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NOAA Technical Memorandum NMFS-AFSC-347

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Cooperative multispecies acoustic surveys in the Aleutian Islands


In Alaska, commercial fisheries have been implicated in the slow recovery of the endangered Western stock of Steller sea lions (Eumetopias jubatus; hereafter, W-SSL). To address this issue the Aleutian Islands walleye pollock (Gadus chalcogrammus; hereafter, pollock) fishery was closed in 1999. Although the fishery was reopened in 2005 to accommodate development of an economically struggling Aleutian Islands community, W-SSL critical habitat in the Aleutian Islands remained closed to pollock fishing. From 2006 through 2008, fishery biologists with the Alaska Fisheries Science Center (AFSC) in conjunction with an Alaska Native regional corporation, fish processors, and fishers explored the technical feasibility of conducting small-scale multispecies cooperative acoustic surveys in the Aleutian Islands.

The surveys were meant to provide spatially and temporally relevant estimates of groundfish biomass to set acceptable biological catch levels for a pollock fishery within one day’s transit from the community, including areas inside W-SSL critical habitat. This was intended as a means to open W-SSL critical habitat to the developing pollock fishery while reducing the probability of adverse interactions between the fishery and W-SSL stock. The surveys were designed by AFSC biologists but conducted by fishers on board commercial fishing vessels using scientifically calibrated echosounders. Biological data collected from the concurrent fishery were used to characterize acoustic backscatter. This report discusses the development of these surveys, the technical feasibility of conducting scientific grade surveys on board fishing vessels, the use of fishery data to supplement the acoustic surveys, and evaluates the uncertainty around estimates obtained in this manner.

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