EK60 Water Column Sonar Data Collected During DY1802

Acoustic-Trawl Survey of Walleye Pollock (Gadus chalcogrammus) in the Southeastern Aleutian Basin near Bogoslof Island (DY1802, EK60). The Midwater Assessment and Conservation Engineering (MACE) program of NOAA Fisheries, Alaska Fisheries Science Center (AFSC) conducted an acoustic-trawl (AT) stock assessment survey in the southeastern Aleutian Basin near Bogoslof Island during the winter of 2018 to estimate the distribution and abundance of walleye pollock (Gadus chalcogrammus). This survey was conducted aboard NOAA Ship Oscar Dyson, 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 1 March transiting toward the southeast Aleutian Basin 1-3 March. The survey was conducted in the Bogoslof Island area 3-7 March, with the vessel arriving in Dutch Harbor, Alaska on 7 March. A calibration of the echosounder system was conducted at the end of the previous cruise on 14 February in Kalsin Bay, Kodiak Island, Alaska.