattern of their catch distribution, because it is not the main purpose of the present study.
SURFACE OCEANOGRAPHIC CONDITIONS
Figs. 7-21 show the distribution of the surface temperature in the 1957/58 to 1972/
73 Antarctic whaling seasons. Some oceanographic conditions in the Crozet and
Kerguelen Ridge regions are discussed on the basis of these distribution of the surface isotherms.

50sFig. 7.

Surface temperature (°C) in December 1968.

The Crozet Ridge Region
The distibution of th emonthly mean surface temperature in this region are
shown in Figs. 7-14. The isotherms are remarkably bending, which is conspicuousin the submarine rising region around the Crozet Islands and less conspicuous in
the Prince Edward Islands than the former, namely northward on the rising andSci. Rep. Whales Res. Inst.,
No. 26, 1974

CROZET AND KERGUELEN WHALING GROUNDS

279

Jan

1968

Jan

1969

40

50

50

s

Fig. 8. Surface temperature (°C) in
January 1968.

40sFig. 9. Surface temperature (0 C) in
January 1969.

Feb

1967

40

50

s

Fig. 10.

Surface temperature (0 C) in February 1967.

southward on the west and the east sides of it, with some irregularities. Such tendency of the isothermal pattern is especially distinct in the Crozet Islands region,
where data are more abundant than in elsewhere. In the Prince Edward Islands
region, however, the similar bend are not so clear as in that region in a certain
months, perhaps owing to the lack of data.
The bend of isotherms in the adjacent waters to the Crozet Islands in winterSci. Rep. Whales Res. Inst.,
No. 26, 1974

MACHIDA

280

Feb
1968

40

6
50

s

Fig. 11.

30

Surface temperature (°C) in February 1968.

40
Fig. 12.

50

GOE

0

Surface temperature ( C) in February 1969.

have been already shown by Darbyshire (1964), Visser and Niekerk (1965), Orren(1966) and Nel (1968). By these charts, therefore, it appears that such feature of
the surface isotherms to be a permanent one. A steep temperature gradient still
occurs in the adjacent waters to south of the Subtropical Convergence. Its oceanographic conditions seem to intencify an effect of the convergent movement in accompany with the Subtropical Convergence, lying about 42° S in the South West
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

CROZET AND KERGUELEN WHALING GROUNDS

281

Feb
1970

40

50

s

Fig. 13.

Surface temperature (0 C) in February 1970.

Mar
1966

40

.

8

50

s

Fig. 14.

Surface temperature (°C) in March 1966.

Indian Ocean (Deacon, 1937a; Orren, 1966). It also seems that the Subtropical
Convergence bends soutwards on the eastern side of the Crozet Islands, presumably
in approximately 60° E. The Subtropical Convergence by Deacon (1937a) also
meanders southwards in approximately 60° E.
The Antarctic Convergence, which is one of the major features in the Antarctic
Ocean, seems to run across the submarine rising around the Crozet Islands in DeSci. Rep. Whales Res. Inst.,
No. 26, 1974

282

MACHIDA

cember 1968, considering the location of the 4°C isotherm at the surface, which isone of the valid indication of the Antarctc Convergence (Deacon, 1937a; Mackintosh, 1946; Houtman, 1968). The 4°C isotherm, however, does not lie on the
Crozet Ridge in January, February and March. The greater parts of the Crozet
Ridge region, therefore, seems to be usually between the Subtropical and Antarctic
Convergences, and so this region is occupied by the major Subantarctic Surface
Water.
It is well known that the temperature distribution well reflects the feature of
the current. If we accept this general view, the current deflects to the left (north)on approaching a submarine rising around the Prince Edward and the Crozet Islands, and after having passed the rising it deflects to the right (south). Such current deflection over the submarine rising seems to be variable probably under the
influence of the bottom topography.
These findings support the view by Darbyshire (1964) and by Visser and Niekerk (1965), who described the current deflection to the left over the submarine rising around the Crozet Islands and the influence of the bottom topography on theocean current. Orren (1966) also indicated a northward flow of the cold Subantarctic Surface Water in the Crozet Islands region, probably occasioned by a northward movement of the Antarctic Convergence south of that islands.

The Kerguelen Ridge Region
Figs. 15-21 show the distribution of the monthly mean surface temperature inthis region. It is clear that the isotherms are bending in a similar way as in the
Crozet Ridge region, namely with a northward bend over the ridge and a southward
one on the east side of it. The 4°C isotherm lies near the 50° S parallel across theridge with bending from the west to the east. Furthermore after passing the ridge
the Antarctic Convergence bends down to about 55°S in approximately 90°E. Its
position roughly coincides with the convergence by Deacon (1937a) or by Mackintosh (1946). In addtion to this convergence, a sharp gradient in the surface temperature occurs on the north slope of the ridge.
The distriburion of the montly mean surface temperature suggests that thecurrent deflects to the left (north) on approaching the Kerguelen Ridge and after
having passed the ridge it bends to right (south). These deflection of the surface
current in the ridge region seems to be probably influenced by the bottom topography
and to be variable as well as in the Crozet Ridge region.
Deacon (1973a, b) and Sverdrup (1942) described the current bends to thenorth and to the south on passing over the Kerguelen Ridge, and that the current
deflection is probably under the influence of the bottom topography.
The deflection for a current on passing over the rising in the bottom topography may be anticipated on the theoritical grounds-in the southern hemisphere acurrent will deflect to the left as the sounding decreases and to the right as it increase(Deacon, 1937a, b; Sverdrup, 1941; Neuman, 1960), and in the case of eastern
flowing is the West Wind Drift a northward movement is expected. These features
are actually observed in many ridge regions, besides these two, in the Antarctic
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

CROZET AND KERGUELEN WHALING GROUNDS

60

70

80

283

90E

Dec
1969

40

Fig. 15. Surface
temperature (°C)
in December 1969.

50

s

Jan
1968

4
50

Fig. 16. Surface
temperature (°C)
in January 1968.

60sSci. Rep. Whales Res. Inst.,
No. 26, 1974

284

MACHIDA

6~0~~~-.--~~-;7r0~~~-.-~~--"8~0~~~-.-~~~90E
Jan

1969

• 6
50

Fig. 17. Surface
temperature (°C)
in January 1969.

60

s

Feb

1967

50

Fig. 18. Surface
temperature (°C)
in February 1967.

2

60

s

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

CROZET AND KERGUELEN WHALING GROUNDS

285

Feb
1968

50

Fig. 19. Surface
temperature (°C)
in February 1968.

60
5

60

70
Feb
1969

40

50

s

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

Fig. 20. Surface
temperature (°C)
in February 1969.

286

MACHIDA

Mar

1968

50

4

·~4

60

s

Fig. 21.

Surface temperature (°C) in March 1968.

Ocean (Deacon, 1937a, b; Sverdrup et al., 1942; Midttun and Natvig, 1957; Burling,
1961; Harris, 1970) and they support the theory.
ACKNOWLEDGEMENTS
I wish to express my thanks to Dr. Keiji Nasu of the Far Seas Fisheries Laboratory,
Fisheries Agency ofJapan and Professor Michitaka U da of the Department of Marine
Science and Technology, Tokai University for suggesting this study. Thanks arealso due to Dr. Ichiro Yamanaka of the Far Seas Fisheries Laboratory, Fisheries
Agency ofJapan for some valuable suggestions and for reading this manuscript.
REFERENCESBURLING, R. vV., 1961. Hydrology of circumpolar waters south of New Zealand. N.:(. Dep. sci. industr.
Res. Bull., 149 (N.<:,. Oceanogr. Inst. Mem., 10), 66 pp.
DEACON, G. E. R., 1937a. The hydrology of the Southern Ocean. Discovery Rep., 15: 1-124.
DEACON, G. E. R., 1937b. Note on the dynamics of the Southern Ocean. Discovery Rep., 15: 125-152.
DARBYSHIER, ]., 1964. A hydrological investigation of the Agulhas Current area. Deep-Sea Res., 11:781-815.
DIETRICH, G. and ULRICH, J., 1968. Atlas zur ozeanograhies. Bibliographisches lnstitut LG Mannhim,
76 pp.
Sci. Rep. Whales Res. Inst.,

No. 26, 1974

287

CROZET AND KERGUELEN WHALING GROUNDSHERDMAN, H. F. P., EISEMAN, J. D. H. and OVERY, C. D., 1965. Proposed names of features on the deepsea floor. Deep-Sea Res., 3: 253-261.
HARRIS, T. F. vV., 1970. Planetary-type waves in the South West Indian Ocean. Nature, 227: 1043-1044.
HOUTMAN, TH. J., 1964. Surface temperature gradients at the Antarctic Convergence. N.z.J. Geol. Geophys.,

7: 245-270.
!CHIHARA, T., 1966. The pygmy blue whale, Balaenoptera musculus brevicauda, a new subspecies from theAntarctic. In Whales, Dolphins and Porpoises (Ed. K.S. Norris, Univ. Calif. Press), 79-113.
KAWAMURA, A., 1970. Food of sei whale taken by Japanese whaling Expeditions in the Antarctic season
1967/68. Sci. Rep. Whales Res. Inst., 22: 127-152.
l'viACKINTOSH, N. A., 1946. The Antarctic Convergence and the distribution of surface temperatures in
Antarctic Waters. Discovery Rep., 23: 1-179.
NAsu, K., 1966. Fishery oceanographic study on the baleen whaling grounds. Sci. Rep. Whales Res. Inst.,

20: 157-210.
NEL, E. A., 1968.

The microplankton of the South-East Indian Ocean. Investl Rep. Div. Sea. Fish. S. Afr.,
62: 1-178.
NEMOTO, T., 1959. Foods of baleen whales with reference to whale movements. Sci. Rep. Whales Res. Inst.,
14: 149-290.
NEMOTO, T., 1962. Food of baleen whales collected in recent Japanese whaling expeditions. Sci. Rep.
Whales Res. Inst., 16: 89-103.
NEMOTO, T. and Yoo, K. I., 1970. An amphipod, Parathemisto gaudichaudii as a food of the Antarctic sei
whale. Sci. Rep. Whales Res. Inst., 22: 153-158.
NEUMAN, G., 1960. On the effect of bottom topography on ocean currents. Deut. Hydrograph.
13:132-141.
ORREN, M.J., 1966. Hydrology of the South West Indian Ocean. Invest[ Rep. Div. Sea Fish. S. Afr., 55:
132-141.
SvERDRUP, H. U., 1941. The influence of bottom topography on ocean currents. Appl. Mechanics. Th.
Karman Ann. Vol., 66-75.
SVERDRUP, H. U., JoHNSoN, M. W. and FLEMING, R.H., 1942. The Oceans. Prentice-Hall, Inc., 1987 pp.
TOWNSEND, C. H., 1935. The distribution of certain whales as shwon by logbook records of American whaleships. Zoologica, 19: 1-50.
VISSER, G. L. and VAN NIEKERK, M. M., 1965. Ocean currents and water masses at 1,000, 1,500 and 3,000
meters in the South-West Indian Ocean. Investl Rep. Div. Sea Fish. S. Afr., 52: 1-46.

z.,

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

THE VOYAGE OF THE KONAN MARU NO. 16 TO
THE ANTARCTIC WHALING GROUNDSSABURO MACHIDA
Whales Research Institute, Tokyo

ABSTRACT

Three major Japanese whaling companies, the Kyokuyo, the Nippon
Suisan and the Taiyo Gyogyo Co. Ltds., made the joint observation on the
distribution and abundance of whales by the whale catcher Konan Maru No.
16 in the Australian and New Zealand sector of the Antarctic Ocean fromJanuary 10 to March 8, 1973.
The number of whales sighted in about eight weeks and on the passageof 9,377 nautical miles was not great. We saw only 20 fin, 16 sei and 7
humpback whales. The blue and right whales was not encountered at all.
The minke and sperm whales sighted are rather great; the former is 251 andthe latter 108. 5 fin, 2 sei, 2 humpback and 8 sperm whales were effectively
marked.
Oceanic observations at the surface were also worked during the voyage.
The locations of the Subtropical and Antarctic Convergences and the Australasian Subantarctic Front on four traverse courses across the Antarctic
Ocean are determined by the steep meridional gradient in the surface temperature and salinity. The distibution of the pack-ice, icebergs and patchof the krill at the surface are also shown.
INTRODUCTION

In order to contribute to the stock assessment of whales in the Antarctic Ocean, themajor whaling companies, the Kyokuyo, the Nippon Suisan and the Taiyo Gyogyo
Co. Ltds., made the joint observation on the distribution and abundance of whales
by the whale catcher Kanan Maru No. 16 in the Australian and New Zealand sector of the Antarctic Ocean from January 10 to March 8, 1973. The principal purpose of the voyage was: 1) to obtain the latest information on the distribution andabundance of whales in that area; 2) to mark as many whales as possible; 3) to observe some oceanic conditions at the surface. In those days Japanese whaling fleets
were not operating in high latitudes south of Australia and New Zealand. We,
therefore, have little information on the distribution and abundance of whales andon some oceanic conditions <1;t the surface in the region, in which a great number ofthe blue, humpaback and fin whales had been taken in the early Antarctic whalingage.
The Kanan Maru No. 16, belonging to the Nippon Suisan Co. Ltd., has a gross
tonnage of 739.82, a disel engine of 3,280 HP, a cruising speed of 13. 75 knots.
The watcher for whales on the whale cathcer consited ofT., Yamada, Captain
Sci. Rep. Whales Res. Inst.,
No. 26, 1974, 289-302

MACHIDA

290

150

170

160

180

'· '>v~£,.,,,oo""'X~'"''

~~~~~

10.l

11.l

.II

'

...

12J

BALLE NYISLANDS '

150

160

170

180

Fig. 1. VoyageoftheKonanMaruNo.16
the first period from January 10 to Febmajor species sighted, observed edge ofencountered on the traverse courses,

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

VOYAGE OF THE KONAN MARU NO. 16

Observed edge of the pack-ice
Northen limit of the observed iceberg
Range of the krill patch observed at the surface.I!

- 3.1!

2.Il

in the Antarctic whaling grounds during
ruary 6, 1973. Ship's track, whales ofthe pack-ice, northern limit of icebergs
and range of the krill patch observed.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

. 291

292

MACHIDA

4.lll

3.fil

2.Ill

110E

120

130

140

150

Fig. 2. VoyageoftheKonanMaruNo.16
the second period from February 8 tomajor species sighted, northern limit ofcourses and range of the krill patch

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

VOYAGE OF THE KONAN MARU NO. 16

VT

ASMAN JA

'

10ll

11.11

@-12.11in the Antarctic whaling grounds during
March 8, 1973. Ship's track, whales oficebergs encountered on the traverse
observed.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

293

294

MACHIDAand Leader of the sighting observation; H., Kano (Captain of a whale catcher ofthe Kyokuyo Co. Ltd.); S., Isobe (Chief Officer of a whale catcher of the Taiyo
Gyogyo Co. Ltd.); the officers and crew of the ship. They have excellent experiencein whaling more than twenty years. I get on board the ship in order to make someoceanic observations at the surface in the Australian and New Zealand sector of the
Antarctic Ocean.
A continuous sighting for whales was usually maintained on the cross net (twowatchers) and on the upper bridge (three ones) from dawn untill dusk every day,except on when visibility is poor and heavy seas greatly disturb our sighting observation. We, therefore, can look out over the horizon as far as 6 to 7 nautical miles
from the cross net in good visibility. On all nights in higher latitudes than about
60° S except on when the weather or schedule gave us reason to steam, we lay stopped to avoid missing whales in the hours of darkness. For the same reason we
steamed slow speed in heavy rain, fog and snow; when the weather was very thick
we would stop untill it cleared.
WHALES SIGHTED AND MARKED

The voyage of seeking after whales by the Kanan Maru No. 16 consisted of two periods in the Australian and New Zealand sector of the Antarctic Ocean from January
to March, 1973. The first period was occupied on the passage from Hobart to Wellington between January 9 and February 6 (Fig. 1). In the second period the whalesighting was occupied on the course from Wellington to Freemantle during February
8 and March 8 (Fig. 2). There is no need to describe in detail the whole of about
eight weeks occupied in sighting for whales, but reference should be made to the
ship's track, location of major whales encountered, distribution of observed edge ofthe pack-ice and some oceanic conditions at the surface in Figs. 1-6, and in Tables 1
and 2. In general it may be said that the Kanan Maru No. 16 steered easterly
courses in the first period and westerly ones in the second period by passing throughthe grounds in which favorite haunts and dense local concentrations of the blue,
fin and humpback whales had been located in the early Antarctic whaling age.
As is given in Tables 1 and 2, and Figs. 1 and 2, major whales sighted in the two
periods are not as great as we had hoped, except the minke and sperm whales. We
could not saw the blue and right whale at all, and fin whales encountered was 20 inabout two months. I wonder whether the very few numbers of the fin sighted arereflected in the size of their stocks in the Australian and New Zealand sector of the
Antarctic Ocean? 19 among 20 fins were distributed in the South Pacific Antarctic Ridge region.
Although we observed on the grounds in which most humpback whales had
been taken by early pelagic expeditions, only 7 individuals were encountered there.
Two humpabacks sighted in 60°53'S, l l6°30'E on February 28 were adult and calf.
It may be said the stock of the southern humpback groups IV and V does not recovered yet well.
We observed 16 sei whales, 8 of which were distributed in the Subtropical
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

VOYAGE OF THE KONAN MARU NO. 16

295

TABLE I. VOYAGE OF THE KONAN MARN NO 16 TO THE AUSTRALIAN AND NEWZEALAND SECTOR OF THE ANTARCTIC OCEAN. WHALES SIGHTED
AND WHALES MARKED EACH DAY.
Sighted
~

Date

10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
2s
29
30
31

I

Noon

46°29 1 S
50°35 1 S
55°31 1 S
6l 0 0l'S
64°05 1 S
63°401 S
6l 0 42 1 S
60°42 1 S
62°5l'S
65°58 1S
63°53'S
64°49 1 S
65°20 1 s
66°46 1S
66°ll'S64°18 1 S

66°00 1S

5
6

64°391 S
63°481862°27 1S
60°43 1S
58°181S
55°57 1S
53°571 S
52°261 S
50°38'8
47°21 1 S
43°341 S

27

working days

8
9
10
11
12
13
14
15
16
17
18
19
20

4l 0 361 S
46°16'S50°44 1 S
53°47 1 S
57°261 S
62°16'S66°36 1 S
67°46 1 S
66°101 S
65°42 1S
64°53 1S
63°31 1S
62°42 1 S

II

2
3
4

Position

147°47 1 E
147°541 E
147°561 E
149°25 1 E
149°25 1 E
152°41 1 E
154°43 1 E
158°11 1 E
162°52 1 E
164°38' E
170'26 1 E
176°401 E
1n°54 1l 75°12 1 W
171°23'W
164°401 W
158°24 1 W
157°261 W
155°351 w
158°47 1 W
163°27 1 W
167°l81 W
l 70°43 1 W
l73°32 1 W
176°11 1 W
179°20' E
176°13 1 E
175°27 1 E

w

Distances Hours(naut. (h.m.)mile)
143 15 30
188 16 00
207 , 16 40
238 16 20
160 16 00
168 17 20
180 16 35
207 16 55
203 17 30
205 16 50
195 16 30
211 17 05
183 15 20
183 16 50
207 15 40
228 15 55
205 17 15121 10221 17 00
211 16 55
201 16 15
196 16 45
205 16 40
116 15 50
no sighting
160 12 50
197 14 40
183 14 35

Sea
condition (1)Visibility(2)

112 800
148 14 20
154 14 15
no sighting
159 15 10
201 15 10
182 15 40
194 15 40
195 16 00
155 11 20
93 14 00
163 15 30
174 14 35

Whales marked~--~---~

~

ci.

"

§ ..,

~

Bad
Good
Bad
Moderate
Good
Moderate
Moderate Bad
Bad
Bad
Moderate Bad
Moderate Good
Bad
Good
Bad
Good
Moderate Moderate
Bad
Good
Moderate Good
Moderate Good
Good
Good
Good
Good
Moderate Good
Moderate GoodGood
Bad
Moderate Good
Moderate Good
Moderate Good
Moderate Moderate
Bad
Bad
Bad
Good

rn

~

§
& c

ci.

Good
Good
Good
Good
Moderate
Good
Moderate
Good
Good

2

3
8
5

5
3

3

5

2

2

2

9
11

6

3

7
8
5
7
5

5
2

5
3
3

I

4

7

2

2

3

4*
17

3 12+4* 84

2

4
7
5
1

26

5

2

l

4

24
Continued ...

Sci. Rep. Whales Res. Inst.,
No. 26, 1974&,,;rn~~JSrn

Moderate Good
Moderate Good
Bad
Bad
Bad
Moderate
Moderate
Moderate
Bad
Moderate
Bad
Bad
Moderate

8

§ ·-

4

Moderate Bad
Moderate Good
Moderate Good

Total 5,013 422 55
174°44'E
172°121 E
171°36' E
169°29 1 E
168°52 1 E
169°541 E
172°21 1 E
167°221 E
163°15 1 E
157°33 1 E
155°33 1 E
151°00 1 E
147°2 l' E

Major species of whales
sighted

2

2

296

MACHIDATABLE I.

Continued.

Sighted
~

Date

Noon

7
8

64°24 1 S
64°17 1 S
64°20 1S
64°34 1 S
63°56 1S
63°57 1S
63°55 1S
6l 0 45 1S
58°581 S
55°00 1S
52°l 71S
47°36 1S
43°20'S39°52 1s
36°23 1S
33°23 1S

27

working days

21
22
23
24
25
26
27
28
1 III
2
3
4
5
6

Position

Distances Hours(naut. (h.m.)mile)

143°07 1 E
139°06 1 E
137°45 1 E
136°36 1 E
133°22 1 E
126°57 1 E
121°21 1 E
116°59 1 E
115°10 1 E
114°51 1 E
l15°14 1 E
114°541 E
114°54 1 E
115°06 1 E
115°02 1 E
114°40 1 E

147 12 15
108 930
no sighting
192 14 30
189 14 35
206 14 35
199 15 05
195 14 00
177 13 45
107 10 15
166 13 00
177 12 30
173 12 20
159 12 50
168 14 3571
600

Major species of whales
sightedSea
condition (1)Visibility
(2)

~

ci.

.s

IJ;,,

8;:j
::r::

4.l

·.i
if)

Bad
Moderate
Moderate Bad

ci.

."I

8....

::s

0.

.s

4.l

if)

.s

IJ;,,

8;:j
::r::

8....
·.i
if)

4.l

0.

if)

13
24
67

Maderate Good
Moderate Good
Good
Good
Bad
Good
Bad
Good
Bad
Good
Bad
Good
Bad
Good
Moderate Bad
Moderate Good
Moderate Good
Good
Good
Good
Good

4

2

8 24

2

2
4
3

5
43
167

Total 4,364 359 25

3

4

54 working days Sum Total 9,377 782 20

20

712+4*251 108(1), (2) mean value of 06, 08, 10, 12, 14, 16, 18 ships time.
(1) 0-2 Good, 3-5 Moderate, 6- Bad.
-6 Good, 5-3 Moderate, 2- Bad.
(2)
TABLE 2.

Whales marked

6

82

6

5

2

2

8

* Probably Bryde's whale.

WHALES ESTIMATED TO HAVE BEEN EFFECTIVELY MARKED.

Species
Whales sighted
Schools encountered
Whales marked effectively
Marking
Hit
Hit-mark protruding
Possible hit
No verdict
Richochet
Miss
Total

Fin

Hump.

Sei

Minke

Sperm

Total

20

12+4*
6+3*
2

251
158

5

7
3
2

108
76
8

402
252
16

7

4

4

9

24

2
2
1
7
21

2
4
2
18
50

6

2
5
15

1
5

2
6

3
3

* Probably Bryde's whale.
Convergence regions, just south of Tasmania and east waters to New Zealand.
However, at the begining of March not one sei whale were encountered in the convergence region of the South East Indian Ocean, where most sei whales have been
recently taken by Japanese whaling expeditions between December and earlyFebruary. It is conceivable that 4 sei whales encountered in the east water to New
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

VOYAGE OF THE KONAN MARU NO. 16

297

Zealand were Bryde's whales, judging from their swimming behaviours. They werelocated over the Mernoo Bank on the Chatham Rise. 7 among other 8 sei whales
were distributed in the South Pacific Antarctic Ridge region. That more sei whales
were not encountered was likely to due to the possibility that sighting areas was nottheir major feeding grounds or that we may had been early in the season for themmigrating into high latitudes.
The minke whale were encountered in every part of high latitudes south of
the Antarctic Convergence compared to the distribution of other baleen whales,
and we sighted up to 251 after all. It seems that the great number of the minke
whale encountered indicates the large population of the species well.
The number of the sperm whale observed is also rather great. Most of them,
except those encountered south of Cape of Leeuwin in South West Australia, were
solitary bulls. It seemed that sperm whales sighted south of Cape Leeuwin weremain herds, which were distributed on the continental slope. It will be noted that
distinct concentration of solitary bulls (24) were lacated between 126° and 128° E
on about 64° S.
The whale marks and marking guns were provided us by the Far Seas Fisheries
Laboratory, Japanese Fisheries Agency. We used the marks of the International
Whale Marking Programe and some of Japanese Fisheries Agency. Tables 1and2
show the whales marked during the cruise. We intended have marked as many
whales sighted as possible. We were oblidged not to waste much marking time
because the time and distance for whale sighting were to be extended.
OCEANIC OBSERVATIONS AT THE SURFACE

Locations of Some Major Oceanic Fronts
Some conspicuous oceanic features of the Antarctic Ocean are the Subtropical andAntarctic Convergences. There has been proposed another oceanic front, whichis named the Australasian Subantarctic Front, existing south of the East Indian
Ocean, the Australian Continent and the Tasman Sea (Burling, 1961). In thisreport the location of these oceanic fronts are determined from the steep mridional
gradient of the surface salinity and temperature, with refering to some previous
works.
Course I: Oceanic observations were made between 44° and 64° Sin approximate longitude 148° E from January 9 to 14. The sea surface salinity and temperature along this traverse course have been plotted in Fig. 3. Between 45° and
46° S salinity decrease from 35.2 to 34.8°/00 and temperature falls off from 14° to 11°C.
These conditions seem to show evidently the Subtropical Convergence region locating south of Tasmania.
A great increase and decrease in temperature and salinity occurred repeatedly
between 50° and 53° S. In the region salinity fluctuates from 34.6 to 34.l°loo andtemperature varies between 9.5° and 7°C. A character of the Australasian Subantarctic Front is sufficently met with their sharp gradients. As the steep meridional
gradient occurred three times, it seems possible, therefore, that the front meandered
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

MACHIDA

298

in the counter-S shape.
Between 53.5° and 55.5° S the surface temperature decrease sharply from 7° to
l.5°C. There is also sharp change in salinity from 34.1 to 33.80fo 0 in this zone.
These oceanic conditions seem to indicate clearly the Antarctic Convergence.
Course II: Fig. 4 shows a latitudinal change of salinity and temperature at
the surface along the traverse course, observed between 42° and 62° S during January
20

oc

~

120E140 160 180 160W
30
40

:J

~

35
°loo

.~

50
60

E

5
70

~~10
c
7il

(/)

34

5
0

55

50

45

60

65°5

LatitudeFig. 3. Surface temperature and salinity along the traverse coune I in approximately !48°E (January 10-14, 1973).

~
:J

20

·c

-ru

120E140 160 180

50

35
°loo

L..

<!>

a.

E

160~~

60

5
70

~b10
c
7il
(/) 34

0
45

50

55

60°5

LatitudeFig. 4. Surface temperature and salinity along the traverse course II (January 29February 6, 1973).

29 to February 6. The convergence region in the eastern waters to New Zealand isgenerally shown by about from 35.0 to 34.50fo 0 and by about from 13° to 16°C in summer (Deacon, 1937; Garner, 1954, 1959). These oceanic parameters were clearly
distributed between about 42° and 44.5° S, and the gradient in salinity and temperature are considerably sharp between about 42° and 44.5° S and so it may be conSci. Rep. Whales Res. Inst.,
No. 26, 1974

299

VOYAGE OF THE KONAN MARU NO. 16

eluded that the Subtropical Convergence region present between 42° and 44.5° S.
A sudden increase in salinity near 43° 15' S seems to suggest the curvature of theconvergence and the southward tangue-shaped extension of the Subtropical Water.
Temperature fall off from about 4° to 2°C and salinity also decrease from about
33.9 to 33. 7%0 between 60° 45' and 61° 30' S. These conditions met sufficently
with characters of the Antarctic Convergence.
Course III: The observation of the surface salinity and temperature weremade between 43° and 67° S from February 8 to 14. The meridional change of thesurface salinity and temperature along this traverse section are given in Fig. 5.
As already mentioned in the Course II, the Subtropical Convergence region
in the eastern waters to New Zealand is generally defined with salinity 35.0 to 34.5% 0
and temperature 13° to l6°C in summer. These oceanic conditions are sufficiently
presented in the region between 43° and 45° S, where steep meridional gradients insalinity and temperature occur.

20

oc

~
:J

iii
......
<IJ

n.
E
~ +-'
>.10

c
Cii
l/)

34

0
45

50

55

60

65°5
LatitudeFig. 5. Surface temperature and salinity along the traverse course III in approximately 170°E (February 8-14, 1973).

The sharp salinity increase in the Subtropical Convergence region seems thatits water mass belongs to the Southland Current system. The current, which is abranch of the Tasman Current having characters of the Subtropical Water, passes
through the Fouevaux Channel from the Tasman Sea, flows northward along thecoast of the South Island and extends to off Banks Peninsula in the latitude about
44° S (Brodie, 1960; Garner, 1961).
It seems possible that the steep meridional gradient in salinity and temperature
between 55° and 57.5° S show an oceanic front and a curvature of the West Wind
Drift. The Subantarctic Slope of the Campbell Plateau locates just between 55°
and 56° S on this traverse course. The sounding variation could have influenceon the current.
The surface temperature falls sharply off from 6.5° to 4°C between 59° and
60° S and salinity also decrese sharply in the region. These steep gradient suggest
Sci. Rep. Whales Res. Inst.
No. 26, 1974

MACHIDA

300

evidently the Antarctic Convergence.
Course IV: Fig. 6 shows the meridional variation of the surface salinity andtemperature along this traverse course, observed for the period from February 8 toMarch 8.
It is every difficult to define the Subtropical and Antarctic Convergence regions
on account of irregular temperature and salinity changes. The salinity variation
between about 35° and 40° S, where the location of the Subtropical Convergenceregion is expected, do not give a simple steep gradient but repeats a sharp decrease
and increase. However, a more steep gradient of temperature occurs between
39.5° and 40.5° S, with a sharp salinity gradient. It is quite possible that these steep
gradient in the region indicate the Subtropical Convergence region. As the temperature change from 17.5° to l4°C and salinity fluctuate between 35.6 and 34.9%0
in that region, these conditions support that estimation.
36

(lJ
1-

~

I-

120E140 160 180

·1••

::J

~

160'!~
50

20

60

•c

s

E
~zi 35
c

70

~10
34
0

35

40

45

50

55

6d'S

LatitudeFig. 6. Surface temperature and salinity along the traverse course IV in approximately l 15°E (February 27-March 8, 1973).

Going north from the Antarctic Continent the surface temperature increases
slowly untill the region between 50° and 49° S is reached where the relatively rapid
increase of some 2°C occurs. Although the rapid increase in temperature and salinity suggests the Antarctic Convergence, the temperature 5° to 7°C in the zone seems
to be relatively higher than ones of the convergence defined by previous works(Deacon, 1937; Mackintosh, 1964; Houtman, 1968). The high temperature may
be partly caused by rare heating by the solar radiation. It may be defined herethat the Anarctic Convergence existed between 50° and 49° S on this traverse cource.
The salinity change sharply from 34. 7 to 34.2%0 between about 44.5° and 46° S
south of the Subtropical Convergence. The center of the steep salinity gradient
range is about 34.5% 0 and locates at 45° S. The surface temperature range in thezone, however, is higher than that which is an indication of the Australasian Su banSci. Rep. Whales Res. Inst.,
No. 26, 1974

VOYAGE OF THE KONAN MARU NO. 16

301

tarctic Front. The reason may be partly caused by unusual heating of the solar
radiation as well as in the Antarctic Convergence region. The Australasian Subantarctic Front, therefore, is defined here to be located between 44.5° and 46° S.

Distribution of Pack-Ice, Icebergs and Patch of Krill
The information on the distribution of the Antarctic sea ice will be some help to thestudy of oceanic problems in the Antarctic Ocean. Although the available observation in old times are quite inadequete for a detailed account of the distribution
and movements of the pack-ice and icebergs as a whole, there are some publishedworks on the distribution of the pack-ice edge; papers by Hansen (1934) and Mackintosh and Herdman (1940) were vased on whaling factory ships and oceanograraphical research vesseles. Recent ones, however, have been established on photographs from satellites (Prehoehl, 1966; Sissalia et al., 1972).
Records on the observed position of the northern limits of the pack-ice andicebergs at differnt times during the cruise are plotted in Figs. 1 and 2.
The observed pack-ice was the very close one and the melting drift ice. Thevery close pack-ice was encountered only in the vicinity of 64° S, 150° Eon January
14 and 15. The melting drift-ice, on the other hand, were observed at different
places.
As it is wellknown that icebergs are located up to about 60° S south of Australia
and New Zealand, the northern limit of the distribution on icebergs are shown on
only for traverse course across the Antarctic Ocean (Figs. 1 and 2). On the Course
I a typical tabular iceberg was first encountered in 56° 02' S, 148° 13' E on
January 12. The last iceberg observed on the traverse course II was in 62° 30' S,
157° 00' E south of the Antarctic Convergence on January 29. It was very large
and typical tabular iceberg. On the Course III from New Zealand to the Balleny
Islands an iceberg was sighted in 63° 50' S, 171° 00' E fruther south of the Antarctic Convergence on February 13. The northern limit of the distribution of iceberg
on the traverse Course IV was in 60° 30 'S, 116° 20' Eon March 2, further south of
the Antarctic Convergence.
As mentioned above, it seems that icebergs were not distributed across the
Antarctic Convergence in the Australian and New Zeland sector between January
and March, 1973.
The Antarctic krill, mainly Euphausia superba, have been recently regarded as
the latent fishery resources, since its standing crop is vast. Its recources has been
hoped for food ones as the world population has been gradually increasing.
The krill is often found in very dense concentrations at the surface. They
are called patch and swarm. In this report the geographical distribution of the krill
patch at the surface is shown (Figs. 1 and 2), but relationship between it and theoceanic conditions will be discussed in another report.
Patches of the krill were roughly distributed south of 63 ° S between 148° E and155° W. In the region they were distributed in temperatures less than 2°C, which
retains characters of the Anarctic Winter Water, and most of them were encountered in temperatures between -0.5° and l.5°C.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

302

MACHIDAACKNOWLEDGEMENTS

I am greatly indebted to Captain and chief investigator Tatsumi Yamada, his crewof the Konan Maru No. 16, Mr. Hayato Kano of the Kyokuyo Co. Ltd. and Mr.
Sadao Isobe of the Taiyo Gyogyo Co. Ltd. for observing on whales and oceanic
conditions.
REFERENCES
BRoDrn,J. vV., 1960. Coastal surface currents around New Zealand. N. -<:,. J. Geol. Geophys., 3(2): 235-252.
BURLING, R. vV., 1961. Hydrology of circumpolar waters south of New Zealand. N. -<:,. Dep. sci. industr.
Res. Bull. 149 (N. -<:,. oceanogr. Ins. Mem. 10), 66pp.
DEACON, G. E. R., 1937. The hydrology of the southern ocean. Discovery Rep., 15: 1-124.
GARNER, D. M., 1954. Sea surface temperature in the Southwest Pacific Ocean from 1949 to 1952. N. -<:,. J.
Sci. Tech. Bull., 36(3): 285-303.
GARNER, D. l\!I., 1969. The Subtropical Convergence in New Zealand surface waters. N. -<:,.]. Geol.,2(2): 315-337.
GARNER, D. M., 1961. Hydrology of New Zealand coastal waters, 1955. N. -<:,. Dep. sci. industr. Res. Bull.
138 (N. -<:,. oceanogr. Ins. Mem. 8), 85pp.
HANSEN, H. E., 1943. Limits of the pack-ice in the Antarctic in the area between 40° Wand 110° E. Hvalriidets Skifter, 9. Oslo.
HouTMAN, TH, J., 1968. Surface temperature gradients at the Antarctic Convergence. N. -<:,.]. Geol.
Geophys., 7(2): 245-270.
MACKINTOSH, N. A., 1946. The Antarctic Convergence and the distribution of surface temperatures in
Antarctic waters. Discovery Rep., 23: 177-212.
MACKINTOSH, N. A. and HERDMAN, H. F. P., 1940. Distribution of the pack-ice in the southern ocean. Discoveiy Rep., 19: 285-296.
PERHOEHL, l\!I. C., 1966. Antarctic pack ice boundaries established from Nimbus I pictures. Science, 153:
861-863.
SissALA, J.E., SABATINI, R.R. and LcKERMANN, H.J., 1972. Nimbus satellite data for polar ice survery.
Pola Ree., 16(102): 367-373.

Sci. Rep. Whales Res. Inst.,

No. 26, 1974

FATTY ACID COMPONENT OF DIFFERENT BLUBBEROIL OF FINLESS PORPOISE
SHINGO ITOHANDHIDEO TSUYUKI
Department of Food Engineering, College of Agriculture & Veterinary Medicene, Nihon University, Tokyo

ABSTRACTThis paper describes the fatty acid components of oils contained in different blubbers of Finless porpoise, Neophocaena phocaenoides. The sample oils
were almost entirely triglycerides, but contained only trace amouts of sterols
and sterolesters.
The fatty acid components of oils extracted from different blubbers ofFinless porpoise contained chiefly C16:1 (38.39-48.89%), C14:o (9.0013.92%), C14:t (8.75-12.36%) and C16:0 acids (7.22-11.80%). Although
the proportion of fatty acid components contained in this experimental Finless
porpoise deviated slightly from other dolphins and porpoises, and also
was only a low level of iso-valeric acid which was comparatively much indolphin and porpoise oil, the distribution pattern was comparable to thoseof dolphin and porpoise as reported by others.
INTRODUCTION

In the previous paper (Tsuyuki and Itoh, 1969), we reported that the blubber oilof an adult Finless porpoise consisted of 26 kinds of fatty acids with 8 to 22 carbon
atoms, including mainly C16:1 and C1s:1 acids.
This paper is concerned with the fatty acid components and distribution patterns of oils extracted from different part of a newly-born Finless poroise,.Neophocaena phocaenoides, who was caught off the coast of Kawasaki, Kanagawa Prefecture, Japan, in June 1973. The mammal was a female with the size of 71.5 cm
in length and 6.15 kg in weight.
We are much indebted to Dr. Toshio Kasuya who presented us the blubbersof Finless black porpoise.
MATERIAL AND METHODS

The sample oils were extracted from five different blubbers of the Finless porpoiseby a high-speed blending with chloroform/methanol (2/1, v/v). The blubbers
were front part of blow hole, dorsal part, thoracic part, tail part and dorsal fin.
The properties of extracted oils are shown in Table 1. The sample oils weredeveloped in thin layer chromatography on 0.25 mm thick layers of silicic acid
Sci. Rep. Whales Res. Inst.,
No. 26, 1974, 303-306

304

ITOH AND TSUYUKI(Wakogel B-5, Wako-Junyaku-Kogyo) with pertroleum ether-ethyl ether-glacialacetic acid (90/10/1, v/v/v). Each blubber oil consisted of almost triglycerides
respectively, having trace amount of cholesterols and cholesterolesters.
TABLE 1.

PROPERTIES OF DIFFERENT BLUBBER OILS OF FINLESS PORPOISE.

Blubbers
Appearance (at 30°C)
Oil content (%)
Refractive index (at 40°C)
Acid value
Iodine value (Wijs)
Saponification value
Unsaponifiables (%)

Front ofblow holeDorsalThoracic

Tail

Dorsal fin

Yellowish
liquid30.0
1.4546
0.54
60.8
213.4
1.49

Yellowish
liquid46.7
1.4596
0.89
71.4
220.4
0.83

Yellowish
liquid42.2
1.4586
0.95
68.8
221.4
0.64

Whitishliquid19.4
1.4592
0.61
77.8
225.5
1.44

Whitishliquid5.3
1.4597
0.55
84.1
224.3
0.37

Gas liquid chromatography (GLC) was conducted with a Shimadzu Instrument, Model 4PTF, using 267 cm X 3.0 mm id glass column packed with 5 % diethyleneglycol succinate (DEGS) on 80-100 mesh Chromosorb W (AW, DMCS)
and a hydrogen ionization detector. Shortchain components were resolved thermally at column temperature programming the range of 70-190°C, 4°C per minute.
Long-chain components were analyzed at column temterature of205°C isothermally.
The fatty acid methyl esters of sample oils were esterified by BF 3-methanol reagent
according to the method of Metcalfe et al (1966). The methyl esters were purified
by thin layer chromatography in petroleum ether-ethyl ether-glacial acetic acid(90/10/1, v/v/v) at low temperature and nitrogen atmosphere to prevent losses ofshort-chain components. The GLC peaks were identified by the use of pure standards (Apllied Science Laboratories, Inc.) and polyunsaturated component peaks
were identified by the difference between GLC patterns before and after hydrogenation with platinum black reagent at the regular intervals. All fatty acid peaks
obtained on chromatogram were reported as weight percentages of total known
fatty acids presented by the method ofMagidman et al. (1962).
RESULTS AND DISCUSSION

The fatty acid components of different blubber oils in this Finless porpoise arelisted in Table 2. The five different blubber oils have 44 kinds of fatty acids withthe range of 8 to 22 carbon atoms, and the fatty acid components and distributionsof those oils are entirely to be the same pattern. The most prominent fatty acids
in different blubber oils are 38.39 % to 48.89 % of C16 , 1 acid; 9.00 % to 13.92 % of
C14:o acid; 8.75 %to 12.36 %of C14:1 acid; 7.22 %to 11.80 %of C16 , 0 acid; 4.67 % to
6.46 % of C1s: 1 acid, respectively. The total percentages of the above metnioned
five fatty acids in all fatty acids are respectively 77.26 % of front blubber of blowhole, 87 .35 %of dorsal blubber, 85.51 %of thoracic blubber, 83.33 %of tail blubber
and 82.39 % of dorsal fin blubber. The percentages of total saturated acids vary
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

FINLESS PORPOISE OIL

305

TABLE 2. FATTY ACID COMPONENT OF DIFFERENT BLUBBER OILSOF FINLESS PORPOISE.
Blubbers
Fatty acids

Front ofblow holeDorsalThoracic

Tail

Dorsal
fin

5:0
6:0
8:0
Iso 10: 0
10: 0
Iso 11: 0
11: 0
Iso 12: 0
12: 0
Iso 13: 0
13: 0
Iso 14: 0
14: 0
Iso 15: 0
15: 0
Iso 16: 0
16: 0
17: 0
18: 0
20: 0
Total saturated

2.55
0.24
0.29
0.14
0.85
0.04
0.25
0.70
3.14
0.47
0.15
0.98
13.85
2.46
0.53
2.44
11.31
0.34
0.02
0.02
40.77

1.07
0.16
0.26
trace
0.49
trace
0.12
0.25
2.15
0.08
0.01
0.28
12.89
1.15
0.29
o. 70
10.33
0.27
0.12
0.04
30.67

0.71
0.13
0.31
trace
0.57
trace
0.11
0.27
2.24
0.12
0.08
0.34
13.92
1.55
0.51
0.89
11.80
0.42
0.13
0.02
34.12

0.46
0.30
0.37
0.09
0.41
0.05
0.16
0.31
1.81
0.21
0.07
0.53
10.77
2.13
0.45
1.47
8.16
0.34
0.10
0.03
28.22

2.30
0.45
0.32
0.04
0.31
0.03
0.14
0.24
1.53
0.28
0.08
0.43
9.00
l. 70
0.48
1.15
7.22
0.38
0.09
0.01
26.18

Monounsaturated
6: 1
8: 1
10: 1
12: 1
14: 1
16: 1
18: 1
20: 1
22: 1
Total monounsaturated

0.52
0.08
0.51
0.89
8.75
38.39
4.96
0.07
0.05
54.22

0.32
0.09
0.66
o. 70
10.57
48.89
4.67
0.08
0.04
66.02

0.29
trace
0.76
0.75
10.35
44.72
4.72
0.05
0.04
61.68

0.43
0.22
0.69
0.92
12.15
46.80
5.45
0.07
0.08
66.81

0.77
0.07
0.67
0.91
12.36
47.35
6.46
0.08
0.08
68.75

0.53
l. 75
0.32
0.22
0.99
0.23
0.05
0.09
0.18
0.17
0.08
0.02
0.06
0.11
0.21
5.01
100.00

0.51
0.47
0.14
0.26
0.83
0.29
0.03
0.06
0.17
0.13
0.05
0.02
0.02
0.15
0.18
3.31

0.55
0.94
0.31
0.44
0.81
0.30
0.03
0.09
0.15
0.11
0.07
0.02
0.08
0.12
0.18
4.20

0.65
1.11
0.24
0.28
1.09
0.44
0.04
0.10
0.28
0.19
0.06
0.05
0.04
0.14
0.26
4.97

100.00100.00100.00

0.73
1.01
0.29
0.24
1.36
0.42
0.04
0.10
0.19
0.15
0.05
0.04
0.07
0.14
0.24
5.07
100.00Saturated
Iso

Polyunsaturated
12: 2
14: 2
16: 2
16: 3
18: 2
18: 3
18: 4
20: 2
20: 3
20: 4
20: 5
22: 2
22: 3
22: 5
22: 6
Total polyunsaturated

Sci. Rep. Whales Res. Inst.,

No. 26, 1974

ITOH AND TSUYUKI

306

from 26.18 % to 40. 77 % and similarly those of total unsaturated acids vary from59.23 % to 73.82 %. Among the saturated acids, C16:0 and C14:o acids are the main
constituents in those oils. The proportions of fatty acids with more than 20 carbon
atoms and the range of 6 to 8 carbon atoms have very small amounts.
In comparison with the previous study (Tsuyuki and Itoh, 1969), the mostprominent fatty acids of the blubber oil in previous work were 26.9 % of C 16 ,i, 20.4%
of C 18 , 1 and 8.4% of C14:o acids. Among those fatty acids, C18:1 acid is notably
different to this experimental blubber oils which contained 4.67 % to 6.46 %· C16:1
and C 14 , 0 acids of the former oil were reversely lower amounts than 38.39% to48.89 % and 8. 75 % to 12.36 % of the latter oils respectively. The ratio of total
saturated acids vs total unsaturated acids in the latter oils somewhat close to thatof the former oil. The latter oils contained proportionately larger amounts of shortchain length acids than the former oil, but the levels of C22 :s and C22:6 acids of polyunsaturated acid were found to be the lower levels than those (C22:s 3.9 %, C22:6
5.3 %) of the former oil. Although the fatty acid proportion in the oils of the newlyborn Finless porpoise in this study and the adult Finless black porpoise in thepi:evious study had thus difference, there were obviously a similar pattern in thefattly acid distribution.
On the other hand, the proportion and distribution of the fatty acid component in this experimental dolphin oil are assumed to be nearly similar to theresults of a number of studies in other dolphin oils as reported by others, but isovalericacid from 0.46 % to 2.55 % in this study was comparatively small amount for thereason that the sample was blubber tissue.
SUMMURY

1. The properties and fatty acid components of oils contained in different
blubbers of Finless black porpoise, Neophocaena phocaenoids, have been studied.
2. The fatty acid components chiefly consisted of C14:o, C14:t, C16:0, C16:1 andC 18 :1 acids in different blubber oils.
3. The fatty acid distributtion patterns in different bubber oils were almost
similar to each other.
4. The Finless black porpoise oil had the fatty acid pattern which was characteristic of dolphin and porpoise oil.
REFERENCES
MAGIDMANN, P., S. E. HERB, F. E. LuDDY and R. W. RIEMENSHNEIDER, 1962. Fatty acid cowmilk, II.
Composition by gas-liquid chromatograph aided by other methods of fractionation. ]. Am. Oil Chemists'
Soc., 39: 142-146.
METCALFE, L. D., A. A. SCHMITZ andJ. R. PELKA, 1966. Rapid preparation of fatty acid esters from lipids
for gas chromatographic analysis. Anal. Chem., 38: 154-155.
TsuYUKI, H. and S. IToH, 1969. Fatty acid composition of Finless porpoise oil. Sci. Rep. Whales Res. Inst.,

21: 137-141.

Sci. Rep. Whales Res. Inst.,

No. 26, 1974

FATTY ACID COMPONENT OF SENEGALMANATEE FATS
SHINGO ITOHANDHIDEO TSUYUKI
Departmeni of Food Engineering, College of Agriculture & Veterinary Medicine, Nikon Universiry, Tokyo.

ABSTRACTThe fats in cerviel, thoracic and dorsal fatty tissues, and thoracic muscle
tissue of Senegal manatee, Trichechus senegalensis, were analyzed for total lipid
content and fatty acid components. Although the above three fatty tissues
of Senegal manatee contained very rich amounts of fat, the muscle tissue contained consisderably small quantity of fat.
The fatty acid components of Senegal manatee fats contained high levelsof C14:0 (14.97-18.66%), C16:0 (24.57-27.78%), C16:1 (6.69-7.32%) andC1s:1 acids (36.86-39.75%), and had a unique proportion with higher levelsof saturated acids (50.16-52.93%). Although the fatty acid component anddistribution pattern in Senegal manatee fats deviated from most of marine
and fresh water mammals, those was nearly closed to that of Dugong fat.
INTRODUCTION

Manatees-sea cows-are completely aquatic and live solely on vegetation beneaththe water along coasts, and in estuaries and rivers. They are named as Trichechus
manatus in rivers and off coasts of Florida to British Guiana, as T. inunguis in riversof Brazil and as T. selegalensis in rivers of West Africa. Their adults reach up to
3 m in length and have remarkably fatty tissue body.
We have investigated the fatty acid component of Senegal manatee, T. senegalensis, fats. No previous studies of T. senegalensis fat have been reported in theliterature.
Greatest thanks are due to Mr. Kazue Nakamura of the Kanagawa Prefectural
Museum who was kindly enough to present us the Senegal manatee fat.
MATERIAL AND METHODSThe Senegal manatee, T. senegalensis, studied was caught by trawling at 60 km of
upper stream from the estuary of the Gambia river of West Africa in January 1973.
The mammal was an immature male of about 158.0 cm in length. The portions ofcervical, dorsal and thoracic fatty tissues, and thoracic muscle tissue were cut
up into small pieces and respectively extracted several times with chloroformmethanol (2: 1) using a high-speed blender. The solvent was dried with anhydrous
Sci. Rep. Whales Res. Inst.,
No. 26, 1974, 307-311

ITOH AND TSUYUKI

308

sodium sulfate and completely distilled off under high vacuum. The properties
ofrecovered sample fats are shown in Table 1. Each sample fat was then subjected
to preparative thin layer chromatography on 0.25 mm thick layers of silicic acid
(Wakogel B-5, Wako-Junyakaku-Kogyo) developed with petroleum ether-ethyl
ether-glacial acetic acid (90: 10: 1). The fats in the above three fatty tissues
were almost entirely triglycerides and slightly the spots of cholesterol and cholesterolesters. On the other hand, the fat from thoracic muscle tissue was almost triglycerides similar to other sample fats. It had not only cholesterol and cholesterolesters, but also slightly phosphatides. The sample fats in cervical, dorsal and thoracic
fatty tissues were softenend at 33.9-34.2°C and cleared finally at 35.4-36.0°C in
1 mm id capilary. The fat from thoracic muscle tissue was softened at 32.6-34.1°C
and cleared at 35.0°C.
The sample fats converted to fatty acid methyl esters by the method of Metcalfe et al. (1966), using BF 3-methanol reagent. So as to purify, the fatty acid methyl
esters were then subjected to preparative thin layer chromatography on 2.00 mm
thick layers of Wakogel B-5 developed with petroleum ether-ethyl ether-glacialacetic acid (90: 10: 1).
TABLE 1.

PROPERTIES OF DIFFERENT TISSUE FATS OF SENEGAL MANATEE.
Fatty tissues

Appearance (at 30°C)
Oil content (%)
Refractive index (at 50°C)
Acid value
Iodine value
Saponification value
Unsaponifiables (%)

CervicalDorsalThoracicThoracicmuscletissueWhitishsemi-solid
78.0
1.4527
0.21
48.1
209.1
0.34

Whitishsemi-solid
69.1
1.4531
0.29
47.3
210.8
0.38

Whitishsemi-solid
71.8
1.4532
0.24
46.9
209.2
0.35

Yellowish
semi-solid
5.8
1.4536
0.32
47.4
207.7
0.51

The gas liquid chromatography (GLC) analyses of methyl ester samples were
performed with Shimadzu Model 4PTF apparatus using a hydrogen ionization
detector under the following conditions: 267 cm by 3 mm diameter glass column
containing 5 %DEGS on Chromosorb W (AW, DMCS), and operating at the temparature programmed from 70-190°C, 4°C per minute for short-chain components
and isothermally at the temparature 205°C for long-chain components. The carrier gas was flowed at the rate of 35 ml per minute by nitrogen gas.
The fatty acids were identified by comparison with standard mixtures (Applied Science Laboratories, Inc.) and GLC analyses with the same apparatus under
the same conditions between before and after hydrogenation by platinum black
reagent at the regular intervals. All fatty acid peaks were caluculated as weightpercentages of total known fatty acids presented by the method of Ettre and Kabot(1962).
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

SENEGAR MANATEE FATTABLE 2.

309

FATTY ACID COMPONENT OF DIFFERENT TISSUE FATS OFSENEGAL MANATEE.
Fatty tissues
CervicalDorsalThoracicThoracicmuscletissue

6:0
8:0
10: 0
12: 0
!so 14: 0
14: 0
15: 0
!so 16 :0
16: 0
17: 0
18: 0
19: 0
20: 0
Total saturated

0.81
0.31
3.14
1.65
0.04
15.98
0.50
0.31
24.82
0.54
2.73
0.09
0.74
51.66

trace
0.19
1.59
1.30
trace
14.97
0.28
0.37
27.78
0.47
2.53
0.05
0.63
50.16

0.72
0.27
2.52
1.54
trace
18.66
0.42
0.35
24.57
0.36
2.77
0.04
0.70
52.93

0.16
2.09
1. 70
0.05
15.72
0.33
0.08
26.12
0.55
2.84
0.02
0.54
50.21

Monounsatrated
12: 1
14: 1
16: 1
18: 1
20: 1
22: 1
Total monounsaturated

0.14
0.41
7 .18
37.60
0.33
0.26
45.92

trace
0.28
7.30
39.75
0.21
0.20
47.74

0.09
0.36
6.69
36.86
0.25
0.19
44. 71

0.11
0.33
7.32
39.17
0.21
0.24
47.38

Polyunsaturated
14: 2
16: 2
16 :3
18: 2
18: 3
20: 2
20:3
20 :4
22: 2
22: 3
22: 5
22: 6
Total polyunsaturated

0.36
0.24
0.49
0.32
0.41
0.20
0.04
0.06
0.06
0.04
0.09
0.11
2.42

0.27
0.42
0.42
0.22
0.28
0.22
0.05
0.04
0.05
trace
0.06
0.07
2.10

0.35
0.28
0.43
0.34
0.40
0.24
0.03
0.04
0.04
0.02
0.08
0.11
2.36

0.33
0.30
0.46
0.41
0.51
0.13
0.02
0.02
0.05
0.01
0.07
0.10
2.41

100.00100.00100.00100.00Fatty acids
Saturated

RESULTS AND DISCUSSION
The properties of fats extracted from different tissues of the experimental Senegal
manatee are shown in Table I. High amounts of fat content were observed in
cervical, dorsal and thoracic fatty tissues as 78.0 %, 69.1 % and 71.8 % respectively.
But thoracic muscle tissue contained only a small amount fat of 5.8 %· It can be
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

310

ITOH AND TSUYUKI

seen that other properties are nearly closed to each other.
The fatty acid components of fats contained in different tissues of the African
manatee are listed in Table 2. The sample fats were found to consist of 31 kindsof fatty acids with 6 to 22 carbon atoms, but the proportion of C6:o acid absents inthoracic muscle tissue fat. The fatty acid components and distribution patterns
were very closed to each other. High amounts of C14:o (14.97-18.66 %), C 16 :o(24.57-27.78%), C16:1 (6.69-7.32%) and C1s:1 acids (36.86-39.75%) were observedin all tissue fats. The combined percentages of C14: i, C16: o, C16: 1 and C 18: 1 acids
were respectively 85.58 % of cervical fat, 89.80 % of dorsal fat, 87.05 % of thoracic
fat and 91.53 % of thoracic muscle fat in total each fatty acid. The main constituents of the saturated acid were similarly C14:o and C 16:o acids whereas the monounsaturated acids were C 18 : 1 and C16:t acids. The least amounts of polyunsaturated
acids with more than double bonds were contained 2.42 % of cervical fat, 2.10% of
dorsal fat, 2.36 % of thoracic fat and 2.41 % of thoracic muscle fat. It is interesting
to note that 97.58 %-97.90 % of total fatty acids were only saturated and monounsaturated acids. The African manatee fats consist of the highest amounts of total
saturated acids. The ratio of total saturated acids vs unsaturated acids is about
half and half as followed: 51.66 % vs 48.34 % of cervical fat, 50.16 % vs 49.84 % of
dorsal fat, 52.93 % vs 4 7.07 % of thoracic fat and 50.21 % vs 49. 79 % of thoracic
muscle fat, respectively.
In the comparison with the fat contained in Dugong, Halicore dugong (Tsuyuki
and Itoh, 1967), the Senegal manatee fats are most nearly allied to its fat. The
Dugong fat was observed the high amounts of C 14 :o (9.8%), C16:0 (23.0%), C16:1
7.7%) and C 18 : 1 acids (41.3%) being similar to the Senegal manatee fats. The
fatty acids ofC 10 :o (0.1 %), C 12 , 0 (0.2%) and C 14:o (9.8%) contained in the Dugong
fat were slightly smaller levels than those of the Senegal manatee fats. But the
fatty acids of C14:o (0.8 %), C14:2 (0.9 %), C16:2 (1.6 %), C11:0 (1.2 %), C1s:2 (3.4 %)and C 18 :3 (4.1 %) contained in the Dugong fat were reversely higher levels thanthose of the Senegal manatee fats. It is a point of interest that the fatty acids withmore than 20 carbon atoms were not observed in the Dugong fat with exception of
C20:o (I. 7 %) and C20 ,4 (1.5 %). Although the fatty acid component and distribution pattern between the Senegal manatee and the Dugong fats were nearly symmetrical for most fatty acids, those deviated from most of marine and fresh water mammal fats.
SUMMARY

1. The properties of fats contained in different tissues of Senegal manatee,
T. senegalensis, was studied.
2. The fatty acid components of different fatty tissues and muscle tissue fats
extracted from the mammal had been determined by GLC analysis.
3. It was confirmed that four main fatty acids of C14:o, C16:0, C16:1 and C1s:1
accounted about 90 % of total fatty acids in those tissue fats; 26 others were foundin only low quantities.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

SENEGAR MANATEE FAT

311

4. The Senegal manatee fat was nearly similar to the Dugong fat in the fatty
acid component and distribution pattern.
REFERENCESETTRE, L. S. and F.J. KABOT, 1963. Relative response of fatty acid methyl esters on the flame ionization
detector. J. Chromatog., 11: 114-116.
METCALFE, L. P., A. A. SCHMITZ and L. R. PELKA, 1966. Rapid preparation offatty acid esters from lipids
for gas chromatographic analysis. Anal. Chem., 38: 154-155.
TsUYUKI, H. and S. ITOH, 1967. Fatty acid composition of the Dugong oil. Bull. Jap. Soc. Sci. Fish., 33:
1035-1037.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

THE HYOID BONES OF TWO KINDS OF HARBOURSEALS IN THE ADJACENT WATERSOF HOKKAIDOYASUHIKO NAITO
Kominato Marine Biological Laboratory, TokJ'O University of Fisheries., Kominato

ABSTRACTThe hyoid bones of the harbour seal in the adjacent waters of Hokkaido
were examined, and remarkable differences were found between those of theice-breeding and the land-breeding harbour seals. The land-breeding harbour
seal completely lost their tympanohyals. Moreover their stylohyals were quite
small and their proportional length was about one tenth of that of the icebreeding seal. However, in the epihyals the land-breeding seal possessed thelonger bones than the ice-breeding seal.
INTRODUCTION

The hyoid bones have been considered to be a systematic character in the whales(Omura, 1964), however, in the seal careful consideration has never been given to
the hyoid bones. In the adjacent waters of Hokkaido, there were found two kinds ofharbour seals; the ice-breeding harbour seal and the land-breeding harbour seal
(Inukai, 1942; Belkin, 1964; Naito and Nishiwaki, 1972 a, b, etc.). The morphological studies on these harbour seals were performed in Hokkaido from 1969 to 1971.
In these studies, I found the incomplete hyoid bones in the land-breeding seal while
the normal hoid bones were found in the ice-breeding seal, and the outline of thisdifference between them was already reported quite briefly (Naito and Nishiwaki,
1972b ). In the present paper some measurements of the hyoid bones of these seals
were examined. But further studies on this problem are required to clarify thesystematic or taxonomical problems of the North Pacific harbour seals.
Concerning the scientific name of the above harbour seals, I had already used
"Phoca vitulina largha" for the ice-breeding seal and "Phoca kurilensis" for the landbreeding seal in my previous papers, however, in the present paper I do not use
these names, for systematical studies on the North Pacific harbour seals have been
advancing in recent years and taxonomical reconsideration on these seals seems to
be required (Fay and Burns, private communication).
MATERIALS AND METHODS

The ice-breeding seals were caught at the Okhotsk coast of Kitami district and theShiretoko Peninsula where the sealing on this kind of seal is active, and the landSci. Rep. Whales Res. Inst.,

No. 26, 1974, 313-320

NAITO314

breeding seal was caught at the Pacific coast of the Nemuro Peninsula where thiskind of seal is dominant. Thirty three hyoid bones of the ice-breeding seal and 10
hyoid bones of the land-breeding seal were collected as materials. Since samples
are quite short in the land-breeding seal, it was difficult to compare the hyoidbones between above two kinds of seals by the same age and the same sex.
The hyoid bones were taken off from the tongue. Then each bone of the hyoid
was separated and measured. The cartilagionous tympanohyals taken off from thetympanic bullae were not measured, for their length and shape were much changed
after drying.
GENERAL DESCRIPTION AND MEASUREMENTS

It is usually thought that the hyoid bones of the harbour seals are consisted of elevenbones such as one basihyal, 2 thyrohyals, 2 keratohyals, 2 epihhyals, 2 stylohyals and2 tympanohyals (Plate I, II). All of these hyoid bones are seemed to be normallyfound in the pinnipeds. I had examined and found the same composition of thehyoid bones in the ribbon seal and ringed seal collected from the Sea of Okhotsk,
and also in the steller sea lion and the south American sea lion Otaria byronia.
Each of the hyoid bones of these animals were found to be well developed. However, the hyoid bones of the land-breding harbour seal in the present work appeared to be quite different from those of above mentioned animals.
The cartilagionous tympanohyals which connect with the tympanic bullae in~2)--'

---

A
I

I

I

8

Fig. I. The positions of the measurements. L, length of basihyal; B, length of
stylohyal; C, length of epihyal; D, length of heratohyal; E, length of thyrohyal.

Sci. Rep. Whales Res. Inst.
No. 26, 1974

315

HYOID BONES OF HARBOUR SEAL

above animals were almost undeveloped and hard to find out in the land-breeding
harbour seal. Therefore one end of the stylohyals were free in the tongue with theother end connecting with the epihyals. While in the ice-breeding harbour seal,
these tympanohyals were well developed and were completely connected with theposterior part of tympanic bullae crossing over the surface of it from anterior part.
The second remarkable difference between the ice-breeding and the landbreeding harbour seals was found in the stylohyals. The stylohyals of the icebreeding seal were thin and slender but well developed in its length. Most of thesebones were almost round and straight but some were found to be slightly curved,
and the epihyal side of these bones was thickened while the other side was lessthickened. In the land-breeding harbour seal these stylohyals were incomparablly
different from those of the ice-breeding one. They were quite small like a minutefragment, and it seemed to be easily failed to be found out in the young seal, whilethese bones were solid and firm like other hyoid bones in the adult seal. The formsof these bones were full of variety, and they differ much even between left and rightbones.
0

10

20 30 40 50

60 70 80~

stylohyals

II

90 100 110 120 130 140

+

I

I

II W?4*1111

epihya.lsIkera.toh'yals

I
+
H$H
I

I

I E$:3 I

thyrohya\s

-+

I I
0

10 20 30 40

50 60

I

I

70 80 90 100 110 120 130 140 (°lo)

Fig. 2. Proportional length of each bone of the hyoid against the basihyal length.
The horizontal line, range; vertical line, mean; outer box, standard deviation;
inner box, standart error. Upper, land-breeding harbourseal; lower, ice-breeding
harbour seal

Other hyoid bones did not show much obvious differences in above two kindsof harbour seals. In the land-breeding seal, however, the epihyals, keratohyals
and thyrohyals showed massive and firm more than those of the ice-breeding seal.
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

316

NAITO

Concerning the shapes of epihyals and keratohyals, they showed a little difference
between above two kinds of seals. The epihyals of the ice-breeding seal were thinin center part and thick in both ends while those of the land-breeding seal were tapered, thick in the keratohyal side and thin in the stylohyal side. The keratohyalsof the ice-breeding seal were also thick in both ends and thin in center, but those of
the land-breeding seal were very short and no constricted or narrow parts were
found.
The measurements were made on each hyoid bone (Fig. 1), and the proportional length of stylohyals, epihyals, keratohyals and thyrohyals was calculated inpercentage against the basihayals. The average length of left and right bone wasused for calculation. The artithmetic mean, standard variation and standard error
were also calculated for the sake of comparison. The calculated results were shownin figure 2. As shown in this figure, the most obvious difference was found in thestylohyals. The proportional length of the land-breeding harbour seal was about
one tenth of that of the ice-breeding harbour seal. The proportional length of
epihyals was larger in the land-breeding seal than in the ice-breeding seal. In the
keratohyals, the ice-breeding seal was larger. In the thyrohyals, both seals showedalmost same proportional length, and as a matter of fact the shape of these bones
showed better resemblance than others.
DISCUSSION

There were definite differences in the hyoid bones between the ice-breeding andthe land-breeding harbour seals in Hokkaido. The land-breeding seal possessed aminute stylohyals and no tympanohyals while the ice-breeding seal possessed welldeveloped these bones. It is of interest to consider above differences from the pointof view of systematics of the North Pacific harbour seals.
In the North Pacific, there seems to be three kinds of harbour seals; the icebreeding seal in the Bering Sea and the Sea of Okhotsk, the land-breeding seal in
the Pacific coast of North America from Alaska to as far south as Mexico, and also
land-breeding seal from the Aleutian Islands to as far west as the Kuril Islands andHokkaido. The systematics of above three kinds of seals are still uncertain.
Especially the systematic relation between above two kinds of land-breeding seals
is quite unknown. Newby informed me in his private communication that theland-breeding harbour seal in Washington possessed the normal hyoid bones.
Fay and Burns also informed me in their private communication that the incomplete hyoid bones were found in the harbour seal in Alaska where above threekinds of harbour seals seem to be common. However, we have quite short data to
discuss the systematics of the North Pacific harbour seals by means of the hyoid bones.
ACKNOWLEDGMENTS

It is a pleasure to extend my grateful thanks to Professor M. Nishiwaki, Ocean
Research Institute, University of Tokyo, who gave me constant encouragement andSci. Rep. Whales Res. Inst.,
No. 26, 1974

HYOID BONES OF HARBOUR SEAL

317

stimulation. I also express my sincere thanks to Drs. T. Kajihara, K. Numachi
and T. Kasuya, Ocean Research Institute, University of Tokyo, for their valuableadvice and discussions. In the field works, the greatest thanks go to Mr. Suzuki,
Engaru Fur Co. and Mr. N. Kanazawa, Kanazawa Fur Co., who have been very
helpful i.n collecting data.
REFERENCES
BELKIN, A. N., 1964. A new species ofseal-Phoca insularis n. sp.-from the Kuril Islands. Dokl. Akad. Nauk.
SSSR, 158: 1217-1219. (in Russian).
INUKAI, T., 1942. Hair seals in our northern waters (I). ShokubutsuDobutsu, 10 (10): 927-932. (inJapanese).
NAITO, Y., and M. NISHIWAKI, 1972a. The growth of two species of the harbour seal in the adjacent waters of
Hokkaido. Sci. Rep. Whales Res. Inst., 24: 127-144.
NArro, Y., and M. NISHIWAKI, 1972b. Ecology and morphology of Phoca vitulina largha and Phoca kurilensis
in the southern Sea of Okhotsk and north east of Hokkaido. Symposium on the Biology of the seal., Universityof Guelph, Ontario Canada. (in press).
OMURA, H., 1964. A systematic study of the hyoid bones in the whales. Sci. Rep. Whales Res. Inst., 18: 149170.

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

318
APPENDIXMEASUREMENTS OF HYOID BONES(upper, right; lower, left; in mm)
The ice-breeding seal :Body length

Age

Sex

Basihyals

155

8

F

24.7

140

7

F

22. l

166

11

M

24.6

153

18

F

23.7

111

0

F

17.2

149

3

M

25.0

142

4

F

23.6

M

22.9

162

12

F

22.4

149

6

F

22.2

162

20

F

23.6

176

22

M

26.5

139

7

F

22.3

M

16.3

M

20.0

110

91

6

M

17.8

132

3

M

22.2

152

4

F

25. l

M

20.4

18

M

27.0

139

2

:M:

24.5

155

18

F

22.5

F

20.8

127

126

Thyrohyals Keratohyals

23.3
22.2
21.5
19.4
23.3
24.2
20.8
15.3
20.9
21.0
20.6
20.2
23. l
22.7
22. l
16.8+
29.3
25.2
25. l
22.3
22.6
20.8
21.9
20.9
15. l
15.2
12.8
13. l
20.1
20.0
23.0
23.3
17.2
27.8
27.5
18.5
19.0
19.2
18.2

155

26

M

26. l

19.2
22.l

94

0

F

18.2

14.8
15.0

17.0
16.8
11. 7
12.6
14.7
13.7
16.0
10.5
9.6
13.9
12.8
11. l
10.6
13.3
12.0
11.3
12.l
13.7
13.3
16.8
16. l
15.6
13.7
12.2
12.0
11.0
10.5
10. l
9.0
8.9
10.8
10.8
11.5
11.3
10.0
10. l
13.5
14.8
11.8
11.8
13.3
14.0
11.8
14.0
14.5
14.0
10.0
11.0

Epihyals

Stylohyals

13.l
13.4
14.6
11.3
15.5
16. l
14.l
14.8
9.1

26.4
26. l
24.2
25.l
28.2
27.6
23.7
23.2
17.8
18. J
26.0
26.6
24.8
24.7
29.9
28.5
27.8
28.0
13.7
13. l
28.9
28.5
27.2
28.9
26.3

15.6
13.8
13.0
12.2
15.8
14.5
15.0
14.4
15.2
14.0
15.0
15.9
16.0
16.8
16.9
7.2
7.9
8.1
7.4
8.6
14. l
13.2
15.2
12.0
12.0
17.9
19.5
13.8
15.0
15.1
14.5
11. 7
11.8
18.0
19.1
8.1
6.7

17.0
17.6
14.9
15.2
13.5
14.0
22.9
22.4
25.5
25.5
18.9
20.0
27.1
28. l
22.5
21. 7
24.0
23.5
14.5
15.3
27.0
26.8
17.1
17.8

Continued ...
Sci. Rep. Whales Res. Inst.,
No. 26, 1974

319
APPENDIX

Continued.

Body length

Age

Sex

Basihyals

Thyrohyals

Keratohyals

Epihyals

Stylohyals

149

2

F

20.5

I36

2

M

22.8

F

20.5

21.3
21.9
18.8
18.9
17.2
17.8
17.2
17.2
26.5
26.5
I3.9
13.0
14.2
13.3
26.9
26.5

I I. I
Il.5
I2. I
I2.2
10.2
9.9
I I. I
10.1
I5. I
I2. I

I5.0
14.5
10. I
I 1.3
10.8
11. I
11.8
13.2
I9.5
I9.6

27.9
27.4
2I .2
21. I
I9.0
I8.9
I I. I
17.1
28.6
29.0

7.9
9.5
11.2
I3.6
I4.0

6.2
6.6
5.7
I7.6
I8. l

14.3
I6.0
16.2
29.3
26. I

I2.0
I2.0
I3.8
I4.0
10.5
I0.5
6.9
6.9
10.1
10.7
7.7
7.9
12.l

I7.2
17.5
23. I
23.7
I6.5
I6.3
9.0
8.9
I6.B
I6.7
12.1
Il.6
19.4
19.B
I5.4
I5.2
I9.0
18.1

2.2
2.3
6. I
6.0
2.1
1.8
1.5
1.6
2.1
2.2
2.1

I08
I I4

0

F

21.2

I63

18

M

23.8

88

0

M

I6.7

97

0

M

I7.5

169

25

F

25.3

The land-breeding seal:

152

3

M

24.9

I78

7

M

28.3

I40

4

F

22. I

104

0

M

I5.0

149

3

F

24.8

104

0

M

17.5

168

7

F

23.9

I44

3

M

22.B

I5I

4

F

26.I

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

21.3
20.6
27.3
27.8
I9.8
I9.5
I3.8
I3.3
22.3
22.2
I5.l
14.3
24.5
23.9
I9.0
19.1
23.I
23.1

10. I
10.5
II.9
Il.5

2.4
2.4
1.9
1.5
2.5
2.0

320

EXPLANATION OF PLATESPLATE I. Hyoid bones of the ice-breeding harbour seal. The tympanohyals are
cut off. (upper, adult; lower, pup)
PLATE II. Hyojd bones of the land-breedjng harbour seal. (upper, adult; lower,pup)

Sci. Rep. Whales Res. Inst.,
No. 26, 1974

d
l
V'
J.
J
:
I:

v
u口S
・

め
z・
9
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ど6
長

Mψ
(
l
D
7
a
ys
a
s
1・
u
s
1
・
z

VN
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PLATEI
I

NAI
TO

S
c
i
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a
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sRe
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t
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.26
,1974

THE SCIENTIFIC REPORTS OF THE WHALES RESEARCHINSTITUTE, TOKYO, JAPANNUMBER 1, JUNE 1948
Akiya, S. and Tejima, S. Studies on digestive enzymt> in whale. 3-7
Akiya, S., Ishikawa, Y., Tejima, S. and Tanzawa, T. Studies on tryptase- from a whale (Balaenoptera
borealis L.). 8-10
Akiya, S., Tejima, S. and Ishikawa, Y. Studit>s on the utilization of whale mf'at by the use of pancreatic tryptase of whales. 11-14
Akiya, S. and Koba, F. The test culture of some microorganisms with whale meat peptone. 15-16
Nakai, T. Chemical studies on the freshness of whale meat. I. Evaluation of freshness and changes inquantity of several kinds of nitrogen in whale meat following deterioration of freshness. 17-26
Nakai, T. Chemical studies on the freshness of whale meat. II. On comparison between whale meatand beef on deterioration of freshnt>ss and autolysis. 27-30
Tawara, T. On the simultaneous extraction of vitamin A-D and vitamin B2 complex from the liver ofa fin whale (Nagasu-Kujira, Balaenoptera physalus L.). 31-37
Tawara, T. Studies on whale blood. I. On the separation of histidine from whalf' blood. 38-40
Nakai, J. and Shida, T. Sinus-hairs of the sei-whale (Balaenoptera borealis). 41-47

NUMBER 2, DECEMBER 1948
Ogawa, T. and Arifuku, S. On the acoustic system in the cetacean brains. 1-20
Yamada, M. Auditory organ of the whalebone whales. (Preliminary rt>port). 21-30
Nakai, T. Chemical studies on the freshness of whale meat. III. Effect of hydrogen-ion concentration
on decrease in freshness and titration curve of whale meat with HCl and Na 2 C0 3• 31-34
Ishikawa, S., Ornate, Y. and Soma, Y. Analytical distillation of vitamin A in the whale liver oil. 35-41
Ishikawa, S., Ornate, Y. and Kanno, H. Molecular distillation of sperm whale blubber oil. 42-45
Kaneko, A. Molecular distillation of fin whale liver oil. 4.6-50
Akiya, S. and Takahashi, K. Determination of tryptophane in whale meat. 51-54
Ishikawa, Y. and Tejima, S. Protein digestive power of sperm whale pancreatic enzyme. 55-60
Tsukamoto, S. Experiment on digestion of whale meat by koji-mould. 61-66

NUMBER 3, FEBRUARY 1950
Ogawa, T. and Shida, T. On the sensory tubercles of lips and of oral cavity in the sei and the fin
whale. 1-16
Ohe, T. Distribution of the red marrow in bones of the fin whale. 17-22
Hosokawa, H. On the cetacf'an larynx, with special remarks on the laryngeal sack of the sei whale andthe aryteno-epiglottideal tube of the sperm whale. 23-62
Akiba, T., Tsuchiya, T., Umehara, M. and Natsume, Y. Bacteriological studies on freshness of whale
meat. (Report No. 1). 63-70
Ishikawa, Y. Protein digestive power of sperm whale pancreatic enzyme. II. 71-78
Mori, T. and Saiki, M. Properties of fats and oils contained in various parts of a sperm whale body.
79-84
Tawara, T. and Fukazawa, R. Studies on kitol. I. PrPparation of kitol from whale liver oil. 85-88
Tawara, T. and Fukazawa, R. Studies on kitol. II. Influence of kitol fraction on the determinationof the International Unit of Vitamin A. 89-91
Tawawa, T. and Fukazawa, R. Studies on kitol. III. The effect of sunlight, air and heat on thf' vitamin A and kitol fractions. 92-95
Tawara, T. On the respiratory pigments of whale (Studies on whale blood II.). 96-101

ii
Yoshida, M. Research on methionine in whale. 102-105
Mizue, K. Factory ship whaling around Bonin Islands in 1948. 106-118
Mizue, K. and Jimbo, H. Statistic study of foetuses of whales. 119-131
Nishiwaki, M. and Hayashi, K. Biological survey of fin and blue whales taken in the Antarctic season
1947-48 by the Japanese fleet. 132-190

NUMBER 4, AUGUST 1950
Omura, H. On the body weight of sperm and sei whales located in the adjacent waters of Japan. 1-13
Omura, H. Diatom infection on blue and fin whales in the Antarctic whaling area V (the Ross Sea
area). 14-26
Omura, H. Whales in the adjacent waters of Japan. 27-113
Nishiwaki, M. Determination of the age of Antarctic blue and fin whales by the colour changes incrystalline lens. 115-161
Nishiwaki, M. Age characteristics in baleen plates. 162-183
Nishiwaki, M. On the body weight of whales. 184-209

NUMBER 5, JUNE 1951
Akiba, T., Umehara, M. and Natsume, Y. Bacteriological studies on freshness of whale meat. (Report
No. II.). 1-4
Hosokawa, H. On the pelvic cartilages of the Balaenoptera-foetuses, with remarks on the specifical andsexual difference. 5-15
Ohe, T. Iconography on the abdominal cavity and viscera of the Balaenoptera, with special remarks
upon the peritoneal coverings. 17-39
Akiya, S. and Hoshino, 0. Isolation of histidine from whale blood using 3, 4-dichlorobenzene sulfonicacid. 41-47
Tawara, T. and Fukazawa, R. Studies on kitol. IV. Purification of kitol by chromatographie. 49-51
Ishikawa, S., Omote, Y. and Okuda, H. Substances related to vitamin A in the whale liver oil. 53-59
Ishikawa, S., Omote, Y., Kijima, M. and Okuda, H. Thermal decomposition of kitol. 61-69
Mizue, K. Grey whales in the east sea area of Korea. 71-79
Mizue, K. Food of whales (In the adjacent waters of Japan). 81-90
Nishiwaki, M. and Ohe, T. Biological investigation on blue whales (Balaenoptera musculus) and fin whales(Balaenoptera physalus) caught by the Japanese Antarctic whaling fleets. 91-167

NUMBER 6, DECEMBER 1951
Hosokawa, H. On the extrinsic t-ye muscles of the whale, with special remarks upon the innervationand function of the musculus retractor bulbi. 1-33
Murata, T. Histological studies on the respiratory portions of the lungs of cetacea. 35-47
Kojima, T. On the brain of the sperm whale (Physeter catodon L.). 49-72
Mizue, K. and Murata, T. Biological investigation on the whales caught by the Japanese Antarctic
whaling fleets season 1949-50. 73-131
Nishiwaki, M. On the periodic mark on the baleen plates as the sign of annual growth. 133-152
Nishiwaki, M. and Hibiya, T. On the sexual maturity of the sperm whales (Physeter catodon) found in
the adjacent waters of Japan (I). 153-165
Nakai, T. Chemical studies on freshness of whale meat. IV. Some informations of Archomobacter ubiquitum
isolated from whale carcass. 167-176
Nakai, T. and Ono, H. The effects of electric shock and fatigue on post-mortem changes in muscle.
177-185

iii
Omote, Y. Complete recovery of vitamin A from molecular distillation residue of whale-liver oil. 187191
Omote, Y. Chemical structure of kitol (I). Double bonds and hydroxyl groups. 193-198
Hirata, M. Experimental investigation on flatterned head harpoon. An attempt for restraining ricochet. 199-207

NUMBER 7, JULY 1952
Ogawa, T. On the cardiac nerves of some cetacea, with special reference to thos(' of Berardius bairdii
Stejnegn. 1-22
Akiya, S., Hoshino, 0. and Motohashi, N. On an attempt to preserve whale meat freshness with 5nitro-furfuriden aminoguanidine from decay. 23-30
Akiya, S. and Sawamura, R. Colorimetric determination of 5-nitro-2-furfuridene aminoguanidine. 31-36
Tomiyama, S. and Takao, M. Studies on utilization of higher fatty alcohol from sperm whale oil. 3746
Omote, Y. A rapid method for the separate determination of vitamin A and kitol in the whale-liveroil. 47-50
Arai, Y. and Sakai, S. Whale meat in nutrition. 51-67
Yamaguchi, K. and Fujino, K. On the serological constitution of striped dolphin (Prodelphinus caeruleoalbus (Meyen)) (I). 67-77
Nishimoto, S., Tozawa, M. and Kawakami, T. Food of sei whales (Balaenoptera borealis) caught in the
Bonin Island waters. 79-85
Nishiwaki, M. On the age-determination of Mystacoc~ti, chiefly blue and fin whales. 87-119
Nishiwaki, M. and Hibiya, T. On the sexual maturity of the sperm whales (Physeter catodon) found in
the adjacent waters of Japan (II). 121-124
Ohno, M. and Fujino, K. Biological investigation on the whales caught by the Japanese Antarctic
whaling fleets, season 1950/51. 125-188

NUMBER 8, JUNE 1953
Yamada, lVI. Contribution to the anatomy of the organ of hearing of whales. 1-79
Omura, H. Biological study on humpback whales in the Antarctic whaling areas IV and V. 81-102
Fujino, K. On the serological constitutions of the sei-, fin-, blue- and humpback-whales (I). 103-125
Ogawa, T. On the presence and disappearance of the hind limb in the cetacean embryos. 127-132
Nishiwaki, M. and Yagi, T. On the age and the growth of teeth in a dolphin (Prodelphinus caeruleoalbus). (I). 133-146
Kakuwa, Z., Kawakami, T. and Iguchi, K. Biological investigation on the whales caught by the Japanese Antarctic whaling fleets in the 1951-52 season. 147-213
Nishiwaki, M, Hermaphroditism in a dolphin (Prodelphinus caeruleo-albus). 215-218

NUMBER 9, JUNE 1954
Akiya, S., Hoshino, 0. and Motohashi, N. Attempt to preservP freshness of whale meat with germicides. II. 1-10
Ogawa, T. On the musculature of the sinus venosus and its continuation with the so-called conducting
system of the whale's heart. 11-35
Yamada, M. Some remarks on the pygmy sperm whale, Kogia. 37-58
Yamada, M. An account of a rare porpoise, Feresa Gray from Japan. 59-88
Omura, H. and Fujino, K. Sei whales in the adjacent waters of Japan. II. Further studies on theexternal characters. 89-103
Fujino, K. On the serological constitution of the sperm- and haired beaked-whales (I) Blood groups of

iv
the sperm- and haired beaked-whales. 105-120
Fujino, K. On the body proportions of the fin whales (Balaenoptera physalus (L)) caught in the northern
Pacific Ocean (I) (Preliminary report). 121-163
Nishiwaki, M., Hibiya, T. and Kimura, S. On the sexual maturity of the sei whale of the Boninwaters. 165-1 77
Uda, M. Studies of the relation between the whaling grounds and the hydrographical conditions (I).
179-187

NUMBER 10, JUNE 1955
Hosokawa, H. Cross-sections of a 12-mm. dolphin embryo. 1-68
Nemoto, T. White scars on whales (I) Lamprey marks. 67-77
Omura, H. and Nemoto, T. Sei whales in the adjacent waters of Japan. III. Relation between movement and water temperature of the sea. 79-87
Omura, H., Fujino, K. and Kimura, S. Beaked whale Berardius bairdi of Japan, with notes of :(:,iphiuscavirostris. 89-132
Fujino, K. On the body weight of the sei whales located in the adjacent waters of Japan (II). 133141
Nishiwaki, M. On the sexual maturity of the Antarctic male sperm whale (Physeter catodon L.). 143149
Ohta, K. et al. Composition of fin whale milk. 151-167

NUMBER 11, JUNE 1956
Omura, H. and Sakiura, H. Studies on the little piked whale from the coast of Japan. 1-37
Nishiwaki, M., Hibiya, T. and Kimura, S. On the sexual maturity of the sperm whale (Physeter catodon)
found in the North Pacific. 39-46
Fujino, K. On the body proportions of the sperm whales (Physeter catodon). 47-83
Fujino, K. On the serological constitution of the fin whales II. Further studies on blood groups. 8598
Nemoto, T. On the diatoms of the skin film of whales in the northern Pacific. 99-132
Hoshina, T. and Sugiura, Y. On a skin disease and a nematode parasite of a dolphin, Tursiops truncatus(Montagu, 1821). 133-138
Iwai, E. Descriptions on unidentified species of dibranchiate cephalopods. I. An oegopsiden squid belonging to the genus Architeuthis. 139-151
Iwai, E. Descriptions on unidentified species of dibranchiate cephalopods. II. A cranchiidae squid of thegenus Taonius. 153-161
Uda, M. and Nasu, K. Studies of the whaling grounds in the northern sea-region of the Pacific Ocean
in relation to the meteorological and oceanographic conditions. (Part I). 163-179
Kimura, S. and Nemoto, T. Note on a minke whale kept alive in aquarium. 181-189
Ishikawa, Y. A characteristic property of whale oils concerning the absorption of gases. I. On theabsorption of carbon dioxide by whale oils. 191-213

NUMBER 12, JUNE 1957"
Omura, H. Osteological study of the little piked whale from the coast of Japan. 1-21
Nishiwaki, M. Age characteristics of ear plugs of whales. 23-32
Nemoto, T. Foods of baleen whales in the northern Pacific. 33-89
Nasu, K. Oceanographic conditions of the whaling grounds in the waters adjacent to Aleutian Islands
and the Bering Sea in summer of 1955. 91-101
Kimura, S. The twinning in southern fin whales. 103-125

v

Ichihara, T. An application of linf'ar discriminant function to external measurements of fin whale.
127-189
Nishiwaki, M. Very small embryo of cetacea. 191-192
Nishiwaki, M. One-eyed monster of fin whale. 193-195
Ogawa, T. and Kamiya, T. A case of the cachalot with protruded rudimentary hind limbs. 197-208
Uda, M. and Dairokuno, A. Studies of the relation between the whaling grounds and the hydrographic
conditions. II. A study of the relation between the whaling grounds off Kinkazan and the boundary of water masses. 209-224
Abe, T. Notes on fishes from the stomachs of whales taken in the Antarctic. I. Xenocyttus nematoi, a
new genus and n!'w species of zeomorph fish of the subfamily Oreosonimae Goode and Bean, 1895.
225-233
Tsuyuki, H. On the oils contained in various blubbers of northern elephant seal, Afirounga angustirostris.
235-240NUMBER 13, SEPTEMBER 1958
Omura, H. North Pacific right whale. 1-52
Nishiwaki, M. and Kamiya, T. A beaked whale Mesapladon stranded at Oiso Beach, Japan. 53-83
Nishiwaki, M. and Randa, C. Killer whales caught in the coastal waters off Japan for recent 10 years.
85-96
Ohsumi, S. (Kimura), Nishiwaki, M. and Hibiya, T. Growth of fine whale in the northern Pacific.
97-133
Nishiwaki, M., Hibiya, T. and Ohsumi, S. (Kimura). Age study of sperm whale based on reading of
tooth laminations. 135-153
Nishiwaki, M., Ichihara, T. and Ohsumi, S. (Kimura). Age studies of fin whale based on ear plug.
155-169
Fujino, K. On the serological constitution of fin whale. III. Human B blood group substances in erythrocytes and some notes on anti-fin Ju specific antibodies. 171-184
Nemoto, T. Cocconeis diatoms infected on whales in the Antarctic. 185-191
Nemoto, T. and Nasu, K. Thysanoessa macrura as a food of baleen whales in the Antarctic. 193-199
Ichihara, T. Gray whale observed in the Bering Sea. 201-205
Ohsumi, S. (Kimura). A descendant of Moby Dick or a white sperm whale. 207-209
Nasu, K. Deformed lower jaw of sperm whale. 211-212.
Omura, H. Note on embryo of Baird's beaked whale. 231-214
Uda, M. and Suzuki, N. Studies of the relation between the whaling grounds and the hydrographic
conditions. III. The averaged conditions of the whaling grounds and their trends of variation during
1946-55. 215-229
Seki, Y. Observations on the spinal cord of the right whale. 231-251
Kamiya, T. How to count the renculi of the cetacean kidneys, with special regard to the kidney ofthe right whale. 253-267
Hosokawa, H. and Sekino, T. Comparison of the size of cells and some histological formations between
whales and man. 269-301
Ogawa, T., Tsunoda, T. and Osawa, M. Amino acid composition of whale meat. 303-307
Ishikawa, Y. A characteristic property of whale oils concerning the absorption of gases. II. On theabsorption of nitrogen by whale oils. 309-321
Tsuyuki, H. Component fatty acids of northern elephant seal oil. 323-332

NUMBER 14, SEPTEMBER 1959
Omura, H. Bryde's whale from the coast of Japan. 1-33
Nishiwaki, M. and Kamiya, T. Mesaplodon ste}negeri from the coast of Japan.
Nishiwaki, M. Humpback whales in Ryukyuan waters. 49-87

35-48

Vl

Cushing, John E., Fujino, K. and Takahashi, K. Glycerol-freezing technique as an aid in blood typingof whales. 89-100
Fujino, K. and Cushing, John E. Blood typing of dried whale erythrocytes with 131 1 labelled antibody.
101-106
Ichihara, T. Formation mechanism of ear plug in baleen whales in relation to glove-finger. 107-135
Nasu, K. Surface water condition in the Antarctic whaling Pacific area in 1956-57. 137-143
Ohsumi, S. (Kimura). A deformed fin whale foetus. 145-147
Nemoto, T. Food of baleen whales with reference to whale mevements. 149-290
Yamada, M. and Yoshizaki, F. Osseous labyrinth of cetacea. 291-304
Nakai, T. Distribution of amino acid in proteins from various parts of whale body. 305-326

NUMBER 15, NOVEMBER 1960
Nishiwaki, M. Ryukyuan humpback whaling in 1960. 1-16
Ohsumi, S. Relative growth of the fin whale, Balaenoptera physalus (Linn.). 17-84
Fujino, K. Immunogenetic and marking approaches to identifying subpopulations of the North Pacificwhales. 85-142
Nasu, K. Oceanographic investigation in the Chukchi Sea du.ring the summer of 1958. 143-158
Tokita, K. and ECG Research Group. Electrocardiographical studies on bottlenosed dolphin (Tursiops
truncatus). 159-165

NUMBER 16, MARCH 1962
Omura, H. Bryde's whale occurs on the coast of Brazil. 1-5
Omura, H. Further informat!on on Bryde's whale from the coast of Japan. 7-18
Nishiwaki, M. Ryukyuan whaling in 1961. 19-28
Nemoto, T. A secondary sexual character of fin whales. 29-34
Omura, H., Nishiwaki, M., Ichihara, T. and Kasuya, T. Osteological note of a sperm whale. 35-45
Ichihara, T. Prenatal dead foetus of baleen whales. 47-60
Nishiwaki, M. Mesoplodon bowdoini stranded at Akita Beach, Sea of Japan. 61-77
Nishiwaki, M. Observation on two mandibles of Mesoplodon. 79-82
Sinclair, John. An early dolphin embryo (Stenella caeruleoalbus) in serial sections. 83-87
Nemoto, T. Food of baleen whales collected in recent Japanese Antarctic whaling expeditions. 89-103
Uda, M. Subarctic oceanography in relation to whaling and salmon fisheries. 105-119

NUMBER 17, FEBRUARY 1963
Nishiwaki, M., Ohsumi, S. and Maeda, T. Change of form in the sperm whale accompanied withgrowth. 1-14
Ohsumi, S., Kasuya, T. and Nishiwaki, M. The accumulation rate of dentinal growth layers in the
maxillary tooth of the sperm whale. 15-35
Ichihara, T. Photometric method for counting laminae in ear plug of baleen whale. 37-48
Yoshikawa, T. and Suzuki, T. The lamination of the masseter of the humpback whale. 49-52
Fujino, K. Intra-uterine selection due to maternal-foetal in compatibility of blood type in the whales.
53-65
Cushing, John E., Fujino, K. and Calaprice, N. The Ju blood typing system of the sperm whale andspecific soluble substances. 67-77
N<"moto, T. New records of sperm whales with protruded rudimentary hind limbs. 79-81
Nemoto, T. and Nasu, K. Stones and other aliens in the stomachs of sperm whales in the Bering Sea.
83-91
Nishiwaki, M. Taxonomical consideration on genera of Delphinidae. 93-103

vii
Nasu, K. Oceanography and whaling ground in the subarctic region of the Pacific Ocean. 105-155
Nemoto, T. Some aspects of the distribution of Calanus cristatus and C. plumchrus in the Bering and its
neighbouring waters, with reference to the feeding of baleen whales. 157-170
Tsuyuki, H. and Naruse, U. Studies on the oil of black right whale in the northern Pacific Ocean.
171-190
Yagi, T., Nishiwaki, M. and Nakajima, M. A preliminary study on the method of time marking withleadsalt and tetracycline on the teeth of northern fur seal. 191-195

NUMBER 18, MARCH 1964
Fujino, K. Fin whale subpopulations in the Antarctic whaling areas II, III and IV. 1-27
Ichihara, T. Prenatal development of ear plug in baleen whales. 29-48
Ohsumi, S. Examination on age determination of the whale. 49-88
Nemoto, T. School of baleen whales in the feeding areas. 89-110
Okutani, T. and Nemoto, T. Squids as the food of sperm whales in the Bering Sea and Alaskan Gulf.
111-122
Ohsumi, S. Comparison of maturity and accumulation rate of corpora albicantia between the left andright ovaries in cetacea. 123-148
Omura, H. A systematic study of the hyoid bones in the baleen whales. 149-170
Nishiwaki, M. Revision of the article "Taxonomical consideration on genera of Delphinidae" in No. 17.
171-172
Tsuyuki, H. and Naruse, U. Studies on the lipids in brain of black right whale in the northern Pacific
Ocean. 173-180

NUMBER 19, APRIL 1965
Ohsumi, S. Reproduction of the sperm whale in the north-west Pacific. 1-5
Kasuya, T. and Ichihara, T. Some informations on minke whales from the Antarctic. 37-43
Nemoto, T. and Kayuya, T. Foods of baleen whales in the Gulf of Alaska of the North Pacific. 45-51
Nishiwaki, M., Nakajima, M., and Kamiya, T. A rare species of dolphin (Stenella attenuata) from Arari,Japan. 53-64
Nishiwaki, M., Kasuya, T., Tobayama, T., Kamiya, T., and Nakajima, M. Feresa attenuata captured at
the Pacific Coast of Japan in 1963. 65-90
Nakajima, M. and Nishiwaki, M. The first occurence of a porpoise (Electra electra) in Japan. 91-104
Hosokawa, H. and Kamiya, T. Sections of the dolphin's head (Stenella caeruleoalba). 105-133
Ohsumi, S. A dolphin (Stene/la caeruleoalba) with protruded rudimentary hind limbs. 135-136

NUMBER 20, SEPTEMBER 1966
Ohsumi, S. Sexual segregation of the sperm whale in the North Pacific. 1-16
Ichihara, T. Criterion for determining age of fin whale with reference to ear plug and baleen plate.
17~82

Kasuya, T. Caryotype of a sei whale. 83-88
Kasuya, T. and Ohsumi, S. A secondary sexual character of the sperm whale. 89-94
Nishiwaki, M. and Norris, K. S. A new genus, Peponocephala, for the odontoceti cetacean species Electra
electra. 95-100
Nishiwaki, M., Nakajima, M. and Tobayama, T. Preliminary experiments for dolphin marking. 101107
Nemoto, T. Thysanoessa euphausiids, comparative morphology, allomorphosis and ecology. 109-155
Nasu, K. Fishery oceanographic study on the baleen whaling grounds. 157-210
Ichihara, T. and Nishiwaki, M. External measurements and weight of a southern elephant seal. 211212

viii
Tsuyuki, H. and Itoh, S.
221

Studies on the oils contained in blubber of a southern elephant seal.

213-

NUMBER 21, JUNE 1969
Omura, H., Ohsumi, S., Nemoto, T., Nasu, K. and Kasuya, T. Black right whales in the North Pacific.
1-78
Nishiwaki, M. and Hasegawa, Y. The discovery of the right whale skull in the Kisagata shell bed.
79-84
Ohsumi, S. Occurrence and rupture of varginal band in the fin, sei, and blue whales. 85-94
Hosokawa, H., Igarashi, S., Kamiya, T. and Hirosawa, K. Morphological characteristics and myelinization of acoustic system in the dolphins (Stenella caeruleoalba). 95-123
Mo!, T. and van Bree, P.J.H. A short contribution to the history of whaling in Japan during the 17th
century. 125-129
Tsuyuki, H. and Itoh, S. Fatty acid composition of finless porpoise oil. 131-135
Tsuyuki, H. and Itoh, S. Fatty acid composition of many toothed pilot whale oil. 137-141

NUMBER 22, JUNE 1970
Omura, H., Ichihara, T. and Kasuya, T. Osteology of pygmy blue whale with additional information
on external and other characteristics. 1-27
Nishiwaki, M. and Kasuya, T. Recent record of gray whale in the adjacent waters of Japan and aconsideration on its migration. 29-37
Kasuya, T. and Rice, D. W. Note on baleen plates and on arrangement of parasitic barnacles of graywhale. 39-43
Nishiwaki, M. and Kasuya. T. A Greenland right whale caught at Osaka Bay. 45-62
Nasu, K. and Masaki, Y. Some biological parameters for stock assessment of the Antarctic sei whale.
63-74
Ohsumi, S., Masaki, Y. and Kawamura, A. Stock of the Antarctic minke whale. 75-125
Kawamura, A. Food of sei whale taken by Japanese whaling expeditions in the Antarctic season 1967/
68. 127-152
Nemoto, T. and Yoo, K. I. An amphipod, Parathemisto gaudichandii as a food of the Antarctic sei whale.
153-158
Tobayama, T., Uchida, S. and Nishiwaki, M. Twin foetuses from a blue white dolphin. 159-162
Machida, S. A sword-fish sword found from a North Pacific sei whale. 163-164
Tsuyuki, H. and ltoh, S. Fatty acid components of black right whale oil by gas chromatography. 165170

NUMBER 23, SEPEMBER 1971
Ohsumi, S. Some investigations on the school structure of sperm whale. 1-25
Kawamura, A. Influence of chasing time to stomach contents of baleen and sperm whales. 27-36
Kasuya, T. Consideration of distribution and migration of toothed whales off the Pacific coast of Japan
based upon aerial sighting record. 37-60
Omura, H. A comparison of the size of vertebrae among some species of the baleen whales with specialreference to whale movements. 61-69
Omura, H., Nishiwaki, M. and Kasuya, T. Further studies on two skeletons of the black right whalein the North Pacific. 71-81
Nishiwaki, M. and Kasuya, T. Osteological note of an Antarctic sei whale. 83-89
Hosokawa, H. and Kamiya, T. Some observations on the cetacean stomachs, with special considerations
on the feeding habits of whales. 91-101

ix
Lugassy, A. A., Korostoff, E. and Rabinowits, J. L. Influence of incr.emental lines upon the compressive
strength of sperm whale dentin. 103-110
Nishiwaki, M. and Oguro, N. Baird's beaked whales caught on the coast of Japan in recent 10 years.
111-122
Mizue, K., Nishiwaki, M. and Takemura, A. The underwater sound of Ganges river dolphins (Platanista
gangetica). 123-128
Kasuya, T. and Nishiwaki, M. First record of Mesoplodon densirostris from Formosa. 129-137
Kawamura, A. and Kashita, K. A rare double monster of dolphin, Stenella caeruleoalba. 139-140
Tsuyuki, H. and Itoh, S. Fatty acid components of Ganges river dolphin oil. 141-147

NUMBER 24, NOVEMBER 1972
Omura, H. An osteological study of the Cuvier's beaked whale, <;,iphius cavirostris, in the northwest
Pacific. 1-34
Nishiwaki, M. and Oguro, N. Catch of the Cuvier's beaked whales off Japan in recent years. 35-41
Nishiwaki, M., Kasuya, T., Kureha, K. and Oguro, N. Further comments of Mesoplodon ginkgodens.
43-56
Kasuya, T. Growth and reproduction of Stenella caeruleoalba based on the age determination by meansof dentinal growth layers. 57-79
Kasuya, and Oguro, N. A new tagging method of dolphins. 81-85
Kasuya, T. Some informations on the growth of the Ganges dolphin with a comment on the Indus
dolphin. 87-108
Kasuya, T. and Aninul Haque, A.K.M. Some informations on the distribution and seasonal movementof the Ganges dolphin. 109-115
Tsuyuki, H. and Itoh, S. Fatty acid component of various blubber oil of Ganges River dolphin. 117-125
Naito, Y. and Nishiwaki, M. The growth of two species of the harbour seal in the adjacent waters of
Hokkaido. 127-144.
Ichihara, T. and Yoshida, K. Diving dt>pth of northern fur seals in the feeding time. 145-148

NUMBER 25, SEPTEMBER 1973
Kasuya, T. Systematic consideration of recent toothed whales based on the morphology of tympanoperiotic bone. 1-103
Omura, H. A review of pelagic whaling operations in the Antarctic based on the effort and catch datain 10° squares of latitude and longitude. 105-203
Nasu, K. Results of whale sighting by Chiyoda Maru No. 5 in the Pacific sector of the Antarctic andTasman Sea in the 1966/67 season. 205-217
Kawamura, A. Food and feeding of sei whale caught in the waters south of 40°N in the North Pacific.
219-236.
Ohsumi, S. Find of marlin spear from the Antarctic minke whales. 237-239
Seki, Y. An anatomical study on the lower extension of the dorsal vagal nucleus to the upper cervical
cord in the sperm whale. 241-249
Tobayama, T., Nishiwaki, M. and Yang, H. C. Records of the Fraser's Sarawak dolphin (Lagenodelphis
hosei) in the western North Pacific. 251-263
Miyazaki, N., Kusaka, T. and Nishiwaki, M. Food of Stenella caernleoalba. 265-275
Nishiwaki, M. Possible vestigial teats of killer whale. 277-278
Williamson, G. R. Counting and measuring baleen and ventral grooves of whales. 279-292
Tsuyuki, H. and Itoh, S. Fatty acid component of blubber oil of Amazon River dolphin. 293-299
Naito, Y. Comparison in colour pattern of two species of harbour seal in adjacent waters of Hokkaido.
301-310x

NUMBER 26, NOVEMBER 1974
Omura, H. Possible migration route of the gray whale on the coast of Japan. 1-14
Satake, Y. and Omura, H. A taxonomic study of the minke whale in the Antarctic by means of hyoidbone. 15-24
Kawamura, A. Food and feeding ecology in the southern sei whale. 25-144
McCann, C. Body scarring on cetacea-odontocetes. 145-155
Kasuya, T., Miyazaki, N. and Dawbin, W. H. Growth and reproduction of Stenella attenuata in the
Pacific coast of Japan. 157-226
Miyazaki, N., Kasuya, T. and Nishiwaki, M. Distribution and migration of two species of Stenella in
the Pacific coast of Japan. 227-243
Kamiya, T. and Pirlot, P. Brain morphogenesis in Stenella coeruleoalba. 245-253
Castello, H. P., Torno, A. P. and Panizza, J. S. First Antarctic record of a killer whale stranding. 255258
Kamiya, T. and Miyazaki, N. A malformed embryo of Stenella coeruleoalba. 259-263
Kamiya, T. and Yamasaki, F. Organ weights of Pontoporia blainvillei and Platanista gangetica (Platanistidae). 265-270
Machida, S. Surface temperatme field in the Crozet and Kerguelen whaling grounds. 271-287
Machida, S. The voyage of the Konan Maru No. 16 to the Antarctic whaling grounds. 289-302
Itoh, S. and Tsuyuki, H. Fatty acid component of different blubber oil of finless porpoise. 303-306
Itoh, S. and Tsuyuki, H. Fatty acid component of Senegal manatee fats. 309-311.
Naito, Y. The hyoid bones of two kinds of harbour seals in the adjacent waters of Hokkaido. 313-320

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