QUASI: DISTRIBUTION OF ARCTIC COD 



the ocean surface (indicated by minus values for 

 level of apex in Tables 6 and 7) or below the 

 ocean bottom, then the appropriate adjustments, 

 discussed previously, were made. As a result, 

 estimates of juvenile cod at the IKMT stations 

 were influenced by both an inferred height of the 

 density structure and the depth of water beneath 

 the structure. Stations in relatively shallow water 

 and with a deeply submerged density structure 

 had the lowest estimates, and stations in water 

 deeper than average and with density structures 

 that reached to the surface had the highest. The 

 average for all stations was 28.5 juvenile cod/ 

 1,000 m3 (Table 8).^ 



Biomass of juvenile Arctic cod in the area 

 surveyed by WEBSEC-70 was estimated by con- 

 verting the overall average concentration to 

 volume and weight. Average volume of indi- 

 viduals in samples was 0.618 ml, with no apparent 

 size segregation with depth (Figure 5). If we 

 assume that the specific gravity of the cod 

 approximated unity (actually they were heavier), 



^This compares with an arithmetic average of 7.3/1,000 m^ 

 for the replicate hauls and 19.5 for the multidepth hauls— an 

 average of 13.4 for all hauls. Thus, simple arithmetic averaging 

 Yould seriously underestimate the value obtained under the 

 liypothesis of density structure with upwelling and down- 

 welling. Even higher values would be obtained if it is assumed 

 that the density structure continued to increase at the same 

 logarithmic rate below its depth of 47 m until the bottom 

 was reached, instead of having the increase truncated at 47 m. 

 This approach would require extrapolation well beyond all 

 observed values for fish densities and would not be fully con- 

 sistent with the welling part of the hypothesis. 



1.6 



1.5 



1.14 



_ 1 .3 



Q 1 .2 



O 



u 



I- ' ' 



u 



< 



u, 1 . 



> 0.9 



< 0.8 



Q 



> 



Q 0.7 



0.5 



5 OS 

 > 



UJ 



< o.a 



IT 

 LU 

 > 



<0.3 



0.2 - 



0.1 - 



0.0 



• • 



WEIGHTED MEAN = 0.618 ML 



• • 



10 



20 30 



DEPTH OF TOW (M) 



140 



50 



Figure 5. — Relation of average volume (milliliters) of indi- 

 vidual juvenile Arctic cod in IKMT tow to depth of capture, 

 eastern Chukchi Sea. 



Table 8. — Estimated volume of water and number of juvenile 

 cod beneath a standard swath at the IKMT stations, eastern 

 Chukchi Sea. 



then the stations averaged 17.6 g of juvenile 

 cod/1,000 m^. If we take the area surveyed in the 

 eastern Chukchi Sea as approximately 30 x 10^ 

 km^ (8,714 square nautical miles) and the 

 average depth as 40.0 m (the average for the 

 20 IKMT stations), then approximately 12 x lO^^ 

 m^ of ocean were contained in the sampling 

 area. Thus, it appears that 211.2 x 10^ g of 

 fish were represented by this volume, or 211.2 

 X 10^ metric tons, for an average of 0.7 metric 

 ton/km^ of ocean surface. 



Where did the juvenile cod originate? Likely 

 sources appear to be the Bering Sea, the East 

 Siberian Sea, or the Chukchi Sea itself. The north- 

 western part of the Bering Sea has particularly 

 low temperatures (Zenkevitch, 1963:824, 825) and 

 water from the Gulf of Anadyr tends to flow 

 northeastward (Zenkevitch, 1963:821). The East 

 Siberian Sea, of course, also has low temperatures 

 and apparently has an eastward-flowing current 



1103 



