Results of 2017 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 (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.

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.

Go to https://www.ngdc.noaa.gov/mgg/wcd/ or email Anderson, Charles (charles.anderson@noaa.gov)

The data set is still being analyzed and will not be available for distribution until it has been finalized and all QA/QC practices have been performed. Contact the Data Point Of Contact for estimated time of release.

These data were collected in accordance NOAA protocols for fisheries acoustics surveys and related sampling (Alaska Fisheries Science Center), 23 p. Prepared by Midwater Assessment and Conservation Engineering Program, Alaska Fish. Sci. Center, Natl. Mar. Fish. Serv., NOAA. Available online: http://www.afsc.noaa.gov/RACE/midwater/AFSC%20AT%20Survey%20Protocols_Feb%202013.pdf

"IT Security and Contingency Plan for the system establishes procedures and applies to the functions, operations, and resources necessary to recover and restore data as hosted in the Western Regional Support Center in Seattle, Washington, following a diserruption."

Acoustic data were recorded at the five split-beam frequencies using ER60 software and, as a backup, acoustic telegram data were logged with Myriax EchoLog 500 software. Acoustic measurements were collected from 16 m below the sea surface to within 0.5 m of the sounder-detected bottom or a maximum of 1,000 m in deep water. Data were analyzed using Myriax Echoview post-processing software. See National Marine Fisheries Service (NMFS) 2013. NOAA protocols for fisheries acoustics surveys and related sampling (Alaska Fisheries Science Center), 23 p. Prepared by Midwater Assessment and Conservation Engineering Program, Alaska Fish. Sci. Center, Natl. Mar. Fish. Serv., NOAA. Available online: http://www.afsc.noaa.gov/RACE/midwater/AFSC%20AT%20Survey%20Protocols_Feb%202013.pdf