EK80 Water Column Sonar Data Collected During DY2401

The Midwater Assessment and Conservation Engineering (MACE) program of NOAA Fisheries (NMFS), Alaska Fisheries Science Center (AFSC), conducted acoustic-trawl (AT) stock assessment surveys in the Shumagin Islands and Pavlof Bay areas of the Gulf of Alaska (GOA) 4-12 February, 2024, to estimate distribution and abundance of walleye pollock (Gadus chalcogrammus). The survey was conducted aboard NOAA Ship Oscar Dyson (built in 2003, 64 meters, 2500 tons, 3100 hp), a research stern trawler equipped with acoustic and oceanographic instrumentation. The primary water column acoustic instrument for these surveys was a Kongsberg EK80 split-beam scientific echosounder system utilizing five frequencies (18, 38, 70, 120, and 200 kHz). The vessel departed Kodiak, Alaska on 4 February and conducted the Shumagin Islands survey 6-11 February, and the Pavlof Bay survey 9-10 February. A calibration of the EK80 echosounder system was conducted following vessel departure from Kodiak and prior to starting the survey on 4 February in Kalsin Bay, Kodiak Island, Alaska. Trawl operations were conducted using an LFS1421 mid-water trawl net equipped with a Kongsberg FS70 trawl sonar.