AFSC/RACE/MACE: Results of 2012 Chukchi Sea Acoustic/Trawl Survey

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.

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. The abundance and distribution of midwater fishes over the Chukchi shelf remains poorly understood. As there are no large-scale commercial fisheries in the U.S. Arctic north of the Bering Strait , no abundance surveys are conducted to inform fisheries management. We conducted two broad-scale baseline acoustic-trawl surveys of the continental shelf of the ice-free U.S. northern Bering and Chukchi Seas in late summer 2012 and 2013 to address this knowledge gap. 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

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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