Shimada and Kimura: Seasonal movements of Gadus macrocephalus 



Time (quarters) 



Residual 



Figure 7 



From the fit of the population dynamics model to the tagged 

 Pacific cod population: graph of expected versus observed tag 

 recoveries by quarter (top) and histogram of residuals by quar- 

 ter and area (bottom). 



(Hollowed and Low 4 ) than the tagging data. There- 

 fore, we conclude that observed movements in the 

 tagged population generally reflect the population 

 movements of Pacific cod in the eastern Bering Sea. 



Emigration and immigration relative to the 

 study area 



We provide direct evidence that Pacific cod migrate 

 from the eastern Bering Sea into the Gulf of Alaska. 

 Of the 95 winter recoveries made in Area 3, 21 of 

 these occurred in the Gulf of Alaska (Fig. 8; note that 

 Fig. 8 includes 30 Gulf of Alaska recoveries from all 

 seasons). Longline vessels operating in the winter 

 quarter between Sanak Island and Shumagin Bank 

 were the main source of returns. These data suggest 

 that 22% of fish found in Area 3 in winter may mi- 

 grate into the Gulf of Alaska. Multiplying this figure 

 by the population dynamics estimate of 78% (which 

 is the total eastern Bering Sea winter population 

 within Area 3), or by the 68% of the winter commer- 

 cial catch that is taken in Area 3, suggests that 15 to 



4 Hollowed, A. B., and L. L. Low. 1986. Productive gadoid fishing 

 grounds based on species assemblage analysis. In M. A. Alton 

 (ed.), A workshop on comparative biology, assessment, and man- 

 agement of gadoids from the North Pacific and Atlantic oceans. 

 Proceedings: part II, p. 681-712. Available: Alaska Fish. Sci. 

 Cent., NOAA, NMFS, 7600 Sand Point Way NE., Bin C15700. 

 Seattle, WA 98115-0070. 



Table 4 



Distribution of catch (numbers) by season and area 

 (Area l=the eastern Bering Sea shelf, Area 2=the 

 outer eastern Bering Sea shelf and upper slope, Area 

 3= the main spawning area), from 1982 to 1992, for 

 Pacific cod, Gadus macrocephalus, in the eastern 

 Bering Sea. Estimated from the Alaska and Pacific 

 Northwest Historical Groundfish Database (J. Ber- 

 ger, Alaska Fish. Sci. Cent., Seattle, WA 98 115-0070, 

 Personal commun., January 1993) and from the rela- 

 tive magnitude of trawl and longline catches. 



Season 



Area 1 



Area 2 



Area 3 



Winter 

 Spring 

 Summer 

 Fall 



0.085 

 0.496 

 0.703 

 0.176 



0.235 

 0.393 

 0.276 

 0.651 



0.680 

 0.111 

 0.021 

 0.173 



17% of the total population in the eastern Bering Sea 

 may migrate into the Gulf of Alaska during winter. 

 A number of individual longer-range migrations 

 tie together the Pacific cod population from 150° W 

 to 180° W longitude (Fig. 8). We note with interest 

 the recovery of two Bering Sea tags in the central 

 Gulf of Alaska near Cape Chiniak on Kodiak Island, 

 after 103 and 334 days. Other tagged Bering Sea 

 emigrants have been recaptured on the North 



