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 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 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 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 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 Shelikof Strait and Chirikof Shelf break areas of the Gulf of Alaska (GOA) 5-20 March, 2024, to estimate distribution and abundance of walleye pollock (Gadus chalcogrammus). The 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 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 5 March and conducted the Shelikof Strait survey 6-17 March, and the Chirikof Shelf break survey 17-19 March. A calibration of the EK80 echosounder system was conducted during a previous survey (DY2401) on 4 February in Kalsin Bay, Kodiak Island, Alaska, and a post-survey calibration was conducted in Uyak Bay, Kodiak Island, Alaska, on 9 March. Trawl operations were conducted using an LFS1421 mid-water trawl net equipped with a Kongsberg FS70 trawl sonar.

Acoustic-Trawl Survey of Walleye Pollock in the Gulf of Alaska (DY1706, 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 along the Gulf of Alaska (GOA) shelf and associated bays during the late spring and summer of 2017 to estimate the distribution and abundance of walleye pollock (Gadus chalcogrammus). The survey was conducted 8 June-16 August 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). The vessel departed Kodiak, Alaska on 9 June and conducted the survey in three legs with all port calls in Kodiak; the project was completed with the arrival of the vessel in Kodiak on 16 August. Leg 1 of the project was conducted 9-28 June along the Gulf of Alaska (GOA) shelf from the Islands of Four Mountains to Outer Shumagin Trough (12-18, 20-21, 22, and 26-27 June). Leg 1 survey areas included Sanak Trough (19 June), Morzhovoi Bay (19-20 June), Pavlof Bay (21 June), Shumagin Islands area (23-25 and 26 June), and Mitrofania area (25 June); the vessel transited to Kodiak 27-28 June. The vessel departed Kodiak on 3 July to start leg 2 (3-28 July) and conducted survey work in Shelikof Strait (3-8 and 10 July), Nakchamik area (9 July), Alitak Bay (12-13 July), initial survey of Barnabas Trough (14-15 July), and GOA shelf (9-10, 10-12, and July). The vessel returned to Kodiak on 15 July, ending leg 2, due to mechanical issues and departed Kodak on 28 July to start leg 3. Leg 3 work included surveys of Chiniak Trough (28-29 July), Barnabas Trough (31 July-1 August), Marmot Bay (3-4 August), and completion of GOA shelf work (3 July; 2 and 4-14 August). The vessel transited to Kodiak Island (14-15 August) and ended the project in Kodiak on 16 August. Sphere calibrations of the echosounder system were conducted in Kalsin Bay, Kodiak Island, Alaska on 9 June and 16 August; no significant differences in gain parameters or transducer beam pattern characteristics were noted between the two calibrations.

Acoustic-Trawl Surveys of Walleye Pollock (Gadus chalcogrammus) in the Gulf of Alaska (DY1803, EK60). 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 and Marmot Bay areas of the Gulf of Alaska (GOA) in the late winter/early spring 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 conducted an acoustic system calibration in Captains Bay, Dutch Harbor, Alaska on 12 March and departed Dutch Harbor on 13 March transiting toward Shelikof Strait. The Shelikof Strait survey was conducted 15-21 March followed by the Marmot Bay survey 21-22 March. A post-cruise calibration of the echosounder system was conducted at the end of the cruise on 23 March in Kalsin Bay, Kodiak Island, Alaska. The vessel returned to its homeport of Kodiak, Alaska on 23 March ending the cruise.

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 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.