EK60 Water Column Sonar Data Collected During DY1403

Gulf of Alaska Acoustic-Trawl Survey of Walleye Pollock (DY1403, EK60). The Midwater Assessment and Conservation Engineering (MACE) program of NOAA National Marine Fisheries Service (NMFS), Alaska Fisheries Science Center (AFSC) conducted an acoustic-trawl (AT) stock assessment survey in the Shelikof Strait, Marmot Bay, and Izhut Bay areas of the Gulf of Alaska (GOA) during late winter/early spring of 2014 to estimate the distribution and abundance of walleye pollock (Gadus chalcogrammus). The survey was conducted 13-25 March (Shelikof Strait 15-22 March; Marmot and Izhut Bays 22-24 March), departing from Dutch Harbor, Alaska and ending in Kodiak, Alaska. The survey was conducted aboard NOAA Ship Oscar Dyson, a 64 meter stern trawler equipped with acoustic and oceanographic instrumentation. The primary instrument for the survey was a Simrad EK60 split-beam echosounder system utilizing five frequencies (18, 38, 70, 120, and 200 kHz).