DISTRIBUTION AND MIGRATION OF
THE WESTERN PACIFIC STOCKOF THE GRAY WHALE*HIDEO OMURA**
ABSTRACT

There are two geographically isolated stocks of gray whales in the
North Pacific. One is the eastern stock which migrates between the Beringand Chukchi Seas and Baja California, or California stock, and the other isthe western stock which has been thought to migrate between Okhotsk Sea
and south coast of Korean Peninsula. This stock was called Korean stock
because south coast of Korean Peninsula has long been thought to be its
calving ground.
In recent years papers from China reported that in the past graywhales also occurred in the Yellow Sea and East and South China Seas. In
the light of these information the Japanese catch and other materials werestudied and these supported these information.
In relation to the migration of these gray whales the difference of theocean structure between the eastern and western North Pacific was noted.
In the latter the continental shelf is well developed. The gray whale isthought to have lived in shallow water and migrated directly across the East
China Sea between Kyushu and South China, from east to west or reverse
way, while some whales have migrated along the coast of the Yellow Sea.
INTRODUCTION

The gray whale, Eschrichtius robustus (Lilljeborg, 1861), is the sole member ofthe family Eschrichtiidae and is considered to be the most primitive surviving
baleen whale. There are presently two geographically isolated stocks: aneastern Pacific stock, which migrates between Baja California and the Beringand Chukchi Seas, and a western Pacific stock, which migrates between South
Korea and the Okhotsk Sea. These may be designated the California stockand the Korean stock, respectively, on the basis of their breeding grounds(Rice and Wolman, 1971).
The California stock was once reduced heavily by whaling in the 1850s as
well as by the operation of floating factories after the turn of the century.
Even so this stock made remarkable recoveries. Since it was afforded protec• This paper was read at a symposium of the XVI Pacific Science Congress held in Seoul, 20-30 August I987.
•• Whales Research Institute, 3-32-11, Ohjima, Koto-ku, Tokyo 136, Japan. Retired in October, 1987.
Sci. Rep. Whales Res. Inst.,
No. 39, 1988, 1-9

OMURA2

TOTAL CATCH
1,362 WHALES

150

z

w
i.:

et

....
VJ

w

...J

et

:r
~

100 .....

LL.

0

cc
w

....

al

:?!
:::i

....

z

50 -·

0

nnnnnn.nn_

I

I

I

1910

1915

1920

1925

1930

I

1935

YEAR

Fig. 1. Catches of gray whales in the western North Pacific region.

tion from commercial whaling in 1946 by the International Convention for
the Regulation of Whaling, the population has recovered steadily. The stock
has been classified as a Sustained Management Stock since 1978, based on theunderstanding that it had remained stable at about 11,000 whales over an 11
years period with approximately constant catches (IWC, 1986).
The western Pacific stock of the gray whale was hunted twice in the history of whaling. Prior to the turn of the century whales were taken in Japan
using hand harpoon and net (net whaling). This whaling was conducted in
two regions of Japan, one the Pacific side and the other on the coasts ofsouthern Sea of Japan and eastern East China Sea (off Kyushu andYamaguchi prefecture). Right whale (Eubalaena glacialis), humpback whale(Bal,aenoptera novaeangliae) and fin whale (B. physalus) were the major targetsof this whaling, but the gray whale and other species of whales were also
taken (Omura, 1984).
Gray whales in the above two regions may represent different populations. The gray whales coming to the Pacific side is thought to have followed amigration route along the east coast of Japan (Nishiwaki and Kasuya, 1970;
Sci. Rep. Whales Res. Inst.,
No. 39, 1988

GRAY WHALE MIGRATION

3

Omura, 1974, 1984; Bowen, 1974). Bowen (1974) describes further that thosegray whales should be regarded as strays from the Bering Sea. Migration ofthese whales, however, is not discussed in detail in the present paper. The
gray whales coming to the coasts of Kyushu and Yamaguchi prefecture are
portion of those whales migrating in the waters adjacent to Korea (Omura,1984).
After the turn of the century (in the years 1911 - 1933) gray whales were
hunted heavily by modern catchers on the coast of Korea, and once the stock
was thought to be exterminated (Mizue, 1951; Bowen, 1974), but this was not
the case and some still survive (Brownell and Chun, 1977; Yablokov andBogoslovskaya, 1984) (Fig. 1).
The calving ground of the western Pacific stock was once believed to be
the southern coast of South Korea (Andrews, 1914; Mizue, 1951; Rice and
Wolman, 1971; Omura, 1984; Yablokov and Bogoslovskaya, 1984). Wang
(1984), however, noted the occurrence of gray whales in the Yellow Sea, theEast and South China Seas and described that the calving grounds of thesewhales are possibly in Baya Bay and Wailuo Harbour. In the light of thesereports I have tried to make clear their migration route using data in hand.
MIGRATION OF GRAY WHALES ALONG THE KOREAN PENINSULA
Andrews (1914) who firstly investigated gray whales at Ulsan, Korea, during aperiod in January and February 1912 states as follows:"In November and December, when the females are taken, almost every
individual will be found to be carrying young nearly for birth. As these would
necessarily be delivered within two or three weeks after passing Ulsan, thebirth must occur in the bays among the numerous small islands at the extreme
southern end of the peninsula."
In fact he examined 24 gray whales during his stay at Ulsan, in which 21
whales were males and 3 were females. One of the females contained a fetus
476cm long. The mean body length at birth of the gray whale fetus is 4.9
meters for the California stock whales (Rice and Wolman, 1971). This fetus,
therefore, can be regarded as near term. This is, however, the only fetal record
he had. It is clear, therefore, that the statement was based largely on information supplied from others, especially a Norwegian whaling gunner H. G.
Melsom, who worked with him.
As already stated a portion of the Korean stock had migrated to thenorth coast of Kyushu, where they were taken by net whaling prior to thiscentury. No catch statistics by species in Kyushu are available (Omura, 1984),
but it is clear that gray whales (Ko-kujira) were also taken at Ikitsuki Island in
addition to right, humpback and fin whales (Yamada, 1983)*. There the* An English translation from a Japanese old book entitled 'Isanatori-ekotoba', which means "Whaling,
explained with pictures". In the translation this was erroneously written as 'Yogiotoru eshi'.

Sci. Rep. Whales Res. Inst.,
No. 39, 1988

4

OMURA
TABLE !. CATCHES OF GRAY WHALES BY JAPANESEWHALE CATCHER (AFTER KASAHARA, 1950)
Area
Year

XII

XIII

XI

13

106

2

XIV

Total

1910
I

2
3
4

30

109

15

5
6
7
8
9

130
36
53
91
35

9

41
13
10
11

52 3)
23
19
4

2
2

1920
I

2
3
4
5
6
7
8
9

J43)
53
19
23
13
I

3

1930
I

2
3
Total

244

2
2

2

F. and W. 1)

6
121

121
1922)
131 2)
154

193
131
155

139
77
68
103
46

139
78 3)
69
104
46

68 3)
78
40
27
13

68
78
40
27
17

10
9
6
9
11

10

10

10
9
9
12

II

30
10
7

30
10
7

30
11
7
2

1,362

1,374

750

38

7

10
9
12

(I) Cited from Rice and Wolman (1971) which includes catches of gray whales in other areas, e.g. Okhotsk Sea.
(2) Cited from other sources kept at the Japan Whaling Association.
(3) Corrected in this table.
For the areas see text and Fig. 2.

whale migrating from north to south was called as the Down-going whale andthat coming from south to north as the Up-going whale. This is applied toabove four species of whales, including the gray whale. Hence the island wason the route of the southward and northward migration of the gray whale,
while it is situated more southerly than the south coast of Korea.
Kasahara (1950) analyzed the catch statistics of Japanese coastal whaling
between 1911 and 1949. A total of 83 land stations were operated by Japaneseindustry during the period in the western Pacific. He grouped these land
stations into 16 areas and made clear the yearly catches of each species in eacharea in his Table 10.
Sci. Rep. Whales Res. Inst.,
No. 39, 1988

GRAY WHALE MIGRATION

5

130

Fig. 2. Positions of land stations concerned with catches of gray whales(after Kasahara, 1950).

Table 1 was rearranged from his Table 10, extracting areas where graywhales were mostly taken during this period.
As to the Kasahara's area some explanation may be needed here (Fig. 2).
Area XII means northeast Korea and includes land stations at Chongjin,
Shinpo and Changjun. Area XIII means southeast Korea and includes Uljin,
Kuryongpo and Ulsan. Area XI means North Kyushu and includes Senzaki,
Okochi, Izumi, Nishidomari, Hidakatsu, Iki, Katashima, Yobuko, Ukishima
and Arikawa. Area XIV means Yellow Sea and includes Cheju Island, Taihuksan, Uchong Island, Taechong Island and Changshan Island (Kantoshu).
As seen in Table 1 gray whales were mostly taken in Area XIII or southeast coast of Korean Peninsula and Ulsan was the center. This was followedby the Area XII or northeast coast of Korean Peninsula, and then North
Kyushu. It is noted, however, some gray whales were taken in the Yellow Sea.
Sci. Rep. Whales Res. Inst.,
No. 39, 1988

6

OMURA

This supports the recent reports of Wang ( 1978, 1984) that gray whales occur
in the Yellow Sea.
In this connection I recall a whale observed by Professor K. Uchida of
the Kyushu University. He was a famous ichthyologist who studied fish larvae.
Prior to 1945 he worked at the Fisheries Research Laboratory at Pusan, Korea
and made an expedition to collect fish larvae in May 1930 in the Yellow Sea.
He positively identified a gray whale during this expedition near Inchon, an
island locally called "Chanchangon" and situated at northwest of 60 nautical
miles from Inchon. His observation of the whale is well described in his book(1964). He observed clearly the fluke-lifting behaviour of a gray whale. He
also writes that the area was said to be a gathering place of whales.
Andrews (1914) writes that Captain H.G. Melsom has often observed
them (gray whales) in this vicinity, but because of the abundance of other andmore valuable species, they are not killed at this time by the Japanese. Thiswas written about the whaling off the south coast of Korean Peninsula, but itis thought this was applicable also to the Yellow Sea, because the main catches
in this area were fin whales.
It is possible, therefore, that the so-called Korean stock of gray whales, orat least a portion of them, entered into the Yellow Sea and hence migrated
south along the east coast of China, as shown in Fig. 2 of Wang (1984). It isalso possible that some whale went westwards from south coast of Korean
Peninsula to the east coast of China, across the southern border of the Yellow
Sea.
MIGRATION ROUTE OF GRAY WHALES THROUGHTHE COAST OF NORTHERN KYUSHU
Gray whales migrating to the northern Kyushu is a part of the Korean stock
and its migration past Ikitsuki Island was noted above. However, the migration of these individuals are very difficult to be understood. Fig. 7 of Omura( 1984) shows only the distribution of gray whales then known to him. In thecase of humpback, fin and right whales it is possible that they migrated
further south through the west coast of Kyushu. At Kasasa, a fishing village
on the west of Kagoshima prefecture, these three species of whales weresometimes taken accidentally entangled in fishing nets (Nasu, 1974; Anon.,1978).
Gray whales, on the other hand, have never been noticed by villagers of
Kasasa. It is possible, therefore, that gray whales took different course of
migration from the above three species.
In this connection this problem should be considered in relation to thedepth of the ocean. It is well known that the gray whale relies upon thebenthic animals for food, though peripheral areas and pelagic resources arealso exploited (N erini, 1984). This does not mean, however, that they also livein pelagic seas. The California stock of gray whales migrates along the coastal
Sci. Rep. Whales Res. Inst.,
No. 39, 1988

GRAY WHALE MIGRATION

120E

130E

7

140E

Fig. 3. Migration of the western Pacific stock of gray whales. (Excludes those occurringon the Pacific side of Japan).
1. Ikitsuki Island
2. Goto Island
3. Kasasa, Kagoshima prefecture

waters, and even in the eastern Bering Sea they travel within 2km from shore
to Nuvivak Island after passing through Unimak Pass in the northboundmigration. They migrated offshore only from that island to waters aroundSt. Lawrence Island (Braham, 1984).
In comparing the migration of the eastern and western stocks of the graywhale we should consider the difference of the ocean structure between theeastern and western North Pacific. In the eastern North Pacific the continental shelf is less developed and the deep sea is close to the continent. On thecontrary in the western North Pacific the continental shelf is well developed,
and the Yellow Sea and most parts of the East China Sea are shallower than
200 meters.
The gray whale is thought to have evaluated to live in shallow water. In
Fig. 3 the continental shelf or 200 meter depth line is shown by dotted line.
As seen in this figure most part of the East China Sea is shallower than 200
meters, and the 200 meters line extends from east side of Formosa to thesouth side of Kyushu, but a tongue of deep water projects along southwest
Kyushu as far north as it reaches westside of the Goto Islands, a group ofsmall islands situated southwest of Ikitsuki Island. The gray whale, therefore,
is thought to travel westwards, instead of southwards, avoiding this deep
water, from Ikitsuki until it reaches to the coast of China. Such migrations
directly crossing the East China Sea, from east to west or reverse way can not
Sci. Rep. Whales Res. Inst.,
No. 39, 1988

8

OMURA

be denied. In this case they travel about 400 nautical miles of offshore.
Wang ( 1984) speculated that the western Pacific stock of the gray whale
migrated in the former times through the waters off the east coast of China,
and entered the calving grounds in the coastal waters of Guangdong Province. He also extended the speculation that these calving grounds are possibly in Baya Bay and Wailuo Harbour and that a few individuals probably
reached occasionally as far south as 20°N in the adjacent waters of the east
coast of Hainan Island.
In the light of the above knowledge of the distribution of the two graywhale stocks the names of "California" and "Korean" stocks seem to be inappropriate. The better expression will be "eastern Pacific" and "western
Pacific" stocks of the gray whale.
Present size of the western Pacific stock of the gray whale, however, hasbeen reduced to such a low level that it can no longer function as a significant
part of its ecosystem (Brownell, 1977). Yablokov and Bogoslovskaya (1984)
referred to a statement of Berzin ( 1978) that they were not recovering andthe number continuing to decline.
ACKNOWLEDGEMENTS

I am much indebted to Dr R. L. Brownell, Jr. of the U.S. Fish and Wildlife
Service, San Simeon, California for his critical comments and correction of
languages of earlier draft of this manuscript. Dr Toshio Kasuya of the Far
Seas Fisheries Research Laboratory and Dr Akito Kawamura of the Faculty ofFisheries, Hokkaido University kindly reviewed the manuscript and offered
many useful comments.
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Sci. Rep. Whales Res. Inst.,
No. 39, 1988