EK60 Water Column Sonar Data Collected During DY1702

Acoustic-Trawl Surveys of Walleye Pollock in the Gulf of Alaska (DY1702, 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 1 March and conducted the Kenai Bays survey (including Port Dick, Nuka Passage, Harris Bay, Aialik Bay, Resurrection Bay, Day Harbor, and Port Bainbridge) 2-5 March. The Prince William Sound, Hinchinbrook Trough and Middleton Island surveys were conducted 5-9 March. A calibration of the echosounder system was conducted during the previous cruise on 14 February in Volcano Bay, Alaska. The vessel arrived at its homeport of Kodiak, Alaska on 10 March, 2017.