Table 26. — Estimated sexual maturity schedule for 

 eastern Bering Sea walleye pollock, 1976 spring trawl 

 survey. 



Age class 



(yr) 



Percentage 



mature 



Males 



Females 



1 + 



0.0 



0.0 



2 + 



5.6 



0.8 



3 + 



37.2 



28.9 



4 + 



80.0 



64.1 



5 + 



94.1 



84.2 



POLLOCK, MALES 



ALL SUBAREAS 



Bay (Fig. 36, 37). Overall, yellowfin sole occurred at 310 (71.3%) 

 of the 435 grid stations, at a mean abundance (CPUE) of 104.04 

 kg/km trawled (Table 27). 



Because an inshore migration of the population was apparently 

 in progress during the survey period, the survey data were ana- 

 lyzed in monthly time intervals in an attempt to improve the reso- 

 lution of real distributional features. Otherwise, because both the 

 progression of survey sampling and movements of high-density 

 concentrations of yellowfin sole followed the receding pack ice in- 

 to Bristol Bay, the overall apparent distributional pattern and 

 overall apparent population abundance (Table 27: "Mean 

 CPUE" column) were badly biased. Eastern Bering Sea yellowfin 

 sole have been generally recognized to make regular seasonal 

 migrations to outer continental shelf waters in winter and to inner 

 shelf areas in summer and early fall (Fadeev 1970; Wakabayashi 

 1974'). 



In April, sampling was limited to subarea 2 and small portions 

 of subareas 1, 3N, and 3S because of ice cover (Fig. 36). A large 

 concentraton of yellowfin sole showing extremely high catch rates 

 was encountered north of Unimak Island in this period. The max- 

 imum catch rate observed, 6,800 kg/km trawled, corresponded to 

 a density of approximately 2.9 individuals/m 2 . The concentration 

 was centered at depths of 90-100 m on the boundary of subareas 1 

 and 2. Catch rates declined very markedly near the ice edge. The 

 offshore limits of this concentration extended to about the 120 m 

 isobath. 



In May, as the ice edge receded north, the large Unimak Island 

 concentration apparently moved northeast towards Bristol Bay 

 (Fig. 36). Sampling in the northern sector of subarea 2 and in 

 subareas 3N and 3S, following the recession of ice, indicated two 

 smaller concentrations, one east of St. George Island and the 

 other west of St. Paul Island. These latter concentrations may 

 have been distributed under the ice in April. The two Pribilof con- 

 centrations and larger Unimak Island concentration have been 

 recognized in previous investigations (Fadeev 1970; Wakabayashi 

 et al. 1977 6 ). 



As ice cover continued to recede from the survey area in June, 

 the Unimak Island concentration appeared to disperse over the in- 

 ner Bristol Bay shelf (Fig. 37). The large concentration of 

 yellowfin sole observed in Bristol Bay during June may have been 

 composed of migrants from the Unimak Island group and in- 

 dividuals that overwintered under ice cover on the inner shelf. 

 Fadeev (1970) reported a population of small yellowfin sole that 

 apparently remained in Bristol Bay through winter. 



MMATURE DEVELOP SPAWN SPENT INACTIVE 



POLLOCK, SEXES 

 COMBINED 



ALL SUBAREAS 



IMMATURE OEVELOP SPAWN SPENT INACTIVE 



GONAD CONDITION 



Figure 35. — Reproductive condition of walleye pollock taken during the 

 1976 Bering Sea spring trawl survey. 



'Wakabayashi, K. 1974. Studies on resources of the yellowfin sole in the 

 eastern Bering Sea. I. Biological characters. Fishery Agency of Japan, Far Seas 

 Fisheries Research Laboratory, 1000 Orido, Shimizu 424, Japan. 77 p. 



•Wakabayashi, K., R. Bakkala. and L. Low. 1977. Status of the yellowfin 

 sole resource in the eastern Bering Sea through 1976. Fishery' Agency of Japan, 

 Far Seas Fisheries Research Laboratory, 1000 Orido, Shimizu 424. Japan, 45 p. 



Previous tagging studies have indicated a migration of 

 yellowfin sole from a wintering area west of St. Paul Island 

 towards Nunivak Island in spring (Wakabayashi see footnote 5). 

 The concentration encountered between the Pribilof Islands and 



50 



