EK60 Water Column Sonar Data Collected During DY1401

Gulf of Alaska Acoustic-Trawl Survey of Walleye Pollock (DY1401, 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 Shumagin Islands and Sanak Trough areas of the Gulf of Alaska (GOA) during the winter of 2014 to estimate the distribution and abundance of walleye pollock (Gadus chalcogrammus). The survey was conducted 21-28 February (Shumagin Islands 23-27 February; Sanak Trough 26 February), starting 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).