THESCIENTIFIC REPORTS
OF

THE WHALES RESEARCH INSTITUTE
No. 29THE WHALES RESEARCH INSTITUTETOKYO· JAPANDECEMBER 1977l~Res. Inst., No. 2.9

!

~

THE
SCIENTIFIC REPORTS
OF
THE WHALES RESEARCH INSTITUTE

No. 29THE WHALES RESEARCH INSTITUTETOKYO, JAPANDECEMBER, 1977

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

THE SCIENTIFIC REPORTS OF THE WHALESRESEARCH INSTITUTE
CONTENTS OF NUMBER 29Page

KASUYA, T.
Age determination and growth of the Baird's beaked whale with a comment on
the fetal growth rate ................................................. .
MIYAZAKI, N.
On the growth and reproduction of Stenella coeruleoalba off the Pacific coast ofJapan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
KAWAMURA, A.
On the food of Bryde's whales caught in the South Pacific and Indian Oceans. .

49

HERMAN, L. M. and R. C. ANTINOJA.
Humpback whales in the Hawaiian breeding waters: population and pod characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

59

AMINUL HAQUE, A.K.M., M. NISHIWAKI, T. KASuYA, and T. ToBAYAMA.
Observations on the behaviour and other biological aspects of the Ganges susu,
Platanista gangetica. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

87

YAMASAKI, F., S. KoMATsu, and T. KAMIYA.
A comparative morphology of anal tonsils in Platanistidae. . . . . . . . . . . . . . . . . .

95

NEMOTO, T., R. L. BROWNELL, Jr. and T. lsHIMARU.
Coconeis diatom on the skin of Franciscana ................................ 101
CASTELLO, H. P.
Fobd of a killer whale: Eagle sting-ray, Myliobatis found in the stomach of a
stranded Orcinus orca . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . 107
NisHIWAKI, M. and A. SAsAo.
Human activities disturbing natural migration routes of whales. . . . . . . . . . . . . . 113
YosHIDA, K., N. BABA, M. OYA, and K. MIZUE.
On the formation and regression of corpus luteum in the northern fur sealovaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
ABE, H., Y. HASEGAWA, and K. WADA.
A note on the air-sac of ribbon seal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
KAWAMURA, A. and T. FuRuNo.
On the northern extreme of the pack-ice edge observed by whaling vessels inthe summer of the Antarctic seasons 1957/58-1962/63 ...................... 137

目 次
粕谷俊雄
ツチクジラの年齢査定に関する研究，胎児の生長速度に関する考察
宮崎信之
日本の太平洋沿岸産スジイルカの生長と繁殖

2
1

河村章人
南半球産ニタリクジラの食性について

49

Herman,L.M.andR.C
.A
n
t
i
n
o
j
a
.
ハワイ繁殖水域におけるザ、トウクジラ：その資源と群の性質

59

AminulHaque,A.K.M.・西脇昌治・粕谷俊雄・鳥羽山照夫
ガンジスカワイルカの生態に関する観察．．
山崎英雄・小松俊郎・神谷敏郎
カワイルカ類の紅門扇桃について87
95

根本敬久• R
.L
.B
r
o
w
n
e
l
l
,J
r
.・石丸隆

ラプラタカワイルカの附着珪藻．−−

1
0
1

C
a
s
t
e
l
l
o
,H.P.
シャチの胃から発見されたトピエイについて

1
0
7

西脇昌治・笹尾昭信
人間活動の鯨類回瀞路の妨害について113

吉田主基・馬場徳寿・大矢真知子・水江一弘
オットセイの黄体の運命．

1
2
1

阿部永・長谷川善和・和田一雄
クラカケアザ、ラシの空気嚢について

1
2
9

河村章人・吉野輝彦
夏季南氷洋捕鯨漁場におけるパックアイスの北限 1
9
5
7
/
5
8〜1
9
6
2
/
6
3

1
3
7

AGE DETERMINATION AND GROWTH OF THE BAIRD'S
BEAKED WHALE WITH A COMMENT ON
THE FETAL GROWTH RATETOSHIO KASUYA
Ocean Research Institute, University of Tok_vo, Tokyo

ABSTRACTTwo kinds of cycles exist in the alternation of the stainability of dentine
and cementum of the species. The longer is of annual, and the stainable layer
is deposited from August to January and the unstainable in the rest of theyear. The shorter cycle ranges from 27 to 31 days with possible individual
variations. The deposition of dentine ceases within several years after birth,and the short cycle is distinguishable in the first few annual layers. In cementum, on the other hand, the annual layer is possibly formed for all thelife time, and the short cycle on the anterior tooth until 40 to 60 years of age.
The length oflife time is 70 years. The gestation will last for about 17 months,
one of the longest among the cetaceans ..
INTRODUCTION

The morphology and life history of the Baird's beaked whale, Berardius bairdii Stejneger, 1883 in the western North Pacific and adjacent seas were studied by Omura
et al. (1955) based on the catch statistics of the Japanese commercial whaling in the
period from 1~48 to 1952 and on many specimens investigated by them. Later
Nishimura (1970) discussed the distribution of the species in the Sea of Japan basedon several stranded animals. Nishiwaki and Oguro (1971) analysed the statistics
of Japanese catch of the species in the years from 1965 to 1969. In recent years,
the catch of B. bairdii is mostly restricted, by the economical factors, to the coastal
waters of the Boso Penninsula on the Pacific coast of central Japan, and the annual
catch seems to be less than 30 whales (Dr. Y. Naito, person. comm.).
In spite of the effort of these authers, very little is known about the life historyof the species. The main obstacle in the study exist in the difficulty in obtaining theadequate number of samples and in the absence of the age determination technique.
Though, Omura et al. (1955 ), studying the anatomy of the tooth of B. bairdii, indicatedthe presence of the annual layers in cementum and suggested the possibility of theage determination, they did not show the reason for the conclusion nor try to estimate the age of the whales. The present study was made in order to reconsider
their study and provide some clue of the age determination of the species.

Sci. Rep. Whales Res. Inst.,

No. 29, 1977, 1-20.

2

KASUYA

MATERIALS AND METHOD

Nineteen samples, in the twenty used in this study, were collected from the catch ofcoastal whaling off the Boso Penninsula (35°N, 140°E), of which 18 animals by
Omura in 1957 through the cooperation of the Takai Gyogyo Co., Ltd, and anothersample WD-9 by Dr. Y. Naito. Whale no. 20 was collected at an whaling station
at Ayukawa (38° 20'N, 141° 30'E) on the Pacific coast of Japan through the field
investigation of the Whales Research Institute.

TABLE l.

Tooth

Whale
no.

Date of catch

4-, - ''57
13, Oct., '59
5, Aug., '57

9.8m
10.8m

6.4 , 5.8
0.44 , 1.55

6, Aug., '57

10.6m

4.10 , 4.10

8, Aug., '57
15, Aug., '57

11. l m10.6m

5.20 ' 5.30
4.80 , 4.90

16, Aug., '57

10.9m

4.70, 5.80

18, Aug., '57
27, Aug., '57

ll.4m
10.7m

0.205, 0.245
4.10, 3.90

28, Aug., '57

10.7 m8.20 ' 8.20

30, Aug., '57
30, Aug., '57

10.7m
10.8m

5.60 , 5.80
7.00, 6.90

1, Sept., '57

7.8m

0.40 , 0.36

1, Sept., '57
15, Sept., '57
14, Oct., '57

10.4m
6.4m
10.1 m0.320, 0.275
0.062, 0.060
5.50 , 5.50

15, Oct., '57

10.8m

7.00, 9.80

6, Nov., '57

11.0m

0.235, 0.245

14, Nov., '57

l0.7m

1.20, 1.15

4, Aug., '76

10.5 m

20
365>
36
377>
37
38
40
40
41
41

44
49
49
50
50
51
52
52
53
53
54
55
57
57
58
58
60
60
61
61
WD-9

LIST OF MATERIALS

Body length

Sex

if

Gonad 10> (kg)3.62 , 4.94

position1>

thicknessheight

Post.
Ant.
Ant.
Post.
Ant.
Post.
Post.
Ant.
Post.
Ant.
Post.
Ant.
Ant.
Post.
Ant.
Post.
Ant.
Ant.
Post.
Ant.
Post.
Post.
Ant.
Ant.
Post.
Ant.
Post.
Ant.
Post.
Ant.
Post.
Ant.

16mm
26mm
35mm
15mm

48mm
73mm
81 mm
49mm
76mm

13mm
21 mm
28mm
16mm
34mm
18mm
32mm
34mm
14mm
34mm
15mm
43mm
36mm
18mm
33mm
16mm
18mm
32mm
35mm
20mm
4lmm
18mm
35mm
18mm
39mm
18 mm
32 mm

52mm
73mm
48mm
89mm
90mm
84mm
80mm
51 mm
56mm
47mm
68mm
79mm
64mm
86mm
5lmm
62mm
66mm
74mm
50mm
84mm
57mm
85mm
59mm
90mm
60 mm
67 mm

2> - : Not erupted, + : Erupted and osteodentine
covered, •> In parentheses: Pulp cavity filled with osteodentine, Italics: No. of annual layers (long78> 30 shortPregnant with 12 mm fetus (Omura, 1958), physically mature.
> Physically immature.
All the testes, except for the whale no. 20, were weighed by the Tokai Gyogyo Co., Ltd., and the ovaries
1> Ant. : Anterior tooth, Post. : Posterior tooth.

Sci. Rep. Whales Res. Inst.,

No. 29, 1977.

3

AGE DETERMINATION OF BERARD/US

The body length recorded by foot (0.305 m) or shyaku (0.303 m) was converted into metric system. The records of sex and weight of gonad were obtained
directly by the biologist or by the whaling company as in the case of the body length.
Teeth of 19 whales, other than that of WD-9, were preserved in dry condition
after cleaning by boiling. Each tooth was cut on a lingua-buccal medial plane,
and one 2 to 3 mm section was taken with a saw. Then, usually, either lingua or
buccal half of the section was polished with whet stones and glued on a clear plastic plate. The other side was polished with the same way to a thickness between

USED IN THIS STUDY
No. of long cycles 4l
attrition2l

+
-tt

+
+
-tt
-tt

+
+
+
+
+
-tt

+
-tt

+
+
+
-tt

+
-tt

+
-tt

+
+
+
-tt

root8lin dentine

in cementum

closedclosedclosedclosedclosedclosedclosedclosedclosedclosedclosedclosedclosedclosedclosedclosedclosedclosedclosedopen
openclosedopen
closedclosedclosedclosedclosedclosedclosedclosedclosed[5][7]

38, 44, 46
40, 41, 42
35, 36, 38
30, 33, 35
16, 17, 17
17, 17, 17
25, 26, 27
56, 57, 61
56, 58, 63
40, 47, 51"
37, 40, 40
22, 25, 29
20, 21, 22
23, 23, 24
66, 67, 71
54, 67, 68
68, 71, 72
29, 30, 31
30, 30, 32
3, 3ai, 3
3, 3, 335, 36, 37
2, 2oi, 2
51, 58, 59
49, 51, 56
50, 50, 52
46, 47, 48
37, 39, 40
44, 46, 51
40, 40, 41
37, 39, 41
64, 65, 66

[4]
[5]
[6]

[4]
[7]
[5]
[5]
[4]
[5]
[5]
[5]
[6]
3
3
[7]
2
[6]
[6]
[5]
[5]
[6]

Age with
completeshort cycle

Last Jong
cementa! cycle6J

~41
~36

Unstainable (wide, -)Stainable(thin, 2)
Unstainable (wide, 7)~17Unstainable (wide, 7)~57

Unstainable (wide, -)Stainable(thin, 2)~47

Stainable(thin, I)~25~21

Stainable
Stainable(wide, 3)(thin, 2);;;;52

Unstainable (wide, - );;;;42~30

Unstainable (wide, -)Stainable(thin, I)~

Stainable(wide, 3)~

Stainable
Stainable(thin, -)(thin, 2)~50

Stainable(wide, 3)~39

Stainable(wide, 3)~40

Stainable(wide, 4);;;;56

Stainable(thin, -)3

2;;;;57

not exposed, -t+ : Osteodentine exposed, si Closed: Root covered with cementum, Open: Root notcycle) used in other part of this study. 5l In parentheses number of short cycles if observable. 6)
10)cycles in cementum and 31 in postnatal dentine. 9J 22 short cycles in dentine and cementum.
by Dr. H. Omura after the fixation in 10% formalin.

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

4

KASUYA

40 µm to 70 µm. The thin ground section was decalcified in 5% formic acid forseveral hours, stained with Mayer's haematoxylin solution for 30 minutes and mounted with permanent mounting medium. In case of the tooth of WD-9, which was
fixed in 10% formalin, the section was at first step embedded in polyester resin,
and then processed with the same method to a thinner decalcified and stained preparation. Its thickness was about 25 µm. This method did not give different
result except for the technical convenience to produce thinner section. Manyother ancillary thin preparations (10 to 15 µm) were made from small pieces of
cementum, and used for limited observations.
The observation of the growth layers was made with a microscope ( X 40 and
X 100) under transmitted light, and counting was always made on the stainable
layers.
Though, the same process was made, if available, on both anterior larger toothand posterior smaller tooth, the latter was used for restricted purpose. If it is not
specified, in the latter part of this study, the analysis are for anterior tooth.
RESULT

Grozvth of the tooth
About 80% of individuals of B. bairdii have two pairs of mandibular tooth,and the rest of animals more (Kirino 1956). The tooth is shaped of a bilaterallycompressed cone, and the fundamental structure is same for both the anterior andposterior tooth (Pl. I). In case of the unerupted tooth, the cusp is covered withthin enamel layer, as already indicated by Omura et al. (1955) on a fetal tooth. The
enamel layer of the postnatal individuals is often covered with cementum (Fig.

1).
Beneath the enamel layer there are dentinal layers and large pulp cavity. Thispulp cavity is later filled with osteodentine arid only narrow root canal, which isconnected to the outside of the tooth through the thick cemental layer, is often left

Fig. I. Schematic figure of the lingua-buccal section of the tooth of B. bairdii.
1 : Enamel. 2 : Cementum, only three layers are indicated. 3 : Feta! dentine.
4 : Postnatal dentine. 5 : Osteodentine. Alphabets indicate the positions forcounting the layers used in Figs. 2 and 3.

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

AGE DETERMINATION OF BERARD/US

5

in case of the older animals.
The cementum covers almost the entire length of the lateral surface of the toothof postnatal animals. In young individuals such as nos. 53 and 55, of whichages are estimated in the later part of this study to be about 30 months, and 21 months
respectively, the osteodentine is exposed on the base of the tooth, however, in theolder animals, the root is covered with cemental layers. This stage is classified
into the" closed" state in Table 1. This definition is different from that of Omura
et al. (1955 ), where the root was considered to be closed if the osteodentine fills thepulp cavity. The closure of the root seems to occur at the age between 3 and 17
years.
The eruption of tooth was recorded at the whaling station and it was confirmedin the laboratory using, if necessary, a microscope. The eruption is considered tooccur in relation to the attainment of sexual maturity (Omura et al. 1955). The
present scanty materials suggest that the eruption of anterior tooth occurs at anage between 3 and 17 years, and the posterior smaller tooth between 21 and 30.
The sexual difference of the eruption was not detected in this study. Matsuura(1942) considered that the posterior tooth of the female does not erupt, however,the present data, whale nos. 36 and 60, indicate that the posterior tooth of female
also erupt at some age as already indicated by Kirino (1956).
Dentinal growth layers

As shown in Fig. 1 and Plate I, the outermost layer of the dentine is the fetal
layer. This is the largest in the thickness, and the length of the contour is longest
next to the first postnatal dentinal layer. There are observed obscured layered
structures in the fetal dentine both in the thin ground section and in decalcified
and stained section. Though most of the layers in the prenatal dentine are obscure, several contiguous layers are clear in most of the individuals (Pl. II). These
clear layers are formed at the various stage of the deposition of the prenatal dentine, and the number of the clear layers is usually from 3 to 7 with 2 exceptional
cases of 0 and 12 layers (13 individuals examined). The condition is same in theanterior and posterior tooth of the same individual. The total number of the layers in the prenatal dentine has a mode at 14 layers (Table 2).
The postnatal dentine is separated from the fetal dentine by a thin clear
unstainable layer, and distinguished from the latter by the good stainability andclearer fine layers in it. Though the postnatal dentinal layers are irregular and
TABLE 2.

FREQUENCY DISTRIBUTION OF FINE LAYERSIN PRENATAL DENTINE
Frequency

No. of layers
anterior tooth

posterior tooth

12
13

14
15

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

1
3

3
2

6

KASUYAthe counting is difficult, there are observed two kinds of accumulation cycles. The
one is of long interval, which possibly corresponds to the annual growth layers ofthe dolphins and sperm whales studied by Ohsumi et al. (1963) and Kasuya (1976).
These layers decrease in length and thickness in accordance with the progress ofdeposition, and the last layer is observed only near the apex of the pulp cavity. The
number of these long cycle layers is between 4 and 7 layers on either anterior orposterior tooth where the pulp cavity is completely filled with osteodentine, clearly
showing the end of the deposition at those ages (Table I).
In the postnatal dentine, there are observed many alternation of stainability possibly reflecting the physiological changes of the shorter cycle. These layers
are most conspicuous in the dentine deposited in the younger stages, and are almost
indistinguishable in the 5th to 7th layers oflong cycle described above. It is notable that in the anterior tooth of the whale no. 53 there are observed 31 small layers
in the 3 long cycle layers, and 22 small layers in the 2 long cycle layers of the anterior tooth of whale no. 55 (Pl. II).

Cementa! growth layers
There are observed two kinds of cycles in the alternation of the stainabilityof cementa! groundsubstance, as in the case of dentinal layers. The one is oflonger
interval and the other the shorter. In other words, the stainable and unstainable
layers of the long cycle are, usually, composed of several short cycles, and the cyclicchange of the stainbility of these short cycle layers constitutes the long cycle (Pls.
II and III). The cementocytes are diffusedly distributed at all the part of thecementum, and there is detected no relationship between its arrangement and thestainability of the cementa! groundsubstance.
As the deposition of the cementum is restricted, after the eruption, to the proximal part of the tooth, the count of the cementa} layers must be made for the correct age determination on the area connecting the lateral margin of the fetal den-

~

50

"jr

II

,.!?

' '
I I

0

~

>-

40

fA\.. ,,

u

c 30

,.,.

l!J

:;,

CJ"
l!J

... 20u..
/10,,/+,,''
,

'

+'

/'~
, I

\',

\~

.I

I

''

"i-

,.+

0-----0-.----0

0

80

90

/

100

110

'

120

Deviation in °lo
Fig. 2. The variation of the counts oflong cycle cemental layers. Closed circle andsolid line indicate the anterior tooth, open circle and dotted line the posterior
tooth, and cross mark and chain the ratio of the number of layers in posterior
tooth to that in anterior tooth of the same animal.

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

AGE DETERMINATION OF BERARDIUS

7

tine and the external margin where the layer of cementoblasts is present. In thepresent study, the cementoblasts were still observable on the section prepared fromthe tooth preserved for many years in dry condition.
The number of the long cycle cemental layers shown in Table 1 was counted
on the area corresponding to" C" in Fig. 1, where the cementa! deposition is most
rapid and the two kinds of cycles are most clearly recorded. Usually three counts
were made independently and a value at their middle was taken as the numberof the cycles. The fluctuation of other two counts expressed by the percentage ofthe central value are shown in Fig. 2. It is usually within the range of 15% ineither case of anterior or posterior tooth. The diversity between the anterior andposterior teeth of a same whale was expressed by the ratio of the two central values.
Most of the difference is also found within the range of 15%. However, as thereading of the layers in the posterior tooth is difficult, its data is used only when theanterior tooth is not available.

99
Whale no. 37--<>--

B

Whale no. 52

95
90

fC J>B
A

,IJ
0

~

I
I
I

~

80

,,,_ ---0'~~..o- - -o- - -o""'

<Ii

>

~

5 60

I

f'

I

'3

I
I

§ 40

/

.t:J

P'

u

I
I

I

20

I

I

I

10
5

I

A'0

c

B

11

2

3 4

5

6

7

8

9 10 11 12 13 14 15

No. of short cycles
Fig. 3. Probability plot of the frequency distribution of the number of short cycles
in a long cycle cementa! layer. Alphabets indicate the position shown in Fig. I.

The short cycle alternation of the stainability of cementum of the anterior
tooth is analysed below. Fig. 3 shows the probability plot of the frequency of thenumber of fine layers in one long cemental cycle. If the number of the fine layers isnormally distributed, the cumulative frequencies plotted in this way lie on a straightline. It seems that the points corresponding to 10 or more short cycles come on astraight line and considered to be normally distributed. However, the frequencyof the long cycle layers which contain 9 or less fine layers is not normally distributed
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

8

KASUYAand the abundance of such long cycle layers decreases from the distal portion to thebase of the tooth. This may suggest the next two possibilities, one is that the shortcycle is not fully recorded nor distinguished on the distal part of the tooth where
the deposition of the cementum becomes slower at earlier age, the second is thatthe distinction of long and short cycles is not correctly done at the distal part of the
tooth.
Fig. 4 will solve the above question. In this figure, the numbers of short cycles in one long cycle are arranged in the order of their deposition. As the first and

14

12

~ 10

u>-

u

6 8

.c
Ill

0
d

z

I
I
I

c

B'I
I

6

I

I

4I

6

I

I
I
I

4

""-<i

\

'~
\,

2

30

20

JO

0

No. of long cycle

105Frequency

Fig. 4. Age and locality difference of the number of short cycles in a long cycle
cementa! layer, whale no. 52. Alphabets indicate the position shown in Fig. I.

Whale no.
Sex
No. long cycles present
No. long cycles checked
No. short cycles
9
10
11
12
13
14
15
16
17
mean
Mean days in a short cycle 2>
1>

Mean of the 13 mean values.

TABLE 3.

FREQUENCY DISTRIBUTION OF NUMBER OF

55

53

~

6

6

6

6

~

1.8

2.4
2

17
16

21
19

30
30

37
16

3
9
8
9

3
4
7

37

4
3
4
4

12.0
30.4
2> 365

12.0
30.4

12.7
28.8

49

8
5
2
2

13.0
28.2

52

60

2

12.7
28. 7

12.6
28.9

days are assumed for long cycle.
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

AGE DETERMINATION OF BERARDIUS

9the last layers are incomplete, they are not adequate for the present discussion. The
disagreement of one layer between the number of long cycles distinguished at distal
area (B) and proximal area (C) is within the reasonable range of the error. Then
Fig. 4 indicates that in the proximal portion of the tooth, about 10 to 14 short cycles are distinguished in every long cycle cemental layers, and that the same numberof cycles are present in the distal portion only up to the age of 22 long cemental
cycles. After this age the number of short cycles observed in the distal portion
rapidly decreases. This was confirmed by the direct tracing of some long cycle
layers, in which higher number of short cycles are observed in the proximal portion
but only lower number in the distal portion. The thinner section, about 20 µm, ofthe latter part could not increase the number of observable short cycles. Accordingly, it will be safe to conclude that, after a certain age, the deposition of cementum
becomes slower at the distal area of the tooth and the alternation of the stainabilityof short cycle is not fully recorded. This change will progress towards the proximal
portion in accordance with the progress of the eruption of tooth. This is supported
also by the fact that the number of long cycle layers where the complete number ofshort cycles are clearly recorded is very few on the posterior tooth. As the cementa!
layers are thin on the posterior tooth, the growth must be slower than the anterior
tooth.
In order to estimate the relative length of the accumulation cycles of long andshort cycle layers, the number of short cycles was counted on several contiguous
long cycle layers at the selected position of 13 anterior teeth. As shown in Table
3, the fluctuation of the number of short cycles in one long cycle layer is wide. Thisis partially because the alternation of the stainability of long cycle is gradual andthe distinction of each long cycle layer is not very definite. Accordingly, if one
long cycle layer contains a relatively small number of short cycles the next long
cycle layer often gives the higher count, and the reliability of the mean value inTable 3 might be higher than that expected from the fluctuation. The range of
SHORT CYCLES IN A LONG CEMENTAL CYCLE OF B. BAIRD!!

20

41

58

40

57

50

51

J

J

J

J

J

J

J

41
7

47
7

50
21

57

58
13

67
15

71

2
3
4

12.7
28.7

12.0
30.4

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

11

4
3
4
6
4

5
3
2

3
3
5
2

4
7
3

12. l
30. l

11.9
30.6

12.5
29.3

12. l
30.2

11

2
4
4

13.4
27.3

Total

169

100%

8
28
47
43
31
6

4.7
16.6
27.8
25.4
18. 7
3.5
0.0
0.6
12.41>
29.4 1>

12. l
30.1

KASUYA

10

the mean values is between 11.9 and 13.4 short cycles per one long cycle, and there
is detected a significant difference of the mean values between some of the individuals as indicated in Fig. 5 and dealt with in the next section. The mean for the
13 whales is 12.4 short cycles per a long cemental cycle.
The number of short cycles constituting one stainable layer of long cycle wascounted in 15 anterior teeth with from 5 to 10 long cycle layers each, and shown in
Fig. 6. The mean counts per long cycle layer of each individual lie between 5.0
and 6.9 cycles, and the mean number of the short cycles calculated for all of the 86
data is 5.86 cycles. This result indicates that the stainable and unstainable layerof the long cycle represent approximately the same length of time, but only if eachlayer of short cycle represents equal time periods.
The age when the deposition of full number of short cycle layers (~ 10 layers)ceases in the cementum of anterior teeth is estimated from the direct observation of=--_ -

3

"'"'

Gl

r~1

r~1

~*1
N

I

<'> <D

r~~o

H.
29

"'"'
I

I

-

"'"'

~l

28
30
Length of short cycle (days)
Fig. 5. Individual variation of the mean length of short cementa! cycles. Numerals in the squares indicate the whale number, and the line the combination
where the difference is statistically significant (p<0.05 ).

40
~

t

30

>-

u

c 20

~

g...

u..

10

.·.·.·.·......-:·-:-:·:·:·:·:·:-:-:·:·:::::::::::::::::::::::.·:..:

57..

0'----'-~~'---~-"":..:.:.::..:.:.::.:i.:.::uJ..-1:.LJ..1_~-L--l

3

4

6

8

Number of short cycles
Fig. 6. Variation of the number of short cycles in a long cycle stainable layer inthe cementum. Solid line and closed circle indicate the frequency, and dotted
area the distribution of the mean values of each animal. Mean and the rangeof 2 standard errors are indicated at the top.
Sci. Rep. Whales Res. Inst.,

No. 29, 1977.

AGE DETERMINATION OF BERARDIUS

11

the teeth (Table 1). The youngest age when the short cycle layers deposition ceases
is 39 long cycle layers, and the cumulative frequency of such animals increases withthe age. The oldest animal found to be still forming the full number of the shortcycle cemental layers is 57 long cycle layers and the cumulative frequency increases
in the younger age. The two cumulative frequencies become equal at the age of
49.5 long cycle layers, which is the mean age at the cessation of the deposition ofcomplete number of short cycle cemental layers.

Seasonal alternation of the layers
The condition of the last cemental layer, concerning the long cycle, was analysed in relation to the date of the catch. As shown in Tables 1 and 4, there areobserved two kinds of layer states at equal abundance in August. One is in theprocess of forming the unstainable layer on the outer margin and the other stainable layer. The thickness of the former layer is large and the number of short cycles
in it is 7 cycles in 2 countable cases. Whereas the thickness of the latter layer isthin and the number of short cycles in it is only 1 to 3 cycles in August. All the
TABLE 4.

Stainable

Unstainable
wide

Month
Aug.
Sep.
Oct.
Nov.
1>

SEASONAL CHANGE OF THE CONDITION
OF THE LAST CEMENTAL LAYER1>
Total
thin

5

wide

5
2

11

3
2
2

l

2
concerning the long cycle

13

12.4

11

i

9

i 7
VJ

0

5.9

d

z

/

5

/

3

D

F

M

A

M

A

Month

Fig. 7. Seasonal variation of the number of short cycles in the last incomplete long
cycle cemental layer. Closed circle and solid line indicate the stainable long cycle
layer, and open circle and dotted line the unstainable. Mean number of shortcycles in one long cycle and that in one long cycle stainable layer are indicated.
For further explanations see text.

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

12

KASUYA

seven whales killed after August were depositing the staniable layer of long cycle,
and the thickness seems to increase with the progress of the season. It is safely
concluded, from these informations, that the alternation of the layer from the unstainable to the stainable, occurrs, in the average, in August.
As the present sample is restricted to 4 months, it is impossible to detect theseason when the deposition of the stainable layer of the long cycle ceases and thatof unstainable layer starts. However, the analysis of the seasonal increment of theshort cycle layer gives a suggestion for it. In Fig. 7, the number of short cycle layers
in the last incomplete long cycle layer is plotted against the date of death. The
two whales, nos. 36 and 37, which were accumulating the unstainable long cycle
layer in August, are extended forward by 12 months and the number of short cycles in the preceding stainable long cycle layer was added. Then the linear regression was calculated by the least squares for the 8 whales, excluding the 5 whales
killed in August, that had recently started the deposition of the stainable layer.
The inclusion of these whales will cause a bias toward the higher number of shortcycles, because half of the whales are still accumulating the unstainable long cycle
layer in August. The regression is shown by
y = 0.03184x+0.58
where x indicates the days from the first of August and y the number of short cycles
accumulated since the start of the last stainable long cycle layer. It is, in a strict
sense, incorrect to project the two whales for 12 months, because the accumulation
rate of the long cycle is not proved to be 12 months. However the annual accumulation of the long cycle is considered to be correct based on the following reasons.
1. The gradient of the regression fits to the data of September and November,and other gradients assumed for the cycles shorter than one year do not.
2. If the length of the cycle longer than 1 year is assumed, there must be observed more varieties in the condition of cemental layers being accumulatedin August and September.
Above regression indicates the accumulation of one short cycle in 31.4 days, and12.4 short cycles, the mean number in one long cycle, in 389 days. This is sufficiently within the range of error for the conclusion of the annual formation of thelong cycle cemental layers. The alternation from the stainable long cycle layer tothe unstainable seems to occur in January. In other words, the long cycle stainable
layer is formed in the season when the length of the daytime decreases, and the unstainable in the opposite season. This seasonal alternation is similar to that of the
spotted dolphin studied by Kasuya (1976) except for the slightly earlier change in
B. bairdii.
When the annual cycle is assumed for the long cemental cycle, the mean lengthsof short cemental cycle of 13 whales come in the range of 27.3 to 30.6 days (Table
2). As shown in Fig. 5, the difference of the mean length of the cycle is significant
between some animals (p<0.05), and there are expected the presence of 4 modes
at 27, 28, 29, and 30 or 31 days. However it will be safe to retain the definite conSci. Rep. Whales Res. Inst.,

No. 29, 1977.

AGE DETERMINATION OF BERARD/US

13

clusion on this problem until the study is made on more animals, because the individual variation in the readability of the short cycle layer may influence the result.
In the natural environment, such a cycles which may cause the 29 or 30 days
cycle of the cemental deposition seems to be the lunar cycle. For the check of thisproblem, the comparison between the state of the outermost cementum and thelunar cycle of the day of catch was made on selected 13 animals using the thinly prepared section (10 to 15 µm). However it gave a negative result. The stainable
or unstainable layer of short cycle is considered to be formed at any period of a lunar
cycle. Though more study is needed on this problem, it is probable that the shortcycle is not a direct reflection of the environmental change, but a cycle hereditarily
decided individual specific cycle just as the menstrual cycle of some of the female
primates. This hypothesis can support the presence of the individual variation in
the length of short cycle.
DISCUSSION AND CONCLUSION
In the present study no tooth offetus or of newborn calf was studied. This obstructed
the conclusion on the start of the deposition of cementum and on the relative rateof the formation oflayers in dentine and cementum. However, Omura et al. (1955)
studied the anatomy of the tooth of9 feet, 2.7 m, fetus which had no cemental layer
on it. The observation on the cementum of postnatal individuals showed that there
is no clear layer such as neonatal line observed in dentine, and that the numbers ofshort and long cycles in cementum and postnatal dentine are almost same in theanterior tooth of young whales, nos. 53 and 55. In case of the dolphins, Stenella
attenuata and S. coeruleoalba, the cementum is lacking on the tooth of fetal or newborn
animals on which no postnatal dentine is deposited (Kasuya 1976, Kasuya unpublished), and it was considered that the cementum is laid down soon after the birth(Kasuya 1976). Accordingly I conclude that the deposition of cemental layer
will start in B. bairdii soon after the birth as in the case of other odontoceti, and thatthe accumulation cycle of dentinal layers is fundamentally the same as that of cementa! layers except for the earlier cessation of the accumulation in the former
tissue. In order to estimate the age of the young animals of the species, it will be
accurate to count both the long cycle layers (annual) and the short cycle layers(about 29.4 days) in dentine and cementum. However it is practical, in case ofanimals older than 3 years of age, to count the annual cemental layers. The ageof the oldest animal thus estimated is 71 years, and seems to be reasonable compared with the same figure of the female sperm whale 64 years (Ohsumi et al. 1963).
The present study suggests that the short cycle layering in the postnatal dentine
and cementum is probably caused by a genetic physiological cycle of about 29.4
days in the average. However, the effect of the lunar cycle is still left to be studied.
The long cycle layer is formed by the enhancement of some of the short cycle layers,which seems to be caused by the annual cycle of the physiological condition possibly relating to some environmental changes. As the cause of the formation of thelayers in the prenatal dentine, both the genetic physiological cycle (29.4 days in theSci. Rep. Whales Res. Inst.,
No. 29, 1977.

14

KASUYAaverage) of the fetus and of the mother can be expected. If the both factors work at
the same intensity and the length of the cycle of the mother and of the fetus is equal,
all the prenatal dentinal layers can be obscure by the complete masking of the opposite phases or can be clear by the complete or partial overlapping of the same phase.
However, if the lengths of the cycle is not equal, the complete coincidence occurs
once in the 27 to 31 cycles and the nearby several layers will be seen clear. Amongthe present materials, the prenatal dentinal layers of the whale no. 4 are almost
completely obscure, in the whale no. 40 so many as 12 layers are clear, and other11 individuals had 3 to 7 clear layers in the prenatal dentine. These facts can be
explained by the above hypothesis, if the length of the gestation of the species isabout 17 months as suspected from the fetal growth rate in later part of this section.
However, it is also possible to explain the presence of the clear and obscure layers in
the prenatal dentine solely by the strong effect of the mothers physiological changesof the short and long cycles, because the layers in the prenatal dentine formed in
the season when the unstainable long cycle layer is deposited in the mother can be
faint. Though the conclusion on the above problem must be left for the future
study and the counting is not fully reliable at present, it will be possible to expectthat the length of the cycle of the prenatal dentinal layering is nearly same with thatof the short cycle layers in the postnatal dentine and cementum.
Omura et al. (1955) estimated the body length of the species at birth 15 feet (4.6m) and the mean body length at the attainment of sexual maturity between 32 and 33
feet (7.8 and 10.1 m) for males and between 33 and 34 feet (10.1 and 10.4 m) for
females. The length at the attainment of physical maturity was not estimated bythem. However, there are, in the odontoceti, usually observed the coincidence ofthe body length and one of the modal length-if there are multiple modes that of thelargest body length (for the bottlenose whale see Christensen 1973 and 1975, for the
sperm whales see Clarke 1956 and Gambell 1972, and for the sppotted and striped
dolphins see Kasuya 1972 and 1976 and Kasuya et al. 1974), and this is expectedalso for B. bairdii. The length frequencies of B. bairdii shown in Fig. 3 of Omura
et al. (1955) indicates the mean length of the females at the attainment of physicalmaturity about 36 feet (11.0 m), and that of the males 35 feet (10.7 m). These
values fit well to the age-length data in Fig. 8, and physical maturity of the species
seems to be attained at an age over 20 years.
The growth curves in Fig. 8 are the von Bertalanffy growth equations calculated from the length at birth 4.6 m, asymptotic length 11.0 m (females) and 10. 7 m(males), and 7.1 m the mean length of the two juvenile whales nos. 53 and 55 at
the mean age of 2.1 years. The equations are shown by the following formulae
male: y = 10.7 (1-e-0.5620-o.2s11x)
female: y = 11.0 (l-e-0,5416-o.2sssx)
where y indicates the body length in m, and x the age in years. There is, at present,
no reason to believe that the mean growth of B. bairdii can be exactly expressed by
the von Bertallanffy equation and most of the known examples are opposite cases
Sci. Rep. Whales Res. Inst.,

No. 29, 1977.

AGE DETERMINATION OF BERARDIUS

150f<?m<lle
Male

11
PMO

PI

0

10

E 9
.£
..c

&

~ 8
>-

'O
0

IXl

7

6

5

0

10

20

30

40

50

60

70

Age in years
Fig. 8. Relationship between body length and the age of B. bairdii. Closed circle
indicates male, open circle female, PM a physically mature female, and PI physically immature male. The ranges of the mean body length at the attainment ofsexual maturity are cited from Omura et al. (1955). For the growth curves see text.

as seen in both sexes of the sperm whale (Nishiwaki et al. 1958), of the bottlenose
whale (Christensen 1973), of the pilot whale (Sergeant 1962), of the white whale(Sergeant 1973), and of the striped and spotted dolphins (Kasuya 1976). One ofthe peculiar features of the growth curves of these species is the presence of a long
prepubertal period when the growth is rather linear. Accordingly, if the above
three points are given correctly, the von Bertalanffy growth equation gives slightly
higher body length at pubertal stage. However, B. bairdii does not seem to have apost-pubertal growth spurt of the male often observed in polygynous marine mammals (Bryden 1972) because the asymptotic length of the male is smaller than thatof the female and possible difference of social behavior is expected (Omura et al.
1955 ). Accordingly it is considered, at the present status of knowledge on thisspecies, that the above growth equation will roughly indicate the mean growth of
the species. These growth curves and the mean body length at sexual maturity
presented by Omura et al. (1955) suggest that the species attains the sexual maturity
at about 8 to 10 years of age (Fig. 8), which is close to that of the female bottlenose
whale (Christensen 1973).
Omura et al. (1955) estimated 10 months for the length of gestation of B. bairdii
based on the seasonal change of the fetal length. However, if the accumulation
cycle of 29.4 days is assumed for the fine layers in the prenatal dentine as in the caseof short cycles in postnatal dentine and cementum, the fetal period of the species
Sci. Rep., Whales Res. Inst.,
No. 29, 1977.

16

KASUYAafter the start of deposition offetal dentine is 29.4xl4=412 days or 13.5 months.
Laws (1959) indicated that the fetal growth of odontoceti in body length isexpressed by a earlier curvilinear growth and later linear growth, and that the period from the start of gestation to the x-intercept of the extended growth curve of thelatter, to, varies between 7 % and 15 % of the total longth of gestation (tg) in accordance with the length of tg. There are indicated large between species variation of
the length of gestation and the fetal growth rate at the period of the linear growth(Laws 1959, Frazer and Huggett 1973), and there is observed a general tendency
that the odontoceti species with large neonatal length has longer gestation period
and faster fetal growth rate. In Fig. 9 the daily increment of the body length at

E

u

.~

.i

.5

•

>.

5

·a

0

100

200
N~natal

300

400

500

length in cm

Fig. 9. Relationship between the neonatal length and the feta! growth rate inodontoceti. 1 : Phocoena phocoena, Laws 1959. 2: Tursiops truncatus, Tabolga andEss:ipian 1957. 3: Stenella attenuata, Kasuya et al. 1974. 4: S. coeruleoalba, Kasuya et al. 1974. 5: Delphinapterus leucas, Hudson Bay, Sergeant 1973. 6: D. leucas,
Kara and Barents Sea, Sergeant 1973. 7: Globicephala melaena, Sergeant 1962.
8: Physeter catodon, Ohsumi 1965. Arrow: neonatal length of B. bairdii, Omura
et al. 1955. For further explanations see text.

the linear stage of the fetal growth is plotted against the mean length at birth citedfrom various authors. For Tursiops truncatus the neonatal length 90 cm and gestation length 12 months are cited from Tavolga and Essapian (1957), and to wasestimated as 0.135 X (gestation time)= 49 days. This indicates the daily increment90/(365-49)=0.285 cm/day. There is observed a linear relationship between
the two parameters of the delphinoidea as shown below (thin solid line in Fig. 9).
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

AGE DETERMINATION OF BERARD/US

17

y = 0.001462x+0.1622
Where y indicates the daily increment in body length (cm) and x the mean neonatal
length (cm). A set of parameters for the sperm whale seems to be slightly above
the regression. If all the 8 data are dealt together, the least square regression isexpressed by the following equation (thick solid line in Fig. 9).
y = 0.001802x+0.1234
Though the former may fit better for smaller odontoceti, the latter seems to be suitable for the relationship in the general odontoceti. Using the latter equation, thelength of the linear growth period, tg- t 0 , is expressed as follows, when x indicatesthe mean neonatal length in cm.
tg-to = x / co.001802x+o.1234)
As the neonatal length of B. bairdii is 15 feet or 458 cm (Omura et al. 1955), (tg-to)
and the growth rate of the period for the species is estimated from the above equations to be 483 days and 0.949 cm/day respectively. Accordingly, the days fromthe start of gestation to the x-intercept of the linear growth curve, t 0 , is (0.07 X 483)
/ 0.93=36 days, and the total gestation time is 36+483=519 days or 17.0 months
for B. bairdii.
The approximate age of the fetus of B. bairdii at the start of the deposition of
the first dentinal layer is 519-412= 107 days of gestation. The body length at thetime is (483-412)X0.949=67 cm. In case of Globicephala macrorhynchus, the fetal
dentine starts to be laid down at about 40 cm in body length (Kasuya unpublished),
the above figure is reasonable and the correctness of the estimation of the gestation length of B. bairdii is suggested. This fetal growth curve and the fetal length
frequency reported by Omura et al. (1955) and Omura (1958) indicate that themating peak of this species exists in October and November and the birth occurs
from November to July with a peak in March and April. This feature is the reverse of that of the northern sperm whale (Ohsumi 1965).
The above equation indicates that the (tg-to) of odontoceti has an asymptote
of 1 / 0.001802=555 days or 18.2 months. For the total asymptotic gestation time,
t 0 or about 1 month shall be added to this value. Then it is considered that thegestation period of any recent odontoceti will not exceed 19 months, and that the
fetal growth of the sperm whale or of the Baird's beaked whale is one of the most
specialized. This specialization seems to have started from the fetal growth patternof the small delphinids, which are less migratory staying usually in one water massand have the mating and parturition in a same season in connection with the gestation of about one year, and attained the modification to have the mating and parturition in the opposite season of a year. This may have a relationship with theattainment of the augmentation of the body and that of the m:igration habit oflonger
distance, both of which are observed in the sperm whale and the Baird's beaked
whale.
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

18

KASUYAACKNOWLEDGMENTS

The greatest thanks are due to Dr. H. Omura, director of the Whales ResearchInstitute, and Dr. Y. Naito of the Tokyo University of Fisheries for providing thetooth samples for the present study. The Tokai Gyogyo Co., Ltd. is also acknowledged for the cooperation in collecting the data and samples. Sincere thanks are
due to Mr. A. C. Myrick of the University of California, who critically read themanuscript and gave invaluable suggestions. The influence of lunar cycle ron thedeposition of the tooth layers of odontoceti was first suggested by him in the discussion with Kasuya, and this suggestion was very helpful in analysing the growthlayers of the present species.
REFERENCES
BRYDEN, M. M., 1972. Growth and development of marine mammals. in: Functional anatomy of marine mammals (ed. R.J. Harrison), 1: 1-79. Academic Press, London and New York.
CHRISTENSEN, I., 1973. Age determination, age distribution and growth of bottlenose whales, Hyperoodon
ampullatus (Forster), in the Labrador Sea. Norwegian J. ,Z,ool., 21 (4): 331-340.
CHRISTENSEN, I., 1975. Preliminary report on the Norwegian fishery for small wha!Ps: expansion of Norwegian whaling to Arctic Northwest Atlantic waters, and Norwegian investigations of the biology ofsmall whales., J. Fish. Res. Bd. Canada, 32 (7) : 1083-1094.
CLARKE, R., 1956. Sperm whales of the Azores. Discovery Rep., 28: 237-298.
FRAZER, J.F.D. and A. ST G. HUGGETT, 1973. Specific foetal growth rates of cetaceans. J. ,Z,ool., Land.,

169: 111-126.
GAMBELL, R., 1972. Sperm whales off Durban. Discovery Rep., 35: 199-358.
KASUYA, T., 1972. Growth and reproduction of Stene/la coeruleoalba based on the age determination bymeans of dentinal growth layers. Sci. Rep. Whales Res. Inst., 24: 57-79.
KASUYA, T., 1976. Reconsideration of life history parameters of the spotted and striped dolphins basedon cemental layers. Sci. Rep. Whales Res. Inst., 28: 73-106.
KAsUYA, T., N. MIYAZAKI, and W. H. DAWBIN, 1974. Growth and reproduction of Stenella attenuata in the
Pacific coast of Japan. Sci. Rep. Whales Res. Inst., 26: 157-226.
KIRINO, T., 1956. On the number of tooth and its variability in Berardius bairdi, a genus of the beacked
whale. Okojimas Folia Anat. Jap. (Tokyo), 28: 429-434.
LAws, R. M., 1959. The foetal growth rate of whales with special reference to the fin whales, Balaenoptera physalus Linn. Discovery Rep., 29: 281-308.
MATSUURA, Y., 1942. On the northern porpoise whale, Berardius bairdi Stejneger, in the adjacent watersof" Bosyu ". Dobutsugaku ,Z,assi, 54 (12): 466-473. (In Japanese with English summary).
NISHIMURA, S., 1970. Recent record of baird's beaked whale in the Japan Sea. Puhl. Seto Mar. Biol. Lab.,18 (1): 61-68.
NISHIWAKI, M., T. HrnIYA, and S. 0HSUMI (KIMURA), 1958. Age study of sperm whale based on reading of
tooth laminations. Sci. Rep. Whales Res. Inst., 13: 135-153.
NrsmWAKI, M. and N. 0GURO, 1971. Barid's beaked whales caught on the coast of Japan in recent 10
years. Sci. Rep. Whales Res. Inst., 23: 111-122.
0HSUMI, S., 1965. Reproduction of the sperm whale in the northwest Pacific. Sci. Rep. Whales Res. Inst.,

19: 1-35.
OHSuMI, S., T. KASUYA and M. NrSHIWAKI, 1963. The accumulation rate of dentinal growth layers in the
maxillary tooth of the sperm whale. Sci. Rep. Whales Res. Inst., 17 : 15-35.
0MuRA, H., K. FUJINO, and S. KIMURA, 1955. Beaked whale Berardius bairdi of Japan, with notes on ,Z,iphiuscavirostris. Sci. Rep. Whales Res. Inst., 10: 89-132.
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

AGE DETERMINATION OF BERARD/US

19

1958. Note on embryo of Baird's beaked whale. Sci. Rep. Whales Res. Inst., 13: 213-214.
SERGEANT, D. E., 1962. The biology of the pilot or pothead whale Globicephala melaena (Traill) in Newfoundland waters. Bull. Fish. Res. Bd. Canada, 132 : 1-84.
SERGEANT, D. E., 1973. Biology of white whale (Delphinapterus leucas) in western Hudson Bay. J. Fish.
Res. Bd. Canada, 30: 1065-1090.
TABOLGA, M. C. and F. S. EssAPIAN, 1957. The behavior of the bottlenosed dolphin (Tursiops truncatus):
mating, pregnancy, parturition, and mother-infant behavior. Z,oologica, 42 (1): 11-31.
OMURA, H.,

Sci. Rep. Whales Res. Inst.,

No. 29, 1977.

20

KASUYA

EXPLANATION OF PLATESPLATE I
Lingua-buccal medial ground sections of the teeth of B. bairdii. Photographed undertransmitted light and the contrast is reversed. The outermost structure is the artefact of the resin, actual size. 1 : Feta! dentine, 2 : Postnatal dentine, 3 : Osteodentine, 4 : Cementum, 5 : Resin.
Fig. I. Anterior tooth of the whale no. 55, 6.4 m, female, about 1.8 years old.
Fig. 2. Anterior tooth of the whale no. 53, 7.8 m, male about 2.4 years old.
Fig. 3. Anterior tooth of the whale no. 41, 10.9 m, male, 47 years old.
Fig. 4. Posterior tooth of the whale no. 53. For the explanations see Fig. 2.
PLATE II
Decalcified and stained sections of the teeth of B. bairdii. Scale indicates 0.1 mm.
Fig. I. I : Cementum, 2 : Feta! dentine, 3 : Postnatal dentine. Bar indicates thelong cycle stainable layer, and circle the short cycle stainable layer. Anterior
tooth of the whale no. 55, 1.8 years old.
Fig. 2. Cementum of the same tooth. Circle indicates the short cycle stainable
layer.
Fig. 3. Feta! dentine of the anterior tooth of the whale no. 53. Circle indicates
short cycle stainable layer.
Fig. 4. Cementa! layers of the whale no. 37, anterior tooth. Pulp side at the top.
For the marks see Fig. I.
Fig. 5. Cementa! layers of the whale no. 51, anterior tooth. Pulp side at the top.
For the marks see Fig. I.
PLATE III
Decalcified and stained section of the anterior tooth of B. bairdii, whale no. 49. Scaleindicates 0.1 mm.
Fig. I. Lower magnification, pulp side at the bottom, dentine is lost. Closed
circle indicates the stainable layer of the long cycle.
Fig. 2. Higher magnification of the upper left part of Fig. I.

Sci. Rep. Whales Res. Int.,
No. 29, 1977.

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GROWTH AND REPRODUCTION OF STENELLA
COERULEOALBA OFF THE PACIFIC COAST
OF JAPANNOBUYUKI MIYAZAKI
Department of Marine Sciences, University of the Ryukyus, Okinawa

ABSTRACTThis study is based on data from about five thousand specimens of S.
coeruleoalba. Mean length at birth is 100 cm. Mean lengths at the age of 1
year and 2 years are 166 cm and 180 cm, respectively. The species starts feeding on solid food at the age of 0.25 year (or 135 cm). Mean weaning age isabout 1.5 years (or 174 cm). Mean testis weights at the attainment of puberty
and sexual maturity of males are 6.8 g and 15.5 g, respectively. Mean ages at
the attainment of puberty and sexual maturity of males are 6. 7 years (or 210cm) and 8.7 years (or 219 cm), respectively. Females attain puberty andsexual maturity on the average at 7.1 years (or 209 cm) and 8.8 years (or216 cm), respectively. There are three mating seasons in a year, from February to May, from July to September, and in December. Mating season may
occur at an interval from 4 to 5 months. The overall sex ratio (male/female)is 1.14. Sex ratio changes with age, from near parity at birth, indicating
higher mortality rates for males.

INTRODUCTION

The striped dolphin, Stenella coeruleoalba are caught annually by the driving fisheryor hand harpoons in the Pacific coast ofJapan (Ohsumi 1972, Miyazaki et al. 1974).
According to Ohsumi (1972), Miyazaki et al. (1974), and Nishiwaki (1975), thestriped dolphins caught in the Pacific coast of Japan are suggested to belong to
one population.
The growth and reproduction of the species have been studied by some Japanesescientists (Nishiwaki and Yagi 1953, Hirose et al. 1970, Hirose and Nishiwaki 1971,
Kasuya 1972, Kasuya and Miyazaki 1976, and Kasuya 1976). Hirose et al. (1970),
and Hirose and Nishiwaki (1971) made histological examinations of the gonads,
but they did not make the age determination. Kasuya (1972) studied growth
and reproduction by the age determination by means of dentinal growth layers,and estimated that there are two mating seasons in a year. Kasuya and Miyazaki(1976) reported that the mean calving interval in the population in the coast ofJapan is decreasing in accord with a decrease in population level. Recently Kasuya(1976) reconsidered the life history parameter, based on cementa! layers, and indicated that the analysis of the life history by means of dentinal layers can not be
available in the older animals. However, Kasuya (1976) did not analize growth
Sci. Rep. Whales Res. Inst.,
No. 29 .1977, 21-48

MIYAZAKI

22

and reproduction by detailed examinations of the gonads.
The present study was undertaken to make histological examinations of thetestes and detailed observations of the ovaries, in order to reconsider the life history
up to the age of 13.5 years based on dentinal layers with abundant specimens, andto estimate the mating season of the species.
TABLE 1.

LIST OF MATERIALS USED IN THIS STUDY
Number of dolphins

Schoolno.

Date of kill

5
6
8
9
10
11
12
13
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
42
43
44

16, 18, 22, Nov. '68
17, Nov. '68
12, Oct. '70
13, Oct. '70
21, Oct. '70
24, Oct. '70
29, Oct. '70
22, Nov. '70
2, Dec. '70
10, Dec. '70
2, Oct. '71
4, Oct. '71
5, Nov. '71
17, 18, Nov. '71
20, Nov. '71
15, Dec. '71
3, Oct. '72
4, Oct. '72
7, Oct. '72
8, Oct. '72
13, 15, 16, Oct. '72
14, 18, 19, Oct. '72
17, 19, 20, Oct. '72
23, Oct. '72
26, Oct. '72
1, Nov. '72
5, Nov. '72
9, Nov. '72
10, Nov. '72
15, Nov. '72
16, Nov. '72
17, 20, Nov. '72
21, Nov. '72
23, 26, Nov. '72
7, 9, Dec. '72
19, Nov. '73
20, 22, Nov. '73
20 Jan. '73 - 15, Feb. '73

Total**

CaughtExamined

1,700
344
265
293
324
49
48
1,832
259
84
393
101
25
636
140
903
31
225
120
94
574
305
238
48
54
63
284
239
45
243
200
372
293
535
912
414
l, 724271 *
14,409

406
318
89
64
68
33
34
125
256
84
176
58
25
361
100
300
29
96
31
41
211
124
108
29
40
63
120
104
27
112
71
212
130
137
168
251
470
271*
5,071

Percentage
ofexamination
23.9
99.7
33.6
21.8
21.0
67 .4
70.8
6.8
98.8
100
44.8
57.4
100
56.8
71.4
33.2
93.5
42.7
25.8
43.6
36.8
40.7
45.4
60.4
74. l
1-00
42.3
43.5
60.0
46.l
35.5
57.0
44.4
25.6
18.4
60.6
27.3
100

Researcher
KasuyaKasuyaMiyazaki and Kasuya
MiyazakiMiyazakiMiyazakiMiyazaki
HiroseMiyazakiMiyazakiMiyazakiMiyazakiMiyazakiMiyazakiMiyazakiMiyazaki and Kasuya
MiyazakiMiyazakiMiyazakiMiyazakiMiyazakiMiyazakiMiyazakiMiyazakiMiyazakiMiyazakiMiyazakiMiyazakiMiyazakiMiyazakiMiyazakiMiyazakiMiyazakiMiyazakiMiyazakiMiyazaki and Kasuya
Miyazaki and Kasuya
Miyazaki* animals caught by hand harpoon at Taiji.
* * exclude the animals caught at Taiji.

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

GROWTH AND REPRODUCTION OF STRIPED DOLPHIN

23

MATERIALS AND METHODS

Biological informations were obtained from 5,071 striped dolphins from 37 schools
caught by the driving fisheries at Kawana and Futo on the east coast of Izu Peninsula
during the five years from 1968 to 1973, and from 271 dolphins caught by hand
harpoon at Taiji on the coast of Kii Peninsula in 1973 (Table 1). Of these specimens the data of the school nos. 5 and 6 were provided by Dr. T. Kasuya, and of theschool no. 13 by Dr. K. Hirose.
Body length was measured in I cm interval in a straight line from the tip of theupper jaw to the notch of the tail flukes.
Mammary gland was observed in the field and classified into lactating andnonlactating.
The ovaries were collected from most of females and fixed in 10% formalinsolution. In the laboratory the ovaries were weighed, the number of corpora albicantia and lutea was counted, and the three diameters of corpora were measured.
The mean diameter of the corpora was obtained as the cube root of the value multiplied their diameters.
Usually the testes were collected from most of males, fixed in 10% formalinsolution, and then transported to laboratory. Histological samples were takenfrom the center of cross section at the midlength of the testis, processed into microscopic slide, and stained with haematoxylin and eosin.
Several teeth were collected from the center of tooth row of each dolphin witha pair of gardening scissors and fixed in 10% formalin solution. The teeth wereprepared by the method of Kasuya et al. (1974). The opaque layers were counted
under a binocular microscope ( X 20- X 50) with transmitted light.
The ages of930 dolphins of the school nos. 5, 6, 22, 28, 43, and 44 were determined by Dr. T. Kasuya. As his age determination of the animals between theage of 1 and 12 years was biased by 0.27 year to the lower side ofMiyazaki's reading(Kasuya and Miyazaki 1976), there is no significant difference between their age
determinations. Therefore, in this study the age data determined by Dr. T. Kasuya
were used together with the same data prepared by Miyazaki.
AGE DETERMINATION

Growth layers in the dentine have been used for age determination of the animals
by various authors, for example in Tursiops truncatus (Sergeant 1959), Globicephalamelaena (Sergeant 1962), Physeter catodon (Ohsumi et al. 1963), Stenella coeruleoalba(Kasuya 1972), Stenella attenuata (Kasuya et al. 1974). Recently cementa! layers
were employed in the age determination of the animals in S. coeruleoalba and S. attenuata (Kasuya 1976).
Since the teeth on the anterior parts of the jaws are too small and those on theposterior are too strongly twisted, they were not used for the age determination.
The readability of the growth layers in teeth from different positions of the same
animal was checked on one individual (Table 2). The number of layers in theseSci. Rep. Whales Res. Inst.,
No. 29, 1977.

MIYAZAKI24

TABLE 2. AGE DETERMINATION BY TEETH COLLECTED FROMVARIOUS POSITIONS OF JAWS IN ONE DOLPHIN
Tooth No. from tip of jaw
Jaw
Left upper jaw
Left lower jaw
Right upper jaw
1 6 91

10

20

30

40

10.5
12.5
10.5

12.5
12.5
11.5

11.5
12.5
13.5

12.5
12.5
11.5

22 4 8 36 8 2

1330 1 9 1 0

10 0

i!

80

>u

c

60

Cl>
:J

.,er 40
u..
20
0
Oct.

Nov.

Dec.

Jan.

Feb.

s e a so n
Fig. 1. Seasonal change of the formation of opaque and translucent dentinal layers.
The marks indicate thin opaque layer, thick opaque layer, thin translucent layer,
and thick translucent layer (from top to bottom). The numbers at the top indicate the sample size. The dates of the kill are grouped into the lst, 2nd, and3rd decade of month.

teeth ranges from 10. 5 to 13. 5 years (average : 12. 0 years) indicating no significant
variations.
In order to find out the annual accumulation rate of dentinal growth layer,
the kind of the last layer and its thickness were examined on the teeth with threeor less opaque bands. Fig. 1 shows that the alternation from opaque to translucent
layer occurs in the period of December and January. This is slightly later thanthat estimated by Kasuya (1972). In the present study it is impossible to decide
when the alternation from translucent to opaque layer occurs because of the absenceof adequate samples. However, above result coincides with that of S. attenuata(Kasuya et al. 1974) in which the alternations occur in December or January andalso in April or May, and each opaque and translucent layer represents about 6
months. Accordingly it will be correct to presume that the alternation from opaque
to translucent layer of the dentine of S. coeruleoalba may occur in winter and thealternation -from translucent to opaque layer in summer, and that each opaque andtranslucent layer represents approximately 6 months, respectively.
In the present study an approximate age was calculated by the criterion of
Kasuya et al. (1974) taking into consideration of the kind of the first and the lastSci. Rep. Whales Res. Inst.,
No. 29, 1977.

GROWTH AND REPRODUCTION OF STRIPED DOLPHIN

25

layers, and of their thickness in the dentine.
Since the dentine above 16 layers is composed of poorly calcified secondary dentine, it is impossible to read precisely the dentine with 16 layers or more. Kasuya(1976) showed that the accumulation of the dentine layers of S. coeruleoalba ceases ata large variety of age above 11 dentinal layers and that the accumulation of cemental
layers continues longer. The number of dolphins fallen in the range between x+ 1
and x-1 cemental layers was calculated at the x dentinal layer on the basis of Fig. 2of Kasuya (1976). The ratios of this number to the total at 12, 13, 14, and 15
dentinal layers were calculated at 80.9, 72.7, 54.8, and 13.8%, respectively. This
indicates that the ratio of the dolphins whose ages are underestimated becomes
gradually higher with the increase of the number of dentinal layers during 11 and 15
layers, and this ratio attains about 50% at 14 dentinal layers. Accordingly the age
determination of the animals seems to be reliable till 14 dentinal layers with precision of 50% or more. Therefore, this study intends to analize the animals at theage of 13.5 years or less. During 11 and 14 dentinal layers, however, the value ofthe mean growth curve or age-weight of testis relationship obtained in this study
appears to be higher than that expected from cemental layers by Kasuya (1976), andthe bias between two values is considered to become larger with increase of the number of dentinal layers.

GROWTH
Mean body length at birth
Since the body lengths of newborn calves do not show distinct sexual dimorphism and available data are scarce, the mean body length at birth was calculated
by combining both sexes. The body lengths were grouped at interval of 5 cm.
The largest fetus was 108 cm and the smallest calf 98 cm. Then the fetuses andcalves from 95 cm to 115 cm groups were used to calculate the mean body length
at birth (Table 3). The number of fetuses and calves was equal at 105 cm group.
However, the numbers of fetuses and calves between 95 and 115 cm groups were 68
and 20 animals, respectively, and there is a big difference between two numbers.
This seems to be caused by the loss of some newborn calves during the driving ofanimals as already suspected by Kasuya (1972). Then the frequency was corrected
to equalize the numbers offetuses and newborn calves (Table 3). The mean bodylength at birth was obtained at 100.5 cm as the body length corresponding to the
TABLE 3.

BODY LENGTH FREQUENCIES OF FETUSES AND CALVES

Length group
(cm)

Fetus
(no.)

Calf
(no.)

Fetus

Calf

(%)

(%)

Percent of calf
(corrected)

95
100
105
110
115
Total

33
30
4
1
0
68

0
8
4
5
3
20

48.53
44.12
5.88
1.47
0
100

0
40.00
20.00
25.00
15.00
100

0
45.39
77.28
94.45
100
50.00

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

MIYAZAKI

26..----

100

a

u

0

50

______

/

c:
a.

0
0

u

...

1~

a.

a.

0

90

95

100

Body
Fig. 2.

/105

lengthMean body length at birth.

frequency of 50% (Fig. 2).

110

115

in

cm

120

For explanation see text.

This result coincides with that of Kasuya (1972).

Weaning
The weaning age of the animals was estimated by the following two methods.
First method: The food remains in the first stomach of 45 young animals were
examined (Table 4 ). The smallest animal containing solid food in the stomach was
133 cm and the largest containing milk was 176 cm in body length. The youngest
animal containing the solid food in the stomach was 0.25 year old and the oldest containing milk was 1.25 years old. Accordingly it is considered that some individuals
start feeding on solid food at 133 cm or 0.25 year, and some may continue to take
both milk and solid food until 176 cm in body length or by the age of 1.25 years.
However, this age seems to be underestimated, because when an animal contains
solid food, it is not easy to detect milk mixed in solid food.
The food items found in the stomachs of these young animals were fishes, squids,
and shrimps. This suggests that when the young animals start to feed on solid food,no preference was made among fishes, squids, and shrimps.
Second method: The next method is to compare the number of the young postnatal dolphins and that of the lactating females in the school. In the first place thecalves were counted in the order of their ages from the youngest one until the number
become equal to that of lactating females. Then the weaning age was determined
to be the age of the last calf in this counting in each school. Secondly the dolphinsof this age or younger were classified as suckling calves, and the dolphins older than
this age as juvenile calves in each school. Finally the ratio of juvenile calves to thetotal calves from 17 schools was calculated at each age as shown in Fig. 3. The oldest
suckling calf was at the age of2.5 years. As the relation between this ratio and age
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

27

GROWTH AND REPRODUCTION OF STRIPED DOLPHINTABLE 4.
Date of kill
3, Dec. '72
23, Nov. '72
17, Oct. '72
20, Nov. '71
20, Nov. '72
17, Oct. '72
20, Nov. '72
3, Dec. '72
20, Nov. '73
7, Oct. '72
20, Nov. '73
20, Nov. '73
20, Nov. '73
20, Nov. '73
17, Oct. '72
20, Nov. '73
20, Nov. '73
20, Nov. '73
26, Jan. '73
3, Dec. '72
20, Nov. '73
3, Dec. '72
20, Nov. '73
20, Nov. '73
20, Nov. '73
20, Nov. '73
3, Feb. '73
17, Oct. '72
13, Oct. '72
26, Jan. '73
3, Feb. '73
1, Nov. '72
1, Nov. '72
30, Jan. '73
1, Nov. '72
31, Jan. '73
31, Jan. '73
26, Jan. '73
26, Jan. '73
31, Jan. '73
21, Jan. '73
21, Jan. '73
26, Jan. '73
3, Feb. '73
26, Jan. '73

WEANING AND TOOTH ERUPTION

Field
no.

Sex

Body
length

Age

155
2
40
41
112

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

102
103
110
112
122
130
132
132
133
135
142
145
149
149
150
151
152
153
154
154
154
157
157
158
159
163

0.25
0.25
0.25

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

163
170
172
174
176
182
184
184
184
184
184
185
185
186
187
187
188
189
196

114
133
92
7
126
182
27
28
3
12
13
11
20
144
136
143
167
214
127
49
23
4
11
30
22
2
10
9
3
30
3
7
5
3
4
5
29
4

0.25
0.25
0.25

Milk

Food

L:+Jo,R:+Jo
r

none

r

none

L : 30Jo, R: 33Jo
L: 35Jo, R: 35Jo

milk only
milk only

L: 37J28, R: 37J28
L: +Jo, R: +Jo

0.5

r
r
none
r
none
r
r
r
none
none
r

0.5

r

r
r

0.5
r
r
r

beaks of squids
fish lensmilk only
beaks of squids
milk only
beaks of squids
beaks of squids
milk only
milk only
fish lens
L: +J+, R: +J+
beaks of squids
L: +J+, R: +J+

0.5
0.5
1.25

1.25
2.50
2.25
0. 75
1. 75
1.50
1. 75
2.50
2.75
3.00
1. 75
3.00
2.75
1. 75
I. 75
2.75
3.00
2.25

r
r

r
r
r
r
r
r
r
rr

r
r

r
r

r
rr

L, left; R, right; M, male ; F, female ; r, few; rr, abundant; +, erupted

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

Comments

L: oJo, R: oJo
L : oJo, R: oJo

r
0.25
0.5
0.25

No. of erupted
teeth

beaks of squids
beaks of squids
beaks of squids
beaks of squids
and shrimps

fish

28

MIYAZAKI

can be shown in a straight line during the ages from 0.25 to 2. 75 years, this line wascalculated by the least squares during this range (Fig. 3). The age at which theratio shows 50% is calculated to be ·1.5 years. This indicates that the mean weaning
21

48

9

26

40

43

·13

12

39

100

•

50

•

16

185

•

~Y=46.7164X-----------•

2• • • •

100•

520.8200( r= 0.9747)

.,,1
·I
~,

0 ._......

~____..__,__.___,~~~~~~~~~~-'-~

0.5

0

1 .5

1.0

Age

3.0

2.5

2.0
in

3.5

years

Fig. 3. Age of the weaning in S. coeruleoalba. Closed circles indicate the frequencyof the juvenile calves. The numbers at the top show the sample size. For explanation see text.

!!Eu85 106

99

82

64

53

74 72

69

96 106

13

10

14

B

6

3

4

1

6 71 60 93 122 135 139 114 139 133 105 98 59 86 71 72 42 41 48 39· 30 9

17

9

10

5

1

1

1

54

66

85

81

78

69

57

40

40

1

1

250

c

.r:.

200

Cl

c
<I>

150

>·u
0

JJ'.l

1 00
10

0

A g

e

io

15

n

y

e

a

25

30

s

Fig. 4. The mean growth curves of the male and the female. Closed circles indicate the male and open circles the female. The numbers at the top indicate thesample size. For samples greater than 30, ± standard deviations indicated asvertical line. Solid line is drawn for the animals younger than 13.5 years old andthe dotted line for the animals older than 13.5 years old.

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

GROWTH AND REPRODUCTION OF STRIPED DOLPHIN

29

age is 1.5 years and the body length at this age is 174 cm as indicated by the mean
growth curve (Fig. 4). This method is not adequate to estimate the minimum
weaning age. However, it is more reliable to estimate the maximum weaning age.
Accordingly the mean weaning age is 1.5 years, and some dolphins may continue tosuck milk until they become 2 to 3 years old. However, this mean weaning age
seems to be overestimated, because the possible loss of newborn calf is expected(see page 25 ).
From these informations it is concluded that S. coeruleoalba starts feeding on
solid food at the age of about 0.25 year (or 133 cm), the mean weaning age of thespecies is approximately 1.5 years (or 174 cm), and some dolphins may continue totake milk till the age of 2 to 3 years.

Tooth eruption
At birth the teeth of young animals have not yet pierced the gums. Teeth
begin to erupt at about 110 cm and are almost erupted at approximately 130 to
150 cm in body length, as may be seen from the data shown in Table 4. The orderof tooth eruption is: first, the 10-40th tooth of the upper jaw, and then the same
numbers of the lower jaw, and finally those close to anterior and posterior ends.
The body length in which teeth of both upper and lower jaws almost erupt wellagrees with the body length of the animals which start feeding on solid food.
Postnatal growth
As the age determination of S. coeruleoalba is reliable till 14 dentinal layers (seepage 25 ), in this section the postnatal growth till 14 dentinal layers was analized
in detail with abundant data.
Based on the data of 1, 752 males and 1,535 females, the mean body length wasplotted against each dentinal layer, and the mean growth curve of S. coeruleoalba
was drawn by assuming body length at birth is 100 cm (Fig. 4). Fig. 4 shows that
S. coeruleoalba attains the body length of 166 cm and 180 cm at the age of 1 and 2
years in average, respectively. The sexual dimorphism of the body length appears
at the age of about 3 years. The mean body length of the males is larger than thatof the females at the ages from 3 to 10 years. The mean growth rate of the females
increases at the age from 7 to 8 years. However, the mean body length of the females in this period does not exceed that of the males at the same age. Afterthe age of
9 years, that is close to the mean age of attaining sexual maturity in the females, themean growth rate of the females becomes slower, and the growth in the mean bodylength stops at the age of 12 years. On the other hand, the mean growth rate of themales is almost constant during the ages from 5 to 10 years. The mean growth rateof the males increases at the age of 11 years. Then the increase of the mean bodylength stops at the age of 13 years. The mean body lengths of 284 males older than
14 years, and of 584 females older than 12 years were calculated at 238 cm and 225
cm, respectively. According to Kasuya (1976) the asymptotic ages of S. coeruleoalba
in the female and the male are 17 and 21 years, respectively. However, the mean
body length offemales older than 12 dentinal layers is close to the asymptotic length
Sci. Rep. Whales Res. Inst.,
No 29, 1977.

MIYAZAKI

30

of the female obtained by Kasuya (1976), and that of males older than 14 dentinal
layers is larger than the asymptotic length of the male obtained from Kasuya (1976).
This indicates that if more abundant data are available, the asymptotic lengths of
S. coeruleoalba in both sexes would be slightly larger than those expected by Kasuya(1976).
REPRODUCTION IN THE MALE

Testis weight and the maturity
The bilateral difference of testis weight was examined for 30 individuals. The
ratio of the heavier testis to the lighter one came between 1.00 and 1.32, and theratio less than 1.20 was observed in 93% of all the pairs. The ranges of the testis
TABLE 5.
Weight(left, g.)

T-TEST OF THE SYMMETRY OF THE TESTIS WEIGHT

Range(L. - R.)

<6.8
6.8-15.4
15.5;;;;
Total-1.2 -1.0 -1.5 -1.5 -Meandifference

SamplesizeStandard
error

Probability-0.2100-0.1700
3.29000.9700

10
10
10
30

0.14870.19322.30910.86660.80<p>0.90
0.50<p<0. 70
0.80<p<0.90
o. 70<p<0.80

0.3
0.9
22.0
22.0

500
300
OI

r:::

l'

l/)

I

:;: 100.:·. • ..
p!:
: r.
....
•.

l/)

i

GI

....... 50
~

GI
.i::.

:

30

OI

:

:

.•

:

i

I :

!. - •- . t<
:.

0

.i::.

i.: ! !
i.;:.
.. i:

11 •

~

;.

10

D

~:~

I~:.

.~

~

·~r~~ ~

GI~.
: i~;~t'~.

;;:: 5
3

.: .
0

..
i

'

5

10

15

20

25

30

Age in years

Fig. 5. Relation between age and the weight of the left testis. The weight of theleft testis is plotted on logarithmic scale. Closed circles indicate the mature animals, open circles the immature, and open circles with rod the pubertal.
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

31

GROWTH AND REPRODUCTION OF STRIPED DOLPHIN

weight of immature, pubertal, and mature males on the average were obtained atless than 6.8 g, from 6.8 to 15.4 g, and at 15.5 g or more, respectively, as indicatedin the latter sections of this study. The mean differences of the testis weights inthese ranges are small enough to consider that there is no significant asymmetryof the testis weight (Table 5 ). Therefore, the weight of the left testis was used in
the present study.
In order to check the maturity tissues were taken from the center of the crosssection at the midlength of the testis and the tissues collected from testes of 350
males were histologically examined. Immature, pubertal, and mature males were
defined as the animals having testes containing only spermatogonia, both spermatogonia and spermatocyte, and spermatozoa, respectively.
Fig. 5 shows the relation between age and testis weight. The testis weightrapidly increases at the ages of 2.5 years when pubertal male first appears and of9years which is about the mean age attaining sexual maturity. The increase of
testis weight stops at about the age of 13.5 years. However, Kasuya (1976) reported that there was no increase related with the age of the animal after 15 years
TABLE 6.
Testisweight(g)

MATURITY OF THE MALE AND ACTIVITY OF THE MATURE
MALE BY GROUP OF THE LEFT TESTIS WEIGHT
MatureImmature

12345678910152025303540455060708090100150200Total

Total

PubertyMI3(100)
12 (100)
13 (100)
13(65.0)14(73. 7)
3 (20.0)5(35. 7)4(57.1)I (20.0)

7 (35.0)5(26.3)12 (80. 0)8(57.1)3(42.9)4(80.0)8(61.5)7 (43.8)
1 ( 8.3)
1 ( 5.3)
1(10.0)1 ( 6. 7)5(38.5)7 (43.8)
7(58.3)15(78.9)4(40.0)6(40.0)5(38.5)3(27 .3)
5(31.3)2 (22.2)
1(10.0)2(12.5)4 (33. 3)
3(15.8)5(50.0)8(53 .3)
6(46.2)6(54.5)8(66. 7)
6(37 .5)
3 (33 .3)
I (10.0)5( 9.1)2(13.3)

68

58

Sci. Rep. Whales Res. Inst.,

Miil

Total

I ( 7. 1)

61

Figures in parentheses indicate percentage.

No. 29, 1977.

MII

59

2(15.4)2(18.2)4(33.3)5(31.3)4(44.4)8(80.0)17 (100)
50(90. 9)13(86. 7)3(100)
108

5
9
11
18
9
14
13
11
12
16
9
10
17
55
15
3
228

3
12
13
20
19
15
14
7
5
13
16
12
19
10
15
13
11
12
16
9
10
17
55
15
3
354

Maturity
(%)
0
0
0
0
0
0
7.1
0
0
38.5
56.3
91. 7
94.7
90.0
93.3
100
100
100
100
100
100
100
100
100
100

32

MIYAZAKI

old. This age difference appears to be related with differences in the methods ofage determination.
Table 6 shows the ratio of immature males to the total males for each testis
weight. The testis weight of the pubertal males ranges from 4.0 to 37.0 g. The
relation between this ratio and testis weight in the range from 3.5 to 10.5 g can beshown by a straight line. The following formula was obtained by the least squares
method, y= l l.332lx-26.6626 r=0.8407; x: testis weighting, y: the ratio, r:
correlation coefficient. The testis weight that 50% of the animals attain the
puberty is 6.8 g.
Table 7 shows the ratio of immature males to the total males at each age. The
youngest pubertal male was 2.5 years and the oldest immature was 11.5 years. The
relation between this ratio and age in the range from 3.5 to 10.5 years can be shownby a straight line. Calculation by the least squares method gives the formula,y=l5.2060x-51.5292 r=0.9652; x: age in year, y: the ratio, r: correlation
coefficient. The age when 50% of the animals attain puberty is 6. 7 years
and the body length at this age is 210 cm as indicated by the mean growth curve(Fig. 4).
The ratio of mature males to the total males for each testis weight is shown in
TABLE 7.

MATURITY OF S. COERULEOALBA BY AGE GROUPS
Male*

Female**Age
immat.
0.5
1. 5
2.5
3.5
4.5
5.5
6.5
7.5
8.5
9.5
10.5
11.5
12.5
13.5
14.5
15.5
16.5
17.5
18.5
19.5
20.5~

Total

pub.

mat.

total

1(100)
4(80.0)11 (100)
17 (85.0)
15(78.9)9 (50. 0)5(17.9)3 (14.3)
4 (14. 8)
0 (0)I ( 4. 8)
0(0)
0(0)
0(0)

0(0)
1 (20.0)0(0)3(15.0)4(21.1)7 (38. 9)15(53.6)9(42.9)6(22.2)2(10.0)0(0)5 (15. 6)
3 ( 9. 4)
I ( 4.2)

0(0)
0(0)
0(0)
0(0)
0(0)
2(11.1)8(28.6)9(42.9)17 (63.0)
18 (90. 0)20(95.2)
27(84.4)29(90.6)23(95.8)

5
11
20
19
18
28
21
27
20
21
32
32
24

0(0)
0(0)
0(0)
0(0)
0(0)
70

0(0)
0(0)
0(0)
0(0)
0(0)
56

21 (100)
11 (100)
12(100)10(100)15(100)
222

21
11
12
10
15
348

immat.

pub.

mat.

total

4(100)
5 (100)22 (95. 7)
42 (97. 7)32(86.5)
20 (74.1)
17(63.0)9(36.0)6(16.7)6(14.3)3 (8.3)0(0)I (1. 3)
0(0)
0(0)
0(0)
0(0)
0(0)
0 (0)
0(0)
0(0)
167

0(0)
0(0)
1(4.3)
I (2.3)3 (8. I)
6 (22 .2)
8 (29. 6)
8 (32.0)16(44.4)
7(16.7)5(13.9)2 (3.4)1(1.3)
0(0)
0(0)
0(0)
0(0)
0 (0)
0(0)
0(0)
0(0)
58

0(0)
0(0)
0(0)
. 0(0)
2(5.4)
I (3. 7)2 (7. 4)8(32.0)14(38.9)29(69.0)28(77 .8)
56(96.6)
73 (97 .3)
54(100)57 (100)
46(100)44 (100)
40(100)27 (100)
21 (100)
42 (100)
544

4
5
23
43
37
27
27
25
36
42
36
58
75
54
57
46
44
40
27
21
42
769

* The testis was histologically examined.
* * The ovaries were weighed and the number of corpora albicantia and Iutea was counted.
in parentheses indicate percentage.

FiguresSci. Rep. Whales Res. Inst.,
No. 29, 1977.

GROWTH AND REPRODUCTION OF STRIPED DOLPHIN

33

Table 6. The testis weight of the mature males varied from 7.7 to 225.2 g. The
relation between this ratio and testis weight can be shown by a straight line in therange from 2.5 to 27.5 g. The following formula was obtained by the least squares
method, y=4.2577x-15.8157 r=0.9819; x: testis weight in g, y: the ratio, r:
correlation coefficient. The testis weight that 50% of the animals attain sexual
maturity is 15.5 g.
Table 7 shows the ratio of mature males to the total males at each age. The
youngest mature male was 6.5 years and the oldest pubertal was 14.5 years. The
relation between this ratio and age can be shown by a straight line in the range from
5.5 to 11.5 years. Calculation by the least squares method gives the formula, y=
17.0643x-97.7893 r=0.9923; x: age in year, y: the ratio, r: correlation coefficient. The age when 50% of the animals attain the sexual maturity is 8. 7 years
and the body length at this age is 219 cm as indicated by the mean growth curve(Fig. 4).
Fig. 6 shows the length frequencies of mature animals and pubertal or immatureones at each age from 6.5 to 10.5 years. This figure clearly shows that the body
Female

60
40

Male

6.5

years

7.5

years

20

"'c:

0

.s:

40

CL

-

20

..,

0
40

0

20

.

0

.0

E
20

z
0

'"''~

20

180
B

o

200

220

y

I

d

240

260

180

200

e

g

h

i

n

t

n

· 2W
c

240

260

m

Fig. 6. The body length frequencies of both sexes in each age. White squares indicate immature or pubertal animals, and black mature animals.

Sci. Rep. Whales Res. Inst.,.No. 29, 1977.

MIYAZAKI

34

length of the mature animals is larger than that of the pubertal or immature onesat the same age, and maturity rate of the older animals is higher than the younger
ones at the same body length group. These suggest that the larger animals attainsexual maturity earlier than the smaller in the same age, and the sexual maturity
rate of the animals increases with the age in the same body length.
In order to estimate the spermatogenic activity of the testis, 20 seminiferoust<iro1415141s 25 24 13 1s

s

1

16

s

16

s

1

3

3

a

2

1

I

200

c
·- 150

I

"'N
"iii
~100

"
"

.0

I-

0

150

100

50

0

Weightof left

I est is200
in g

Fig. 7. Relation between the weight of the left testis and the diameter of seminiferous tubules. Closed circles indicate mean and vertical lines range. Solid line
is drawn by eyes. The numbers at the top indicate the sample size.
TABLE 8.

SEASONAL VARIATIONS OF TESTIS WEIGHT AND SEMINIFEROUS TUBULE

SeasonOct.

Immature

Pubertal

No.

T.W.

S.T.

No.

T.W.

S.T.

No.

T.W.

S.T.

E.

6

4.4

40

14

7.5

48

66

127

M.

9

5.1

40

4

15

59

2
(6.3)
4
(8.0)

50

94

4

8.5

61

I

35

121

47

109

29

110

29

84

II

59

33

98

L.

Nov.

Dec.

MI

E.

2

4.4

46

5

13

63

M.

5

6.9

48

5

9.5

57

L.

6

9.6

50

II

15

63

E.
M.

42

3.9

43

15

7.0

47

(25. 0)8(15.4)
22(56.4)
20(55 .6)3(42.9)

L.

Total
Mean

70

58
4.8

44

60
(27. 3)
10

55

T.W. and S.T. indicate mean left testis weight (g) and mean seminiferous tubule size (µ),respectively.
Sci. Rep. Whales Res. Inst.,

No. 29, 1977.

GROWTH AND REPRODUCTION OF STRIPED DOLPHIN

35

tubules selected at random from each testis of the sexually mature males were histologically examined. The mature males of type MI and type Miii were definedas the animals having testes containing spermatozoa in only one tubule and in all
20 tubules, respectively. The mature males of type MII was defined as the animals at the intermediate stage of type MI and type Miii. The testis weights of themature males in type MI, MII, and Miii range from 7.7 to 80.0 g, from 17.2 to
159.7 g, and from 42.2 to 225.2 g, respectively. The ratios of the mature males
in type MI, MII, and Miii to the total mature males for each testis weight are
shown in Table 6. The relation between the ratio of type Miii and testis weight
can be shown by a straight line in the range from 40 to 100 g. Calculation by theleast squares method gives the formula, y=l.5680x-58.1632 r=0.9639; x:
testis weight in g, y: the ratio, r: correlation coefficient. The testis weight thatthe ratio of type Miii shows 50% is 68.9 g. This indicates that the mean testis
weight at the attainment of the full sexual maturity is considered to be approximately 70 g. This value well coincides with the weight at the age of 13.5 years(Fig. 5).

Relation between the testis weight and the diameter ef seminiferous tubule
The testes of 348 males were histologically examined. The mean of the measurements of 20 seminiferous tubules selected randomly from a testis was used as thediameter of the tubules of the specimen. The diameters of the tubules in 70 immature, 58 pubertal, and 220 mature males range from 33.0 to 65.0 µ (mean: 43.5 µ),from 34.0 to 104.0 µ (mean: 54.6 µ), and from 45.0 to 214.0 µ (mean: 130.8 µ),
IN THE IMMATURE, THE PUBERTAL, AND THREE TYPES OF THE MATURE MALES
Mature
MIII

MII

Total

No.

T.W.

S.T.

No.

T.W.

S.T.

No.

7
(21. 9)7(14.0)
3(75. 0)16(30.8)
16(41. 0)12(33. 3)

97

170

119

168

121

158

23
(71. 9)39(78. 0)

119

155

47

156

49

122

45

119

35

112

32
(100)
50
(100)
4
(100)
52
(100)
39
(100)
36
(100)

17

73

1
(14. 3)62(28.2)

28(53.8)
1(2.6)
4(12 .1)3(42.9)

98

72

152
169

49

103

55

92

130

108

Figures in parentheses indicate parcentage in the mature.
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

S.T.

111

166

113

150

44

148

78

136

37

115

33

95

31

75

73

131

220
(100)

98
(44.5)
55

7
(100)

T.W.

153

MIYAZAKI

36

respectively.
Fig. 7 shows the relation between the seminiferous tubule size and testis weight.
The increase of the diameter of the tubule is rapid when the testis weight becomesfrom 15 to 20 g, that coincides with the mean testis weight at the attainment of sexual
maturity. This increase becomes slower at testis weight of 70 g or more where themales attain full maturity. These suggest that the testis grows with the increase ofdiameter of seminiferous tubule till about 70 g, and then the testis weight and thediameter of seminiferous tubule show no significant correlation.

Seasonal change of reproductive activity in the testis
In order to find out the seasonal change of reproductive activity in the testis,studies were made on the variations of testis weight, of the diameter of seminiferous
tubule, and of the ratio of mature males in type Miii to the total mature males. Table 8 shows the variations by ten days period. This Table indicates that there is noseasonal change in both the testis weight and seminiferous tubule size for immatureand pubertal males during early October and middle December. As for the mature• -Octobero --- November• -·- December
Cl

200

c:
Ill

-.
I ll

-

150

-..

0

..c:

~

t\

100

: \ It

Cl

.
. 50

I

?

/

;:

~I\ R
I~
ii\~/\\!\,''it\•If H I I
\

,,

/'
p

c:

0

II
/\

t/

0

\

\

I

:::;:

.l

\

b

&j1.,,,\. !·"'·\..i''V/

I

f

_,l"

J\

p'

1

....

J"-1.

.6 •.

0 LI:!:~:i::l.....L..L..W....W....L-J'"-L-L..l-._,_.L..L.L...L...W...J....J.-l....1-L-JL.-L-'--L..J
25
30
15
20
10
5
0
Age

in

years

Fig. 8. Relation between age and the mean weight of the left testis. Closed circles(solid line) indicate the males caught in October, open circles (dotted line) themales in November, and closed squares (chain line) the males in December.
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

GROWTH AND REPRODUCTION OF STRIPED DOLPHIN

37

males, the seasonal variations of the testis weight, of the seminiferous tubule size, andof the ratio of the mature males in type MIU are also shown in Table 8. This indicates that the testis weight, the tubule size, and the ratio of mature males in type
MIU gradually decrease from early October till middle December. As it is expected that such a seasonal change of the reproductive activity in the testis might
be affected by the difference of the age composition of the animals, the testis weightof the males at each age was analized by each month from October to December(Fig. 8). This shows that after the mean age at the attainment of sexual maturity(8. 7 years), the mean testis weight is heaviest in October and lightest in December.
From these informations, it is suggested that the reproductive activity of thetestis is highest in October and then it gradually decreases till December between
October and December. This does not well coincide with the main mating seasons estimated from the latter part of this study. Such a seasonal change of reproductive activity of the mature males seems to be affected by the difference of thetime in the migration period of mature males into the fishing area, because the sampling period is short.
REPRODUCTION IN THE FEMALE

The maturiry
In order to determine the sexual conditions of the females, the ovaries, the mammary gland, and the fetuses were examined in details. Immature animals were identified as those that had the ovaries with no corpus luteum or albicans, pregnant ones
as those that had the ovaries with corpus luteum, the lactating ones as those had the

01

c
.>-

....

Cl

>

0

--

5

<I>

0

.c

01
<I>

3::
0

5
Age

10
ii')

yea.rs.

Fig. 9. Relation between age and the left ovary weight.' Double crosses indicate
the mean weight of the left ovary.
Sci. Rep. Whal.es Res. Inst.,

No. 29, 1977.

MIYAZAKI

38

mammary gland secreting milk, and the resting females as those that were matures
but neither pregnant nor lactating.
The pubertal females were identified by the following method. As the leftovary of S. coeruleoalba becomes mature earlier than the right (Ohsumi 1964), therelation between the weight of the left ovary of the immature and age is shown in
Fig. 9. This shows that the weight of the ovary was about 2.0 g or less during 2
and 6 years, and it rapidly increases after the age of 6 years, when the mature female
first appears. The weight frequencies of the left ovary with one corpus albicans(251 individuals) and of the left ovary with no corpus albicans or luteum (191 individuals) are shown in Fig. 10. The former had a mode in 3.5 to 4.0 g and the

Ill

100

c
.i::

n.
0
-0
~

0

50

"'

..CJ

E
:J

z
0
0

'·

2
Weight

0 f

left

8

6
ovary

in

10

g.

Fig. 10., Frequency of the left ovary weight. White squares indicate the left ovary
with no corpus albicans and black the left ovary with one corpus albicans.

latter also one in 1.0 to 1.5 g. This indicates that the weight frequency of the leftovary can be divided into two groups at the ovary weight of approximately 2.0 g.
From these informations the pubertal females were tentatively defined as the immature females who had the left ovary weighing 2.0 g or more. The youngest pubertal
female was 2.5 years and the oldest immature female was 12.5 years. The ratio of
the pubertal females to the total females at each age is shown in Table 7. The
relation between that ratio and age in the range from 3.5 to 11.5 years can be shownby a straight line. Calculation by the least squares method gives the formula,y=l3.1883x-42.9792 r=0.9803; x: age in year, y: the ratio, r: correlation
coefficient. The age when 50% of the animals attain the puberty is 7.1 years, andthe body length at this age is 209 cm as indicated by the mean growth curve (Fig.
4).
Table 7 shows the ratio of mature females to the total females at each age. The
youngest mature female was 4.5 years and the oldest pubertal was 12.5 years. The
relation between this ratio and age in the range from 5.5 to 12.5 years can be shownby a straight line. The following formula was obtained by the least squares method,
Sci. Rep. Whales Res. Inst.,
No. 29, 197.

GROWTH AND REPRODUCTION OF STRIPED DOLPHIN

39

y= 15.1036x-83.0946 r=0.9846; x: age in year, y: the ratio, r: correlation coefficient. The age when 50% of the animals attain sexual maturity is 8.8 years,
and the body length at this age is 216 cm as indicated by the mean growth curve(Fig. 4).

Diameter of corpus luteum
Fig. 11 shows the relation between the mean diameters of corpus luteum of 206
pregnant females and the time in months after the start of the last gestation. The
date of conception of pregnant female was estimated from the date of kill and thetime after conception given by the fetus size on the basis of the mean growth curve(Fig. 15). The pregnant female confirmed no fetus was tentatively considered as

30

E

25

E

0

c:

·-

20
c:
0

.. 1 5
E
Cl

0

10

5

-

I
I

Cl

, .

a..

:!
1 .•

-1~2~~~~~~0~~-'-----'--"--"-,2-L--l.--l.--1--1--12_4_i__,__,__,__J

MonthsFig. 11. Change of the diameter of corpora lutea during the period of pregnancy
and regression of the diameter of corpora albicantia after parturition. Closed
circles indicate the reliable combinations obtained from Fig. 13 and open circles
the mean diameter of corpora lutea in the interval of 0.25 month.

the earliest pregnant female. The mean diameter of corpus luteum of these females
was 20. 7 mm. It may continue the growth until 3 months after the conception andattain the diameter of 29.3 mm. Then the mean diameter of corpus luteum slightly
decreases with the lapse of time. If the regression line is calculated by the leastsquares, it gives the relation: y=-0.447lx+23.5098, where y is the mean diameterin mm and x is the proceeding time after conception. The mean diameter at thetime of parturition was calculated at 23.5 mm from this formula.

Regression of corpus albicans
Fig. 12 shows frequency of diameters of corpora albicantia at each age. The
modal diameter gradually decreases with the increase of the age of the animal until
Sci. Rep. Whales Res. Inst.,

No. 29, 1977.

40

MIYAZAKI

14.5 years. Then the highest peak of the mode stays between 2 and 5 mm in diameter. The minimum size of the corpora albicantia was 2.3 mm. These indicatethat the corpora albicantia reaches to final size within several years after the startof regression and may stay in the ovary all the life time.
The regression curve of the diameter of corpora albicantia was estimated by themethod of Kasuya et al. (1974). As the size frequency of the largest corpora albicantia of lactating females in the same school may represent the frequency of parturition seasons, the length frequencies of calves and size frequencies of the largest
corpora albicantia oflactating females in corresponding schools are shown in Fig. 13.
The time after parturition was estimated from the mean modal length of calves on
the basis of the mean growth curve (Fig. 4).
No
5

2

11

2 3 24ofcorpora2 0 1 9 24 2 3 1t

10

4

2

2

6

E 10
E
c

·....

...

<I>

<I>

E
a 5

''

--

0

10

15
Age

20
in

25

years

Fig. 12. Distribution of the diameter of corpora albicantia. The dotted line indicates the position of the mode and the numbers at the top show the sample size.

The mean modal diameters of the largest corpora albicantia oflactating females
were plotted against the time after parturition in Fig. 11. It shows that the mean
diameter of corpora lutea at parturition (23.5 mm) rapidly decreases to 7.0 mm
within 4 months. Then the speed of regression gradually slows down and after 18
months the diameter decreases in an almost straight line. However, it is difficult todistinguish between the corpora albicantia of ovulation and those of the last parturition. If a few probable corpora albicantia of ovulation are omitted as in thecase of S. attenuata (Kasuya et al. 1974), the regression curve of the diameter of corpora albicantia seems to become slightly earlier than that expected here.

Ovulation diagram
Of 296 pregnant females, the 26 females on which all the ovulations occured
within 12 months before the last conception were picked up in order to make ovulaSci. Rep. Whales Res. Inst.,

No. 29, 1977.

GROWTH AND REPRODUCTION OF STRIPED DOLPHIN
8 0 d y120

100

length

140

41

cm

160

180

200

I

29

33
I

34
36
37
39
40
42

---43

44

20

15
D

10

5

ameter(mm)

0Fig. 13. Comparison of the frequency of the diameter of the largest corpora albicantia of lactating females (black square) and the length frequency of juvenile
calves (white square). The numbers at the left indicate the school no.

tion diagram. All corpora albicantia of these pregnant females may be probably corpora albicantia of ovulation, because these pregnant females were not synchronously
lactating. This diagram was made by finding out the conception date of the pregnant females from the kill date and fetus size, and the ovulation date of them fromthe size of corpora albicans and the regression curve of corpora albicans. Fig. 14
shows ovulation diagrams of each pregnant female. This figure shows that all theanimals have not regular ovulation rhythm. In the animals of field no. 29 fromschool no. 15, of no. 13 from school no. 34, and of no. E6 from school no. 42, theovulation occurs at about 4 months interval and sometimes does at approximately
one month or less interval. It also occurs at about 8 months interval in the animals
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

42

MIYAZAKIof field no. El from school no. 36, of no. 44 from school no. 38, and of no. 344 fromschool no. 44. These suggests that the ovulation may usually occur at about 4
months or 4 x N months interval (N: integer), and sometimes at approximately
one month or less interval. Accordingly the ovulation of the species may occur by
combination of several ovulation intervals.

Schoo I Fie I d
n o

no

27

14

29

2

29

12

29

15

29

22

34

13

34

15

34

42

34

E5

36

E1

36

E6

38

18

38

3"

38

43

38

44

39

10

40

I8

40

35

40

107

42

E5

42

ES

43

121

44

135

44

232

44

29 0

44

34 4

...
.
..
..

c 1

•

2

M

0

3

4

6

5

h

s

8

9 10 11 12

7

No.of
No.of
corporc corpora

0

0

0

0

0

0

0

0

0

0
0

«>

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

I

n

0
0
0

0

0

0
0

•o
«>

•

0

•

0

0

0

00

0
0
0
0

0

0
0

0 0
0
0

0

0

0

0

0
0

0

0

0
0

0

0
0

tut ea albicontia
1

3

1

2

1

3

1

2

1

1

1

2

1

1

1

3

1

1

1

1

1

1

1

2

1

4

1

1

1

1

1

3

1

3

1

1

1

2

1

I

1

3

1

2

1

4

1

2

1

1

1

1

Fig. 14. Ovulation diagrams of 26 pregnant females. Closed circles indicate thecorpora albicantia of pregnancy and open circles the corpora albicantia of ovulation. C means conception date. For explanation see text.

Mating season
Since the main sampling period was limited in October to December, it is difficult to define the mating season of S. coeruleoalba with precision. In this study themating season of the species was estimated from the following two methods.
First method: Length frequencies of 603 fetuses and 73 newborn calves bymonth are shown in Fig. 15. Records of 21 individuals caught in May 1951 werecited from Nishiwaki and Yagi (1953). As they did not report the body length offetuses smaller than 15 cm but gave the range and the number of fetuses, the middle
value of the range was used in this study. Fig. 15 shows that there are three peaks inthe body length frequency in October, 10.0, 68.3, and 110 cm and also in November,
5.0, 45.0, and 78.3 cm. Laws (1959) showed that fetal growth in odontoceti can. be described by a linear plot oflength except for the very early stage of growth. As
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

43

GROWTH AND REPRODUCTION OF STRIPED DOLPHIN

the gestation length of S. coeru:eoalba was estimated at 12 months (Kasuya 1972)
and the mean body length at birth of the species was about 100 cm (see page 25), if
Lto of Laws (1959) is tentatively .used as 0.15 x gestation length, the fetal growthrate in the linear plot of length is calculated at 9.8 cm per one month. Taking
account of this fetal growth rate and also by using the method of Laws (1959), themean fetal growth curve can ?e drawn from the following four points, 8.1 cm in May,.o cm in October, 78.3 cm m November, and 94.0 cm inJ anuary (Fig. 15). When
68
this growth curve is moved for 4 months, any mode observed in Fig. 15 well fits to
it. On the other hand, from ~he differences of the mean body lengths between
these peaks at each month, the mtervals of the. mating seasons are estimated as 3.4
months (mean: 4.5 months) on the basis of this fetal growth rate. These60:~g~est that the mating season may occur in the interval of approximately 4 months.

E

100

u

--~Y : /Ieng! h at birth---

.-c

-"'

.c

c

-"' 5.0
,,>0

'1l

0
J

F

M

A

M

A

S

0

N

D

F

MonthsFig. 1 . Body length frequencies of .fetuses and newborn calves by month. The
5
feta! growth curve is dra_w~ pre~ummg 12 ~onths of gestation. The specimens in
May are cited from N1sh1wak1 and Yagi (1953). White squares indicate thefetuses, black squares the newborn calves, and closed circles the mean body lengthin each mode.

Second method: Since the gest~tion length of S. coeruleoalba was 12 months (Kasuya) the mating season was estimated from the parturition season on the basis of1972
h p~rturition dates of 567 fetuses, 238 newborn calves younger than 1.0 year (ort e II r than 166 cm), and 144 juvenile calves from 1 to 2 years of the age (or from
sma e
..
d
cm to 180 cm). The partunt10n ate of the animal was predicted from the166
kill date and from body lengt~ as indicated by the mean fetal and postnatal growth
curve. The seasonal fluctuation of the parturition is shown in Fig. 16, with the
49 specimens caught from 1968 to 1972. Fig. 16 shows that there are year-to-year
9variations in the timing and the number of mating peaks, and when the data for all
years are combined it can be said th.at the mating season is prolonged, with threehigher points in Feburary to May, ~~July to September, and in December. To
estimate the interval of the partunt1on date, the frequency of parturition dateSci. &p. Whales Res• .lnst.,

No. 29, 1977.

44

MIYAZAKI
1966

60

"'c:

40

.c:
a.

20

196 7

·1 9 6 91 9 6B

1sio

0

0
"O

150

Tola I

6

60
40

.a

E
~

z

50

20
0
M

0

n

h

s

Fig. 16. Frequencies of parturition dates estimated from the body length of fetuses
and postnatal calves on the basis of the mean growth curve. Black squares indicate the parturition dates estimated from fetus size, striped squares from thebody length of newborns younger than 1 year old, and white from the body lengthof the calves at the age between 1 and 2 years. Double crosses indicate peak.
TABLE 9.
Stage or age
fetus

0.5
1.5
2.5
3.5
4.5
5.5
6.5
7.5
8.5
9.5
10.5
11.5
12.5
13.5
14.5
15.5
16.5
17.5
18.5
19,5
20.5Total*

SEX RATIO OF S. COERULEOALBA BY AGE GROUPS
No. of males

No. of females

269

247
54
66
85
106
99
82
64
53
74
72
69
96
106
85
81
78
69
57
40
40
59
1,535

71

60
93
122
135
139
114
139
133
105
98
59
86
71
72
42
41
48
39
30
55
1,752

} 131
875

}

419

327

} 120
563

}

428

424

Sex ratio

1.09
1.31
0.91
1.09
1.15
1.36
I. 70
I. 78
2.62
1.80
1.46
1.42
0.61
0.81
0.84
0.89
0.54
0.59
0.84
0.98
0.75
0.93
1.14

} 1.09
1.55

}

0.98

0.77

* exclude the fetuses.
Sci. Rep. Whales Res. Inst.,
No. 29, 197..;.

GROWTH AND REPRODUCTION OF STRIPED DOLPHIN

45

between 1969 and 1972 was available, because the frequency in these years was composed of the data of three stages, which were fetus, newborn calf, and juvenile calf
stages. The interval between the nearest peaks ranges from 3 to 7 months (mean 4. 7
months). This indicates that the mating season of the species may occur in the interval from 4 to 5 months.
From above informations it is concluded that there are three mating seasons ina year, namely, from Feburary to May, from July to September, and in December,and the mating season may occur in the interval from 4 to 5 months.

Sex ratio
The sex ratio in this study is shown by the number of males per one female.
The overall sex ratio was 1.14. Table 9 shows the change of the sex ratio in relation to the age of dolphins. In both the fetuses and newborn animals of the age
younger than 2.0 years, the number of males slightly exceeds that of females. The
ratio of the males at the age between 2 and 9 years is extraordinary high. Thissuggests that there is sexual segregation in this period. The number of males isalmost equal to that of females in the young mature animals at the age between 9
and 14 years. However, the ratio of the males at the age older than 14 years is toolow. This suggests that the mortality of the older mature males higher than thatof females at the same age group.
DISCUSSION

It was reported that a pair of opaque (in summer) and translucent (in winter)layer is annually accumulated in the case of Tursiops truncatus (Sergeant 1959),
Globicephala melaena (Sergeant 1962), Physeter catodon (Ohsumi et al. 1963), andStenella attenuata (Kasuya et al. 1974). The seasonal change of the dentinal layers
in the present results reveals good agreement with those of the above four species.
On the basis of the comparison of the dentinal and cemental layers of the same
tooth on S. coeruleoalba, Kasuya (1976) indicated that the accumulation of dentinal
growth layers ceases at a large variety of the age above 11 dentinal layers and thatthe accumulation of cemental layers continues longer. However, the dentinal
growth layer is more useful than the cemental layer to determine the age in theyounger animals in which the former is more readable than the latter. Thus thepresent study analized the growth and reproduction of the animals younger than
13.5 years old by means ofdentinal growth layers.
Ohsumi (1966) showed an allometric relationship, B=0.532 M 0 • 916 , between
mean body length at birth (B in m) and that of female at the attainment of sexual
maturity (M in m) for Physeter, Berardius and several species of Delphinidae. If
this formula is applied for S. coeruleoalba assuming M=2.16 (m), 1.08 m is obtained
as the mean body length at birth. This figure is too larger than the length obtainedin this study. Same tendency is observed in S. longirostris (Perrin et al. 1975),
S. attenuata in the Pacific coast of Japan (Kasuya et al. 1974), and S. attenuata in theoffshore eastern tropical Pacific (Perrin et al. 1976). On the other hand the ratios
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

46

MIYAZAKIof the mean length at birth to the mean length of the females at attainment of sexual
maturity were calculated as 0.45, 0.49, 0.46, and 0.46 in S. longirostris (Perrin et al.
1975), S. attenuata in the Pacific coast of Japan (Kasuya et al. 1974), S. attenuata inthe offshore eastern tropical Pacific (Perrin et al. 1976), and S. coeruleoalba (this study),
respectively. The constancy of these values clearly indicates that the mean length
at birth well correlates with that of the females at the attainment of sexual maturity
in the genus of Stenella. Then the relation between the mean length of the females
at the attainment of sexual maturity and the mean length at birth in Stenella wascalculated by the least squares method. This gives the relation y=0.4758x- l.9152(r=0.9584), where y is the mean length at birth in cm, x is the mean length of thefemales at attainment of sexual maturity in cm, and r is correlation coefficient.
According to the observations on T. truncatus born and kept in aquallia (Tabolga
and Essapian 1957, Nakajima et al. 1963) and to the examination of stomach contents on S. attenuata (Kasuya et al. 1974), these species start feeding on solid food fromabout 0.5 year old. This coincides with the result obtained on S. coeruleoalba in thisstudy. T. truncatus continue to take both solid and milk till about 1.5 years. Thisis similar to the present result on S. coeruleoalba. However, Kasuya and Miyazaki(1976) pointed out that the length oflactation in S. coeruleoalba became shorter withthe decrease of population size. On this problem further study should be done in
the future.
According to Kasuya et al. (1974) and Perrin et al. (1976) the age of S. attenuata
at attainment of sexual maturity in the female is slightly younger than that in the
male. However, the present study indicates that the sexual maturity in S. coeruleoalba
is attained at about 9 years of the age in both sexes. This result well coincides withthat in S. coeruleoalba obtained by Kasuya (1972, 1976).
Kasuya (1972) showed that the mating seasons of S. coeruleoalba were expected
in November and December, and in May and June. The present study, however,shows that there are three mating seasons in a year, namely, from February to May,
from July to September, and in December. This is rather similar to result of S. attenuata (Kasuya et al. 1974). According to Kasuya et al. (1974), the species in thecolder waters have one mating season in spring or in summer and those in the warmer
waters have two or three in a year. The present result seems to support this idea.
The present work shows that the sex ratio at birth is almost parity, indicating
coincidence with the case of S. attenuata in the offshore eastern tropical Pacific (Perrin
et al. 1975). However, in the cases of S. attenuata in the Pacific coast of Japan(Kasuya et al. 1974) and S. longirostris (Perrin et al. 1975) the number of the males
born slightly exceeds that of the females suggesting that the sex ratio at birth appears to be dependant on the population, but not on the species.
For S. attenuata (Kasuya et al. 1974, Perrin et al. 1976) and S. longirostris (Perrin
et al. 1975) it was reported that the mortality rate for the adult male was higher thanthat for the adult female. The present study that confirms these observations
strongly suggests that mortality rate of the adult male is higher than that of thefemale in the genus Stenella.
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

GROWTH AND REPRODUCTION OF STRIPED DOLPHIN

47

ACKNOWLEDGMENTS

The collections of specimens were made under the kind help of the fishermen's cooperative unions at Kawana, Futo, and Taiji. I am indebted to Dr. T. Kasuya of
the Ocean Research Institute of Tokyo University, Dr. K. Hirose ofTokai Regional
Fisheries Research Laboratory, and Mr. N. Oguro of the Oyster Research Institutefor collecting the data and samples. The greatest thanks are due to Dr. T. Kasuya,
and Professor M. Nishiwaki and Dr. T. Higa of Department of Marine Sciences,
University of the Ryukyus, who kindly read the manuscript and provided useful
criticism. I also thank to the following persons for their kind help and valuableadvices: Drs. T. Kajihara and K. Numachi of the Ocean Research Institute ofTokyo University, and Professor T. Fujiyama of Department of Marine Sciences,
University of the Ryukyus.
REFERENCES
HIROSE, K., T. KASUYA, T. KAZIHARA and M. NISHIWAKI, 1970. Biological study of the corpus luteum
and the corpus albicans of blue white dolphin (Stenetla caeruleoalba). J. Mamm. Soc. Japan, 5 (1): 3339.
HIROSE, K., and M. NISHIWAKI, 1971. Biological study on the testis of blue white dolphin, Stenella caeruleoalba. J. Mamm. Soc. Japan, 5 (3): 91-98.
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.
KASUYA, T., 1976. Reconsideration of life history parameters of the spotted and striped dolppins based on
cementa! layers. Sci. Rep. Whales Res. Inst., 28 : 73-106.
KAsUYA, T. and N. MIYAZAKI, 1976. The stock of Stenella coeruleoalba off the Pacific coast of Japan.
ACMRR/MM/SC 25, 37 p.
KASUYA, T., N. MIYAZAKI and W. H. DAWBIN, 1974. Growth and reproduction of Stenella attenuata in the
Pacific coast of Japan. Sci. Rep. Whales Res. Inst., 26: 157-226.
LAWS, R. M., 1959. The foetal growth of whales with special reference to the fin whale Balaenoptera physalus Linn. Discovery Rep., 29: 281-308.
MIYAZAKI, N., T. KASUYA, and M. NISHIWAKI, 1974. Distribution and migration of two kinds of Stenellain the Pacific coast of Japan. Sci. Rep. Whales Res. Inst. 26: 227-243.
NAKAJIMA, M., K. TAKAHASHI, M. OouRA, and K. SAWAURA, 1963. On the growth of infants of the small
size toothed whales. J. Jap. Ass. :(.ool. Gardens and Aquarium, 5 (I): 16-22. (in Japanese).
N1SHIWAK1, M., and T. YAGI, 1953. On the growth of teeth in a dolphin (Prodelphinus caeruleoalba) (!).
Sci. Rep. Whales Res. Inst., 8: 133-146.
N1SHIWAKI, M., 1975. Ecological aspects of smaller cetaceans, with emphasis on the striped dolphin(Stenella coeruleoalba). J. Fish. Res. Board Canada, 32 (7): 1069-1072.
OHSUMI, 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.
OHSUMI, S., 1966. Allomorphosis between body length at sexual maturity and body length at birth in the
cetacea. J. Mamm. Soc. Japan, 3 (I): 3-7.
OHSUMI, S., 1972. Catch of marine mammals, mainly of small cetaceans, by local fisheries along the coastof Japan. Bull. Far Seas Fish. Res. Lab. (Shimizu, Jap.), 7: 137-166.
0HSUMI, S., T. KASUYA, and M. N1sHIWAKI, 1963. The accumulation rate of dentinal growth layers in the
maxillary tooth of the sperm whale. Sci. Rep. Whales Res. Inst., 17 : 15-35.
PERRIN, W. F., D. B. HOLTS, and R. B. MILLER, 1975. Preliminary estimates of some parameters of growth
and reproduction of the eastern spinner porpoise, Stenella longirostris subspecies. Southwest Fish. Cent.
Set. Rep. Whales Res. Inst.,

No. 29, 1977.

48

MIYAZAKI

Administrative Rep. No. LJ-75-66.
PERRIN, W. F., J. M. CoE, and J. R. ZWEIFEL, 1976. Growth and reproduction of the spotted porpoise,
Stenella attenuata, in the offshore eastern tropical Pacific. Fish. Bull., 74 (2) : 229-269.
SERGEANT, D. E., 1959. Age determination of odontocete whales from dentinal growth layers. Norsk
Hvalfangst-Tid., 48 (6) ; 273-288.
SERGEANT, D. E., 1962. The biology of the pilot or pothead whale, Globicephala melaena (Traill) in Newfoundland waters. Bull. Fish. Res. Bd. Canada., 132: 1-84.
TABOLGA, M. C., and F. S. EssAPIAN, 1957. The behavior of the bottle-nosed dolphin (Tursiops truncatus);
mating, pregnancy, parturition, and mother-infant behavior. Z,oologica, 42 (1): 11-31.

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

ON THE FOOD OF BRYDE'S WHALES CAUGHT IN
THE SOUTH PACIFIC AND INDIAN OCEANS
AKITO KAWAMURA*
Whales Research Institute, Tokyo

ABSTRACT

A total of 225 Bryde's whales was caught in the Coral Sea, South Pacificand southwestern Indian Oceans during the 1976/77 Antarctic season under
the scheme of special permission (Figs. lA-B), and their stomach contents alongwith feeding conditions in terms of the state ofrepletion were examined. In theSouth Pacific regions 75% of animals was found to be repleted with under various state whereas it was 46. 7% in the animals caught in the temperate Indian Ocean. (Tables lA-B). The occurrence of fully repleted animal during
the daytime suggests that there seems to exist a considerable availability of
whales food even in the pelagic waters over the tropics (Tables 2A-B). The
stomach contents were solely comprised of three species of euphausiids : Euphausia diomedeae, Euphausia recurva and Thysanoessa gregaria. There found toexist a possible differences in the fashion of geographical distributions among
those euphausiid species as whales food (Table 3). Both E. diomedeae and E.
recurva occurred dominantly over the whaling regions in question with monospecific or mingled composition whereas Th. gregaria alone was completely absent
from the Indian Ocean animals.
INTRODUCTION

During 1976/77 Antarctic season two Japanese whaling fleets, Tonan Maru
No. 2 and Nisshin Maru No. 3, caught a total of 225 southern Bryde's whales in the
Coral Sea, tropical South Pacific and southwestern Indian Oceans under the schemeof special permission for the scientific purpose.
The report on the general topics and some biological observations performed on
those Bryde's whales was preliminarily documented by Ohsumi (IWC/SC/38/1977).
This report deals with the food habits of the Bryde's whales which are identicalto that above mentioned but very briefly since the examination on the stomach contents collected by each factory ship are still halfway of microscopic observations atpresent. Therefore, the argument was focussed on discussing the marine biological purport for taking the whales under special permission rather than describing
the result in detail. However, the article as a whole hopefully be regarded as asupplement to the document by Ohsumi.

* Present address: Faculty of Fisheries, Hokkaido University, Hakodate, Hokkaido.
Sci. Rep. Whales Res. Inst.,

No. 29, 1977, 49-58.

KAWAMURA

50

MATERIAL

Seven Bryde's whales out of 225 animals were caught in the Coral Sea during
October 24-25, 1976, and 113 were caught in the tropical South Pacific between
Fiji Islands and New Zealand during October 30-November 5, 1976. The rest 105
animals came from the catch in the waters off Madagascar, southwestern Indian
Ocean. The approximate locality where the catches took place is demonstrated by
the hatched squares in Figs. IA and lB.
""~01:0,.,_~ ~ <'70./\t
~~

I's

~\,.

CORAL SEA
7 animals

NEW HEBRIDES.cf1 FIJI IS.

q,,

October 24-25, 1976

20·'

NEW CALEDONIA
AUSTRALIA30·~

113 animals

October 30N ovember 5,1976~SOUTH40·

NEW ZEALA~-f/\jFig.IA.
E 120°

140'

130°

150°

160°

PACIFIC

d·
170°

11o·w

180'

lo·
SOUTH AFRICA

20'

r1

MUADAGASCARINDIAN OCEAN
30·

105 animals
March 7-13,1977

Fig.lB.

_ _,
70° E

40°'---'---'---'---"'---'----'-~-'---'-----'----'----'--_,___~__.

S Q°

10'

20·

30"

40'

50°

60°

Figs. IA-B. Whaling ground for the Bryde's whales caught by Japanese whaling
fleets, (IA) Tonan Maru No. 2 and (lB) Nisshin Maru No. 3, under the special
permission for the season of 1976/77. Location of catch is indicated by the hatched squares framed by the farthest extremes of catch positions.
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

51

FOOD OF BRYDE'S WHALES

A total of 121 stomach contents was collected from the identical number ofanimals, of which 69 samples were obtained from the South Pacific and Coral Sea
regions, and 52 were from the southwestern Indian Ocean.
The collected stomach contents were preserved in 10% formalin solution. Although a considerable amount of the stomach contents was heavily digested leaving
a very small fraction of the appendages of prey organisms, it was rather easy to identify euphausiid species by the remains of male copulatory organ on the 1 st-2 ndswimming legs and spermatophore in female since there was quite clear biasing insex composition by each euphausiid species.
Apart from sampling the stomach contents, eye observations on the stomach ofeach carcass were made by a personnel on board, and the results were recorded by
the kind of food organisms on all animals. By examining this results, there foundno descriptions of food items other than euphausiids.
RESULT

Stomach condition in general
The overall state concerning the amount of stomach contents was based on eye
observations by classifing it into five quantitative categories. One of summed up figures was given in Tables IA and lB by the whaling ground. In the animals caught
in the Coral Sea and tropical South Pacific waters, 75% of animals were found to
be repleted with food to some extent under varying quantity. Although the majority of those repleted animals showed few in the quantity of stomach contents, say,
57.5% of animals were repleted less than halfofthe stomach volume, it is noteworthy
or even amazing that there occurred 17 .5% of animals which were repleted almost
fully(' Rich' plus 'Full' in the table-A) in those pelagic waters of the tropics where
the quantitative distribution of planktonic organisms is very scarce in general.
TABLES lA-B. THE OVERALL STATE OF THE STOMACH CONDITION IN BRYDE'S
WHALES CAUGHT IN THE CORAL SEA AND SOUTH PACIFIC OCEAN
DURING OCTOBER 24-NOVEMBER 5, 1976 (A), AND IN THE
SOUTHWESTERN INDIAN OCEAN DURING
MARCH 7-13, 1977 (B).
(A)*
Amount ofstomach contents

Empty

Few

Moderate

Rich

Full

No. of animalo/o to total

30
25.0

49
40.8

20
16.7

13
10.8

8
6.7

(= 120)(=100)* catch by the Tonan Maru No. 2 fleet(B) **
Amount ofstomach contents

Empty

Few

Moderate

Rich

Full

No. of animal

56
53.3

21
20.0

10
9.6

1
0.9

17
16.2

% to total** catch by the Nisshin Maru No. 3 fleet
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

(=105)(=100)

52

KAWAMURA

In contrast to the animals in the South Pacific regions, there occurred considerably large number of poorly fed animals in the southwestern Indian Ocean.
The number of whales with empty stomach roughly doubled in this whaling ground.
However, there still exists about 50% of animals of being well repleted stomach,and the percentage figures combined both ' Rich ' and ' Full ' are very similar tothat found in the South Pacific animals.
The stomach conditions in southern blue and fin whales, for instance, show veryfrequent occurrence in the number of animals with empty stomach in the Ross Sea
region, and its percentage figures usually vary between 40% and 57% (Kawamura,1977). By comparing these figures with those found in the southern Bryde's whales,
it may be considered that the relatively frequent occurrence of well fed animals bothin the South Pacific and southwestern Indian Oceans is significant evidence in connection with dealing the ecosystem through food webs in the pelagic waters of thetropics.

Occurrence of stomach contents by the local time
In the animals caught in the South Pacific and Coral Sea regions, there seems
to be no clear trends in the stomach condition by the local time of catch. The
animal caught in October showed somewhat large number in the frequency of empty
stomach (44.4%) while it was reduced to 13.3% in November (Av. 25.0%), butthere was a slight difference in the Indian Ocean. (Tables 2A and 2B).
The number of animals of being repleted stomach in terms of the percentage figures is very large throughout every time series of catch. Both upper and lower mostextremes of the percentage in the South Pacific animals repleted with some amountof food for given time series was 87.5% for 0900 hour and 60.0% for 0800 hour
respectively, while they were 66.7% and 16.7% in the Indian Ocean animals. Thevery high percentage occurrence of animals of repleted stomach through a series ofdaily catch time (0500-1800 hours) suggests that there must be considerably richavailability of food organisms for baleen whales, and that possibly for many other key
members involved in the tropical food webs. No animal with repleted stomach
was found in 0500, 1000 and 1100 hours, but perhaps it was due to poor catch
number during those time zones. One of important facts in Tables 2A and 2B
should be found in the occurrence of ' Rich ' and ' Full ' stomachs during the daytime (1200-1400 hours). These animals undoubtedly preyed upon euphausiids
within the past several hours prior to their capture. This indicates that there
exists an abundant food organisms even during the daytime and that E. diomedeae,
E. recurva and Th. gregaria occur with large biomass by forming the mono-specificsurface swarms instead of remaining in deep waters.
Species ef food organisms
From a total of 121 stomach samples following three species of euphausiid wereindentified:Euphausia diomedeae Ortmann
Euphausia recurva Hansen
Sci. Rep. Whales Res. Inst.,
No 29, 1977.

FOOD OF BRYDE'S WHALES

53

TABLES 2A-B. FREQUENCY DISTRIBUTION OF THE NUMBER OF ANIMALS BY
THE LOCAL TIME OF CATCH AND THE STATE OF STOMACH CONTENTS,(A) OCTOBER-NOVEMBER, 1976 IN THE SOUTH PACIFIC AND CORAL
SEA, AND (B) MARCH, 1977 IN THE SOUTHWESTERN INDIAN OCEAN.
Tonan Maru No. 2 fleet(A)
PeriodAmount ofstomach contents

October 24-30, 1976
Empty

05
06
07
08
09
10
11
12
13
14
15
16
17
18
Total

1
3
3

Total
1
3
5
1
5
1
1
4
3
4
5
6
3
3
45
100.0

2
2
15
33.3

1
2
4.4

5
11.2

3
6.7

Full

Total

Grand
total

November 1-5, 1976
Few

1
2
4

Moderate

6
8
3

2
4
1

3

1
1
3
2
1
2
1

1
4
4
1
1
34
45.3

10
13.3

Full

2
1
1

1
4

20
44.4

continued ...
Empty

Rich

2
1
3

1
1
1
1
1
2
1
4
1

%

Moderate

Few

Rich

2
3
1

18
24.0

06
07
08
09
10
11
12
13
14
15
Total

%
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

5
6.7

8
10.7
(B)

PeriodAmount ofstomach contents

9
18
9
3
1
4
5
4
6
5
8
2
1
75
100.0

3

1
12
23
10
8
2
5
9
7
10
10
14
5
4
120

% animalwith food
66.7
78.3
60.0
87.5
80.0
77.8
85.7
80.0
80.0
71.4
80.0
80.0

Nisshin Maru No. 3 fleet
March 7-13, 1977

Empty

Few

Moderate

1
7
16
6
9
2
7
3
5

1
5
3
6

1
1

56
53.3

l

l

l

2

Full
1
7
3
2
1
2

3

2
2
1
21
20.0

Rich

l

10
9.5

1
1.0

17
16.2

Total
3
14
28
18
11
5
13
6
6
1
105
100.0

% animalwith food
66.7
50.0
42.9
66. 7
18.2
60.0
46.2
50.0
16.7
100.0

54

KAWAMURA

Tlrysanoessa gregaria G.0. Sars
The population of Euphausia diomedeae occurred in the Coral Sea during October was comprised of adult of both sexes except an instance which was solely comprised of female, and there found a single spermatophore attached to the thelycumin female or to the external genital aperture in male in some individuals. In theSouth Pacific and Indian Ocean population of E. diomedeae, however, male individual was complete absent to result complete mono-sexual composition. The stomach contents of Bryde's whales caught in the Coral Sea were represented solely by
E. diomedeae without exception.
In contrast to the case in E. diomedeae, Euphausia recurva population was comprised of adult male. Female did not occur completely in this species. E. recurva
occurred both in the South Pacific and southwestern Indian Ocean, but not in the
Coral Sea. There were no individuals carrying spermatophores in the specimen
came from the tropical Pacific whereas some few individuals from the Indian
Ocean carried a single spermatophore on the genital aperture although the majority was not.
Thysanoessa gregaria was comprised of both adult male and female. Both E.
diomedeae and E. recurva distributed widely over the whaling grounds in question,
TABLE 3. COMPOSITION OF THE FOOD OF BRYDE'S WHALES CAUGHT IN THE
CORAL SEA, SOUTH PACIFIC AND SOUTHWESTERN INDIAN OCEANS
FOR THE 1976/77 ANTARCTIC SEASON. FIGURES IN THE
TABLE INDICATE THE NUMBER OF ANIMALS.
Sea area
Fleet
No. of animals caught
No. of stomach contents examined

S. Pacific & Coral Sea
Tonan Maru No. 2

S. W. Indian Ocean
Nisshin Maru No. 3

120

105
52

Euphausia diomedeae
E diomedeae/E. recurvalJ
E. diomedeae/Th. gregaria
Euphausia recurva
E. recurva""'E. diomedeae 2l
E. recurva/E. diomedeae
E. recurva+E. diomedeae 3l
E. recurvas;,E. diomedeae/Th. gregaria
Euphausia sp. 41
Thysanoessa gregaria
Th. gregaria/E. diomedeae
Th. gregaria/ E. recurva
Th. grPgaria/E. diomedeae+E. recurva

1751

69

12

4
17

l
2

9

15

2

861

3
3
7

5

10
l

3

by the order of dominancy
mixture of closely equal quantity
3l mixture of two species but quantitative share among them is unknown due to heavy digestion<J the fraction of appendages and spermatophore strongly suggest that the species may possibly be composed of E. diomedeae and/or E. recurva
5J of which five animals out of seven in all caught in the Coral Sea are included
6J including one stomach contained a single specimen of hatchetfish
IJ

2l

Sci. Rep. Whales Res. Inst.,

No. 29, 1977.

FOOD OF BRYDE'S WHALES

55

but Th. gregaria tended to show a sporadic occurrence which suggests the presenceof possible five different local groups. There were however, no noticeable indications in the environmental condition which may explain their characteristic occurrence. The occurrence of Th. gregaria was fairly restricted in the whaling groundof the South Pacific regions.
The Bryde's whales caught in the Coral Sea, South Pacific and southwestern
Indian Ocean preyed upon these three euphausiid species with some local differences in the species composition. As it is shown in Table 3 the food of Bryde's whales
which distributes in the pelagic waters of the tropics was found to be comprised ofmonospecific or mixtured swarms of euphausiids. Comparing this with the stomach
contents having been known throughout the so-called boreal and antiboreal feeding
grounds, the revealed composition of prey organisms in terms of the variety of species
in the tropical waters is considered to be rather monotonous. To see Table 3 there
may be found differences but slight between South Pacific and Indian Oceans: Oneof clear differences was complete absence of Th. gregaria from the stomachs in the
Indian Ocean, instead, Euphausia recurva was possibly dominant in this locality. The
result shows in general that both E. diomedeae and E. recurva are considered to bevery important food items among all in a scope of studying the energy flow throughmarine food webs in the tropical seas where micronektonic organisms other thaneuphausiids have been considered likely to be the key biotic group in the ecosystemof those waters.
DISCUSSION

It is well known fact in general that the abundance of zooplankton in the waters
over the tropics is very poor. The stomach contents of surface dwelling fishes suchas albacore, yellowfin and skipjack suggest that micronektonic fishes and squids may
possibly be the key members in the pelagic food webs in those warmer waters (e.g.
Roger and Grandperrin, 1976). Analysing the stomach contents of above mentioned tunas in the tropical Pacific, Roger and Grandperrin (1976) reported that
60% of the diet of tunas was comprised of micronektonic fishes, and euphausiids
accounted only about 12% of the food of preyed fishes or may account only 7% of
the food of tunas through the predation by their prey fishes.
The Bryde's whales have been considered to be the inhabitant of warm watersof the surface temperature higher than 20°C (Omura and Nemoto, 1955). They
possibly share an identical ecosystem with tunas, surface dwelling fishes and othermany micronektons in those tropical waters. The baleen whales undoubtedly feed
to some extent on some organisms while they are in warmer waters. An example
suggesting their active feeding may be found in the behaviour of excreting reddish
faeces by blue whales in the Indian Ocean (Gambell et al., 1974), and the similar
one was observed in Bryde's whales during the marking cruise of Miwa Maru to theequatorial western Pacific (Far Seas Fish. Res. Lab., 197 5; Wada, 197 5 ). By considering those facts along with some speculations, it may be considered quite naturallythat the Bryde's whales are likely to feed mainly on small gregarious fishes, larvae or
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

56

KAWAMURA

juvenile oflarger fishes and/or micronektonic organisms. However, one of the evidences revealed in the present study on the feeding of Bryde's whales that inhabit
in the tropical South Pacific and southwestern Indian Oceans suggested somewhat
different from that have been considered previously. The Bryde's whales underconsideration preyed exclusively upon euphausiids. There occurred no other kindof food organisms. Although the importance of euphausiids as food ofBryde's whalesin the tropical seas is still obscure since the material did not cover over the sufficient period and amounts. However, the fact that euphausiids occurred significantly
over the different time and space suggests their importance as the stable foodstuff not
only for Bryde's whale but also perhaps for all other baleen whale species occurringin those warm waters regardless the origin of whales whether the animals were endemic or migrants. In this respect the Bryde's whales in the tropics are by nomeans at higher trophic level than any other migrating baleen whale species, andthe ecological niche for those Bryde's whales is considered very similar to thatknown throughout balaenopterid whales.
The euphausiids species, E. diomedeae, E. recurva and Th. gregaria are very
common over the waters from tropics toward the warm temperate regions. Usuallythese euphausiids migrate vertically for a considerable distance of about several
hundred meters and are considered seldom to occur in the near surface during thedaytime (e.g. Boden et al., 1955; Ponomareva, 1963; Mauchline and Fisher,1969). According to Roger and Grandperrin (1976), only Stylocheiron species may
become available for its predators during daytime in the tropical Pacific. Euphausia species, on the other hand, may become more important at night (Roger,
1973a, b). However, the occurrence of E. diomedeae, E. recurva and Th. gregaria
largely in the stomach contents of Bryde's whales even in the daytime suggests theprimary importance of these food species at some restricted time and space overthe pelagic waters of the tropics. Apart from the diurnal behaviour pattern, theformation of swarms at this time of the season in these euphausiid species might
relate to their reproduction, which is indicated by an extremely biased sexual composition occurring only male for E. recurva and female for E. diomedeae of the South
Pacific populations, and several other characteristics such as that the spermatophore frequents in E. diomedeae.
The mass occurrence of euphausiids in the tropical seas so abundant as to be utilized by the predators is again significant phenomenon in considering the energy
budget of baleen whales. Through the calculation of energetic budget in the southern baleen whales, Kawamura (1975) suggested that the overall estimations may fulfill the energetic requirements by migrating animals, but at the sametime there exists
very ill fed animals with thin blubber, and these animals perhaps must to feed on
the way to and from the so-called breeding ground in the warmer waters. One ofquestions arose from the discussion was whether there were any possibility to comeacross suitable feeding place for those stenophagous filter feeders in the tropicalseas, and the failure in this may suggests a critical situation for the mulnutritioned
animals. Although the mass occurrence of euphausiids in the austral spring as was
suggested through this study did not coincide with a possible seasons of appearing
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

FOOD OF BRYDE'S WHALEb

57

the migrating whales, it can be said that the swarms of euphausiids may occur over
the whole warmer season at least in some restricted localities. The occurrence of
euphausiids both in October-November and March with considerable availability
may support this, and there have been reported a considerable amount of halfgrown to adult specimens of E. diomedeae occurred during the austral winter in
Siboga-Expedition (Hansen, 1910).
In concluding with the discussion, the occurrence of euphausiid swarms in thetropical South Pacific and in the southwestern Indian Ocean strongly suggests its
importance in considering the pelagic ecosystem through the food webs in the tropics
as well as the identical subject taking place in the feeding ground of the mid~ to higher
latitudes. The consumption of planktonic crustaceans by baleen whales may
amount significantly among many other predators even if the whale does not feedso much as to fulfill its nutritional daily ration. Although the role of euphausiids
in the tropical marine ecosystem does not seem such magnitude as to noticeable
extent in the overall energetic flows, the swarming of these crustaceans may be oneof the phenomena that can not be overlooked from the ecological aspects. The
swarms of euphausiids possibly be utilized largely by many kind of predators in
addition to the Bryde's whales, and the latter undoubtedly accounts an indispensablerole as the biotic members in the tropical marine ecosystem. More accumulation ofthis kind of knowledge is therefore needed to fulfill the biased knowledge both thebiology of whales and biological oceanography since many similar evidences forthe latter topics have been known solely by studying on the food of baleen whales(e.g. Nemoto, 1962; Omori et al., 1972; Kawamura, 1974).
REFERENCES
BODEN, B. P., M. W. JoHNSON, and E. BRINTON, 1955. The Euphausiacea (Crustacea) of the North Pacific. Bull. Scripps Instn. Oceanogr., 6(8): 287-400.
FAR SEAS FISHERIES RESEARCH LABORATORY, 1975. Progress report on whale research. IWC/SC/27/Progress Report, Japan.
GAMBELL, R., P. B. BEST, and D. W. RICE, 1974. Report on the international Indian Ocean whale marking cruise, 24 November 1973-3 February 1974. IWC/SC/26/37.
HANSEN, H.J., 1910. The Schizopoda of the Siboga-Expedition. Siboga Exped., 37: 1-123.
KAWAMURA, A., 1974. Food and feeding ecology in the southern sei whale. Sci. Rep. Whales Res. Inst.,
26: 25-144.
KAWAMURA, A., 1975. A consideration on an available source of energy and its cost for locomotion in fin
whales with special reference to the seasonal migrations. Sci. Rep. Whales Res. Inst., 27: 61-79.
KAWAMURA, A., 1977. An interim consideration on a possible interspecific relation in southern baleen
whales from the viewpoint of their food habits. IWC/SC/12, Special Meeting on southern sei whales,
Tokyo, April 20-27, 1977.
MAUCHLINE, J. and L. R. FISHER, 1969. The Biology of Euphausiids. Advances in Marine Biology, 7. Sir
F. S. Russell and Sir M. Yonge (ed.), Academic Press, London, 454 p.
NEMOTO, T., 1962. Food of baleen whales collected in recent Japanese Antarctic whaling expeditions.
Sci. Rep. Whales Res. Inst., 16: 89-103.
0HSUMI, S., 1977. Provisional report on the Bryde's whales caught under special permit in the southernhemisphere. IWC/SC/38/1977.
0MORI, M., A. KAWAMURA, and Y. ArzAwA, 1972. Sergestes similis Hansen, its distribution and importanceSci. Rep. Whales Res. Inst.,

No. 29, I977.

58

KAWAMURA

as food of fin and sei whales in the North Pacific Ocean. In : Biological Oceanography of the Northern
North Pacific Ocean. Takenouti et al. (ed.), Idemitsu Shoten, Tokyo, 626 p.
OMURA, H. and T. NEMOTO, 1955. Sei whales in the adjacent waters of Japan. III. Relation between
movement and water temperature of the sea. Sci. Rep. Whales Res. Inst., 10: 79-87.
PoNOMAREVA, L. A., 1963. The euphausiids of the North Pacific, their distribution and ecology. Dokl.
Akad. Nauk. SSSR, 1-142. IPST, 1966.
RoGER, C., 1973a. Recherches sur la stituation trophique d'un groupe d'organismes pelagiques (Euphausiacea). II. Comportements nutritionnels. Marine Biology, 18: 317-320.
RoGER, C., 1973b. Ditto. III. Petentiel alimentaire du groupe. Ibid., 18: 321-326.
ROGER, C. and R. GRANDPERRIN, 1976. Pelagic food webs in the tropical Pacific. Limnol. Oceanogr., 21(5); 731-735.
WADA, S., 1975. (Whale marking in the southwestern North Pacific.) Geiken Tsushin, 284: 27-34. (in Japanese).

Note: According to Best (1974) there exist clear difference in the dietary habit of Brycte's whales in theSouth African waters : his ' inshore form ' feeds mainly on fish (Engraulis capensis, Trachurus trachurus,
Sardinops ocellata) whereas 'offshore form' does euphausiids (Euphausia lucens, E. recurva, Nyctiphanes
capensis, Thysanoessa gregaria). As far as this result is concerned, the animals caught in the Coral Sea,
tropical South Pacific, and Indian Ocean seem to represent his ' offshore form '. Although Best's result
provides very important knowledge on the southern Bryde's whales, there was no other way but exclude
his result throughout my discussion since the document (Best, P. B., 1974 : IWC/SC/SP/74/DOC4) has
not been published yet at the moment of publishing this article.

Sci. Rep. Wha!es Res. Inst.,
No. 29, 1977.

HUMPBACK WHALES IN THE HAWAIIAN BREEDINGWATERS: POPULATION AND POD CHARACTERISTICSLOUIS M. HERMAN AND RONALD C. ANTINOJA
Department of Psychology, University of Hawaii

ABSTRACT

Aerial, shipboard, and underwater observations were made during Spring 1976 of the population of humpback whales, Megaptera no1•aeangliae, breeding in Hawaiian waters. Animals were found around all of the major islands,
almost always within the 100 fathom contour, with the bulk of the population
concentrated in regions having the greatest contiguous extent of such water.
Breeding and calf rearing were not confined to any given area. Survey results yielded estimates of from 200 to 250 animals. The birth rate was estimatedas less than 10 %, a low figure of some concern. Coloration characteristics of the
Hawaii population differed considerably from the easten1 North Pacific population of humpback whales, suggesting little genetic exchange with that group.
Differences from the western North Pacific group were less clear, in part because of sparsity of data. Approximately 18% ofthe animals were alone whenobserved ; the remainder were in pods of 2 to 9 animals. Overall there wereconsiderably fewer singletons and considerably larger-sized pods than has been
observed in feeding ground aggregations. A calf was typically found in a multiple-animal pod, consisting of the mother and, most frequently, one other adult" escort " whale. The escort seemed to serve a protective function. The large
majority of the pods were swimming in fairly regular formations in apparent
local migratory movements. Milling pods, with animals contacting one another, or engaging in other behaviors seemingly consistent with sexual courtship or advertisement, was observed in 16 % of the cases. The possibly adverse
effects of increasing public and commercial on-water and in-water whale-watching activites on the reproductive success of the whales was noted.

INTRODUCTION
Each year, during the winter breeding/calving season, a population of humpwhales (Megaptera novaeangliae) migrates into waters adjoining the major Hawaiian
islands. The first arrivals may appear as early as November; peak numbers
occur during February and March, and the last stragglers depart as late as May
or June. From Hawaii, the animals return to summer feeding grounds along the
Alaskan peninsula or elsewhere in the high-latitude regions of the North Pacific.
This report focuses on the description of this population while in Hawaiian waters,
based principally on observations carried out during the Spring of 1976. The
study goals included the determination of areas of principal aggregation and theirfunction, the estimation of population abundance and of the rate at which calves
Sci. Rep. Whales Res. Inst.,
No. 29, 1977, 59-85.

60

HERMAN AND ANTINOJA

were recruited into the population, the description of some of the principal demographic and phenotypical characteristics of the population, the analysis of the organization of pods of whales, and the documentation of behaviors of the animals.
The study was carried out using aerial, shipboard, and underwater visual observations, and included extensive photographic documentation. The analysis of behaviors is reserved for a separate paper.
The humpback whale is part of the family of Balaenopterid whales, or rorquals,
which principally include the blue (Balaenoptera musculus), fin (B. physalus), sei (B.
borealis), Bryde's whale (B. edeni), and piked whale (B. acutorostrata). Rorquals
are cosmopolitan species, generally found in all oceans of the world. They are
distinguished from other mysticete whales by multiple longitudinal ventral grooves
extending from the throat to as far as the navel. These grooves can distend greatly,
like the lower jaw of a pelican, when feeding on the small marine crustacea or small,schooling fish that are their main diet. Additional rorqual characteristics are asmall, posteriorly-placed dorsal fin, and a generally slim, tapered body well adapted
for rapid swimming. Unlike the other rorquals, Megaptera has extremely long(e.g., 3.5 to 4.5 m), highly mobile, pectoral fins; rounded knobby tubercles on theupper jaw and portions of the lower jaw, possibly sensory in function; irregular
protruberances along the leading edges of the pectoral fins; moderately fine serrations or scalloping along the trailing edge of the caudal fin (tail flukes); and an
irregularly shaped dorsal fin. It has been described as stouter of body than otherrorquals, but those seen in Hawaiian waters seem generally slim and graceful inform. The slender form apparently reflects the reduced or even absent food intake,characterizing breeding migrations of humpback whales and other rorquals (Dawbin, 1966; Tomilin, 1967). We occasionally observed some Hawaiian humpback
whales engaging in what appeared to be feeding behaviors.
According to Rice's (1963) data on eastern North Pacific stocks, physicallymature female Megaptera average slightly longer in body length (14.8 m) than domales (13.6 m), though Tomilin (1967) reports somewhat smaller differences. Sexual maturity occurs when the animals are 2-3 m shorter. Newborn calves may
range from 4 to 5 m in length (Nishiwaki, 1972), but in Hawaii some appear to besmaller than the minimum stated. Following sexual maturity at 6-12 years, females
calve generally only every other year, giving birth almost always to a single young.
The gestation period is close to 12 months and the lactation period lasts from 10 to
11 months. Some additional aspects of reproductive biology of humpback whales
are discussed later in this paper. More detailed discussions of general and reproductive biology of Megaptera are available in a number of sources (e.g., Chittleborough,1959, 1965; Mackintosh, 1972; Matthews, 1937; Nishiwaki, 1959; Omura,
1953; Rice, 1963; Symons & Weston, 1958; Tomilin, 1967; Wolman, 1972).
Megaptera, like most other rorquals, engages in long-distance annual migrations
between higher-latitude summer feeding grounds and lower-latitude winter breeding
grounds. Dawbin (1966) described sexual and maturational temporal segregation
during migration and discussed some of the physical and ecological conditions possibly triggering and guiding migration of Southern Hemisphere humpback whales
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

HUMPBACK WHALES OF HAWAII(also see Chittleborough, 1965;

Nishiwaki, 1959, 1960).

61

Unlike other rorquals,

Megaptera prefers breeding grounds in the nearshore, shallow waters around continents or islands at approximately 10° to 20° latitude. In many cases, near-shore
preference increased the vulnerability of Megaptera to whaling.
DISTRIBUTION AND ABUNDANCE OF THE NORTH PACIFIC STOCKThe Hawaiian population is part of the highly-exploited stock of North Pacifichumpback whales. The distribution of this stock has been discussed, directly or
indirectly, in a number of sources (e.g., Kellogg, 1929; Mackintosh, 1947;
Nishiwaki, 1966; Omura, 1955; Rice, 1974; Tomilin, 1967; Townsend,1935). Charts prepared by Omura (1955) and Nishiwaki (1966) and material
provided by Tomilin (1967) reveal the orginal feeding range as extending from the
Sea of Okhotsk on the far western rim of the upper North Pacific to the Gulf of Alaska
on the eastern rim. Within this broad range, the whales were concentrated along
the Kuril Islands and on both sides of Kamchatka Peninsula in the western North
Pacific, within the Bering Sea and northward to the Bering Straits and the Chukchi
Sea, and along the northern and southern shores of the Aleutian chain and the Alaska
Peninsula down through S.E. Alaska.
Three breeding populations are generally recognized according to their separate
migration loci each winter in the tropical zones of the North Pacific. An eastern
Pacific, or American group, migrates southward past the west coasts of Canada andthe United States to calving/breeding grounds in the bays and outlying islands
along the west coasts of Baja California and the Mexican mainland (Kellogg, 1929;
Rice, 1974). A western Pacific, or Asiatic group, seemingly follows a southwesterlyroute along the east coasts of Japan to calving/breeding areas near Taiwan, or further east in the Bonin Islands, the Mariana Islands, and reportedly, the MarshallIslands. According to Kellogg (1929) and Tomilin (1967) some whales may penetrate into the Sea of Japan on their way to the Yellow Sea. Finally, the central
Pacific, or Hawaiian group, migrates into the Hawaiian waters by a route which isstill unknown. Also unknown is the degree to which the three populations disperse
and comingle in their summer feeding grounds, and whether there is any significant
genetic exchange across breeding populations. Ivashin and Rovnin (1967) believe that dispersed groups return to their original breeding grounds and that genetic
exchange is negligible. Coloration data for the different groups, discussed in alater section of this paper, tends to support this contention.
Historically, the humpback whale was hunted in the North Pacific as early as
the l 7th century by Japanese shore whalers using spears and arrows and, later,
nets (Omura et al., 1953). However, major exploitation did not occur until
the 19th and 20th centuries when the stock of North Pacific humpback whales
was extensively hunted throughout its summer feeding grounds by Japanese andRussian pelagic whalers (20th century); along its migratory routes in the eastern and western North Pacific by American and Japanese shore whaling stations;and in many of its tropical calving/breeding areas, principally by American andSci. Rep. Whales Res. Inst ..
No. 29, 1977.

62

HERMAN AND ANTINQJA

Japanese whalers (Omura, 1955; Tomilin, 1967; Townsend, 1935). Its hunting
was finally banned in 1966. At that time there may have been 200-300 animals
remaining in the American population, based on extensive surveys in 1965 of thewinter breeding grounds of this population (Rice, 1974). There were probably
similar numbers remaining in the Hawaiian population, judging from the recent
survey reported in this paper. There appear to have been no formal surveys of the
Asiatic population since 1966. However, the rarity of sightings even before 1966,
as noted by Tomilin (1967) and the fact that western North Pacific concentrations
were always smaller than eastern North Pacific concentrations (Omura, 1955, Appendix 17) suggests that very few animals remained in the Asiatic population by
1966. Optimistically, it would seem that the North Pacific stock in 1966 numberedat most 1000 animals. Stock assessments by Wada (1972) suggested only 1200
animals. Thus, there are no indications of any substantial recovery of the North
Pacific stock since 1966.
Wolman's (1972) brief review of humpback whales included an estimate oforiginal abundance of the North Pacific stock as 4000 animals and Nishiwaki (1959)
suggested 5000-6000 animals. These estimates seem low given the 3037 humpback
whales caught in the North Pacific in the three-year period 1925-27 (International
Whaling Statistics, 1931) and the 3455 caught by Russian pelagic whalers in the
two-year period 1962-63 (International Whaling ·statistics, 1966). Also, the catch
statistics for 1925-27 apparently did not include the take off Kamchatka Peninsulain the western North Pacific (Omura, 1955). Ifwe assume the estimates of Wolman
and Nishiwaki are reasonable, then current abundance may be no more than 1525% of the original stock. Worldwide figures for humpback whale populations
are correspondingly low. The original abundance of the Antarctic stock may
have been as much as 90,000-100,000 animals, but census data between 1965-70
revealed, on the average, a maximum of 2800 animals, or roughly 3% of the original
stock (Chapman, 1974). The Antarctic stock has been protected since 1964. The
eastern North Atlantic stock was decimated before the end of the 19th century andis extremely rare today (Tomilin, 1967). The western North Atlantic groupcurrently numbers roughly 1200 animals (Winn et al., 1975). It has been protected
since 1955, and according to Winn et al. (1975) may not be much below its
numbers at the end of the nineteenth century just before major exploitation began.
Based on the slow recovery rates in other areas (Myers, 1975) and the small catchin the North Atlantic of only 22 whales in 1969/70 under a special permit to take
40, as compared with the total catch of 729 humpback whales in that area in 1903/
04/05 (Mitchell, 1974), it seems more likely that full recovery of the Atlantic grouplies considerably in the future. Chittleborough (1965), for example, estimated thatrecovery of portions of the Antarctic stock to original levels could take more than
65 years, while increases of world stocks to " significant " levels could take 50 years(Anon., 1975). The worldwide protection currently given the humpback whaleby member nations of the International Whaling Commission hopefully will someday enable its reclassification upwards from an endangered species.
Sci. Rep. Whales Res. Inst.,
No. 29, !977.

63

HUMPBACK WHALES OF HAWAIIBACKGROUND OF THE HAWAIIAN POPULATIONThe Hawaiian Island region nicely meets the preferred ecological requisites
for breeding grounds of Megaptera. The eight main Hawaiian Islands (Fig. 1),
around which the whales predominately aggregate, comprise the southeastern portion (Leeward chain) of a linearly arranged archipelago extending some 1300 nm
from Kure atoll in the northwest (178° 30' W, 28° 25' N) to the island of Hawaii
in the southeast. Figure 1 shows some extensive areas surrounding the main islands
160° w

159'

158°

156'

157°

w 155°HAWAIIAN ISLANDS
22°

21°

157°

156°
156°

w 155°

Fig. I. The main islands of the Hawaiian Archipelago. The inset expands thefour-island region of Molokai, Lanai, Maui and Kahoolawe. The dotted lines
are the JOO-fathom contours. Penguin Bank is the entire region within the 100fathom contour extending southwesterly from Laau and Ilio Points, Molokai.

in which the water depth is 100 fathoms or less, especially within the four-island
region of Molokai, Lanai, Maui, and Kahoolawe, and within Penguin Bank extending some 25 nm southwest of Molokai. Between November and March, surface water temperatures remain close to 25° C (77° F), with a near-isothermal layer
extending downward to 50-80 m (Gosline, 1965). Zooplankton is fairly uniformly
distributed throughout the coastal waters, though in markedly lesser concentrations
than in equatorial waters or in waters further to the north and northeast of the islands (King and Demond, 1954; King and Hida, 1954). The relatively low zooplankton abundance and that runoffs from land have little permanent effect on thenearshore environment make for clear waters. The water clarity and the concentration of the whales near shore make for ideal surface and underwater study conditions. Strong northeast trade winds or southern storms occasionally restrict viewing
opportunities, but the majority of the time the whales may be readily observed
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

64

HERMAN AND ANTINOJA

from a number of key shore points or easily accessed by ship or light aircraft.
Prior to the 1976 season, the Hawaiian population had not been studied inany detail. In fact, it seems to have gone almost unnoticed in the scientific literature until relatively recently, as illustrated by a number of compendia on the zoogeography of cetacea that failed to record the population (e.g., Marcuzzi and Pilleri,
1971; Tomilin, 1967). Bryan (1915), in his review of Hawaiian ethnology,. geology, and natural history, seems to be the first to give mention of the population,
but as noted by Tomich (1969) Bryan's documentation is sparse. Unfortunately,
the situation improved little thereafter, being limited mainly to occasional newspaper reports of sightings (see summary in Tomich, 1969). This historical neglect
seem paradoxical given that Hawaii was the commercial hub of North Pacific whaling·in the early and mid-nineteenth century, offering rest, recuperation and reprovisioning to the hundreds of vessels hunting sperm whales in equatorial waters or in
the seas adjacent to Japan, or else searching for right whales in the Bering Sea, theSea of Okhotsk, and in adjacent waters. Apparently, the whalers had little interest in catching or even logging the presence of the seasonally resident humpback
whales in Hawaii, which were of lesser economic importance at the time than were
sperm or right whales. Minor exploitation of the Hawaiian humpback whale
population (and of a few sperm whales) did occur from the late 1840's through to
the late 1860's by shore whaling stations operating mainly from the island of Maui
(Anon. 1848, 1856, 1866; Baldwin, 1958; also see Jones, 1938), but the records
seem too fragmentary to allow for any estimates of nineteenth century abundanceof the humpback whale in Hawaii. The 19th century exploitation by shore stations appears to have begun just about the time when whales, in general, were diminishing in economic importance worldwide. Combined with the apparent
difficulty encountered by the Hawaiian shore stations in capturing the animals,
each operation seems to have petered out only a few years after it began. Exploitation of the at-large North Pacific humpback whale stock in its higher latitude summer
feeding grounds, which certainly must have included portions of the Hawaiian
population was, as noted, a continuing process from the latter part of the nineteenth
century, whenJapanese and, apparently, Russian pelagic whaling began (H. Omura,personal communication), through to the end of 1965.
There is no evidence of any exploitation of the humpback whale by native
Hawaiians prior to the nineteenth century. The antiquities of the Hawaiians,
including their petroglyphs, contain no record of humpback whales, or indeed ofwhales of any type, and there are no Hawaiian whale legends other than a very few
obviously imported from the South Pacific, where native whaling did occur (Beckwith, 1970; Kirtley, 1971; Malo, 1951). The Hawaiian language seems tocontain no special word for humpback whale, though a general word for whale,
kohola, exists, as does a special term, palaoa, for sperm whale teeth or products derived
from the teeth, such as whale-tooth pendants (Malo, 1951; Pukui and Elbert, 1971).
Sperm whales and other toothed whales were apparently washed ashore on occasion,and their teeth became the valued property of the royalty. No similar names forderivatives from baleen whales (such as baleen plates) appear in recorded Hawaiian
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

HUMPBACK WHALES OF HAWAII

65

history or in the language. The sum of the evidence thus suggests that the humpback whale was either of little interest to the pre-nineteenth century Hawaiian natives, or else that the whales were inhabiting different breeding grounds than thoseused today, grounds which were not observable from the island shores or the nearby
waters. The resolution of those two hypotheses poses an interesting challenge tomarine mammalogists and archaeologists.
CURRENT OBSERVATIONS: FIELD METHODSWe began the study at the end of February 1976, while the migratory season
was in progress, and concentrated our efforts principally in the regions of suspected
highest whale density, the waters within the four-island region and on Penguin
Bank (Fig. 1). Other areas were also surveyed, but in less detail. Table 1 summarizes dates, times, and whale spotting conditions for the various aerial and ship
surveys. Aircraft surveys used a high-winged Cessna 172, flying at 152-m (500 ft.)altitude at air speeds of approximately 100-120 knots. During an aerial survey, apredetermined transect over an area of interest was flown untill sighting of a whaleor pod of whales. The aircraft then diverted from its path and orbited the pod at
152-m altitude for close-range visual observation and photography. We used
TABLE !.

AERIAL AND SHIPBOARD SURVEYS OF HUMPBACK WHALE
POPULATION IN HAWAII (1976)

Date

Time

Region

Method a>

29 Feb.
29 Feb.
I Mar.
I Mar.
13 Mar.
14 Mar.
14 Mar.
14 Mar.
15 Mar.
16 Mar.
19 Mar.
19 Mar.
9 Apr.
9 Apr.
9 Apr.
15 Apr.

1130-1454
1617-18330926-1222
1456-1737
0840-1801
0910-1810
1110-1420
1600-1735
0800-1640

Hnl to W. Maui
W. Maui to Hnl
Hnl to W. Maui
W. Maui to Hnl
Hnl to Molokai
Kalohi Channel
Hnl, Lanai, to W. Maui
W. Maui to Hnl
Kalohi Channel
Molokai to Hnl
S. coast Oahu to W. Kauai
Circle Kauai, Niihau, Oahu
Hnl to W. Maui
N. & E. Maui, circle Hawaii
N. Hawaii to E. Maui
Circle Oahu

A
A
A
A

0730~1615

1000-1056
1231-1627
0853-1137
1333-1651
1745-1840
1353-1517

s
s
A
A

s
s
A
A
A
A
A
A

Spotting
Conditionsb>
E
E (F after 1745)
G
G
E
E
E
G to FG
G (P after I OOO)E
G to FFFF
E to Ga> A =aircraft. S =ship
bl E =Excellent; weather fair and seas calm to slight; no whitecapping (Beaufort Scale No. 0-2).
G =Good; weather fair or cloudy and seas moderate with minor whitecapping (Beaufort Scale No. 3).
F =Fair; weather fair or cloudy and seas moderate with more frequent whitecapping (Beaufort
Scale No. 4); or reduced visibility due to poor light but sea state 3 or less.
P =Poor; reduced visibility and sea state 4 or more; or greatly reduced visibility in any sea state;or sea state 6 or greater.

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

66

HERMAN AND ANTINOJA

Nikon F2 and Canon FTB cameras equipped with 105, 200, and 300 mm lenses.
Visual observations were recorded in real-time on audio cassettes. The positionof the aircraft over whales was obtained by reference to land-based VORTAC radio
stations, if in range, or to landmarks using USCG navigational charts. The swimming direction of the whales was determined through use of the aircraft's onboard
compass. Three personnel in addition to the pilot accompanied each flight.
Shipboard surveys between Oahu and Molokai were made on March 13th and16th. The boat followed approximately the same path as the aircraft within asurveyed region, but did not divert from its path following a spotting. Three observers were positioned along the port side, and another three along the starboard
side. Whales observed beyond the stern of the boat were not counted unlessobviously not a previously-seen spot. The swimming direction of the whales wasestimated by handheld compass and their distance from the boat gauged by visual
estimation. The position of the boat was determined by reference to visibly charted
landmarks or by dead-reckoning using time and distance data.
The ship remained in the Kalohi Channel area between Molokai and Lanai
on March 14th and 15th for close-range observation of the whales and for launchingof underwater observations. Divers equipped with Nikonos II 35-mm underwater
cameras dropped off the stern of the moving ship at positions which hopefully wouldintercept the path of whales observed swimming astern. Scuba gear was not usedbecause it was felt that bubble emissions might prove aversive to the whales. A
surfboard was thrown into the water for the diver's use immediately after his departure, while the ship continued on its path. The diver was recovered by theship after completing observations or on failing to contact the whales. Divers madetape recorded notes of their visual observations immediately after returning to thevessel.
The aerial, shipboard, and underwater photographs obtained, in conjunction
with notes on visual observations, were used to refine the numerical counts of pod
size, to describe pod composition and organization, to identify morphometric characteristics of individual animals and to categorize behaviors.
RESULTS AND DISCUSSION

Population Parameters
Distribution and Concentrations:

Four Island Region.

Figures 2-4 show representative data, giving the locations of pods and numbers of whales per pod during
aerial surveys between Honolulu and W. Maui on February 29th and March 14thand during a ship survey between Honolulu and Molokai on March l 3th. Each
pod is numbered serially, in the order seen, and the movement characteristics of thepod, if obtainable, are shown. Calves are noted as cross symbols. The remaining
animals were almost always classified as adults, though a few of seemingly juvenile
status were also seen, but are not identified separately in this report. Table 2 summarizes pod and whale counts for all surveys within the four-island region. Figures
2-4 show that whales were principally found within the 100-fathom contour. AirSci. Rep. Whales Res. Inst.,
No. 29, 1977.

HUMPBACK WHALES OF HAWAII67

TABLE 2. FOUR-ISLAND REGION: NUMBERS OF PODS, WHALES PLUS CALVES,AND CALVES OBSERVED DURING AIRCRAFT AND SHIP SURVEYS

AircraftFeb. 29
Mar.
Mar. 14
Apr.

9

Ship
Mar.
Mar.
Mar.
Mar.

13
14
15
16

RegionPods

All Whales

CalvesWhales/Pod

Hnl-Maui
Maui-Rn!
Hnl-Maui
Maui-Rn!
Hnl-Maui
Maui-Hnl
Hnl-Maui
Totals:

22
20
23
22
22
15
6
130

43
52
56
54
55
27
15
302

4
5
0
4
5
3
22

1.96
2.60
2.43
2.45
2.50
1.80
2.50
2.32

Hnl-Mlk
Kalohi Ch.
Kalohi Ch.
Mlk-Hnl
Totals:

38
10
18
16
84

48
31
30
18
127

0
3
3
0
6

1.25
3.10
1.67
1.13
1.51

22·~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

N

30'

21·

AERIAL SURVEY
30'

Honolulu to Maui
February 29, 1976
1130-1454 hours
158°W

30'

157°

30'

156°

Fig. 2. Aerial survey results, showing path of aircraft (solid line), pod numbers in
the order seen, and the number of whales per pod. Adults are shown as open
circles and calves as cross symbols, Straight arrows show movement direction ofswimming pods; arrows with a cross-hatch indicate a re5ting pod oriented in the
direction shown; curved arrows. indicate milling pods. Not all pods were classifiable because of observation difficulty. The 100-fathom contour is shown as adashed line.
Sci, Rep. Whales Res. Inst.,
No. 29, 1977.

68

HERMAN AND ANTINOJA
22·~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

N

30'

21'

30'

AERIAL SURVEY
Honolulu to Maui
March 14,1976
1110-1420 hours
158' w

Fig. 3.

KAHOOLAWE
30'

157'

30'

156'

Aerial survey results keyed as in Figure 2.

30'

21'

30'

SHIP SURVEY
Honolulu to Molokai
March 13,1976
0840-1801 hours
158' w

30'

157'

30'

156'

Fig. 4. Ship survey results keyed as in Figure 2. The Kalohi Channel area is expanded in the upper right of the chart to show details of the pods.

craft data gave the relatively greatest numbers of whales, on the average, in Kalohi
Channel (13. 7 whales/flight). This was followed by Penguin Bank (11. 7 whales/
flight), the Auau channel area southeast of Kalohi Channel (9.6 whales/flight) andthe south coast of Molokai from Laau Point to Kaunakakai (6.3 whales/flight).
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

HUMPBACK WHALES OF HAWAII

69

Other regions yielded much smaller numbers. The relative numbers of whales
seen in the various regions remained reasonably consistent across successive flights,
although some anomalies were evident. On the flight of February 29th from Mauito Honolulu, especially heavy concentrations were seen along the south coast of
Molokai, and on April 9th no whales at all were seen in Kalohi Channel. Thoughspotting conditions were only fair on April 9th (Table 1), possibly accounting forsome reduction in the counts, as on the return flight of March l 4th from Maui to
Honolulu, it is more likely that by this date many whales had already left on theirreturn migration to the summer feeding grounds. Kalohi Channel, especially thesouth and southeast portions, seems to be an important breeding area and as these
activities diminish over the season it would be one of the earliest areas expected toshow a population decline. With respect to the south coast of Molokai, ten of thetwenty-two whales seen on February 29th were actually located near the beginning of Penguin Bank. Though moving towards southwest Molokai, a survey
perhaps an hour earlier might have placed them within the usually more densely
populated Penguin Bank.
The ship survey of March 13th verified the aircraft data showing 'large concentrations of whales in Penguin Bank and Kalohi Channel. The fewer numbersof whales per pod, as compared with aircraft data reflects the difficulty in estimating the numbers of whales without approaching pods closely. On March 13th
(and on March 16), with but one exception, the ship did not divert from the planned transect to inspect pods. In contrast, on March l 4th in Kalohi Channel, theship frequently diverted from its transect for the close-range inspection of pods,
yielding an elevated count of 3.1 whales per pod (as compared with the overall
estimate of 2. 7 whales per pod from aircraft data in Kalohi Channel). It is significant that calves were seen from the ship only during close-range inspection. On
March 15th, less time was spent on close-range inspection from the ship than on the
14th and more on general survey, resulting in an elevated pod count, but less whales
per pod. Three of the pods approached on the 15th had calves, as was thecase on the 14th. In general, it seems that pods with calves are easier to approachthan those without, in part because the latter are capable of more rapid locomotion and prolonged diving.
On March 16th, during the ship survey, large swells and considerable whitecapping were encountered in the Penguin Bank region. Nevertheless, the pod
count in that area (9 pods) was not much reduced over that found on March 13th
(13 pods) under better weather conditions. Spotting of the pods on March 16th
was almost entirely through seeing the large splash resulting from the breachingof an animal, whereas on the 13th blows and the animals themselves could be
spotted in the absence of breaching. It may be, as has been suggested by others,
that breaching is more common in rough water, perhaps serving to maintain acoustic
and/or visual contact between whales.
Distributions and Concentrations: Other Regions and Islands. We cannot draw
strong conclusions about concentrations of whales in the areas outside of the fourisland complex or Penguin Bank, since the outlying areas were surveyed less freSci. Rep. Whales Res. Inst.,
No. 29, 1977.

HERMAN AND ANTINOJA

70

quently and sometimes beyond the peak of the migratory period. Nevertheless, it
seems apparent from the available data that outlying concentrations in no way approached those observed within the four-island region and Penguin Bank. Table
3 shows that on March 19th, presumably still at or near the peak period of concentration of whales in the four-island complex and Penguin Bank, a total of only
ten whales (four pods) was seen around the entire island of Oahu, along the northand northeast coasts; six whales (three pods) around the entire island of Kauai,
between Nawiliwili Bay and Makaha Point; and no whales at all around the islandof Niihau or nearby Kaula Rock. The island of Hawaii was not surveyed until
April 9th, and judging from our results on that same date in the four-island region(Table 2), this was already past the peak migratory period. The two pods ofwhales seen near Hawaii on April 9th were at or just south of Upolu Point. The
pod of six whales seen in Alenuihaha Channel was approximately 8-10 nm NWof Upolu Point heading north-northeasterly. It was one of the few pods foundconsiderably outside of the 100-fathom contour and possibly was on the beginningof a return migration to higher latitudes.
TABLE 3. OUTLYING REGIONS: NUMBERS OF PODS (P), WHALES PLUS
CALVES (W), AND CALVES (C) OBSERVED DURING AIRCRAFT SURVEYS
Mar. 19

Oahu
Kauai Ch.a>
Kauai
NiihauKaula RockE. Maui
Alenuihaha Ch.bl
Hawaii

Apr. 9

p

w

c

4

10
0
6
0
0

0
0
0
0
0

0
3
0
0

p

w

Apr. 15

c

p

c

w
3

2

1
6
4

0
0
0

al Survey path was a straight line between Kaena Pt. Oahu and Nawiliwili Bay, Kauai.
bl Survey path was a straight line between Kipahulu Gulch, Maui and Upolu Pt., Hawaii.

The survey around the island of Oahu on April lSth revealed only a single
pod of three whales, including a calf. No further surveys were conducted afterthat date, though as late as mid-May the authors observed several pods from peaks
overlooking the south coast of Oahu. Also, reports were received of a few whales
lingering around the island of Oahu in June.
The last departures on the northward migration seemingly would tend to bepods with calves, judging by the relatively high proportion of such pods (three ofsix) seen on April 9th and lSth. The delayed departure of calves would allow
for attainment of sufficient growth and blubber deposit before encountering the
rigors of migration and the colder waters of the higher latitudes, and typifies migratory characteristics of Southern Hemisphere populations of humpback whales(Dawbin, 1966).
Our data showing that concentrations of whales outside of the four-island reSci. Rep. Whales Res. Inst.,

No. 29, 1977.

HUMPBACK WHALES OF HAWAII

71

gion and Penguin Bank are relatively small are consistent with sighting reports
from commercial hydrofoil craft during the 1976 season (Shallenberger, 1976).
Population Estimates. The combined data from the ship and aircraft surveys
can be used to estimate population numbers in selected areas. Gulland (1972)
suggested that counting all whales for two miles on each side of a ship's paththrough an area yields accurate estimates of whale density (whales/nm 2 ) in thefour-mile wide strip covered, which may then be extrapolated to the entire regionof interest. Gulland's model assumes that nearly all whales in the strip will beseen. Our data suggest, however, that it is simpler to estimate pod density (pod/nm 2 ) than whale density by ship survey. Our ship, transecting an area at ten
knots, probably missed very few of the pods actually present within the 4-nm widesighting strip. But, our aircraft surveys over the same region revealed that the
number of whales per pod was underestimated, unless the ship approached thepods closely. Aircraft, from their favorable vantage point, count whales per pod
with great accuracy, but unless surveying a region in fine detail, miss some proportion of the pods actually present. It would seem, then, that nearly all whales
present in a region could be accounted for by using ship data to estimate pod
density in the region, and aircraft data to estimate mean whales per pod. Multiplying the two estimates should yield highly accurate population counts. This
simple model was used to estimate the number of whales present in the three main
regions surveyed by ship on March 13th. The results were 63 whales for Penguin
Bank (.22 whales/nm2 ), 9 for the south coast of west Molokai within the 100-fathom
contour (.2 whales/nm2 ), and 47 for Kalohi Channel (.57 whales/nm 2 ), for a totalof 119 whales. To this we can add seven more in the small region just north of
the NW tip of Penguin Bank, where the ship encountered three pods, and aircraft
data yielded an average of 2.5 whales per pod. Other than this small region, thenumber of whales in the area between Honolulu and Penguin Bank appears negligible. The estimates given suggest that aircraft surveys sampled from one-third
to two-thirds of the population present. The larger sample size was obtained when
the region was well covered by the aircraft, such as the restricted coast-line areas of
Molokai.
The remaining major concentration of whales present on March 13th in thefour-island region would have been in the Auau Channel region east of Kalohi
Channel between Maui, Lanai, and Kahoolawe, and within the I 00-fathom contour. This region was not surveyed by ship. If we assume the whale distribution
on March l 4th was not significantly different from that on the l 3th, we can use
the aircraft flights of the 14th to add to our population estimates. Five pods werespotted by the aircraft in the Auau Channel region on March l 4th, but all dove
before they could be approached closely. We can, however, use the mean valueof 2.0 whales per pod, based on all aircraft flights over that region, to estimate thenumber of whales in those pods as ten. Applying the sampling ratio for aircraft,
previously discussed, of from one-third to two-thirds of the population, gives a final
estimate of from 15 to 30 whales actually present in Auau Channel. The assumptions made in these calculations should be treated with caution but appear reasonSci. Rep. Whales Res. Inst.,
No. 29, 1977.

72

HERMAN AND ANTINOJA

able in view of our overall data.
In summary, the overall estimate of population size on March 13th in thefour-island region, and including Penguin Bank and the area immediately adjacent to its NW tip is thus 141-156 whales (119+ 7+15 to 30). There were undoubtedly whales in other regions, but likely in considerably smaller numbers thanin the four-island region and Penguin Bank. On March l 4th, for example, only
six whales were seen along the northeast coast of Molokai and the south and west
coasts of Lanai, and on March 19th, only 16 whales were found around all of
Oahu, Kauai, Niihau and Kaula Rock (Table 3). East Maui and the island of
Hawaii, surveyed on April 9th, yielded only 11 whales (Table 3). Concentrationsin these latter two regions were likely greater three weeks earlier, and our uncertainty in estimates for the period near March 13th is, accordingly, greatest for theseregions. For the present, it seems best to bracket our estimates for all combined
outlying regions and islands as perhaps 50 animals as a lower bound and 100 as an
upper bound. The total population on or about March 13th might then havenumbered from close to 200 animals to as many as 250 animals. The March 13th
period was apparently within the peak of the migratory cycle, judging by our aircraft data (Table 2). However, we do not know how long individual whales
remain in the islands, and it is possible that some animals might have already departed the Hawaiian waters and that others were still in-migrating, which would
add to our population counts somewhat. It would be desirable to extend thecensus work in the future, so that all major areas within the islands could be surveyed in parallel on given dates, and in- and out-migration studied in detail.
Nursery Grounds and Numbers of Calves. Tables 2 and 3 gave data for the number of calves seen during each aerial survey. Calves were typically accompanied
by more than one adult, as discussed more fully in a later section, but in no casewas there more than one calf in a pod. With the one exception of a pod of two
adults and calf observed off north Oahu on April 15th, all pods with calves were
found within the four""island region and on Penguin Bank. For all flights combined, the areas of greatest concentration were Kalohi Channel (9 calves), especially along the north coast of Lanai, and Penguin Bank (8 calves). Additionally,
two calves were seen south and southwesterly of Lahaina, Maui. No other area
yielded more than a single calf. Though the north coast of Lanai is clearly themost densely concentrated nursery region and should be protected, there is considerable dispersion of nursery areas throughout the regions surveyed.
The numbers of calves seen relative to total whales provides a basis for estimating gross recruitment rate (Seber, 1973). As a first approximation we can assume that the Hawaiian population is similar demographically to populations of
humpback whales elsewhere having characteristics known through whaling operations. Normal sexual maturity for humpback whales, as for some other baleen
whales, occurs from 6-12 years (Anon, 1975) for both males and females. Earlier
average onset may be recorded in highly exploited stocks due to the more rapid
growth rates in such cases, or the selective depletion of larger (older) animals(Chittleborough, 1965). Mackintosh (1972) states that given the two-year reSci. Rep. Whales Res. Inst.,
No. 29, 1977.

HUMPBACK WHALES OF HAWAII

73

productive cycle of female baleen whales, and that 99% of the births are single
calves with the sex ratio approximately equal, the expected birth rate would be 50%of the sexually mature female population. Rice (1963) calculated a pregnancy
rate of 43% based on examination of 168 humpback whales caught by shore stations near San Francisco. The number of females was not specified. Nishiwaki's(1959) data on humpback whales caught in Ryukyuan waters in the western North
Pacific gives the annual percentage of ovulating females as 60% and pregnancy
rates as 40%. Chittleborough (1965), using catch-effort statistics from the whaling station of Albany in southwest Australia, estimated that 37% of the female
humpback whales were pregnant. Of a small sample of 13 female humpback
whales collected in the northwest Atlantic in 1969 and 1970, 7 (54%) were pregnant (Mitchell, 1974). The collective data from these sources suggest that thenormal birth rate could be somewhat lower than 50% of the mature females; 43%
may be a reasonable best estimate.
According to Nishiwaki (1959) approximately half of a normal humpback
whale population are sexually mature animals, with half of these males and half
females. This places the normal limit on calf recruitment rate as .5x .5X .43=
.108 or 10.8% of the entire population. Applying this recruitment rate to the
Hawaii population, conservatively estimated as 200 animals, would yield an expected calf population of 22.
Across all of our aerial surveys, there were some obvious vagaries in our calf
counts (Table 2). Low counts can generally be attributed to unfavorable spotting conditions or to the abbreviated nature of a survey, though in the ca~e of themorning flight of March lst, the reasons for the zero count were unclear. The
largest number of calves seen on any flight was five, on the second flight of February 29th and then again on the first flight of March 14th. In each case, spotting conditions were excellent for all or nearly all of the survey. The most optimistic estimates of recruitment rates are obtained by considering the calf to adultratios on these two flights. (Calf to adult ratios obtained after the peak migratory
period, such as that of April 9th, are biased because mothers with calves remain
longest in the breeding grounds, cf. Dawbin, 1966). On the second flight of February 29th, 9.6% of the total of 52 whales seen were calves, and on the first flightof March l 4th 9 .1 % of the 55 whales were calves. These percentages can be considered the upper limits of the current calf recruitment rate for the Hawaiian population, but both are somewhat below the discussed expected rate of 10.8%. More
importantly, since the four-island region and Penguin Bank appear to contain the
major nursery grounds, birth rate samples from these areas may not be representaative of other areas, and would overestimate rates for the population at large.
Hence, the rates of 9.1 % and 9.6% should be regarded as optimistic.
The apparent low birth rate is disturbing and calls for additional assessment.
The reasons for the apparent low rate are unclear. In a small unexploited population, presumably below the carrying capacity of the environment, one would, infact, expect higher than normal rates of birth (Wilson, 1975). It seems doubtfulthat our sampling of the calves was disproportionately low, since pods with calves
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

74

HERMAN AND ANTINOJA

are typically slow moving or even resting, seldom diving deep or for long periods,
and hence are relatively easy to spot from aircraft. It may be that a demographic
analysis of the Hawaiian population would show, for reasons unknown, a smaller
than usual number of mature whales, explaining the low recruitment rate. Or, it
may be that the low rate reflects unfavorable biological or ecological conditions, ora response to continued harassment from the ships, aircraft, and divers passing
close to the whales, intentionally or otherwise. Whatever the cause, the apparent
low recruitment rate underscores the potential fragility of the population and thepressing need for its careful protection and management.

Pod Characteristics
Pod Si,ze. Table 4 summarizes the findings on sizes of pods for all aerial surveys combined. There is generally an orderly decrease in the frequency of occurence of successivCly larger pod sizes, though the majority (59%) of the pods
were comprised of two or more animals. The largest pod size, nine, was observedon February 29th in Kalohi Channel and on March lst near Laau Point, Molokai.
The percentage of singletons is very probably an overestimate, since we conservatively estimated one whale for all spots for which a single blow, breach, or bodypart was seen at a distance but the animal could not be relocated on closer approach. There were 23 such cases out of the total of 59 singletons.
TABLE 4.

SIZE COMPOSITION OF PODS FOR ALL AERIAL SURVEYS
Pod Size2
No. of Pods
% Total
Note:

59
41.5

37
26.1

3
18
12.7

4
11
7.8

5
8
5.6

6
6
4.2

7
1
0.7

8
0
0.0

9
2
1.4

Totals142
100.0

Pod size includes both adults and calves.

The data of Table 4 may be contrasted with that of Nemoto (1964) who reported on pod sizes for the humpback whales in their summer feeding grounds inthe upper North Pacific. Of 92 pods encountered by Nemoto, 50% were singletons, 43% pairs, 3% threesomes, 2% foursomes, and 1% fivesomes. There wasalso a single group of seven (1 %). The largest difference between our data andthat of Nemoto occurs for groups of three or more: 32% of our groups were threeor more animals but only 7% of Nemoto's. Dispersal in the feeding ground andclustering in the breeding ground appear obviously adaptive. Grouping in baleen
whales may stimulate and facilitate reproductive activities as it does for other species (Wilson, 1975) and is consistent with the presumed promiscuous mating behaviors of female baleen whales in which multiple males appear to attend a single
female (e.g., see Payne, 1976). Apparent polyandrous mating bouts were observed in a number of our aerial surveys, but we cannot be sure of the sex of theparticipants. The counts by Winn et al. (1975) of the humpback whales in
the West Indies breeding grounds seem discrepant in that only 23% of their sightings were groups of two or more as compared with 49% for Nemoto and 59% forSci. Rep. Whales Res. Inst.,
No. 29, 1977.

HUMPBACK WHALES OF HAWAII

75

our data. The Winn et al. counts were based on shipboard transects whichapparently did not approach the whales closely. Their data may thus underestimate whales per pod, as did similar ship surveys we conducted on March 13thand 16th. The data of Nemoto (1964), though based on shipboard observation,
relied on catch statistics in which boats necessarily pursued and approached whales
very closely, allowing for highly accurate counts of pod size.
Pods With Calves. Table 5 shows that calves are typically found in pods withmultiple adults, most often two adults, the mother and an " escort " whale. This
is in contrast to other Balaenopterid whales in which the mother and calf often
travel unescorted (Nemoto, 1964). The Southern Hemisphere mother-calf humpback whale pairs, like the Hawaiian group, do tend to school with other whales.
TABLE 5.
FlightFeb. 29 (1)Feb. 29 (2)Mar. 1 (1)Mar. 1 (2)Mar. 14 (1)Mar. 14 (2)Mar. 19
Apr. 9Apr. 15
TotalsNUMBER OF PODS WITH CALF(C) AND THE NUMBER
OF ACCOMPANYING ADULTS (A)
lA-lC

2A-1C

3A-1C

2
5

2

4A-1C

5A-1C

4
5
0

4

3
2

4

Totals

11

2

4

2

5

2

0
3
1
23

Chittleborough (1953) reported that all nine mother-calf humpback whale pairs
seen in Antarctic waters were accompanied by other whales. Four of the nine
were accompanied by a single additional whale. In some contrast only two of ninemother-calf humpback whale pairs seen in North Pacific waters by Nemoto (1964)
were accompanied by other whales. It may be that schooling with other whales
occurs principally in the terminal breeding and feeding areas rather than enroute.
Thus, Chittleborough (1953), observing migrating Southern Hemisphere humpback whales near the western Australia coast, reported that the calf was usually accompanied only by the mother. Also, in Exmouth Gulf, on the Australian west
coast, all seventeen calves seen by Chittleborough were accompanied only by themother. Exmouth Gulf does not seem to be a terminal point, since migrations
north and south of the Gulf were observed. Since mother-calf pairs do departthe breeding grounds last, there are few other whales for them to school with on
the return migration, except for other cow-calf pairs. But, as noted for the
Hawaiian population, multiple calves in a pod were never seen, and may indicate
a self-imposed segregation of mothers from calves which are not their own.
The escort whale or whales may serve a protective function, as discussed in alater section. Here we may note that Southern Hemisphere humpback whale trios·with calf have been observed defending themselves against killer whales. In one
Sci. Rep. Whales Res. Inst.,

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HERMAN AND ANTINOJA

case cited by Chittleborough (1953), one adult of the two present kept the calf very
close while the second charged the pack of 4-5 killer whales, successfully beatingthem off with its flukes.
Gross Activiry ef Pods. The gross activity of a pod was classified as swimming,
milling, or resting (Table 6). Swimming behavior was defined as movement in a
fixed direction during the aircraft's approach. Milling was defined as spatially
undirected activity occurring within a small area. Milling animals might be lolling about, rolling on their backs, or contacting one another in the case of multiple
animal pods. For singletons, the animal was classified as milling using a similar
criterion of area-restricted activity, though contactual behavior was of course
absent. Resting animals were lying quietly in the water, dorsal surface up, barely
moving at best, usually stationary. Gross activity data was available for 97(68.3%) of the total of 142 pods seen on all flights. The remaining pods either
dove when closely approached and before they could be classified or else we could
not locate the animal on close approach.
TABLE 6.

GROSS ACTIVITIES OF PODS CLASSIFIED BY TYPE AND SIZE

Activity/Size

Singleton

Swimming
Milling
Resting(Subtotal)
No Data(Total)20(83.3)
4(16.7)0 ( 0. 0)24
35
59

Pods with Calfal

Multiple-Adult Pods
2

3

4

s+

19
3
2
24
9
33

5
0
1
6

4
4

10 38(76.0)
1 8(16.0)0
4 ( 8. 0)
11 50
0 JO
II 60

I

7

I

9
0
9

All

Totals

2

3

4

s+

1 6
0
2
3
3
4 11
0
0
4 II

2
0
0
2
0
2

2
2
0
4
0
4

2 13(56.5)
0 4(17.4)
0 6(26.1)
2 23
0 0
2 23

All

71 (73.2)
16(16.5)
10(10.3)
97
45
142

Note: Percentages, given in parentheses, are based on subtotals.
al pod size refers to number of adults accompanying calf.

It is clear from Table 6 that for multiple-adult pods, and for single adults aswell, active swimming was the most common gross activity, with milling considerably less common but still more frequent than resting. It is the milling multipleadult pods that are engaging in mating behaviors. There are no obvious relations
between pod size and pod activity.
For pods with calves, swimming was relatively less frequent though still themost common behavior, while resting was more common than milling. It is probable that the young calf tires easily and tends to require that the mother be stationary while nursing. Whalers in the past have taken advantage of the lesser
stamina of the calf to catch and kill the mother who remains nearby the tiririg calf
throughout the pursuit.
The breakdown of activity by size of pod having calves reveals a tendency forswimming and milling activities to be associated with larger-sized pods, while resting seems common when the calf is accompanied only by the mother. The database is very small so these trends must be interpreted with caution. If they are
indicative of the population at large, it may be that calves accompanied only by
Sci. Rep. Whales Res. Inst.,
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HUMPBACK WHALES OF HAWAII

the mother are quite young, and that as they mature the pair either joins otherwhales, who tend to be active, or else are attractive to other whales who join them.
Spatial Organization of Pods. The spatial formation of swimming pods, whenobservable, was classified into eight different categories as described in Table 7:line astern (file); diagonal; line abreast (rank); wedge-shaped with animals spreadout symmetrically behind a leading animal or animals (simplified echelon); veeshaped with multiple leading animals abreast and one or more additional animals
centered and behind; T-shaped; diamond shaped; and x-shaped. In many cases,
the formation was clean-cut, as in the case of a pod of five whales observed line
astern, each animal nearly touching the flukes of the one ahead, or the neatly staggered diagonal array of a pod of four whales observed on another occasion. Moreoften, the formation was broken by one or two animals, so that three might betightly astern while a fourth swam off to one side. In such cases, the formationof the majority of the animals was used to categorize the pod's organization.
Only formations actually seen are listed. There are obviously other possibilities.
TABLE 7.

SPATIAL ORGANIZATION OF SWIMMING PODS GROUPED BY POD SIZE

Formation/Pod Size
AsternDiagonal
Abreast
Wedge
Vee
Tee
Diamond

All-Adult Pods

Totals
2

3

4

5+

All

2

3

4

5+

All

2
2
5

1
0
0
0
2

5
2
0
2
0
0
0

2

2
3

1
0
0
1
0

0
0
0
0
0
0
0

0

0
0
0
1
0

9
9
18

3
3
6

9
0
9

5
0
5

10(38.5)
5(19.2)5(19.2)2 (7. 7)2 (7. 7)
1 (3.8)0 (0.0)1 (3.8)
26
12
38

2
0
2

0
0
0

0
3

3 (27 .3)
4(36.4)2(18.2)
1(18.2)0 (0. 0)0 (0.0)1 (2. 7)0 (0.0)
11

4

12

x
(Subtotal)
No information(Total)Pods With Calvesal

6
0
6

1
0
0
0

13(35.1)
9(24.3)7(18.9)4(10.8)2 (5 .4)(2. 7)(2. 7)(2. 7)
37
13
50

Dashes in columns mean that spatial organization of the type specified is not possible for the
given number of animals. Numbers in parentheses are percentages of subtotals.
a) Organization based on adults in pods only.
One swimming pod of the total of 13 in Table 6 wasa single adult with calf and hence is not classified here.

Note:

Among the all-adult pods, the line abreast formation was observed only forpaired animals, swimming side by side. For larger pods, the adults arranged
themselves most commonly in the line astern formation or what may be simply its
variant, the diagonal. The function of these "follow-the-leader" formations is
not apparent, nor is it clear whether specific animals maintain leadership positionsin the swimming pod. More protracted observations are necessary to answer thesequestions.
For pods with calf, only the spatial organization of the adults was classified,since the calf typically remained close to a given adult, presumably the mother.
The number of swimming pods having calves was small, so generalizations are difSci. Rep. Whales Res. Inst.,
No. 29, 1977.

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HERMAN AND ANTINOJA

ficult. In pods with a single escort whale, the escort tended to remain behind themother-calf pair. If multiple escorts were present, one or more might remain aheadof the mother-calf pair while the others remained behind or abreast. Invariably,
we noted that when a pod with calf shifted its formation in response to the orbiting
aircraft, it was to tighten the formation and move the calf to a more central position between the adults, a clearly protective behavior. In contrast, for all-adultpods, shifts of formation occurring in response to overhead aircraft were predominantly dispersals of the pod, the animals moving further apart or temporarily
going in different directions. Another defensive response of a pod to the aircraft
was deep diving (sounding). This tended to occur more commonly for singletonsand for pods of two but rarely for larger groups.
Underwater observations of milling or stationary pods revealed that verticaldispersion was often greater than horizontal dispersion. In pods with calf, theescort would typically appear from well beneath the near-surface mother-calf pair,
presumbably in response to the presence of the diver. The pod would then departfrom the area of the diver.

Coloration: A Clue to Population Identification
Most humpback whales are predominantly black on their dorsal surface, excluding the pectoral fins and tail flukes which may have extensive white coloration.
White coloration is common on the ventral surface of the pectoral fins, flukes, andportions of the body from the throat region to the navel. In earlier whaling days
when humpback carcasses could be examined, investigators studying coloration
focused on the description of ventral surfaces as these seemed to show the mostvariability. Lillie (1915), working with carcasses of Southern Hemisphere humpback whales, devised a seven category classification scheme for ventral surface coloration, ranging from extensive white to all or nearly-all black. Later invesigators
generally continued to use Lillie's categories (Chittleborough, 1965; Matthews,
1937; Omura, 1953; Nishiwaki, 1959; Symons and Weston, 1958). The major interest was in whether coloration differences could predict demographic characteristics of the population, in particular sex and body length (age). No stable, clearcut relationships were found within or across studies, but a by-product of the research was the observation that geographically isolated groups often demonstrated
different coloration characteristics. In the Southern Hemisphere, Matthews(1937) found that humpbacks from the South Georgia and South Africa regions
were on the average darker in color (84.8% of 53 animals fell in the darkest twoof Lillie's categories and 1.8% in the lightest two) than humpbacks from the New
Zealand area (26% of 30 animals were in the darkest two categories and 26. 7%in the lightest two). Symons and Weston (1958) reported that 24.1 % of 58 animals captured in the Bellinghausen Sea adjoining Antarctica fell in the darkest twocolor categories while 36.2% were in the lightest two. Omura (1953) provides
an excellent summary of differences among all five Antarctic groups and Chittleborough (1965) gives additional data on coloration differences between east andwest coast Australian populations.
Sci. Rep. Whales Res. Inst.,
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HUMPBACK WHALES OF HAWAII79

In the North Pacific, Pike's (1953) data for 184 British Columbia humpback
whales reveal that all fell into the darkest two coloration categories. Nishiwaki(1959), examining 237 western North Pacific whales captured in Ryukyuan waters,
classified 92.2% as being black or mostly black and none as being predominantly
white. These results were very similar to another 164 animals subsequently captured in the same waters (Nishiwaki, 1962), leading Nishiwaki (1965) to conclude
that North Pacific humpback whales are darker in coloration, having only a few
small white areas, than Southern Hemisphere humpback whales, which often havelarge white areas.
Our coloration data for the Hawaiian population, based principally on aerial
observations, must rely on coloration of dorsal, not ventral surfaces. We havefound considerable variation in dorsal surface coloration of the pectoral fins. Past
literature on humpback whale coloration has in a few cases reported dorsal surface coloration of the pectoral fins. These data suggest considerable color variation in the dorsal surfaces of the pectoral fins between geographically isolated breeding groups.
In Table 8 dorsal surface coloration of the pectoral fins for the Hawaii population is classified into four categories: all black; slight white (leading or trailing
TABLE 8.

COLORATION OF DORSAL SURFACE OF PECTORAL FINS:COMBINED AERIAL TRANSECTS
Mother

Adult a>

Calf

Total

ColorationN
All Black
Slight White
Moderate White
Extensive White
Subtotal
Undetermined
Grand Total
al

7
3
3
8
21
2
23

%
33.3
14.3
14.3
38.1
100.0

N
6
3
3
7
19
4
23

%
31.6
15.8
15.8
36.8
100.0

N

%

N

%

53
27
14
55
149
137
286

35.6
18.1
9.4
36.9
100.0

66
33
20
70
189
143
332

34.9
17.5
10.6
37.0
100.0

Includes six animals classified as juveniles, two with all black coloration, one with slight whitecoloration and three undetermined.

edges white, or a few small spots of white seen elsewhere on the surface); moderate
white (mottled, piebald, speckled, or patchy areas of white); and extensive white(solid white or mostly white). Classification was based on detailed examinationof aerial photographs and on supplemental notes made while circling a pod. Coloration data were available for 189 of the total of 332 whales spotted during thevarious aerial transects. Many of these whales were undoubtedly the same animal seen on different occasions, but assuming that whales are sampled on a random basis (with replacement in the population) the percentages should estimate
population parameters closely. Table 8 shqws that 37% of the whales were classified in the extensive white category and 35% in the all black category. The
data reveal very close correspondence in percentages for mothers, calves, and adults, suggesting that phenotypical color characteristics are stable in the population.
Sci. Rep. Whales Res. Inst.,
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80

HERMAN AND ANTINOJA

These characteristics could prove useful in identification of the Hawaiian population in its summer feeding grounds, if dispersal and intermingling of populations is
minimal.
From the limited data available on Southern Hemisphere stocks, it appears
that white coloration on the dorsal surface of the pectoral fins was rare. Lillie(1915) made no mention of all-white pectoral fins; neither did Omura (1953) orSymons and Weston (1958). Matthews (1937) stated that of the groups in thedarkest two categories, 7% had white pectoral fins. Unfortunately, data for othercoloration categories was not given. In the eastern North Pacific, Pike (1953) reported that only 14. 7% of the British Columbia whales had predominantly whitecoloration on the dorsal surface of the pectorals. This is considerably below the
37.0% value we find for the Hawaiian group. Scammon (1874) described theeastern North Pacific population as all black above, or nearly so. Very recent observations of humpback whales in the southeast Alaska region describe them as
having all black pectoral fins above and as numbering 60-61 animals (M. Tillman,personal communication). From these combined data, we can infer that the
Hawaiian population is reproductively isolated from the eastern North Pacific stockand that it does not summer in the feeding grounds of that region.
Tomilin (1957) provided only qualitative data on coloration of the western
North Pacific stock, presumably in the area of the Kamchatka Peninsula. He described the dorsal surface of the pectorals as ranging from black to piebald or evencompletely white. He also described a group from the Chukchi Sea and the Bering Sea as having dusky flippers with an exceptionally white border. This was
not a characteristic observed in the Hawaiian group, suggesting reproductive isolation of the Hawaiian group from at least portions of the Asiatic population. It isdifficult to say whether significant intermingling of the populations occurs in common feeding grounds in the Aleutian Island regions or further to the west andnorth.
Chittleborough (1953), using aerial surveys to study the New Zealand humpback whale population, reported that calves were born light and darken rapidly
with age. How rapidly was not specified. All of the calves we saw in Hawaii
were dark above, except for pectoral fin coloration as noted and, occasionally, somewhite coloration on the dorsal surface of the tail flukes. We cannot say whether
the calves we saw had already darkened, or whether the light color of the newborn
does not occur in the Hawaiian population. Other than Chittleborough's observations on newborns, investigators seem to agree that coloration and age are notrelated.
The extensive color variation among individuals within the Hawaiian population, and here we include ventral as well as dorsal surfaces, may function in individual recognition among conspecifics. Colar patterns may also serve as signals
communicating movement intention or direction, as in the exposure underwater ofthe white surface of a raised pectoral or caudal fin to a school-mate swimming
nearby. Additionally, light ventral surfaces and darker dorsal surfaces provide forcryptic coloration important for predators, such as Mageptera, which at least in partSci. Rep. Whales Res. Inst.,
No. 29, 1977.

HUMPBACK WHALES OF HA WAii

81

feed on schooling fish (A.V. Yablokov, in Sokolov, 1971).
SUMMARY AND CONCLUSIONSThe Hawaiian population of humpback whales may number between 200 and 250
animals, though more detailed surveys of outlying islands and study of migratory
patterns is necessary to refine the bounds of these estimates. Our estimates concurwith Shallenberger's (1976) data on peak population size, peak population periods,
and that the population numbers are much reduced by or after the first to second
week of April. A ship survey from Kauai to Hawaii from 23 February to 7 March
1976 by the National Marine Fisheries Service counted 373 whales (M. Tillman,personal communication). The bases for this somewhat larger count have notyet been clarified.
Almost all of the whales were found within the 100-fathom contour surrounding the islands, a trait noted also for other breeding groups of humpback whales(Chittleborough, 1953; Winn et al., 1975). The principal areas of aggregation
were within the four-island region of Molokai, Lanai, Maui, and Kahoolawe, andwithin Penguin Bank extending 25-nm southwesterly from Molokai.
No unique nursery area was found, though the greatest numbers of calves werein two areas: Kalohi Channel between Molokai and Lanai, particularly on the
Lanai side, and on Penguin Bank. Since these two areas are also regions of maximum whale density, it is not clear whether the greater number of calves simply
reflects that fact. The number of calves recruited into the population was numerically small, and the recruitment rate, at its most optimistic, appeared to be
somewhat below normal expectations. Given the small population size, this seems
an unusual occurrence and leads to concern for the recovery of the stock. Highpriorities should be given to further investigations of recruitment rate.
Calves were typically found with multiple adults, most usually two (including
the mother). The additional adults seemed to serve a protective function as notedfrom the tightening of calf groups versus the dispersal of all-adult groups on approach of aircraft. Over the entire population, pod size was on the average larger
than that noted by investigators of humpback whale populations in other waters,either in breeding or feeding areas. Accurate determination of pod size seems
heavily dependent on close approach by ship or aircraft, and unless this is done thenumber of animals in a pod may be underestimated. Also, calves are often difficult to detect without close approach. Our data were in most cases based on
close-range observations.
The amount of migration between subregions within the island waters is unclear, though the 76% of the all-adult pods seen swimming on "determined"
courses suggested considerable local migration, but without any obvious pattern.
The remainder of the all-adult pods were milling about within some small area
often in great activity (16%), or else simply stationary or nearly so (8%). Milling
pods appeared to be engaged in courtship and mating activities, though actual
mating was not seen. Pods with calves were more frequently resting (26%) thanSci. Rep. Whales Res. Inst.,

No. 29, 1977.

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HERMAN AND ANTINOJA

were all-adult pods, possibly reflecting the lesser stamina of the calf (or mother)
and/or a requirement for nursing.
The most common formation for swimming pods was line astern (file), noted
in 38% of the cases. Diagonal arrays and line abreast (rank) each typified 19%of the swimming pods. The functions of the various formations were not clear.
Most of our data were obtained within the peak period of the migratory cycle,
from the end of February through to the third week of March. Therefore, wehave no information on changes in local aggregations over time. Data collectedby E. Shallenberger (1976), particularly those based on daily observations madeby the crews of hydrofoil craft transiting between the various islands of Hawaii,suggest that the earliest immigrants may arrive in the four-island region. As theseason progresses, the population appears to extend itself easterly and westerly, incomparatively small numbers, from the four-island region.
The routes by which the whales arrive at or leave the islands are unknown, as
is their migratory loci in northern waters. A survey we made in November 1976of the Northwest Hawaiian Islands, the small atolls and islands extending 1,200 nm
northwesterly to Midway and Kure from the main Hawaiian Islands, revealed nowhales. Coast Guard flights over this region by others in November 1975 andMarch 1976 (Shallenberger, 1976) also found no whales. However, in late
December 1976, a report was received of two pods of whales in the eastern portionof the Northwest chain, moving southeasterly. It may be that the Northwest
Hawaiian Islands are used as a migratory route by only a few whales, or only during portions of a season. Further studies of this area are necessary. Currently,
there seems to be no evidence that any humpback whales breed in this chain. Our
discussions with personnel based on the Midway Islands indicate that no humpback whales are ever seen there, nor heard there by underwater listening stations.
Nishiwaki's (1972) statement that humpback whales are frequently seen aroundthe Midway Islands in winter is therefore puzzling.
Based on their early arrivals in the four-island area, it may be that the principal migratory route to the main Hawaiian Islands is due south, south-southeasterly, or south-southwesterly from the higher-latitude feeding grounds along thenorthern rim of the North Pacific. The major return migration may simply be in
the reverse direction, as suggested for example, by the northerly heading of a podof six adult whales we observed in deep water on April 9th 10 nm off the west
coast of Hawaii. Direct observations of these possible migratory routes needs tobe implemented.
Coloration characteristics of the dorsal surfaces of the pectoral fins of the
Hawaiian whales strongly suggest that the population is not that observed in thefeeding areas near southeast Alaska. The coloration also appears to differ fromsome subpopulations observed near Kamchatka in the upper western Pacific,
though this is less certain. The degree to which there may be dispersal of the
Hawaiian population in the feeding grounds should be studied, and its degree ofintermingling with other populations ascertained. If the three North Pacific populations are like the Southern Hemispere humpback whales, little migration beSci. Rep. Whales R.es. Inst.,

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HUMPBACK WHALES OF HA WAil83

tween populations would be expected (Ivashin and Rovnin, 1967; Mackintosh,1947). However, ecological conditions vary widely in the higher latitudes of thetwo hemispheres. In particular, feeding areas are more restricted in the North
Pacific, so generalizations are difficult to make.
It was also noted that color variations within the Hawaiian population anddisplays of coloration could function in individual identification among conspecifics and as signals for movement intention and direction. Additionally the ventraldorsal variations provide cryptic camouflage.
Finally, the potential fragility of the Hawaiian population, given its small
numbers and apparent low recruitment rate, should be stressed. The annual migration of the population into Hawaii has been receiving increasing popular attention, and the number of people observing or wanting to observe the whales seems
to be increasing annually at an exponential rate. The generally good weather in
Hawaii and the nearshore clear-water regions favored by the whales makes theirobservation easy. While this is a scientific boon, and vitally important to the description and understanding of the natural behaviors and dynamics of a breeding
population of mysticete whales, the rare spectacle of the whales is an attraction toall. Increasingly, commercial and pleasure ships and small boats are launched towatch the whales, divers enter the water to observe, photograph, and perhaps
touch the animals, planes and helicopters on tourist runs circle the animals. Allof this unregulated activity constitutes a potential source of major harrassment
to the whales, and some controls on this activity are needed which will, first, protect and conserve the whales and, secondly, allow the expression of their benefit
to humans as an educational and aesthetic experience.
Harmer (1928) long ago warned that whales may abandon their preferredgrounds under harrassment, a warning that has been realized too often in whaling
history. When driven from a given locality, whales rarely return to it, selecting
instead secondary and likely less favorable grounds. Harmer's warning should bewell heeded in the case of the Hawaiian humpback whale.
ACKNOWLEDGMENTS

This research was supported in part by a grant from the Office of the Dean for
Research of the University of Hawaii. Use of the vessel Noi'i was arranged by
the Office of the Dean for Marine Programs, University of Hawaii. Appreciation
is extended to G. Curtis, H. Herman, M. Palmgren, and M. Yunker for their help
in obtaining and processing the data. M. Tillman and P. Forestell provided helpful comments on an earlier version of this paper. This paper is contribution No.
527 from the Hawaii Institute of Marine Biology.
REFERENCES
ANONYMOUS,
ANONYMOUS,

1848.
1856.

The whale fishery. Polynesian, May 20, p. 3.
Letter to the editor. Polynesian New Series, XII, Feb. 23.

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

84

HERMAN AND ANTINOJAANONYMOUS, 1858. Bay whaling at Lahaina. Polynesian New Series, XIV, Mar. 6.
ANONYMOUS, 1866. Bay whaling. Pacific Commercial Advertiser, X, Mar. 10.
ANONYMOUS, 1975. Humpback whale. Report to the Congress by the National Marine Fisheries Service/
National Oceanic and Atmospheric Administration on Administration of the Marine Mammal Protection Act of 1972. Washington D.C., June 1975, 131-132.
BALDWIN, D., 1858. Letter Mar. 2, 1858. Journal qfthe Rev. D. Baldwin, 1848-1858, III. Hawaii Mission
Children's Society, Honolulu. (Unpublished).
BECKWITH, M., 1970. Hawaiian Mythology. Univ. of Hawaii Press, Honolulu, 575 p.
BRYAN, W. A. 1915. Natural History of Hawaii. The Hawaiian Gazette, Honolulu. 596 p.
CHAPMAN, D. C., 1974. Status of antarctic rorqual stocks. In: W. E. Schevill (ed.) The Whale Problem:
A Status Report. Harvard University Press, Cambridge, 218-238.
CHITTLEBOROUGH, R. G., 1953. Aerial observations on the humpback whale Megaptera nodosa (Bonnaterre),with notes on other species. Aust. J. Mar. Freshw. Res., 4: 219-226.
CHITTLEBOROUGH, R. G., 1959. Determination of age in the humpback whale Megaptera nodosa (Bonnaterre). Ibid., 10: 125-143.
CHITTLEBOROUGH, R. G., 1965. Dynamics of two populations of the humpback whale Megaptera novaeangliae(Borowski). Ibid., 16: 33-128.
DAWBIN, W. H., 1966. The seasonal cycle of humpback whales. In: K. S. Norris (ed.) Whales, Dolphinsand Porpoises. Univ. of California Press, Berkely, 145-170.
GOSLINE, W. A., 1965. Vertical zonation of inshore fishes in the upper water layers of the Hawaiian
Islands. Ecology, 46: 823-831.
GuLLAND, J. A., 1971. The effect of exploitation on the numbers of marine animals. In: P.J. den Boer and
G. R. Gradwell (eds.) Dynamics of Populations. Centre for Agricultural Publishing and Documentation, Wageningen, Netherlands, 450-488.
GuLLAND, J. A., 1972. Population dynamics of world fisheries. Univ. of Washington Sea Grant Publication WSG 72-1.
HARMER, S. F., 1928. The history of whaling. Presidential address delivered to the Anniversary Meeting of the Linnean Society of London.
INTERNATIONAL WHALING STATISTICS II, 1931. Ed. by the Committee for Whaling Statistics, Oslo.
INTERNATIONAL WHALING STATISTICS LVII, 1966. Ed. by The Committee for Whaling Statistics, Oslo.
IvASHIN, M. V. and A. A. RovNIN, 1967. Some results of the Soviet whale marking in the waters of theNorth Pacific. Norsk Hvaifangst-Tid., 56: 123-129.
]ONES, M., 1938. Whaling in Hawaiian waters. Paradise of the Pacific, 50: 20.
KING, J. E. and J. DEMOND, 1954. Zooplankton abundance in the central Pacific. U.S. Department of
the Interior, Fish & Wildlife Service, Fishery Bulletin 82.
KING, J.E. and T. S. HmA, 1954. Variations in zooplankton abundance in Hawaiian waters, 1950-52.
U.S. Department of the Interior, Fish & Wildlife Service, Special Scientific Report: Fisheries No. 118.
KIRTLEY, B. F., 1971. A Motif-Index of Traditional Polynesian Narratives. Univ. of Hawaii Press, Honolulu,
486 p.
KELLOGG, R., 1929. What is known of the migrations of some of the whalebone whales. Ann. Rep. Smithsonian Inst.for 1928, 467-494.
LILLIE, D. G., 1915. British Antarctica (Terra Nova) Expedition, 1910. Natural History Reports, ,Zoology,

17: 85-124.
MACKINTOSH, N. A., 1947.

The natural history of whalebone whales. Ann. Rep. Smithsonian Inst.for 1946,
235-264.
MACKINTOSH, N. A., 1972. Biology of the populations of large whales. Science Progress, Oxford, 60: 449464.
MALO, D., 1951. Hawaiian Antiquities. Bernice P. Bishop Museum, Honolulu, Special Publication No. 2.
(First published, 1838), 278 p.
MARcuzz1, G. and G. PrLLERI, 1971. On the zoogeography of cetacea. In: G. Pilleri (ed.) Investigations
on Cetacea, III: 101-170.
MATTHEWS, L. H., 1937. The humpback whale, Megaptera nodosa. Discovery Rep., 17: 7-92.
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

HUMPBACK WHALES OF HAWAII

85

MITCHELL, E., 1974. Present status of northwest Atlantic fin and other whale species. In: W.E. Schevill(ed.) The Whale Problem: A Status Report. Harvard Univ. Press, Cambridge, 108-169.
MYERS, N., 1975. The whaling controversy. American Scientist, 63: 448--455.
NEMOTO, T., 1964. School of baleen whales in the feeding areas. Sci. Rep. Whales Res. Inst., 18: 89-110.
NrsmWAKI, M., 1959. Humpback whales in Ryukyuan waters. Sci. Rep. Whales Res. Inst., 14: 49-87.
NISHIWAKI, M., 1962. Ryukyuan whaling in 1961. Ibid., 16: 19-28.
NISHIWAKI, M., 1965. Whales and Pinnipeds. Tokyo Univ. Press, Tokyo, 439 p.
NISHIWAKI, M., 1966. Distribution and migration of marine mammals in the North Pacific area. Presented at Symposium No. 4 of the Eleventh Pacific Science Congress.
NISHIWAKI, M., 1972. General biology. In: S.H. Ridgway (ed.) Mammals of the Sea: Biology and Medicine,
Chas. C. Thomas, Springfield, Illinois, 3-204.
OMURA, H., 1953. Biological study of humpback whales in the Antarctic whaling area IV and V. Sci.
Rep. Whale Res. Inst., 8: 81-102.
OMURA, H., 1955. Whales in the northern part of the North Pacific. Norsk Hvaifangst-Tid., 44: 323-345
and 395-405.
OMURA, H., K. MAEDA, and I. MIYAZAKI, 1953. Whaling in the adjacent waters of Japan. Norsk Hvalfangst-Tid., 42: 199-212.
PAYNE, R., 1976. At home with right whales. National Geographic, 149: 322-339.
PIKE, G. C., 1953. Color pattern of humpback whales from the coast of British Columbia. J. Fish. Res.
Board of Canada, 10 :-320-325.
PuKur, M. K. and S. H. ELBERT, 1971. Hawaiian Dictionary. Univ. of Hawaii Press, Honolulu, 590 p.
RICE, D. W., 1963. Progress report on biological studies of the larger cetaceans in the waters off California.
Norsk Hvalfangst-Tid., 52: 181-187.
RrcE, D. W., 1974. Whales and whale research in the eastern North Pacific. In: W.E. Schevill (ed.) The
Whale Problem: A Status Report. Harvard Univ. Press, Cambridge, 170-195.
SCAMMON, C. M., 1874. The Marine Mammals of the Northwestern Coast of North America, Together
with an Account of the American Whale Fishery. G.P. Putnam, New York, (reprinted by Dover Press,
New York, 1968), 319 p.
SEBER, G.A.F., 1973. The Estimation of Animal Abundance. Griffin, London, 499 p.
SHALLENBERGER, E.W., 1976. Report to Seaflite and Sea Grant on the population and distribution of
humpback whales in Hawaii. (Mimeo ).
SoKOLOV, V., 1971. Cetacean research in the USSR. In: G. Pilleri (ed.) Investigations on Cetacea. III,pt. 2: 317-346.
SYMONS, H. W. and R. D. WESTON, 1958. Studies of the humpback whale Megaptera nodosa in the Bellinghausen Sea. Norsk Hvaljangst-Tid., 47: 53-81.
TOMICH, P. Q., 1969. Mammals in Hawaii. Bishop Museum Press, Honolulu, 238 p.
ToMILIN, A. G., 1967. Mammals of the U.S.S.R. and Adjacent countries, IX, Cetacea. Israel Program for Scientific Translations. Jerusalem, 756 p.
TOWNSEND, C. H., 1935. The distribution of certain whales as shown by logbook records of American
whaleships. Z,oologica, 19: 3-50.
WADA, S., 1972. The ninth memorandum on the stock assessment of whales in the North Pacific. Unpublished report submitted to the Scientific Committee, International Whaling Committee.
WILSON, E. 0., 1975. Sociobiology: The New Synthesis. Harvard Univ. Press, Cambridge, 497 p.
WINN, H. W., R. K. EDEL and A. G. TARUSKI, 1975. Population estimate of the humpback whale Megaptera novaean.tfliae in the West Indies by visual and acoustic techniques. J. Fish. Res. Board of Canada,
32 ; 499-506.
WOLMAN, A. A., 1972. Humpback whale. In: A. Seed (ed.) Baleen Whales in Eastern North Pacific andArctic Waters. Pacific Search, Seattle, 38-42.

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

OBSERVATIONS ON THE BEHAVIOUR AND OTHER
BIOLOGICAL ASPECTS OF THE GANGES SUSU,
PLATANISTA GANGETICA
A.K.M. AMINUL HAQUE
Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh, Bangladesh

MASAHAR U NISHIWAKI
University of the Ryukyus, Naha, Okinawa

TOSHIO KASUYA
Ocean Research Institute, University of Tokyo, TokyoANDTERVO TOBAYAMA
Kamogawa Sea World, Awa-gun, Chiba

ABSTRACT

Observations on the behaviour of the Ganges susu, Platanista gangetica(Roxburgh, 1801 ), indicated that these animals frequent the confluence of asmaller stream with the main river, even with over-flooded banks, for food
fishes. The most satisfactory method so far tried for capture of these animals
was the use of' jagatberh '. With a little care these could be easily transported over long distances. Though they are known to be side-swimming, theGanges susu cruised in normal fish-like movement with the body in normal,
upright position. Rate of breathing showed individual and diurnal variations,the rate being more for younger specimens, and again during day-time. One
susu was seen chasing a big fish at a tremendous speed, another attacked agoose, and a third one attacked a fish caught in the hook and thereby itself got
caught in a locked-jaw condition. Two others reportedly were seen in theact of mating about an hour after sunset in August 1959. Parturition in theseanimals appears to occur around May, with another peak possibly aroundDecember.

INTRODUCTION

Thirteen live specimens of the Ganges susu, Platanista gangetica (Roxburgh, 1801),
collected at different times from the Brahmaputra-Jamuna-Meghna river-systems
during the period from January 1970 to May 1973 were each maintained for atime in ornamental pool, civil-work ponds, and/or in portable swimming pool in
the Agricultural University Campus at Mymensingh, Bangladesh. These wereamong a total of 44 specimens collected and studied during investigations on theSci. Rep. Whales Res. Inst.,
No. 29, 1977, 87-94.

88

HAQUE, NISHIWAKI, KASUYA AND TOBAYAMA

biology of the Ganges susu. Various aspects of their behaviour during captivity
in these small, artificial waterbodies as well as on land and in the river werestudied.
METHOD OF CAPTURE
The Ganges susu were found to avoid fast-moving boats, and seemed to be able tosense the presence of nets set in the vicinity. Various methods were tried for capture of these animals. The most satisfactory method was, however, found to be
the use of a special type of seine-net, locally called 'jagatberh' used for catching
bigger carps and other fishes in the river when the water-level was low. A row ofsuch nets mounted on specially constructed rafts is placed across the river at two
points each usually several kilometers apart. Dolphins are found to frequent theconfluence of a smaller stream with the main river evidently for food-fishes (Kasuya and Aminul Haque, 1972). This was true even with over-flooded bank of theriver. If the two components of the jagatberh were placed in the river enclosing
such confluences, chances are that several specimens of dolphin would be rounded
up towards the end of the jagatberh operation. Care has to be taken to remove
the dolphins from the net as quickly as possible, as otherwise the dolphins may getentangled in the net, and get drowned.
Harpooning may be possible at the confluence of two streams frequented bydolphins, but this was not tried.
HANDLING
On land the dolphins were relatively calm, showing not much of visible distress.
When picked up, they would struggle, within manageable limits, trying to wriggle
out of hands. An interesting thing noted in a number of cases was that supported
on one hand placed just below the throat-region, the dolphins became calm andstill, stopping all strugglings. This was most pronounced in a calf about three
weeks old (No. 33, 76 cm, ~) that had been held in the swimming pool for 30days since 8 June 1970.
TRANSPORTATION
Transportation on land from the place of capture to Mymensingh was easily doneon a stretcher by two men, or on the lap by one man-longer distances being covered by rickshaws or trains with the animal left on the footboard or on the floor of
the train compartment, as the case may be. The animal was loosely wrapped up
with a length of rug leaving the blow-hole uncovered, the rug being kept wet byoccasional sprinkling of water so as to keep the skin moist and cool. When released in artificial waterbodies, like ponds, the animals recovered in no time, without any apparent ill-effects. The breathing rate stabilised slowly from little under
500 times per hour on land to about 65 times per hour in water.
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

BEHAVIOUR OF GANGES SUSU89

For really long distances covering several thousand kilometers (MymensinghDacca, 200 km by truck; Dacca-Bangkok-Manila-Tokyo, 5,000 km by plane; andin some cases, Tokyo-Kamogawa, 100 km by truck again) the animals, duly wrapped up with wet rug, were placed in wooden crates of suitable size lined with
polyethylene sheets and with 7-10 cm of water added. The animals stood the long
journeys, in some cases, of about 21 continuous hours, surprisingly well, and recovered from the shock of the unusual journey fairly quickly.
SWIMMING

In confined, shallow waters-for example, in ornamental pool (865 X 360 X
45 cm deep, with a fountain-base, 65x65 cm, in the middle), small pond (960X
725 X 80 cm deep), or swimming pool (450 cm dia. X 105 cm deep )-the dolphinsswam on one side nodding the head continuously in ' yes ' motion. One remarkable thing noted is that, of the thirteen specimens observed in shallow waters, all
except one swam in anti-clockwise direction, that is, on the right side, while only
one swam in clockwise direction or on the left side. This 'right- or 'left-handedness' may well be controlled genetically, so that occasional individuals with left
side-swimming may not be unexpected.
The Indus susu, P. minor Owen, 1853, has also been reported to be a sideswimming cetacean with individuals moving either clockwise or anti-clockwise(Herald et al., 1969). We are, however, inclined to believe that side-swimming in
the Ganges susu is only one aspect of its swimming behaviour under specific environmental conditions-like small, confined area and depth of the waterbody. Further, contrary to popular explanation for side-swimming, this may not have anything to do with food-seeking or food-catching.
On one occasion, as described elsewhere in this paper (vide infra), a specimenof the Ganges susu was seen chasing a big fish in the river at a tremendous speed.
This was a normal, fish-like swimming movement, with the body in normal, upright position.
TERRITORY FORMING
Ganges susu are non-gregarious creatures (Kasuya and Aminul Haque, 1972),
although occasional two-most probably mother and calf as suggested by sizedifference-have been seen swimming up or down the river.
Two specimens (No. 31, 138 cm, ~; and No. 32, 123 cm, 6) maintained ina pond during the period from 17 May to 21 August 1970, established themselvesin two mutually exclusive areas in the pond, never crossing-as far as could beascertained from their surfacings-into each other's territory. Also, they were observed never fighting with, or chasing, each other in the pond. These observations
were true of two other specimens (No. 22, 188 cm, 6; No. 24, 166 cm, 6) similarly maintained in another pond.
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

HAQUE, NISHIWAKI, KASUYA AND TOBAYAMA

90

BREATHING RATE

The ' blowing ' of the Ganges susu is a composite act-exhalation, quickly followed
by inhalation-both done so quickly within a fraction of a second that the twosounds appear to be of one single action. It is interesting to note, however, thaton one occasion on 15 May 1973 a specimen (No. 38, 91 cm, d') placed on a tablein the Laboratory was found to have missed inhalation in one blowing, which was
followed after only two seconds by another blowing, this time only inhalation taking place, so that for all practical purposes there were two separate blowings forexhalation and inhalation with a two-second interval between the two.
There were individual and diurnal variations in the rates of breathing of theseanimals. Record of breathing as kept for different specimens maintained in artificial waterbodies as well as on land has been summarised in Table 1 below. It
may be noted from the Table that the minimum breathing rates for any individuals
TABLE 1.

RATES OF BREATHING OF SEVEN SPECIMENS OF PLATANISTAGANGETICA UNDER DIFFERENT CONDITIONS(Unless otherwise stated, breathing rate was recorded for 60 continuous
minutes each time within the hours mentioned.)
Rate of breathing per hour
On landSpecimen
No.

Sex

Size
(cm)

22

cJ

188

24
31

cJ

166
138

~

123

32

33
36
38

~
~

cJ

76
130.5
91.0

Date

27-4-'70
8-5- 170
8-5-'70
15-5-'70
16-5-'70
17-5-'70
26-5-'70
21-8-'70
15-5-'70
16-5-'70
17-5-'70
26-5-'70
21-8-'70
9/10-6-'70
24-6-'70
30-9-'70
15-5-'73

0600
to
1000
hrs.

1200
to
1600
hrs.

492bJ

In water
1900
to
1830
hrs.

0600
to
1000
hrs.

1200
to
1600
hrs.

1700
to
1830
hrs.

53
43
58
121/2al127 /2al52
42
54
129/2al

58

0000
to
0100
hrs.

348bJ
64
40
121/2•l127/2aJ

444bl

129/2•)

204bl
67
88
88
96

68
92

106C)
40
58

156d>

•> Combined data for two specimens (Nos. 31 & 32.)b> Breathing recorded for 15 minutes (and multiplied by 4) while being transported in a railway cornpartment.
cJ Breathing recorded one day after capture.
d> Breathing recorded for 10 minutes (and multiplied by 6) in the laboratory half an hour after arrivalby road.
Sci. Rep. Whales Res. Inst.,

No. 29, 1977.

BEHAVIOUR OF GANGES SUSU

91

were recorded for two specimens (Nos. 33 and 36) at nights, and the same could
indicate their hours of sleeping. Two other specimens (Nos. 31 and 32) also recorded low breathing rates (on 21 August 1970) when they had in fact become
very much emaciated due apparently to starvation. One of these latter two specimens (No. 31) died some 10 hours after the minimum breathing rate of 40 per
hour had been recorded, and the other specimen was sacrificed the next day.
During transportation, the breathing rate of these animals was, for obvious
reasons, significantly higher than under acclimatised state in water.
FEEDING HABITS(a) Acceptance or rejection of food: While specimens of the Ganges susu readily accepted food (small fishes) from the handler in the ornamental pool and in theoceanarium, those kept in the pond did not accept food offered to them, nor did
they seem to take any food from the pond which had previously been stocked withan assortment of fishes of various sizes. Specimens left in ponds seemed to haveslowly starved to death as the general emaciated state of health and post-mortem
examination of the stomach would indicate.
(b) Attack on a goose: Specimen No. 22, while in a pond, once bit the neck of
a domestic goose, Anser cygnopsis cygnoides, while the latter was, in its characteristicmanner, probing the pond-bottom for food. The dolphin, however, loosened its
grip and the goose managed to come out of the water. The injured goose wasthen slaughtered, and on examination the neck and part of head were found tohave rows of tooth-marks on both the sides, establishing that the goose had reallybeen bitten by the dolphin (Plate I, Fig. 1).
(c) Dolphin caught in a hook: An unusual case of a dolphin getting caught ina hook was brought to light on 28 September 1970. On the preceding night twoanglers had placed a series of hooks each hanging from a bamboo rod, and fixednear the bank of the river. There were live baits (small fish or frog) hooked to theline, the hooks just touching the surface of water. This was a common local method of catching such predatory fishes as freshwater shark (Wallago attu, a kind of
Teleostomi), featherback (Notopterus chitala) and snakeheads (Channa striatus and C.
marulius).
At about 0200 hours, local time, the anglers were attracted by violent splashing sounds from the direction of one of the hooks. They took this to be caused by
an extra-large freshwater shark, and hauled it up with a push-net. They were,
however, shocked to see a Ganges susu instead, and decided to present the
curious specimen to the Faculty of Fisheries across the river. When the specimen
was brought to us early in the morning, we were bewildered to understand thecircumstances under which the dolphin got caught in the hook. As stated above,
the hook had a live bait of a frog or small fish, which lured to the hook a 36 cm
freshwater shark, which, in its turn, attracted the dolphin. On examination thehook at the end of a length of string, was found deep into the oesophagus of thefish, which, in its turn got caught in the jaws of the mammal, the hook nowhere
Sci. Rep. Whales Res. Inst.,
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HAQUE, NISHIWAKI, KASUYA AND TOBAYAMA

92

even touching the jaws of the latter. Apparently, the dolphin found itself in a'locked-jaw ' condition, in which condition it was still fixed to the fish in the latter's abdomen and tail region that bore on the dorsal side distinct tooth-marks ofthe dolphin (Plate I, Figs. 2-4). The 130.5 cm dolphin (No. 36) was still alive,
and after being maintained for 9 days in a swimming pool, was transferred to
Kamogawa Sea World in Japan to start a new life in the oceanarium there.
CHASING A BIG FISH

On 17 October 1969, when the river old Brahmaputra was in half spate, a big (approximately 45 cm) carp, Labeo rohita, was seen being chased by a Ganges susu
close to the surface of the water, to almost where one of the present authors withseveral friends had been standing near the edge of the water. Both the fish andthe mammal were cruising at tremendous speeds, the latter continuing to chasethe former to some 10 meters beyond the amazed on-lookers after which they bothswam deeper down in water beyond sight.
MATING

Judging by the date of capture of very young, untoothed and teething calves, itappears safe to say that parturition in the Ganges susu in the river-system in Bangladesh takes place around May. According to Anderson (1878) parturition in
TABLE 2. PARTICULARS OF 13 YOUNG SPECIMENS OF GANGES SUSU,
PLATANISTA GANGETTCA, ALL LESS THAN 120 CM IN LENGTH
Specimen No.
Sex
at BAUat ORI

33

14
21

38

3
2
7
II
15
4
16
9
17

~
~

6

2
5
7
11
3
13

6
6
~

6
~

6

6
6
6

15
KS-76-5

6

~

Size
(cm)

Date ofcollection
or capture

27
67.4
76
91

100.5
105
llO
113
113
115
115
117
118
118

River*

Remarks

28- 8-67
8- 6-70
8- 7-70**
15- 5-73

M
B

FoetusHair follicles very prominent;
Teeth not erupted
Hair follicles prominent;
Only 10 or II teeth on eachside of the jaws erupted;
Curdy substance found in mouth?- 6-69?- 6-69

B
B
B
B

20-10-69
6- 1-70
26- 1-70
23- 8-69
26- 1-70
20-12-69
26- 1-70
13- 9-76

B

J
B

J
B
J
B

* River-names : M-Meghna; B-Brahmaputra; J-Jamuna** Date of taking second measurement.

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

BEHAVIOUR OF GANGES SUSU

93

the Ganges susu may occur in two seasons-between April and July, and November and December. Harrison (1972), however, believes that parturition inthis animal probably occurs in April, and he gives the length of neonates as 7075 cm. From details of 13 young specimens, all measuring less than 120 cm (Table2), it may reasonably be concluded that parturition in the Ganges susu takes
place around May. Whether a second season for parturition exists for this animalcannot be confirmed from available data. The capture of 5 of the 13 specimens
listed in the Table, all belonging to the same size-group (113-118 cm), in December-January, indicates that these were all born about the same time of the year.
Since the age of these individuals was estimated with dentinal growth layers as 1.0
year (Kasuya 1972), it seems possible to expect another parturition peak aroundDecember.
There is no reliable information to estimate the period of gestation in theGanges susu. Assuming that the period of gestation in these animals is 9 months(Anderson, op. cit.), mating would appear to take place around July/August. The
collection of a 27 cm foetus on 28 August 1967 at Chandpur (R. Meghna) would
lend support to this assumption.*
One first-hand report from a Professor, an M.A. in Bengali language, andhaving no biological background, describes an incident involving two dolphins(Prof. M.A. Nawaz, BAU; pers. comm.). It was about an hour after sunset on
14 August 1959. The gentleman, while crossing the river Burhiganga at Dacca on
board a small country-boat, was alarmed at violent splashings in the water of two
huge struggling creatures, locked in embrace, and rolling and almost shooting out
of water. Both the Professor and the boatman watched in horror this 'struggle'
that was apparently an act of mating of two dolphins. The boatman was, however, categorical that it was actually so.
ACKNOWLEDGMENT

The authors wish to thank the authorities at the Bangladesh Agricultural University, Mymensingh, Bangladesh, at the Ocean Research Institute, University ofTokyo, Japan, and at the Kamogawa Sea World, Chiba, Japan, for the generous
help and co-operation received at different times during the period of study reported in the present paper.

* Since the paper was sent to the press, a second foetus, 30 cm, has been collected on 13 October 1977
from the river Meghna.
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

94

HAQUE, NISHIWAKI, KASUYA AND TOBAYAMAREFERENCES
ANDERSON, J., 1878. Anatomical and zoological researches: comprising an account of the zoological result of the two
expeditions to Western Yunnan in 1868 and 1875, and a monograph of the two cetacean genera Platanista and Orcella, vol. 1. B. Quaritch, London, 564 p.
HARRISON, R.J., 1972. Reproduction and reproductive organs in Platanista indi and Platanista gangetica.
In: Investigatians on Centacea Vol. IV, ed. G. Pilleri, 71-82, Berne.
HERALD, E. S., R. L. BROWNELL, Jr., F. L. FRYE, E . .J. MORRIS, W. E. EVANS, and A. B. ScoTT, 1969. Blind
river dolphin: First side-swimming cetacean. Science, 166: 1408 :1410.
KAsUYA, T., 1972. Some information on the growth of the Ganges dolphin with a comment on the Indus
dolphin. Sci. Rep. Whales Res. Inst., 24: 87-108.
KASUYA, T., and A.K.M. AMINUL HAQ,UE, 1972. Some information on distribution and seasonal movementof the Ganges dolphin. Sci. Rep. Whales Res. Inst., 24: 109-115.

EXPLANATION OF PLATE
PLATE I
Fig. 1. Head of a goose with rows of tooth-marks of a Ganges susu.
Figs. 2-4. Specimen of a freshwater shark ( Wallago attu) with tooth-marks of aGanges susu on its body.

Sci. Rep. Whales Res. Inst.,

No. 29, 1977.

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A COMPARATIVE MORPHOLOGY OF ANAL TONSILSIN PLATANISTIDAEFUSAO YAMASAKI, SHUNRO KOMATSU
Department of Biology, Sapporo Medical College, Sapporo

AND
TOSHIRO KAMIYA
Department of Anatomy, Faculty of Medicine, University of Tokyo, Tokyo

ABSTRACT

Anal tonsils, complex lymphoepithelial structures in the anal canal, were
found in Platanista gangetica, and morphological observations were made macroand light microscopically. In Platanista, the anal tonsils are mainly present
and scattered on the oral half of the anal canal, however, they are relatively
poorly developed and small in number. The formation of the anal tonsils cannot be found in Inia geoffrensis, although accumulations of lymphoid tissue areobserved as far as the posterior part of the anal canal. In Pontoporia blainvillei,
even such accumulations are absent from all parts of the anal canal. Comparative considerations of the anal tonsils are mentioned in Platanistidae and insome other cetaceans.

INTRODUCTION

Ortmann (1960) reviewed the lymphatic apparata and so-called "anal tonsil" inthe anal region in many mammals, however, in his description no mention wasmade of those in Cetacea. Uys and Best (1966) made a pathological observation
on Cetacea in which they described the anal tonsil in sperm whales. This structure is present externally around the anal opening. Cowan and Brownell (1974)
reported the anal tonsil in the anal canal of gray whales and made comparativeand functional considerations on this subject. We made an anatomical observation on the digestive tract of the Ganges susu in 1972, however, we overlooked the·anal tonsils at that time. Recently, we have reexamined the previous materials
and observed other specimens of this dolphin, and similar structures to that in graywhale were found in the anal canal. No reports on this subject in Cetacea, except
for the abovementioned two reports, have been published to date and there still
remain many problems of ambiguity in the biological meanings of the anal tonsil.
Therefore, a brief morphological description of the anal tonsil in the Ganges susu
will be added to the knowledge of that of Cetacea. In addition, comparative observations were done on two other kinds of Platanistidae, Franciscana and Boutu,
and also on the striped dolphin .
.Sci. Rep. Whales Res. Inst.,

No. 29, 1977, 95-100.

96

YAMASAKI, KOMATSU AND KAMIYAMATERIALS AND METHODS
Six specimens of Ganges susu, Platanista gangetica (body length; 76.0, 105.5, 106.5,
113.0, 118.0, 127.0 cm) were used in this study. For comparison four Franciscana,Pontoporia blainvillei (98.5, 113.5, 121.0, 171.0 cm) and a Boutu, lnia geoffrensis(204 cm) were examined. The Platanista and the Pontoporia were collected by the
Cetacean Research Expedition of the University of Tokyo. Specimens of 76.0,
113.0, 118.0 and 127.0 cm in the Platanista were collected in the Brahmaputra
River (Bangladesh) from 1969 to 1970 and the other in the lndus River (Pakistan)in 1974. The Pontoporia were caught off the Uruguayan coast from 1972 to 1973.
The lnia was offered to us by the Kamogawa Sea World Aquarium in Chiba,
Japan. Six striped dolphins, Stenella coeruleoalba, collected off the Pacific coast of
Izu peninsula, Japan, were also examined as one example of marine dolphins.
Materials were fixed in 10% formalin solution at the site of capture and sent
to our laboratory. After macroscopical observations from the interior of the anal
canal, the whole length of which was cut serially in about 5 mm thicknesses, detailed examinations were done. Histological pieces were embedded in paraffin andcelloidin, and then sectioned and stained with hematoxylin and eosin.
OBSERVATIONS AND COMPARATIVE CONSIDERATIONS
The anal canal, from the posterior end of the rectum to the anal orifice, varies inlength with individual body length and is about 4 to 7 cm long in the Platanista observed. The epithelium shows an abrupt change at a point between the rectum
and anal canal from intestinal glandular mucosa to stratified squamous epitheliumin all species of dolphins observed. We have labelled this point the recto-analepithelial transition (Takahashi and Yamasaki, 1972). Cowan and Brownell, in
the gray whale, labelled it as the muco-squamous junction. The oral half of theinner surface of the anal canal in Platanista is somewhat irregular and uneven inappearance and several longitudinal folds are present on the posterior half (Fig. 1).
The epithelium of the anal canal becomes pigmented towards the anal orifice andcontinues to the external skin.
Complex lympho-epithelial structures in the anal canal, anal tonsils, are foundin Platanista, with the exception of one 76 cm specimen. A well developed structure (Fig. 2) similar to that of the gray whale observed by Cowan and Brownell
was found. This structure may correspond to the ' first type ' described by them,
however, the development and the number of the tonsils in Platanista is rather poorand less, respectively, than that of the gray whale. There seems to be no sexual
difference. In Platanista the anal tonsils are present but scattered in the oral threefifths of the anal canal, except for the zone adjacent to the recto-anal transition,
approximately 2 to 3 mm in width.* The tonsils are rather well developed in the* In our previous paper on the intestinal tract of Platanista (1972) there was no mention of this structure
because we had observed only the part adjacent to the recto-anal transition where no tonsils were present.
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

ANAL TONSIL IN PLATANISTIDAE

97

oral half of the anal canal and they decrease in size and number towards the posterior. There are a few structures which form an independent elevation and these
are usually found grouped in the irregular or longitudinal folds of the anal canal,
forming oval masses 2 to 3 mm thick, 4 to 5 mm wide and 5 to 6 mm long. In
the gray whale, distinct openings of the tonsilar crypts are abundant in Figure 1of Cowan and Brownell's article. In Platanista they are very small, usually pinhole in size, and few distinct ones are found on the inner surface of the anal canal.
Although it is fairly difficult to distinguish the existence of the tonsilar crypt with
the naked eye, especially in younger animals, when viewed through a stereomicroscope small openings can be recognized on the surface. When viewed on a crosscut surface of the anal canal masses of lymphatic nodules, being yellowish gray incolor, are rather easily distinguishable.
Anal tonsils in the gray whale, of which the anal canal is 30 to 40 cm long,
are found on the posterior part of the muco-squamous junction extending overabout 10 cm in width (Cowan and Brownell). In sperm whales, they are present
as numerous lumps and exist externally around the anal opening (Uys and Best).
The location and the distribution of the tonsils may vary considerably among different species of some cetaceans which may have anal tonsils.
The sample shown in Figure 2 is of a well developed, independent tonsil in
Platanista (113 cm) which we observed. It shows a distinct epithelial elevation,
about 5 mm across and 3 mm high. The tonsil is composed of a mass of lymphatic nodules with a few germinal centers. The mass is about 4 mm in diameter.
Its capsulation of connective tissue which is continuous with that of the submucosa
is poorly developed. The tonsilar surface is covered with stratified squamous
epithelium, invaginated into the subjacent lymphoid tissue to form a central crypt,
which ramifies into a small number of subdivisions. Invaginated epithelium fromthe free surface becomes thinner and almost disappears at the mid-portion of thecrypt. In cases of younger specimens (105.5, 106.5 cm), tonsils are small in size,
1 to 3 mm across, and they are grouped in places in the submucosa (Fig. 3). The
crypts, some of which are slightly tortuous in course, ramify near the surface tothe adjacent tonsils which are separated by connective tissue, or the crypts of twoor three tonsils open onto the surface by a common opening. Lymphatic nodules
without crypts are often present next to the tonsils. In the deeper portions of thecrypts in younger specimens secondary papillae of their epithelia are poorly developed and the limit between the epithelium and lymphoid tissue is obscured by an
infiltration of the epithelium with lymphocytes. Small numbers of mucous glands
are present at the bottom of the structure. In younger cases, glands are seen near
the masses of lymphatic nodules. In the case of the 76 cm specimen, there can beseen a very few small aggregations of lymphocytes without the formation of lymphatic nodules in the submucosa.
Thus, Platanista has anal tonsils, which are mainly present in the oral half of
the anal canal, although relatively poorly developed and small in number. Since
the anal tonsils were not formed in the 76 cm specimen and in younger stage they
are small in size, it seems that the anal tonsils develop with age in Platanista as far
Sci. Rep. Whales Res. Inst.,

No. 29, 1977.

98

YAMASAKI, KOMATSU AND KAMIYA

as we have been able to observe.
Cowan and Brownell referred to the relation of the anal tonsils in Cetaceawith the avian bursa of Fabricius. They described the morphologic homology andsuggested the functional homology between the two structures. Assuming that theanal tonsils of Platanista develop with age, the relationship between the anal tonsils
and the bursa, which may degenerate with age, may be converse, and this problem
should be discussed based on further observations of the anal tonsils in other cetaceans.
On the other hand, in Inia, although we observed only a single case of a specimen of 204 cm in body length, diffuse accumulations of lymphoid tissue are observed in the submucosa to the posterior region of the anal canal. Crypt-likeepithelial invaginations can often be observed, but they are not always associatedwith accumulations of lymphoid tissue. Germinal centers are poorly developed.
In the Inia observed, well outlined organs of lymphoid tissue such as in Platanista
could not be observed (Fig. 4).
In contrast, in Pontoporia no accumulations of lymphoid tissue can be observedin any part of the anal canal and only a very few aggregations of lymphocytes canbe seen in all animals examined, as we briefly pointed out in a previous paper(Yamasaki et al., 1975). The submucosa is highly vasculized (Fig. 5).
In Stenella coeruleoalba, well outlined anal tonsils with distinct germinal centers
are present on the oral over about three-fourths of the anal canal. Many openingsof the tonsilar crypts are clearly visible to the naked eye at the region corresponding to the tonsils on the inner surface of the anal canal. Anal tonsils in this speciesof Stenella are far more well developed compared with those in Platanista.
There is a remarkable difference in the lymphoid tissue in the anal canal in
Platanistidae as mentioned above. It is interesting as to whether anal tonsils arepresent in other kinds of Stenella or not. Ortmann (1960) has already reviewed
the considerable variations in the presence of anal tonsils in all the species of mammals he observed, although no mention was made of those in cetaceans.
There seems to be a close relationship between the existence of the anal tonsils
and the distribution of the lymphoid tissues in the entire intestinal tract. Therefore, observation of the anal tonsils should be done along with that of the wholeintestinal tract in each species.
There are so few descriptions on this subject that further comparative observations on other cetaceans should be done and are needed to clarify biologicalmeanings from immunological, ecological and phylogenetical standpoints.
ACKNOWLEDGMENTS

We are greatly indebted to Dr. R. L. Brownell Jr., Department of Vertebrate
Zoology, National Museum of Natural History, Smithsonian Institution, Washington, D.C., who arranged for us to collect Pontoporia. Our sincere thanks are due to
Dr. K. Takahashi, Department of Anatomy, Sapporo Medical College, who gave
us valuable suggestions and advice for our study. The technical assistance of Mr.
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

ANAL TONSIL IN PLATANISTIDAE

99

A. Mori, Risto-Technical Center, Sapporo Medical College, is also acknowledged.
REFERENCES
COWAN, D. F. and R. L. BROWNELL Jr., 1974. Gut-associated lymphoepithelial organ ("anal-tonsil")in the gray whale. In: Functional anatomy of marine mammals. Vol. 2., ed. by R.J. Harrison, pp. 321327., Academic Press, London, New York and San Francisco.
ORTMANN, R., 1960. Uber den lymphatischen Apparat der Analregion und die sogenannte "Analtonsille"
bei Siiugetieren. Eine vergleichend histologishe Studie. ,Z. Anal. Entwicklungs., 121: 459-477.
TAKAHASHI, K. and F. YAMASAKI, 1972. Digestive tract of Ganges dolphin, Platanistagangetica. II. Smalland large intestines. Okajimas Fol. anat.jap., 48: 427-452.
Uvs, C.J. and P. B. BEST, 1966. Pathology of lesions observed in whales ftense<l at Saldanha Bay, South
Africa. ]. Comp. Path., 76: 407-412.
YAMASAKI, F., K. TAKAHASHI and T. KAMIYA, 1975. Digestive tract of La Plata dolphin, Pontoporia blainvillei. II. Small and large intestines. Okajimas Fol anat.jap., 52: 1-26.

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

YAMASAKI, KOMATSU AND KAMIYA100

EXPLANATION OF PLATE
PLATE I
Fig. I.

Inner surface of the oral three-fourths of the anal canal of a Platanista
gangetica (body length, 105.5 cm). The oral half of the surface is uneven in appearance and longitudinal folds are present on the posterior half. Anal tonsils
in Platanista are mainly present in the oral half of the anal canal. An arrowshows one of the tonsilar crypts which are usually fairly difficult to distinguishwith the naked eye. A recto-anal epithelial transition is clearly visible at the topof the photograph. Hollows seen in the longitudinal folds at the bottom of the
figure are not tonsilar crypts. X 3.3

Fig. 2. A photomicrograph of a well developed anal tonsil of a Platanista (113 cm).
Although no opening of the crypt is seen in this section, the surface epithelium
invaginates into the subjacent lymphoid tissue to form a central crypt, which ramifies into subdivisions. Germinal centers can be seen in places within the lymphoid tissue. x 15
Fig. 3. A cross section of the anal canal of the Platanista in Figure 1. In younger
specimens anal tonsils are rather small in size compared with the larger animals.
A tonsilar crypt shown by the arrow corresponds to the arrow in Figure 1. Anal
tonsils are grouped in places within the submucosa. Small glands are visible near
the anal tonsils. X 9
Fig. 4. A cross section of the oral part of the anal canal of an lnia geojfrensis (bodylength, 204 cm). Accumulations of lymphoid tissue are present but formation of
the anal tonsil cannot be seen in the lnia. Germinal centers are poorly developed.

x9
Fig. 5. A cross section of the oral part of the anal canal of a Pontoporia blainvillei(body length, 171 cm). No lymphoid tissue can be seen in any part of the anal
canal. Submucosa is highly vasculized. X 9

Sci. Rep. Whales Res. Inst.,

No. 29, 1977.

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COCCONEIS DIATOM ON THE SKIN OF FRANCISCANATAKAHISA NEMOTO
Ocean Research Institute, UnivmitY of Tokyo, TokyoROBERT L. BROWNELL, JR.
Smithsonian Institution, National Museum of Natural History,
Washington, D.C.

AND
TAKASHI IS HI MAR U
Ocean Research Institute, University of Tok)'O, Tokyo

ABSTRACTTwo species of diatoms are described from the skin films of Franciscanacaught in the adjacent waters to Urguay. Cocconeis ceticola is common
diatom on skin films, and one other naviculoid species is also found on thisdolphin.

INTRODUCTION

Many diatoms have been reported from skin films of larger baleen whales andsperm whales both in the North Pacific and in the Antarctic (Hart, 1935; Nemoto,1956). Species of diatoms are various, but Cocconneis ceticola is found generally on
whales examined. Those parasitic diatoms are common on all larger whales in thepolar waters and include many species which have not generally found in pelagicplankton (Nemoto, 1956). Cocconeis ceticola and its varieties and forms are common on Balaenoptera species and sperm whales, and some peculiar naviculoid diatoms, Stauroneis species are also found on sperm whales, which have not been described as a pelagic form.
Although many descriptions on parasitic diatoms have been made on larger
whales including killer ( Orcinus orca) and Baired beaked (Berardius bairdii) whales,
few observations on diatom films on the skin of small cetaceans have been reported. Only a few descriptions have been made by Harrison and Thurley (1974)
and Brownell (1975) recently.
Among many Franciscana studied in Urguay, some specimens had greenbrown films of diatoms on the body surface. We studied these diatoms with reference to diatoms found on other whales.
DESCRIPTIONSThe Franciscana (Pontoporia blainvillei) has been studied from 1971 to 1973 in Punta
Sci. Rep. Whales Res. Inst.,
No. 29, 1977, 101-105.

102

NEMOTO, BROWNELL JR. AND ISHIMARU

del Diablo, Urguay by one of us Brownell. The progress report on the biology of
those Franciscana studied is already given by Brownell (1975). Diatom films weremainly observed on the dorsal and lateral surface of the most fresh dolphins examined(Brownell, 1975). This observation suggests that more Franciscana may have had
diatom films on the skin surface if they were examined in more fresh and un-rubbed
conditon. The catch of those dolphins is done by gillnets by fishermen (Brownell,1975), which possibly have removed diatom films with epidermis of the skin ofdolphins.
TABLE 1.
Field

OBSERVATIONS OF DIATOM FILMS ON SKIN FILMS OF
FRANCISCANA IN URUGUYAN WATERS

No.

Sex

Body length(cm)

Weight(kg)

Date caught

Remarks

717

M

119

19.5

9 Aug. 1971

721
753

F
M

104
131

16.4

11 Aug. 1971
25 Aug. 1972

762

M
M
M

110
111
115

19.0

771
774

13 Sept. 1972
24 Sept. 1972
25 Sept. 1972

869
872

F
M

130.5
142

27.3
31.4

5 Jan. 1973
11 Jan. 1973

889

F

136.5

29.1

23 Jan. 1973

895

F

112.5

17 .3

28 Jan. 1973

Diatom film collected from left sideof dorsal fin.
Diatom film collected.
Diatoms present on dorsal side andlateral tail stock, flippers and side ofhead. Sample collected from tail stock.
Diatom film around base of dorsal fin.
Diatom film present.
Diatom film covering all of the animalareas of heaviest concentration werearound the gape and tail stock-areasof next heaviest concentration were
flukes (dorsal and ventral), the flippers(dorsal and ventral) and the dorsal fin.
Diatom film collected.
Heavy diatom film on dorsal andlateral surfaces.
Some diatoms on dorsal surface offlippers, dorsal fin, and tail stock.
Heavy diatom film on tail stock.

Diatom films are observed at least 10 dolphins in the studies carried out since1971, in which three diatom specimens have been collected from three dolphins.
The data of observations are given in Table 1. Generally diatom films are foundon the side of dorsal fin and the dorsal surface of flippers and tail stocks. It is considered also that diatom films are common on the surface of dorsal fins and flukes.
The seasons of catch of dolphins are both in winter (January) and summer (August) of the southern ocean, and dolphins which have been caught in both seasons
were infected with diatoms.
The collected samples are examined by scanning electron and ordinary microscopes. Among all samples, Cocconeis ceticola specimens are found. On one porpoise (RLB-717), naviculoid diatoms are also found.
Cocconeis diatoms found on the skin films of Franciscana are considered all
ceticola type and the variety form such as constricta form has not been found in samples. Although the shape of ceticola is somewhat oval but it is similar to thosefound on sperm whales. Sizes of diatoms are all within the general distributionof size which are reported up to date (Nemoto, 1958). Another naviculoid diatom
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

103

DIATOM FROM FRANCISCANA

is also found in specimens collected from No. 721 dolphin. This naviculoid diatom
is considered to be one of the definite records from the skin films of whales like thereport by Harrison and Thurley (1974), although there was some description of
Navicula sp. from fin whales (Amemiya, 1916), which is considered as Stauroneisspecies.

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Variety and deformation of Cocconeis diatoms on whales.

DISCUSSION

Many descriptions and discussions have been reported on diatom infection on theskin films of larger cetaceans. On the other hand, rather small numbers of observation have been reported on smaller cetaceans including dolphins. In the
Antarctic and both in the Atlantic and the Pacific, many diatom films have been
observed from blue, fin, humpback and sei whales even from sperm whales (Hart,
1935; Nemoto, 1956). Diatom films have also been observed in moderate sizedwhales of bottle-nose (Hyperoodon ampullatus) and the killer whales ( Orcinus orca) (Bennett, 1920) in the Antarctic. Although diatom films have been observed on dolphins in other occasions, few precise descriptions have been reported after 1920.
The notice of diatom films on dolphins, Lagenorhynchus cruciger and Cephalorhynchus commersonii was reported at South Georgia by Hart (1935), however no taxonomical observation was made on those diatoms. Harrison and Thurley (1974)
Sci. Rep. Whales Res. Inst.,

No. 29, 1977.

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DIATOM FROM FRANCISCANA

105

migration. The most of records of parasitic diatoms have been recorded from thewaters colder than 20°C. Especially Cocconeis ceticola has only been reported in thepolar waters.
The water temperature around the fishing ground of Franciscana are ranging
between 13° and 23°. The seasonal difference of water temperature is not sogreat as to show clear decline or decrease of infection of diatoms on the skin.
Perhaps more extensive research on dolphins and whales reveals the infection of
Cocconeis diatoms on whales are common in Urguay waters throughout the year.
REFERENCESAMEMIYA, I., 1916. [The propagation of diatoms on the skin of whales] (In Japanese). Rep. Jap. Soc.
Sci. Fish., l : 378-379.
BENNETT, A. G., 1920. On the occurrences of diatoms of the skin of whales (With an appendix by Nelson,
E.W.) Proc. Roy. Soc. London., 91 : 352-357.
BROWNELL, Jr. R. L. 1974. Progress report on the biology of the Franciscana dolphin, Pontoporia blainvillei,
in Uruguayan waters. J. Fish. Res. Bd. Can., 32: 1073-1078.
DAILEY, M. D., and R. L. BROWNELL, Jr., 1972. A checklist of marine mammal parasites.
In: Sam H. Ridgway [ed.], Mammals of the sea. Biology and medicine. 528-589. Charles C. Thomas,
Springfield Ill.
HARRISON, R.J. and K. W. THURLEY, 1974. Structure of the epidermis in Tursiops, Delphinus, Orcinus
and Phocoena. In: R.J. Harrison (ed.), Functional anatomy of marine mammals, 45-71. Academic Press.
HART, T. ]., 1935. On the diatoms of the skin film of whales and their possible bearing on problemsof whale movements. Discovery Rep. 10: 249-282.
KLIASHTORIN, L.B., 1962. The diatoms of the skin film of whales in the Far Eastern seas. Truqy Inst Okeanology A.N. U.S.S.R. 58: 314-321.
NEMOTO, T., 1956. On the diatoms of the skin film of whales in the Northern Pacific. Sci. Rep. Whales
Res. Inst., No. 11 :97-132.
NEMOTO, T., 1958. Cocconeis diatoms infected on whales in the Antarctic., Sci. Rep. Whales Res. Inst., 13:
185-191. 3 pls.

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

FOOD OF A KILLER WHALE: EAGLE STING-RAY,
MYLIOBATIS FOUND IN THE STOMACH OF
A STRANDED ORCINUS ORCA *HUGO P. CASTELLOModulo de Comunidades Nectonicas-Base Oceanografica Atlantica
Rio Grande, Brasil

ABSTRACTThe killer whale, Orcinus area feed on a variety of foods including sea mammals, sea birds, fishes and squids. Among fishes, teleosts seem to be more
frequently found in the stomach content than elasmobranchs. There are somerecords where electric ray, skates- and sharks are mentioned as preyed by killer
whales.
Eagle sting-ray, Myliabatis teeth plates were the only remain found in thestomach of a killer whale stranded on the beach of Rio Grande do Sul, Brazil.
As in the case of sharks that prey on sting-rays, six broken stings were foundembedded on the jaw and snout tegument. By comparison of the teeth plates,
the total length of the Myliobatis rays was estimated in a range of 65 to 81 ems.
INTRODUCTION

During the first week of November 1976 a killer whale, Orcinus area was stranded
3 km South of Lagoa dos Peixes bar and 120 km North of Rio Grande (R.S.,
Brasil). During the last week of December two trips were made by the staff of theMuseu Oceanografico to the stranding place. During the first trip color slides
were obtained and the possibility of retrieving a part of the_ skeleton was considered. On the second trip, the complete head and the left flipper (M.0.R.G.
Cetacean coll. n° 37) were collected, some measurements were taken and the stomach content was preserved and identified.
The 5.60 m long male killer whale was almost dried and partially hurried insand above the high tide line. Through a left lateral cut the liver was reachedand under it the stomach was found. Numerous ray teeth, one cartilage, a broken shell and sand were retrieved.
STOMACH CONTENT

The teeth were identified as belonging to the eagle sting-ray, Myliobatis, a common venomous ray of the SW Atlantic waters and abundant during the summer
along Rio Grande do Sul coasts.

* Contribution of the Base Oceanografica Atlantica n° 1
Sci. Rep. Whales Res. Inst.,
No. 29, 1977, 107-111.

108

CASTELLO

Teeth plates and venomous spines of the Whip rays, Dasyatis; Butterfly rays,
Gymnura; Cow-nosed rays, Rhinoptera and Eagle rays, Myliobatis were dissected forcomparison with those obtained from the stomach content.
Two kind of Myliobatis teeth could easily be recognized, long rectangular ones
with slightly curved edges placed at the middle of the teeth plate and small polygonal ones on both sides of the middle series.
VENOMOUS STINGS
The killer whale was carefully inspected. The tegument had been loosing oil andwas partially dried. All injuries and scars were opened with scalpels and 6 piecesof broken venomous stings were easily seen and extracted from inside the tegument
at the following places:
sting A: 3.5 cm long at 10.5 cm distance, sligthly to the left of the tip ofsnout, upper jaw
sting B: 1.9 cm long at 4.0 cm distance below the 3rd upper right tooth,lower jaw
sting C: 4.3 cm long at 8.0 cm distance below the 8th lower tooth, lower
jaw
sting D: 1.0 cm long at 4.5 cm distance below the 4th lower tooth, lower jaw
sting E: 2.0 cm long at 9.0 cm distance below the 5th upper tooth, upper jaw
sting F: 2.0 cm long at 13.0 cm distamce from the tip of snout, lower jaw
KILLER WHALE FOOD HABITS
The killer whale of the West coast of North America feed on a variety of foods,
including four main kinds: sea mammals (whales, dolphins, seals and sea otters);
sea birds; fishes (ling cod, Ophiodon; salmon, Oncorhynchus) and squids (Scheffer andSlipp, 1948).
The different preys of Orcinus orca had been carefully listed, including 10
species of cetaceans, 8 pinnipeds, 11 teleosts, 6 other vertebrates and 3 varieties ofelasmobranchs (Martinez and Klinghammer, 1969).
It has been reported that a killer whale was observed to be feeding on an electric ray, Torpedo californica (Norris and Prescott, 1961) while unidentified skates andsharks are also mentioned among their diet (Tomilin, 1967).
The killer whales from the coastal waters of Japan feed mostly on fishes andcephalopods, but also feed on large numbers of cetaceans and pinnipeds (Nishiwaki
and Handa, 1958).
The stomach content of 10 killer whales studied in the Eastern North Pacificcontained the remains of at least three California sea lions (Zalophus californianus;
four Steller sea lions (Eumetopias jubatus); seven Elephant seals (Mirounga angustirostris; two harbor porpoises (PhocOena phocoena); two Dall porpoises (Phocoenoides
dalli); one minke whale (Balaenoptera acutorostrata); two Opah fishes (Lampris regius);
one Pacific halibut (Hippoglossus stenolepus); two carcharinid sharks and one squidSci. Rep, Whales Res. Inst.,
No. 29, 1977.

FOOD OF A KILLER WHALE

109(Rice, 1968).
The leatherback sea turtle, Dermochelys coriacea, has been added to the known
prey of the killer whale from the St. Vincent Island (Lesser Antilles) (Caldwell
and Caldwell, 1969).
DISCUSSION

Orcinus area has been recently included on the list of Rio Grande do Sul cetaceanson the base of eight stranding records (Castello and Gianuca, in press).
The stranding of November 1976 (8th. record) took place along one of thelongest sandy beaches of the SW Atlantic coast (from Chui to Torres), where sea
lions Otaria jlavescens and fur seals, Arctocephalus australis are seldom seen.
The La Plata dolphin or " Franciscana ", Pontoporia blainvillei has been considered as a possible prey of killer whales at Punta del Diablo (Dto. de Rocha,
Uruguay) waters (Brownell, 1975), but until now this has not been documented.
It is also known that sharks frequently prey upon sting-rays. Dr Perry Gilbert (1977) from Mote Marine Laboratory, Florida, USA. recalled removing 96
sting ray spines from the mouth and lips of a 4.20 m long Hammerhead shark,
Sphyrna mokarran. The spines were from the common sting ray, Dasyatis americana
and the little round sting ray, Urolophus jamaicensis. Also from the jaws and neckregion of a Hammerhead shark, Sphyrna z:ygaena (3.70 m long) caught in Beaufort
North Carolina, USA., 58 stings were dissected. In a second specimen, there were
remnants of 17 caudal spines in the stomach and at least 24 spines were in thegums. Stings can also be observed embedded in the tissues covering the jaw ofCarcharinus limbatus (13 stings) and of the Sharp-nosed shark, Scoliodon terra-novae(one sting) (Gudger, 1946).
A Black-tip shark, Carcharinus limbatus from North Carolina waters (3.0 m
long and 192 kg of weight) contained pieces of the Small Devil-fish, Mobula and in
three Tiger sharks, Galeocerdo tigrinus pieces of Mobula and Whip ray (Dasyatidae)
were found (Bell and Nichols, 1921). A Whip ray spine was imbedded in themuscle at the corner of the mouth of a 1.8. m long Carcharhinus commersonni collected
at the Bay of Forida (Nichols, 1917).
From the size and number of teeth plates recovered from the stomach content
and the size and number of the stings embedded on the jaw and snout of the killer
whale, six eagle sting rays, in a range of 65-81 cm of total lenght, were eaten.
Two species of eagle sting rays are mentioned for Rio Grande do Sul waters,
Myliobatis freminvillei and M. goodei (Bigelow and Schroeder, 1953 ). Unfortunately
I am not able by the moment to distinguish both species on the basis of teeth orstings.
A broken shell of the bivalve, Pitar rostratus (Koch, 1844) also found in thestomach content was probably eaten by one of the eagle rays.
When caught in the killer whale's mouth each ray had in defense lashed out
with its long tail and at least 6 of them had left with the killer whale mementos of
their fights. Apparently no vital organ was injured by any of the stings.
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

CASTELLOllO

ACKNOWLEDGMENTS

To my friend, Prof. Norton M. Gianuca, Director of the Base Oceanografica Atlantica who identified the killer whale carcass and also to Miss Rosangela Lessa and
Mr. Lauro Barcellos and Mr. Rodney Nascimento who collaborated in taking measurements, color slides and helped to collect the head and flipper on the beach.
To Dr. Eliezer Rios, Director of the Museu Oceanografico who determined thebivalve shell and to Dr. Perry Gilbert; Dr. George Y. Harry, Director of the
Marine Mammal Division, N.O.A.A., Seattle, Washington and Dr. James W.
Atz from The American Museum of Natural History, New York, USA. who kindly
helped me with bibliography and information.
REFERENCES
BELL, J.C., and J. T. NICHOLS, 1921. Notes on the food of Carolina Sharks. Copeia, 92: 17-20.
BIGELOW, H. B., and W. C. SCHROEDER, 1953. Sawfishes, Guitarfishes, Skates, Rays. Mem. Sears
Found. Mar. Res.. I, part 2: 1-514.
BROWNELL, R. L., 1975. Progress Report on the biology of the Franciscana dolphin, Pontoporia blainvillei,
in Uruguayan waters. J. Fish. Res. Ed. Canada, 32 (7): 1073-1078.
CALDWELL, D. L., and M. C. CALDWELL, 1969. Addition of the Leather back sea turtle to the known preyof the killer whale, Orcinus orca. J. Mamm., 50 (3) : 636.
CASTELLO, H.P., and N. M. GIANUCA, (in press). Contribution to the study of the Cetacean fauna of Rio
Grande do Sul, Brasil. Atlantica, F.U.R.G. (Rio Grande).
GILBERT, P., 1977. Personal communication.
GUDGER, E.W., 1946. Does the sting ray strike and poison fish(!s? Sci. Montly 63 (2): 110-116.
MARTINEZ, D. R., and E. KLINGHAMMER, 1969. The behavior of the whale, Orcinus orca ; a review of theliterature.
Tierpsychol., 27: 828-839.
NORRIS, K. S., and J. H. PRESCOTT, 1961. Observations on Pacific cetaceans of Californian and Mexican ,waters. Univ. Calif. Publ. Zool., 63: 291-402.
NICHOLS, J. T., 1917. Ichthyological notes from a cruise off Southwest Florida, with description of Gobiesox
yuma, sp. nov. Bull. Amer. Mus. Nat. Hist., 37: 873-877.
NrsHIWAKI, M., and C. HANDA, 1958. Killer whales caught in the coastal waters of.Japan for recent ten
years. Sci. Rep. Whales Res. Inst., 13: 85-96.
RrcE, D. W., 1968. Stomach contents and feeding behavior of killer whales in the Eastern North Pacific.
Norsk Hvalfangst-Tid., 2 : 35-38.
SCHEFFER, V. B., and J. W. SLIPP, 1948. The whales and dolphins of Washington State with a key to thecetaceans of the west coast of North America. The Amer. Mir/land Nat., 39 (2): 257-337.
ToMILIN, A. G., 1967. Mammals of the U.S.S.R. and alijacent countries. vol IX. Cetacea. Israel Program for
Scientific Translations, Jerusalem, 717 p.

z.

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

FOOD OF A KILLER WHALE

EXPLANATION OF PLATE
PLATE I
Fig. I. Left middle series teeth of the upper plate (n° 1) of an eagle sting-ray,
Myliobatis estimated to be 81.5 cm long, eaten by the killer whale. Right-Lower
plate of the same specimen.
Fig. 2. Eagle ray teeth in different positions, three first rows are middle teeth,
fourth row are lateral ones.
PLATE II
Fig. I. Dorsal aspect of the lower teeth plate (n° 3) of an eagle sting-ray eaten by
the killer whale.
Fig. 2. Ventral aspect,
PLATE III
Fig. I. Labial cartilage of an eagle-sting ray found in the stomach content.
Fig. 2. Rests of a Pitar rostratus bivalve shell, probably eaten by one of the stingrays.
PLATE IV
Six pieces of eagle ray stings that were embedded on the jaw and snout of the killer
whale.

Sci. Rep, Whales Res. Inst.,
No. 29, 1977.

111

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HUMAN ACTIVITIES DISTURBING NATURALMIGRATION ROUTES OF WHALES*MASAHARU NISHIWAKI
Department of Marine Science, University of the Ryukyu, Okinawa

AND
AKINOBU SASAO
Ocean Research Institute, University of Tokyo, Tokyo

ABSTRACT

Trying to prove human activities which disturbed natural migration routesof whales, two populations of whales were investigated.
In Tokyo Bay area, annual catch numbers of the Baird's beaked whale(Berardius bairdii) in Boso whaling ground are between 50-300. Although
the whales have shown no sign of average body length decrease, (Nishiwaki
and Oguro 1971 ), apparent decrease of whales caught inspite of increasing CatchPer Unit Effort makes us no other way, accept the fact that the maritime
transportation disturbed the migration routes of whales of this stock.
Same is true in the northern coast of Kyushyu. Reason of catch decrinein the present investigation can not be considered as damage to the minke
whale (Balaenoptera acutorostrata) stock caused by whaling. Catch Per Unit
Effort is, as a whole, in an up surging, but the number of whales caught is decreasing without average body length decrease.
Great number of vessels are coming into and going out of the both areas
and the number is still increasing. Not only those whales, but also various
species of marine mammals may be troubled by the busy traffic. The result of
this investigation would be a warning to the countless activities by men,which disturb or expel wild animals from their natural inhabiting ground andmigration routes everywhere in our environment.
INTRODUCTION

Handreds of years ago, when human population was moderate and people did not
try to catch whales, many species of big whales which by nature favored to breedin temperate or warmer waters, may have entered into lagoons and inlets of Japan.
Evidences of half fossilized whale skeletons have been found at many places along
the coast of the Inland Sea, in the western K yushyu Island and even on the coastof Tokyo Bay. At present, however, there are very few sighting reports of big* This report was submitted to FAO/ACMRR/MMWP and taken up as No. 124 by the Scientific Consultation on the Conservation and Management of Marine Mammals and their Environment, Bergen, 1976
and published in the Scientific Report of Whales Research Institute .because publishment of the Proceedingsof the above conference is later than that of WRI, and earlier publishment was desired.
Sci. Rep. Whales Res. Inst.,
No. 29, 1977, 113-120.

114

NISHIWAKI AND SASAO

whales in those areas.
In 1969, a stray calf of the bowhead whale came into Osaka Bay and was accidentally caught by local fishermen (Nishiwaki and Kasuya 1970). The incident
was a proof of the natural preference of this species which had favored the temperate waters of the Inland Sea.
At Scammon's Lagoon, Baja California, gray whales had come abundantly tobreed in former days. However, when the rumour of this phenomenon spreadamong people, not only scientists but also a large number of general people
gathered to see the whales. Disturbed by the sightseers, it was reported, that the
number of whales coming to the lagoon had apparently decreased. The incident
was one of disturbances, not by whaling activities, but by another human action
affected the whales.
Trying to prove human activities which disturbed natural migration routes ofwhales, we investigated the two populations of whales, the Baird's beaked whale(Berardius bairdii) in Boso whaling ground and the minke whale (Balaenoptera acutorostrata) in Yobiko whaling ground, both of which did not receive a serious damage
by whaling, but affected by the increasing number of ships and boats coming inand out or passing near by the whaling grounds (there are very few whale population which have received no harm from whaling).
INFLUENCES OF VESSELS OVER THE BAIRD'S BEAKEDWHALES IN BOSO WHALING GROUND

Baird's beaked whale catch has been operated from land stations in certain limitedareas of Japan. One of such whaling grounds is Boso ground in Chiba Pref. The
ground is only 20 miles distant from the mouth of Tokyo Bay. Coast of Tokyo
Bay is dotted with commercial, naval and fisheries' ports. As shown in Fig. 1, there
140°E

142°E

JAPAN

36°N

PACIFIC
OCEAN
34°N

32°N
142°E

Fig. I. Boso whaling ground and the main course of vessels in and out of TokyoBay.

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

HUMAN ACTIVITIES DISTURBING WHALESTABLE I.

ANNUAL NUMBER OF VESSELS ENTERED THE PORTS
Tokyo Bay Area

Northern coast of Kyushyu

Year
Tokyo

1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974

11941
11301
13797
13913
12625
13957
15038
15116
12066
20649
22813
27360
31776
32767
31358
33936
45886
53381
57356
64502
68894
70158
78816
76586
79763
81689
72222

115

Yokohama Yokosuka

5870
12507
14723
16262
21093
20009
17118
22953
26737
28384
30573
37120
45121
45644
50649
60078
71087
76039
88238
99691
106721108427104742101537102946
93987

3521
1768
3228
3806
6220
7182
8337
8101
9156
10063
12408
14690
16085
16206
16114
16223
19136
24719
27880
26404
24556
27549
28243
28632
26225
27673

Chiba

3744
6306
4155
6708
9479
11198
9942
18513
31237
32241
33500
39480
35336
60065
73713
72098
77347
87185
80827

Dokai Area Kokura

41756
37132
58467
47441
42926
49788
72641
10391
72450
75743
63310
65657
70136
71648
69944
67224
76418
76544
68172
64064
58037

15330
14108
12849
30427
29211
28211
28192
18858
29398
27165
27394
29265
28117
28354
29952
28792
30013
26424
23450
25034
25994

Moji

Shimonoseki

17738
34839
33884
13156
40612
47807
44655
43447
27857
27564
43600
42820
45100
77778
66141
65720
62430
55807
65530
84363
62448

5199
11478
90886
11333290239
96694
100046
56812
42382
47460
80323
77185
78151
75664
77257
77317
75909
74237
72665
71059
73913
65317
64124
65993
71576
69319
66845

are Tokyo, Kawasaki, Yokohama, Yokosuka, Chiba, Kisarazu, Uraga and Kurihama Ports. Various ships and boats which are coming into those ports, mustenter the mouth of Tokyo Bay. A list of a great number of vessels of over 5 tons isshown by the year in Table 1. Moreover, all boats which once enter into the Bay,
must inevitably go out. So, the number of boats must be considered as twice asmuch to become an amazingly big number. Although it was difficult to get datafrom every port of Tokyo Bay area, general circumstances of maritime transportation around the Bay might be understood with this table. Actual number of theboats was, of course, much more than the indicated number. In the year when
100 whales were caught, the number of boats coming into Tokyo Bay was about
250,000. That is, one boat per minute was passing through the mouth of the Bay.
In Fig. 2, annual number of vessels entered into Tokyo Bay is compared withthat of Baird's beaked whales caught at Boso whaling ground since 1948 till 1974.
These numbers are averages of every three years. This method makes the curves
smoother and the curves show the tendencies more clearly.
As it is also indicated in Fig. 2, CPUE (Catch Per Unit Effort) has been increasing in the years. The reason of the remarkable increase of CPUE between
Sci. Rep. Whales Res. Inst.,

No. 29, 1977.

116

NISHIWAKI AND SASAO
300,000.5'O.,,...
~.,,

15

300

f".,

I

.,,...

0

i

0.

j:i

200,000

"'""

::>
u

~
u

:fl

!

"

. ,,

i

10 g 200

]

.'G.

'

.i i

5 0100
~·

....

"'·'~

,:;,.'v......
•<'.,;:x.•·····X•·-··-•X'"

0

t

0

1949

1952

1955

1958
Year

1961

1964

1967·

1970

1973

Fig. 2. Annual number of vessels entered into Tokyo Bay compared with that of
Baird's beaked whales caught from Boso whaling ground.

1961 and 1964 was that, small tonnaged (15-20 tons) catchers were abolished andbigger (30-50 tons) catchers were taken up for operation. Accordingly, numberof catchers decreased, instead, capability per boat increased. Nevertheless, thepopulation seems to have shown no sign of receiving damages during the 25
years, although biological examination on those whales caught has not been done
every years. Annual catch numbers are between 50-300. The numbers arerather small, but the whales have shown no sign of average body length decrease(Nishiwaki and Oguro 1971). Considered the increasing CPUE and apparent
decrease of whales caught without population damage, we have no other way,
accept this phenomenon as a fact that the maritime transportations have disturbed the migration routes of the Baird's beaked whale.
MINKE WHALES IN YOBIKO WHALING GROUND AND MARITIME
TRAFFIC ON THE NORTHERN COAST OF KYUSHYUIn the northern part of Kyushyu Island, local people have had a habit of eating
whale meat since more than four hundred years ago. Among the species of whales
coming near to the coast, minke whales are relatively fearless and even coming into
set net to be an easy harvest for fishermen. The meat of minke whale was a very
important protein resources at the time of devastation just after World War II:
minke whale meat was a necessary food in northern Kyushyu and consumed abundantly. Whaling on minke whale is usually done by small boats of 15-20 tons
with 35-50 mm harpoon guns. The whaling ground is naturally limited within
30 miles from the shore (Fig. 3).
Fortunately, the record of the body length of minke whales caught in this area
since 1948 has been kept to date, and was very important reference to our investigation. It was very difficult to grasp a number of vessels coming in and out of all
the ports in Northern Kyushyu. As main transportations of this area, numberof vessels coming into Dokai district (Yahata, Wakamatsu and Tobata), Kokura,
Moji and Shimonoseki Ports, were investigated. Fig. 4 shows a relation between
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

HUMAN ACTIVITIES DISTURBING WHALES

129'E

36'N

131'E

SEA
OF
JAPAN

REPUBLIC

OF
KOREA

35'N

34'N

33'N

33'N

131'E

Fig. 3. Yobiko whaling ground and ports of Northern Kyushyu on the coast of
Korean Strait.
ti

250,000£

200,000

"'u0

100

.

\
50,000 iil

§

/

/

•\,...- ....!

P-'""'\_.,/I"-·-et""· \

\.
\

\,
z QiL-1~94-8~'-...---1~95-0~~-19~5-2--'~l-9~54~-'--1~9~56~-'---1~95-8~'---1~96-0

0 ~

Year

Fig. 4. Relation between the incresing number of vessels and that of the decreasing
whales caught in Yobiko whaling ground since 1948 till 1957.
Sci. Rep. Whales Res. Inst.,

No. 29, 1977.

117

118

NISHIWAKI AND SASAO

the increasing number of vessels and the decreasing number of minke whalescaught in Yobiko whaling ground. Similar number to that in Tokyo Bay, 250,000
vessels came to those ports in the most prosperous years. In Fig. 4, actual numbers of whales caught are used, not averages of every three years. So, the curves
are not so smooth as those in Fig. 2, but the tendency of traffic and catch number
might be recognized.

JO

Number of whales caught by year
lOO .--"r20-'Tl5,_,lr-O'f-5-¥-0-415""-'l!'-O'f-5-'i-0--'l'i'-O+5-¥0~1T-O_,,_5-¥0_1'+0-¥5--iOi-'lT-5¥10-T5'-'0f--¥10_,5~0r--""1'10--i5,_0J-_.,10~5,_0J-~5f-10

31
29
28

27
25

t:0

fil
~24 13
~

<:23

§

'§

~ "&5

-~

7,;"' 20 ~0

=f21 "'
u

't:J

50

~

"'u "'u"' c;;"'~..c:: 19 ~~ "O ..c::"' ·..c::~ ;;: ;;:OJ";:'.,11
't:J
0

.0

.8 15
~

OJ

]16 "O"O...OJ ...OJOJ""..."'

.0

.0

§
z" z
E

OJ

~ 13 ~

t i f
14

0

0

1952
Year

1954

1956

Fig. 5. Annual number of whales caught, its body length distribution and average
body length with CPUE in Yobiko landstation during the period 1948-1957.

We would like to discuss at this point whether that decline of catch in Yobiko
was caused by whaling damage on the minke whale stock. Fig. 5 shows the annual size distribution, average body length and number of whales caught with
CPUE since 1948 till 1957. The data of whales caught were exclusively bodylength without physiological records such as maturity or pregnancy. The numberof whales caught were rather small in most years, especially in 1957. Very little
can be presumed only from size distribution of each year. However, if the size
distribution of all whales caught during the ten years period is observed collectively, whales can be divided into groups. Each peaks of size distribution appears at
the body lengths 15, 18-20 and 23-24 feet respectively. These peaks are considered to be groups of yearings, the one to two years old and the older than three
years. At that time, minke whale whaling in Japan was not restricted by regulations. So1 females and calves were caught together. But in later years of theperiod, number of yearings became smaller: disturbed frequently by increasing
maritime transportations, mothers with calves must have detoured the coast of
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

119

HUMAN ACTIVITIES DISTURBING WHALES

northern Kyushyu.
Record in 1947 is unknown. In 1948, 93 individuals were caught. Then
Korean War broke out in 1950. Number of vessels coming to Northern Kyushyu
in 1950 was triple times as much as the number in 1949. The least catch in 1950
was not because exclusively of disturbing maritime traffic, but also of various industrial reasons, including munitional boom. In other words, wages from suchindustries became more profittable than those from whaling, so whalers switched to other employments in those years. Conditions were similar in 1951 and1952. In 1953, the war stopped and the munitional boom gradually ceased.
However, number of vessels showed little decrease. Whalers of the ground saw
unstable status of their whaling desperately and wanted to move to some other district. One catcher boat moved to Ushizu, Ishikawa Pref. in 1950 and caught fiveminke whales (average body length of them was 20 feet), then other two followed
in 1951 and caught 25 individuals (average body length of them was 23.3 feet).
In 1956, one whaling boat of Yobiko made an expedition to southern islands of
Kyushyu as far as Naze, Amami-Oshima and caught 19 individuals (average bodylength of them was 25.0 feet). Finally whalers of Yobiko whaling ground gave up
the entire ground and all except one moved to the far northern district, Wakasa
Bay, Fukui Pref. And though remained one worked, caught only two individuals
in the following year. Then Yobiko whaling was ceased at all.
TABLE 2. ANNUAL NUMBER OF CATCHER-BOATS, WHALES CAUGHT WITH
AVERAGE BODY LENGTH AND CPUE IN YOBIKO WHALING GROUND
Year

1948

1949

1950

Number of catchers
Number of whales caught
Average body length in feet
CPUE

10
93
17.8
8.5

7
39
17.0
5.6

5
17
17.7
3.4

1951
5
20
20.0
4.0

1952
6
43
19.3
7.2

1953

1954

6
43
20.1
7.2

6
31
20.5
5.2

1955
5
28
21. 7
5.6

1956
6
37
20. 7
6.2

1957
2
18.0
2.0

Again, reason of the catch decline can not be considered as damages caused
by whaling to the whale stock. As it can be understood from Fig. 5, though
CPUE has been flactuated by the years, as a whole, it was in an up surging, but
average body length of the population showed no sign of decrease, or even showedmcrease. We would like to introduce here a letter from Mr. S. L. Bowen addressedto the senior auther written on 18th April, 1972. He was then an army soldierdispatched to Korea. He had had interest in the gray whale and its status andconditions. He told Nishiwaki that in 1970, total number of whales caught fromthe whaling ground adjacent to Ulsan was 740, among them, 715 were minke
whales. It may be safe to presume that the stock of minke whales there was identical population to the Y obiko stock. Distance between the two grounds is little
more than 100 miles. If the number which Mr. Bowen indicated, is right, cause of
Yobiko whaling decline (they caught, at most, 100 a year since 1948 till 1957) was
not by damages on the minke whale stock by whaling activities. At present,minke whale whaling can not be operated in the Y obiko whaling ground, eastern
Sci. Rep. Whales Res. Inst.,

No. 29, 1977.

120

NISHIWAKI AND SASAO

channel of the Korean Strait, but is still prosperous in the Ulsan whaling ground,
the western channel of the Korean Strait. Considered the experience in Yobiko
whaling ground, one can hardly deny influences of maritime traffic to the minke
whales. As great number of vessels which belonged or connected to the Northern
Kyushyu Industrial Zone, in which Moji, Tobata, Yahata, Karatsu, Sasebo andNagasaki, biggest ports of Japan, are included, are coming in and going out andthe number is still increasing, various other species of marine mammals may betroubled similarly by the busy traffic.
CONCLUSION

Naturally, there might have been other additional factors of influences which affected the whale populations to some extent. But, at least, result of the present
investigation shows apparent disturbances by ships and boats to the migrationroutes of Baird's beaked whales in Boso whaling ground and minke whales in
Yobiko whaling ground.
The result of this investigation would be a warning to the countless activities
by men, which disturb or expel wild animals from natural inhabiting grounds andmigration routes everywhere in our environment. As well as aerial and landtransportations, maritime traffic is another environmental problem. Damages bywhaling has been so controvercial in recent years, but those by maritime traffic
tends to be overlooked. From the view point of ecosystem, maritime influences
to animals are not small, but little countermeasures to those have been taken up
till now.
REFERENCES
BOWEN, S. L., 1972. Personal communication.
CHIBA PREFECTURAL OFFICE, 1948-1974. "Chibaken Tokei Shiryo" (Statistical Data of Chiba Prefecture)(in Japanese).
DEPARTMENT of RESEARCH and DATA PROCESSING, MINISTRY of TRANSPORTATION, GOVERNMENT of JAPAN,
1948-1974. "Nippon-Koku Kowan Tokei" (Harbor Statistics of Japan) (in Japanese).
KANAGAWA PREFECTURAL OFFICE, 1948-1974. "Kanagawaken Tokei Shiryo" (Statistical Data of Kanagawa Prefecture) (in Japanese).
NISHIWAKI, M. and T. KASUYA, 1970. A Greenland right whale caught at Osaka Bay. Sci. Rep. Whales Res.
Inst., 22 : 45-62.
NISHIWAKI, M. and N. 0GURO, 1971. Baird's beaked whales caught on the coast of Japan in recent 10 years.
Sci. Rep. Whales Res. Inst., 23 : 111-22.
STATISTICS DIVISION, MINISTRY of AGRICULTURE and FORESTRY, GOVERNMENT of JAPAN. Agriculture, Forestry
and Fishery Statistics Data 1948-1974. Association of Agriculture and Forest Industries.

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

ON THE FORMATION AND REGRESSION OF CORPUS
LUTEUM IN THE NORTHERN FUR SEAL OVARIESKAZUMOTO YOSHIDA, NORIHISA BABA
Far Seas Fisheries Research Laboratory, Shimizu

MACHIKO OYA AND KAZUHIRO MIZUE
Ocean Research Institute, University of Tokyo, Tokyo

ABSTRACT

Corpus luteum and the process of its formation in fur seal ovary, collectedaround the Robben Island in the Okhotsk Sea, were studied. The regressive
phases of follicle and courpus luteum were examined histologically. There are
two kinds of corpus luteum, one is formed inside the vesicular follicle after
ovulation, the other is formed outside the follicle without ovulation. The
former is the true corpus luteum and the latter is the accessory corpus luteum
or corpus atreticum. The function of corpus luteum graviditatis degenerates in
the last stage of pregnancy. Corpus albicans originated from the true corpus
luteum is distinguished from the corpus atreticum clearly. The former exists
for about two years in the ovary and then disappears, but the latter vanishes
shortly.

INTRODUCTION

There are many informations about the mammalian ovaries including human race.
Since the fur seal is a kind of marine mammal but goes ashore during some months
once a year for reproduction, its sexual cycle, age and growth were made clear byvarious authors. But microanatomical studies of the reproductive tracts are stillrather scanty. Craig (1964), Enders et al. (1946), and Pearson and Enders (1951)
report ovarian cycle for seals taken in the eastern Pacific and on the Pribilof Islands
respectively. However, there is no report on the microanalisis of reproductive organs on the Robben and Commander fur seals.
In the field observation of fur seals for the purpose of the stock assessment,
numbers of corpus luteum and corpus albicans are counted, but the disappearing
process of corpus luteum and corpus albicans can not be followed sufficiently by
this method and further the corpus albicans can not be identified from corpus atreticum by macroscopical observation. The disappearing processes of corpus luteum and corpus albicans were not treated sufficiently in the aforesaid reports.
We report in this paper on the corporal cycle in the fur seal ovaries taken in
the seas around Robben Island between July and October 1975.

Sci. Rep. Whales Res. Inst.,

No. 29, 1977, 121-128.

YOSHIDA, BABA, OYA AND MIZUE122

MATERIAL AND METHODThe Fur Seal Section of the Far Seas Fisheries Research Laboratory, JapaneseFisheries Agency, took fur seals in the seas around Robben Island in 1975 for the
purpose of stock assessment and their reproductive tracts were preserved in 10%
formalin after field biological investigation. We have sampled randomly 11 7 pairsof ovaries from these, which consisted of ovaries from 11 immature females, 11
ovulated females for the first time this year, 29 nonpregnant females but ovulated
in preceding breeding season, 23 ovulated females this year but non-ovulated inpreceding breeding season, and 43 pregnant females. These ovaries were weighed
their weight, then sliced to the thickness of about 2 mm, and measured the diameter of corpus luteum in three dimensions, counted the number of corpus albicans,and measured the diameter of the largest Graafian folicle. And then all ovaries
were further sliced into thin sections, embedded in paraffin, and these sections were
stained by compound stain method of Mayer's haematoxylin and eosin, and thenobserved. Age of these fur seals was determined by annual rings in the upper andlower cuspids.
OBSERVATION AND RESULT(1)

Regression offollicle

Section of the pup ovary of about three months after birth is indicated in Plate I-1
which contains many small follicles. Very few follicles among them develop tolarge size and finally ovulated, but many other follicles would be regressed, because it can be seen that there are many corpora atretica and follicles in process of degeneration and contraction. Plate I-2 shows ovary of 2 years of age, immature female, which contains many large follicles and this specimen was collectedin the middle of October. In this investigation mature females had no large follicle in the ovaries at this time of the season, owing to their functional corpus luteum, but in the ovaries of immature females, a number of comparatively large follicles are present, due to the fact that they have no functional corpus. Plate I-3
shows matured ovary of 14 years of age. A functional corpus Iuteum caused byovulation of this reproductive season exist in this section. Since this specimen wascollected towards the end of July, it is not clear whether this is corpus luteum graviditatis or corpus luteum of without gravidity. (Craig, 1964; Enders et al., 1946;
Pearson' and Enders, 1951). In addition there are corpus albicans and corpora
atretica resulted from Graafian follicles in this figure.
Enlarged follicle figure in the process of regression existed in pup ovary of
Plate I-1 is shown in Plate I-4. Oocyte is actualized in this figure but stratum
granulosum begins to degenerate, and in antrum folliculi, a sort of phagocyte
which is usefull for exhaustion are observed in abundance, and the basement membrane transformed to glassy membrane by distortion and increase of thickness.
The former term of vesicular follicle in the progress of development which is similar
to that of the other mammals is shown in Plate II-1. Contraction of the vesicularSci. Rep. Whales Res. Inst.,
No. 29, 1977.

123

CORPUS LUTEUM OF FUR SEAL

follicle, the stratum granulosum degeneration in the first place, and then in oocyte
are shown in Plate II-2. In corpus atreticum distortion has occurred and thickened glassy membrane, and in Plate II-3, there are no oocyte and stratum granulosum. This corpus atreticum existed abundantly in ovary and it can be distinguished from corpus albicans resulted from corpus luteum distinctly and it seems
that these corpora atretica vanishes rapidly.
The figure of large vesicular follicle which contracted already is shown in
Plate II-4. The glassy membrane in this figure thicken increasingly than theformer, but it is the same in fundamental structure as corpus atreticum.

(2)

Corpus luteum and its degeneration
The aspect just ruptured to release an ovum from a ripened vesicular follicle
is shown in Plate III- I. In this figure, liquor folliculi and blood are still exist in
antrum folliculi, stratum granulosum along interna of theca folliculi increases the
thickness exceedingly and follicular epithelial cells formed stratum granulosum begin to expand and change to lutein cell in the enlarged figure. It is thought that
fur seal corpus luteum is originated mainly from the cells of stratum granulosumand not from theca interna of folliculi.
TABLE I. CORPUS LUTEUM DIAMETERS IN mm
AFTER OVULATION BY MONTHS

July
AugustSeptember
October

Vertical diameter

Lateral diameter

Height

8.0
10.0
11.3
14.0

7.4
8.7
10.4
12.7

8.5
9. 7

10.5
13.5

The corpus luteum resulted from an ovulation about two months before isshown in Plate III-2, a specimen from mid September. In the fur seal corpus
luteum is contained within the ovary like in many other mammals, though inwhales it is usually protruded from the ovary. Other corpus luteum constituted
around the outside of vesicular follicle, beside formal corpus luteum, is observed in
Plate III-2. Such corpus luteum is not rare in fur seal ovary, like in ovaries ofwhales (Harrison et al. 1972). It seems that the lutein cells of such corpus luteum
are originated from theca follicular cells and perform the same function as formal
one besides suppressing the development of its inside follicle. The lutein cells informal corpus luteum resulted from an ovulation of about three months before areenlarged in Plate IIl-3, a specimen from mid October. This figure shows the mostactive appearance of lutein cells and there are many secretions in the protoplasm ofthese cells and around them. The lutein cells in corpus luteum formed aroundvesicular follicle show the same histological appearance in this season too.
In Table I corpus luteum measurements in three dimensions are arranged in
the order from July to October. The corpus luteum which was formed in earlySci. Rep. Whales Res. Inst.,
No. 29, 1977.

124

YOSHIDA, BABA, OYA AND MIZUE

July by ovulation increases its size during the progress of month and increases its
function gradually, as shown in Table 1 clearly. And no difference in the size of
corpus luteum by ages, from three to twenty years, is noted.
After fur seals went ashore for reproduction and delivered a calf, the ovulation
is taken place within one week. Consequently it might be necessary that the regression of the lutein cells should begin towards the latter of the pregnancy. Craig(1964) describes that the corpus luteum graviditatis of the fur seal in the eastern
Pacific is functional until February and begins to degenerate after that. His description agrees with ours. The histological figure of corpus luteum graviditatisof pregnant animal prior to delivery caught on 10 July is indicated in Plate III-4.
In this figure lutein cells are almost degraded or fallen off and remains are small andnot in complete phase. It is distinct that the aspect of this corpus luteum graviditatis does not perform the secretion, unlikely from the lutein cells in Plate III-3,
and has the connective tissue penetrating into the structure of corpus luteum arborescently. As we have only specimens for four months, from July to October,we can not conclude definitly about the cycle of corpus luteum, but it is thoughtthat the same pattern of corporal cycle of Robben seal, as reported by Craig(1964), would be followed by the eastern Pacific stock of the fur seal.
Table 2 shows the process of regression of the corpus luteum graviditatis, indiameters in three dimensions, from just before delivery to after birth. In spite of
TABLE 2. THE AVERAGE DIAMETER OF CORPUS LUTEUM
IN mm BEFORE AND AFTER PARTURITION

Corpus luteum just before parturition
Corpus luteum after parturition(corpus albicans)

July
AugustSeptember
October

Verticaldiameter

LateraldiameterHeight

18.9
11.2
10.6
8.7
8.6

14.2
10.4
8.7
8.5
7.3

15.5
13.0
10.9
8.9
8.5

the unfunctional lutein cells, the size of this corpus luteum is larger than thatshown in Table 1, so it is concluded that the corpus luteum enlarges continuously
since ovulation. Fur seal fertilized ovum remains free in the lumen of uterine
horns and does not implant for about four months and placentation is establishedafter implantation (Craig, 1964; Enders et al., 1946; Pearson and Enders, 1951).
It seems possible that this phenomenon occurs not only in fur seal but also in all
Pinniped animals (Matthews and Harrison, 1949). The corpus luteum without
pregnancy, or in the case of unfertilization or unimplantation it does not contract
rapidly, unlikely to whales, because it has enough time for contraction until next
reproductive season and contractive process is thought to be same to that of corpus
luteum graviditatis. Pearson and Enders (1951) describes that the fur seal corpus
luteum which has not accompanied by a pregnancy follows even in the latter part ofMarch same phase of corpus luteum graviditatis and this is similar to our result.
The corpus albicans originated from corpus luteum without pregnancy in theSci. Rep. Whales Res. Inst.,
No. 29, 1977.

CORPUS LUTEUM OF FUR SEAL

125

preceding breeding season, and from an animal caught in 6 August, is shown in
Plate IV-2. The size and the stage of degeneration of this corpus albicans is sameto that of Plate IV-1. From Table 2, the corpus luteum graviditatis contracts
rapidly just after whelping, but the pace of contraction become slow after that.
The corpus albicans two months later from the parturition is indicated in Plate
IV-1, in which no lutein cell is observed naturally. And this is a typical corpus
albicans originated from the true corpus luteum and it shows quite different phase,compared with the accessory corpus luteum or corpus atreticum originated fromvesicular follicle. Laws (1958) discusses about the differences between the corpus
albicans resulted from corpus luteum graviditatis and that without pregnancy inwhales, but in the fur seal, there is no difference between both corpora albicantia
from the starting points of ovulations.

Corpus albicans and its degeneration
The corpus albicans disappears within a comparatively short span of time inmost mammals, but in whales the corpus albicans persists in the ovaries throughout
the life. This is thought to be based on the fact that their ovaries are large enoughfor admiting the persistence of all corpora albicantia, but in the fur seal, the ovary
is small and has no core in the center of corpus albicans, unlikely to whales. Accordingly, the disappearing period of corpus albicans is not short in the fur seal,
compared with other mammals. It does not remain, however, in the ovary
throughout the life.
A contracted figure of corpus albicans after one year since parturition is shownin Plate IV-3. Its surrounding parts are torn to pieces and has disappeared andbecame smaller. There are many ovaries in our specimens which have such a
corpus albicans, collected from animals one year after parturition, in which twenty
percent have vanished within one year, and this rate is higher in younger animals
than older. Plate IV-4 shows corpus albicans of an animal taken two years after
partunt10n. Such an old corpus albicans which existed such long time is very seldom in the fur seal. According to our investigations, it is concluded that in the
fur seal corpus albicans vanishes within three years after ovulation, though there
are some individual variations. That is different from the finding of Pearson andEnders (1951) who describe that it disappears before the next ovulation from thesame ovary, which means that the corpus albicans disappears within one year after
parturition.
(3)

REFERENCES
CRAIG, A. M., 1964. Histology ofreproduction and the estrus cycle in the female fur seal, Callorlzinus ursinus.
]our. Firh. Res. Bd. Canada, 21(4):773-811.
ENDERS, R. K., L. P. PEARSON and A. K. PEARSON, 1946. Certain aspects of reproduction in the fur seal.
Anal. Ree., 94 (2): 213-227.
HARRISON, R.J., R. L. BROWNELL Jr. and R. C. BOICE, 1972. Reproduction and gonadal appearances insome odontocetes. Functional Anatomy of Marine Mammals, 1 : 361-429.
LAws, R. M., 1958. Age determination of whales by means of the corpora albicantia. Proc. XVth lnt.
Sci. Rep. Whales Res. Inst.,

No. 29, 1977.

126

YOSHIDA, BABA, OYA AND MIZUECongr. :(',ool., Sect. III : 303-305.
MAITHEWS, L. H., and R.J. HARISON, 1949. Subsurface crypts, oogenesis, and the corpus luteum in theovaries of seals. Nature, 164: 587-588.
PEARSON, A. K., and R. K. ENDERS, 1951. Further observations on the reproduction of the Alaskan fur
seal. Anat. Ree., 111 (4) : 695-711.

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

CORPUS LUTEUM OF FUR SEALEXPLANATION OF PLATESPLATE I
Fig. 1. X 11.4, Histological section of fur seal pup ovary after three months frombirth. Caught 11 October, 1975.
Fig. 2. x5.7, Histological section of immature fur seal ovary, two years old.
Caught 13 October, 1975.
Fig. 3. x5.7, Histological section of mature fur seal ovary, 14 years old. Caught
31 July, 1975. It contains one functional corpus luteum resulted from this ovulation, one corpus albicans originated from corpus luteum and eight corpora
atretica originated from vesicular follicle.
Fig. 4. X 380, Histological figure of small follicle in the progress of degeneration.
The same ovary of Fig. 1.
PLATE II
Fig. I. X 380, Early stage of vesicular follicle in the process of development, three
years old. Caught 3 September, 1975.
Fig. 2. X 155, Degrading vesicular follicle, five years old. Caught 15 July, 1975.
There is no stratum granulosum already and oocyte is degenerating.
Fig. 3. X 155, Corpus atreticum originated from vesicular follicle, from the same
specimen shown in Fig. 2.
Fig. 4. x51, Corpus atreticum originated from large vesicular follicle, eighteen
years old. Caught 6 August, 1975.
PLATE III
Fig. 1. X 11.4, Ovulated follicle, four years old. Caught 29 July, 1975.
Fig. 2. x5.7, Mature ovary, nineteen years old. Caught 14 September, 1975. In
this section there are two kinds of corpus luteum, one is the formal by ovulation,
the other is formed around the outside of vesicular follicle.
Fig. 3. X 760, Functional lutein cells, fourteen years old. Caught 11 October, 1975.
Fig. 4. X 155, Histological figure of corpus luteum graviditatis just before delivery.
Fourteen years old. Caught 10 July, 1975. It is in the process of degeneration.
PLATE IV
Fig. I. x51, Corpus albicans after about two months from parturition. Seven
years old. Caught 13 September, 1975.
Fig. 2. X 51, Corpus albicans not accompanied by pregnancy passed about thirteenmonths after ovulation. Eighteen years old. Caught 6 August, 1975.
Fig. 3. x51, Corpus albicans originated from corpus luteum graviditatis of about
fourteen months after parturition. Six years old. Caught 28 September, 1975.
Fig. 4. x51, Corpus albicans of about two years after parturition. Fifteen years
old. Caught 3 July, 1975.

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

127

128

YOSHIDA, BABA, OYA AND MIZUEEXPLANATION OF SYMBOLS IN PLATES
AF
Antrum folliculi
BM Basement membrane
CA
Corpus albicans
CAT Corpus atreticum
CLF Corpus luteum formed around the follicle
CO Cumulus oophorus
FC
Functional corpus luteum
GM Glassy membrane
LC
Lutein cell
LF
Liquor folliculi
N
Nucleus0
OocyteP
Protoplasm
PH
Phagocyte
S
Secretion
SG
Stratum granulosum
TA
Tunica albuginea
TF
Theca folliculi
VF
Vesicular follicle
ZP
Zona pellucida

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

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A NOTE ON THE AIR-SAC OF RIBBON SEALHISASHI ABE
Institute of Applied :(oology, Faculty of Agriculture, Hokkaido
University, Sapporo

YOSHIKAZU HASEGAWA
Section of Vertebrate Paleontology, National Science Museum, TokyAND
KAZUO WADA
Primate Research Institute, K_yoto Unii;ersity, Inuyama

ABSTRACT

Investigations on the air-sac of seals were carried out by us, using twelve
males and three females of the ribbon seal (Histriophoca fasciata ZIMERMANN) and two males of the Okhotsk harvor seal (Phoca vitulina LINNAEUS), which were caught off Rausu of the Shiretoko Peninsula, Hokkaido,
Japan, in the middle of March and April, 1966. In the rear part of the trachea of the ribbon seal, the cartilage rings are broken to form a slit, 25-46 mm
long, which leads to an air-sac on the outer side. The two ends of the broken
rings form long and slender valvular projections. The fore part of the air-sac
is developed beneath the sternomastoid muscle, and the rear part is between
the pectoralis superfacies and the costae. In adult males, the sac is large, but
it is smaller in young individuals. Young females have a pair of valvular projections but no air-sac. Even in adult females, development of the air-sac isvery poor or entirely absent. The role played by the air-sac is not known.
The cartilage rings of harbor seal are broken at the rear part of the trachea,
but the break does not form a slit and hence air-sac is not developed.

INTRODUCTION

Studies on the morphology and ecology of the ribbon seal, Histriophoca fasciata
ZIMMERMANN, have been relatively few, and even the dental formula of this animal
had been little known until recently (SCHEFFER, 1960).
The present writers have observed that the ribbon seal has an air-sac branching out of the trachea. An outline of the observation is reported here.
Valuable specimens of the ribbon seal for this study were offered by Mr.
lchitnatsu Nedefuji, Misaki-machi, Rausu-cho, Menashi-gun, Hokkaido, who also
took care of the lodging for the writers during the period of investigation. We
wish herewith to express their sincere gratitude to Mr. Nedefuji. They are alsoindebted to many persons for helpful suggestions.
Sci. Rep. Whales Res. Inst.,
No. 29, 1977, 129-135.

130

ABE, HASEGAWA AND WADA

DISCOVERY OF AIR-SAC
Two of us, Wada and Hasegawa, visited Rausu-cho from March 15 to 17, 1966 forthe purpose of investigating seals. On March 15, when a male ribbon seal, captured off Rausu by Mr. Nedefuji, was being dissected, Wada noticed a bladder-likemembranous sac in the thorax, and surmised if it might be an air-sac. On the following day, four more males and one female were captured. Hasegawa examinedthem and noted that the sac seemed to occur only in males, its position being located always on the right side of the body, and that the size of the sac was considerably variable according to individuals. However, he could not get sufficient
data on this subject as the time was limited.
Later, from April 12 to 14, Abe visited Rausu and made more precise observation of seven males and two females of H. fasciata and two males of Phoca vitulina
LINNAEUS (Okhotsk harbor seal). He examined in particular the size and position of the air-sac and the difference between male and female, as well as the relationship between the length of the body and the development of the air-sac. Later,
he cut off the tracheae attached with the sac, preserved them in alcohol, andbrought them back to the laboratory for further observation of details.
POSITION AND STRUCTURE OF AIR-SAC
1) MaleIn the first half of the trachea, the tracheal cartilage forms complete rings without
any break, whereas in the latter half, the cartilage rings are broken on the dorsalside of the trachea as illustrated in Fig. 2, III-IX. On the outer side of the bothends of the broken rings, there is a more or less membranous wall, which is developed particularly on the right side, so as to form an air-sac (Fig. 1, 1-V; Fig. 2,
V-VIII). Accordingly, the break in the rings serves as a passage to the air-sac.
This slitlike passage starts at about 50-60 mm from the diverging point of thebronchi and extends forward (toward the neck) (see Pls. 1 and 2). In general,
the slit becomes longer as the animal grows up (Table 1).
The sac occurs as a bulge of the relatively thick muscular membrane on theright outer side of the slit in the early stages of the development (Fig. I, I). The
sac grows larger, decreasing the thickness of membrane, and extends forward until
it reaches the neck of the animal; it also stretches rearward (toward the hind legs)
and, when fully developed, it becomes to cover the whole right ribs (Pl. 1, II; Fig.
1, V). As the sac grows larger, the membrane becomes thinner and translucent.
Also, the larger the sac, the better is its rearward development. For example, inSpecimen No. 6 the length between the foremost end of the sac and the starting
point of the slit is 120 mm, and from there to the rear end of the sac it is 70 mm
long. In Specimen No. 7 the measurement by the same method reveals that thesac is 150 mm long in its fore part and 230 mm long in the rear part.
The fore part extends forward, passing through the underside of the sternomastoid muscle. If the sac is small it is concealed by the muscle, but when it
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

A NOTE ON THE AIR-SAC OF RIBBON SEAL

II

Ill

131

IV

Fig. I. Developmental precesses of male air-sac and its opening part on the tracheaof the ribbon seal. I: No. 1 specimen in Table 1, II: No. 3, III: No. 5, IV: No.
6, V: No. 7, "0" in III to Vindicates the opening of the sac. VI: rear half oftrachea on the right side (No. 5 specimen), showing the opening and the valve(V) of the air sac which in this figure the membraneous sac has been removed.
Lower side in the figure VI is the dorsal side, the right tapering part is thebronchus.

grows larger its fore end appears ahead of the muscle. The rear part of the sac isfound between the pectoralis superfacies and the costae. Therefore, the existenceof the sac would be hardly noticed when the seal is only skinned.
On the right and left sides of the slit, part of the trachea forms a long andnarrow valve, with its rear end starting from the diverging point of the bronchi.
The valve has a slender crescent shape, being widest at the middle. The rightvalve is larger than the left in both length and width. The distance between
the two valves is largest at the slit (Table 1; Fig. 2 IX). The left valve does notseem to be functional at all, but the right valve, which is widest at the slit, is considered to conduct the important role for taking the air in and out of the sac (Pl,1, II and III). To clarify the function of these valves, further study is required
from the standpoint of histology and ecology.

2) Female
The fundamental features of the sac are identical with those of male. A valvular projection is observed at the dorsal inner side of the rear part of the trachea.
However, development of a sac is poor in female, and even in a fully grown stageof the animal the sac is of nearly the same size as that of a small male (Pl, 2, IV;
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

132

ABE, HASEGAWA AND WADA

II.

IX
Fig. 2. Developmental processes of air sac of ribbon seals, and cross and longitudinal sections of the sac and trachia. I : No. 10 specimen; II : No. 11 ; III :cross section at the central part of the valve in No 10 female; IV, V, VI, VIIa and VIII indicate the cross sections at the central part (" a " line on IX) of valve
in specimens 11, l, 3, 5, 7, respectively; VII-band VII-c: cross sections at" b"and " c " lines in IX. Lower side in the figures is the dorsal side of trachea ;V and S: valve and air sac; IX: longitudinal section showing the dorsal innerside of the opening part of trachea.
TABLE 1.

TOTAL LENGTH OF BODY, CONDYLOBASAL LENGTH OF SKULL
AND DIMENSION OF AIR-SAC (in mm)

species name·"'i::<L> ...

s

..@~

<L>

·08
~§

><

~

Histriophoca fasciata Z.
M
l
M
2
M
3
4
M
5
M
M
6
M
7
8
M
M
9
10
F
11
F
Phoca vitulina L.
12
M
M
13
-

air-sac

~

..c:
bO

~..8
B~

right valve

-«!~
::I

"'"'

>.£
-.:I Oili:: i::
0

<L>

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1260
1230
1300
1130
1370
1360
1500

177. 7
180.7
178.8
201.9

1310
1560

178.4
204.6

1450
1600

203.5
222.8

.s
-.:I

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bO

.g«I._0

t
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~

40
55
70
130
190
380
105
430

5
15
37
35
70
75
110
55
120

70

20

i::

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t

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86
82
92

..c:
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«!

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«!

27
25
35
40
42
46

102

14
9
9
11
11
11
13

40

80
84

14

24

3

80

left valve
«!

8

~

t

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82
73
71

82

5
5
4
4
5
4
7

70
80

7
6

60

7

68

s

broken and unmeasured.

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

A NOTE ON THE AIR-SAC OF RIBBON SEAL

133

Fig. 2, I-IV). Hasegawa examined a pregnant individual but could not confirm
the existence of the sac. In females, the sac, if any, may not be functional.
COMPARISON WITH OKHOTSK HARBOR SEAL
We dissected two males of Okhotsk harbor seal, which were captured together withthe above-mentioned ribbon seals, and examined their trachea for comparison withthat of ribbon seals. In that species, too, the cartilage rings are broken in the rearpart of the trachea, that is, immediately before the bronchil they diverge. However, the valvular projection is entirely different from that of ribbon seal, as it
occurs only on one side. One of the examined specimens had it on the right side
(Fig. 3), but the other had it on the left side. Specimen No. 11 is supposedly arelatively large individual, but it had no air-sac nor its trace.

Fig. 3. The longitudinal section of the rear part of trachea of Phoca vitulina (adultmale).

CONSIDERATIONAs to the role played by the sac, we can say nothing more than a conjecture. It isevident, however, that the sac is connected with the trachea through a simple functional valve, and there remains little doubt that the sac serves as an air-sac. The
size of the sac differs markedly between male and female, and also varies with theage of individual. These facts may indicate some differences in habit andbehavior of individual seals. According to certain hunters, ribbon seals, whenchased, would stay under the water for a long time; another hunter, however, says
he has experienced no such occasion. Thus, the hunters' comments cannot be
relied upon. In fact, the riddle of the sac would remain unsolved until scientificinvestigations are made on the ecology of ribbon seals.
It is of a special interest that the sac is located on the right side of the body,&i. Rep. Whales Res. Inst.,
No. 29, 1977.

ABE, HASEGAWA AND WADA

134

stretching beneath the sternomastoid muscle or between the pectoralis superfacies
and the costae, and that the sac grows larger along with the animal's growth. To
give reasonable explanation for these features, anatomical and ecological studies of
not only the ribbon seal but also other kinds of seals must be carried out in the
future. This is why the present writers refrain possible explanations of the roleof the sac.
REFERENCESSCHEFFER, V. B., 1960.

Dentition of the ribbon seal.

Proc. Zoo!. Soc. London, 135(4): 579-585.

* We have found recently that SLEPTSOV'S paper (.(ool . .(hum. 19(3) : 379-385, 1940) had described theoutline of the air-sac of this seal.

Sci. Rep. Whales R.es. Inst.,
No.. 29, 1977.

A NOTE ON THE AIR-SAC OF RIBBON SEALEXPLANATION OF PLATESPLATE I
I: Sac of young male (8 in Table 1). Ila and llb: Sac of adult male (9 in Table
1). Notice the valve closed (a) and opened (b).
PLATE II
Development of male sac (I-III) and primitive small sac of an adult female (IV).
I-IV show those of specimens 3, 5, 7, respectively. Sacs of II to IV have been dissected to show the inside and the opening.

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

135

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ON THE NORTHERN EXTREME OF THE PACK-ICE EDGE
OBSERVED BY WHALING VESSELS IN THE SUMMER
OF THE ANTARCTIC SEASONS 1957 /58-1962/63
AKITO KAWAMURA*
Whales Research Institute, TokyoANDTERUHIKO FURUNO
Nippon Kyodo Hogei K.K., Tokyo

During the cruise of exploratory fishing and scouting for sei whales by the freezer,
Eiho Maru of Hokoku Suisan K.K. in 1971/72 Antarctic season, one of the authors(A.K.) got acquaintance with Teruhiko Furuno, skipper of one of the whale catchers
belonging to Nippon Suisan K.K. that has been sending a couple of whaling fleetsto the Antarctic for many years since 1946. Furuno, one of present authors is awell experienced captain in the Antarctic whaling operation, and is very skillful
as the skipper of scouting boat. While we had been on high seas in the Southern Ocean, Furuno kindly permitted me to see and reproduce his important dataon the northern extreme of the drifting pack-ice which have been observed during
the whaling seasons in some Antarctic regions where the whaling has been mostintensively conducted through the past several seasons. The present material issolely based on the data recorded by Furuno.
Since its re-establishment of the pelagic whaling operation to the Antarctic
Ocean in 1946/47 season onward, Japan has successively sent thirty-one times ofwhaling expeditions to date. Each expedition during the seasons of 1957/58 to
1962/63 was operated by using six to seven mother ships, each of which usually accompanied about nine to ten catcher boats. In the whaling grounds those catcher
boats are generally dispersed widely over the region to be harvested in order tolocate the best place as the whaling ground. They scout about the region bylooking for the school of whales, and they also try to locate the position of the packice edge as much as possible along the steaming course since it is one of the mostimportant sea conditions for the stable whaling operation.
It may be easy to suppose that each whaling company keeps such kind of data
under their control, and usually those data are placed beyond the public use by reason of confidential material only be opened within the companies. Under these circumstances the figures shown in this report are considered one of those ' exhumed 'material showing the location of northernmost extreme of retreating pack-ice
during the austral summer. The figures are based on day-by-day reports ~x­changed between whale catchers worked out for the corresponding seasons. Although the behaviour of the pack-ice in the high Ant~rctic Ocean is observed rather* Present address: Faculty of Fisheries, Hokkaido University, Hakodate, Hokkaido.
Sci. Rep. Whales Res. Inst.,
No. 29, 1977, 137-141.

138

KAWAMURA AND FURUNO

easily at present by using the artificial satellite systems, the material provided inthis report may be of interests for many purposes as the evidence of past years.
Although the material provides only a fraction of knowledge on the movementof pack-ice in time and space, one of distinctions be noted may be found in theirsimultaneousness in obtaining the positions of the pack-ice at the different localities,i.e., they were located within a relatively short intervals of the days, and this would
make ones enable to estimate how fast the pack-ice as indicated by the location ofnorthernmost extreme shifts back and forth. Still more, ~he material would be
helpful for estimating the area of ice coverage as to the environmental conditions
for the marine life in the regions such as the figures given by Mackintosh (1970).
Apart from these the present data may provide a reference in checking the monthly
mean position of the pack-ice edge that was reported previously (e.g. Mackintosh

19571958-··1959·-·1960-1961 ---1962 -------)

Fig. 1. Northern extreme of the pack-ice edge in November.
denotes the date of observations.

Numeral in the figure

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

PACK-ICE IN THE ANTARCTIC139

DECEMBER
19571958-··1959-·19601961--1962 ·······

lO)

Fig. 2. Northern extreme of the pack-ice edge in December.
figure denotes the date of observations.

0

Numeral in the

30E

JANUARY
1958 -··1959 --1960 -Fig. 3. Northern extreme of the pack-ice edge in January.
denotes the date of observations.

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

lO\i\-t++++-++--+-++++-+++++-++10rn

Numeral in the figure

140

KAWAMURA AND FURUNO
30W

0

30

FEBRUARY
1958 -··1959 - · 1960·-\t-t-14-t-+-t-+-+-H-l-H-+-+-f.-HH-l~

Fig. 4. Northern extreme of the pack·ice edge in February.
figure denotes the date of observations.

rn

Numeral in theand Herdman, 1940; Treshnikov, 1967).
Following are the notes based on the communications with Furuno, and theseshould be took in mind when one consults a matter with the figures demonstrated(Figs. 1-4):
1) The whole data for making those figures were obtained by all whalingboats participated to the Antarctic whaling seasons under the flag of the Nippon
Suisan K.K. Two kinds of whaling boats may be distinguished by the purpose of
their use; the first one is the whale chaser of actually catching the whales and thesecond one is the scouting boat which often heads for far distant region in searchof possible whaling ground to be harvested in near future. Furuno has been
worked out as one of the skippers of those scouting boats throughout the mostof his Antarctic life.
2) It was very often or usual that the ship's position was hardly determined
for several days or even more than a week due to ill conditioned weather, andtherefore there were no other ways but find the ship's position temporarily by theso-called dead reckoning. However, the position was corrected as much as possible
whenever the weather permitted to have sun shot.
3) It may be said empirically that the deviation of ship's position due _todead reckoning by rough weather would be usually somewhere around 5 to 6
nautical miles a day from the true position.
4) It was, however, very calm usually in the southern region close to thepack-ice edge, and most of the suggested positions in the figures could be consideredcorrect enough for the purpose of general use.
5) A slight ocean current was noticed in the regions close to the pack-ice,but there was strong current at times when the ship positioned at some distance,
Sci. Rep. Whales Res. Inst.,

No. 29, 1977.

PACK-ICE IN THE ANTARCTIC

141

say, 10 to 20 miles off the ice limit though it varied considerably by the place andthe seasons.
6) Although there seems to be considerable varieties in the state of pack-ice
such as ' open ', ' close ', ' very close ' and so on, there were no specifications in the
figures.
7) In the northernmost extreme of tongue-like projection as a shape of packice distribution, the state of pack-ice was usually ' open ' or ' close ' ones. Thereobserved no 'very close' pack-ice in those above mentioned regions.
8) In the far more southerly region beyond the observed ice limit, it was very
often to exist a large ice free waters, especially in the place where the northernmost
extreme of the pack-ice greatly expands toward north and forms a tongue-likeprojection. In these regions there was a good deal of distance between the northernmost ice edge and the second one which lies considerably in the south.
We would like to express our appreciation to Nippon Suisan K.K. and to all
personnel who had been participated to the Antarctic whaling operations during
the seasons from which our data originated.
REFERENCES
MACKINTOTH, N. A., 1970. Whales and krill in the twentieth century. In: Antarctic Ecology, M. W. Holdgate (ed.), Vol. 1, Academic Press, London, 604 p.
MACKINTOSH, N. A. and H. F. P. HERDMAN, 1940. Distribution of the pack-ice in the southern ocean. Discovery Reports, 19 : 285-296.
TRESHNIKOV, A. F., 1967. The ice of the southern ocean. Japanese Antarctic Research Expedition, ]ARE Sci.
Reports, Special Issue, No. I : 113-123.

Sci. Rep. Whales Res. Inst.,

No. 29, 1977.

THE SCIENTIFIC REPORTS OF THE WHALES RESEARCHINSTITUTE, TOKYO, JAPANNUMBER 1, JUNE 1948
Akiya, S. and S. Tejima. Studies on digestive enzyme in whale. 3-7
Akiya, S., Y. Ishikawa, S. Tejima, and T. Tanzawa. Studies on tryptase from a whale (Balaenoptera borealis

L.).

8-10

Akiya, S., S. Tejima, and Y. Ishikawa. Studies on the utilization of whale meat by the use of pancreatic
tryptase of whales. 11-14
Akiya, S. and F. Kobo. 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 meat andbeef on deterioration of freshness and autolysis. 27-30
Tawara, T. On the simultaneous extraction of vitamin A-D and vitamin B2 complex from the liver of afin whale (Nagasu-Kujira, Balaenoptera physalus L.). 31-37
Tawara, T. Studies on whale blood. I. On the separation of histidine from whale blood. 38-40
Nakai,.J. and T. Shida. Sinus-hairs of the sei-whale (Balaenoptera borealis). 41-47

NUMBER 2, DECEMBER 1948
Ogawa, T. and S. Arifuku. On the acoustic system in the cetacean brains. 1-20
Yamada, M. Auditory organ of the whalebone whales. (Preliminary report). 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 Na2 C0 2 • 31-34
Ishikawa, S., Y. Omote, and Y. Soma. Analytical distillation of vitamin A in the whale liver oil. 35-41
Ishikawa, S., Y. Omote, and H. Kanno. Molecular distillation of sperm whale blubber oil. 42-45
Kaneko, A. Molecular distillation of fin whale liver oil. 46-50
Akiya, S. and K. Takahashi. Determination oftryptophane in whale meat. 51-54
Ishikawa, Y. and S. Tejima. 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 T. Shida. On the sensory tubercles oflips 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 cetacean larynx, with special remarks on the laryngeal sack of the sei whale andthe aryteno-epiglottideal tube of the sperm whale. 23-62
Akiba, T., T. Tsuchiya, M. Umehara, and Y. Natsume. 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 M. Saiki. Properties of fats and oils contained in various parts of a sperm whale body. 7984
Tawara, T. and R. Fukazawa. Studies on kitol. I. Preparation of kitol from whalf: liver oil. 85-88
Tawara, T. and R. Fukazawa. Studies on kitol. II. Influence of kitol fraction on the determination of
the International Unit of Vitamin A. 89-91
Tawawa, T. and R. Fukazawa. Studies on kitol. III. The effect of sunlight, air and heat on the vitamin
A and kitol fractions. 92-95

ii
Tawara, T. On the respiratory pigments of whale (Studies on whale blood II.). 96-101
Yoshida, M. Research on methionine in whale. 102-105
Mizue, K. Factory ship whaling around Bonin Islands in 1948. 106-118
Mizue, K. and H. Jimbo. Statistic study of foetuses of whales. 119-131
Nishiwaki, M. and K. Hayashi. 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 in crystalline 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., M. Umehara and Y. Natsume. 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 0. Hoshino. Isolation ofhistidine from whale blood using 3,4-dichlorobenzene sulfonic acid.
41-47
Tawara, T. and R. Fukazawa. Studies on kitol. IV. Purification ofkitol by chromatographic. 49-51
Ishikawa, S., Y. Omote and H. Okuda. Substances related to vitamin A in the whale liver oil. 53-59
Ishikawa, S., Y. Omote, M. Kijima and H. Okuda. Thermal decomposition ofkitol. 61-69
Mizue, K. Grey whales in the east sea area of Korea. 71-79
Mizue, K. Food of whales (In the adjacent waters ofJapan). 81-90
Nishiwaki, M. and T. Ohe. 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 eye muscles of the whale, with special remarks upon the innervation andfunction 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 T. Murata. 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 T. Hibiya. On the sexual maturity of the sperm whales (Physeter catodon) found in theadjacent 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 H. Ono. The effects of electric shock and fatigue on post-mortem changes in muscle. 177185

iii
Omote, Y. Complete recovery of vitamin A from molecular distillation residue of whale-liver oil. 187191
Omote, Y. Chemical structure ofkitol (I). Double bonds and hydroxyl groups. 193-198
Hirata, M. Experimental investigation on flattened 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 those of Berardius bairdii
Stejneger. 1-22
Akiya, S., 0. Hoshino and N. Motohashi. On an attempt to preserve whale meat freshness with 5-nitrofurfuriden aminoguanidine from decay. 23-30
Akiya, S. and R. Sawamura. Colorimetric determination of 5-nitro-2-furfuridene aminoguanidine. 31-36
Tomiyama, S. and M. Takao. Studies on utilization of higher fatty alcohol from sperm whale oil. 37-46
Omote, Y. A rapid method for the separate determination of vitamin A and kitol in the whale-liver oil.
47-50
Arai, Y. and S. Sakai. Whale meat in nutrition. 51-67
Yamaguchi, K. and K. Fujino. On the serological constitution of striped dolphin (Prodelphinus caeruleoalbus(Meyen)) (I). 67-77
Nishimoto, S., M. Tozawa and T. Kawakami, Food ofsei whales (Balaenoptera borealis) caught in the Bonin
Island waters. 79-85
Nishiwaki, M. On the age-determination of Mystacoceti, chiefly blue and fin whales. 87-119
Nishiwaki, M. and T. Hibiya. On the sexual maturity of the sperm whales (Physeter catodon) found in theadjacent waters of Japan (II). 121-124
Ohno, M. and K. Fujino. Biological investigation on the whales caught by the Japanese Antarctic whaling
fleets, season 1950/51. 125-183

NUMBER 8, JUNE 1953
Yamada, M. 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 T. Yagi. On the age and the growth of teeth in a dolphin (Prodelphinuscaeruleo-albus).
(I). 133-146
Kakuwa, Z., T. Kawakami and K. Iguchi. 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 (Prodelphinuscaeruleo-albus). 215-218

NUMBER 9, JUNE 1954
Akiya, S., 0. Hoshino and N. Motohashi. Attempt to preserve 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 K. Fujino. Sei whales in the adjacent waters ofJapan. II. Further studies on the external
characters. 89-103
Fujino, K. On the serological constitution of the sperm- and Baird beaked-whales (I) Blood groups ofthe sperm- and Baird beaked-whales. 105-120

iv
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., T. Hibiya and S. Kimura. On the sexual maturity of the sei whale of the Bonin waters.
165-177
Uda, M. Studies of the relation between the whaling grounds and the hydrographical conditions (1).
179-187

NUMBER 10, JUNE 1955
Hosokawa, H. Cross-sections ofa 12-mm. dolphin embryo. 1-68
Nemoto, T. White scars on whales (I) Lamprey marks. 67-77
Omura, H. and T. Nemoto. Sei whales in the adjacent waters of Japan. III. Relation between movement and water temperature of the sea. 79-87
Omura, H., K. Fujino and S. Kimura. 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 ofJapan (II.) 133-141
Nishiwaki, M. On the sexual maturity of the Antarctic male sperm whale (Physeter catodon L.). 143-149
Ohta, K., T. Watarai, T. Oishi, Y. Ueshiba, S. Hirose, T. Yoshizawa, Y. Akikusa, M. Sato and K. Okano,Composition of fin whale milk. 151-167

NUMBER 11, JUNE 1956
Omura, H. and H. Sakiura. Studies on the little piked whale from the coast of Japan. 1-37
Nishiwaki, M., T. Hibiya and S. Kimura. 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. 85-98
Nemoto, T. On the diatoms of the skin film of whales in the northern Pacific. 99-132
Hoshina, T. and Y. Sugiura. 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 ofdibranchiate cephalopods. II. A cranchiidae squid of thegenus Taonius. 153-161
Uda, M. and K. Nasu. Studies of the whaling grounds in the northern sea-region of the Pacific Ocean inrelation to the meteorological and oceanographic conditions. (Part I). 163-179
Kimura, S. and T. Nemoto. 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 the absorption of carbon dioxide by whale oils. 191-213

NUMBER 12, JUNE 1957
Omura, H. Osteological study of the little piked whale from the coast ofJapan. 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 andthe Bering Sea in summer of 1955. 91-101
Kimura, S. The twinning in southern fin whales. 103-125
Ichihara, T. An application oflinear discriminant function to external measurements of fin whale. 127189

v

Nishiwaki, M. Very small embryo of cetacea. 191-192
Nishiwaki, M. One-eyed monster of fin whale. 193-195
Ogawa, T. and T. Kamiya. A case of the cachalot with protruded rudimentary hind limbs. 197-208
Uda, M. and A. Dairokuno. 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 boundaryof water masses. 209-224
Abe, T. Notes on fishes from the stomachs of whales taken in the Antarctic. I. Xenocyttus nemotoi, a new
genus and new 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, Mirounga angustirostris.
235-240NUMBER 13, SEPTEMBER 1958
Omura, H. North Pacific right whale. 1-52
Nishiwaki, M. and T. Kamiya. A beaked whale Mesoplodon stranded at Oiso Beach, Japan. 53-83
Nishiwaki, M. and C. Handa. Killer whales caught in the coastal waters off Japan for recent 10 years.
85-96
Ohsumi, S. (Kimura), M. Nishiwaki and T. Hibiya. Growth of fin whale in the northern Pacific. 97133
Nishiwaki, M., T. Hibiya and S. Ohsumi (Kimura). Age study of sperm whale based on reading of
tooth laminations. 135-153
Nishiwaki, M., T. Ichihara and S. Ohsumi (Kimura). Age studies of fin whale based on ear plug. 155169
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 K. Nasu. 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. 213-214
Uda, M. and N. Suzuki. 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 of theright whale. 253-267
Hosokawa, H. and T. Sekino. Comparison of the size of cells and some histological formations between
whales and man. 269-301
Ogawa, T., T. Tsunoda and M. Osawa. Amino acid composition of whale meat. 303-307
Ishikawa, Y. A characteristic property of whale oils concerning the absorption of gases. II. On the absorption 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 T. Kamiya. Mesoplodon stejenegeri from the coast ofJapan. 35-48
Nishiwaki, M. Humpback whales in Ryukyuan waters. 49-87
Cushing, John E., K. Fujino and K. Takahashi. Glycerol-freezing technique as an aid in blood typing
ofwhales. 89-100

vi
Fujino, K. and John E. Cushing. Blood typing of dried whale erythrocytes with 131 1 labelled antibody.
101-106lchihara, 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 movements. 149-290
Yamada, M. and F. Yoshizaki. 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, Balaenopterapk_ysalus (Linn.). 17-84
Fujino, K. lmmunogenetic and marking approaches to identifying subpopulations of the North Pacificwhales. 85-142
Nasu, K. Oceanographic investigation in the Chukchi Sea during 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 information on Bryde's whale from the coast ofJapan. 7-18
Nishiwaki, M. Ryukyuan whaling in 1961. 19-28
Nemoto, T. A secondary sexual character of fin whales. 29-34
Omura, H., M. Nishiwaki, T. lchihara and T. Kasuya. 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., S. Ohsumi and T. Maeda. Change of form in the sperm whale accompanied with growth.
1-14
Ohsumi, S., T. Kasuya and M. Nishiwaki. The accumulation rate of dentinal growth layers in the maxillary tooth of the sperm whale. 15-35
lchihara, T. Photometric method for counting laminae in ear plug of baleen whale. 37-48
Yoshikawa, T. and T. Suzuki. 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., K. Fujino and N. Calaprice. The Ju blood typing system of the sperm whale and specificsoluble substances. 67-77
Nemoto, T. New records of sperm whales with protruded rudimentary hind limbs. 79-81
Nemoto, T. and K. Nasu. 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
Nasu, K. Oceanography and whaling ground in the subarctic region of the Pacific Ocean. 105-155

vii
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 U. Naruse. Studies on the oil of black right whale in the northern Pacific Ocean. 171190
Yagi, T., M. Nishiwaki and M. Nakajima. A preliminary study on the method of time marking withleadsal t 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
lchihara, 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 ofbadeen 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 U. Naruse. 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. 1-35
Kasuya, T. and T. lchihara. Some informations on minke whales from the Antarctic. 37-43
Nemoto, T. and T. Kasuya. Foods of baleen whales in the Gulf of Alaska of the North Pacific. 45-51
Nishiwaki, M., M. Nakajima and T. Kamiya. A rare species of dolphin (Stenella attenuata) from Arari,Japan. 53-64
Nishiwaki, M., T. Kasuya, T. Tobayama, T. Kamiya and M. Nakajima. Feresa attenuata captured at the
Pacific Coast of Japan in 1963. 65-90
Nakajima, M. and M. Nishiwaki. The first occurrence ofa porpoise (Electra electra) in Japan. 91-104
Hosokawa, H. and T. Kamiya. Sections of the dolphin's head (Stenella caeruleoalba). 105-133
Ohsumi, S. A dolphin (Stenella 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
lchihara, T. Criterion for determining age of fin whale with reference to ear plug and baleen plate. 1782
Kasuya, T. Caryotype of a sei whale. 83-88
Kasuya, T. and S. Ohsumi. A secondary sexual character of the sperm whale. 89-94
Nishiwaki, M. and K. S. Norris. A new genus, Peponocephala, for the odontoceti cetacean species Electra
electra. 95-100
Nishiwaki, M., M. Nakajima and T. Tobayama. 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
lchihara, T. and M. Nishiwaki. External measurements and weight of a southern elephant seal. ·211-212

viii
Tsuyuki, H. and S. Itoh.

Studies on the oils contained in blubber of a southern elephant seal.

213-221

NUMBER 21, JUNE 1969
Omura, H., S. Ohsumi, T. Nemoto, K. Nasu and T. Kasuya. Black right whales in the North Pacific.
1-78
Nishiwaki, M. and Y. Hasegawa. The discovery of the right whale skull in the Kisagata shell bed. 79-84
Ohsumi, S. Occurrence and rupture ofvarginal band in the fin, sei, and blue whales. 85-94
Hosokawa, H., S. lgarashi, T. Kamiya and K. Hirosawa. Morphological characteristics and myelinization of acoustic system in the dolphins (Stenella caeruleoalba). 95-123
Mo!, T. and P.J.H. van Bree. A short contribution to the history of whaling in Japan during the l 7th
century. 125-129
Tsuyuki, H. and S. Itoh. Fatty acid composition of finless porpoise oil. 131-135.
Tsuyuki, H. and S. Itoh. Fatty acid composition of many toothed pilot whale oil. 137-141

NUMBER 22, JUNE 1970
Omura, H., T. lchihara and T. Kasuya. Osteology of pygmy blue whale with additional information on
external and other characteristics. 1-27
Nishiwaki, M. and T. Kasuya. Recent record of gray whale in the adjacent waters of Japan and a consideration on its migration. 29-37
Kasuya, T. and D. W. Rice. Note on baleen plates and on arrangement of parasitic barnacles of graywhale. 39-43
Nishiwaki, M. and T. Kasuya. A Greenland right whale caught at Osaka Bay. 45-62
Nasu, K. and Y. Masaki. Some biological parameters for stock assessment of the Antarctic sei whale.
63-74
Ohsumi, S., Y. Masaki and A. Kawamura, Stock of the Antarctic minke whale. 75-125
Kawamura, A. Food ofsei whale taken by Japanese whaling expeditions in the Antarctic season 1967/68.
127-152
Nemoto, T. and K. I. Yoo. An amphipod, Parathemisto gaudichaudii as a food of the Antarctic sei whale.
153-158
Tobayama, T., S. Uchida and M. Nishiwaki. 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 S. Itoh. Fatty acid components of black right whale oil by gas chromatography. 165-170

NUMBER 23, SEPTEMBER 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., M. Nishiwaki and T. Kasuya. Further studies on two skeletons of the black right whale in
the North Pacific. 71-81
Nishiwaki, M. and T. Kasuya. Osteological note of an Antarctic sei whale. 83-89
Hosokawa, H. and T. Kamiya. Some observations on the cetacean stomachs, with special considerations
on the feeding habits of whales. 91-101
Lugassy, A. A., E. Korostoff and J. L. Rabinowits. Influence of incremental lines upon the compressive
strength of sperm whale dentin. 103-110

ix
Nishiwaki, M. and N. Oguro. Baird's beaked whales caught on the coast of Japan in recent 10 years.
111-122
Mizue, K., M. Nishiwaki and A. Takemura. The underwater sound of Ganges river dolphins (Platanista
gangetica). 123-128
Kasuya, T. and M. Nishiwaki. First record of Mesoplodon densirostris from Formosa. 129-137
Kawamura, A. and K. Kashita. A rare double monster of dolphin, Stenella caeruleoalba. 139-140
Tsuyuki, H. and S. Itoh. 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 cauirostris, in the northwest Pacific.
1-34
Nishiwaki, M. and N. Oguro. Catch of the Cuvier's beaked whales off Japan in recent years. 35-41
Nishiwaki, M., T. Kasuya, K. Kureha and N. Oguro. Further comments of Mesoplodon gingkodens. 43-56
Kasuya, T. Growth and reproduction of Stenella caeruleoalba based on the age determination by means ofdentinal growth layers. 57-79
Kasuya, T. and N. Oguro. 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.
87-108Kasuya, T. and A.K.M. Aminul Haque. Some informations on the distribution and seasonal movementof the Ganges dolphin. 109-115
Tsuyuki, H. and S. Itoh. Fatty acid component of various blubber oil of Ganges River dolphin. 117-125
Naito, Y. and M. Nishiwaki. The growth of two species of the harbour seal in the adjacent waters of
Hokkaido. 127-144
Ichihara, T. and K. Yoshida. Diving depth 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 data in
10° squares oflatitude 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 dorasl vagal nucleus to the upper cervical
cord in the sperm whale. 241-249
Tobayama, T., M. Nishiwaki and H. C. Yang. Records of the Fraser's Sarawak dolphin (Lagmodelphis
hosei) in the western North Pacific. 251-263
Miyazaki, N., T. Kusaya and M. Nishiwaki. Food of Stenella caeruleoalba. 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 S. Itoh. 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. PoJsible migration route of the gray whale on the coast of Japan. 1-14
Sa take, Y. and H. Omura. A txonomic study of the minke whale in the Antarctic by means of hyoid bone.
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., N. Miyazaki and W. H. Dawbin. Growth and reproduction of Stenella attenuata in the Pacificcoast of Japan. 157-226
Miyazaki, N., T. Kasuya and M. Nishiwaki. Distribution and migration of two species of Stenella in the
Pacific coast of Japan. 227-243
Kamiya, T. and P. Pirlot. Brain morphogenesis in Stenella coeruleoalba. 245-253
Castello, H.P., A. P. Torno and J. S. Fanizza. First Antarctic record of a killer whale stranding. 255258
Kamiya, T. and N. Miyazaki. A malformed embryo of Stenella coeruleoalba. 259-263
Kamiya, T. and F. Yamasaki. Organ weights of Pontoporia blainvillei and Platanista gangetica (Platanistidae).
265-270
Machida, S. Surface temperature 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 H. Tsuyuki. Fatty acid component of different blubber oil of finless porpoise. 303-306
Itoh, S. and H. Tsuyuki. 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

NUMBER 27, SEPTEMBER 1975
Omura, H. Osteological study of the minke whale from the Antarctic. 1-36
Williamson, G. R. Minke whales off Brazil. 37-59
Kawamura, A. A consideration on an available source of energy and its cost for locomotion in fin whales
with special reference to the seasonal migrations. 61-79
Kasuya, T. and M. Nishiwaki. Recent status of the population of Indus dolphin. 81-94
Kasuya, T. Past occurrence of Globicephala melaena in the western North Pacific. 95-108
McCann, C. A study of the genus Berardius Duvernoy. 111-137
Nishiwaki, M. and K. Kureha. Strange organ in the anal region of the finless porpoise. 139-140
Machida, S. Distribution of sperm whale catches in the southern Indian Ocean. 141-159

NUMBER 28, OCTOBER 1976
Kawamura, A. and Y. Satake. Preliminary report on the geographical distribution of the Bryde's whalein the North Pacific with special reference to the structure of the filtering apparatus. 1-35
Pivorunas, A. A mathematical consideration on the function of baleen plates and their fringes. 37-55
Omura, H. and T. Kasuya. Additional information on skeleton of the minke whale from the Antarctic.
57-68
Omura, H. A skull of the minke whale dug out from Osaka. 69-72
Kasuya, T. Reconsideration of life history parameters of the spotted and striped dolphins based on cemental layers. 73-106
McCann, C. Notes on the foetal skull of Mesoplodon stejnegeri. 107-117
Gianuca, N. M. and H. P. Castello. First record of the southern bottlenose whale, Hyperoodon planifrons
from Brazil. 119-126
Brownell, R. L. Jr., L. A. Aguayo and N. D. Torres. A Shepherd's beaked whale, Tasmacetus shepherdi, fromthe eastern South Pacific. 127-128
Brownell, R. L. Jr. and R. Praderi. Records of the delphinid genus Stenella in western South Atlantic

xiwaters. 129-135
Yama.saki, F., H. Satomi and T. Kamiya. An observation on the papillary projections at the lingual
inargin in the striped dolphin. 137-140
Kasuya, T. and N. Miyazaki. An observation of epimeletic behavior of Lagenorhyncus obliquidens. 141-

143
Kawakami, T. Squids found in the stomach of sperm whales in the northwestern Pacific. 145-151
Leung, Y. M. Life cycle of G_yamus scammoni (Amphipoda: Cyamidae), ectoparasite of gray whale, witha remark on the associated species. 153-160
Kagei, N., T. Tobayama and Y. Nagasaki. On the helminthum of Franciscana, Pontoporia blainvillei.

161-166
Tsuyuki, H. and S. Itoh. Fatty acid component oflipid of Euphausia superba. 167-174
Naito, Y. The occurrence of the phocid seals along the coast ofJapan and possible dispersal of pups.

175185
Naito, Y. and M. Oshima. The variation in the development of pelage of the ribbon seal with reference
to the systematics. 187-197

NUMBER 29, DECEMBER 1977
Kasuya, T. Age determination and growth of the Baird's beaked whale with a comment on the fetal
growth rate. 1-20
Miyazaki, N. On the growth and reproduction of Stenella coeruleoalba off the Pacific coast ofJapan. 21-48
Kawamura, A. On the food of Bryde's whales caught in the South Pacific and Indian Oceans. 49-58
Herman, L. M. and R. C. Antinoja. Humpback whales in the Hawaiian breeding waters: population andpod characteristics. 59-85
Aminul Haque, A.K.M., M. Nishiwaki, T. Kasuya and T. Tobayama. Observations· on the behaviourand other biological aspects of the Ganges susu, Platanista gangetica. 87-94
Yamasaki, F., S. Komatsu and T. Kamiya. A comparative morphology of anal tonsils in Platanistidae.

95-100
Nemoto, T., R. L. Brownell, Jr. and T. Ishimaru. Coconeis diatom on the skin of Franciscana. 101-105
Castello, H.P. Food of a killer whale: Eagle sting-ray, Myliobatis found in the stomach of a stranded
Orcinus orca. 107-111
Nishiwaki, M. and A. Sasao. Human activities disturbing natural migration routes of whales. 113-120
Yoshida, K., N. Baba, M. Oya and K. Mizue. On the formation and regression of corpus luteum in thenorthern fur seal ovaries. 121-128
Abe, H., Y. Hasegawa and K. Wada. A note on the air-sac of ribbon seal. 129-135
Kawamura, A. and T. Furuno. On the northern extremes of pack ice observed by whaling vessels in thesummer of the Antarctic seasons 1957/58-1962/63. 137-141

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