OCEANOGRAPHY AND WHALING GROUND IN THE
SUBARCTIC REGION OF THE PACIFIC OCEAN
KEIJI NASU
INTRODUCTION

Oceanographic observation in the whaling grounds have been conducted for someyears past on board the whaling factory ship "Kyokuy6-maru" and whale marking research boats. The work is carried out in the Chukchi Sea, Bering Sea andnorthern part of North Pacific Ocean with temperature by bathy thermographand some serial observations.
Some aspects of the data obtained by these surveys were discussed in previous
papers (Nasu 1957, 1958). Uda and Nasu (1956) discussed the whaling grounds
in relation to meteorological and oceanographic conditions. Nemoto (1957, 1959)
also had reported in detail on the subject from the point of the food of baleen
whales and the ecology of plankton. The present paper gives the oceanograhpic
structure in the whaling grounds and on the physical and chemical environment
connected with the distribution of whales, using data obtained by whaling expedition cruises as well as sources.*
In this paper the vertical and horizontal distribution of water mass in thewhaling grounds were examined.
The author is of the opinion that the vertical stability of sea water is also an
important element for the formation of the whaling grounds.
ACKNOWLEDGEMENT

Grateful acknowledgement is made to the Japanese whaling inspectors and thestaff of the whaling company who co-operated in the observations.
Acknowledgement is also made to my colleague Mr. Takahisa Nemoto, Mr.
Seiji Ohsumi and Mr. Tadayoshi lchihara who assisted in the collecting of theoceanographic data.
The author is greatly indebted to Dr. Michitaka Uda, Prof. of the Tokyo
Univ. of Fisheries, who gave me kindly advices.
Sincere thanks are also expressed to Mr. J.E. Pearce who assisted in editing
the paper.
DISTRIBUTION OF WHALESAs already reported by several scientists (Townsend 1935, Matsuura and Maeda
1942, Nikulin 1946, Sleptsov 1955) the larger whales in the northern part ofNorth Pacific, Bering Sea and Chukchi Sea are blue, fin, humpback, sei, right,* Other data were collected by Oshoro-maru and H.M.C.S. Ste Therese in the summer of 1955.
105

~I

106

K. NASU

greenland, grey and sperm whale.
Blue whale (Balaenoptera musculus)
In general, blue whales are found in the northern part of North Pacific except
the Bering Sea. According to Sleptsov (1955), blue whales are found in the south
off Cape Olyutorski, the east off Cape Navarin and the Chukchi Sea. The resultof Japanese whaling operations indicate that blue whales in the Bering Sea arescarce and are found mainly in the southern water of the Aleutian Islands. It
appears, therefore, blue whales in the southern hemisphere have migrated to comparatively high latitude (Mackintosh and Wheeler 1929), but those in the Pacificsector of the northern hemisphere are found in relatively lower latitude. The blue
whales seem to be found dominantly of about 50°N, l 70°W.
Fin whale (Balaenoptera physalus)
Fin whales in the Sub-arctic Pacific sector are the most prevalent species for thestock of whale as is ture for Antarctic whaling and its distribution ranges fromthe North Pacific to Bering Sea and Chukchi Sea. In the Chukchi Sea (a partof the Arctic Ocean), Japanese research vessel, Yiiki-maru found many fin whales(number of whales are unknown) near 66°40'N, l 70°W. on August, 22, 1937 anda Japanese pelagic expedition caught 74 fin whales there in 1940. According to
Nikulin (1946), in C. Serdzekamen and the Bering Sea, 177 fin whales (July:70,
September: 57, October: 50 respectively) were found in 1937. Consequently, as
already stated (Nasu 1960), many fin whales seem to migrate into the Siberianwaters of the Chukchi Sea at least from the early summer to October.
During the summer season, fin whales in the Bering Sea have been observedin all areas except the central part about 58°N, l 77°E and the east of 200 m
depth contour line (extending north-west from Unalaska I). Moreover, fin whales
were abundant to the north of Unalaska I., (center about 54°39'N, 160°W), near
59°30'N, 170°-00'W and Cape Navarin. Especially, to the north of Unalaska
I. as already shown by Kawakami and Nasu (1956), fin whales were most concentrated. Many fin whales were captured in the waters of Cape Navarin and from someprevious reports, it is considered that the fin whales migrate to the Chukchi Sea.
Some whales were also captured to the west of St. Mathew Island, near 60°N,
l 78°W.
To the south of the Aleutian Islands, many fin whales are distributed in a belt
situation centering around 50°N, l 70°W, where blue, sei, and humpback whales
have been caught, too. Therefore, this sea region is important for whaling operations, but the annual whaling condition there is unstable.
As already shown by Nemoto (1959), many fin whales are found in the waters
around the Komandorski Islands, to the east of Kamchatka Peninsula. In thenorthern region of the Komandorski Islands, many fin whales were caught in 1956
and 1959.
In the area south-east of Kamchatka, it is considered that the fin whales alreadyhad migrated in the middle ten days of May. Fin whales were also captured in

1·

OCEANOGRAPHY AND WHALING GROUND IN THE SUBARCTIC

107

the waters off Cape Olyutorski, near 60°N, l 70°E, but the whaling area and catchare both small.
Sei whale (Balaenoptera borealis)
In general, sei whales have been caught in the south region of the Aleutian Islands,
but some whales were observed in the mouth of Anadyr Gulf in August of 1958.
Sei whales are distributed mainly in the waters from the east of Kamchatka
Peninsula to the south of Komandorsky Is. and from 180° to l 70°vV along the
51°N line.
Humpback whale (Megaptera novae-angliae)
Humpback whales are most prevalent in the waters south of the AleutianIslands (especially, east of l 70°W) and are also found in the area north of Unalaska
Island. Form the record of operations of the Japanese expedition in 1940 (101humpback whales were captured) and data obtained by the reserch vessel "Yukimaru" in 1937 (many humpback whales were found, but total number is unknown),
as Tomilin (1935) stated, it is clear that the humpback whales migrated to the
Chikchi Sea. Humpback whales of the Ryukyo waters have close relation to
those of the eastern Aleutian sea area. (Kawakami and Ichihara 1958). Kellogg(1929) advanced the opinion that humpback whales in the west coast of Canada
move as for north as Alaska. However, this has never been substantiated.
Sperm whale (Physter catodon)
Many sperm whales were captured along the Aleutian Islands, and the mostdense area is situated near longitude 180°. Sperm whales were also captured in
the region centered at 56°N, l 70°W. According to data obtained by Japanese
expeditions, few sperm whales have migrated as far as 61°-62°N latitude. Tomilin(1935) stated that the sperm whales did not migrate to the region north of Cape
Navarin. Matsuura and Maeda (1942) determined that the northern limit ofthe distributional region of sperm whale had existed from 50°N to 60°N latitude
by analyzing where whales were sighted and caught.
In general, sperm whales in the Bering sea are considered to migrate as far
north as 60°N latitude. In addition, sperm whales have also migrated to the
Kuril Is., the west of Kamchatka peninsula, and the central area of Okhotsk sea(Sleptov 1955).
WHALING GROUND OF BLUE AND FIN WHALE
1) Blue whale
The author can not discuss in detail the blue whaling grounds because the catch
number have been restricted to 70 whales since 1955; however, the whaling grounds
may be roughly divided into east and west longitude areas. Moreover, as stated
by Nemoto (1959), blue whales have not been captured in the Bering sea. The
whaling ground in east longitude is located in the vicinity of latitude 52°N and108

K. NASU

a narrow area along 51°N. In general, the center of whaling grounds existed
in the vicinity of 52°N, 166°E. Catch in the west longitude was dominant in thearea between 50°N and 49°N and its bound roughly covered from 178°W to 160°W(its Center may be considered to locate near 50°N, l 70°W). The densest area ofcatch was in the Aleutian waters from 170°W to 166°W, centered at 53°N, 165°W.
A few blue whales were captured near 55°N, 157°W in 1960. Moreover, the rateof catch on east and west longitude was about 3 :7 respectively.
2) Fin whale
Number of fin whales caught in the Subarctic Pacific area consist of more than
80 per cent of all whales caught.
Whaling ground of fin whale covered the greater part of the Bering Sea andthe North Pacific Ocean north of 48°N, 12,998 fin whales were captured in theyear 1952 to 1962, and prior to World War II 221 were caught in 1940 and 370
in 1941, respectively (catch in 1940 included 74 fin whales captured in Chukchisea). Number of catch in the vicinity of 54°-30'N, 167°W, north of Unalaska
I. was more than 500 whales in every one degree area for latitude and longitude.
Number captured in one degree square area shows fin whales captured since 1952,
and area more than 100 whales present the favorable ground for convenience andthose named as follows.
1) Off Kamchatka Peninsula2) Off Unalaska Island
3) Off Cape N avarin
4) Southern region of the Aleutian Island
GENERAL BATHYMETRY

Pelagic whaling in the Subarctic Pacific operates around north of latitude 48°N,
in the Bering sea, and the Aleutian Is. The Aleutian Islands form a perfect arcof a circle, and divide the Bering Sea and the North Pacific. The Bering Sea
forms roughly a scalene and its area is about 878,000 square miles (Barnes andThompson 1938).
Fig. 1 is drawn by use of a bathymetric chart published by U.S. Navy
Hydrographic office.
In general, the depth of Pacific side is deeper than that of the Bering sea, andthe deepest area lies parallel to the Aleutian Islands at latitude 52°N, longitude
173°E, where it attains a maximum depth of more than 4,000 fathoms.
The 3,000 fathom contour line lies 60 sea miles off the south of AleutianIslands and extends from l 70°E to longitude 157°W. Consequently, there aresteep continental slope lies in the area from 170°E to 157°W, the south of Aleutian.
Islands.
The 2,000 fathoms contour line lies to the north of the 3,000 fathoms lies andit extends from the central part of Kamchatka Peninsula to the Alaskan Continent,a distance of About 2,000 sea miles east and west. Therefore, the southern con-

OCEANOGRAPHY AND WHALING GROUND IN THE SUBARCTIC

109

tinental shelf of Aleutian Islands is very narrow. The maximum depth of the
Aleutian Rigde lies to the northwest of Attu Island and its depth attains about
1,000 fathoms.
The deeper areas, those exceeding 2,000 fathoms, lie in the southwest part ofthe Bering Sea and the maximum depth is more than 2,200 fathoms at 54°N
l 75°W. The Bowers bank is located at the central part of Aleutian Islands, nearlong. 180° and extends to the north and northwest. The north edge of the 500
fathoms contour line lies along 55°N, and is 12 fathoms at the shallowest point
54°16'N, l 79°30'E. The topography in the eastern and northern part of Bering
Sea has a depth of at least 1,000 fathoms, and an extensive continental shelf exists.
The 100 fathoms contour line extends from the U nimak Pass in the northwest
direction to the south of Cape N avarin.

Fig. I. Bathymetric chart, based on chart published by the U.S. Navy Hydrographic
Office. (Soundings in fathoms)

Bering Strait is less than 50 sea miles wide at its narrow point and is from
20 to 30 fathoms deep. The depth in the Chukchi Sea is almost entirely less than
30 fathoms and has a minimum depth of 8 fathoms in 66°-30'N, 168°-30'W.

TEMPERATURE STRUCTURE
Horizontal distribution

Fig. 2-6 show monthly mean distribution of surface temperature during 1955-1959
every 1 degree latitude and longitude.
May:
In the east off Kamchatka, as already stated by Taguchi (1956), we can recognize

K. NASU

110

cold current (coastal water) which is southerly flowing along the Kamchatka coastalline and warm current (offshore water) which is flowing from the southeast off
Kamchatka Peninsula to the northwest. Taguchi (1956) divided coastal andoffshore water in May and June by surface temperature as follows.
coastal water> (J 4.0°C
offshore water < (} 3.0°C
Fig. 2 shows the distribution of mean surface temperature in May.
Whaling ground in this season, in the off Kamchatka Peninsula is in generalisotherms 1.0° to 3.5°C distributed from NNE to SSW. The isotherm of l.0°C
extends to the east ofOnekotan Island (49°-30'N, 155°£) near the 158°£ longitude,
and isotherms of 2.0°, 2.5° and 3.0°C lie parallel to the isotherms of l.0°C and the
3.0°C line reach to 161°£ longitude. Moreover the distribution of these isotherms
must be influenced by the cold water mass which is transported from Okhotsk Sea.

160'W

Fig. 2.

150'\\"

Distribution of average sea surface temperature (°C) in May.

The coastal water which is characterized by less than 3.0°C approaching to
the Kamchatka in the northern area and the coastal water at near Cape Africa
reaches to only 15 sea miles off the shore.
To the east of the 3.0°C line, the 3.5°C line meanders from the Komandorski
Islands to the southwest nearly parallel to the Kamchatka Peninsula and the watermass is characterized by 3.0° to 4.0°C at surface temperature covers on extensive
area. From the determination of coastal water mass by Tagauchi ( 1956), mixing
area consisted of coastal and off shore water must be extensive.
Oceanographic variation to the east off Kamchatka Peninsula, as stated by

OCEANOGRAPHY AND WHALING GROUND IN THE SUBARCTIC

111

Taguchi (1956), may be considered as due to the influence of those two water masses.
Near 52°N, 162°E the 3.5°C isotherm extends to the west. This is a consequenceof the returning flow (Kitano 1958) which is flowing to the west along the southof the Aleutian Islands.
On the southern side of the Aleutian Islands, isotherms (5.0° and 5.2°C) run
towards the east and west nearly parallel to each other and the distrubution ofsea temperature is characterized by a decrease from the west to the east. In
the northern side of the Aleutian Islands, the 4.0°C-isotherm extended to the eastof the Komandorski Islands with meandering.
The 3.5° and 3.0°C isotherms lie to the north of 4.0°C isotherm and extend
roughly parallel of it.
June
Surface temperature m the east of Kamchatka Peninsula was comparatively

Fig. 3.

Distribution of average sea surface temperature (°C) in June.

higher than that of May. The isotherm of 7.0°C extended towards the east andits eastern edge attained in 53°-30'N, 163°E. The water mass which extended
towards the east is characterized by low water color and coastal water mass. Moreover, surface temperature was higher in coastal water and lower in offshore watermass.
Temperature at 0 and 30m depth in July of 1957 was as follows.
Depth (m)Coastal water (Be)030

Off shors water (Bo)

8c
8c

>
<

80
80

112

K. NASUHigher temperature in coastal water may be influenced by geographicaldifference of surface heating by solar radiation.
In the vicinity of the Komandorski Islands the 5.0°C-isotherm is located andlargely meanders along the northern side of the Aleutian Islands. The southernside of the Aleutian Islands isotherms (5.0° and 5.5°C) run to east and west, andat the south of the Aleutian ridge there is cold water mass which is characterized
by less than 5.0°C.
To the south of Aleutian Islands the main flow is from east to west and it wasnamed the returning flow (Kitano 1958), which approaching longitude 180° withhigh temperature and low salinity at the surface.
The 6.0°C-isotherm reachs to 51°N, l 78°W and at l 78°W horizontal inclinationof temperature increased to the west. Consequently, the extreme point of the
returning flow in June may be considered to locate in the vicinity of l 78°W longitude.
At l 70°W longitude the isotherm of 7.0°C penetrated from the north-east to
the southwest and at 167°W longitude isotherms (6.5° and 7.0°C) extended towards
the northeast. From these phenomena, each water masses in this area were conjectured to formed complicated movement which was formed between the returning
flow and the current with easterly component. The 6.5°C-isotherm locates in thenorth side of Unalaska Island, on the continental shelf to Alaska relativley hightemperature 7.0°C-isotherm is tongue-shaped, extending towards the south. Thisis the water mass which is heated on the shallow waters of Alaskan continental
shelf. At area from Cape Navarin to Cape Olyutorski isotherms run nearlyparallel to Siberian Continent and temperature within 20 sea miels off the coast
found less then 4.5°C.
July
The 8.5°C-isotherm covers most of the south waters of the Aleutian Islands. At
near 53°N, 163°W isotherms lie with a complicated situation like that of June.
The 8.0°C-isotherm lies at the north of the 8.5°C isotherm and it also lies along the
Aleutian Islands like the 8.5°C-isotherm. In the neighborhood of the Bowers
bank, there is a cold water area (below 8.0°C). This is a consequence of the upwelling which is formed by the bank, and it seems to him that the upwelling had
developed in July. North side of the eastern Aleutian Islands the 7.0°C isothermlies along the Islands and to the north of it the 7.0°C-isotherm extends towards thenorth-northwest mostly like the distribution of the 6.5°C-isotherm in June. The
the water mass which penetrated from the Alaskan sea area is higher about l.0°C
than that in June.
Off Cape Navarin the 5.0°C-isotherm lie nearly parallel to Siberian Continent. Near 57°N, l 78°E 10.0°, 9.5° and 9.0°C-isotherms run tongue-shaped.
AugustThe surface temperature attained the maximum value in the Bering sea and thenorthern part of the North Pacific. For instance, temperature at the east of
Paramushiru Island run about l.0°C-isotherm in May and the l l.0°C-isothermin August respectively. To the southeast of Cape Kronotski 13.0°, 12.0° andOCEANOGRAPHY AND WHALING GROUND IN THE SUBARCTIC

113

l l.0°C-isotherms extend towards the northeast and the l l.0°C isotherm approaches
to the south of Attu Island through the Komandorski Islands. North side of the
Aleutian Islands in the neighborhood of Attu Island the l0.0°C~isotherm runs fromthe northwest to the southwest. The temperature value was generally higher 10.0°C
off Kamchatka and 5.0-6.0°C at the adjacent waters of Attu Island than that of
May.

160"E

Fig. 4.

170"E

180'

11o·w

l60"W

!150'\\

Distribution of average sea surface temperature (°C) in July.

At the shallowest part of the Bowers bank 8.0° and 8.5°C-isotherms run parallel
to each other and from these temperature distribution, it is clear that the upwelling area exists. And the isolated cold water area also is found due to the upwelling by the ridge at the central part of the Aleutian Islands, near of longitude
180°. Off Navarin Cape surface temperature is about 2.0°C higher than that ofJune and 7.0°, 8.0° and 8.5°C-isotherms run, and the inner part of Anadry Bay
is supposed to have a cold water area formed by melted-ice.
In the neighborhood of St. Lawrence Island the 8.0°C-siotherm lies and off
Cape Chaplina the 4.0°C-isotherm is found. In addition, temperature within
3.0°C were observed in August of 1958 (Nasu 1960).
Temperature distributions in the Chukchi Sea are summarized as follows.
Temperature at surface in the Chukchi Sea ranged from 3. 7°C minimum tol l.2°C maximum (in August).
In general, in the eastern area of Chukchi Sea, the surface sea condition
tends to higher temperature and the isotherms run parallel with the Alaskancoast line. In addition the distribution of temperature at surface is chatacterized by a decrease from the east to west.

K. NASU

114

SeptemberIn the Subarctic Pacific temperatures are decreasing. Near 45°N, 155°E there
is tongue-shaped area with the l l.0°C-isotherm extending easterly and the 10.0°Cisotherm extending almost to Attu Island. Surface temperature in the sea areafrom 45°N, 155°E to Attu Island is higher at the west side and lower at the east
side.
HiO'\\'

so·
11.0

t6o·w

170'\\"

Fig. 5.

I.

,.
'

ISO'\\'

Distribution of average sea surface temperature (°C) in August.

·'1~~--,i160~'Ec--L--~~~---..!clio~l,--'-'~~~-'--,!,,180~.~~~~~±170~."~~~~~lh60'~"~~~~LJ150'~

Fig. 6.

Distribution of sea surface temperature (°C) in September.

115

OCEANOGRAPHY AND WHALING GROUND IN THE SUBARCTIC

Vertical distribution
Figs. 8-14 show the vertical distribution of temperature along the C,D,E,
F,G,H and I (see Fig. 7).

'

2726

.0"'-';\,,

"
....

G '

\.
·is

0-29
~

0-30

55'

Fig. 7. Station positions obtained by Konan·maru no. 5 in the summer of 1955.
(0-28-> 0-32: Data by Oshoro-maru)

C-lineFig. 8 is the southeastward section of the Komandor Is. The cold water area
found between Station 44 and 45. The thermocline lies in the upper 50 m indepth and its L!B/LlD is about 0.5° C/50 m. The intermediate cold water lies below
the 100 m and its core temperature shows below l.5°C. Besides, the discontinious
zone was formed at the intermediate cold water layer.
D-lineFig. 9 shows the vertical section of D-line. Near 54°-30'N, 168°-30'W, the author
shows the warm water mass which existed at 50 m with a 30 m layer and wascharacterized by more than 7.0°C (the maximum temperature was 9.3°C at 25 m
at Station 51). In the upper layer of the warm water mass, there is cold water
which is characterized by less than 7.0°C and the reverasl layer was formed.
Moreover, the warm water mass appeared near 55°-lO'N.
At 55°-lO'N, 169°-00'W, the author recognized the remarkable upwelling
and at the upper layer of upwelling, there was the warm water mass, where wereformed the thermocline. It seems to him that there were not intermediate cold
water.
E-lineFig. 10 shows the vertical profile of temperature along the E-line.

The warm

116

K. NASU
St •.

45

44

0

46

10.0
9.5
9.0
8.0
7 .0
6.0
5.0
4.0

50

3.0
2.5
2.0

I
~

"J

100

0

150
2.0
2.5
3.0

200
3.3

Fig. 8.

Vertical Profile of temperature ( 0 C) along the C-line.
61

s t,

54

52

55

51

I

7 .0
7 .0

50

5

100

5.0

-"

fr

Cl

4 .6

150

4 .0
200
3.8

Fig. 9.

3 .6

Vertical profile of temperature ( 0 C) along the D-line.

water mass which was characterized by moret han 7.0°C existed northwards at
a shallow layer less than 50 mat St. 66, near 54°-20'N, 169°-30'W. At the warm
water mass (about 25 m in depth), the inversion layer was formed and its tern-

OCEANOGRAPHY AND WHALING GROUND IN THE SUBARCTIC

117

perature was 7.6°C (the surface water was 7.0°C). The water mass seems to besame one which was found in vertical section slang the D-line. At 54°-30'N,
166°W the temperature distribution at less than 30m suggest the warm
s t,

60

52

62

64

I

I

I

I

7.0
7 .o
6.0
50

5.0
4.8

:§:

4.2
4.0

100

i

3.8

Cl

150

200

3 .5

Fig. 10. Vertical profile of temperature ( 0 C) along the E-line.
25

21

St.

7.5

20

rn

'

'
7 .5

50

\'"

4.0

:§:
1100

8

150
200

2 .0

7 .0
6.0
5.0
3.0

3.0

Fig. 11. Vertical profile of temperature (°C) along the G-line.

water mass which was characterized by more than 7.0°C and has a westward
tendency. The spreading of the isotherms is probably and indication of Bristol
waters. Moreover, at 167°-l68°W the stratum less than 30 m the boundary
was formed between the Bering Sea water (towards the east) and the Bristol Bay
water (towards the west). At 54°-30'N, 169°-30'W, there is intermediate cold
water, which has 3.0°C at the core, and it is clear that the small scale thermocline
is formed near the upper layer of the cold water mass (about 70 m in depth). Below
100 m, the isotherm of 3.5°C climbs steeply. Generally the horizontal distributionof temperature at the layer below 50 m depth, decreases towards the west andincreases towards the east.
G-lineFig. 11 shows the vertical section of temperature along the G-line which was
located from about 60 sea miles off Cape N avarin to the south-east. At 25 m

K. NASU

118

depth, the 5.0°C and 6.0°C lines showed similar depth in every station and it may
be considered that stable layer was formed at the surface.
At St. 21, the dichothermal water located near the 75 m depth (temperature
minimum shows 0.6°C) and the comparatively remarkable thermocline was formed
between the dichothermal water and upper layer of that. Below the dichothermal
water, the temperature varies little towards the deep and its difference was 0.5°C
from I 00 to 200 depth.
St. 19, 59°-20'N, 176°-l5'W, the dichothermal water lies at about 60 m
in depth and its core water temperature shows l.6°C, and the temperature below
75 m is mostly homogeneous. The 3.0°C line which extends from the 40 m depth
at St. 19 and was very similar in depth to St. 20. At St. 25, the water mass with
3.0°-4.0°C in temperature eixsts below 60m depth and the temperature was low
on the both sides of that water mass. From the vertical section, it is clear
considered that the vertical boundary was formed at St. 25.
St.

28

29

30

31

I

I

I

I

32
I

6.0

20

..s

i 40
0

60

80

Fig. 12.

Vertical profile of temperature (°C) along the I-line.

I-lineFig. 12 shows the vertical profile of temperature slong the I-line by use of dataobtained by Oshoro-maru. Each thermoclines rise at St. 0-28. East of St. 029 the comparatively cold water was characterized by less than 3.0°C in temperature below the 50 m depth and the cold water layer becomes deeper towards
the west. The comparative warm water was characterized by more than 6.0°C
in temperature located upper the 30 m in depth near St. 0-28 and the warm waterlayer becomes deeper towards the west, and at St. 0-28, the water masses are of two
types, east area of St. 0-28 is cold and west area is warm.

Thermocline
It is well known that in the northern part of North Pacific and Bering sea thethermocline in summer season has been formed by the heating of surface layer.
According to the observations at Ocean Weather Station (lat. 60°N, long. 145°W),

OCEANOGRAPHY AND WHALING GROUND IN THE SUBARCTIC

119

the thermocine develops between 10 and 50 m in April (Tully et al 1960).
In order to analyze of the thermocline conditions, Fig. 13 and 14 show thestation curves of temperature at each station in July and August. Then thethermocline located in almost all the northern part of the North Pacific Ocean,
Bering Sea and a part of Chukchi Sea, but their depth and temperature gradient(M/LlD: °C/m where (} is temperature and D is depth) differ with sea area. On
the thermocline, Tully (1957) has been discussed as follow. "Surface waters were
warmed by varnal heating and continues to increase through summer to midSeptember. "

1

I

170°E

I

'180·

'.I

170"\V'1~o·w·

Fig. 13. Station curves of temperature in July.
St. 1-12, 55, 56, 57: 1957
St. 209, 224, 236: 1959In July, the most remarkable thermocline exists about 20 sea miles south off
Cape Olyutorski, where the temperauter gradient is about-l.0°C and that layer isshallow depth. Such a remarkable thermoclines appeared from off Cape Olyutorski
to Kamchatka Peninsula, and the sharp variation layer of temperature were roughly
from surface to 25 m depth. The depth of thermocline have a tendency todownward in the south sea regions, i.e. to the east of south Kamchatka, near
51°-30'N, 162°-30'E the observed depth were 50-70m (see Fig. 14). From Komandorski Island to Attu I., there were also comparatively remarkable thermocline
which lied similar to that off south Kamchatka slighlty deeper than that of Cape

K.NASU120

Olyutorski.
Central part in the Bering Sea the thermocline near 59°N, l 75°W, especially
was conspicuous in August and its depth was shallow, from surface to 25 m depth andtemperature gradient was about-0.28°C. The temperature gradient observed on 29
and 30July were about -0.09°"'-0.l8°C and those depth were deep. From that
fact, it may be considered that the thermoclines in the central part of Bering Sea
develope conspicuously since the beginning of August. North-north-east of C.
Navarin, lat. 63°-20'N, long 180° the thermocline was not observed in July, andbelow 20 m depth, there is a thermocline which might cause a sinking due tomelting ice. To the east of C. Navarin, in July, the thermocline exists in the upper
20 m depth, below that was formed the homogeneous layer similar to the area
north-north-east of C. Navarin. From the data collected on 2 and 3 August
around St. Lawrence I. where the thermocline developes conspicuously similar to
160"E

170"£

iso·

11o·w

160"\V

1so·w

l60°E

170"£

180°

170

160°\\'

150°W'

Fig. 14. Station curves of temperature in August of 1955 (St. 58, 60, 63, 65, 68, 71,
84 and 88 were carried out in 1958)

that off Cape Olyutorski and depth of that is shallow (about 20 m). The
thermocline east of St. Lawrence was more developed than that of the west. (Itis assumed that the thermocline at the east of St. Lawrence Island has arleadyformed in July.) At the Chukchi Sea, north of the Bering Sea, the thermoclines
were found on the side of Alaskan waters, but were not found on the side of Siberianwaters (Nasu 1960).

OCEANOGRAPHY AND WHALING GROUND IN THE SUBARCTIC

121

The data obtained by Oshoro-maru during July of 1955 (Motoda et al 1956),
the thermoclines in the Bristol Bay existed in the sea area west of 57°-16'N, 161°40'W where the eastern most station in the observed region, and those depth werefrom surface to 50 m at each station. The temperature gradient increases to the
Aleutian ls. To the north of Unalaska I. near 54°-05'N, 168°-lO'W the thermoclines were not found and it may be caused by the vertical movement which
took place due to physical action.
South of Unimak I. thermocline exists at the surface layer, and the temperature at the 10 m depth was perfectly homogeneous, which seems to represent upwelling by bottom topotraphy. At the southern side of Aleutian ls. the vertical temperature gradient at the west longitude area was larger than that found east of southern Kamchatka Peninsula.
160'h110·1,;

180'

110·\1160"\\"

150·1\

~08

.,.

5'

'

'

O'

'

45

'

160'E

Fig. 15.

170"E

180'

17(J"\\"

160'\\"

150'\\"

Isotherm on the temperature minimum surface in summer of 1955, 1957 and 1958.

Intermediate cold water.
It is wellknown that m the Subarctic region a temperature minimum wasobserved at some depth in the summer. The structure which is associated withthe temperature mininmum is termed dichothermal structure (Uda 1935, 1955,
1956).
As Hirano (1961) also stated, the intermediate cold water is one of the characteristics of the Subarctic Pacific.
Fig. 15 shows the isotherm on the temperature minimum surface in summerof 1955, 1957 and 1958. The minimum temperature was -l.5°C and occurred eastof Paramushiru I. near 50°N, 159°E. The intermediate cold water extents to the
Kuril Is. and exists in about 150 m in depth. The maximum value of the minimun
temperature is 5.0°C isotherm and exists near 53°N, 165°W about 40 sea miles

K. NASU

122

south of the Unimak Pass. Judging from the map of Bennett (1959) and Uda(1960), the 5.0°C-isotherm may extend south of Kodiak I. And in this region
the depth of the minimum temperature existed at 60 m and increased from thisarea towards the south. Near 53°N, 161°W the minimum temperature covereda wide area at 75 m depth. The 3.5°C-isotherm occurred in a tongue near the
Pribirof Islands north of Unalaska, and to the west of this area there were 3.2°
and 3.0°C isotherm. The 3.2°C isotherm is notably meandered as far as 53°N,
171°W and the 3.0°C isotherm extents from 53°N, l 72°W to south of Attu Island
52°N, l 72°E.
150'\\

{:ft
..
,

I60'E

Fig. 16.

170"E170"\\'

180'

160'W

Depth of temperature minimum (meters) in Summer (1955, 57, 58, 59)

The depth of minimum temperature north of Unalaska I. the 100 and 125 mline lie mostly similar to the contour line of 200 m and extent from near 61°N,
180° longitude to near 55°N, l 70°E. In the northern-side of the Aleutian Is. theintermediate cold water increased in temperautre and decreased in depth towards
Bristol Bay. East of Cape Navarin, there was a minimum temperature which wascharacterized by comparative low -0.8°C at 73 m in depth. At the south of Cape
Olyutorski, intermediate cold water exists at 150 m in depth and has 0.0°C in
temperature. At very small area, the distribution of minimum temperature waters
differed with the east and west of Cape Olyutorski. That is:0

At the east
At the west

Temp. ( c)1.5
1.9

Depth (m)5080Near Cape Govena, the intermediate cold water existed, and was 0.7°C in
temperature and 25 m in depth.

OCEAt~OGRAPHY

AND WHALING GROUND IN THE SUBARCTIC123

At the north of the Komandorski Is. the cold water area (less than 1.0°0 in
temperature) was found and was 0.0°C at its minimum temperature at the area
close to the island. South of the Komandorski Is. the 1.8°0 isotherm lies at thelayer more than 100 m in depth. To the north of the Bering Sea, the minimum
temperature around St. Lawrence I. in general, existed near the sea bottom.
Generally, the temperature minimum of intermediate cold water in thenorthern part of the North Pacific and the Bering Sea in summer vary from -l.6°C
at its minimum to the highest value 5.6°0, and its core extents from l 75m to 25m
in depth.
There is an indication that the depth at the core of intermediate cold water
is deep at the cold area and shallow at the warm area.
SALINITY STRUCTIRE

As the data of salinity are very few compared with that of temperature, it is
not suitable for analysis concerning monthly mean. Consequently, in this paper
the distribution by year's were shown. Moreover, the general distribution of ice
in Febraury and April shown in Fig. 17 cited from the pilot chart which was published by U.S. Navy Hydrographic office.
HllY

170'E

160"E

,>,."

'

170'\\"~ j,

L----=160':_!·_ _ _ __,_,11,,_,o->:,_:--~~-~-----~-"'18-0e_''=_'=_'=_~~':'.::_':'.::_':'.::_'=_j,110::_·"----~-----~---~16"'-0'l;;_I- - - - - - - 'Fig. 17.

Distribution of ice area, Solid line: April, Chain line : February

Horizontal distribution
June
Fig. 18 shows the horizontal distribution of salinity at the surface to the east of
l 70°W, the southern side of the Aleutian Is. At the north of Unalaska, 33.00,
32.80 and 32.50°/ 00 located roughly parallel to one another and the 200 m contour
line and those values decrease towards Bristol Bay. As shown by Fig. 17, it isK. NASU

124

clearly due to melted-ice. From the surface, the waters to Bristol Bay is characterized by high salinity and low temperature.
The surface distribution of salinity south of the Aleutian Is. was drawn by
use of data in 1958. At latitude 52°N south of Unalaska I. the 32.65% 0 isohaline
existed to the east and west, and the low salinity area located north of the isohaline.
South of 32.60% 0 isohaline 32. 70, 32. 75, 32.80 and 32.85% 0 isohalines locatefrom southwest to northeast, and it is supposed that the water mass which ischaracterized by high salinity extends from southwest to north with anticyclonic
pattern.
170°11'165°

32. 75

N
50°

N

50°

N
47°

N

47°

170 °\\"

165'

Fig. 18. Honzontal distribution of salinity at thesurface in June of 1958.

July
Fig. 19 shows the horizontal distribution at the surface in July of 1957. The variation of salinity near 32.80% 0 is scarecely changed, and 33.00% 0 moved about
40 sea miles westward compared with that of June. It may be considered as due
to influence of lateral mixing by advection of melted-ice in and near Bristol Bay.
The distribution of salinity at the west longitude area south of the Aleutian Is.
war drawn by use of data in 1958. At 50°N, l 70°W, 32. 70% 0 isohaline in theform of tongue extends toward the southeast, and 32. 70°/ 00 isohaline runs in generalfrom east ot west within the range from l 77°W to 169°W. At the north of
32. 70°/ 00 isohaline, there was 32.65%0 isohaline which seems to be extended towards
the east.

OCEANOGRAPHY AND WHALING GROUND IN THE SUBARCTIC

125

At the sea region to the east of Cape Navarin there was distinguished low
temperature and salinity water mass which is characterized by less than 4.0°C in
temperature and 24.60°/ 00 in salinity. In addition, at this sea region melting packice was observed in June of 1957 (information from Mr. Ichihara), therfore, it
may be considered that the low temperature and the salinity water mass which
was already mentioned was formed m the immediate melted pack-ice.
175'

170'

!65'W

/I/

32 .8555•

55•.32.70

N
50°

N
50°

175.

Fig. 19.

170'

1165 "\\'

Horizontal distribution of salinity at the surface in July of 1958.

To the East of Kamchatka, at the sea region between the Komandorski Island and Attu Island 32.900fo 0 isohaline located from south to north, and thesalinity was low at the east and high at the west of the isohaline. Moreover,during the summer west of Kronotski low salinity water mass extended to the east
(Kitano 1958).
AugustAs shown in Fig. 20, near Cape Navarin, 31,500fo 0 line was found parallel 30-50
sea miles off the coast of Siberian Continent, 32.500fo 0 line extends further northeast through the vicinity of 60°N, 168°E and locates south of Cape Navarin.
The warm area which is characterized by more than 10.0°C was similar to
the area of 32.500fo 0 •The location of the 33.500fo 0 isohaline was also found near 61°-62°N l 79°30'W. However, compared to the western area of this region (vicinity of 60°N,
168°E) it is noted that relatively cold water (less than 10.9°C) extends. ConseK. NASU

126

quentry, it can be concluded that the cold and fresh water mass exists from Cape
Navarin to the east. While the warm and high salinity water mass exists from
Cape Navarin to the west.
In addition, in July of 1957 the high salinity water mass at the surface had
closed with the land compared to that of August, it may indicate that the oceanic
water mass had grown from July to August. The surface salinity in the Chuckih
Sea in August of 1958 varies from 27.00°!oo to 32.500fo 0 • The high salinity region
existed in the central part of the Chukchi Sea east and west of this region the low
salinity region existed (Nasu 1960).

60'
N

175'E

Fig. 20.

180 °

175 °

170°11'

Horizontal distribution of salinity at the surface in August of 1958.

The data of 1955, the separated salinity area (33.300fo 0 located near 52°N,
170°-30'W, and it shows 33.420/oo at the maximum. The surface temperature
was less than 7.0°C and there was the separated cold and high salinity area, which
is clearly formed by the influence of sea bottom topography.
Vertical distribution

C-lineFig. 21 shows the vertical profile of salinity along the C-line. Below the surface
salinity was high at St. 45 and low at St. 46 respectively. This tendency wasprominent in layer less than 30 m in depth.

OCEANOGRAPHY AND WHALING GROUND IN THE SUBARCTIC

127

That is, the (isohalin) distribution decreases towards St. 46 and from thevertical (isohaline) distribution shown in Fig. 22 the pattern of distribution evidently varied with stations (St. 45 and 46) at layers more than 50 m in depth.
In this region, the distribution of temperature also was divided into two types
the 9.0°C and l 1.0°C line, and the difference of temperature was clearly foundbelow 50m in depth (Fig 23).
St.
0

44

45

46
33 25
33.30

50
~

5

-=

100
33.40
33.50

n.
~
0

150

33.60
33. 7033.80
33. 90200

Fig. 21.

Vertical profile of salinity along C-line.

34 .00

(%)
0

2.0

4.0

6.0

10.0 l'C)o,---.--~--r-.---~--,-----,---r---,,-----.---:;"""

50 -

St.45

100

St.46

t-

100

Cl

150

150

200~----------'-----'

Fig. 22.

Station curves of salinity.

200~--~---------~

Fig. 23.

Station curves of temperature.

Consequently, at the southeast of Medni I, it may be concluded that thenotable structure of discontinuity was formed below the 30 m depth between thesouthern warm saline and the northern cold, low-salinity water mass.
At St: 46 the layer which was characterized by 33.700fo 0 existed at 50-100 m
in depth and at St. 45 there was low salinity layer at about 140 m in depth.
D-lineFig. 24 shows the vertical section of salinity along the C-line. At St. 54 the isohalines rise suddenly towards the surface similar to the isotherms. St. 45 is located128

K. NASU

at just the edge of 200 m contour line and the bottom topography from this station
to the west became abruptly deeper. Accordingly, the sudden rise of these isolines
are probably caused by the influence of some irregularity of the bottom topography. At the surface layer, the low salinity area (33.00°lo 0 ) was found to the south

50 ...

I

JOO

..c
0.

"

0

150

200

Fig. 24.

Vertical section of salinity along the D-line.

St.

25

0

20

32.00
50

32.60

I 100
32.80
-"
g.
0

150
200

33.20

Fig. 25.

Vertical section of salinity along the G-line.

of latitude 55°N where the temperature was more than 6.0°C. To the north of St.
54 the water mass is more than 6.8°C and less than 33.00°/ 00 extended. Below 50 m
the structure of discontinuity was formed on both the northern and the southernside of the cold, saline water mass which rose from a deeper layer. The warm
low-salinity water which was locates less than 50 m depth may be transported from
Bristol Bay.
G-lineThe vertical section of salinity along the G-line shown in Fig. 25. 32.800fo 0 line
was found as far as of St. 20 with the salinity being high in the southeasternside and low on the northwestern side of this line. Consequently, it was evident
that in the layer above 25 m depth the warm, saline water mass existed to thesoutheast, and the cold, low salinity water mass existed to the northwest of St. 20.
At St. 25, a local high salinity area which was characterized by more than 33.400fo 0

OCEANOGRAPHY AND WHALING GROUND IN THE SUBARCTIC

129

existed to about 150 m in depth with 3.3°C temperature, indicating dichothermal
water. Morever, as already stated, the vertical section of the temperature along
the G-line showed that the cold water mass existed both southeast and northwestof St. 25 warm area. Accordingly, below 50m depth it is evident that the cold
saline water mass was formed to the north and south, respectively.
I-lineFig. 26 shows the vertical section of salinity along the I-line. The low salinity
water mass (32.00% 0 ) extends from near 20 m in depth at St. 31 to the east in
the form of sinking. From the distribution of temperature it may be assumed thatthe deep water had risen near St. 28 and 29. In the surface layer of St. 28 theres~r-_o-,2_sr--o-,2_9~~0~--30~--~o~-~31~~0~-~32=--~

;:·~
80

I

\

32 .SO

32.00

I

\
32 40

100

Fig. 26.

Vertical section of salinity along the I-line.

is a zone of high salinity (32.40°1o 0 ) which coincided with the warm water (6.0°C<).
Generally, at St. 28 the water masses can be devided into two types.
Low temerature, low salinity water mass: Easter of St 28.
High temperature, saline water mass: Wester of st. 28.
THE ANALYSIS OF WATER MASS
The analysis of water mass was made by using temperature and salinity diagrams.
J-lineFig. 27 and 28 show a vertical section of temperature and salinity along the J-line.
A relatively warm water mass was rising near the island to the north. Thisphenomena was conspicuous, and this water mass, which is characterized by morethan 5.0°C in temperature, was found uniformly. At St. 11 the cold water ofthe deep layer was found as shallow as 100 m depth. High salinity water was also
found above the deep layer. From the distribution of temperature and salinity,
it can be assumed that the water mass which flows from the Aleutian Islands tothe north was isolated by the rising of deep water at St. 11.
Fig 29 shows the temperature-salinity relation near J-line. Surface water which
was characterized by more than 5.0°C in temperature and salinity of less than
32.660fo 0 was found at St. 10 and 12, and was clearly divided from the relatively
high temperature saline water mass of more than 5.0°C and 32.80°/ 00 found St. 11.

K. NASU

130

To the Aleutian Islands at St. 13 and 14 water mass which was characterized
by about 6.0°C and 32.50°/ 00 located, and seems similar character for that of St.
10 and 12. Dichothermal water of minimum temperature was found at St. 11,
15 and 16, at about 150m in depth. Dichothermal water was not found at St.
10, 13 and 14, near the Aleutian Islands.
St.

12

II

13

10

0

~6.4

6.2

-... 6.0

50

5.0
~

100

4.8

g
150

4 .6
3.5;
4.4

200

4 .2
3.0
3 .6

Fig. 27.
St.
0

4.0

3 .8

Vertical section temperature along the J-line.
11

12

10

13

50

a 100
~

""~

"" 150200

Fig. 28.

I

33.40

33.20

33.00

Vertical section of salinity along theJ-line.

Near the layer of 200 m depth, the water masses characterizing St. 13 and
14 were found to be quite similar At St. 11 there was a relatively high-salinity watermass which may have been mixed with the deeper water mass by upwelling.
Consequently, the water masses at near 200 m depth are divided into two types.
Those are water mass alongs the Aleutian Islands (St. 13 and 14) and the mixing
zone (St. 10). The water mass near St. 15 also seems to be a mixing zone and wascharacterized by the low-salinity (33.00°!o 0 ). It may be due to the advection of
the waters of Bristol Bay. The water masses near the J-line can be divided asfollows:

OCEANOGRAPHY AND WHALING GROUND IN THE SUBARCTIC

131

15
(°C)

8.0
16
7 .0

6.0

5.0

4.0

12
3.0

2

-°'-~-::--'-~~~-~~'--'----'-----'--'---'-'

--.I

32.50

33.00

33.50 (% 0 )Fig. 29. Temperature and salinity at St. 10, 11, 12,
13, 14, 15, 16 and 17.
170°

15s·w

N

N
05°

55•

Fig. 30.

Water types in the north area of Unalaska 1.

That is,B'-typeC-typeU-typeMixing typeC-lineFig. 31 shows the T-S characteristics of the water masses along the C-line. These
are separated by three zones; an upper zone of warm, low-salinity water (above
25 m in depth): a intermediate cold zone characterized by a temperature minimum(near 100 m in depth): and a lower zone in which the temperature and salinity

K. NASU

132

are both high. From the vertical section shown in Fig 8, the rising phenomenonof deep water was found at St. 45 and was more apparent from Fig. 21. It istheorized that the deep water was raised by the ridge located between' St. 45 and
46. By analysis of the T-S diagram shown in Fig. 31, there were uniformly surface
(o·c)

(0-C)

10.0

10.0

8.0

8.0

6.0

6.0

,,

4.0

2.0

2.0

"

"

00
33.00

33.50

34.00

0.0

(%0)

33.00

33.50

34.00

Fig. 31 Temperature and salinity at St. 10, 11, 12, 13, 14, 15, 16 and 17.
160'E

170'

160°\\'

y
~

,;,

••

~·'

·~

60

··.•."'\""

0......
50

50'

x

160'E

~

180°

170'E

Fig. 32.

Distribution of water mass.

170'\V160'W

OCEANOGRAPHY AND WHALING GROUND IN THE SUBARCTIC

133

waters in salinity about 33.30-33.40% 0). To the west of Attu Island, near 53°N,
170°E, low salinity water was, of which the salinity was lower than that of thewater mass along the C-line. Near 50 m of St. 45 high salinity water mass(>33.600fo 0 ) was found, and suggested the rising of deep water. At St. 42 thetemperature from surface to 50 m varied remarkable, however the salinity washomogeneous. This water mass may be conisdered that of coastel water off Kamchatka, in which the intermeidate cold water exists at relatively shallow depth.
Near 100 m the water mass which is characterized by less than l.5°C and 33.5033.60°1o0 located at St. 42, 43 and 44 respectively, and water masses at St. 40 and
47 were relatively warm and low salinity. At St. 46 there are cold and low

('C)
8.0

19
22

21

6.0

4.0

2.0

o.o

31.00

32 .0033 .00%r.i

Fig. 33. T-S characteristics of the water masses at vicinityof the G-line.

salinity waters (temperature: about l.2°C, salinity: about 33.400fo 0). Near 200 m
depth, both temperature and salinity were higher than those at 100-150 m depth
at each station. Analyzed water masses are termed A, A', B and K for convenience, and the distribution of those is shown in Fig. 32. The summary for water
masses are as follows.
A: Intermediate cold water developed, with the core at about 100 m, withwarm and high salinity water near 200 m.
A': As stated by Kitano ( 1958), A' is a subtype of A, and is generally warmer
and more saline than A below 50 m depth.
B: From surface to near 100 m depth, temperature varied anomalously withdepth. Salinity was homogeneous, and the temperature minimum was foundnear 100 m. According to Kitano ( 1958), the B-type extended to the central
area of the Bering Sea.
K: The core of intermediate cold water is located in shallow layer, with atemperature of less than l ,0°C.

K. NASU

134

G-lineFig. 33 shows the T-S characteristics of the water masses at the v1cm1ty of
the G-line. In general, from 10 to 75 m depth at St. 22, near Cape Navarin, there
is a prevalent cold water ( <-l.0°C) which is apparently established by verticalconvection during the period of cooling. At 100 m depth there is a low salinity
water mass (30.99°/ 00 ) which is quite different from that observed at 75 m depth.
At surface layer of St. 19, 20. 21 and 25 warm and high salinity water masses arefound which may be divided with the water mass near St. 22. At the 25 m layerof St. 21 there is a relatively cold and low salinity water mass which must be influenced by the Siberian coastal area water mass. At St. 25 in general it wasevident that the warm and high salinity water mass had intruded. At St. 19,
generally, salinities are low at each depth layer, it was probably established by
the convection between the low salinity of Alaskan coastal area and other. From
Fig. 32, near Cape N avarim cold and low salinity water mass located in the vicinityof Siberian Continent where in the south, there was a warm and high salinity area
near 60°-30'N, 180° longitude where salinity in the east decreased again. Consequently, water masses near Cape Navarin may be divided into three types. General
distribution of water masses in the Subarctic region was shown in Fig. 32 which
included Kitano's figure (1958), too. The water masses near Cape Olyutorski,
St. Lawrence Island and the Chukchi Sea were examined by use of data obtained
at sea surface.
HYDROGEN-ION CONCENTRATION (PH)The hydrogen-ion concentration was determined by a comparator for sea water
which consists of two series of color standard solutions, one was Cresol Red and53°

0 /////,;::: ----8.10 53'
8 15

//I

52'

II!/

'/

~
/

2'
5

8.05
N

51°

160'E

8.00~,///'-----)
165 °

N
51°

8.05

170 °

Fig. 34 a).

the other was Tymol Blue. The horizontal distributions of pH at the surface
are shown in Fig 34 a) b) c) d). The pH values varied from 8.25 maximum to7.95 minimum at the south of the Komandorski Is. and the adjacent waters of the
Aleutian Is. The waters of high concentration of pH at the surface located in
the northern area of Unalaska I., where the value was 8.15, and increased toward

OCEANOGRAPHY AND WHALING GROUND IN THE SUBARCTIC

135

Bristol Bay (8.20-8.25). The pH value in Bristol Bay was 8.4 to 8.5 according
to data obtained by Oshoro-maru. In July of 1959, the eastern-most part of the
8.20 line was located more westerly than in 1958 and it may be deduced that theBristol water mass is to characterized by a pH of less than 8.25 extended towards
the west. Moreover, it may be assumed that the annual variation on the distribttion of pH is quite large. It may be influenced by the expansion and decay between the Bristol Bay and Bering Sea water mass.
175.

170"\V,::~~'"
j'
~
50"

8.00

50·

~

June'58
175.

170'\\'

Fig. 34 b).

55•

July' 58

/ / / 8.15N
• 50'
165°1\'

Fig. 34 c).

TRANSPARENCY

Fig. 35 a) b) show the isoline of transparency which were obtained by Secchi disc.
In June 1958, near 50°-30'N, l 72°-30'W where the transparency generally washigh compared with that of the surrounding area and those value varied 7 to 18 m.
The transparency was observed to vary between stations. That is, near 50°N,
l 78°W and 51°N, l 72°W, high value area extended towards the north. This may

136

K. NASUbe a significant factor in causing the branch of extension of the Kuroshio watermass. Near 50°N, 170°W, to the south there was an isoline of 7 m. From the
distribution of transparency it is assumed that a dis continuous zone may beformed near 168°W to 172°W. The transparency at the northern side of Unalaska~..---.---,--l.,...75_"E--,--,-~~-18~0_'~--.-~-17_5'~~--..--~17_0'-~~--l__,65 'II'

55'

55°

8. 10)__..,/

N.July21-.Ju,ly29

50'

N

50'

175 'E

Fig. 34 a)-d).

180'

175'

170'

165 'IV

Fig. 34 d).
Horizontal distribution of pH at the surface.
170'W

55•

55'

N
54•

170 'IV

Fig. 35 a).

I., from 6 to 16 m, decreased towards the north, near 200 m contour line. The
highest area which was characterized by more than 16 m, coincide with the Cwater mass area (see Fig. 32), and it is probably due to the intrusion which flowedfrom the western area. In addition, the transparency near Unalaska I. was lessthan 10 m.

OCEANOGRAPHY AND WHALING GROUND IN THE SUBARCTIC

175°1\'

170'

137

165"W

Q

June' 58

N

so'

10
170.

175°1\'

16S.

Fig. 35 b).
Fig. 35 a)-b).

Transparency in summer (reading-meters).

DISSOLVED OXYGEN

Horizontal distribution
In general, from the data obtained by our observations the dissolved oxygen at thesurface in the Bering Sea ranged from 4.43 to 11.05 CC/L and it decreased alongl »(ii:,/.- /

170"

29 ,June-16 ,July

~

oD

'h

--2_ __ .../o\;zif>_~>:dL:::=Z---~-"'--~ .. :..-----OC/-----~/-·\17 -~--~-·12....:..---

7.20

Jv,0

,.w
'---./( JI ) )

N

so·

165"W

)

1.00

N

so·

22 July-29 July

.

7.10

175"

170"

165"\V

Fig. 36. Horizontal distribution of dissolved oxygen at the surface
in June and July of 1959.

the Aleution Is. (the dissolved oxygen was decreased near Bowers Bank also) andincreased towards the east region of Kamchatka Peninsula and Bristol Bay (Nasu138

K. NASU1957).

In the Chukchi Sea, the dissolved oxygen varied from 9.03 to 7.17 CC/L
in August of 1958, and generally was less along the Alaskan coast and the higher
along the Siberian coast (Nasu 1960). Fig. 36 shows the distribution of dissolved
oxygen at the surface. To the northern side of Unalaska I. the 8.0 CC/L line istongue-shaped and intrudes from Bristol Bay to the southwest. As already mentioned above, the dissolved oxygen is higher in the water mass of Bristol Bay andis lower along Unalaska I. where there is sea area, which is covered by less than
8.0 CC/L. Morever, at 49°-50'N, l 70°-l 76°W there is the isolated region where
the dissolved oxygen was greater than 9.00 CC/L. It may be considered due to the
influence of some biological elements. To the south of the Aleutian Is. near 49°510N, 170°-176°W, the dissolved oxygen ranged from about 7.00 to 8.00 CC/L
and generally is lower compared to that in the northern side of Unalaska I. 7.00
and 7.10 CC/L line extend from the south to the northward. On the other hand,
7.20 CC/L line locates from the north to the southward and is mostly tongue-shaped
at 50°N, l 72°-30'W. From the data of sea temperature, salinity and transparency,
at 50°N, l 72°W the author can be assumed that the oceanic front is formed between
the cold and warm water mass.
Vertical distribution
C-lineFig. 37 shows the vertical profile of the dissolved oxygen along the C-line. In
general, as shown in the profiles of temperature and salinity, there is a boundary
at St. 45. That is, the dissolved oxygen is higher at the northern side (B-watermass) and is lower at the southern side of the boundary (A-water mass), and the
St.

44

45

46

o..--~~~~~~~~~~

7.3~ 7.15

v 7.2fJ ~'""'
Cj

50
7.2

I 100

(<9.0

7.0/~~l~OO(
5.0

150

(9.u

4.0

7 .5
7 .2
7 .0
5.0

200

4.0

Fig. 37. Vertical profile of dissolved
oxygen along the C-line.

OCEANOGRAPHY AND WHALING GROUND IN THE SUBARCTIC

139

isoline of it abruptly changes. The rising of low dissolved oxygen at St. 45 may
be caused by upwelling formed by the ridge extending from the Komandorski Is.
to the southeast. At St. 46, from the surface to near 100 m depth, there is highdissolved oxygen layer in which the value was over 9.0 CC/L (the value at 150 m
depth was about 7.0 CC/L). It may be assumed that the marine productivity ishigh in the B-water mass of Bering Sea water. Above 100 m depth at St. 44 and45 there is a water mass which is characterized by having water of about 7.5 to
6.0 CC/L. dissolved oxygen. From each station curves of the dissolved oxygenvertical change developes abruptly below 100 m depth, at St. 44 and 46, and aresmall at St. 45.
D-lineThe vertical profile of the dissolved oxygen along the D-line is shown in Fig.
38. Below 50 m depth between St. 65 and 61 there is a transition layer whichcharacterized by a abruptly change of the dissolved oxygen. The isolines of the

&-

/"6,9
I

I

JOO

\

Cl

,_,

I

~

6.0

150

\---1
,

200 .____,,,~-----~

Fig. 38. Vertical profile of the dissolved
oxygen along the D-line.

low dissolved oxygen rise from south to north. The phenomenon may be consideredthat the upwelling is fromed by the marine topography in which the contour line
is steeply change from 200 m to downward. The existence of upwelling is also
apparent from the vertical distribution of the dissolved oxygen at St. 61 and 65.
To the very surface the intrusion of the high dissolved oxygen is found.

K. NASU

140

I-lineFig. 39 shows the vertical profile of dissolved oxygen along the I-line. The watermass is characterized by more than 11.00 CC/L below 20 m to the east of St. 0-29.
From the surface to 30 m between St. 0-28 and St. 0-29 11.00 CC/L, of which
st.
0

0 -28

0 -29

o-w

o-n
Ii. 0

o-n
---...:___ 11. 0-----------11.0

;o

5

""'@
0

10.0
40

601----------~-----------~

Fig. 39.

Vertical profile of dissolved oxygen along the I-line.

the distrubution at a relatively shallow layer coincides with the water mass of morethan 6.0°C in temperature and 32.400fo 0 in salinity. Such a distribution leads toa definition of two distinct water masses as a boundary to St. 0-28: the Alaskan
water mass of low temperature and salinity with high dissolved oxygen, and theBering Sea water mass (high temperature and salinity with dissolved oxygen).
ANNUAL VARIATION OF WHALE CATCH

Table 1 shows the number of whale caught by Japanese whaling expeditions in
the Bering Sea and the northern part of the North Pacific. The fin whale is themost important specie in the waters, as mentioned in Table 1. Fig. 40 shows thedaily catch of fin whale per a catcher boat. In the Fig. 40 we must be careful on
the catch of fin whale during the operation of blue whale, because the catch of
TABLE I. NUMBER OF WHALE CAUGHT BY JAPANESE WHALING EXPEDITIONSIN THE BERING SEA AND THE NORTHERN PART OF NORTH PACIFIC
Year.

Blue

Fin.

Hump.

Sei.

Total.

Sperm.

Right.

1940
41
52
53
54
55
56
57
58
59
60
61
62

34
40
55
90
145
70
70
70
70
70
70
70
48
902

295
370
213
470
1, 316
1, 360l, 415I, 405I, 331I, 450I, 393I, 452
1, 193
13,663

108
6
37
42
136
117
37
6
24
0
0
9
17
539

3
7
14
98
129
21
48
166
330
32
203
4
260
1, 315

440
423
319
700
1, 726
1, 568
1, 570I, 641
1, 755I, 552
1,666
1, 535
1, 51816, 413

182
162
0
0
490
1, 084
1, 5981, 7001, 5001, 8001, 8001, 6002,549
14, 4673
3
6

19May

1960

1952

25

1 June

10

20

Ill

Fig. 40.

1020

1 Aug.

15

Daily catch of fin whale per a catcher boat.
I : Off Kamchatka Peninsula.
II : Southern region of Aleutian Islands.
III: Off Unalaska Island.
IV : Off the west of St. Mathew Island.
V: Off Cape Navarin.

1 .July

1 Sep-------Sperm whaling

15

25

-....

~
......
0

~

c:::

ifl

trJ

~

z

~tl

0

~

Q

~

~

~

I

0

~

0

0

142

K. NASUfin whale decrease by the catch of blue whale. The daily variation of catch has
increased in recent years. However, the catch in 1959 and 1960 was relatively
stable. Such a problem must be examined from the point of oceanography,
meteorology, catch effort and other elements. From the catch tendency of eachyear, the fluctuation of daily catch off Kamchatka is relatively large, but that of1959 shows a small daily variation. The whaling location in this year was a little
different from that of other years. Whaling was carried out in the region northof the Komandorski Islands.
When compared to 1953 the catch off Kamchatka has a tendency to become
better in the first half and worse in the latter half of the season.
As already stated, the whaling ground on the southern side of the AleutianIslands (West longitude) shifted to the southward around on 50°N latitude from1957. In this ground, the operation in 1957 and 1958 were holding out a stable
catch, but the catch in 1959 and 1960 decreased. The operation carried out frommiddle to last decade of July in 195 7 and from middle to last decade of June 1958
and from July 1959 and 1960. Whaling operation at the west region of St. Mathew
Island carried out in 1957 and 1960. In 1957 and 1958 there were also whaling
ground off Cape Navarin, where many fin whales were captured and the detail ofwhaling season is obscurity as there is lack of data in June and July, but it should
be late (may be from last decade in July).
Operation in the northern ground of U nalaska Island commenced in 1954
and has carried out there ever since. The number of daily catch always stablecondition every year in this ground, but the total caught whale are relatively small
quantity in some years which is because of unnatural influence for the commercial
production. From the yearly operation itmay be considered that the whaling
season lasts from June into September. The variation of sperm whale caught did
not show in Figure. From yearly operation the whaling ground is formed aroundthe Aleutian Islands during the summer season, whose yearly fluctuation is verysmall, but 1960 many whales were captured at the vicinity of 57°N, l 75°W.
It is convenience to use the center of whaling ground for the analysis of fluctuation of that at sea region off Kamchatka Peninsula and the northern region of
Unalaska Island where the whaling operation are carried out at every year. A
primary factots what the whaling grounds are formed consist mainly of meterology,
submarine topography, oceanographic condition and others, in which the oceanographic condition is the most important factor. The oceanographic condition,
namely, the physical, chemical and biological element in each year do not shown
always stationary distribution.
CENTER OF WHALING GROUND
Off Kamchatka Peninsula

In order to obtain the center of whaling ground the author used following
formula which was shown by Uda (1930).

OCEANOGRAPHY AND WHALING GROUND IN THE SUBARCTIC

143

y = In~yinz, where x and y are location of caught whale.
X and Y are the center of whaling ground.

n is number of caught whale.

Fig. 41 shows the average center in the years 1952 to 1960 and the yearly centerof ground. Next, Fig. 42 shows the yearly caught whale number of latitude andlongitude respectivery at each grounds.
On the longitudinal variation, two peaks were found in 1952, 1953 and 1954,of which the operations were carried out during long time (the operation in 1956
and 1959 were carried mainly out at the northern region of the Komandorski
Islands). Those peaks are generally near 164°E and l 74°E, and the most peak
160 E
165'
170'
55• .---,-----v------,--,----,------,-,-~-,----r-----r----, 55•

'··~
, 59
54•

54•

, 60

, 57

53•

53•

, 58
52·

, 56

M

'52

52'

'54
'55
'53
N
N
51' ~-~-----~--~--'-----''----'----'-----'---' 51 •
160'E
165'
170'

Fig. 41. Yearly center of fin whaling ground.
® shows the average center in the years 1952 to 1960.

longitudinal catch was found near 164°E. The peak of latitudinal catch generally
as at 52° to 53°N, and has a tendency to more barely towards the north. Such in1956 and 1959 when the whaling ground was formed at the northern region of
Komandorski Islands coincide with relatively higher in sea temperature. The
problem of movement of ground must analyze from the point of migration ofwhales and whaling season.
The operation in this area is carried out in recently the beginning of allwhaling season in the Subarctic Pacific area. The peak of latitudinal catch
generally, is near 52°-30'N and average center of whaling ground in the years
1952 to 1960 locates near 52°N, 165°-30'E.
Off Unalaska island
As mentioned on the whaling operation in the region off Unalaska I. by Japanese144

K. NASU

1952

1953

1954

~l

1955

...
0

~

"'c"

1957

0

1
t

1958

(.)

1959

1960

158 160

162 164

166 168170

172 174(£) 48(Longitude)

50

52

54

56 (N){Latitude)

Fig. 42. Yearly caught number of fin whale in the
ground off Kamchatka.

170'

166'\\'.......... ..
'58
, 57

55•

M

, 56

'\ --.

...._

55e

'60
'55

N

N
54•

54•
'59

170'

i6S' 11·

Fig. 43. Yearly center of fin whaling grouud.
<Ml shows the average center in the years 1954
to 1960.

expeditions are began since 1954. From Fig. 43 the center of ground fluctuates
in a small range. The average center of ground in the years 1954 to 1960 locates
at 54°N 169°W and the peak of the latitudinal catch was found between 54°N

OCEANOGRAPHY AND WHALING GROUND IN THE SUBARCTIC

145

and 55°N latitude (see Fig. 44). On the longitudinal between 169°W and 171°W,
there are the center of catch.
In general, the whaling groun off U nalaska Island fluctuates in a smaller
compared with that off Kamchatka Peninsula.

1954

I
200

'""r
100

'"~

0

•.

1956

.c

r

~

c

"''O

.

1957

400

c

-"'
E

i'!

f.o

@

u

~

200
0

1958

~
1959

1960

112·

110·
168'
(Longitude)

166 ·w

53'

54•

55·

56'N

(Latitude)

Fig. 44. Yearly caught number of fin whale in the ground to
the north of Unalaska Island.

SPERM WHALING GROUND
Sperm whales are mainly captured along the Aleutian Islands 1960 was an
exception. Fig. 45 shows the latitudinally number caught in the ground along
the Aleutian Islands. The latitudinal range of ground covers from l 70°E to
160°W indicates that the annual fluctuations are very small. The number caught
at each latitude section varies somewhat each year, and in general, is more abundantin the region west of l 77°W and is most abundant in the vicinity of 180° longitude.

K. NASU

146

1955

200l
100
0

Longitude

Fig. 45. Latitudinal number of sperm whale in the ground along the
Aleutian Island. (except to the north of 55°N)

STRUCTURE OF WHALING GROUND

Fig. 46 shows the schematic hydrographic structure of the ground off northern
region of Unalaska Island along the D-line. In the Fig. 46 black circle shows thenumber of fin whale caught in 1955 season. The hydrographic structure in thisground has formed the discontinuous zone at subsurface between the water mass
which intrudes from the southern region of the Aleutian Islands and the Bering
Sea from the water mass, which there also is upwelling zone. The quantity of dissolved oxygen, is lower along the Aleutian Islands and almost shows super-saturation at the head of the water mass which is transported from the southern region.
Uda (1960) stated that

Q=J J J0 'dzdA (where A: area, Z: depth, Oz:
(A)

<Zl

2

quantity of dissolved oxygen at Z m. in depth, O'z: super-saturation quantity ofdissolved oxygen at Z m.) is directly proportional to the quantity of marine life,and Matsudaira et al ( 1956) reported that the marine production relationship isshown in following formula, based on the quantity of dissolved oxygen.

P = (Oz-O'z)
Where P is marine production,
0 and O' are similar to Uda's formula.
Consequentry, Oz-O'z may be considered for the indirect index of marine

OCEANOGRAPHY AND WHALING GROUND IN THE SUBARCTIC

147

production. The source of the oxygen supply is air, phytoplankton etc. The
oxygen which is supplied from air is transported to the deep layer by vertical turbulence of sea waters, etc, and is consumed there.
61

54

55

. .. .. ..
.. ...... ............ 11::Hi ..ii.. .. ... ::: ::52

51

St.No.

=-

50

.. ..
..:...... :: ....
:: ::

c

..-- ..... · i1·~··1··· . - -_~ ~.. ·1 I. I I r· - . _ - 11II1.. I I '1· 111 I I I 111 I
I
I·.
I
I
11 I I' .
. . . ,I 1I1 II 111 I 1I I I I I I'_: , ,
• I I, I" I . I ' I I I I I I I I 11 1 I I 11 I I I -;- : ...;_ ....
,
.111
I 1 1 I 111_,
111 11 I
r. ·1 ·'I II II I I II
I I I
I II II , .
I •1 I I I I I 11
I
1 I
I
I
1
1
I
I I I
· I
I
1 I
I I/
. I ·i ·I I 1 I I /I I I II I
I I I
1I · : I I I r I I I 11 I I 1 I I I
I I I I I I I1
I I 11 1 I
I I I I I I I 111 I I I /I I

Q
~

E
c

-"

100

g.

Cl

150

200

Fig. 46. Schematic hydrographic structure of the groundoff region of Unalaska Island.
Small black circle: catch no. of fin whale.
Oblique: super saturation of disolved oxygen.
Black : the most dence stratus of dissolved oxygen.
And other notations show water mass.

5.0
13.20

6.0
40

4.0

7.0

5.0

(cc/L)
80 (% )

60

6.0

CC)

26.50

26.10

100
<YI

200

Fig. 47. Vertical distribution of temperature, salinity, dissolved oxygen
and at at St. 54.

When the dissolved oxygen is supplied from air, the quantity is the maximum at sea surface. As shown in Fig. 47, at St. 54 the quantity of dissolved
oxygen is very large. Its saturation ratio is 122.40%, and mainly be produced

148

by photosynthesis.

K. NASUAt St. 54 the vertical stability (E = 10- 3 ~:t, where Eis ver-tical stability, at is density of sea water and Z is depth) is the most stablecondition between 25 and 50 m. in depth, where the typical thermocline is formed
also (see Fig. 47). This may be explained by an upwelling water mass during thewinter season supplying the surface layer, where it is well known that phytoplanktons
increase. Halse ( 1956) stated that in the Antarctic zone, with its pronounced
stability, the large phytoplankton population were confined to a surface layer of
25-50 m. According to Mackintosh & Wheeler (1929), Hardy & Gunther (1935),
Mizue (1951), Peters (1955), Marr (1956) and Nemoto (1957, 1959, 1962), it iswell known that the staple food of baleen whale in the Antarctic and North Pacific
Ocean is euphausiids, and Kemp et al ( 1932) stated that the distribution of blueand fin whales in the Antarctic waters is closely correlated with the euphausia
distribution. It is also reported that these euphausiids feed mainly on phytoplankton (Barkley 1940, Einarson 1945, Ponomareva 1959) and zooplankton organisms(Ponomareva 1959). But Hardy (1935) described that the zooplanktons are
distributed away from the concentration area of the phytoplanktons, in general,such an area is not always plenty area of zooplankton.
It also is known that the high concentration layer of the diatom exists lessthan about 50 meters of depth (Moberg 1928, Phifer 1934a, 1934b, Kokubo andTamura 1934. The high concentration layer of the phytoplankton seems to thefeeding depth of baleen whale. Consequentry, as stated by Marr (1956) and
Nemoto (1962), baleen whales seem to feed at relatively shallow depth, but the
problem on the feeding depth must be examined from the ecology of zooplanktons
and other marine life, also.
Southern region of the Aleutian Is. in West longitude
In this region mainly fin whales were captured but some blue and sei whales
were also captured. The whaling ground extends to east and west as a center tolat. 50°-51°N, and locates in the water mass of returnig flow (Kitano 1958).
From the distributions of surface temperature in June and July (some whales
were sighted in the season) the ground seems to be closely with the oceanic front
which is formed between the northerly branch of Kuroshio Extention and the
Aleutian Gyral. In order to analyze the structure of the whaling ground, theauther tried study of the upwelling and sinking, whose conputation was based on
the formula devised by Saito and Kanari (1961).
Fig. 48 shows the distribution of upwelling and sinking between 25 and 200
meters in depth along 50°N latitude. At l 77°W, sinking exists as deep as 200 m.
at least. In the area between 171°W and 176°W there is upwelling at relatively
shallow depth which seem to extend toward the west, according to Kitano ( 1958).
Between 174° and 176°W sinking is formed to depth of 100 to 200 m. Near 171°W
upwelling exists as deep as at least 200 m. At 170°W sinking generally is formed
as far as 200 m, condition being similar to those found at l 77°W. From these conditions fin whale generally were captured in the area where the upwelling exists

OCEANOGRAPHY AND WHALING GROUND IN THE SUBARCTIC

149

from relatively deep layer, being especially plentiful near the boundary zone which
exists between the sinking and upwelling areas. Vertical structure along 167°57'W is shown in Fig. 49, where the fin whale catch between 168° and 169°W, wastotaled. Thermocline exists between 20 and 40 m depth, with isopycnal rises
between 50° and 51°N.
(Langi tudc)

175"
69

27

18

170 'IV
43

11

89

123

148

0

-+50

-+-

100

-++-+-

~

150

+

200

+
+

+-

0
+-++-

+++-

-+-

-++++-

+-

+-

+

-+++-

-+-++-++0-+++-.Nos. show ti:e canght no. of fin whale-

upwelling-+ sinking
0 There is no upwelling and sinking

Fig. 48. Vertical distribution of upwelling and sinking along 50°N
Latitude.

so·

49•

48"
Catch nos,of fin whale

99

52·

53• N (Lat.)

118

20
40

:§:

60

i

80

0

I

11

Rich P20s

100
120
140

Fig. 49.

(\
Richer P20s

Aleutian Is.

Schematic structure in the fin whaling ground along 167°57'W.

The maximum layer of dissolved oxygen is found between 20 and 80 m,with thickness being larger where the quantity of phosphate is low at relatively
shallow depth, and especially is lower south of 48°-30'N and north of 51°-20'N.
The water mass which is characterized by having water of relatively highconcentration of phosphate rises north of 49°N, and zone of the highest concentration is found near 110 m depth at 51°N. Many fin whales were captured between
49° and 51°N, where an upwelling region exists in which the waters in the deep

K. NASU

150

layer have rich phosphate waters and the maximum layer of dissolved oxygen ismost thick.

Off Cape .NavarinThis whaling ground is located near the m1xmg zone formed between thewater mass along the Siberian continent, characterized by low temperature andsalinity, and the oceanic water mass of relatively high temperature and salinity.
Fig. 50 shows the schematic figure of water masses and the distribution of fin whale
caught (nos. is shown in the Fig. 50). In the Fig. 50 oceanographic data used isthat of middle July, and the whaling season is shown from the last of August.
170°E

175°

180°

175°W

65°
65°

64

3.8

32

53

21

4

8

15

N
61°

N
61°

170°E

175 °

180°

175'W

Fig. 50. Schematic picture of water masses and the distribution of fin
whale caught. Solid lines show the boundary of water mass.

Moreover, the vertical section of temperature along the N-line is shaown in Fig.
51. The water mass off Cape Navarin further can be definited to three zones(it was definited to two zones in the article of water mass analysis), as follows:
1. Pure melted-ice water: is characterized by marked cold (less than
2.2°C) and low salinity (less than 26.00° / 00 ).
2. Zone off Cape Navarin: is characterized by relatively warm (morethan 6.0°C) and high salinity (more than 30.000fo 0).

OCEANOGRAPHY AND WHALING GROUND IN THE SUBARCTIC

151

3.

Mixing zone: locates between the pure melted ice-water and watermass off Cape Navarin.
These water masses are termed conveinentry N, ON and M-type, respectively. From Fig. 51, it is seen that a typical discontinuous zone is formed between
N-type and M-type, and is considered the vertical boundary as Tsujita (1954)
described it in his treatise on the mackerel fishing grounds of Tsushima. Such avertical boundary can also be assume to form near pack-ice in the Antarctic.
30.000%0 (6.0"C (

26.00 %0)2 .2"C)B

A~1·:::'.\

'•

....,
. ...
.. . .
•

25

•.

I

.

..

.

2.0'C

.

.

ME>lted-ice water·

50

.....
.. . . .

...

. . . ... .

.
75 ,____ _ _ _ _ _ _ _ _ ___,

Fig. 51. Vertical section of temperature
along the N-line.

From the distribution of surface temperature as shown on current chart (U da1960, Fleming 1955), it is clear that the water mass of N-type is moving towards
the south along the Siberian continent and the ON-type is flowing towards thenorth. In addition, many fin whales were captured in the mixing zone (especiallynarrow area).
SUMMARY

1. In this paper the oceanography and whaling grounds are discussed basedon the data obtained by whaling factory and whale marking boats.
2. The monthly mean distributions of surface temperature during 1955-1959
were examined.
May: Temperature distribution to the east off Kamchatka Peninsula, ingeneral, may be considered as due to the influence of coastal and off shore
water mass.
On the both side of the Aleutian Islands, isotherms run towards the east andwest roughly parallel to each other.
June: Isotherms in the vicinity of the Aleutian Islands run similar to those. 152

K. NASUof May. On the continental shelf to Alaska relatively high temperature
7.0°C-isotherm is tongue-shaped, extending towards the south.
July: In the neighborhood of the Bowers bank there is a cold water area
which is characterized by below 8.0°C.
Temperature in the Alaskan Sea area is high about l.0°C than that in June.
In the vicinity of the Cape Navarin the 5.0°C and 6.0°C isotherms lie nearlyparallel to Siberian Continent.
August; The surface temperature in the northern part of the North Pacificand the Bering Sea attained the maximum value in August.
September; Temperatures in this season are decreasing.
3. Thermocline located in almost all the northern part of the North Pacific
Ocean, Bering Sea and a part of Chukchi Sea, but their depth and temperture
gradient (LlB/LlD) differ with sea area and season.
4. The temperature minimum of intermediate cold water in the Subarctic
Pacific region vary from -l.6°C at its minimum to highest value 5.6°C, and its
core extents from 175 m to 25 m in depth.
5. As the data of salinity was very few compared with that of temperature, it
is not examined concerning monthly mean. However, the distribution of somemonths by year's were shown and discussed.
6. The analysis of water mass was made by using temperature and salinity diagram.
a) Northern sea area of Unalaska Island can be divided into four water
masses as shown in Fig 30.
b) Water mass off Kamchatka Peninsula can be divided into four types.
That is,
A: Intermediate cold water developed, and saline water near 200m.
A': Subtype of A.
B: From surface to 100 m in depth, temperature varied anomalouslywith depth. Salinity was homogeneous.
K: Intermediate cold water was located in shallow layer, with a temperature of less than l.0°C.
c) Near Cape Navarin cold and low salinity water mass located in thevicinity of Siberian Continent where in the south, there was a warm andhigh salinity. Water mass near Cape Navarin may be divided into three
types.
7. The waters of high concentration of pH at the surface located in the areaof Unalaska Island and increased towards Bristol Bay.
8. The transparency shows the higher in the C-water mass (see Fig. 32) andlower near U nalaska Island.
9. The dissolved oxygen at the surface in the Berig Sea range from 4.43 CC/L
to 11.05 CC/L and it decreased along the Aleutian Islands and increased towards
the east region of Kamchatka Peninsula and Bristl Bay.
10. According to catch distribution from 1952 to 1960 in general, fin whale
grounds divided in to five area.

OCEANOGRAPHY AND WHALING GROUND IN THE SUBARCTIC

153

That is,a) Off Kamchatka Peninsula
Whaling grounds off Kamchatka Peninusla located from the east area of
Kamchatka Peninsula to the vicinity of Attu Island. Such in 1956 and1959 when the whaling ground was found at the northern region of the
Komandorski Islands coincied with relatively higher in sea-temperature.
b) Southern side of the Aleutian Islands
Whaling ground on the southern side of the Aleutian Islands (westlongitude) shifted to the southward around on 50°N longitude since
195 7. The whaling ground extends to east and west as a center to lat.
50°-51°N, and located in the water mass of returning flow (Kitano 1958).
c) Off U nalaska Island
Whaling operations in the northern ground of Unalaska Island commenced in 1954 and has carried out there ever since. The center of groundfluctuates in small range.
d) Off the west of St. Mathew Island
Whaling operations in this area carried out in 195 7 and 1960.
e) Off Cape Navarin
Whaling in this area carried out in 1957 and 1960. This groundis located near the mixing zone formed between the coastal water mass
along the Siberian Continent and the oceanic water mass of relatively
high temperature and salinity.
11. The results of Japanease whaling expeditions indicate that blue and sei
whales are found mainly in the southern waters of the Aleutian Islands.
12. Humpback whales are most prevalent in the waters south of the AleutianIslands (especially east of l 70°W) and are also found in near Cape Navarin andin Chukchi Sea.
13. Sperm whales are mainly captured along the Aleutian Islands.
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