EK60 Water Column Sonar Data Collected During DY1203

Gulf of Alaska Acoustic-Trawl Surveys of Walleye Pollock (DY1203, EK60). 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 Gulf of Alaska (GOA) during the late winter/early spring of 2012 to estimate the distribution and abundance of walleye pollock (Theraga chalcogramma). The survey was conducted along the Gulf of Alaska shelf break east of Chrikof Island (17-19 March) and throughout the Shelikof sea valley (20-26 March). The vessel departed Kodiak, Alaska on 5 March for the start of cruise DY1202 and was at sea for the start of the Chirikof shelf break survey. The vessel conducted a personnel transfer in Kodiak on 19 March then proceeded to the Shelikof Strait survey area. A post-cruise EK60 echosounder system calibration was conducted on 26 March in Malina Bay, Afognak Island, Alaska and the vessel returned to Kodiak at the completion of the cruise on 27 March. The survey was conducted aboard NOAA Ship Oscar Dyson, a 64 meter stern trawler equipped with acoustic and oceanographic instrumentation.