OBSERVATION OF CETACEA DURING WHALE
MARKING CRUISE IN THE WESTERNTROPICAL PACIFIC, 1976NOBUYUKI MIYAZAKI
Department of Zoology, National Science Museum, TokyoANDSHIRO WADA
Far Seas Fisheries Research Laboratory, Shimizu

ABSTRACT

From 20 January to 19 March 1976, the whale marking and sighting
were carried out in the western tropical Pacific. During this survey 103
schools of 13 species from 11 genera were sighted, and 15 specimens of 5
species from 4 genera were collected. Observations of these 103 schools
were made and the biology of these 15 specimens was studied.

INTRODUCTION

Distribution and biology of cetaceans in the western tropical Pacific have been
almost not known till 1972. Recently Masaki (1972) and Wada (1975) carriedout the tagging Investigation of cetacea in the western tropical Pacific. In Ogasawara and Mariana Islands Masaki (1972) found Physeter catodon, Balaenoptera borealis,B. edeni, Stenella coeruleoalba, S. attenuata, Pseudorca crassidens, Globicephala macrorhynchus,
Delphinus delphis, Ziphius cavirostris. According to Wada (1975) P. catodon, B. edeni,
S. coeruleoalba, S. attenuata, G. macrorhynchus were sighted in the southwest areas of
the North Pacific. However, still little is known about thedistribution and biologyof cetaceans in these areas. This paper reports biological investigations of cetaceans carried out during winter season in the western tropical Pacific.
MATERIALS AND METHODS

The vessel used was the Miwa-marn, 199.68 grosstons and maximum speed II knot.
It was used from 20 January to 19 March 1976. The cruising course of thissurvey is shown in Fig. I. The total cruising and sighting distance were 9,178
and 6,074 nautical miles, respectively. The total time of observation was 631.8
hours. Sightings were usually carried out by three persons at the foremast andtwo at the upper bridge except for in heavy rain.
Specimens were collected with shot gun and hand harpoon. The specimens
were measured, photographed, and made on biological examinations as soon as
Sci. Rep. Whales Res. Inst.,
No. 30, 1978., 179-195

180

MIYAZAKI AND WADA

18 M.

30° N
17 M.
22J.
16 M.

23 J,

15 M,

20° N
24 J.

2 5 J.

2 6 J.

14 M.

13 M.

12 M.

1 0° N

QO

10°5
25 F.

Fig. 1. The cruising course of Miwa-maru from 20 January to 19 March 1976.
J., F., and M. mean January, February, and March, respectively. Numbers
indicate dates.

possible after hauling them aboard the vessel. Testes and ovaries were collected
and fixed with 10% formalin solution. In the laboratory testes and ovaries were
weighed, the number of corpora counted, and the diameters of Graafian follicles
measured. The testes of the specimens were histologically examined.
OBSERVATIONS AND BIOLOGICAL INFORMATIONS
During this survey 103 schools of 13 species from 11 genera were sighted, and 15
dolphins of 5 species from 4 genera were collected. Informations on the distribution, behavior, and biology of these species are given below.

Balaenoptera edeni
Bryde's whales, Balaenoptera edeni, are common in the western tropical Pacific(Masaki 1972, Wada 1975). As the research vessel could always approach to
Sci. Rep. Whales Res. Inst.,
No. 30, 1978.

CETACEAN IN WESTERN TROPICAL PACIFIC

181

Bryde's whales, it is easy for us to identify the species. Especially it is also possible
to distinguish the species from the sei whale, Balaenoptera borealis, basing on thethree ridges on the snout.
Fifty animals of 25 schools of Bryde's whale, and 4 females with calf in theseschools were found (Table 1). Estimated body size of 4 calves, 4 females with
calf, and the other animals were 7-8 m, 12-13 m, and 11-13 m, respectively. We
could not find subadult animals between 8 and 11 m. According to Masaki(1972) and Wada (1975), they did not also find subadult animals in winter seasonof the western tropical Pacific. From these data it seems that the subadult ofBryde's whale geographically segregate from the adult in winter season of thisarea. In order to solve this problem it is necessary to accumulate more data in
the future.
Bryde's whales were sighted mostly in the area of 0°-2°N latitude and 142°1440E longitude, especially around Manus Islands, Solomon Islands, and Nauru
Island (Fig. 2). Sea surface temperature at sighting positions ranged from 28.5°C
to 30.0°C. School size ranged between 1 and 8 animals, but most of the groups
had only one or two whales (Fig. 5 ). This suggests that Bryde's whales mostly
distribute on solitary or pair, and sometime make small school less than 10 animals
in winter season of the western tropical Pacific.
Six Bryde's whales of schools (sighting Nos 13, 14, 15, 22, 23, 24) were foundtogether with bonito schools and many sea birds. Especially several animals of theschool (sighting No. 14) chased the prey turning sideways with their mouths open
and appeared to be feeding. This suggests that Bryde's whales take the prey inwinter season. Many remoras (Echeneidae) were found on the back of one adultanimal in a school (sighting No. 19).

Physeter catodon
Sperm whale, Physeter catodon is common in the western tropical Pacific(Masaki, 1972; Wada, 1975). Twelve schools with a total of 156 sperm whales
were found. As shown in Fig. 2, sperm whales were often found around islands.
The school size ranged from 1 to 28 animals (Fig. 5 ). Sea surface temperature atsighting positions ranged from 28. 7°C to 29. 7°C (Table 1).
Estimated body length of four sperm whales sighted separately (sighting Nos
33, 34, 35, 36) was between 12 and 14 m. These whales were probably solitary
adult males. These animals were often observed to dive for 15 to 25 minutes.
Four schools had female with calf (Table 1). These females and calves were often
found slightly apart from other animals in the school. Estimated body size ofthese females and calves were 9-10 m and 4-5 m, respectively. Six schools werecomposed of the subadults or adults, and the school size of these whales was between 8 and 28. In a school (sighting No. 31) there are three groups of the animals. The group composed of 11 adult animals, 5 subadult ones, and 2 calves
was placed between two groups, one of which was consisted of 6 adult animals andthe other 4 adult ones. One school (sighting No. 38) had eight adult whales andthese were found side by side approximately 2-3 m apart. Sperm whales in one
Sci. Rep. Whales Res. Inst.,
No. 30, 1978.

~'?

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...'~
~

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~~

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Species

27
28
29
30

"

"

"

"

1 Balaenoptera edeni
2
"
3
"
4
"
5
"
6
"
7
"
8
"
9
"
10
"
11
"
12
"
13
"
14
"
15
"
16
"
17
"
18
"
19
"
20
"
21
"
22
"
23
"
24
"
25
"
26 Physeter catodon

Sighting
No.

7 II '76
7 II '76
7 II '76
8 II '76

30 I '76
31 I '76
1 II '76
1 II '76
1 II '76
5 II '76
5 II '76
6 II '76
6 II '76
6 II '76
6 II '76
6 II '76
6 II '76
6 II '76
7 II '76
13 II '76
18 II '76
21 II '76
21 II '76
21 II '76
21II'76
4 III '76
4 III '76
4 III '76
6 III '76
30 I '76

Date

TABLE 1.

Ol 24'S, 148°06'E
0 l 0 34°S, l 48°42'E
01°50'S, 148°47'E
03°16'S, 150°24'E
000°54'N, 142°05'E
00°16'N, 143°28'E
01°35'N, 142°03'E
01°40'N, 142°03'E
01°43'N, 142°03'E
00°55'S, l46°35'E
00°57'S, 146°38'E
01°05'S, 147°01°E
Ol 0 16'S, 147°00'E
01°2l'S, 147°05'E
01°22'S, 147°06'E
Ol 0 27'S, 147°2l'E
01°23'S, 147°22'E
Ol 0 15'S, 147°28'E
Ol 0 25'S, 148°14'E
04'08'S, 154°17'E
00°04'N, 162°27'E
00°55'N, 165°24'E
00°47'N, 165°27'E
00°37'N, 165°35'E
00°30'N, 165°38'E
06°06'S, 156°53'E
06°07'8, 156°56'E
06°05'S, 156°07'E
03°16'S, 153°39'E
00°56'S, 142°03'E

Position

07: 15
12: 10
15:20
15: 10

06:45
08:25
14:20
15: 00
15: 20
14: 35
15: 1006: 1509: 15
10: 55
11: 20
14: 15
15: 1516:30
09: 10
10: 1008: 35
10: 35
12: 15
14: 40
16: 1006:50
07:50
10: 55
10: 4508: 00

Time

29.0
29.2
28.8
29.7

28.8
29.2
30.0
30.0
30.0
29.0
29.0
29.0
29.0
28.8
28.8
29.0
29.0
29.(}
29.0
29.2
29.1
28.5
28.7
29.0
29.0
29.6
29.5
29.3
30.2
28.8

Surfacetemperature (°C)

8
19
15
12

1
2
2
1
1
1
1
1
6
1
1
2
l
7
2
3
1
8
2
1
18

Schoolsize

One female with a calf was found.
One female with a calf was found.
Two females with a calf were found.
Many remoras attached to the back of calf.

Four females with a calf were found.
Together with two Risso's dolphins .

One female with a calf was found.
One female with a calf was found.
One female with a calf was found.
With many sea birds and a school of bonito.
With many sea birds and a school of bonito.
With many seabirds and a school of bonito.

One female with a calf was found.

......

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tj

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With many seabirds and a school of bonito.
W'ith many sea birds and a school of bonito.
With many seabirds and a school of bonito.

~-

Comments

O:>""

Many remoras attached to the back of this animal.

SIGHTING RECORDS OF CETACEANS DURING THIS SURVEY

~·

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"'

~~

-""'~
.....

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Q

~~

54
55
56
57
58
59
60
61
62
63
64

31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53

"

"

"

"
"
"
"
Stenella longirostris

"
"

,,

"

"
"
"

"

"

"
"
"
Stenella attenuata

"
"
"
"

"
Stenella coeruleoalba

"
"

"
"
"
"
"

2 III '76
5 Ill '76
5 III '76
6 III '76
6 III '76
7 III '76
16 III '76
2 II '76
2 II '76
12 II '76
14 II '76

22 II '76
24 II '76
29 II '76
29 II '76
29 II '76
29 II '76
3 III '76
JO III '76
21 I '76
23 I '76
5 III '76
16 III '76
16 III '76
16 III '76
16 III '76
17 III '76
25 I '76
27 I '76
14 II '76
16 II '76
I III '76
1 III '76
2 III '76
06°02'S, 159°15'£
04°20'S, 155°5l'E
03°4s's, 155°04'E
03°25'S, 153°44'E
03°06'S, 153°3l'E
01°49'S, 151°53'£
26°4l'N, 143°07'£
03°03'N, 141°57'£
03°1l'N, 142°07'£
04°55'S, 152°56'£
02°09'S, 157°45'E

00°44'S, 166°37'E
08°5l'S, 163°50'E
09°!l'S, 159°56'E
09°l!'S, 159°56'E
09°JO'S, 159°57'E
09°lO'S, 159°57'£
06°14'S, 157°08'E
02°17'N, 151°34'£
30°47'N, 138°33'£
23°2l'N, 138°27'£
04°02'N, 155°4l'E
25°23'N, 143°04'£
25°56'N, 143°06'E
26°40'N, 143°07'£
26°42'N, 143°00'E
28°29'N, 142°30'£
14°50'N, 138°28'£
04°52'N, 138°35'£
01°09'5, 157°49'£
02°20'S, 159°49'£
08°20'S, 160°00'£
08°09'S, 160°04'£
06°37'S, 159°35'£
16: 35
10: 15
17: 10
09:35
12: 15
10: 15
16:40
13: 35
15: 50
16:25
10: 05

13:30
16:00
17: 30
17: 30
18: 35
18: 48
17: 2506:20
17: 20
09: 15
13: 3507: 0509:45
15: 05
17: 00
11: 1007:55
16: 30
16: 0509: 10
11: 00
13: 15
10: 00
29.5
30.l
30.0
30.2
30.4
29.8
22.0
29.5
29.2
29.6
29.0

28.8
28.7
28.8
28.8
28.8
28.8
29.2
29.6
18.2
22.4
30.5
22.6
22.2
22.0
22.0
20.6
27.4
29.l
29.8
29.0
29.l
29.4
29.0
400-500
30-40
100-150
70-80
50-60
40-50
100-15040-50
30-40
150-200
40-50

JO
26
40-50
10-20
400-500
30-40
50-60
40-50
20-30
100-150
10-20
10-20
50-60
20-30
20-30
150-200
500-600

28
16~

Several females with a calf were found.

Continued ...

One specimen (specimen No. 13) was collected.
One specimen (specimen No. 11) was collected.

Several females with a calf were found.

One specimen (specimen No. 7) was collected.
Several females with a calf were found.
One specimen (specimen No. 5) was collected.
Five females with a calf were found.
One specimen (specimen No. 8) was collected.
Several females with a calf were found.
Serveral females with a calf were found.

Together with a school of Pseudorca crassidens.
One specimen (specimen No. 6) was collected.

......

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Several females with a calf were found.
Two females with a calf were found.
Three females with a calf were found.
Three females with a calf were found.

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"
"
"

69
70
71
72

27 I '76
6 III '76
19 II '76
30 I '76

Pseudorca crassidens

88
89
90
91

. "'

<.;

~ ~~

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~~

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~~

Orcinus area
Grampus griseus"

20 II '76

Peponocephala electra

87

~
~~

~

~

04°52'N, 138°35'E
02°37'S, 153°0l'E
02°2l'N, 164°08'E
00°56'S, 142°03'E

01°43'N, 164°53'E

03°00'N, 141°55'E
01°43'N, 164°53'E

01°33'N, 142°04'E

1 II '76

2 II '76
20 II '76

06°3l'S, 157°26'E
05°10'S, 156°34'E
04°54'S, 156°1l'E
03°48'S, 155°18'E
02°55'S, 153°22'E
00°25'N, 153°09'E
00°56'N, 143°30'E
00°23'N, 165°37'E
01°55'S, 148°53'E
l0°33'S, 160°33'E
23°15'N, 138°27'E

3 III '76
4 III '76
5 III '76
5 III '76
6 III '76
9 III '76
31 I '76
21 II '76
7 II '76
26 II '76
23 I '76""

07°53'S, 160°05'E
07°52'S, 160°04'E
07°4l'S, 159°55'E
06°34'S, 158°08'E

1 III '76
1 III '76
1 III '76
3 III '76

85
86

"

01°18'N, 165°13'E
00°52'S, 166°42'E
07°18'S, 164°34'E
08°50'S, 159°52'E

Position

20 II '76
22 II '76
24 II '76
1 III '76

Date

~

84

" hosei
Lagenodelphis

Tursiops sp.

"

Stene/la sp."

"
"
"
"
"

"

"
"
"..

65
66
67
68

73
74
75
76
77
78
79
80
81
82
83

Species

Sighting
No.

16: 30
16:45
15: 1508: 00

12: 10

10: 30
12: 10

13: 10

14: 25
18: 1007: 15
15: 45
13: 4507:25
17:55
18: 20
17: 15
14: 15
10: 00

16: 00
16:25
18: 00
09:20

16: 45
15: 50
07:00
07:35

Time

TABLE I.

29.1
30.8
28.7
28.8

28.7

29.5
28.7

30.0

29.9
30.6
30.0
30.6
30.4
29.4
30.0
29.0
28.8
28.4
22.9

29.5
29.5
29.5
29.0

28.7
29.1
28.6
28.8

Surfacetemperature (°C)

Continued.

10
20-30
9
2

20

40-50
400-500

40-50

200-300
20-300150-200
150-200
500-600
20-30
10-20
10-20
200-300
10-20
200-300

80-100150-200
500-600
50-100100-15030-40
150-200
30-40

Schoolsize

Several females with a calf were found.
Together with a school of Peponocephala electra.
One specimen (specimen No. 3) was collected.
Together with a school of Lagenodelphis hosei.
Together with a school of Stenella attenuata.
Several females with a calf were found.
Two females with a calf were found.
Together with a school of Physeter catodon.

One specimen (specimen No. 1) was collected.
Several females with a calf were found.
One specimen (specimen No. 2) was collected.
Several females with a calf were found.

One specimen (specimen No. 4) was collected.

Several females with a· calf were found.
Several females with a calf were found.

Three females with a calf were found.
One specimen (specimen No. 10) was collected.
Several females with a calf were found.
One specimen (specimen No. 15) was collected.
Two females with a calf were found.
Several females with a calf were found.
Four females with a calf were found.
One specimen (specimen No. 14) was collected.
One specimen (specimen No. 9) was collected.
Several females with a calf were found.
One specimen (specimen No. 12) was collected.

Comments......

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co

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~-

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~

if

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.<=> ~

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98
99
100
101
102
103

92
93
94
95
96
97

"
"

"
Feresa attenuata:(iphius cavirostris

Globicephalamacrorhynchus"

00°27'N, 143°4l'E
00°39'N, 143°42'E
01°20'N, 142°08'E
05°59'8, 157°04'E
14°04'N, 144°56'E
00°48'8, 142°14'E
25°58'N, 143°06'E
02°48'8, 153°16'E
00°54'N, 143°29'E
01°20'N, 142°09'E
01°22'N, 163°04'E
02°06'N, 164°33'E

31 I '76
31 I '76
1 II '76
4 III '76
13 III '76
30 I '76

16 III '76
6 III '76
31 I '76
1 II '76
19 II '76
20 II '76

29.7
30.0
30.0
30.2
27.6
29.2
22.2
30.6
29.9
30.0
28.5
28.6

10: 20
12: 50
11: 40
11: 55
13: 00
12: 40
10: 20
14: 50
15:35
11: 25
06:30
09:20

30-40
150-200
3
3
1
1

10
10
10
20-30
8
9

(JI

o;

0

......

":I

0......

~

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!:""'

0

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0

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>-'l

z

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0

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0

MIYAZAKI AND WADA

186

170°E
150°E
rr-r...,.-,-,...,...,-r-rrri-rr.,....,-rri-rr.--r,--r-rro...,-rr-,,--,n-r,...,.,10°N

19

••

...

O A

- oo

Nauru I.

Fig. 2. Sighting records of Balaenoptera edeni and Physeter catodon.
triangles indicate B. edeni and P. catodon, respectively.

Circles andschool (sighting No. 26) were found together with two Risso's dolphins, Grampus
griseus. Although many remoras were attached on the backs of two calves in
one school (sighting No. 27), we did not observe any sucking fish on the backs of
the adults or subadults in this school.

Stenella coeruleoalba
Striped dolphin, Stenella coeruleoalba is common along the eastern coast ofJapan (Miyazaki et al., 1974). Eight schools of striped dolphin were found. Six
schools (75%) had less than 100 dolphins (Fig. 5). The maximum school size
was estimated to be 400-500 dolphins. Several females with calf were observedin five schools (Table 1). Estimated body lengths of these calves were 110-140
cm. Although several dolphins from two schools (sighting Nos 43 and 46) approached the bow of the vessel, but no dolphin from the other schools approached
the bow.
Striped dolphins were found between from 04°02'N to 30°47'N latitude (Fig.
3), and sea surface temperature ranged from 18.2 to 30.5°C (Table 1). Especially
6 schools (75%) were found between 20°N and 30°N latitude. On the other hand,most of spotted dolphins and all of spinner dolphins were found between l0°S and
l0°N latitude in this survey as indicated in the latter part of this report. Considering from these data, striped dolphins seem to have larger distribution in thenorthern Pacific than spotted and spinner dolphins. According to Miyazaki et al.
(1974), spotted dolphins are found in warmer area than striped dolphins. This
supports our result.
Stenella attenuata
Spotted dolphin, Stenella attenuata is common in the coast of Japan (Miyazaki
et al., 1974), in the tropical Pacific (Dawbin, 1966) and in the eastern PacificSci. Rep. Whales Res. Inst.,

No. 30, 1978.

CETACEAN IN WESTERN TROPICAL PACIFIC

187

170°E

30°N
0

s
8

0

20°N

A

1 0°N

A

0

a•

A

c
A

•

•

~,a

a

d· ~<t:,.·•'lt.

~

••

"""

QO

<;;;,

1 QO $

Fig. 3. Sighting and catch records of Stenella spp. Circles, triangles, and squares
mean S. coeruleoalba, S. attenuata, and S. longirostris, respectively. Open and shaded
symbols are sighting and catch records, respectively.

(Perrin, 1975). Perrin (1975) reported that there are at least two races of spotted
dolphin in the eastern Pacific.
Fourteen schools of spotted dolphin were found. Nine schools (65%) wereless than 100 dolphins (Fig. 5 ). The maximum school size was estimated at about
500-600 dolphins. Several females with calf were observed in three schools (Table
1). Although some spotted dolphins off the Pacific coast ofJapan often approached
the bow of ship, in this survey no spotted dolphin did so.
Spotted dolphins were found between from 08°20'S to 26°4l'N latitude (Fig.
3), and sea surface temperature ranged from 22.0 to 30.2°C. Between 10°S and
l0°N latitude 12 schools (86%) were found. One school of spotted dolphinsighting No. 47) was found between 10°N and 20°N, and another (sighting No.
60) between 20°N and 30°N latitude. On the other hand most of striped dolphin
were found between 20°N and 30°N, and all of spinner dolphin were found between 10°S and l0°N latitude in this survey. From these information, it can be
Sci. Rep. Whales Res. Inst.,
No. 30, 1978.

MIYAZAKI AND WADA

188

150°E

•L

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0/ z .
ovL

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Pe

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10°5

Fig. 4. Sighting (oen circle) and catch (closed circle) records of small cetaceans.
Pc., 0., Gg., T., L., Pe., Gm., F., and Z mean Tursiops sp. Lagenodelphis hosei,
Peponocephala electra, Pseudorca crassidens, Orcinus orca, Grampus griseus, Globicephalamacrorhynchus, Feresa attenuata, and Z,iphius cavirostris.

said that spotted dolphin may have larger distribution m the western northern
Pacific than spinner dolphin.
Four specimens were collected from four different schools (Table 2). These
specimens consist of one female and three males. As the left ovary of the female.
(specimen No. 5) was heavier than the right, and the diameter of Graafian folliclesof the left ovary became bigger, the female seems to be in the early stage of ovulation. Two animals (specimen Nos 6 and 7) showed no spermatozoa in the tissueof the testes but one (specimen No. 8) did.

Stenella longirostris
Spinner dolphin, Stenella longirostris is common in the eastern Pacific (Perrin,1975), but little is known about spinner dolphins in the western Pacific.
Eighteen schools of spinner dolphin were found. Half of these schools had
Sci. Rep. Whales Res. Inst.,
No. 30, 1978.

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Stenella attenuata

Stenella attenuata

Stenella longirostris

Stenella longirostris

Stenella longirostris

Stenella longirostris

5

6
7
8
9

JO

11

12
13
14
15

Stenella longirostris

Stenella longirostris

Stenella longirostris

Stenella attenuata

Stenella attenuata

Peponocephala electra

49
51
54
72
66
63
73
62
71
68

53

84
87
81

Male

Male

FemaleFemaleFemaleFemaleFemale

Male

Male

Male

FemaleFemaleFemaleMale

Female83

Lagenodelphis hosei

Lagenodelphis hosei

Sex

Sighting
No.

Species2
3
4SpecimenNo.

TABLE 2.

173
176
215
152
158
167
189
191
181
187

178

0.2
0.5
0.7
6.4
1.3

1.1

0.9
3.0

183.5
208
238

0.2
0.5
0.5
0.8
1.3

0.4

0.8
2.7

1.3

320
620

7.3
4.2
200

8.6

3.0

231

250
620

7.1
4.3
200

8.6

R.

L.

L.

R.

Weight oftestes (g)Weight ofovaries (g)Bodylength
(cm)

0-0
0-0
0-0
1-1
0-6

0-0

0-0
0-1

0-0

L.

0-0
0-0
0-0
0-0
0-3

0-0

0-0
0-4

0-0

R.

No. ofcorporaMatureMatureResting

Pregnant

Immature

Immature

Immature

MatureImmature

Immature

Immature

Lactating

Immature

Immature

Immature

Sexualcondition

LIST OF SPECIMENS CAUGHT DURING THIS CRUISE

Body size of the foetus is 75 cm

Diameter of maximum Graafian follicle is 3 mm

Diameter of maximum Graafian follicle is 3 mmComments

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MIYAZAKI AND WADA

190

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0
30

5

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400

600

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100
Eottler:ose

i;oo

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100

600

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400

Fraser's

600
l:elon-'neaded

0

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killerKillerwhale

20

Risso' sdolphin2

Short-finned

pilot

Pygmy

whale

0

;:J

z

0

10

0

0

10

20

0

2 00

killer

J;OO

2

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40

2

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1 00

.5 0

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t-ihale

100

50

2
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0

beakedwhale

10

5 c h 0 0 l

s i z eFig. 5. Frequency of school size in cetaceans. Shaded and open areas are schools
with several female and calf and schools without it, respectively.

less than 100 dolphins (Fig. 5). The maximum school size was estimated at about
500 to 600 dolphins. Several females with calf were observed in nine schools(Table 1). No spinner dolphin approached the vessel during this survey.
Spinner dolphins were found between from 08°50'S to 03°ll'N latitude(Fig. 3), and sea surface temperature ranged from 28.6°C to 30.6°C. Consideringfrom sighting records of striped, spotted, and spinner dolphins in this survey, spinner
dolphin seems to have the most limited distribution in the western north Pacificamong these three species of the genus Stenella.
Seven specimens were collected from seven different schools (Table 2). These
specimens consist of five females and two males. Based on biological examinationsof ovaries, mammary gland, and uterus, sexual condition of these females were
determined as indicated in Table 2. Pregnant female (specimen No. 12) hadaSci. Rep. Whales Res. Inst.,
No. 30, 1978.

CETACEAN IN WESTERN TROPICAL PACIFIC

191

foetus of 75 cm in body length. According to Perrin et al. (1977) estimated average
length at birth of the spinner dolphin in the eastern Pacific is 77 cm. Therefore,
it seems that the foetus collected was probably about term. Two males (specimenNos 14 and 15) showed spermatozoa in the tissue of the testes.

Stenella sp.
On 31 January a school of approximately 10-20 dolphins, and on 21 Februarya school of about 10-20 dolphins were found. As these dolphins were found latein the evening, it was impossible to identify the species. However, we thoughtthese dolphins probably to be Stenella sp. based on body size, the shape of the snout
and the dorsal fin, and their swimming behavior.
Tursiops sp.
On 7 February, a school composed of approximately 200-300 bottlenose dolphins was found (Fig. 4). Sea surface temperature was 28.8°C. Several bottlenose
dolphins approached the vessel. A lactating female was collected from them
(Table 2). In this animal greyish speckles were characteristically found on theventral portion between the umbilicus and genital region. Comparing with adultfemales of T. gilli off the Pacific coast of Japan, this animal is shorter in bodylength and higher in body height, and it appears to be thickset than adult femalesof T. gilli. One open pit was observed on the left lateral portion above the flipper
and under the dorsal fin, respectively. Several whale lice were attached to theinside of these two open pits. On 26 February a school composed of about 10-20
bottlenose dolphins were found (Fig. 4). Sea surface temperature was 28.4°C.
Lagenodelphis hosei
Fraser's dolphin, Lagenodelphis hosei is rare all over the world. Recently
Perrin et al. (1973) reported the discovery of the species in tropical and subtropicalareas, and Tobayama et al. (1973) described specimens from the western North
Pacific.
On 23 January a school composed of approximately 200-300 dolphins wasfound (Fig. 4). This school was consisted of two small schools (100-150 individuals), and several members of one small school approached the bow of thevessel but the other did not. In the small school at least a group of ten, eight,
and seven individuals, three groups of six ones, two groups of five ones, and a pairof adult female and calf were observed. The similar school formations is found in
S. coeruleoalba (Miyazaki and Nishiwaki 1978). One specimen (TK 451) was collected from this school with harpoon. On 1 February a school composed of about
40-50 dolphins with several females with calf were found (Fig. 4). In this school
no dolphin approached the bow of the vessel, but one spec imen (TK 452) was
captured from the school with shotgun. This specimen showed no spermatozoa inthe tissue of the testes. On 2 February a school of about 40-50 dolphins was found(Fig. 4). Any dolphin did not approach the bow of the vessel. No dolphin was
captured. On 20 February a school of approximately 400-500 dolphins was foundSci. Rep. Whales Res. Inst.,
No. 30, 1978.

192

MIYAZAKI AND WADA

together with a school of PejJonocephala electra which was composed of about 20
dolphins (Fig. 4). This shows that Fraser's dolphin may rarely mix with otherspecies. Several leaping dolphins were observed, but no dolphin was captured.
Sea surface temperature at sighting areas ranged from 22.9°C to 30.0°C.

Peponocephala electra
According to Perrin (1976) and Bryden et al. (1977), Melon-headed whale,
Peponocephala electra appears to be distributed in tropical and warm temperatewaters in the world. On 20 February a school composed of approximately 20
dolphins with several females with calf were found together with about 400-500
Fraser's dolphins (Fig. 4). Sea surface temperature was 28.7°C. One immature
female was collected from this school (Table 2). In this animal several whale
lice attached to the ventral portion between flippers, around the mammary glandand the umbilicus, and under the right eye.
Pseudorca crassidens
On 27 January a school composed of approximately 10-20 false killer whales
were found together with about 10-20 spotted dolphins (Fig. 4). Sea surface
temperature was 29.1°C. Although a false killer whale was shot and killed withshotgun, the carcass was lost at sea. The estimated body length of this carcass
suggests that this animal is subadult one. This school was composed of several
groups of two or three animals. Distance between groups ranged from 10 to 50 m.
On 6 March a school of approximately 20-30 false killer whales with several pairsof female with calf was found (Fig. 4). Sea surface temperature was 30.8°C.
Orcinus orca
Although the killer whale, Orcinus orca is found primarily in polar and temperate regions, the species is sometimes found in the tropical areas. On 19 February a school of 9 killer whales was found (Fig. 4). Sea surface temperature was
28. 7°C. Based on body size and shape of the dorsal fin of the animals, and their
behavior this school seemed to be composed of 3 adult males, 2 adult or subadultwhales, and 2 females with calf. It is noted that three adult males were all foundon the outer edge of the school. Estimated body lengths of adult males, adultfemales, and calves were 7-9 m, 4-6 m, and 2-3 m, respectively.
Grampus griseus
Risso's dolphin, Grampus griseus is common in Pacific Ocean, but there are
few records of the species in the western tropical Pacific (Dawbin, 1966). Six
schools of the species were found. Five schools (85%) had less than 10 animals.
The maximum school size was about 20-30 animals. One school (sighting No.
91) was found together with 18 sperm whales, Physeter catodon. Rissos's dolphinswere found between 20°N and 30°N latitude (Fig. 4) and sea surface temperature
ranged from 27.6°C to 30.0°C.
Sci. Rep. Whales Res. Inst.,
No. 30, 1978.

CETACEAN IN WESTERN TROPICAL PACIFIC

193

Globicephala macrorhynchus
On 30 January a school of approximately 10 shortfinned pilot whales wasfound (Fig. 4). Sea surface temperature was 29.2°C. Based on body size and theshape of the dorsal fin, at least two animals of this school seemed to be adult males.
On 16 March a school of about 30-40 shortfinned pilot whales was found (Fig. 4).
Sea surface temperature was 22.2°C. Judged from body size and the shape of thedorsal fin, it seems that there were some adult males in the school.
Feresa attenuata
On 6 March a school of approximately 150-200 pygmy killer whales, wasfound (Fig. 4). All members of the school were well united in their behaviour.
Sea surface temperature was 30.6°C. Although no specimen of the species werecollected, these animals were identified as Feresa attenuata by the following threereasons. I) Body size of all animals in the school were about 2.5 m-3.5 m. 2)
These animals were of slender bodies with round head and no beak. 3) Their
dorsal fins lead edgeslopes backwards, the rear margin is slightly concave, and thetip is pointed.
Ziphius cavirostris
Since Cuvier's beaked whale, ZiPhius cavirostris is too nervous about the vessel
and always dive into the sea for 30-40 minutes before approaching, it is difficult
to identify the species by sighting. During their jumping above the sea, however,Cuvier's beaked whales were identified by the body size, the position of the dorsal
fin, and the shape of the head.
Cuvier's beaked whales were observed four times (Fig. 4). Two sightings
were of single animal and three whales were found in each of the other two pods.
ACKNOWLEDGMENTS

We thank the captain and other crew of the Miwa-maru for their cooperation, and
Drs S. Ohsumi, Y. Fukuda and I. Ikeda of the Far Seas Fisheires Research Laboratory for giving us chance for this study. Drs T. Kasuya, K. Mizue and
T. Kajiwara of the Ocean Research Institute, and Professor M. Nishiwaki of
University of the Ryukyus are acknowledged for their kind help during this study.
We are indebted to Dr R. L. Brownell of the Smithsonian Institution who readdraft of manuscript and gave us valuable suggestions.
REFERENCES
BRYDEN, W. F., W. H. DAWBIN, G. E. HEINSOHN, and D. H. BROWN, 1977. Melon-headed whale, Pepotwcephala electra, on the east coast of Australia. J. Mamm., 58: 180-187.
DAWBIN, W. H., 1966. Porpoises and porpoise hunting in Malaita. Australian Natural History, 15 (5):207-211.
MASAKI, M., 1972. Tagging investigation of whale in Ogasawara and Mariana Islands. Geiken Tsushin,
249: 35-42 (in Japanese)
Sci. Rep. Whales Res. Inst.,
No. 30, 1978.

194

MIYAZAKI AND WADA

MIYAZAKI, N. and M. NISHIWAKI, 1978. School structure of the striped dolphin off the Pacific coast of Japan.
Sci. Rep. Whales Res. Inst., 30; 65-115.
MIYAZAKI, N., T. KAsuvA, 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.
PERRIN, W. F., 1975. Distribution and differentiation of populations of dolphins of the genus Stenella in theeastern tropical Pacific. J. Fish. Res. Board Can., 32 (7): 1059-1067.
PERRIN, W. F., P. B. BEST, W. H. DAWBIN, K. C. BALCOMB, R. GAMBELL and G.J.B. Ross, 1973. Rediscovery
of Fraser's dolphin Lagenodelphis hosei. Nature, 241 (5388): 346-350.
PERRIN, W. F., 1976. First record of the Melon-headed whale, Peponocephala electra, in the eastern Pacific,
with a summary of world distribution. Fish. Bull., 74: 457-458.
PERRIN, W. F., D. B. HOLTS, and R. B. MILLER, 1977. Growth and reproduction of the eastern spinner
dolphin, a geographical form of Stenella longirostris in the eastern tropical Pacific. Fish. Bull., 75: 725-

750.
ToBAYAMA, T., 1\1. NISHIWAKI, and H. C. YANG, 1973. Records of the Fraser's sarawak dolphin (Lagenodelphis hosei) in the western North Pacific. Sci. Rep. Whales Res. Inst., 25: 251-263.
WADA, S., 1975. Tagging investigation of whales in the south-western areas of the NorthPacific. Geiken
Tsushin, 284: 27-34. (in Japanese)

Sci. Rep. Wheles Res. Inst.,
No. 30, 1978.

CETACEAN IN WESTERN TROPICAL PACIFIC

EXPLANATION OF PLATESPLATE I

Fig. I. Bryde's whale, Balaenoptera edeni, at sea in 00°55'8, !46°35'E, on February
5, 1976. Note three ridges on the snout.
Fig. 2. A part of school of sperm whales, Ph_yseter catodon, at sea in 02°l 7'N, 151°34'E,
showing side by side in the interval of 2-3 m between whales, on March 10, 1976.
Fig. 3. An adult male killer whale, Orcinus orca, at sea in 02°2l'N, 164°08'E, on
February 19, 1976.
Fig. 4. A part of school of Fraser's dolphin, Lagenodelphis hosei, at sea in Ol 0 43'N,
164°53'E, on February 20, 1976.
PLATE II
Fig. 1. Lateral view of immature female Peponocephala electra, 208 cm long, taken at
sea in 01°43'N, 164°53'E, on February 20, 1976.
Fig. 2. Lateral view of the cephalic region of the same specimen.
Fig. 3. Ventral view of the cephalic region of the same specimen.
Fig. 4. Anterior view of the oral region of the same specimen, showing whitish
skin on the lip margins and palatine portion.
PLATE III
Fig. I. Lateral view of lactating female Tursiops sp., 238 cm long, taken at sea in
01°55'8, 148°53'E, on February 7, 1976.
Fig. 2. Ventral view of the same specimen, showing greyish speckles on the ventralside.
Fig. 3. Lateral view of the cephalic region of the same specimen.
Fig.4. Ventral view of the genital region of the same specimen.

Sci. Rep. Whales Res. Inst.,
No. 30, 1978.

195

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