FISHERY BULLETIN: VOL. 69, NO. 3 



is more efficient than planchet counting, produc- 

 tivity samples were routinely counted on plan- 

 chets in a gas-flow geiger detector for conven- 

 ience. The efficiency of the geiger counter was 

 determined by counting a standard source of 

 known activity so that absolute activity of the 

 samples could be related to those of the stock 

 solution. 



Samples for chlorophyll a, phosphate, silicate, 

 and nitrate-nitrite were also drawn from the 

 water bottles. Nutrient samples were frozen 

 in plastic bottles and returned to Seattle for anal- 

 ysis. Phosphate and silicate concentrations 

 were determined by methods given by Strickland 

 and Parsons (1965), and nitrate-nitrite samples 

 were analyzed by the method of Wood, Arm- 

 strong, and Richards (1967). 



Four liters of water from each sampler were 

 filtered through glass-fiber filters (Gelman, type 

 A) ,° stored in a dark desiccator at about 0° C, 

 and returned to Seattle for chlorophyll a anal- 

 yses. A layer of MgCOa was added to the filter 

 prior to filtration. Chlorophyll a concentrations 

 were determined by the method of Richards with 

 Thompson (1952) but were computed with equa- 

 tions given by Parsons and Strickland (1963). 

 Chlorophyll samples on the glass-fiber filters 

 were ground in a tissue grinder as suggested 

 by Yentsch and Menzel (1963). The resulting 

 suspension was filtered through a very-fine-por- 

 osity (VF) fritted-glass disk under pressure, 

 and the cake of residue remaining on the disk 

 was stirred with a few ml of 90 ''r acetone and 

 refiltered. Absorbances at 750 ni/u, which in- 

 dicate turbidity, of the resulting effluents were 

 seldom more than 0.010 per cm of light path 

 and then only in the more highly colored sam- 

 ples. A series of 20 tests showed no more than 

 traces of pigment remaining in the residue after 

 the first wash. The above treatment for separat- 

 ing residue from samples was preferable to cen- 

 trifugation because it resulted in generally lower 

 turbidity and more complete recovery of extract. 



Total incident solar and sky radiation (over 

 the wavelength range 0.3 to 3 n) was continu- 

 ously measured and graphically recorded by a 



" Gelman Instrument Co., P.O. Box 1448, Ann Arbor, 

 Mich. 48106. 



pyranometer. Although the photosynthetically 

 active portion of the spectrum is roughly half 

 the total radiation (Edmondson, 1956), total 

 radiation values were used in productivity cal- 

 culations. Salinity and temperature were mea- 

 sured and standard weather observations were 

 recorded near the productivity stations (Lar- 

 rance, 1971). 



Measurements of productivity, chlorophyll a, 

 and nutrients at various depths were integrated 

 to the bottom of the euphotic zone (designated 

 here as that depth where light intensity is 1% 

 of the surface intensity), or other specified 

 depth, and the integrated values expressed per 

 square 'meter of sea surface. Mean values for 

 several oceanographic domains were computed 

 by weighting the values according to distances 

 between stations. Details of the calculations 

 were given in Larrance (1971). 



PHYSICAL OCEANOGRAPHY 



The physical oceanography of the Pacific Sub- 

 arctic Region has been described by Fleming 

 (1955) , Dodimead, Favorite, and Hirano (1963) , 

 and Tully (1964). On the basis of data from 

 Ocean Station "P" (lat 50° N, long 145° W), 

 Dodimead etal. (1963) divided the upper 1,000 m 

 of the Subarctic Pacific Region into three perma- 

 nent zones: an upper zone from to about 

 100 m depth; a halocline from about 100 to 200 m 

 through which the salinity increases downward 

 by about l%c; and a lower zone from about 200 

 to 1,000 m. During the spring and summer, 

 warming of the surface layers causes a tempo- 

 rary thermocline in the upper zone which is 

 subsequently destroyed by cooling in the autumn. 

 Consequently the lower limit of the wind-mixed 

 upper layer ranges from about 30 to 60 m in 

 the spring and summer and extends to the top 

 of the permanent halocline at 100 m during 

 winter. The upper zone in the Subarctic Pa- 

 cific has been divided by Dodimead et al. (1963) 

 into Coastal, Alaskan Stream, Central Subarctic, 

 Western Subarctic, and Transitional Domains 

 (Figure 2). 



The Coastal Domain south of the Aleutian 

 Islands lies over the continental shelf and is 

 strongly influenced by Bering Sea water mixed 



598 



