FISHERY OCEANOGRAPHIC STUDY ON
THE BALEEN WHALING GROUNDSKEIJI NASU
INTRODUCTION

A Fishery oceanographic study of the whaling grounds seeks to find the factors controlling the abundance of whales in the waters and in general has been a subject ofinterest to whalers. In the previous paper (Nasu 1963), the author discussed theoceanography and baleen whaling grounds in the subarctic Pacific Ocean. In thispaper, the oceanographic environment of the baleen whaling grounds in the coastal
region ofJapan, subarctic Pacific Ocean, and Antarctic Ocean are discussed. J apanese oceanographic observations in the whaling grounds mainly have been carriedon by the whaling factory ships and whale making research boats using bathythermographs and reversing thermomenters. Most observations were made at surface.
From the results of the biological studies on the whaling grounds by Marr ( 1956,
1962) and Nemoto (1959) the author presumed that the feeding depth is less thanabout 50 m. Therefore, this study was made mainly on the oceanographic environment of the surface layer of the whaling grounds.
In the coastal region of Japan Uda (1953, 1954) plotted the maps of annual
whaling grounds for each 10 days and analyzed the relation between the whaling
grounds and the hydrographic condition based on data of the daily whaling reports
during 1910-1951. A study of the subarctic Pacific Ocean whaling grounds inrelation to meteorological and oceanographic conditions was made by U da andNasu (1956) and Nasu (1957, 1960, 1963). Nemoto (1957, 1959) also had reported
in detail on the subject from the point of the food of baleen whales and the ecologyof plankton.
Numerous physical, chemical and biological studies of the Antarctic have been
described by the Discovery Committee. Studies of the physical and chemical
oceanographic environment of the whaling ground based on the data obtained by
the Japanese surveys were made by Shimomura (1947), Sugiura (1949), Tsuchida(1952), Nasu (1959), Kumagori (1963), Ishino (1963), Uda (1963) and Ishino &Nasu (1965). The biological study was made by Nemoto & Nasu (1958) and
Nemoto (1959).
The present paper gives the oceanographic structure of these whaling grounds
and the physical environment connected with the distribution of baleen whales,
using data obtained by whaling research, operation ships and other survey ships.

157

158

K. NASU

DISTRIBUTION OF BALEEN WHALING GROUODSOF THE WORLD IN THE PAST 10 YEARSCOASTAL WHALING GROUNDS

Coast of JapanThe sea regions from Sanriku * to Hokkaido are the most representative whaling
grounds in the North Pacific, and the whale species caught consist mainly of sei
and Bryde's whale. The sei whale is the most important species and its catchaverage about 600 in a year. Generally the favourable seasons are from May toJune off Sanriku and from September to October off Hokkaido.
The catch of Bryde's whale in the Sanriku region is primarily influenced especially by the fluctuation of the Kuroshio water mass because the distribution of
Bryde's whales depends on water with about 20°C or more in surface temperature
Omura & Nemoto 1955, Omura 1959). The total catch of whales caught in themost abundant years in the Sanriku was 400 and the average number in a year was
about 120. On the other hand, the catch off Hokkaido was less than 10 in a year,
because of colder sea region than Sanriku. Sometimes the fin, blue and humpback
whales were caught in this sea region, too. The catch of fin whale in the Okhotsk
sea was reduced recently and a catch of few sei and humpback whales was observed.
The favourable seasons being from July through August.
Whaling in the East China sea commenced in 1955. The fin whales are mostimportant baleen whale species there. About 250-300 animals are caught in abundant catch years, Bryde's whales also were caught here.
The main whaling grounds of Bryde's whale were located off Kii Peninsula,and the total number of whales caught reached more than 200 in plentiful years.
In waters adjacent to Okinawa Island in the Ryukyu Islands humpback whales
mainly were caught. More than 200 animals were taken during January to Marchin rich years (the catch in 1958 reached 240 animals). The catch ofBryde's whales
also was observed on the coast of Formosa, but the number of whales caught was very
few compared with Ryukyu Islands. The whaling operation in these waters haveclosed from 1963 in Ryukyu Islands and 1960 in the coast of Formosa, respectively.
Coast of North America
The most important whaling grounds in this area was located off British
Columbia and the catch during April to October in 1963 were 30 blue, 220 fin, 24
humpback and 154 sei whales, the favourable whaling season for each whale
species is as follows: blue whale: May-July; fin whale: May-August; himpback
whale: May-June; sei whale: June-August. The coast of California is also an
important baleen whaling ground, that is, the catch in 1963 are 6 blue, 16 fin, 55* Sanriku includes the waters to the northeast of Honshu, Japan.

OCEANOGRAPHY OF BALEEN WHALING GROUNDS

159

humpback and 97 sei whales and the favourable whaling seasons are April-May forhumpback whale and July- August for sei whale, respectively.
Coast of South America

The whaling off the Chilean coast was operated for long seasons except Augustand September. The chief whale species was sperm whale (the total number ofwhole caught in 1963 was 1494). However, Clark (1962) reported that unexploitedbaleen whaling grounds were located in the waters of 30°-35°S latitude in thevicinity of Rumbolt current. After that, 378 blue, 138 fin and 190 sei whales werecaught by the operation from November of 1964 to March of 1965, and so it may beconsidered that the results of the survey by Clark were justified. The favourable
whaling seasons are for fin : November, December and for sei and blue : after January,respectively.
In addition, according to the composition of body length and shape of baleen
plate, the blue whales in this area seem likely to pigmy blue whales which were observed in the sea regions from Kerguelen to Marion Island (private informationfrom Dr. Ichihara). The baleen whale catch in the waters of Brazil consists mainlyof sei whale. The sei whale catch, recently has decreased motably.
Coast of Australia and New ,ZealandIn the coast of New Zealand and Australia mainly humpback whales were caught
and whaling seasons are May-July in New Zealand and June-October in Australia.
The number of whales caught in good years amounted to about 300 in New Zealand,
and about 2,000 in Australia. The catch, however, in 1963 decreased to 9 animals
in New Zealand and 87 in Australia. On the other hand, the catch of sperm whalesin these waters has increased considerably recently.
Coast of South Africa

In south African waters whaling was carried on from the coast of Natal andthe coast of Cape Province. The baleen whale species in these waters consists
mainly of fin and sei whales. On the coast of Cape Province, 50 or less, Bryde's
whales are also taken in a year. The favourable whaling seasons are May to Octoberin both waters. In 1959. 160 humpback and 6 sei whales were caught in Gabon
on the west coast of South Africa.
North Atlantic and Arctic

The representative whaling grounds in this region were Iceland and the Norwegian coast. The main species of whale was fin whale in both regions. The averagecatch of fin whale in a year from Iceland was more than 250. The sei whales also
were caught, averaging 70 animals in a year, but the catch of sei whale has decreased notably recently (the catch in 1963 decreased to 20 animals). The whaling
grounds off Norwegian coast are located near Steinshamn in the southern districtof Norway and near Skjelnan in the northern district of Norway. The main whale
species (fin whale) caught and the favourable whaling seasons (June to Aug.) are160

K. NASUquite same in both grounds. The total annual catch average in these regions reachedabout 160 animals.
The catch in F~roe Islands consists mainly of fin whales and reached 141
animals in 1957, but the annual average (less than 80 animals) was less than
Norway and Iceland. The catch in these waters was also strongly reduced in recent
years, and was only 3 fin whales in 1963.
In the west coast of Greenland the annual number of whales caught was morethan 200 animals up to 1957, but the catch in recent years can not observed. The
catch in Newfoundland also can not observed from 1960.
Some baleen whales also were caught in Spain and Madeira, where the highnumber of sperm whales were caught.
PELAGIC WHALING GROUNDS

Subarctic Pacific
The Japanese operations with floating factories in the subarctic Pacific Ocean
were resumed in 1952, and the whaling grounds covered the Bering Sea the northernpart of North Pacific and the Gulf of Alaska. The baleen whale catch in thesewaters consists mainly of fin whales, but the catch of sei whales have increased
notably in recent years.
The fin whaling grounds were located from the southern region of the AleutianIslands to the Bering Sea, but no blue or sei whaling grounds were located in the
Bering Sea.
Antarctic
The locality of baleen whaling grounds operated by the Japanese floating
factories varied in the recent 10 years. That is, the grounds during the seasons in
1954/55-1956/57 covered the waters of 170°W to 80°W, and the western end ofwhaling grounds reached to 50°E in 1960/61, 10°W in 1962/63 and 60°W in 1964/65.
The latitudinal positions of grounds also varied abruptly, that is, the whaling
operations have been carried on near the Antarctic Convergence, and the northernborder reached in 47°S latitude. Pigmy blue whales were caught in the adjacentwaters to Marion, Crozet and Kerguelen Island in 1959/60. In 1964/65 the baleen
whaling grounds operated by Japanese floating factors completely shifted to the
Antarctic Atlantic sector, and the northern border reached in about 45°S whichcorresponded to the vicinity of Sub-tropical Convergence which was characterized
by the comparative high temperature with 13°-l4°C as surface temperature.

OCEAROGRAPHIC STRUCTURE OF BALEEN WHALING GROUND
IN THE WATER TO THE NCRTHEAST OF JAPAN AND OFF HOKKAIDO.

The oceanographic analysis of baleen whaling ground in this area were made on
the sei whale whose catch was the most abundance. The whaling grounds weredivided as Fig. 1 by the land station. In addition, the catch statistics used in this

OCEANOGRAPHY OF BALEEN WHALING GROUNDS

161

paper were those 1955-1963. Fig. 1 shows the locality of land station from 1955
to 1963.
Moreover, the data used in this chapter are as follow.
1953 1954: Nihon Hogei Senpaku Sobikaizen Iinkai
Meteorological Agency,
Whale chaser
1962

40°N

ONAGAWAA YU KAWA

35•
145°E

Fig. I.

Locality of land station.

Oceanographic conditions ef sei whaling groundThe coasta lwhaling ofJ a pan is operating from May to October, and the favourable whaling ground is generally moving from the northeast of Japan to Hokkaido.
Figs. 2-1, 2, 3 show the relation between the distribution of surface temperaturesand sei whaling grounds in 1953, 1954 and 1962 respectively.
May: 1953-The favourable whaling grounds are located in the waters with
l3°-l6°C surface temperature which lie in mixing area*> and the edge of the
branch of Oyashio.
1954-0ceanography in relation to whaling ground was not clear, because of few
data of catch distribution, but the oceanographic condition was characterized by*The waters to the northwest of Japan was divided into Kuroshio, Oyashio and Transition areas, andthose surface temperature are as follows (Kawai 1959).
Area
Oyashio
KuroshioTransition
Season14°-19°C
5°-l6°C
0°- 7°C
Feb.-Mar.
10°-19°C
17°-23°C
2°-12°CMay
20°-27°C
25°-29°C
10°-22°c
Aug.
13°-22°C4°-l5°C
20°-25°C
Nov.

162

K. NASUthe cyclonic eddy between Oyashio (0) and Kuroshio (K).
1962-The whaling ground was located in the waters with temperatures of l3°-15°C
at the surface which correspond to the colder part in the mixing area.
June: 1953-The maximum catch of sei whales which generally is in June
was in May in this year. The whaling ground was located in the mixing area,and es- pecially was formed around the oceanic front consists of the northwardly
flowing warm waters and southwardly flowing cold waters. In addition to the warm
water mass in 1953 was located more easterly than in normal years.
1954-The kuroshio water mass in 1954 was located in a more western area than1953. The surface temperature generally was higher than in 1953 and the main
whaling ground was formed in the waters of l 8°-20°C (especially the most favourable
whaling area is at the west side of warm water mass towards north).
July: 1953-The main whaling ground was located in the domain of 21°230C near the frontal zone of northwardly flowing warm water mass which corresponds with the oceanic front by the warm and cold water mass.
1954--The distribution of sei whales extends to the northeast direction, and the
locality of main whaling grounds are found near the frontal zone of Oyashio which
is characterized by 12°-l4°C at surface temperature, too. Therefore, it seems thatthe whaling ground moves to the northeast of Japan to the Hokkaido area in thisseason.
1962-The whaling ground was located in the mixing area, and the most favourable
area was found in oceanic front between the Kuroshio and Oyashio water mass
near in 146°-144°E lat. which is characterized by 22°-25°C at surface temperature.
August: 1953-The distribution of temperature appears roughly similar toJuly, but it was supposed by the catch of whale that the amount of migrating whales
was increased. The main whaling grounds were found in the mixing area between
the warm and cold water mass and were divided into cold area where is near thefront of Oyashio l9°-22°C (at surface temperature) and warm area where is near
the front of Kuroshio (23°-26°C at surface temperature).
1954-From the locality of favourable whaling grounds which are situated in thewaters with temperatures of l 7°-20°C at surface. Evidently the main group ofwhales had moved toward the cold area to the north of Oyashio front. Morever
the favourable whaling ground in the north of 42°N was located to the west ofsouthwardly the 2nd Branch of Oyashio, and it was supposed that the whaling groundnear 40°30'N, 148°E corresponded to the southern border of the 2nd Branch of the
Oyashio (See Fig. 2-2).
1962-The favourable whaling grounds were in the Oyashio area (l 7°C-20°C at
surface temperature) and bordered the Kuroshio front (23°-27°C at surface temperature), and such phenomena seemed to be a moving seasonal whaling ground.
September: 1953-The whaling grounds are similarly located in the two areas
as in August and generally existed to the north. That is, the whaling ground layin the water of l0°-l8°C near 43°N in the Oyashio area and near 39°N in the warm
waters, where owing to the condition of the surface temperature field, must be formedof the cyclonic eddy between the southwardly 2nd Branch of the Oyashio and the

OCEANOGRAPHY OF BALEEN WHALING GROUNDS
l 45'E

JUNE

40°N

40'N

145'

145 'E

145°E

40°N

40°N

l 45°E

Fig. 2.

Distribution of surface temperature and sei whaling ground in 1954.

163

164

K. NASU

warm waters.
1954-The southern whaling ground in 38°-39°N lie in the waters of 21°-26°C
at surface temperature, which may be considered that the cyclonic eddy was formed
between the southwardly cold and northwardly warm waters.
1962-The whaling ground in September was found far north of the previous
month's, an especially favourable area located in front of tongue shaped warm
waters near 42°N, 148°E. According to this phenomenon it must be presumed thatthe northward moving structure of whaling grounds participate in the situation of
tongue shaped warm water mass.
October: 1953-The favourable whaling ground was located in the west areaof the 2nd Branch of Oyashio near 42°N, 14 7°E, and in the oceanic front between
the cold and warm waters near 40°N, 144°E, too.
1954-The whaling ground was in the Oyashio area to the north of about 43°N,
which is characterized by 10°-l2°C at surface temperature (Fig. 2-3).

Consideration of the sei whaling grounds
According to the reports of whale chasers, the sei whales off Sanriku coast inlast of April were sighted in waters of 8.5°C-13.11°C surface temperature. The
area having the highest whale density existed in water of 12.2°-l3.0°C where corresponds to the southern area in the Polar Frontal Zone.*In May through June, as shown by Fig. 9, the number of sei whale in the Sanriku area abruptly increases. As already stated the whaling grounds locate in theadjacent waters to southerly Oyashio waters within the mixing area which consistsof Oyashio and"Kuroshio waters, and the main grounds were formed in the northerly
warm waters area (Kuroshio waters). The most favourable whaling grounds exists
in the extreme area of warm waters. In July, the northward flow of Kuroshio
water mass predominates (In 1982, in spite of the notable predominant Kuroshio,
the whaling grounds were located considerally southwards) and the whaling grounds
move from Sanriku area to Hokkaido area with the northerly movement of theKuroshio.
In August of 1953 and 1962, the whaling grounds were formed considerablly
southwards, and the general character of oceanographic conditions are that thenorthwardly flowing warm water mass (Kuroshio system waters) became located in
the waters adjacent to the Sanriku coast in these respective years. In 1954 the main
whaling ground moved off Hokkaido, and the northwardly flowing warm watermass became located further from Sanriku coast than in 1953 or 1962. In addition,
the surface temperature of whaling grounds in August reaches 26°C by influence ofKuroshio waters.
In September some of the main whaling grounds are located in the Sanriku
sea region as 1954, but these are generally located off the Hokkaido sea region.
By above mentioned phenomena the whaling grounds off Sanriku and Hokkaido are formed in the southern part in the transition area at beginning of whaling
season, and moving towards the north with the increase of Kuroshio waters. It* The Polar Frontal Zone is a general term for the Kuroshio and Oyashio front.

OCEANOGRAPHY OF BALEEN WHALING GROUNDS

165

1.500

w
<(

I

s
~ 1,000

0

8
z
,_

I
('.)

::>

0 500

Fig. 3.

Monthly catch of sei whale at Sanriku and Hokkaido in the years 1955 to 1964.

YEAR

OFF SANRIKUCAUGHT NOS.
OF WHALE

OFF HOKKAIDO

100
317

Y"'

l 955

64 50

/J

~

1-----======-~====~~===::::::=====--o>--~~~-1

1956

~
247

1957

l 958

l 959

1960

1961

1962

1963

1964

Fig. 4.

Monthly and yearly catch of sei whale.

507

166

K. NASUmay be considered that the moving mechanism of the whaling grounds were
influenced by the conspicuous tongue shaped Kuroshio waters which project towards the north.
Fig. 3 shows the monthly catch of sei whale of Sanriku and Hokkaido in theyears 1955 to 1964. Judging from the monthly fluctuation we can find that theprosperous whaling times generally are in June off Sanriku and in September off
Hokkaido, and it seems that the whaling grounds move from Sanriku area to Hokkaido area in July to August.
Fig. 4 shows the monthly and yearly catch of sei whale was drawn to study
the moving mechanism of whaling grounds.
From Fig. 4 we can to two ground whaling condition types, the characterof which are as follows.
1) Good catch off Sanriku
l 45°E
It is of the general type, namely, the prosperous whaling times are in June off
Sanriku and September off Hokkaido
respectively. Further, the catch of sei
whale off Sanriku is ·better than Hokkaido.
40°N
40°N
2) Good catch off Hokkaido
The prosperous whaling time off Hok22°
kaido is early that is, it is generally in
July, and the catch of sei whale off Hokkaido is better than Sanriku. Then theoceanographic character have been anaLATE OF JULY
lyzed on the situation as of the last ofJuly
1959
in each whaling condition year in which
35 ° .....___,__......__.___._....__.__.35•
a close correlation can be shown between
145°
the catch of sei whale and the oceanographic pattern (especially, the fluctuaFig. 5. Oceanographic conditions oftion of Kuroshio waters).
good catch year in Sanriku.
As shown by Fig. 5 the oceanographic conditions of good catch year in
Sanriku area as 1958, 1959 and 1963 arecharacterized by that the Kuroshio waters
flow towards the north close to the Sanriku coast.
Further, as already stated on previous chapter, the main whaling grounds
located to the west of the northwardly
flowing warm waters, and tend to move145°
l 50°E
towards the north along with the warm
waters.
Fig. 6. Oceanographic conditions
Therefore it must be consideredof good catch year in Hokkaido.

OCEANOGRAPHY OF BALEEN WHALING GROUNDS

167

that the rich catch of sei whale in the yeasrich in the Sanriku area are caused byfollowing.
1) The distribution density of whales increase because of the constrictionof whaling ground area in Sanriku area.
2) The whaling grounds are located near the Sanriku land stations.
On the other hands, the catch off Sanriku area is generally poor in theyears which show the good catch in Hokkaido area as 1955, 1956 and 1963 (seeFig. 6). The oceanographic character in these years is that the northward Kuroshio waters was located more easterly than good catch year off Sanriku.

60°N

so

160°E

180°

Fig. 7.

160°

0

120°w

Locality map of baleen whaling grounds.

Therefore it must be considered that the catch of sei whale in these years arepoor in Sanriku area by following cause.
I) The distribution density of whales decrease because of the expansion of
whaling area.
2) The whaling grounds are located further from the Sanriku land stations.
In addition, the whaling conditions in Hokkaido area are as follows:I) The prosperous whaling time is early in these years.
2) The catch of sei whale is better than Sanriku area.
Their causal explanation must be summarized as follows:I) The locality of whaling grounds which is formed near the northing tonguelike extension of Kuroshio waters become close to Hokkaido land station; because
the Kuroshio waters flow northing far out from the Sanriku.
2) The catch availability of sei whale in the Hokkaido area is larger than
Sanriku in these years.
SUBARCTIC PACIFIC AREA

The main baleen whaling grounds in the Subarctic Pacific area were divided asfollows by the geographic distribution of Aleutian Islands, Alaskan continent andSiberia continent.
That is,

168

I)
II)
III)
IV)
V)
VI)

K. NASU

East area off Kamchatka Peninsula.
Off Cape Navarin and Olyutorski.
St. Mathew Island area.
North area off Unalaska Island.
Southern area of Aleutian Islands.
Gulf of Alaska.

60°N

50°
160° E

160°
~LUE

140°W

AND HUMPBACK WHALEe
Q

BLUE WHALE
HUMPBACK
WHALE

50°~·

60°N

50°
140°W

l 60°E

SE/ WHALE

60°N

50°
160° E

180°

Fig. 8.

160°

140°W

Distribution of whaling grounds by species.

The locality map of baleen whaling grounds shown in Fig. 7 based upon
the catch distribution of fin whale. Consequently, in here the author discussed
the fin whaling grounds, but the distribution of whaling grounds by species in1952 to 1964 also were shown in Fig. 8.

OCEANOGRAPHY OF BALEEN WHALING GROUNDS

169

East area off Kamchatka Peninsula

The whaling grounds in this area were formed to the south and north of Komandorskii Islands and the beginning season of the whaling is most early, late in May,because of the geographic relation to Japan and migrational season of whales.
Moreover the killed whale species consist of blue, fin, humpback and sei whale asshown in Table 1.
TABLE I.

WHALING RESULT IN THE SUBARCTIC PACIFIC AREA
IN THE YEARS 1952-1964
Species of whales caught

Years
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
Total

Blue
55
90
28
23

5
1
0
0
0
0
0
203

Fin
213
470
961
148
595
280
269
694
167
169
3
0
55
4024

Sei
14
98
82
20
47
64
60
7
0
0
0
0
2
394

Humpback
37
42
16
18
35
0
24
0
0
0
0
0
0
172

Total of Whales
319
700
1087
209
678
344
358
702
167
169
3
0
57
4793

In order to obtain the center of whaling grounds the author (1963) used following
formula which was shown by Uda (1930), and discussed the annually fluctuationof it. The annual fluctuation of the number of whales caught in 1 degree of latitude
and longitude were discussed, too.

n;where x and y are the location of caught whale.
and Y is the center of wahling ground.

n is number of whale caught.

X

That is, in the years 1952 to 1960, on the longitudinal fluctuation, two peaks were
found in 1952, 1953 and 1954 during which the operation were carried out overan extended period (the operations in 1956 and 1959 were carried mainly out at thenorthern region of the Komandorskii Islands). These peaks are generally near
164°E and l 74°E, and the highest peak of the longitudinal catch was found near
164°E. The peaks of the latitudinal catch were found 52°N to 53°N. Next, themean position of the center of whaling grounds in the years 1952 to 1960 locate
near 52°N, 165°-30>E, but the annual fluctuations of it were comparatively large.
Figs. 9 to 14 show the distribution of sighted fin whales and surface temperature
obtained by whale chaser in May and June.

170

K. NASU

May: 1955 {see Fig. 9).-The isotherms run roughly paralled to Kamchatka
Peninsula, but the 3.5°C-line extend to the north and south with some meander.
Fin whales were found in the waters of less than 3.8°C in surface temperature andthe greatest concentration of whales was located in the waters which were characterized by 3.5°-3.8°C. Whaling grounds were also located in the cold waters ofless than 2.5°C in surface temperature. It seems to author that the whaling grounds
which are located near 2.5°C are minimum temperature are as for whaling in the
Subarctic Pacific Ocean.
160°E

l60°t

165°

165°

KOMANDORSKI IS.

~~55"N~ ~55°N

J

4.o·

so·

so·

so·

so·
3.2°

3.o·

l 60°E165°

Fig. 9. Distribution of sighted fin whales
and surface temperature (QC) in May of
1955.

~--

l60°E

---------~

Fig. 10. Distribution of sighted fin
whales and surface temperature(QC) in May of 1959.

1959 (see Fig. 10)-The distribution of isotherms generally run parallel to Kamchatka Peninsula similar to 1955, but the temperatures in the vicinity of Peninsula
are higher than 1955. According to Fig. 9 and 10 the whales were sighted in thewaters of 3.2°-3.5° surface temperature and were not sighted in the cold waters ofless than 3.0°C, as in 1955. The surface temperatures in the area from the eastof Kamchatka Peninsula to the south of Komandorskii Islands in 1959 generally
were higher than 1955 and the fin whales were distributed further to the north ascompared with 1955.
1960 (see Fig. 11 )-The oceanographic character of this area in 1960 that the isotherms of 2.6°C to 3.0°C meandered in the vicinity of 52°-54°N, and the cold watermass near the Kamchatka Peninsula extended to the east. In general the surface
temperatures were colder than in 1959 being similar to 1955. The fin whales weresighted more south to the region than in 1959.
June: 1955 (see Fig. 12)-The temperature at surface rised remarkably, andgenerally were more than 3.0°C as compared as in May. The isotherms run parallelto the Kamchatka Peninsula like May, but the disposition of them differed greatly.
That is, the patterns of temperature are summerized as follows,

OCEANOGRAPHY OF BALEEN WHALING GROUNDS

171

I 60"EKOMAN DORSKI IS.
55°N~ 55"NKAMCHATKA

50 • .__......__,___.._...___.__.___.._.__...__. 5 o·
I 60"E

Fig. 11. Distribution of sighted fin whales
and surface temperature (°C) in May of
1960.

May : lower in west and higher in east
June: higher in west and lower in east.
And it also differed in that during May the cold area which was characterized byless than 5.0°0 in surface temperature was located near the Komandorskii Islands.
The areas where fin whales were moved from the adjacent waters of the Kamchatka Peninsula in May to the waters south of the Komandorskii Islands where,
as stated above, was found cold area ofless than 5.0°0 in surface temperature which
proved to be the most productive whaling grounds of this season.
I 60"E165"

l 60°E

165"

KAMCHATKAI
PENINSULA55"NKAMCHATKA

55"N

PENINSULA55"N'\::::, (

55"N

4.0"

7.o· 6.5" 6.o· 5S

50•.___.____..___,___.._...___..___.._....__,5 0.
160"E

165"

Fig. 12. Distribution of sighted fin whales andsurface temperature (°C) in June of 1955.

50•.___,__..__,__.___,_......__,___.._.__....__,___.50•
I 60"E165"

Fig. 13. Distribution of sighted fin whales andsurface temperature (0 C) in June of 1958.

1958 (see Fig. 13)-The temperatures in this year were especially low, and thewaters with less than 3.5°0 at surface covered extensive areas to the south of Ko-

172

K. NASU

mandorskii Islands as May in 1955, 1959 and 1960. The pattern of temperature
distribution was lower in the west and higher in the east as in May of ordinary years.
The notable cold area which was characterized by less than 2.2°C at surface was
located to the north of Komandorskii Islands.
165°

170' EKAMCHATKA
PENlNSULA

a~o·
55°N

55'N

ATTU I.
7.0'

s:::::i

6.0'

165'

170'E

Fig. 14. Distribution of sighted fin whales and surface
temperature (°C) in June of 1959.

l 60' E

170' Eoo 0 ooo ooooooooOQoo

N~M1Bi~ OF l:IN
WHALE. O
Qio~ 3 o

55' N

0Q30~60060-l 00

50'N

000000000000()~

0000000o o o o o Oo o055'N0000000000000

Q100<

0

0

\S,

OQQo oO~OQQOOO

0

0

0

o OOo
50'N

oQoo oo
160'E

Fig. 15.

170.E

Distribution of fin whales caught in the years 1952 to 1964.

Fin whales were sighted at the comparatively south sea region with 2.5°-3.0°C
at surface temperature as similar to 1955 which was a colder year.

OCEANOGRAPHY OF BALEEN WHALING GROUNDS

173

1959 (see Fig. 14)-As already evident from the distribution of temperature in May,
this was warmer year and especially the warm water mass with temperatures higher
than 6.0°C conspicuously extended to the northeast of the Komandorskii Islands.
l 60° E

I 6S

0

170°

I 7S

0

I

\

////UPWELUNG AREA--

SURFACE
CURRENT

ss· •

/

so·

I 60°E
Sf ATION I 7

~

O

~ 100

UJ

t

---

~CTION A

/

170°
I8

~

l9

\\

20

l

so·

175°

9
SALINITY 1%.J~.~3.12~3.4~3.20
~33 6
33.22
-

/3.80~~~

0200

Fig. 16.

~~

Oceanographic structure in the east area off Kamchatka Peninsula.

The concentration fin whales were sighted in the warm sea region which was
located to the northeast of Komandorskii Islands and was not sighted in the region
east of the Kamchatka Peninsula.
Fig. 15 shows the distribution of caught fin whales in the years 1952 to 1964.
As already reported by Nasu (1963), it is well known that the center of fin whaling
grounds were located in the region of 51°-54°N, 162°-166°£. In order to analyze
the oceanographic structure of this sea region. Fig. 16 was drawn by use of the174

K. NASUoceanographic data obtained by NORPAC survey.
The distributions of temperature and salinities are shown at 50 m of depth.
The author presumed that the feeding depth of baleen whale is less than 50 m,
because of the papers of Marr (1957, 1962) and Nemoto (1959). The surface
currents which are shown by arrows were based on the current map by Taguchi(1956), Uda (1963) and Dodimead et al. (1963).
From these figures it was evident that the favourable fin whaling grounds
coincided with the isolated cold area which formed the anticyclonic eddy. The
lower figures in Fig. 16 show the profile of salinity and at along the section A. As
Kato (1958) already reported. Fig. 16 shows that the upwelling area was locatednear the center of anticyclonic eddy.
166°

167°

168°E

ILONGI!YEARl

1957

<
3 600
z

;:;::

'58

400

0

'z"
0

'59

200

'60
1955
COLD
YEAR

·57

·59
COlD
YEAR

1YEAR!
COtD
YEAR

Fig. 17-1. Annual fluctuation of surface temperature and catches of fin whales.
Fig. 17-2. Annual fluctuation of intensity of Alaskan stream (After Koto 1964).

Consequently it may be considered that the whaling grounds south of Komandorskii Islands were formed by the dynamic upwelling which was caused by the
anticyclonic eddy. As already shown, the whaling grounds in May, theearly seasonof whaling, were located in the waters with 2.0°-3.8°C surface temperatures.
To analyzed the salmon fishing grounds in this sea region, Taguchi (1956)
divided to coastal and offshore waters in May and June by surface temperature as
follows:
Water masstemperature (0 C)
Coastal waters> 4.0°C
Offshore waters< 3.0°C
According to this division, the whaling grounds in May were located at the
mixing area between the coastal and offshore waters, and shifting to the east withthe progress of thewhaling season. The author has analysed the situation in thisregion for the years 1955 to 1960. A close correlation was found between the water
tempterature and fluctuation of fin whale catches. That is, from Figs. 9, 10, 11,
12, 13, and 14, the tendency are summarized as follows.
The colder year (1955, 1958, 1960).
Whaling grounds were located towards the south.
The warmer year ( 1956, 1959).
Whaling grounds were located towards the north.
Fig. 17-1 shows the relation between the annual fluctuation of surface temperature and fin whale catches. According to Fig. 17-2 it may be considered that

OCEANOGRAPHY OF BALEEN WHALING GROUNDS

175

the annual fluctuation of water temperatures were introduced by the intensity of
the Alaskan stream. Namely, the western extension of the Alaskan stream in warm
years was located more westerly than in colder years. As shown by Fig. 16 ,thewarm water masses which extend from the region east of the Kamchatka Peninsula
to the region north of the Komandorskii Islands are closely connected with the
Alaskan stream.
Off Cape Navarin and Olyutorskii

The catch from these sea regions was only fin whales, and the whaling seasons
were from late July to the middle of August. As shown by Table 2, the fin whale
catch off Cape Navarin was greater than off Olyutorskii. The total number ofwhales caught off cape Navarm was compared to 128 off Cape Olyutorskii.
180"

175°

60"N

180"

175°

Fig. 18. Distribution of sighted fin whale and surface
temperature (°C) in July of 1958.
TABLE 2.

WHALING RESULT OFF CAPE NAVARIN AND
OLYUTORSKII (FIN WHALE).
Sea region

Year
1957
1958
1959
1960
1961
1962
1963
1964
Total

Olyutorskii
6
47
0
75
0
0
0
0
128

Navarin
175
275
0
0
0
81
0
0
531

Total
181
322
0
75
0
81
0
0
659

July of 1958: According to Fig. 18 which was drawn from the results of whale
marking survey, the isotherms near 62°N extended towards the east. This can beconsidered the result of the cold water mass which was formed by the melted-ice

176

K. NASUin the vicinity of Siberia mainland. From the distribution of 7.0°C isotherm whichmeanders north and south, it was clear that there is oceanic front between the
Bering water masses and the water masses covering the Alaskan continental shelf.
The fin whales were sighted mainly along the oceanic front.
Augustof 1958: Fig. 19 shows the distribution of temperatures and salinities
at the surface based on the data from the results of whales marking survey. The
temperatures covered from off Navarin to the Gulf of Anadyr raised about 2.0°C
over those July. The isotherms ran roughly parallel to Cape Navarin, and thecold water masses extended to the south. The fact that the cold water mass which
11s w
0

65°N

65°N

32.00
~17~5.,.--E~-'---'-~-I~80~
0 -'---'-~~-I7~5°,.--W~ 6 o0Fig. 19. Distribution of sighted fin whale and surface
salinity (%,) in August of 1958.

extended to the south was caused by the melted-ice waters in the vicinity of Siberiancontinent is clearly shown by the distribution of salinity. That is, the distributionof cold water masses which were characterized by less than 8.0°C at surface corresponded to the waters with salinity less than 31.40%0.
Many fin whales were sighted near the mixing zone between the water massof low temperature and salinity along the Siberian continent, and the Bering sea
water mass of relative high temperature and salinity.
Fig. 20 shows the schematic map of the distribution of fin whales caught in theyears 1957 to 1962. The oceanographic conditions, and the surface currents weredrawn by use of the papers of Fleming (1955), Uda, (1963), Dodimead & Hirano(1963) and Nasu (1963). The main fin whaling grounds were located from themixing zone to the south area. From the vertical section of temperature along the
L-line as shown in Fig. 20, it can be found that there is the notable vertical boundaryof the water masses.

Off Cape Olyutorskii
The catch from off cape Olyutorskii was small as shown in Table 2, and the

OCEANOGRAPHY OF BALEEN WHALING GROUNDS

60°

177

60°

180°

175°W

n

~
I

100

§;
0

200

Fig. 20. Schematic map of the distribution of fin whales in the years
1957 to 1962 and the oceanographic structure.

whaling seasons were short.
From the distribution of surface temperature in 1958, it may be consideredthat the zone of eddy was west of Cape Olyutorskii (see Fig. 21-3). Moreover, it
was noted that the whaling grounds in 1958 and 1960 were located west of Cape
Olyutorskii (see Fig. 21-1, 2). This can be summarized as follows: The formationof whaling ground was result of the topographic back eddy was located west ofCape Olyutorskii by the southward current along the Siberian continent.
St. Mathew Island area
Fig. 22 shows the distribution of fin whale caught in rich years (163 animals
in 1957, 399 animals in 1959). The whaling grounds were located roughly samesea region, and the area of abundance of whales corresponds to the edge of continental shelf.

K. NASU

178

1 70° E

C.OLYUTOR
0

bU N

3

22 J 360°N

15 l 11 I
351958)= 1957

1 70° E

1 70° E

60°N

60°N

1960
1 70° E

170°E
C.OLYUTOR~9.0°-~9.2°

60°N

..--

9.6°

170°E

Fig. 21-1. Whaling grounds in 1958.
Fig. 21-2. Whaling grounds in 1960.
Fig. 21-3. Distribution of surface
temperature in August of 1958.

From Fig" 22 the whaling grounds located at the oceanic frontal zones between
the water masses covered the continental shelf to the Alaska and the water mass
upwelled at the edge of shelf. The oceanic front was distributed nearly along the
200 m isobathymetric line" As already stated, the whaling grounds located nearlyin the same area every year. It may be considered that the whaling grounds wereat the oceanic front which was formed by the topographic upwelling"

Northern area off Unalaska Island
The whaling operations in the area north of Unalaska Island by Japanese ex-

OCEANOGRAPHY OF BALEEN WHALING GROUNDS
l 80'

l 75'W'-.. l 0 22 (4

l 70'
I

~..

ST.M~THEWI.

18 55 27\~8\-··r:.

6 0'N

lOOm

<

,l 2 \ )
200m

1957

'V

l so·

l75°W

l 70°

l 80°

l 75'Wl 70''31 .. \59 d2 6

60'N

179

'CJ

4 ~. 89 33\

ST.MATHEW I.

,,,.,....

12 25·4334

60'N

lOOm

l..v2oom

l 959
l 80'

l 75'Wl 70'

Fig. 22. Distribution of fin whale caught in rich years, 1957
and 1959.

peditions began in 1954. As shown in Table 3, the fin whale is the most important
species of whale caught here. The catch from this region reached a maximum in
1955 with 1,177 animals. In 1963 and 1964, however, this catch decreased to 1
and 3 animals, respectively. A possible explanation maybe that the body lengths
TABLE 3. NUMBER OF WHALE CAUGHT BY JAPANESE EXPEDITIONSIN THE NORTH AREA OFF UNALASKA ISLAND IN THE YEARS
1954 TO 1964
Year
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
Total

Fin
584
1,177
744
286
298
703
670
422
115
I
3
5,003

Species of whales caught
Humpback
6
10
0
0
0
0
0
0
0
0
0
16

Total of whales
590
1,187
744
286
298
703
670
422
115
I
3
5,019

of whales taken in this area were smaller than other regions (see Table 11), and thewhaling operations in the Gulf of Alaska has been carried on from 1961.

180

K. NASU
170°W

July.

55°N

l.5° 55° N
00

/.Oo
0

0
o0

0

°
0

0

·: :··:~}JOy

UNALASKA I

~
170°W

Aug.

9.00

00

00
0

]70°W
170°W

165°

Sept.

55°N

Fig. 23. Distribution of sighted fin whales and the surface
temperatures in July, Augut arid September of 1955.

The average center of whaling grounds in the years 1954 to 1960 were locatedat 54°N, 169°W. The greatest catch was found between 54°N and 55°N latitude.
In general, the whaling ground north of Unalaska Island are smaller than thoseeast of Kamchatka Peninsula (Nasu, 1963).
July of 1955 (see Fig. 23) : At 56°W, the warmer water mass* which wascharacterized by 8.0°C or warmer at the surface extended towards the east. The

OCEANOGRAPHY OF BALEEN WHALING GROUNDS

181

6.5, 7.0 and 7.5 isotherms were parallel to each other with meandering to the west
and the south. To the south of the warmer water mass, there was cold water
region which was formed by the upwelling due to the effect of the submarine topographic conditions. The favourable whaling grounds located were in the cold
region having surface temperatures of 7.0°C or less.
There was a mixing area between the warmer water mass which flows to theeast on the northern side of Aleutian Islands and the warm water mass which extends
to the west. In Fig. 23, the mixing area having surface temperatures of less than
6.5°C are shown to be favourable whaling grounds (Nasu, 1963).

Fig. 24.

Distribution of fin whales and mixing area.

August ef 1955 (see Fig. 23) : The warmer water mass which was located near
56°N, 196°W in July showed temperatures higher than l0.0°C, and was strongly
extended towards the southwest. The easterly-flowing water mass along thenorthern side of Aleutian Islands also extended tongue-like towards the northeast.
More-ever, the mixing area are characterized waters with less than 8.0°C surface
temperature.
September ef 1955: (see Fig. 23): According to the distribution of surface temperature, the westerly edge of Bristol water mass retreated near 168°W, and themixing area had temperatures of less than 6.5°C. Fig. 24 shows the distributionof fin whales and the mixing area. As already stated, the most fin whales weresighted from the mixing area to the Bristol water mass, and the position shifts monthby month in accordance with the fluctuation of the two water masses, i.e. in Julylying near 171°W and in September lying at near I 69°W.
Fig. 25 shows the vertical distribution of at along the section A. At isolines
of at St. 55 the water mass rise abruptly towards the surface, and St. 55 is locatedat just the edge of 200 m contour line. The bottom topography from this station
to the west became suddenly deeper. Accordingly, the sudden rise of isoline ofat are probably caused by the bottom topogrp,phy. From this phenomenon, it may
be inferred that the whaling grounds of U nalaska Island are formed by the to po-182

K. NASUgraphic upwelling and the mixing area.
57°N

55°

53°1LAT.!

I

e:;
0

Fig. 25. Vertical distribution of a, along
the section A (Fig. 24).

Southern area of Aleutian Islands
The main whaling ground in this area extends to the east and the west as a centerto 50°-51°N. As shown in Table 4, the fin whale is the most important speciesof whale caught in this area, but some blue, humpback and sei whales also were
captured.
TABLE 4.

NUMBER OF WHALE CAUGHT BY JAPANESE EXPEDITION
IN THE SOUTHERN AREA OF ALEUTIAN ISLANDS
IN THE YEARS 1954 TO 1964
Species of whales caught

Year
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
Total

Blue
121
47
69
70
65
69
70
39
13
0
17
580

Fin
167
39
46

500
442
53
52
273
288
7
224
2,091

Humpback
114
89
2
0
20
0
0
9
0
0
0
234

Sei
40
1
102
270
25
203
4
195
0
457
1,298

Total
442
176
118
672
797
147
325
325
496
7
698
4,203

Fig. 26 shows the distribution of sighted fin whales and the oceanographic
conditions. The water mass which extended towards the southwest with tongueshaped may be considered the Alaskan stream. On the other hand, the water mass
which extended towards the northeast may be considered. From the distributionof these water masses the whaling ground seems to be closely associated with the

OCEANOGRAPHY OF BALEEN WHALING GROUNDS

183

oceanic front which is formed between the extention of Alaskan stream and thenortherly branch of Kuroshio water mass. Morever, the fin whales in this groundFig. 26. Distribution of sighted fin whales andthe oceanographic condition.

160°

1so·w

Fig. 27. Distribution of surface temperature and the number of fin andsei whale caught.

generally were captured in the area where the upwelling exists from relatively deep
layer, being especially plentiful near the boundary zone which exists between thesinking and upwelling area (Nasu 1963).
Gulf of Alaska
The Japanese whaling operations in this region were started in 1961. As
shown in Table 5 the catch from this region consists to a great extend of fin andsei whales. The total number of whale caught in 1963 amounted to 1,037 fin
and 945 sei whales which was the greatest catch ever recorded from this area.

184

K. NASUTABLE 5. NUMBER OF WHALE CAUGHT BY JAPANESE EXPEDITIONSIN THE GULF OF ALASKA IN THE YEARS 1961 TO 1964
Species of whale caught
Year
1961
1962
1963
1964
Total

Fin
425
587
1,037
728
2,777

Humpback
0
13
20
0
33

Blue
31
35
57
25
148

Sei
0
61
945
1,082
2,088

Total
456
696
2,059
1,835
5,046

Fig. 27 shows the distribution of surface temperature and the number of fin
and sei whale caught every 1 degree latitude and longitude in July. The cold
water mass which is characterized by less than 10.0°C in surface temperature islocated from near the Alaskan continent to the adjacent waters of the AleutianIslands. It extends eastward to an area northeast of Kodiak Island, where thewarm water mass extending towards the west exists.
SARINITY

14.0'C

31.00

32.00

34.00(%o)

33.00

i2.o

w

10.0

CENTRAL SUBARCTIC

~

~

**)

/

~

:::>

8.0

6.0
150m

4.0
500m

Fig. 28.

Temperature and salinity diagram.

These water masses form the eddy in the east of Kodiak Island where thefavourable whaling grounds was located in 1961 and 1963. The 2-isotherms of 11°C
which extend towards the southwest from the eddy area must be influenced by the
Alaskan stream. The distribution of fin and sei whale caught in 1964 covered thesouthern area of 11°C isotherms.
From the distribution of temperatures it has been found that the zone of eddy
was located near 56°30'N, 144°30'W and 53°N, 149°V\T where the whaling groundswith fin and sei whales were formed. In addition, many sei whales were sighted
in the water with l0°-l2°C in surface temperatures near 56°N, 153°W and 54°N,
159°W respectively during the whale sighting survey in summer of 1964 (Theregions where many sei whales were sighted were shown by the oblique line in
Fig. 28).
Fig. 28 shows the temperature and salinity diagram based on the data obtained

OCEANOGRAPHY OF BALEEN WHALING GROUNDS

185

by Brown Bear in summer of 1955, and Fig. 29 shows the schematic map:of water
masses and the distribution of fin whales caught.

Fig. 29.

Schematic map of water masses and the distribution of fin whale caught.

As already reported by Dodimead and Hirano ( 1963), the water masses inthis whaling grounds are divided as follows;
1) Central subarctic2) Alaskan stream3) Coastal water (it can diveded to A and B)
Whaling grounds in 1961: The main whaling grounds were located in the
Alaskan stream.
Whaling grounds in 1962: The main whaling grounds were located from thezone of eddy which situated in the northeast of Kodiak, near 59°N, l 49°W to thecoastal water B.
Whaling grounds in 1963: As already stated the catch of fin whale in this year
was the highest. The whaling grounds covered an extensive area and were situatedclose to the continent compared with 1961, 1962 and 1964, and also were found near
59°N, 149°W to the northeast of Kodiak Island, similar to 1961 and 1962. The
catch of sei whales in this year also increased, and the main whaling grounds, differ
from that of fin whales being located in the zone of boundary between the Alaskan
stream and the central subarctic water.
From the distribution of annual whaling grounds, the favourable grounds
generally were found in the marginal zone of Alaskan stream. According to Fig.
30 which shows the vertical distribution of at along the section A it can be seem thatthe upwelling area existed in the southern edge of the Alaskan stream. Consequently, the explanation of oceanographic structure in this whaling grounds may besummarized as follows: The whaling grounds in the southern marginal zone of
Alaskan stream were formed by the convergence between the upwelling water mass

186

K. NASU

which was influenced by the anticlockwise gyr and the Alaskan stream.
COASTAlWATER

WATER MASSCENTRAl SUBARCTICAlASKAN STREAMSTATIONo~l~l~T2~D~ll0~-2~1--110~-2~3--~l~I0-~25'------ll~0-_26_ _--i24.~----------25.0100~~~~~==~~
111~--------26.8

I

ffi 200

0~300

lOOL--------'-------------~

Fig. 30.

Vertical distribution of ai along the section A.

The whaling grounds in the northern marginal zone of Alaskan stream wereformed by the convergence between the coastal waters to the Alaskan continentand the Alaskan stream.
As above stated it may be assumed that the dynamic upwelling by the anticyclonic eddy and the Alaskan stream were the important factors in the formationof these whaling grounds.
ANTARCTIC OCEAN
Fig. 31 shows the rough map the whaling ground operatated by Japanese expeditions and the surface oceanographic condition cited from Marr (1964). In addition
Table 6 shows the catch during the recent 10 years from the Antarctic region by
world expeditions.
TABLE 6. BALEEN WHALES CAUGHT IN THE YEARS 1955/56-1964/65,
BY SPECIES (AFTER THE INTERNATIONAL WHALING STATISTICS)
Year
1955/56
1956/57
1957/58
1958/59
1959/60
1960/61
1961/62
1962/63
1963/64
1964/65
Total

Blue
1,611
1,505
1,682
1,187
1,228
1,739
1,116
944
112
20
11,144

Species of whales caught
Fin
Sei
Humpback
25,102
274
1,425
708
25,502673
25,067
2,375
396
1,394
25,687
2,393
26,271
1,332
3,219
4,280
27,299
709
309
4,716
26,364
18,636
5,482
270
13,583
8,256
2
7,306
19,838220,81750,542
7,509

Total
28,412
28,38829,52030,661
32,05034,02732,50525,332
22,22327,164290,282

B.W.U.
14,77914,636
14,77015,324
15,421
16,374
15,22811,306
8,448
7,052
133,338OCEANOGRAPHY OF BALEEN WHALING GROUNDS

187

Area of 105°W-135°W in 1957 season
Fig. 32-1 and 32-2 show the distribution of fin whales caught and the surface
oceanographic conditions in January of 1957. Observation area covered from about
105°W to 130°W. The surface temperature in this area varies from 0.5°C to -0.9°C.
The distribution of pack-ice is extended towards the east from the vicinity of 66°S,
117°W, and it is directed southward very sharply from 66°S, l l0°W. To the westside of the south-western tongue region, the low temperature and salinity watermass is projected towards the north-east. This is probably caused by the of distribution of pack-ice.
00
SOUTH
AFRICA

1964/65

Ill

90°W

90°E
IV

CD @:WHALING GROUND

PACK

v

'.PACK ICE---:WEST WIND DRIFT[}-:EAST WIND DRIFT(f-:ANTARCTIC

150°

Fig. 31.

CONVERGENCE~EW ZEAIAND
180°

AUSTRALIA

150°

Rough map of the whaling ground operated by Japanese expeditions.

It is clear that complicated sea conditions were formed in this region between
the northern and southern moving water masses as evidenced by the map of isotherms and isohalines. The distribution of temperatures in this area varied
abruptly.
The condition of pack-ice at the western part of l l 7°W is not clear, but it
is assumed that the pack-ice is distributed towards southern direction from about

188

K. NASUl l 7°W. In the vicinity of l l 7°W, the high temperature and salinity water mass isfound and at the west part of it, near 128°W, the definite shape running towards
the south-west direction was recognized.
120·

llO"W

GT

65"S

65"S

-o.s·
([[[]) ; WHALING GROUND:.:;,;;.

130"; PACK ICE

120·

120·

1oo·w

110·

llO"W
SALINITY

Fig. 32. Distribution of fin whales caught and the surface
oceanographic condition in June, 1965.

It is clear from these phenomena that the favourable whaling ground are situated near the region of 65°S, l l5°W and 66°-67°S, 108°W. In the neighbourhoodof these two regions the eddies were developed on the oceanic fronts between thewater mass of high temperature and salinity flowing towards the south and the watermass of low temperature and salinity flowing towards the north.

Area of 90°E-35°W in 1961/62 season
Fig. 33 shows the distribution of sighted whales by Umitaka-maru in December
and January respectively in the regions east and west of 20°E. To the east ofSouth Georgia Island, there was warm water mass which flowed towards the south
and a cold water mass which flowed towards the north. In the vicinity of 65°S,
l0°W the low salinity water mass with less than 33.0%0, was clearly influenced by
the melting of ice, extended towards the northeast with definite shape. Fin whales
were sighted near the pack-ice in the low salinity water area.
On the other hand, near 15°E, many fin whales were sighted in the area ofhigh salinity water mass which projected towards the southwest. At 20°E fin
whales were sighted in the neighbourhood of pack-ice (the area ofless than -l.0°C)
which was situated towards the north. Fin whales were also distributed in thewaters of low temperature and salinity which were situated towards the north

189

OCEANOGRAPHY OF BALEEN WHALING GROUNDS

near 35°E.
Generally, it can be assumed from the distribution of temperature and salinitythat the clockwise eddies in the vicinity of pack-ice play a very important role forthe formation of the Antarctic baleen whaling grounds. According to Fig. 34 whichshows the vertical distribution of temperature along the line-A (see Fig. 34), the
3o•w

30°

60° E

FIN WHALES

50°

60°s

.•:c•,• :PACK ICE:FIN WHALE
0
e :SEI WHALE
A :HUMPBACK WHALE

o·

3o·w
Fig. 33.

30°

60°E

Distribution of sighted whales by Umitaka Maru in December and January.
30°

35°

40°

45°

so·

A.C

55°

31 °E

60°s

SIGHTED 25 FIN WHALES

47°S

47° s

48°

48°

500
:r:

>~

1.000

CJ

:. : SEIDEEP WATER

1,500

Fig. 34. Vertical distribution of temperature along
the line A.

x: FIN
49° L . . - - - - ' - - - - - - - ' ' - - - - - - - ' 4 9°
30°
31° E

Fig. 35.

Distribution of surface temperatureand sighted fin and sei whale.

sea region where many fin whales were sighted correspondeds to the upwelling areaof the Warm Deep Water.
Area of 29°E-39°E in 1962/63 season

In the middle of January, the main whaling grounds cons1stmg of fin andsei whales) were in the region of 47°-48°S and 30°-31°E (see Fig. 35). The oceanographic conditions in this area were characterized by a warm water mass (morethan 7.0°C surface temperature) which extended toward the southwest. Most of
fin whales are caught in the relatively colder region (less than 6.0°C) and the sei
whales in the same grounds are caught in the relatively warmer region. The resultsof stomach content observed by the author are as follows: sei whales feed mainly
on Parathemisto gaudichaudi and Euphausia vallentini, and fin whale feed only E. vallentini.
The fin whaling grounds in late of January shifted to the region of 48°-49°S,

190

K. NASU37°-38°E. The surface temperature in the more favourable grounds was less than
4.0°C. The colors of the water were observed 4-6 (see Fig. 36). In addition thestomach content of fin whales consisted mainly of 2 years group of Euphausia superba.
Fin whaling grounds also located in the sea region with 4.0°-5.0°C in surface temperature and with 5-6 in water color. The stomach contents of whales observed
were mainly Euphausia vallentini.

aIIlD : WHALING GROUND::·:::: : E. SU PERBA

Fig. 36. Distribution of surface temperature (QC) andthe color of water.

Fig. 37. Distribution of Eaphausia superba, sighted pigmy
blue and fin whales, and surface temperature (QC).
Dot: E. superba, Vertical line: Pigmy blue and Fin
whale, Horizontel line : Fin whale.

Fig. 37 shows the distribution of pigmy blue and fin whales and the sea condition at surface in middle of January. According to the distribution of surface
temperature, it indicated that there is the clockwise eddy between the warmer watermass with flowing towards the southeast and the colder water mass flowing
towards the northwest. Many pigmy blue and fin whales were sighted in the

OCEANOGRAPHY OF BALEEN WHALING GROUNDS

191

area from the southern tops of the warm water mass to the oceanic front between
the warmer and colder water mass. The stomach contents of fin whales caught
were mainly Euphausia vallentini.
Fig. 38 shows the whaling grounds of pigmy blue and fin whales and thesurface sea conditions in the waters of 30°E-34°E in early of February. In thevicinity of 32°E, the colder water mass having a temperature of less than 2.5°C was
located towards the north. On the other hand, the warmer water mass flowing
towards the south was found in the neighborhood of 33°E.
The fin whaling grounds were situated in the water with 2.5°-4.0°C surface
temperature within the colder water mass. The stomach contents were observedwith Euphausia superba from water of less than 4.0°C, and with Euphausia vallentini
from water of more than 4.0°C.
32°

30°

3~ E

0

47° s

47°5

------

6.0°
48°

6.0°

_/

48°

49°

49°

5.0°

50°

3.0°

34°E

Fig. 38. Whaling ground of pigmy blue and fin
whales and the surface temperature (°C),
Vertical lines: Sighted pigmy blue whale,
Horizontal lines: Sighted fin whale, Dot: E.
superba, Cross ; E. vallentini.

The catch from the zone of the warmer water mass are pigmy blue and fin
whales. The stomach contents of these whales were largely Euphausia vallentini frompigmy blue whales, and Euphausia vallentini and Euphausia superba from fin whales.

Area of 60°W-l0°W in 1964/65 season
The whaling grounds of fin and sei whales and the distribution of surface
temperature are shown in Fig. 39. The Antarctic Convergence and Subtropical
Convergence in Fig. 39 were indicated by the 4.5°C and l4°C in surface temperature,
respectively. As shown in the figure, to the east of South Georgia Island the cold
water mass which has a northerly component of movement covered an extensive
area. In the waters with a center at 22°-23°W the warm water tongue shaped mass
extended towards the south. Favourable whaling grounds of fin and sei whales also
were found in the sea region of 44-48°S, 55-60°W, where the extension of Brazil
Current was located, and corresponded to the zone of Subtropical Convergence192

K. NASU
60'W

580

50'

30'

40°

L6o""'·""'w-,------~--s~o~·--~---4~07'--~---3~0'"·--~--- 53 "Fig. 39. Whaling ground of blue and fin whales, and the surface
temperature (°C).

SO'S

60°

135°

~~
135°

50'S

I 65°E

""

5o·s

60°

.. ·

165°

135'

165'E

34.0~

33.9~

60'S

"~
····~4.0/

33.X:X·:..

~
135'

60'S

e

. {\

165'

Fig. 40. Distribution of sighted fin and minke
whale, and surface temperature (°C), Horizontal line: Fine whale, Verticalline: Minke
whale, Dot: Pack ice.

which was reveiled assumed by 12-l5°C m surface temperature.
Area of 135°E-165° E in 1965 season

Fig. 40 is drawn based on the data obtained by Umitaka-maru in January of
1965. The species of whales sighted are fin and little piked whale, or minke.

OCEANOGRAPHY OF BALEEN WHALING GROUNDS

193

From Fig. 40 it can be seen that the fin whales were sighted in waters of high temperature and salinity, and the little piked whales were sighted in waters of low
temperature and salinity.
Fig. 41 shows the vertical distribution of temperature along the line A of Fig.
40. In Fig. 41 the area of oblique lines shows that the denser region of sighted
whales as observed in the area of 52°S, l5°E in January of 1962, coincided with the
upwelling area of Warm Deep Water.
LAT

50°

55°

60°

65°S

500

I

5::
CU

I OOO

0

I

1·

1500

WA""' :.,, WM"';>000Fig. 41. Vertical distribution of temperature (°C)
along the line A in Fig. 40.

As the analyses in the Antarctic whaling grounds mainly used the dataobtained by Japanese expeditions, the author mostly discussed the relation between
the surface sea conditions and the baleen whaling grounds.
It general can be assumed that the most favourable whaling grounds weresituated in the oceanic front between the warm water mass and cold water mass
with no relation to the latitude. Especially when the clockwise eddies develop along
the oceanic front, the best whaling grounds were found from the top of the tongue
shape of warm water which flowed towards the south to the east side of the cold
water mass which flowed towards the north.
Fig. 42 is the schematic illustration of above-mentioned sea condition. Uda(1954) already analyzed the whaling grounds off Sanriku, and explained as follows: The cyclonic revolving pattern of the tongues of cold and warm currents
corresponds to the centres of the most favourable whaling grounds. It may be dueto the rich zone of the foods for whales. In the southern area of Antarctic Convergence, it may be considered from the vertical distribution of temperature that thefavourable whaling grounds were located in the upwelling zone of warm deep water.

194

K.NASU

It is well known that the zone of high production is found in areas of upwelling.
Uda (1963), Kumagori (1963) and Ishino (1963) already stated the relation between
the Antarctic whaling grounds and the upwelling, Warm Deep ·water.
The catch from the sea-region of 47°-51°S, 24°E-36°E where the whaling
operations have been carried on since 1961/62, and the stomach contents of thesewhales were studied Euphausia superba, Euphausia vallentini, and Parathemisto gaudichaudi
was found to be the primary food. Morever, the relations among the species offood predator (whales) and surface temperature generally are as follows:

WARM WATERSI
COLD WATERS

Fig. 42. Schematic illustration of sea conditionin the favourable whaling ground.

Species of food
Euphausia superba
Euphausia vallentini
Parathemisto gaudichaudi

Surface temperature
Predator (whales)
Fin whale, Sei whale<4.5°C
Pigmy blue whale, Fin whale, Sei whale>4.5°CSei whale>5.0°COn the Antarctic whaling grounds in recent years
As shown in Fig. 31 the baleen whaling grounds in the Antarctic Ocean havebeen shifted from the Pacific sector to the Atlantic sector, and its latitudinal positions
also moved from the vicinity of pack-ice region to the area of Antarctic and Subtropical Convergence. In order to analyze such a tendency the author discussed the fin
whaling grounds which have been operated by the Japanese expeditions. Table 7
shows the whaling results in the individual areas and the catch rate of all areas during
the period 1957/58-1964/65. The largest catch in the season 1957/58 was obtainedin area VI with 4,107 fin whales, or 56.4 per cent of the all area. In the following
two seasons the catch in the area IV varied between 42.1 in 1958/59 and 72.8 percent of the entire area in 1959/60. In Area III the catch amounted to 8,865 fin
whales, or 74.8 per cent of the entire area in 1961/62. Thus in the Antarctic
season 1964/65, in Areas II and III (from 60° west and eastwards to 70° East) a totalof 5,233 fin whales were obtained, or 99.2 per cent of all Area. In area I the result
was only 44 fin whales, 0.8 per cent of all Area. In other areas there was no
whaling activity in the latest season. Consequently, the recent Antarctic whaling
by Japanese expeditions have mostly been operated in the Atlantic sector.

195

OCEANOGRAPHY OF BALEEN WHALING GROUNDSTABLE 7.
Year
1957/58

THE NUMBER AND CATCH RATE OF ALL AREA OF FIN WHALE
CAUGHT IN THE DIFFERENT AREAS OF ANTARCTIC*
II

1958/59
1959/60
1960/61
1961/62

226
(1.9)
2,066
(19.7)
5,003(59.3)
4,346(82.4)

1962/63
1963/64
1964/65

III
832(11.4)
53
(0.7)
797
(9.0)
4,761
(53.5)
8,865(74.8)
7,705(73.6)
3,296(39.0)
887(16.8)

IV
584
(8.0)
3,314
(42.1)
6,477(72.8)
2,044(23.0)
2,764(23.3)
699
(6.7)
7
(0.1)

v
1,130
(15.5)
2,395(30.5)
1,303(14.6)
236
(2.6)

VI
4,107
(56.4)
2,103(26.7)
320
(3.6)
1,861
(20.9)

111
(1.3)

I
628
(8.7)

24
(0.3)
44
(0.8)

( ) : shows the catch rate for the all area.
*. whaling area was shown in Fig. 32.

For the purpose of obtaining the meridional change of fin whaling grounds,
the catch between each 5 degrees latitude is shown in Table 8.
From Table 8 will be seen that the whaling operations in the Antarctic inlater years have been carried on farther north than earlier.
TABLE 8.

CATCH BETWEEN EACH 5 DEGREES LATITUDE IN THE ANTARCTIC(CATCH FROM THE JAPANESE EXPEDITION)

Year
1961/6240°-45°S

1962/63

9
(0.1)
6.5
(0.8)

1963/64

45°-50°S
1,009
(8.5)
2,964
(28.3)
937(11.3)

50°-55°S
6,138(51.8)
6,605(63.1)
6,704(80.5)

55°-60°S
4,008(33.8)
854
(8.1)
617
(7.4)

60°-65°S
547
(4.6)
43
(0.5)

65°-70°s
153(1.3)

A causal explanation may be as follows:
1) Change of oceanographic environment2) Fluctuation of whale population
In the paper, the author discussed the position of the pack-ice. This factor
is important in the formation of Antarctic whaling grounds. Fig. 43 shows theaverage positions of pack-ice in the years 1929-1934 (Mackintosh & Herdman:
1940) and in recent year obtained from the data carried out by Umitaka maru
(shown by U in Fig. 43) and whaling catcher boats (shown by W in Fig. 43).
Fig. 43 shows that the fluctuations of pack-ice in the meridional average position between the previous and recent years were about 1 degree or 60 sea miles
towards the north or south and consequently, it seems that the positions of pack-ice
have not a tendency to change towards the low latitude in recent years.

196

K. NASUIt has been well-known that the baleen whaling grounds in high latitude
mainly were formed in the waters with 1.0°-0.0 in surface temperature, so that theFig. 43. Average position of pack ice in the years 1929-1934(black line) (Mackintosh & Herdman 1940) and recent year
(slender line).

meridional fluctuations of 0°C isotherm at surface was illustrated in Fig. 44 forcomparison to the pack-ice. The data sources used in Fig. 44 were similar to thoseof Fig. 43.

1962U
1965U

ANTARCTICA

Fig. 44. Average position of 0°C-isotherm in the years 1926-39 (black line)(Mackintosh 1946) and recent year (slender line).

The maximum difference of meriditional position between the previous andrecent years was about 1 degree in latitude, or 60 sea miles, and consequently, it
seems that the position of 0°-isotherm have not a tendency to change towards the
low latitude in recent years.
According to these phenomena it may be not considered that the change ofwhaling ground in recent years was influenced by the oceanographic environments
such as pack-ice and surface temperature.

OCEANOGRAPHY OF BALEEN WHALING GROUNDS197

In next, the discussion on the fluctuation of fin whale population was madeon the C.P.U.E. (Catch per unit of effort) in area III and IV, because the fin whales
are the most important species, and occupied more than 80 per cent of the total
catch. Table 9 shows the value of C.P.U.E. on the Antarctic fin whales caught
by the Japanese expeditions. As seen from Table 9 it may be considered that the
population of Antarctic fin whales have been decrease in recent years.
According to these phenomena as already stated by Ichihara (1962), it supposes that the shift of fin whaling grounds were influenced by the relation of demandand supply between the amount of available food and the number of whales.
TABLE 9.
Year
III
IV

ANNUAL VALUES OF C.P.U.E. ON THE FIN WHALES IN AREA III
AND IV (BY THE JAPANESE DATA)
1958/59

1959/60

2.46

2.21

1960/61
2.69
1.64

1961/62
2.57
1.77

1962/63
2.62
1.52

1963/64
1.94

MOVEMENT OF BALEEN WHALE AND
OCEANOGRAPHIC ENVIRONMENT

Generally, the movement of animals was divided into 1) recurrent movement, or
migration 2) none-recurrent movement, or mere movement (hereafter termed movement). As to terms migration and movement of whales. I would refer to the workby Mackintosh (1942) and Nemoto (1959). That is, the migration means the longannual journeys between the cold feeding area and temperate or tropical breedingarea, and the movement is used in the case of the local movement or short journeyin the feeding and breeding areas. In this paper, the movements of fin whales in
the Subarctic Pacific region are discussed. The research on the movement of whales
have been made by the whale marking directly, and by biological survey etc. indirectly.
According to the results of biological and marking investigations on the whales,
it is clear that the blue and fin whales in the southern hemisphere migrate between
high latitude feeding area and low latitude, breeding area (Mackintosh and Wheeler 1929, Mackintosh 1942, Brown 1960). In a addition in the southern hemisphere,
humpback whales also migrates with regularly period (Mathews 1937, Chittleborough1953, Dawbin 1949, Mackintosh 1942).
In the northern hemisphere it is clear from the results of whale marking that
humpback whales migrate between the Bering Sea in summer and the waters of the
Ryukyus in winter. Current maps indicate that theimigrations of humpback between the Antarctic Ocean (Area IV and V) and the adjacent waters to Australia haveno consist relationship to current conditions. Daw bin ( 1956) also reported thatthe direction of current flow appears to be unimportant as the known south-north
movements of humpback whales in the southern hemisphere.
Ing eneral, the important factors for the migration of baleen whales are notexplained, however, the moving mechanism in the feeding area was reported bysome papers. In the Sanriku area Uda (1954) stated that the moving route of whales

K. NASU

198

appears in the zone of abundant food. N emoto ( 1959) also reported that the movement of baleen whales bears close relation with the abundance of food. And further,in the Antarctic Ocean the distribution of blue and fin whales wa; intimately related
to the areas rich in Euphausia superba and other organisms (Kemp & Bennet 1932:
Hardy & Gunther 1935).
MOVEMENT OF FIN WHALES IN THE SUJ3ARCTIC PACIFIC OCEAN

The whale marking survey by Japanese vessels in the Subarctic Pacific has been
carried on since 1953. The migration and movements of fin whales are indicatedby the marking results (Kakuwa, Kawakami & Ito, 1955: Omura & Kawakami,
1956: Kawakami & Ichihara, 1958: Nemoto 1959).
165°

N
55°

N
55°

54°

54°

53°

53°

o<J

v

l 70°W

165°

Fig. 45. Marking results by the Japanese marking research in the northernarea of Unalaska Island, Horizontal line: Frontal zone in August, Verticallines: Frontal zone in September.

Fig. 45 shows the marking results by the Japanese marking research in the northern area of Unalaska Island. In the earlier season, the fin whales which come to
the nothern area of Unalaska Island may be divided into two groups, one of whichmoves towards the adjacent waters to Cape Navarin, while the other group approachs
towards the Unalaska Island with the progress of the season. The latter seems likely
to stay in the vicinity of the Aleutian Islands as will seen from the fact that the movement of fin whales in this region corresponds to the seasonal shift of oceanic
front (see Figs. 23-1, 23-2, 23-3 and 45). It seems that the movement of whales

OCEANOGRAPHY OF BALEEN WHALING GROUNDS

199

in the feeding area generally is influenced by the oceanographic circumstances.
For the purpose of analyzing the movement among the whaling grounds, the instances of comparatively long distances between marked and recaptured position are
shown in Fig. 46. It must be considered that the distribution of the whales caughtI

160' E

l 80°

l 60°

120°W

.-~~-,----~"'~~~--.-~~--rr~~~-,--~~--.~~~-,--~......,

8

7\M
60°N

60'N

~o
5
50°

I

7~o

:::::=-('37-9tcTE

65-~~"'or?,
7

7

Fig. 46.

180°

D

C

6

7

~50'

VANCOUVER 1____5'"

NORTH PACIFIC OCEAN

160° E

7

160°

120°W

Map of comparatively long distance between marked and recaptured position.

shows the movement of it, and so the map of whaling grounds and the monthly
sighted whales show in Fig. 4 7 and 48, respectively. According to five instancesin the Gulf of Alaska the fin whales which came from off Vancouver Island prior toJune tend to move towards the Gulf of Alaska, and it will be seen from the distribution of whales caught that these moving routes run along the marginal zoneof Alaskan stream. In addition Kellogg (1929) already stated that the fin whales
may move between the Lower California and Bering Sea.
The fin whales which moved towards the west along the Aleutian Islands
came to the northern area of Unalaska Island between the Islands (E.F.G. in Fig.
46), and the movement of these whales in general may be related to the eastward
current along the northern area of Aleutian Islands.
The marking results indicate some fin whales which came to the east area off
Kamchatka Peninusula move towards the east area, and those routes also may berelated to the eastward current similar to case of E.F.G. in Fig. 46. Fin whales
which came to the northern area ofUnalaska Island must be divided into two groups.
One group closely follows the oceanic front between the water mass covering thecontinental shelf of Alaska and the water mass upwelling at the edge of shelf in anorth-westerly direction as far as near Cape Navarin. The other group must staya long time in the northern area of Unalaska Island. In addition, as will be seenfrom Table 10 it seems that the staying group is characterized by the high percentage of young and lactating whales.
Therefore, it supposes that the group which moves towards the north consists
comparatively of older whales.
The reasons why the whaling ground in the northern area of Unalaska Island

200

K. NASU

was formed by the special biological group are obscure. Consequently, the author
thinks that the analysis of the relationship between the physiology and ecology ofwhales and the oceanographic environment is a very important problem for thefishery oceanographic study of whaling grounds.
160°
120'W
70" N IT~:-::::::-,,r='"""'C-'-'rc-H-U-IC_C_H.-1-----,--'-T-'"---------'-'i'~"-----~---,70' N
SEA

NOS. SHOW MONTH>< DISTRIBUTION 0 F SIGHTED
GRAY WHALE IN AUGUST
OF 1955...

I·;:,":WHALING GROUNDS OF
FIN WHALE

60'·v11-v111
BERING SEA

..

.

VI-IX

"

\ir.:_rx· o.....

-~·0 ;·~,;.,;,;,o·:ob·~-~-O~.

GULF 0 F AlASKA·. ·: "'.: · ·": ·. vr:_:vi1 · ·

so·

50'

NORTH PACIFIC
160"E

180°

Fig. 47.

160°

120° E

Map of monthly whaling grounds.

TABLE 10. AVERAGE SIZE, IMMATURE RATE, AVERAGE OVULATION AND
LACTATING RATE OF FIN WHALE CAUGHT IN THE SUBARCTIC PACIFICOCEAN BY INDIVIDUAL AREA 1958 (AFTER NASU 1959)
Area*
I
II**
. IV

v

Average size
(feet)
60.5 63.1
60.6 63.2
59.4 60.8
60.8 62.6

Immature rate

18.8 27.6
20.6 23.0
41.5 54.6
25.0 32.4

Average Ovulation

8.1
8.0
5.6
6.3

Lactating rate*

5.6
3.8
12.5
3.2

* Shown in Fig. 8.
* * Off Cape Navarin.
number of Lactating whale** * Lactating rate = number of female mature whale X 100%
North-bound fin whales which travel up to the Bering Sea in summer season
were seen in the Chukchi Sea, where few already were observed in July, and someof them were staying until October (Nikulin 1964). According to the results ofsurvey in 1937 and whaling operation in 1940 by Japanese expedition it seems thatthe number of fin whales in the Chukchi Sea decreases from the middle of August,on the contrary the gray whales increase. Such a tendency also was indicatedby the survey carried ouf on 16-20, August of 1958 (The number of the sighted whales
during the survey were as follows: Fin whale: 1, Right whale: 2, Gray whale:
82, Unknown: 1, Total 86). Also most gray whales during the survey in 1958
were sighted in the fin whaling ground operated by Japanese expedition in 1940.

201

OCEANOGRAPHY OF BALEEN WHALING GROUNDS

Furthermore, it is clear from the distribution of physical (temperature andsalinity) and chemical (dissolved oxygen and hydrogen-ion concentration) elementthat the conspicuous oceanic front was formed in the dense concentration area ofsighted whales, of which the marine productivity seems to be high.
160° E

l 60°E

180°

MAY.

CV
60° N

~

j50• N

160° E
SEP.
60° N

132> °o
50° N

QFig. 48.

Map of monthly distribution of sighted fin whale.

Fig. 49 shows the presumed moving route of fin whales, and the distributionof oceanic fronts and current pattern at surface in the Subarctic Pacific Area. In
the Antarctic as already stated in previous chapter, the catch of fin and sei whales
from near 47°S, 57°W were distributed along the southward tongue-shaped extension of the Brazil current. To the south of Antarctic Convergence, fin and sei
whales near 54°S, 22°W were caught along the tongue shaped southward current
indicated by the 2°-3°C isotherms.
In the waters to the north east of Japan, the northwards moving mechanismof sei whaling grounds were influenced by the conspicuous tongue shaped Kuroshio

202

K. NASU

160°

140°

70°N

70°N
-

SURFACE CURRENT-_::,-FIN WHLING GROUND~OCEANIC-FROT

PRESUMED MOVINGROUT Of FIN WHALE

60°

Fig. 49.

Presumed moving route of fin whale and the oceanographic environment.

1<400

145°

150° Ey ~"""~r
100

40°

N
35°

140°

0? ":

9
il0
E<O
I
I

9

l10 E=O 40°~\r~v_)ff (j \) <!J~"~"1'0 B~? .
145°

N
35°

150°E

Fig. 50. Vertical stability in the northeast sea region of Japan, Sanriku to Hokkaido.
Black line whows the Kuroshio current.

waters which projects towards the north. As stated in previous chapter, thedistributions of the sei whales which came to the waters off Hokkaido correspondto the waters which the Oyashio Front projects towards south. Consequently, thebaleen whales in the feeding area have a tendency to move along the oceanic front
and the current which it developes in this region.

OCEANOGRAPHY OF BALEEN WHALING GROUNDS

203

GENERAL CONSIDERATION OF THE
BALEEN WHALING GROUNDS

Generally, the whaling grounds are divided into feeding and breeding grounds.
There are breeding grounds such as humpback whales in the Ryukyu Islands whichwere investigated by Nishiwaki (1959). However, most whalings is done infeeding grounds (especially, in the pelagic whaling grounds). Favourable feeding
grounds of whales are characterized by the special oceanographic structures such as
the upwelling and vertical convection etc. Such oceanographic characters arefound in the waters to the northeast ofJapan, Subarctic Pacific Ocean and Antarctic
Ocean.
That is, the vertical convection based on the increase of surface density inwinter was recognized in the whaling grounds by the existence of intermediate cold
water (Uda 1935, 1955, 1956, 1963, Nasu 1957, 1963). The upwelled deep waters
in the euphotic zone form the notable spring layer of density by the increase of
surface temperature or the melted-ice waters. For the purpose of obtaining thedepth of spring layer, the vertical stability in individual sea region shown in Fig.
50, 51 and 52. As Elizarov (1963) also stated on the sea region at Newfound Banks,
the vertical stability is a very imprtant element for the formation of fishing grounds.
In the Antartic, Halse (1956) stated that the large phytoplandton populltions wereconfined to a surface large of 25-50 m, which coincided with the pronounced stablelayer, Nasu (1963) also pointed out that the vertical stability is the important factor
for the formation of whaling grounds.
Of course, the oceanographic analysis of whaling grounds must include thestructure of deep water, however, from the results reported by Marr (1957, 1962)
and Nemoto (1959) the author presumed that the feeding depth of baleen whaleis less than about 50 m. Consequently, the vertical stability is within 100 m in
Antarctic, Subarctic Pacific and Northeast area of Japan as shown in Fig. 50, 51
and 52. For the calculation of vertical stability the following approximate formula
was used:
E = lo-a dat
dz

Where Eis vertical stability, at is density of sea water, and Z is depth). As will beseen from these figures the maximum layer of E in the favourable whaling grounds
generally existed at depth less than about 50 m which roughly corresponded to the
maximum layer of dissolved oxygen. This may be explained by an upwelling
water mass during the winter seasons supplying the surface layer, where phytoplankton increase. Halse ( 1956) stated that in the Antarctic zone, with its pronounced
stability, the large phytoplankton populations were confined to a surface layer of
25-50 m.
According to Mackintosh & Wheeler (1929), Hardy & Gunther (1935),
Mizue (1951), Peters (1955), Marr (1956, 1962) and Nemoto (1957, 1959, 1963),
it is well known that the staple food of baleen whales is euphausiids. Kemp &204

K. NASU

45°

60°

ANTARCTICA
07s 5

3o·w is·

0

0

is E

30·

45•

60°

75°

90•

Fig. 51.

ios·

i20·

Vertical stability

Bennett ( 1932) stated that the distribution of blue and fin whales in the Antarctic
Ocean is closely correlated with the euphausia distribution. Euphausiids feed
mainly on phytoplankton (Barkley, 1940; Einarson, 1945; Ponomareva 1959) andit also is known that the high concentration layer of diatom exists less than 50 metersin depth (Moberg, 1928; Phifer, 1934 a, 1934 b; Kokubo and Tamura, 1934).
Consequently, the baleen whaling grounds seems to be closely related to the
maximum layer of vertical stability.
170°

160° E

180'

?

~

60°

O'\

6Q Q

;)

SEA

(? 00
(/

(I

'?

~v
J

N
so·

y

·,·:';~''il/'~(~'"<y_;,J: o.,~-iP

d

11

~
160°E

)

,)

y'Yos':>..,,

y

14o·w

I SO'

Q

? Y'
<?
(°/
' BERING

60°

160'

170°

J

V

S:

<>

<)

LJ

lJ

::;u

D

9

160°

1so·

/)

'L

v

c;?

J

N
so·

']
170°

Fig. 52.

180'

170°

14o·w

Vertical stability in the Subarctic Pacific Ocean.

As already discussed in previous chapter it is clear that the favourable whaling
grounds correspond to each special three-dimensional oceanographic structure.
Especially favourable whaling ground are formed in the zone of dynamic eddy along

OCEANOGRAPHY OF BALEEN WHALING GROUNDS
135°

150°

165°

l so·

165°

150•

135°

120·

1 05·

205

90· 75•w

i

45°

()
'
;
__
--.::.J\!
•ANTARCTIC~u
VV :_,,,;---........ QCONVERGEN.CE
60°
0i .1 0---11 0 0 0' l 5 -1--l__-----··q_,,0 _____ _o o o ~ 0ii::? <? 9oc:?
9--~-l__n0

ROSS SEA__.____.__~........_~__.~~...._~_._~__.___._.....____._~___.--__.15·s
135°

iso·

165°

iso·

165°

iso·

135°

120·

los•

90•

1s·w

in the Antarctic Ocean.

the oceanic fronts between the water masses. Topographically-developed backeddy systems also are good whaling grounds as shown in the vicinity of South
Georgia (Hardy and Gunther 1935) and the Cape Olyutorsokii in the Bering Sea.
The good whaling grounds also were found in the area of upwelling caused by thesubmarine topography and gyre.
The oceanographic character of the baleen whaling grounds can be summarized
as follows;I) Oceanic front type
Off Sanriku and Hokkaido
Polar Front between the Oyashio and Kuroshio
waters.
Subarctic Pacific
Oceanic front between the melted-ice waters
East area off Navarinof the Siberia Continent and the Bering warm
waters.
Oceanic front between the westward Alaskan
Southern area of
stream and eastward West Wind Drift.
Aleutian Is.
Oceanic front between the southward warm
Antarctic
water mass and northward melted-ice watermass in the vicinity of pack-ice.
Antarctic Convergence
Subtropical Convergence2)

Eddy typea) Dynamic eddy

Eddy develops along the oceanic . fronts, andfound in the Antarctic, Subarctic Pacific, and
off Sanriku-Hokkaido.

206

K. NASUb)

Topographic eddy
Subarctic PacificWest of Cape Olyutorskii

Antarctic
South Georgia
3)

Upwelling typea) Dynamic upwelling
Subarctic
East area of Kamchatka
Peninsula
Gulf of Alaskab) Topographic upwelling
Subarctic
St. Mathew I.
Unalaska I.
Antarctic
South Georgia I.

Back eddy which was formed at the west ofCape by the southward current along theSiberia continent.
Back eddy which was formed at the east ofisland by the West Wind Drift.

Upwelling by the anticlockwise gyre.
Upwelling by the anticlockwise gyre.

Upwelling along the edge of continental shelf.

"

"

"

Upwelling in the vicinity of the Island.
SUMMARY

In this paper the formation mechanism of whaling grounds and the movement ofballen whales were discussed from the view point of fishery oceanography.
1) The concentrated sei whales off Sanriku coast in last of April came along
the waters of 12.2-13.0°C which corresponds to the southern area in the Polar Frontal Zone.
2) Favourable whaling seasons of sei whale in the east sea regions of Japan
are in May to June off Sanriku area and are in September to October off Hokkaido,
respectively. It may be considered that the moving mechanism of whaling grounds
from off Sanriku to Hokkaido were influencd by the conspicuous tongue shaped
Kuroshio waters which project towards the north.
3) In the east sea regions of Japan there are two whaling condition types.
Good catch off Sanriku-It is general type, the prosperous whaling season are inJune off Sanriku, and the catch of sei whale off Sanriku is better than Hokkaido.
The oceanographic conditions were characterized by that the Kuroshio waters
flowing towards the north close to the Sanriku coast.
Good catch off Hokkaido-The prosperous whaling seasons generally are in July,and the catch of sei whale off Hokkaido is better than Sanriku. The oceanographic
character in these years is that the northward Kuroshio waters are located moreeasterly than good catch year off Sanriku.
4) The main whaling grounds in the Subarctic Pacific Ocean were divided
into six areas by the geographic distribution of Islands and continents etc. i) EastOCEANOGRAPHY OF BALEEN WHALING GROUNDS

207

area off Kamchatka Peninsula-it may be considered that the whaling grounds inthis region were formed by the dynamic upwelling which was developed by the
anticyclonic eddy.
ii) Off Cape Navarin and Olyutorskii-The whaling grounds off Cape Navarin
were located near the mixing zone between the water mass of low temperature andsalinity along the Siberian Continent and the Bering Sea water mass of relative
high temperatured and salinity. The formation of whaling ground off Olyutorskii
was the result of the topographic back eddy which was located at the west of Cape
Olytorskii.
iii) St. Mathew Island area-It may be considered that the whaling grounds wereat the oceanic front which was formed by the topographic upwelling and the watermass covering the continental shelf to the Alaska.
iv) North area off Unalaska Island-It seems that the whaling grounds was formedby the topographic upwelling and the mixing area.
v) Southern area of Aleutian Islands-Many fin whales in this area were captured
mostly of in the upwelling area from the relative deep layer, being especially plentiful near the boundary zone which exists between the sinking and upwelling area.
vi) Gulf of Alaska-It may be assumed that the dynamic upwelling by the anticyclonic eddy and the Alaskan stream were the important factors in the formationof the whaling grounds.
5) The results of oceanographic analysis in some Antarctic whaling grounds
were summarized up as follows. The favourable whaling grounds were located in
the oceanic front between the southward warm water and northward cold water,
melted-ice water. To the south of Antarctic Convergence, the favourable whaling
grounds corresponded to the upwelling zone of Warm Deep Water.
6) The whaling operation in the sea-region of 4 7-51°S, 24°E-36°E have been
carried on since 1961/62. The stomach contents of whales caught in this area
were found to contain Euphausia superba, Euphausia vallentini, and Parathemisto gaudichaudi.
Morever, the relation among the species of food, predator (whales) and surface
temperature was as follows :Species of foodE. superba
E. vallentini
P. gaudichaudi

Fin whale, Sei whale
Pigmy blue whale, Fin whale
Sei whale
Sei whale

Surface temperature<4.5°C>4.50°C>5.0°C

7) The whaling operations in the Antarctic in later years have been carriedon further north than earlier. A possible explanation may be 1) Change of oceanographic environment 2) Decreasing of whale population. According to theresults in this paper, as already stated by Ichihara (1962) it supposed that the shiftof fin whaling grounds were influenced by the relation of demand and supply between the amount of foods and whales ensuing the diatom of whale population.
8) The baleen whales in the feeding area have a tendency to move along theoceanic front and the current which develops in local regions.

208

K. NASU9) The favourable whaling grounds seems to be closely related with the maximum layer of vertical stability.
10) The oceanographic character in the baleen whaling grounds can be summarized as follow :2) Eddy typea) Dynamic eddy develops along the oceanic eddyb) Topographic eddy3) Upwelling typea) Dynamic upwelling develops in the anticyclonic (northern hemisphere)
or cyclonic (southern hemisphere) gyreb) Topographic upwelling
ACKNOWLEDGEMENT

I am much indebted to Dr. Hideo Omura, the Director of the Whales ResearchInstitute for his kind support throughout this work. Dr. Masaharu Nishiwaki,
Professor of the University of Tokyo, has kindly given me valuable suggestion on
this work. This work could not have been written without the materials collectedby Dr. Takahisa Nemoto, Dr. Seiji Ohsumi, Dr. Tadayoshi Ichihara, and Mr.
Toshio Kasuya.
The author is greatly indebted to Dr. Y oshio Hiyama, Professor of the U niversity of Tokyo, who gives me kind advices; and to Dr. Michitaka Uda, Professor of theTokyo University of Fisheries, for his kind constant guidance throughout this work.
I appreciate very much the helpful discussions on the methods for analyzing
the whaling grounds with Dr. Yasukazu Saito and Dr. Makoto Ishino, Assistantprofessors of the Tokyo Universitys of Fisheries. Grateful acknowledgement ismade to the Japanese whaling inspectors and the staff of the whaling company who
cooperated in the observation. Thanks are also expressed to Dr. W. J. Houck,
Professor of Humboldt State University, who assisted in editing this paper.
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