. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder . I Figure 32-10. Distribution of Pacific herring in October and the relationship of adults (mature) and juveniles (immature) to salinity gradients. (Modified from Rumyant- sevand Darda 1970.) have been made to estimate herring biomass by a Soviet hydroacoustic trawl survey, ecosystem model- ing, and aerial surveys of spawning biomass. In 1963, three years after the fishery began, the eastern Bering Sea herring biomass was estimated to be million mt, based on a Soviet hydroacoustic su
. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder . I Figure 32-10. Distribution of Pacific herring in October and the relationship of adults (mature) and juveniles (immature) to salinity gradients. (Modified from Rumyant- sevand Darda 1970.) have been made to estimate herring biomass by a Soviet hydroacoustic trawl survey, ecosystem model- ing, and aerial surveys of spawning biomass. In 1963, three years after the fishery began, the eastern Bering Sea herring biomass was estimated to be million mt, based on a Soviet hydroacoustic survey of the wintering grounds (Shaboneev 1965). A recent paper by Kachina (1978), using the same data, reduced this earlier estimate to million mt by using a lower mean school density— fish/m^ — than the original estimate, which used fish/m^. According to Shaboneev, schools were surveyed at night and the area and height of schools were mapped acoustically; school composition and age distribution were determined by trawling. The density used in the original estimate ( fish/m^) was determined by comparing acoustic echograms from the eastern Bering Sea to echograms of schools sampled by purse seines in western Bering Sea coastal water. The revised estimate of fish/m^ is based on densities observed in surveys of herring concentra- tions in the winter grounds northwest of the Pribilofs during 1969-71 (N. Fadeev, TINRO, Vladivostok, , personal communication). The densities derived are questionable but cannot be fully eval- uated because few specific details of Soviet survey methods and accuracy are available. However, data reported in the literature and from people involved with herring hydroacoustic surveys indicate that the range of densities used by the Soviets may be ex- treme; an intermediate value may be more realistic. Recently, a numerical ecosystem model was applied to estimate the biomass of eastern Bering Sea herring (Laevastu and Favorite
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