EK60 Water Column Sonar Data Collected During SH1904

Acoustic-Trawl Surveys of Walleye Pollock (Gadus chalcogrammus) in the Gulf of Alaska (SH2019-04). 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 Shelikof Strait, Chirikof shelf break,and Marmot Bay areas of the Gulf of Alaska (GOA) in the late winter/early spring of 2019 to estimate the distribution and abundance of walleye pollock (Gadus chalcogrammus). This survey was conducted aboard NOAA Ship Bell M. Shimada, a 64 meter stern trawler equipped with acoustic and oceanographic instrumentation. The primary acoustic instrument for the survey was a Simrad EK60 split-beam echosounder system utilizing five frequencies (18, 38, 70, 120, and 200 kHz). The vessel departed Kodiak, Alaska on 6 March and conducted an acoustic system calibration in Kalsin Bay, Kodiak Island 7 March. The Shelikof Strait was conducted 7-16 March, the Chirikof shelf break sure was conducted 16-18 March, and the Marmot Bay survey was conducted 19-20 March. A post-cruise acoustic system calibration was conducted 20-21 March in Kalsin Bay and the vessel arrived in Kodiak, Alaska on 21 March.