We conducted acoustic-trawl (AT) surveys of the US continental shelf region of the Chukchi Sea during ice-free periods (27 August to 26 September) with a focus on Arctic cod (Boreogadus saida), a key species in Arctic ecosystems. These surveys indicate that midwater fishes are dominated by age-0 Arctic cod, with large numbers of age-0 walleye pollock (Gadus chalcogrammus) found in the region for the first time. Age-0 Arctic cod abundances were significantly larger than observed in previous surveys. Age-0 Arctic cod were distributed north of 70 °N with the highest densities in the northeastern Chukchi Sea, west of 164 °W. Age-0 pollock were found between 66-72 °N. Additional key pelagic species included capelin (Mallotus villosus), saffron cod (Eleginus gracilis), Pacific cod (Gadus macrocephalus), and Pacific herring (Clupea pallasii). These four species were primarily found in coastal areas between 66.5-72 °N. The increase in age-0 pollock abundance suggests that environmental conditions now enable species from the south to colonize the Chukchi Sea, at least on a seasonal basis. Age-0 Arctic cod not found in significant abundance in the central and southern Chukchi as in previous surveys, indicating that changes in the environment may be restricting the southern extent of their distribution.

We conducted acoustic-trawl (AT) surveys of the Alaska northern Bering and Chukchi Seas during ice-free periods with a focus on Arctic cod (Boreogadus saida), a key species in Arctic ecosystems. The mixed species assemblages in the study area required a refinement of standard AT survey methods used in Alaska. These surveys indicate that midwater fishes are dominated by age-0 Arctic and saffron cod (Eleginus gracilis), capelin (Mallotus villosus), and Pacific herring (Clupea pallasii). Age-0 Arctic cod were distributed north of 70 °N, age-0 saffron cod were abundant in coastal areas between 66.5-69.5 °N, and Pacific herring were distributed south of 67 °N. Abundances of Arctic cod, saffron cod, herring and capelin all increased by more than factor of 2 in 2013 compared to 2012. Sizeable populations of age-0 Arctic cod were observed in the northern Chukchi Sea, which suggests that this area is an important nursery ground. However, relatively few larger Arctic cod were observed in this and other surveys of the area, which suggests that either overwinter mortality of age-0 Arctic cod is high, and/or these fish are not retained on the Chukchi shelf.

We conducted acoustic-trawl (AT) surveys of the Alaska northern Bering and Chukchi Seas during ice-free periods with a focus on Arctic cod (Boreogadus saida), a key species in Arctic ecosystems. The mixed species assemblages in the study area required a refinement of standard AT survey methods used in Alaska. These surveys indicate that midwater fishes are dominated by age-0 Arctic and saffron cod (Eleginus gracilis), capelin (Mallotus villosus), and Pacific herring (Clupea pallasii). Age-0 Arctic cod were distributed north of 70 °N, age-0 saffron cod were abundant in coastal areas between 66.5-69.5 °N, and Pacific herring were distributed south of 67 °N. Sizeable populations of age-0 Arctic cod were observed in the northern Chukchi Sea, which suggests that this area is an important nursery ground. However, relatively few larger Arctic cod were observed in this and other surveys of the area, which suggests that either overwinter mortality of age-0 Arctic cod is high, and/or these fish are not retained on the Chukchi shelf.

Eastern Bering Sea shelf walleye pollock (Gadus chalcogrammus) midwater abundance and distribution were assessed from Bristol Bay to the U.S.-Russia Convention Line between 12 June and 17 August 2016 using acoustic-trawl survey methods aboard the NOAA ship Oscar Dyson.

Scientists from the Alaska Fisheries Science Center conducted acoustic-trawl stock assessment surveys in the Gulf of Alaska during late winter and early spring 2019 to estimate the distribution and abundance of walleye pollock (Gadus chalcogrammus) at several of their main spawning grounds.

Shumagin Islands, Sanak, Morzhovoi, Pavlof

Scientists from the Midwater Assessment and Conservation Engineering (MACE) Program of the Alaska Fisheries Science Center's (AFSC) Resource Assessment and Conservation Engineering (RACE) Division conducted an acoustic-trawl (AT) stock assessment survey of the Shumagin Islands and Sanak. The Shumagin Islands survey was conducted 12-15 Feb., beginning in Shumagin Trough, continuing through Stepovak Bay, Renshaw, Unga Strait, Korovin Strait and ending in West Nagai Strait. The Sanak Trough area survey was conducted 15-16 Feb., followed by the survey of Morzhovoi Bay on 16 Feb.

Scientists from the Midwater Assessment and Conservation Engineering (MACE) Program of the Alaska Fisheries Science Center"s (AFSC) Resource Assessment and Conservation Engineering (RACE) Division conducted an acoustic-trawl (AT) stock assessment survey of

Scientists from the Midwater Assessment and Conservation Engineering (MACE) program of the Alaska Fisheries Science Center (AFSC) Resource Assessment and Conservation Engineering (RACE) Division conducted an acoustic-trawl (AT) survey of walleye pollock in the southeastern Aleutian Basin near Bogoslof Island aboard the NOAA ship Oscar Dyson during 7-15 March, 2012. The survey was designed with two survey tracks, which covered 3,656 nmi2 of the CBS Convention Specific Area. The primary survey track was nearest to the Aleutian Islands and consisted of 35 north-south parallel transects spaced 3 nmi apart and the second survey track was located just north of the primary survey track, and consisted of 12 north-south parallel transects space 9 nmi apart. These second survey track was essentially northern extensions of the primary survey track, designed to observe whether walleye pollock were present in deeper water. The survey followed established AT methods as specified in NOAA protocols for fisheries acoustics surveys and related sampling.

Scientists from the Midwater Assessment and Conservation Engineering (MACE) Program of the Alaska Fisheries Science Center's (AFSC) Resource Assessment and Conservation Engineering (RACE) Division conducted acoustic-trawl (AT) stock assessment surveys in the Gulf of Alaska (GOA) during late winter and early spring 2017 to estimate the distribution and abundance of walleye pollock (Gadus chalcogrammus) within several of their main spawning grounds. These pre-spawning pollock surveys covered the Shumagin Islands, Sanak Trough, and Morzhovoi and Pavlof Bays (DY2017-01; 8-14 February).