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 US continental shelf region of the Chukchi Sea during ice-free periods (1 August to 27 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 68 °N with the highest densities in the northeastern Chukchi Sea, and age-0 pollock were found throughout the region north of 66 °N. Additional key pelagic species included capelin (Mallotus villosus), saffron cod (Eleginus gracilis), and Pacific cod (Gadus macrocephalus). These three species were primarily found in coastal areas between 66.5-72 °N. As had been previously observed, sizeable populations of age-0 Arctic cod were observed in the northern Chukchi Sea, which suggests that this area is an important nursery ground. 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.

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.

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.

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 survey’s primary objective was to collect acoustic data and trawl information to estimate midwater abundance and distribution of walleye pollock (Gadus chalcogrammus) in the Gulf of Alaska (GOA) Shumagins Region during late winter and early spring. Acoustic data were collected using five split-beam transducers (18, 38, 70, 120, and 200 kHz) and Simrad ER60 scientific echo sounders. Midwater and near-bottom acoustic backscatter was sampled using an Aleutian Wing 30/26 Trawl (AWT) and a poly Nor’eastern bottom trawl (PNE) with roller gear. This long-running survey has consistently provided data on the pollock population in the western GOA during winter and spring months.

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) survey of the Gulf of Alaska (GOA) shelf to estimate the distribution and abundance of walleye pollock (Gadus chalcogrammus) in summer 2017. Previous surveys of the GOA have also been conducted by the MACE program during the summers of 2003, 2005, 2011, 2013, and 2015. The 2017 survey covered the shelf from the Islands of Four Mountains to Yakutat Trough including many bays and troughs. Surface water temperatures across the GOA shelf averaged 11.6° C, overall, approximately 0.6° C cooler than in 2015 (mean 12.2° C) and 1.0° C warmer than in 2013 (mean 10.6° C), which were the only other surveys with comparable coverage. Large aggregations of age-0 pollock were observed throughout the survey but especially in the Shumagin Islands and Shelikof Strait areas. The estimated amounts of age-1+ pollock for the entire surveyed area were 2.64 billion fish weighing 1,341,973 metric tons (t). The majority of the pollock biomass was observed on the continental shelf (84%), Shelikof Strait (5%), near Mitrofania Island (3%), and east of Kodiak Island in Chiniak (2%) and Barnabas Troughs (4%). The majority (86%) of the biomass in the survey area consisted of age-5 fish from the 2012 year class. Compared to previous summer GOA surveys, fish weight at length was similar, but length at age was slightly smaller. Backscatter was attributed to species other than pollock when trawl verification, differentiation based on backscatter frequency response, or other methods allowed. Abundance and biomass estimates were calculated for Pacific ocean perch (Sebastes alutus; 305.9 million fish weighing 172,388 t), and backscatter distribution and abundance relative to previous surveys was estimated for euphausiids (primarily consisting of Thysanoessa inermis, but also including T. spinifera, T. raschii, and Euphausia pacifica).

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 routinely conduct acoustic-trawl (AT) stock assessment surveys in the Gulf of Alaska (GOA) during late winter and early spring to estimate the distribution and abundance of walleye pollock (Theragra chalcogramma). Historically, most of these efforts have been focused on the Shelikof Strait area, which has been surveyed annually since 1980, except in 1982 and 1999. The Shumagin Islands area has also been surveyed annually since 2005 with prior surveys in 1994-1996 and 2001-2003. Additionally, the GOA continental shelf break east of Chirikof Island to Barnabas Trough has been surveyed annually since 2002. In 2010, survey activities were expanded to include Morzhovoi Bay, Pavlof Bay, the bays along the southern coast of the Kenai Peninsula, and Prince William Sound. This report presents the distribution and abundance of walleye pollock for all AT surveys conducted in the GOA during February and March 2010 along with acoustic system calibration and physical oceanographic results.

Acoustic-trawl survey of prespawning pollock in Shelikof Strait

Eastern Bering Sea shelf walleye pollock (Gadus chalcogrammus) midwater abundance and distribution were assessed using 3 Saildrone autonomous vehicles due to Covid-19 restrictions.