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DY1207 Bering Sea ME70
Scientists from the Midwater Assessment and Conservation Engineering (MACE) Program of the Alaska Fisheries Science Center (AFSC) have conducted summer surveys to estimate the abundance and distribution of walleye pollock (Theragra chalcogramma) on the eastern Bering Sea (EBS) shelf since 1979. Surveys have been conducted either annually or biennially since 1994. The 2012 acoustic-trawl (AT) survey was carried out between 7 June and 10 August aboard the NOAA ship Oscar Dyson. Its primary objective was to collect acoustic and trawl information to estimate walleye pollock midwater abundance and distribution on the U.S. and Russian Bering Sea shelf. Additional survey sampling included conductivity-temperature-depth (CTD) and expendable bathythermograph (XBT) casts to characterize the Bering Sea shelf physical environment, and supplemental trawls to improve acoustic species classification and to obtain an index of euphausiid abundance using multiple frequency techniques. A number of specialized sampling devices were used during the survey, including light level sensors; a Simrad ME70 multibeam sonar to image fish schools; an 83-112 bottom trawl modified to sample fish in midwater; a trawl-mounted stereo camera ("Cam-Trawl") designed to identify species and determine size and density of animals as they pass by the camera during a haul, and a small, bottom-moored, trigger camera system to autonomously collect images of fish on the seafloor.