Grey Whales in the East Sea Area of Korea
BY
KAZUHIRO :M:!ZUE

Introduction
Rhachianebtes goaucus is classified into a
Suborder Mystacoceti but it is quite a different
species from Balaenidae or Balaenopterynae.
Apart from them, it forms a family Rhachianectes by itself. Due to its resemblance tothe fossil whales of the Pleisiocetus group in
the shape of the skull it is often called a ·" living fossil " .
Whales of this species were captured soabundantly off the coast of California once
that they are still called Californian greywhales. But the catch there began to decrease rapidly towards the middle of the 19thcentury. It is reported, however, they are on
the increase in the recent years. Besides California, a considerable catch of grey whales

JAPANSEA

L---=o'-----"'-'---.._.~--~

Fig.

I.

was made in the East sea area of Korea, but their stock has completely been
exhausted at present. Roy C. Andrews made a detailed study of grey whales
at Urusan, the landstation in the East sea area of Korea during the season 1909,
2oo1910, which will be found in the Memoirs of the American Museum of
Natural History-V. We shall here makeISO
some study of the same subject statistically based on the data after 1910.

Number of the CatchFig. 2 shows a number curve of
the catches of grey whales in our adjacent waters according to the years.
It is based on the data from 1910 up
to the present.

In spite of the lack of

the data of some years, the curve gives
a clear idea of the rapid decrease ofFig.

2.

72

K. MlZUE

the catch. It is not before 1903 that Norwegian Whaling was adopted in the East
sea area of Korea for the first time, and in thirty years, almost the last grey
whale was hunted up there. The fact will indicate that the stock of grey whales
in our adjacent waters was but a small one existing, as it were, independently,
having no intercourse with the stocks of other waters.
At the middle of the 19th century when grey whales along the coast of Cali_fornia were feared to have gone to exhaustion, in the East sea area of Korea thestock was still kept intact, which began to decrease after 1903; during the fifteenyears from 1934 up to the present not a single grey whale was captured there.
Meanwhile, along the Californian coast, it is reported, grey whales are on theincrease. It apparently proves the fact that there is no intercourse between thetwo stocks of grey whales on the east and the west sides of the Pacific.
No catch of Grey Whales has been made off the eastern coast of Korea since1933. Of the thirty years' whaling history there, the records of the seven years,-1911, 1914, 1919, 1921, 1922, 1926, and 1932- are completely preserved in themonthly reports of the various whaling companies forwarded to the Japanese Whaling Society. Based on the data we shall here make some reports of the grey
whales in this place.
Table 1.
;%Sea-area.

jWhaling seasonI

1'1-------1-----_-_-_ -1-----1~~~~~~-~~l

1l,,

_ _

I_<.:_u_m_·1_e-_Is_l_an_as_ _ _ _ _ ______
0_.2____-_1 --A-,.,r-ugua_y_-s_t____1l

Hokkaido-Okhotsk

0.2

I

Hokkaido-Pacific0.2

Sanriku

O. 7

""'-'

I

July

I

October

1'I

Kinan

0.0

J'I

111

Bonin-Islands
0.0______________,_____
i__________
Goto-Ts1shima

4.2\December(1 - - - - - - - - - - - 1 - - - - - - - - - - - - - - - -1

l__w_es_t_of_K_o_re_a_____

I &""of Korea___
0_.4___ ___M___a_Y____
1
194.2

!,

Novembm--M;,-·

Japan-Sea
0.0
I1-----------1------'---------!
Formosa-Ryukyu
0.0I

Sea-Area is divided by location of the land-station
In Table 1 are shown percentages of the yearly catches in the seven years
according to the sea areas; the division of the sea areas is based on the sites ofGrey Whales in the East Sea Area of Korea

73

the landstations. The whaling ground of gray whales in the Goto-Tsushima sea
area actually belong to the east sea area of Korea. So 98% of the catch of grey
whales are made off the eastern coast of Korea. Grey whales in our adjacentwaters are different from other baleen whales in point of the distribution; they
have seldom been captured in the ground belonging to the Pacific. Besiees theEast sea area of Korea, three were caught at Ayukawa of the Sanriku sea area
and one off Nemuro, Hokkaido in 1914, two in the northern part of the Yellow
Sea in 1922, one off Sakhalin in 1826 and one off Otomae, the North Kurile Islandsin 1942. The number is so small compared with that of the catch made .in theEast sea area of Korea that they may be regarded as exceptional. However, theseeight grey whales were all caught in the waters north of 38°N.
---lllAfu____ fu-e,uNov.
,. A .....
-·~'·'DEC.

\\\JAN.

FEB.

l'IAR·In spite of the yearly decrease of
the number, body-length frequency
curves of the grey whales according
to the years follow the same pattern
every year rising into peaks in almost
the similar months. Fig. 3 showsbody-length frequency curves of thewhale catch according to the months ..
Here monthly variations in number are
noticable, and. in the case of malegrey whales, the peaks in the curves

apparently move from the left to theright according to the months, show~PR.
ing the process of their growth. (As""IS~l-------..L:.:::::::::::::::...:..--=..:::..:::::...__,,,..tlllY.!--jfor the females, due to the scantiness
~
•~
M~ -~
ff
~
N ~
' - - - - + a..; ~ x.. Jaolof the number, the phenomenon isFig. 3
hardly discernible) A-group in Fig. 3
is composed of one-year-old male animals, B-and C-groups of two-years-old andthree-years-old ones respectively. According to R. C. Andrews the ;period ofdelivery of grey whales lasts from the end of December to the beginning ofJanuary next year, and their body-length at birth is 14 feet, which gains no lessthan 18 feet during the first year after the birth. Seeing the growth speed ofgrey whales, like any other species, is extremely high in the first year, it isquite a8Sumable that the young whale born during the previous winter, is some
30 feet long when it appears in the Korean waters the next season. The bodylength of grey whales at birth, as it is calculated from my data is 15 to 16
feet.

IC MIZUE74Fig. 4 presents body length frequency curves of the whale catch according to the sexes. In the case of· male grey whales the curve rises intoa peak at 40 feet while in females apeak forms at 41 to 42 feet and again
at 44 feet. According to Figs. 3 andtoo,.
--~.
----f.......tu8•
7•
6•

4 female grey whales, like any other·species of baleen whales, are larger
in size than males.

Fig. 4Table 2IN~vemb~r~ecember
I January I
I_ _ _ _ _ _ _ _ .,__0 _1_-\!_. l~_0_,_-\!_l~_0_l_-\!_l~1·~umber of Whales
I 7 I 6 13 220 : . 125 345 97 j 22 / 119~A-v_er_a_g_e_1-en_g_th-·_i_n_f--e-et-- 39. 7i 42. 3 i 40. 9 39. 6 ' 42. 3 ! 40. 51 39. 8139. 0 I 39. 6Sex-ratio!I 'February IIMarchjJ

53.8 j 46.2 i

63.8 j 36.21

181.5 / 18.5 JApril

May/Total

1~l_-\!_l~,_0_1_-\!_l~l_0_ _-\!_~ _0_l_-\!_l~l_0_I_._-\!_I~
1 11 ', u
6 I 17 I 29837
8 I 8 I 13 I 37 .2 1 113 i545)'t1-45145._41.4 43.5 lrul~ 44.8 42.6: 39.8 i 44.8 IITT\ 39.9 '.~\4o.6 1
M[WO.O-. ~:35.31--i7sA!~--i-;;L-;-T~~f--l--u,3L7i-I
1
1

1

1

In Table 2 are shown average body lengths and sex ratios of the whole catch
according to the months. There is two feet's variation between the body lengthsof the two sexes, and the maximun body length of the males is 50 feet and thatof the females 49 feet, while the minimum body length is 29 feet for the males
and 35 feet for the females. In Table 3 you will find these particulars of thebody length of grey whales compared with the measuring values calculated byother writers in the past.

Grey Whales in the East Se,a Area of Korea

75

Table 3------I Average for all

ISpecimens of both sex-··--------

~--

23

38' 9t"I1 - - - - - - - - -123

39' IO"I

4

40' 8"!

545

40' 7''I

I

I

Korea, by Whalers

I

California, by Scammon iKorea.

i50···-1----

II

174

42' l"II

I Max. of female Max. of males I Min. of females
LlengthlengthlengthII
43' 3"
q8'. l"I 41' l"II

length38' 6"
39' O"

43' O"

45' O"

32' O"

I340' 8"372

I 39'11"

48' O"
50' O"

49' O"I

Min. of males
length32' 2"
35' 5"
32' O"
29' O"

Table 4MonthNovember

2.4

December

63.l

January

21. 8

II

---1i

41' 2"

I

Average for all males

20
I------73!

length! · · - - - - - -,--i41' 4"
3-----·-I'I

I

i No. of whale

lengthIII

I No. of whale I---

Korea, by Andrew .

No. of Whale

Average for all femalesIFebruary

0.8--------·-

March

3.1- --

April

6.8--

May

2.4-----

35' O"

K. MIZUE76

Table 4 presents the percentages of the monthly catches shown in Table 2.
According to it the catch of December forms the highest percentage· of 63.1 andthen comes the 21.8.% of January. The catches of the other months cannot becompared with those of the above two months. When we divide the catches ofboth December and November into decades, it will be found that there is a small
variation between the whaling seasons of the two sexes and that the best season
for both males and females is from the middle of December towards the end, andthe next best is either the beginning of January or that of December.
Table 5November::\IonthI No. of male'1Middle j 1ast I first
I
028
6I

i

Jmiddle J last

81Ill

I firstj middle

74

23--

No. of females

0Total

0i

629

49

47

147i 1257

130

158

88

30!
II Feb.

January

DecemberiI last I firstIIIIII1!

0'II''

02I

0I

Localities of the CatchAs has already been made clear by tables and figures, grey whales arequite regular in their appearance in the east sea area 'of Korea. According toTable 5, males begin to arrive there at the end of November, increase in number
till they reach the greatest number at the end of December, which declines towards
the middle of January. After that, male grey whales are no longer seen in thissea area. As for females, they begin to appear at the end of November, reachthe greatest number at the middle of December towards the end and decrease in
number till they leave the· place for the north at the middle of January. Thus
grey whales stay for only two months in this sea area; the place is also a goodwhaling ground for Fin Whales and many catcher-boats work during the season,from September to March next year. They ,would have certainly caught grey
whales if they had seen them in the months of October, November, February andMarch. The localities of the catch of grey whales, compared with those of fin
whales, are· qu!te near the coast. Their chief grounds are found within 10 seaknots from the shore.
Grey whales come to the east sea area of Korea for the purpose of delivery
as was already pointed out by R. C. Andrews. Female animals captured before
the middle of December, are, with almost no exception, with big foetuses immediately before birth. It is quite assumable that delivery is made among theislands at the southern extremity of the Korean Peninsula. Pregnant whales hasten
to the place of delivery by themselves, and a little later, herds of grey whales

77

Grey Whales in the East Sea Area of Korea

appear in this sea area. In the case of sperm ahales, many females led by onestrong male, from so-called "Harem". The contrary is true of grey whales; intheir case, the leader is a female and many males follow her. The fact will bemade clear by a survey of the sex ratio of the catch. Mr. Andrews writes in his
book, " One or two females lead ten to fifteen males." By this he must havemeant the pairing migration, for the waters at the southern extremity of theKorean Peninsula present a place of pairing for grey whale as well.
After delivery, female animals accompanied by cubs and apart from the herd,
go up north on their nursing migration.
According to Cap. H. G. Melson, the two female Grey Whales captured offChanzen (39° N.) at the middle of March, 1912 are found with foetuses of sevenand ten inches respectively,-both are two months and half after fecundation.

JANUARY-'•l•-3•

ir-10o11-is

G 26-So@so10... -,5~··-Fig.

5... ~!

78K. MIZUE

From this and other data the pairing season of grey whales is assumed to be at
the beginning of January. According to Mr. Scammon, the five female whales
with small foetuses captured along the coast of California (31°-37° N) in upseason, had thick blubber contrary to the animals nursing cubs. It is not supposable that female grey whales copulate while nursing. So their delivery may
happen, in the most favorable condition, every other year. 'Grey whales in down-season do not seem to hunt for food, for the animals
captured then have no food in their stomach but green colored gastic juice. Inup-season, after delivery or pairing, they begin to search for food. Grey whalescaught off Yushin, North Korea in up-season-from March to May, are sure to befound with Crustacea in their stomach. According to Mr. Tago, Nei:hrops thom-sonii, small sized Crustacea, was found in the stomach contents of the two grey
whales caught in the nothern waters of the Yellow-Sea in May, 1922.
Fig. 5 shows the localities of catch according to the months based on the dataof the seven years.. At the end of November a small number of grey whales appear both off Urusan and Chanzen. In December, catches are made in three places,
the best ground being off Urusan. The animals start on their northwards migration in January and the catch off Urusan decreases. It is interesting to notice thatno grey whale is caught in the month .of February, except one at Yushin in thenorth. The fact may indicate that grey whales go up north through the distantoffing during that month. In March
catches begin to be made in thenorthern part of this sea area. Either
in April or May the catch there forms
a comparatively large percentage of
the whole catch. These grey whales
captured in the northern part, are assumably stray or belated animals
from the main herd. Generally
spreaking, grey whales on theirsouthwards migration get up speed,
but slacken it when they go up north.
The general routes of the migra3S"

0Fig.

6

tion of grey whales off the eastern
coast of Korea, based on the various
data at our disposal, is shown in Figs.
6 and 7.
From the above two figures, weGrey ·whales in the East Sea Area of Korea

79

can assume the movement of grey
whales in the east sea area of Korea.
As for there where about after then,it is reported by Mr. Tago that theyreach Hokkaido or the western coastof Sakhalin in May or June and thenthrough the Mamiya Channal go to
the northern part of the sea _of
Okhotsk, where they seem to spend
their summer. On their southwards
migration they seem to take the same
course as they come up north. It is
not probable that grey whales passthrough the Soya Channal to thefarther north, for fin and hump-backwhales are captured there from theIandstation in Hokkaido but not greywhales. Nor is it assumable thatFig. 7
they go between the Kurile Islands to the North Pacific and further to the Bering
Sea, for the North Kurile Islands have many landstations from where both malesperm whales and fin whales were caught abundantly but no grey whale hasever been captured since 1919. (Tl)oµgh one was captured off Otomae, a landstation of the North Kurile Islands, ip August, 1942, it ought to be regarded asexceptional.)
According to Mr. Scammon (1874), grey whales in the American side of thePacific go down as far as 20° N. but in the Asian side· they go no farther than34° N. Nor will they go to the water whose temperature rises higher than 20°C.
The right temperature of water for both delivery and pairing of _grey whales isassumed to be 15°-20°C. In Fig. 5 the dotted lines show the distribution of
the annual mean temperature of the surface water in the East sea area of Korea.
October 30, 1949