Results of 2019 Chukchi Sea Acoustic/Trawl Survey

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.

There is substantial interest in the fishes of the Pacific Arctic region (northern Bering, Chukchi and Beaufort Seas) due to their important role in the food web, and the potential for human activities to influence these species. The arctic environment is changing rapidly. Sea ice extent and thickness has decreased and temperatures have increased dramatically in recent years. Temperatures have warmed and sea ice has declined faster than predicted by models, and there is substantial concern about the impacts of these changes on the ecosystem. Ecological research in the region has been sporadic. However, recent concern about the potential impacts of climatic changes and the impacts of human activities such as oil and gas development on the ecosystem has stimulated a substantial amount of sampling of fishes in the Pacific Arctic. Previous surveys in the area determined that pelagic fishes were dominated by large numbers of age-0 Arctic cod (Boreogadus saida), but that very few adults were present in the region. The lack of adults suggests that survivorship of age-0 Arctic cod is either very low or that these juvenile Arctic cod emigrate to other areas as they grow. To evaluate the role of the region as a nursery for these age-0 fish and how changes in the physical environment may further influence the ecosystem, we conducted two broad-scale acoustic-trawl surveys of the continental shelf of the ice-free U.S. Chukchi Sea in late summer 2017 and 2019. The work was conducted as part of the Arctic Integrated Ecosystem Survey program.