Localized Depletion of Three Alaska Rockfish Species Dana Hanselman NOAA Fisheries, Alaska Fisheries Science Center, Auke Bay Laboratory, Juneau, Alaska
Biology, Assessment, and Management of North Pacific Rockfishes 493 Alaska Sea Grant College Program • AK-SG-07-01, 2007 Localized Depletion of Three Alaska Rockfish Species Dana Hanselman NOAA Fisheries, Alaska Fisheries Science Center, Auke Bay Laboratory, Juneau, Alaska Paul Spencer NOAA Fisheries, Alaska Fisheries Science Center, Resource Ecology and Fisheries Management (REFM) Division, Seattle, Washington Kalei Shotwell NOAA Fisheries, Alaska Fisheries Science Center, Auke Bay Laboratory, Juneau, Alaska Rebecca Reuter NOAA Fisheries, Alaska Fisheries Science Center, REFM Division, Seattle, Washington Abstract The distributions of some rockfish species in Alaska are clustered. Their distribution and relatively sedentary movement patterns could make localized depletion of rockfish an ecological or conservation concern. Alaska rockfish have varying and little-known genetic stock structures. Rockfish fishing seasons are short and intense and usually confined to small areas. If allowable catches are set for large management areas, the genetic, age, and size structures of the population could change if the majority of catch is harvested from small concentrated areas. In this study, we analyzed data collected by the North Pacific Observer Program from 1991 to 2004 to assess localized depletion of Pacific ocean perch (Sebastes alutus), northern rockfish S.( polyspinis), and dusky rockfish (S. variabilis). The data were divided into blocks with areas of approxi- mately 10,000 km2 and 5,000 km2 of consistent, intense fishing. We used two different block sizes to consider the size for which localized deple- tion could be detected. For each year, the Leslie depletion estimator was used to determine whether catch-per-unit-effort (CPUE) values in each 494 Hanselman et al.—Three Alaska Rockfish Species block declined as a function of cumulative catch.
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