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) 1 June to 10 July 2021 to estimate the distribution and abundance of walleye pollock (Gadus chalcogrammus). The survey was conducted along the Gulf of Alaska shelf from the Islands of Four Mountains to Yakutat Trough. Survey operations were conducted aboard NOAA Ship Oscar Dyson, a 64 meter fisheries research vessel built in 2003 and equipped for stern trawling and included capabilities to collect acoustic, oceanographic, and biological scientific data. Acoustic data was collected for the survey using a Kongsberg Simrad EK80 split-beam echosounder system utilizing five frequencies (18, 38, 70, 120, and 200 kHz). Mid-water trawls were conducted using an LFS 1421 mid-water trawl net equipped with a Kongsberg Simrad FS70 trawl sonar. The survey was divided into two segments with the first segment conducted from 1 June to 20 and the second segment conducted 24 June to 10 July with a mid-survey port call in Kodiak. The vessel departed Kodiak, Alaska on 1 June and conducted a calibration of the EK80 system prior to starting survey operations. The survey areas included the Gulf of Alaska shelf from the Islands of Four Mountains to southeast Kodiak Island, the Shumagin Islands, Barnabas Trough, Shelikof Strait, Chiniak Trough, and the Gulf of Alaska shelf from southeast Kodiak Island to Yakutat Trough. A post-survey calibration of the EK80 echosounder was completed prior to arrival in Kodiak, Alaska on July 10.

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.

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 Shelikof Strait, Chirikof Shelfbreak, and Marmot Bay areas of the Gulf of Alaska (GOA) in the late winter of 2023 to estimate distribution and abundance of walleye pollock (Gadus chalcogrammus). This 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 the survey 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 March and conducted the Shelikof Strait survey 4-11 March, followed by the Chirikof Shelfbreak survey 11-14 March, and Marmot Bay 15-16 March. A calibration of the EK80 echosounder system was conducted prior to starting the previous survey on 12 February; a post-cruise calibration was conducted 13 March in Kaiugnak Bay, Kodiak Island, Alaska. Trawl operations were conducted using an LFS1421 mid-water trawl net.

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 Shelikof Strait area of the Gulf of Alaska (GOA) in the late winter of 2022 to estimate distribution and abundance of walleye pollock (Gadus chalcogrammus). This 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 the survey 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 8 March and conducted the Shelikof Strait survey 9-16 March. A calibration of the EK80 echosounder system was conducted prior to starting the survey on 8 March in Kalsin Bay, Kodiak Island, Alaska. Trawl operations were conducted using an LFS1421 mid-water trawl net.

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 Shumagin Islands, Pavlof Bay, Morzhovoi Bay, and Sanak areas of the Gulf of Alaska (GOA) 10-22 February 2023, 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 the survey 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 10 February and conducted the survey 14-20 February. A calibration of the EK80 echosounder system was conducted prior to starting the survey on 12 February Uyak Bay, Kodiak Island, Alaska. Trawl operations were conducted using an LFS1421 mid-water trawl net.

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 areas of the Gulf of Alaska (GOA) in the summer of 2023 to estimate distribution and abundance of walleye pollock (Gadus chalcogrammus). This 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 the survey was a Kongsberg EK80 split-beam scientific echosounder system utilizing five frequencies (18, 38, 70, 120, and 200 kHz). The survey was conducted in three segments (10-22 June, 30 June to 21 July, and 7-20 August) starting and ending in Kodiak, Alaska with two port calls also in Kodiak. The vessel departed Kodiak, Alaska on 11 June and conducted a standard sphere calibration on the Kongsberg EK80 echosounder system on 11 June in Uyak Bay, Kodiak Island, Alaska. The survey areas included the Gulf of Alaska Shelf (between 14 June and 17 August), the Shumagin Islands (18-20 June), Shelikof Strait (1-8 July), Barnabas Trough (15-18 July), and Chiniak Trough (19-21 July). A second calibration of the EK80 echosounder system was conducted on 12 August in North Arm, Nuka Sound, Kenai Peninsula, Alaska. Mid-water trawl operations were conducted using an LFS1421 mid-water trawl net. Water column CTD casts were conducted at select positions on most days throughout the cruise using a Sea-Bird Scientific SBE 911Plus water column profiling system. During the second segment of the cruise, experimental operations were conducted using an iXblue DriX unmanned surface vessel (USV) remotely operated from the vessel and/or shore stations. The USV was equipped with a Kongsberg EK80 echosounder system. Survey operations were concluded on 18 August and the vessel returned to port (Kodiak) on 20 August.

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 area of the Gulf of Alaska (GOA) in the late winter of 2021 to estimate distribution and abundance of walleye pollock (Gadus chalcogrammus). These surveys were 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 the survey was a Simrad EK80 split-beam scientific echosounder system utilizing five frequencies (18, 38, 70, 120, and 200 kHz). The vessel departed Kodiak, Alaska on 2 March and conducted the Shelikof Strait survey 3-10 March, and the Marmot Bay survey 13-15 March. A calibration of the EK80 echosounder was conducted prior to starting the surveys on 2 March in Kalsin Bay, Kodiak Island, Alaska and a follow-up post-cruise calibration was conducted in Kalsin Bay, Kodiak Island, Alaska on 15 March. Trawl operations were conducted using an LFS1421 mid-water trawl net.

The Midwater Assessment and Conservation Engineering (MACE) program of NOAA Fisheries, Alaska Fisheries Science Center (AFSC), conducted acoustic-trawl (AT) stock assessment surveys on the Gulf of Alaska (GOA) shelf and associated bays during the late spring and summer of 2019 to estimate the distribution and abundance of walleye pollock (Gadus chalcogrammus). The survey was conducted 30 May - 7 August 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 30 May and conducted the survey in three legs with all port calls in Kodiak; the project was completed in Kodiak on August 7. Leg 1 of the project was conducted 30 May \u2013 20 June on the Gulf of Alaska (GOA) shelf from the Islands of Four Mountains to outer Shumagin Trough including Sanak Trough, Morzhovoi Bay, Shumagin Islands area, and Mitrofania area. The leg 2 surveys were conducted 25 June \u2013 16 July in Shelikof Strait, Alitak Bay, Barnabas Trough, Chiniak Trough, and on the Alaska shelf. The leg 3 surveys were conducted 19 July \u2013 7 August and included Marmot Bay, Resurrection Bay, Prince William Sound, and the Alaska shelf from Kodiak to Yakutat Bay. Calibrations of the echosounder system were conducted in Kalsin Bay, Kodiak Island, Alaska at the start and end of the cruise; no significant differences in gain parameters or transducer beam pattern characteristics were noted between the two calibrations.

Gulf of Alaska Acoustic-Trawl Survey of Walleye Pollock (DY1103, EK60). The Midwater Assessment and Conservation Engineering (MACE) program of NOAA National Marine Fisheries Service (NMFS), Alaska Fisheries Science Center (AFSC) conducted acoustic-trawl (AT) stock assessment surveys during the late spring/summer of 2011 in the Gulf of Alaska to estimate the distribution and abundance of walleye pollock (Theragra chalcogramma). The survey was conducted on the Gulf of Alaska shelf extending from the Islands of Four Mountains to the Chiniak Trough east of Kodiak Island, 14 June to 12 August 2011, in three legs (leg 1, 14-29 June; leg 2, 5-22 July; leg 3, 6-12 August) aboard NOAA Ship Oscar Dyson, a 64 meter stern trawler equipped with acoustic and oceanographic instrumentation. The vessel departed Kodiak, Alaska on 14 June with intermediate port calls in Kodiak, Alaska. An extended port call occurred between legs 2 and 3 (22 July to 6 August) due to vessel mechanical issues. Smaller surveys were also conducted in several bays and around islands including Morzhovoi Bay (22 June), Sanak Trough (23 June), Pavlof Bay (25 June), the Shumagin Islands area (7-8 July), Mitrofania Island (9-10 July), Nakchamik Island (11-12 July), Shelikof Strait (16-21 July), Chiniak Trough (7-8 August), Barnabas Trough (9-10 and 11-12 August), and Alitak Bay (10-11 August). The cruise ended when the vessel arrived in Kodiak, Alaska on 12 August 2011.

Gulf of Alaska Acoustic-Trawl Survey of Walleye Pollock (DY1403, EK60). The Midwater Assessment and Conservation Engineering (MACE) program of NOAA National Marine Fisheries Service (NMFS), Alaska Fisheries Science Center (AFSC) conducted an acoustic-trawl (AT) stock assessment survey in the Shelikof Strait, Marmot Bay, and Izhut Bay areas of the Gulf of Alaska (GOA) during late winter/early spring of 2014 to estimate the distribution and abundance of walleye pollock (Gadus chalcogrammus). The survey was conducted 13-25 March (Shelikof Strait 15-22 March; Marmot and Izhut Bays 22-24 March), departing from Dutch Harbor, Alaska and ending in Kodiak, Alaska. The survey was conducted aboard NOAA Ship Oscar Dyson, a 64 meter stern trawler equipped with acoustic and oceanographic instrumentation. The primary instrument for the survey was a Simrad EK60 split-beam echosounder system utilizing five frequencies (18, 38, 70, 120, and 200 kHz).