. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder. Oceanography Bering Walleye pollock 533 TABLE 33-3 Indices of age-class abundance measured by NMFS Crab-Groundfish research vessel surveys within a central area of the eastern Bering Sea during June to mid-August, 1973-78 (units = 10^ individuals per 159,100 km^).^ Survey Number of Number of Age-classes (yr) year trawls otoliths 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1973 111 490 - 1974 111 954 5
. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder. Oceanography Bering Walleye pollock 533 TABLE 33-3 Indices of age-class abundance measured by NMFS Crab-Groundfish research vessel surveys within a central area of the eastern Bering Sea during June to mid-August, 1973-78 (units = 10^ individuals per 159,100 km^).^ Survey Number of Number of Age-classes (yr) year trawls otoliths 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1973 111 490 - 1974 111 954 — — 1975 111 766 — — 1976 107 1990 1977 112 944 -- 1978 116 1256 — — — OveraU mean (1973-78) Standard deviation (1973-78) Coefficient of variation (1973-78) * Based upon estimates of nominal sampling effort, uncorrected for differences in effective fishing power. Italicized values were apparently affected by in- or out-migrations. 3r 1973 Size and age composition Rather than being a homogeneous pool, the eastern Bering Sea pollock population exhibits a size and age structure that reflects pulsed annual birth inputs, birth and survival rates, and a differentiation of distributional patterns based upon age. Pollock are generally considered to spawn during only one period each year. In the eastern Bering Sea, the spawning period has been reported to extend from the end of February thr
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