CATCH OF THE CUVIER'S BEAKED WHALES OFF JAPANIN RECENT YEARSMASAHARU NISHIWAKI* AND NOBUO OGURO*ABSTRACT

We analysed Cuvier's beaked whales (.<)phius cavirostris) caught off the coastof Japan between 1965-70. In most cases they were caught in waters deeper
than 1000 m. They eat food abounding in the surrounding waters. 70% of
189 whales were males. This tendency was the same every year, and was also
reported by Omura et al. (1955). 87 % of the whales caught were mature, andthe average body length of both sexes was larger than between 1948-52. Ifan
annual quota of 30-50 animals were to be observed, this probably would notendanger the ,Ziphius stock in the western North Pacific.

The ' smaller whale ' whaling industry of Japan has been catching a considerable
number of Cuvier's beaked whales (Ziphius cavirostris) along with Minke whales(Balaenoptera acutorostrata) and Baird's beaked whales (Berardius bairdi). Omura et al.
(1955) reported on the Cuvier's beaked whale caught off the coast of Japan between
1948-52. The total catch during that period was 85. Ziphius is the least valuable ofthe three to the whaling industry, and hence there is less pressure on it than on theother two. It is evident that coastal whaling operations have diminished and thenumber of catcher boats have decreased in recent years. There must, therefore,
have been some change in the different relative rates of catch of Ziphius and the othertwo species, while the total catch has been decreasing. Our discussion here concerns Ziphius caught between 1965-70. The data was extracted from the report by
the Fisheries Agency of the Japanese Government on the harvest of the smaller whales
during 1965-70.
ANALYSIS OF CATCH

The areas of the whaling operation and the precise positions of catch are shown inFig. 1. The coastal waters are divided in the same way as by Omura et al. (1955).
Ziphius whales has been taken in each of the seven areas except for VI, in which,nevertheless, Omura et al. has some catch records. The catch positions are mostly on
the 1000 m contour or in deeper waters, and are most abundant in areas I and II.
The catches are particularly numerous in Area I on account of the indented coastline
and the concomitant meandering 1000 m contour.
Table 1 and Fig. 2 show the size distribution of the whales caught. Table 2
indicates the monthly catch in each area. The total catch was 189, of which 132
were males (70%) and 57 were females (30%). This rate is almost the same as re-* Ocean Research Institute, University of Tokyo, Tokyo.
Sci. Rep. Whales Res. Inst.,
No. 24, 1972, 35-41.

36

NISHIWAKI AND OGURO\OKHOTSK SEA' \I'45'Nt--~~~~~~~~~~--~~,~-r~~~--\AREA NIII"o I\.

HOKKAIDOAREAV/--- ____' \ .....

\\.... ,,/'\Q)

AREAill

1C!:.=SEA of JAPAN'\\~\~','°'ov\40'Ni-~~~~~~~~~~~~~7,_,.,.

I£:I

10,,,,,,.- .... ItO
tO, .....

I
I

I

[.

I/.' ...
.
.. ...
..... :·:,,,:;·.::·'I

I

AREA VI

I
I[~//,,,/'/I',, ....

,,,.,,."""'

I

I''/'

/ ' 'I/•1••

I

I/,/ AREAII'I'oII

PACIFIC OCEAN

I/II/35'N/'·
/~-­

..

AREA I

135'E
Fig. 1.

140'E

145'E

Position of catch of <:_iphius cavirostris off Japan, 1965-1970.

Sci. Rep. Whales Res. Inst.,
No. 24, 1972.

CATCH OF THE CUVIER'S BEAKED WHALE
TABLE I.

Month37

NUMBER OF CATCH OF Z,IPHIUS AVIROSTRIS ACCORDING TOTHE MONTHS AND AREAS, 1965-1970.
Area I

Area II

Area IV

Area VII

Total~,.-"--.

,.---_~~

Male Female

Male Female

Male Female

Male Female

Male Female

218
11Jan.
Feb.
Mar.
Apr.
May
June
JulyAug.
Sept.
Oct.
Nov.
Dec.
Total

641074206501080222020131282075436634104123416120030203300518
131072151912228132**

0010210802207786557* A sex unidentified individual is excluded.
40

__II=

~.!::

Male
Female30...,..c:llO::Iroc..>I/)~ro..c:

20

3:

....0
....
Q)

..c

E::Iz

10

13

14

15

16

17

18

19

20

21

2223

Body length in feetFig. 2.

Size distribution of Z,iphius cavirostris caught, 1965-1970.

ported by Omura et al. The catch in each area was as follows: in area I 106 werecaught, 70 in II, 3 in IIland 12 (including 2 individuals of unidentified sex) in VII.
In Area I, 64 were caught between Jan-June and 42 between Aug-Dec, while area II,
64 of the year's total of 70 were caught between Aug-Dec. In area IV only 3 werecaught between May-June, while in area VII records are scattered throughout theSci. Rep. Whales Res. Inst.,
No. 24, 1972.

NISHIWAKI AND OGURO

38

TABLE 2. AVERAGE BODY LENGTH AND SEX RATIO OF Z/PHIUS
CAVIROSTRIS CAUGHT DIVIDED BY AREAS AND MONTHS, 1965-1970.
Area I

Area II

MaleFemale

Jan.-June
Average length
Sex ratio

20.1
65.5

19.8
34.4

Aug.-Dec.
Average length
Sex ratio

18.9
54.8

18.l
45.2

MaleFemale

19.5
74.1

19.1
21.9

first six months of the year.
The whales caught in the above mentioned periods are presented in Table 2
together with the average body length of both sexes and the sex ratio. According toabove mentioned data, the abundant catch in Area I between Feb-May may consistof adult males going north to chase after adult females. The whales caught inArea I in the other months may be younger males searching for food. The abundantcatch in Area II between Aug-Dec seems to consist of males migrating south, some ofthem possibly in the company of adult females.
SIZE DISTRIBUTIONAs seen in Fig. 2 and Table 3, the greatest body lengths of all the individuals caught
were 23 feet for males and 22 feet for females. The most common body length forboth sexes was 20 feet, while most of the catch was in the length range 18-21 feet.
There are four species of Mesoplodon in the western North Pacific: M. stejnegeri,
M. densirostris, M. ginkgodens and M. carlhubbsi. We found some suggestions ofTABLE 3.
Body
lengthin feet
131415161718
1920
212223Total
Sex ratio
Maturity

SIZE DISTRIBUTION OF Z,IPHIUS CAVIROSTRIS CAUGHT, 1965-1970.
NumberMale

Number

Percentage
Total

6917
1745
30
74
3
10
10
18
8
2

*10
1227
27
*63
38
9132
69.8

57
30.2

189
100.0

MaleFemale

Total

1.8
1.8

0.5
0.5

7.0
5.3
17.5
17.5
31.6
14.0
3.5

4.56.8
12.9
12.9
34.1
22.7
5.3
0.8
100.0

100.0

5.3
6.4
14.3
14.3
33.3
20.1
4.8
0.5
100.0

88.6

84.2

87.3

* A sex unidentified individual is excluded.

Sci. Rep. Whales Res. Inst.,
No. 24, 1972.

CATCH OF THE CUVIER'S BEAKED WHALE
TABLE 4.
ArealYear---~

Male Female
1965
1966
1967
1968
1969
1970
Total

14101994965

39

ANNUAL CATCH OF Z,IPHIUS CAVIROSTRIS AND THEIR SEXRATIO ACCORDING TO AREAS, 1965-1970.
Area II,.-.____,

Area IV

Area VII~~..-"'----.

Male Female

Male Female

Male Female

Male Female

MaleFemale

47
1729
2199132

78.3
63.0
64.4
72.4
69.2
60.0
69.8

21.7
37.0
35.6
27.6
30.8
40.0
30.2

78
1262641

28
67
10
3

62
422354

16

30

02
l3
22

*O

100

0
0
00

Total

13JO
16
84
657

Sex ratio~* Two sex unidentified individuals are excluded.
Mesoplodon in the discarded bones around the whaling stations where ,Ziphius areprocessed, but there has been no report of Mesoplodon being caught by these companies. Therefore, the data in Fig. 2 for ,Ziphius may include some Mesoplodon, but
the percentage of the latter is so small that it could exert no significant effect on thefigures.
The catch for each year is indicated in Table 4. Although the total catch of,Ziphius has been decreasing year by year, this may be partly due to reduced hunting
effort rather than to an actual population decrease.
FOOD

The stomach contents varied according to the area in which the animals werecaught, as shown in Fig. 3. The food found in the stomachs of the animals fromArea I consisted mainly of deep-sea fish, but that from animals in Areas II and VII
was exclusively squid. There was no food report from Area V. Therefore, deep-sea
fish must have been the main food in waters deeper than 1OOO m, while squid must bethe main food in the shallower waters. As seen in Fig. 3, deep-sea fish were often
found in the animals from Area I all through the year, but squid was sometimes
found in Area II from Nov-Jan. This evidence suggests that the whales may eat
whatever fish are abundant in the waters where they happen to be.
CONCLUSION

Our analysis suggests that Cuvier's beaked whale (,Ziphius cavirostris) has been beingcaught throughout the year, abundant harvests being taken in Feb., Sept. and Nov.
The greatest body length in our sample is 23 feet (male) and 22 feet (female).
The data also suggest that the majority of ,Ziphius whale were caught in waters deeper
than 1000 m. The variety of food in the stomachs examined shows that the ,Ziphius
whales, like other smaller whales, eats the food most common in its surrounding
waters. Both sexes of ,Ziphius seem to be about 18 feet in body length when theyattain sexual maturity. 87% of the whales caught were mature, and the average
Sci. Rep. Whales Res. Inst.,
No. 21, 1972.

NISHIWAKI AND OGURO40•

OKHOTSK SEA

Deep-sea fishes

45°N

No Squid

SEA of JAPAN0PACIFIC OCEAN
0000 00II

35°N

135°E

Fig. 3.

140°E

145°E

Position of catch of <:,iphius cavirotris with stomach contents, 1965-1970.

body length of both sexes from this data are greater than those in the data of Omura
et al.
Considering that the number of new whaling boats has been decreasing conSci. Rep. Whales Res. Inst.,
No. 24, 1972.

CATCH OF THE CUVIER'S BEAKED WHALE

41

tinually, possibly, if the population remains in its apparently stable condition as atpresent, this industry may not endanger the Z,iphius stock. Our estimate of apermissable quota, based on Omura's paper and the consistency of the average bodylength over the years is in the region of 30-50 animals, regardless of age or sex.
ACKNOWLEDGEMENT

We are greateful to the members of the Whaling Administration Section of theFisheries Agency for allowing their data to be used in this report.
We would also like to thank the stuff members of the Biology of Fisheries
Resources Division of the Ocean Research Institute, the University of Tokyo andMr. T. Kubota of the Fuji Suisan Co. for their helpful advice.
REFERENCES
HoucK, W.J., 1958. Cuvier's beaked whale from northern California. J. Mamm., 39(2): 308-309.
NrsmwAKr, M., 1965. Whales and Pinnipeds. Univ. of Tokyo Press, Tokyo, 439 pp. (in Japanese).
NrsmwAKI, M. and N. OGuRo, 1971. Baird's beaked whales caught on the coast ofJapan in recent 10 years.
Sci. Rep. Whales Res. Inst., 23: 111-122.
OMURA, H., K. FUJINO and S. KIMURA, 1955. Beaked Whale Berardius bairdi of Japan, with notes on Ziphiuscavirostris. Sci. Rep. W'ales Res. Inst., 10: 89-132.

Sci. Rep. Whales Res. Inst.,
No. 24, 1972.