. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder. Oceanography Bering 522 Fisheries oceanography 100. 1950 1955 I960 1965 Year-class 1970 1975 Figure 32-12. Abundance of Pacific herring year-classes in the eastern Bering Sea relative to the 1975 year-class. (From Naumenko 1979). Hydroacoustic surveys in the nearshore areas just before or during spawning are probably not practical because of the many widely scattered schools that are constantly moving through the shallow waters. Optimum results can be expected on the winter grounds,
. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder. Oceanography Bering 522 Fisheries oceanography 100. 1950 1955 I960 1965 Year-class 1970 1975 Figure 32-12. Abundance of Pacific herring year-classes in the eastern Bering Sea relative to the 1975 year-class. (From Naumenko 1979). Hydroacoustic surveys in the nearshore areas just before or during spawning are probably not practical because of the many widely scattered schools that are constantly moving through the shallow waters. Optimum results can be expected on the winter grounds, when herring are relatively stationary and concentrated. Results of surveys conducted during late winter to early spring could be applied in time for management of the roe fisheries. Spawn surveys convert the amount of spawn deposited to size of adult population, using age-sex- size composition and fecundity data. Such surveys would have to be conducted immediately after spawning so as not to be affected by losses from predation and storms. The vast size of the area, including distances between spawning areas, lack of subtidal spawning information, and various logistical problems currently render this method impractical for the eastern Bering Sea. In spite of limitations due to weather and narrow time-area coverage, aerial surveys may be one of the most cost-effective ways of measuring the abundance of spawning herring. School distribution within a limited area should be intensively studied to deter- mine if surveys are more effective at particular times and to assess the variability of schools along sighting tracks. Aerial biomass estimation procedures and species identification procedures need to be developed. If a model of spawning school distribu- tion could be developed, then statistical procedures could be used to overcome some of the weather and time limitations. Satellite technology may be used to augment aerial surveysMarge schools may be ob- servable at distances fro
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