EK60 Water Column Sonar Data Collected During DY1807

Acoustic-Trawl Survey of Walleye Pollock (Gadus chalcogrammus) on the U.S. Bering Sea shelf (DY1807, 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 on the U.S. Bering Sea shelf (EBS) between Bristol Bay and the U.S.-Russia Convention Line between 6 June and 29 August 2018; the adjoining Russian portion of the EBS shelf was not surveyed. The survey was conducted aboard NOAA Ship Oscar Dyson, a 64 meter stern trawler equipped with acoustic and oceanographic instrumentation. The survey was conducted in three legs with the vessel departing Dutch Harbor, Alaska on 6 June and the cruise ending in Kodiak, Alaska on 26 August. The vessel departed Dutch Harbor on 6 June to begin leg 1 survey operations and ended leg 1 in Dutch Harbor on 28 June. The vessel departed Dutch Harbor on 1 July for leg 2 with survey operations conducted 3-7 July. A mechanical issue required the vessel to return to Dutch Harbor on 8 July ending leg 2. Following vessel repairs 8-23 July, the vessel departed Dutch Harbor on 25 July with survey operations for leg 3 conducted 25 July to 10 August and returning to Dutch Harbor on 11 August. Leg 3 continued with vessel departure from Dutch Harbor on 14 August and survey conducted 15-20 August. The vessel transited to Kodiak, Alaska 21-25 August and arrived in Kodiak on 26 August. 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 conducted a pre-cruise acoustic system calibration in Captains Bay, Dutch Harbor, Alaska on 7 June and a post-cruise calibration in Kalsin Bay, Kodiak Island, Alaska on 25 August.