Results of the 2009 eastern Bering Sea continental shelf bottom trawl survey of groundfish and invertebrate resources

Abstract

The Resource Assessment and Conservation Engineering Division of the Alaska Fisheries Science Center conducts annual bottom trawl surveys to monitor the condition of the demersal fish and crab stocks of the eastern Bering Sea continental shelf.  The standard study area encompasses a major portion of the eastern Bering Sea shelf between the 20-m and the 200-m isobaths and from the Alaska Peninsula north to approximately the latitude of St. Matthew Island (60°50'N).  In 2009, two chartered trawlers, the 40-m FV Arcturus and the 40-m FV Aldebaran, surveyed this area.  Demersal populations were sampled by trawling for 30 minutes at stations centered within 37.04 × 37.04 km (20 × 20 nautical mile) grids covering the survey area.  At each station, species composition of the catch was determined, and length distributions and age structure samples were collected from ecologically and commercially important species.

Three hundred seventy-six standard survey stations were sampled successfully.  A total of 94 species of fishes representing 21 families and 62 genera, as well as 168 species of invertebrates representing 13 phyla, were identified in the catches from the entire survey area.  The combined biomass of walleye pollock (Theragra chalcogramma), yellowfin sole (Limanda aspera), and rock sole (Lepidopsetta spp.) was 5.6 million metric tons (t) which was 63% of the total fish biomass.  The biomass of invertebrates was composed primarily of echinoderms (1.5 million t) and crustaceans (0.71 million t).

Survey results presented in this report include abundance estimates for fishes and invertebrates, geographic distributions and size composition of the more common fish species, and contour plots of surface and bottom temperatures during the survey sampling period.  Appendices provide station data, summarized catch data by station, species listings, and detailed analyses of abundance and biological data of the sampled populations.

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