EK60 Water Column Sonar Data Collected During DY1701

Acoustic-Trawl Surveys of Walleye Pollock in the Gulf of Alaska (DY1701, EK60). The Midwater Assessment and Conservation Engineering (MACE) program of NOAA Fisheries, Alaska Fisheries Science Center (AFSC) conducted acoustic-trawl (AT) stock assessment surveys in the Gulf of Alaska (GOA) during the winter and early spring of 2017 to estimate the distribution and abundance of walleye pollock (Gadus chalcogrammus). These surveys were conducted aboard NOAA Ship Oscar Dyson, a 64 meter stern trawler equipped with acoustic and oceanographic instrumentation. The primary instrument for the surveys was a Simrad EK60 split-beam echosounder system utilizing five frequencies (18, 38, 70, 120, and 200 kHz). The vessel departed Kodiak, Alaska on 7 February and conducted the Shumagin Islands survey (including Shumagin Trough from Renshaw Point to Simeonof Island, Stepovak Bay, Unga Strait, and West Nagai Strait) 8-11 February. The Sanak Trough survey was conducted on 11 February followed by the Morzhovoi Bay survey on 12 February. The vessel transited to Pavlov Bay and conducted the Pavlov survey 13-14 February. A calibration of the echosounder system was conducted on 14 February in Volcano Bay, Alaska. The vessel returned to its homeport of Kodiak, Alaska on 16 February, 2017.