ME70 Water Column Sonar Data Collected During DY0901

Gulf of Alaska Acoustic-Trawl Surveys of Walleye Pollock (DY0901, ME70). The Midwater Assessment and Conservation Engineering (MACE) program of NOAA National Marine Fisheries Service (NMFS), Alaska Fisheries Science Center (AFSC) conducted acoustic-trawl (AT) stock assessment surveys in the western Gulf of Alaska (GOA) during the winter of 2009 to estimate the distribution and abundance of walleye pollock (Theragra chalcogramma). The vessel departed Kodiak, Alaska on 12 February and conducted echosounder system calibrations in Three Saints Bay, Kodiak Island, Alaska. The vessel conducted the Shumagin Islands survey (including Shumagin Trough, Stepovak Bay, Renshaw Point, Unga Strait, and West Nagai Strait) 15-18 February. The vessel then surveyed Sanak Trough on 18-19 February, followed by a survey of the continental shelf break from Sanak Island to Unalaska Island 19-20 February. The vessel conducted equipment research operations utilizing a lowered target strength transducer system 21-22 February and arrived in Dutch Harbor, Alaska on 22 February. The primary acoustic echosounder system for this survey was a Simrad EK60; a Simrad ME70 multibeam echosounder system was also operated for the duration of the cruise. The survey was conducted aboard NOAA Ship Oscar Dyson, a 64 meter fisheries research stern trawler equipped with acoustic and oceanographic instrumentation.