SUBARCTIC OCEANOGRAPHY IN RELATION TO
WHALING AND SALMON FISHERIESMICHITAKA UDA *INTRODUCTION

Since the year 1952 after the World War II the Japanese High Sea
Whaling and Salmon Fisheries were again undertaken with the oceanographic surveys every year and particularly since the NORP AC Projectin 1955 the oceanographic surveys covering the whole areas of Subarctic
North Pacific Waters from west to east were carried out during theyears of 1955-1960.
The present paper is a summary of oceanographic structure in thesubarctic waters of North Pacific Ocean (Uda, 1960, 1962) and the resultsof studies concerning hydrographic conditions in relation to the Whaling
and Salmon Fisheries with the purpose to give some useful prediction
indices for them.
SUBMARINE TOPOGRAPHY IN RELATION TO WHALING GROUNDSThe shaded steepest zone of continental slope is shown in Fig. 1 which

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Fig. 1. Zone of maximum bathymetric gradientcorresponds to the counterclockwise circulatory migration route of whales
and consequently contributes to some of the favourable whaling grounds.
Localities of maximum curvature of isobathymetrical lines (Fleming,* Tokyo University of Fisheries.
105*Fig. 2.

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Schematic map of waterma~ses and circulation in the Subarctic Pacific (1955-'58).

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SUBARCTIC OCEANOGRAPHY IN RELATION TO WHALING

1071955) appear to correspond to the particulary favourable whaling groundsrx, (3, r, iJ as shown in Figs. 2, 3 compared to Fig. 1., probably due tothe concentration of whales and abundant food organisms.
CURRENTS AND WATERMASSES IN RELATION TO WHALING AND
SALMON FISHING GROUNDS

Analysis of available hydrographic data collected in the North Pacific(north to 30°N) down to the 1000 m. depth or more for the years 1955'59, proved the principal three types of watermasses i. e. Subarctic,
Polar Frontal (including three subtypes) and Subtropical watermasses
with several characteristic gyres and currents as shown in Fig. 2.
The watermasses, gyres and circulations are corresponded to the
distribution, migration and conjectured stocks of salmons and whales ingeneral, as suggested by the results of tagging or marking experiments
and fishing grounds as the results of fishing exploition.
1. The averaged pattern of geostrophic circulation during the years
1955-'59 is shown in Fig. 3, based on the dynamic topography for dynamic
anomaly (0 db./1000 db.). The basic pattern referred to 500 db. or even300 db. as reference level is roughly the same to the above in the
Subarctic waters.

Fig. 3. Circulation based on geopotential topography.
Summer (1955-'58) tJD (0/1000 db.)

2. As a good indicator of Subarctic Watermass and a measure of
winter temperature, the extent of dichothermal water (intercooled water,
mainly produced in winter by convectional cooling and persists its trend
to summer) with its core depth was studied (Fig. 4.). Salmon is very
scarce in the domain of temperature less than l-2°C and very abundantin the domain of 4-7°C near the frontal zone of dichothermal cold core

MICHITAKA UDA

108

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Fig. 4.

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Dichothermal topography (Summer, 1955~'58)

and again very scarce in the warmer (subtropical) water above 12-13°C.
Salmon wintering grounds are roughly specified by the dichothermal
topography in the south of Aleutian and Kurile Chains.
Dichothermal structure in the western Subartic Waters is shallower
and well developed in contrast to the eastern waters which is deeper
and feeble. Those correspond to the densely concentrated salmons in
the upper shallower layer in the western waters of Subarctic high sea
compared to the deeply scattered fishes in the eastern waters.
The southern limit of distribution of dichothermal water and thenorthern limit of the intermediate (salinity minimum) water define thelocation of Polar Frontal Zone in which favourable fishing or whaling
grounds are found in general.
3. Surface salinity
The distribution of salinity in each year from 1955 to 1958 are shownin Figs. 5, 6, 7, 8. Fig. 9 indicates the map of oceanic fronts based on
the distribution of surface salinity during the summer season in theabove years (1955-'58).
The whaling grounds seem to avoid the saline core lying at the Okhotsk
Gyre, Bering Gyre and Alaskan Gyre (as well as Subtropical water) andto prefer the fringing zones around those cores of Gyres.
Salinity boundary looks to have more important meaning for thelocation of whaling grounds than water temperature, at least in the
Subarctic waters does.
4. Transparency of Sea Water or Clarity
The distribution maps of transparency measured by Secchi's disk areshown in Figs. 10, 11, 12, 13 for each year during 1955-'58. Fig. 14
is the averaged distribution of transparency of them. The shaded turbid

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SUMMER 1957 I'

Fig. 8. Surface salinity in Summer of 1958.

Fig. 7. Surface salinity in Summer 0f 1957.

150°

1957

SURFACE SALINITY0 ;0r-r·~~~~~~~~~~~~~~~_,

Fig. 6. Surface salinity in Summer of 1956.

SURFACE .SALINITY 0100
SUf1f1Ef? 1956 I'

Fig. 5. Surface salinity in Summer of 1955.

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Fig. 10. Transparency in Summer of 1955.

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SUBARCTIC OCEANOGRAPHY IN RELATION TO WHALING

111

correspond to the migratory routes, concentrated areas and segregatedpopulations of salmons and whales. Turbidity is mainly composed ofinorganic (mainly mud particles) and of organic (mainly planktonic origin)matters.

Fig. 12. Transparency in Summer of 1957.

Transparency in Summer of 1958.

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Fig. 14. Distr. of transparency in Summer of 1955~'58.

112

MICHITAKA UDA

5. Favourable whaling grounds at meridional sections
Several meridional sections illustrate in Figs. 16-22 the oceanic frontal
zone nearwhere the mode of whale catch (sperm whale and fin whal) are
shown e. g. at the meridional sections across the Aleutian Ridge Fig. 15.

Fig. 19.

Fig. 20.

Temp. and saltinity sections along AleutianIslands in contrast to the distr. of sperm
whale catch.

Fig. 21.

VERTICAL CIRCULATION AND WHALING GROUNDS

1. Vertical mixing and convection in winterTable 1 suggests us the infiuencial depth of convectional mixing in thenorthern subarctic water from winter and spring to summer within the200-300 m. depths from sea surface in winter almost completely and

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1935, 21, Aug.
Summer40°-38 1 N Bottom
146°-321 E 3385m

SOYO-MARU*l

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Depth Temp.
S<1t
02 02 Depth Temp. S
02
02 P
m
°C
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% mg/m3
08.44 32.18 25.02 8.01 119
0 12.80 32.45 6.55 106
25

1942, 14, July
Summer50°-21 1 N
148°-241 E

1939, 13, May
Winter-Spring
50°-47 1 N
145°-09 1E

1939, 26, April
Winter46°-27 1 N
144°-45 1 E

Depth Temp. S
Depth Temp.
S
Depth Temp.
S
m
°C
%0
m
°C
%0
m
°C
%o
0 -1.19 32.25
0 -0.55 32.07
0 -1.38 32.75

1939, 2, March
Winter45°-41 1 N
145°-101 E

RYOFU-MARU*lODOMARl*l

TABLE 1 VALUES OF TEMPERATURE, SALINITY, ui, 02, SATURATION DEGREE
OF 0 2 AND PHOSPHATE IN THE OKHOTSK SEA

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MICHITAKA UDA

114

gradually to the lower depths unto 500-600 m. incompletely with delayedphase lag in which saturation degree of dissolved oxygen is above 60%
in the Okhotsk Sea. Contrary to the deep water below the 800 m. depth
having 15-30%, the upper water of lower saline and richer oxygen is
flowing out through the Middle Kurile Straits into the water of Pacific
Ocean of different water type. Stronger convectional mixing continues
in tne Okhotsk and Bering Seas to the end of May in the upper layer.
2. The schematic pattern of watermasses and currents in the meridional
section are shown in Fig. 22.

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Fig. 22. Schematic circulation pattern in meridional section of North Pacific.

The inflow of Pacific Deep Water having salinity of 34.0-34.7%0 invades
in the bottom layers of Bering Sea and Okhotsk Sea, overflowing the
Aleutian and Kurile Ridges northwards which is basically different fromthe oceanographic structure in the North Atlantic Ocean.
3. In summer time the whaling grounds in the North Pacific Ocean
cover the area of Subarctic Watermass lying in the zone of 48-64° N as
their center.
The pattern of deep circulation in the North Pacific indicates also thegeneral ascending current or upwelling in the higher latitudes. As
favourable feeding grounds they depend on the higher productivity
aroused by the general upwelling area which is similar to the Antarctic
whaling grounds of fertilized waters by the prosperous upwelling
process (Uda, 1961a). (Fig. 16-21)

SUBARCTIC OCEANOGRAPHY IN RELATION TO WHALING

115

4. We recognize the evidence of the Intermediate Current of Subarctic
origin showing the second maximum of dissolved oxygen along theisopycnals of 26.20-26.80 and salinity minimum layer in the Polar Frontal
Zone between the latitudes of 38 and 42° N.
WHALING GROUNDS IN RELATION TO HYROGRAPHY

The whaling grounds for each species in the Aleutian waters and Bering
Sea north to 48° N during the years from 1955 to 1959 are shown in
Figs. 23, 24, 25, 26, 27.
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180'

11o•w

IW

Distribution of fin whale catch (1955-1959 accumulated).

1. We can not find fin whale grounds (Fig. 23) in the areas of theBering Shelf Water of low salinity in the eastern part in the Bering
Central Saline Water and also in the warm Alaskan Stream, probably
due to the poor food-organisms.
Their grounds are located along the several oceanic fronts probably
due to the plenty food-organisms concentrated by the vortical trains;(a) .... Anadir Front off the entrance of Anadir Bay,( (3 ) •••• Along the continental shelf edge particularly northwest to
the southern tip of shelf edge north off Alaskan Peninsula,( r ).... At the front of the warm South Aleutian Current and thecold Alaskan Gyre,( a ) .... Eddies east off Kamchatka Penninsula covering the waterof Kamchatka-Komandorskii Islands-Attu Island.

MICHITAKA UDA

116

As for example, sections at longitudes 180° and 170° W concerning
water temperature and salinity indicate the relationship between theprosperous whaling grounds and the oceanic fronts, located between thecold, low saline and turbid water and the warm, saline and transparent
water.
wo'w

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Fig. 24.

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180'

17(/'

w

Distribution of sperm whale catch (1955-1959 accumulated).

2. The sperm whaling grounds (Fig. 24) extend mostly around the
Aleutian Islands, especially on the northern side where the upper andlower waters mixed well, almost showing homogeneous water temperatureand salinity in the vertical and disappearance of dichothermal water,presumably due to the stronger turbulent mixing by tidal current andconvectional mixing on the Aleutian Ridge and also suggesting the plenty
food of squids around the Aleutian Islands Chain.
In the western part of the Subarctic Waters the dichothermal topography shows a shallower core depth of temperature minimum which
may correspond the lower boundary surface of sperm whale migration.
3. The sei whale grounds during 1955-'59 (Fig. 25) developes mainlyin the south of Aleutian Islands and concentrated to the top of the
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Distribution of sei whale catch (1955-1959 accumulated).

SUBARCTIC OCEANOGRAPHY IN RELATION TO WHALING

117

South Aleutian Current in the south of Middle Aleutian (170°W-180°,
49°-52° N).
4. The humpback whale grounds during 1955-'59 (Fig. 26) also lie
nearly along the south of Aleutian Chain.
Hv11fBA<K WHALu

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Distributian of humpback whale catch (1955-1959 accumulated).

5. The blue whale grounds during 1955-'59 (Fig. 27) lie along thesouth of the Western Aleutian (165° W-180°).
rw'

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Distribution of blue whale catch (1955-1959 accumulated).

CYCLIC CHANGE AND SEASONAL VARIATION

1. Seasonal or monthly variation of the distributed extents of watertypes or oceanographic elements (temperature, salinity etc.) shows rapidchanging state of environmental conditions of salmon etc. from winterthrough spring to summer decade by decade, particularly in the Aleutian
waters.
2. By his recent study (Uda, 1960, 196lb, 1962) (Fig. 2, 9) the author
convinced that the pulsational cycle travels across the Pacific Ocean in thehigher latitudes of prevalent westerlies flow west to east and come backfrom east to west in the lower latitudes of the prevalent Northeast Trade
Wind (Rodewald 1959). The warm water intrusion in the western pacificoccurs just concurrently with the cold water intrusion in the eastern
pacific and vice versa (according to the past records of half a century).

118

MICHITAKA UDA

3. The changing pattern of intruding shift from west to east appears
to occur with the cycle of several years.
The superposed isolines of geostrophic flow in one map during 1955'59 illustrates the above stated pattern of pulsation. Favourable catchyear of salmon and whale corresponds to the warm intrusion in thatarea.
The head of warm water intrusion located in the waters, south of
Hokkaido (in 1955), south of Kamchatka (in 1956), south of AleutianIslands (in 1957) and off British Columbia-Northwest of U.S. A. (in1958 and less in 1959) successively suggests us the migration patternof pulsating Polar Front in easterly direction with the transpacific timeinterval of 3-4 years which is expected to reflect on the fisheries conditionsof salmon, whale etc.
4. Temperature rise and fall in the ocean along Japan side occurs
almost conversely to that along American side in the pacific during thefifty years 1910-'59. The intermediate pattern between those extrema
on west and east coasts of pacific indicates the displacement of warmer
or cooler waters in succession in the higher and middle latitudes andlower latitudes from east to west during the cycle years.
The anomaly chart of water temperature for each year during 19101941 and 1952-1959 indicates transpacific travelling pattern from west
to east in the zone north to 30° N, on the contrary from east to west
in tne zone of 30° N to 0° (equator) still in question though conceivably.
5. The core atomospheric pressure difference between the great highand low depressions in winter i. e. those between the Siberian High, theAleutian Low and North Pacific High increased in the years from 1955
to 1959 in correspondence with the temperature rise in the east andtemperature drop in the west during that period.
The increase of above pressure difference suggests us the accelerated
geostrophic flow, and the intensified gyres with heat transport of warm
watermass from west to east (refer to Fofonof, 1960-'61).
6. Cyclic change in the North Pacific Circulation composed of Subarctic(Cold Water) Circulation and Subtropical with Tropical Warm Water
Circulation occurs with the period of 5-11 (in average 7-9) years.
7. Fluctuations of Kuroshio, California Current, North Equatorial
Current and Peru Current (El Nino) might be correlated with the prediction indices from one to another.

REFERENCESFLEMING, R.H. (1955): Review of the Oceanography of the Northern Pacific. pp. 1-43.
Bull. No. 2. International North Pacific Fisheries Commission.

SUBARCTIC OCEANOGRAPHY IN RELATION TO WHALING

119

RODEWALD, M. (1959): Beitriige zur Klimaschwankung im Meere (11), Die Ostpazifische"Wiirmewelle" von 1957/58, Deutsches Hydr. ZS. R. (5).
UDA, M. (1960): On the fluctuation and prediction of ocean temperature in the North
Pacific. The Memoirs of the Kobe Marine Meteorological Observatory. Vol. 14. 1-16.
(1961a): Deep Circulation in the Antarctic Ocean. The Antarctic Record No. 11.
pp. 831-835. Ministry of Education. Japan.
- - - (1961b): Cyclical fluctuation of the pacific tuna fisheries in response to cold andwarm water intrusions.
M. S. distr. Pacific Tnna Biology Conference, Honolulu,
Aug. 1961.
- - - (1962): Oceanography of the Subarctic Pacific. Journal of the Fisheries Research
Board of Canada (in press).
Fofonof, N. P. (1960, '61): Transport Computation for the North Pacific Ocean. 1955, '56,
'57, '58, '59, '60. Fisheries Research Board of Canada. MS. Rept. Ser. (Oceanographic
and Limnological). No. 77, 78, 79, 80, 85, 93.