Studies of the Relation between the Whaling Grounds
and the Hydrographical Conditions (I).
By
MICHITAKA UDA

Introduction

By the request of the Whaling Vessel-equipments Improving Committee and by the courtesy of the Whaling Companies in Japan (Taiyo,
Nippon Suisan, Kyokuyo, Nitto, Kinkai Hogei Fisheries Co.) together
with Whales Research Institute, the data of the whaling grounds inthe waters adjacent to Japan during 1910-1951, the daily whaling reportsof all catcher boats and the monthly whaling reports were given to theauthor at his disposal in order to study them. He plotted the maps ofyearly whaling grounds for each ten days and of the annual fisheries
grounds. 1) 2) 3)
In the opportunity the author wishes to state his sincere thanks
to the fishing companies above mentioned and the director of the
Whales Research Institute Dr. Tsutomu Maruyama and the director
Dr. Hideo Omura for their encouragement, and also to all captainsof the catcher boats who have prepared the correct data by theirzealously continued observations. Also he wishes to state his heartiful
thanks to the aids and cares given during his researches by the
Whaling Vessel-equipment Improving Committee (President Mr. Iwao
Fujita and its Charge in Press, Mr. Takao Ban and the Chief of Research
Section in the Fisheries Agency, Dr H. Omura.
Basing on the 10 days reports of whaling grounds, the charts prepared by us have shown clearly the location of fishing-grounds foreach species of whales, the date of catch, the abundance of catch, its
body length, stomach-contents, the data of whales seen, isotherms andcurrents with the general description of the sea conditions. The annual
report of whaling ground charts have shown the iso-lines of the catchof sperm-whales, sei-whales and fin-whales on the basis of the summarized
number for each rectangle of 1 degree of longitude and latitude and as
its consequence the location of the most concentrated abunaance ofwhales. Also the amount of catch for each sea-districts for each decadeand the body-length were shown in additional tables.
Hitherto, with respect to the whaling fishing grounds there appeared the researches carried out by Mr. Yoshio Matsuura•), H. Omura5)B)180

M. UDAK. Kasahara,7) K. Midunoe, 8) K. Otsuru, 9) the Japan Whaling Association10),
the Central Meteorological Observatory, 11) the Tokai Regional Fisheries
Research Laboratory 12) and Mr. Z. Nakai,' 3) however there lacks thedetailed study of the relation between the yearly whaling grounds andthe hydrographical conditions.
Basing on the above charts (for annual and each decade), the whaling
grounds in the waters adjacent to Japan; the Northern Kurile, the Middle
Kurile, the Southern Kurile, the Northern Coast of Hokkaido (off Akkeshi, Kushiro), the North-eastern Sea-region of Japan (off Sanriku, off
Kinkazan and off Fukushima and Ibaragi Prefectures), off Kishu (Kumano-nada), Ogasawara, Kyushu (SE-sea region, Got6-nada, Tsushima
Strait), South Western Islands (Amami Oshima and Ryukyu etc.), theSouth Sea to Formosa, the Yellow Sea, off the Southern Korea, theEastern Korea, the Japan Proper-side faced to the Japan Sea.
We can inspect the yearly variation of those whaling grounds easily,
and refering to the oceanographical charts we can at once point out
the following features:
1.

The General Trends of the Whaling Grounds.
(1) During 1910-1926 (Meiji, Taisho eras) the whaling grounds wereremarkably coastal one in general and among them the conspicuouswhaling grounds off Kinkazan, Sanriku and Kii were also limited in
the very coastal area by the capacities of the whaling navigation andthe whale processing at that time.
(2) The whaling grounds in the period after the year 1926
extended its circle to the offing of Kinkazan and especially developed inSouth Kurile region and the regions north and south off Hokkaido.
(3) Entering in Syowa era, during the years from 1932 to 1941
the whaling grounds have been extended to the North Kurile region
and marked with its prosperous fishing. Also in that period the Ogasawara Whaling grounds and the grounds adjacent to Korea developed
remarkably.
(4) After the last World War II, we have lost the whaling grounds
in the waters adjacent to Kurile and in the Yellow Sea, but we can now
continuing the fishing in the grounds mainly from the offing of Kinkazan to the offing of Akkeshi (Hokkaido), partly off the north coastof Abashiri (Hokkaido), Ogasawara and Kii (Shiono-misaki).
2.

Relation between the Variation of Whaling Grounds in Each Yearand the Corresponding Hydrographical Fluctuation.
(1) In the years of the prosperous cold current such as 1934 theStudies of the Relation between the Whaling Grounds

181

whaling grounds distribute relatively to the south with its center ofgrounds and extend conspicuously to the east offing. The catches in thecentral and southern districts of the North-eastern Sea-district of Japanare more abundant than that in the Hokkaido ground.
(2) In the cold years two centres of the whaling grounds, theoffing one and the coastal one, can be observed. Those correspond to
the two frontal regions of warm and cold currents at their heads ofthe coastal and offshore cold current respectively. The ratio of theareas of fishing grounds varies in correspondence to the relative fluctuation of the two cold currents above mentioned.
(3) In the year 1948 the state of the sea was normal, showing
remarkably rich catch on the whaling ground off Kinkazan. During theyears from 1944 to 1949 in accompany with the gradual decay of thecold current tending to warmer, the whaling ground extended its circle
to north than before and accordingly translated its centre of gravity tonorth in the fishing ground off Akkeshi (Hokkaido).
In short, in the former period of years during 1933-1941 (the prosperous period of warm current), the prosperity of the northern fishingground off Kurile Islands was shown. After then corresponding to the
decay of warm current and the development of cold current the whaling
ground temporarily tended to translate to south than before. Howeverafter the elapse of ten years in accompany with the rise of warm current
again the grounds have shown the tendeny to come back to the north.
(4) The fishing grounds of sei-whale show somewhat later appearance seasonally in the northern district than those of sperm-whale relatively in southern (warmer) region, more approaching to the coast compared to those of sperm-whale.
(5) We are now in the course of researches on the optimum temperature for each species of whales. However, roughly speaking, therange of the water temperature at the time of catch is prettily broad
and lies in the range 5°-28°C, centering at about 12°-23°0. Probably
the optimum temperature may be separated in two parts of 12°-16°C
and 17°-23°0 as those due to the optimum temperature of the feedersor due to the two fronts (Oyashio- and Kuroshio-Fronts).
The Oceanographic Structure Determining the Whaling Grounds are
as in the following.
(1) Each boundaries of water-masses (fronts) determine the favourable fishing grounds. Or in other words, they have intimate relations
to the distributions of the vertical and the horizontal gradients ofwater temperature. Particularly the massive centre of the whaling
3.

182

M. UDAgrounds locates in the zone where the cold and warm current collide
each other (i.e. where the cold current creeps beneath the warm current,
accordingly the vertical gradient of water temperature shows its maximum of the super-saturation of dissolved oxygen).
(2) The boundaries between the cold upwelling water-mass of acyclonic eddy and the warm water-mass, forming a cyclonic revolving
pattern of the tongues of cold and warm currents corresponds to thecentres of the most favourable whaling grounds. (Fig. 1, 2.) It may
120°E

1zs·

!.))"

135•

140•

150°

N

SIJ"

Olclwt:sk Sea~Whaling Ground

I}

40°

A~ PACIFIC

Ogasawara
I

Hahazima

125'1::

13<)0Fig. 1. Distribution of whaling grounds in relation to the boundaries
of water masses (fronts) and currents.

be due to the rich zone of the foods of whales involving, euphausid,
copepods, squids and sardine, anchovy etc. which were assembled toStudies of the Relation between the Whaling Grounds

11r

142"

f43•

144•

•

183

145°

Late July1150
o Sperm Whale
• Sei
0 Fin

Hokkaido

43•
18°

42°

42°

24°

41°

®

10·

141°

10·

142°

l

•

145°

Fig. 2. Typical examples of the distribution of the whaling grounds,
surface water temperature and currents.

184

M. UDAthe boundary of water masses by the convergence of currents.
(3) The migrating route of whales appears in the zone of abundant
food. It seems that the migration of whale schools and accordingly
the movement of their central whaling grounds are subjected by thenorth and south movement of the front of abundant food zone. One
migration route along the band of comparatively cold water on theJapan Trench stretching in the longitudinal direction to the east sideof the ridge of Fuji volcanic mountains, from Ogasawara fishing groundto the Southern NE-Sea district of Japan, was inferred by the recaptured
report (sei-whale) of the whale marking experiment, 14) and another routefrom the east off Ryiikyii and Amami Oshima, off Tosa, Kii Kumanonada to the south part of NE-Sea district of Japan were also inferred.
After jointing together the above two systems of whale schools going
to north migrate from the offing of Kinkazan to the offing of Akkeshi
and further to the Kurile sea-region.
(4) The mixing of the several species (sperm-whale, sei-whale, humpback-whale, blue-whale and in the north fin-whale) can be seen mostremarkably in the fishing ground off Kinkazan, and the next in the
ground off Akkeshi, also in the ground east off Ogasawara (Bonin Is.)
(5) Generally the whale school does not concentrate densely in theeasterly rapid flowing zone of warm current and not long there it passes
through the zone rapidly. Accordingly the whaling grounds are poorly
found in the westerly drift wind current area (a branch of Kuroshio)in the North Pacific Ocean and Kuroshio itself.
(6) The details of the whaling grounds in relation to the waterboundaries (fronts) are as follows.
(a) The Ogasawara fishing ground lying east to the Ogasawara
Hahazima where it corresponds to the region north of the line of Subtropical Convergence nearly crossing the Japan Trench, indicates a highly
productive zone and especially in the seasons of winter and spring (fromDec. Jan. to May having its centre in spring) it exhibits one of themost favourable whaling fisheries (sperm-, humpback and bluefin-whales
mixed zone). Here, the cyclonic rolling eddies locating in the cores ofwaters boundary formed by the north-going warm branch of the North
Equatorial Current and the cold water influenced by the upwelled southcoming Oyashio Under-current (intermediate water). The subtropical
Convergence indicates nearly the southern limit of the whaling groundand of albacore fisheries ground.
(b) The whaling grounds off Kinkazan correspond to the cores of
the water boundary between the Oyashio Cold Current and the northernStudies of the Relation between the Whaling Grounds

185

ranch of the Kuroshio Warm Current, forming the cyclonic rolling
ldies in the zone limited by the Oyashio Front (Polar Front) and the:uroshio Front (the northern marginal line of the Kuroshio main current).
he fishing season extends over the whole year, but its prosperous periodring in May-Nov. (spring, summer, autumn) of this well-known great
rhaling grounds of the longest season corresponds to the long stay ofrhales (sperm-, sei-, fin-, blue- and humpback-whales mingled).
(c) The whaling grounds off Akkeshi and Kushiro (in the southern~a off Hokkaido correspond to the cores of water-boundary forming
17clonic eddies in summer and autumn by the Oyashio Cold Current
owing to southwest along the south coast of Hokkaido and the north·oing warm branch of Kuroshio Current (NE warm branch current).
nits fishing season from May to Dec. (prosperous in summer and autumn)
he whale shoals (mainly sperm-, sei-, fin-whale and sometimes bluefinrhale mingling in them) are observed.
(d) The whaling grounds in the waters adjacent to Kurile Islands
ppears in summer in the frontal zone of cold watermasses of Oyashio
owing out from the Okhotsk Sea through the Straits of Kurile inrarmer watermass of the North Pacific Ocean.
In particular the Northern Kurile whaling ground is formed in therater boundary between the north-going warm branch current towards~amtchatska Penninsula and the North Kurile sea-region. It is noteds whaling ground (mainly of sperm-whale) in the season from June to:ite August. The middle Kurile whaling ground located in the area beween Shinshiru and Uruppu Islands, showing the whales (mainly spermrhale mixed with sei- and fin-whales) in the fishing season from middle
fay to middle Sept. The Southern Kurile whaling ground lies off the:torofu Is. and Shikotan Is. in the season from May to late Sept, showing
rninly sei-whale mixed with sperm- and fin-whales. The Southern Aleuian whaling grounds (sperm- and fin-whales) appears in the water
1oundary formed between the warm branch current flowing strongly
owards north during June and July and the cold current in the Northrestern part in the Bering Sea.
(e) The whaling grounds (mainly of fin-whale) north off Kitami
Abashiri) of Hokkaido are formed in the cyclonic eddies by the front·etween the south-coming East Saghaline Cold Current and the coastaloya Warm Current strengthened by the geomorphological conditions ofhe Okhotsk Yamato Bank and Cape Shiretoko. The fishing season begins
1 late June, prosperous in July (the maximum) and ends in early Sept.
(f) The whaling grounds in Kumano-nada are narrow and near the186

M. UDA

coast, forming cyclonic eddy located at the water boundary (front) between Kuroshio Main Current and the Coastal Cold Current in the fishingseason from January to July (in April, May, sperm-whale and in June,
July sei-whale dominantly).
(g) In some years the humpback-whaling ground was observed in
the waters to Okinawa coast during January-April.
(h) The humpback-whaling ground off Goarampii south of Formosa
was seen in the winter (Jan.-March).
(i) In the whaling grounds west to Kyushu, fin-whale (Jan.-April),sei-whale and sperm-whale (May-Nov.) and again fin-whale (June-Dec.)
were caught. The fishing grounds are divided in three parts (Goto Is.,
Yobuko-Iki Is. and adjacent to Koshiki-zima).
(j) The fin-whale ground in the Yellow Sea have the fishing seasons
during Jan.-April (May) and in Oct.-Dec.
(k) The Urusan whaling grounds of fin-whale were seen in thefishing season during August-November.
(1) The fin-whale whaling grounds off Genzan and Seishin along
the east coast of Korea were seen during March-April, Dec.-Nov.
(m) The fin-whale grounds in March and April in the waters adacent
to Sado and Noto were also observed in past years.

7 Remarks on the Antarctic Whaling Grounds.

There are greatest whaling grounds in the world located around thewater-boundaries circumscribing near the Antarctic Continent, whichcorrespond to the most abundant area of the food of whales (euphausia)
and they can be found by the oceanographic surveys or aerial surveys
by helicopter. The principles of the formation of whaling grounds may
be the same throughout the waters adjacent to Japan in the North
Pacific and in the Antarctic Ocean.

Concluding Remarks.

Now we can foretell the variation and location of whaling grounds
by investgating the oceanographic conditions and whaling conditions
continuously year by year as stated in above and by availing the mapsof whaling grounds, and also we can supply some important data to
the scientific control of the whaling.

Studies of the Relation between the Whaling Grounds.

187

Reference( 1) The Charts of the Whaling Grounds in the years during 1910-1951 in the Waters
adjacent to Japan with its Appendix Rep. (July, 1953) (The Whaling Vesselequipment Improving Committee).
( 2) The Oceanographic Charts of the Whaling Grounds for each Decade in the Year1951 in the Waters adjacent to Japan with its Appendix Rep. (June, 1953). (Ditto).
( 3) The Oceanographic Charts of the Whaling Grounds for each Decade in the Year
1950 in the Waters adjacent to Japan with its Appendix Rep. (Nov., 1953). (Ditto).
( 4) Yoshio Matsuura: Papers published in the Bull. of the Scientific Fisheries in Japan.
1935--41.
( 5) H. Omura: The Rep. of the Whales Res. Inst. No, 4.
( 6) H. Omura & Others: Sei-whales in the Adj. Waters of Japan. 1952.
( 7) K. Kasawara: Whaling and its Resource in the Adj. Waters of Japan. Rep. of
Nippon Suisan Co. Res. Inst. 1950.
(8) K. Midunoe: The Distr. of the Surface Water Temp, and the Whaling Grounds
during 1911-48. (1950).
( 9) K. Otsuru: Rep. of Nippon Suisan Co. (Type-written). (1950).
(10) Japan Whaling Assoc.: Antarctic Whaling Grounds. (1942).
(11) CMO: Oceanographic Charts (each Decade), and Obs. in the Antarctic Whaling
Grounds.
(12) Tokai Regional Fisheries Res .. Inst: Oceanographic Charts. (Monthly).
(13) Z. Nakai: Plankton Investigations in the Whaling Grounds. (Aug. 1953). (The
Whaling Vessel-equipment Improving Committee)(14) Japanese Fisheries Agency: Report on Whale Marking. 1950, 1951.
Postscript.
( 1 ) We can distinguish the following 4 types of the whaling grounds in the above
charts;the warm front type at the head of the north-going warm current (Apr.-Aug.),
the cold front type at the head of the south-going cold current (Sept.-Dec.),
the stationary front type (summer, winter) and the occluded front type (mostfavourable fishing grounds, however not persistent, feasible to change anddisappear).
( 2) The central localities of the main whaling grounds in the NE-sea district are atabout (40°-43°N., 144°-l47°E.) off Akkeshi, (37°--39°N., 142°-l44°E.) and (38°-48°
N., 144°-l46°E.) off Kinkazan.