Reconstruction of Bristol Bay sockeye salmon returns using age and genetic composition of catch
Cunningham, Curry J
Hilborn, Ray W.
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The purpose of this report was to reconstruct historical sockeye salmon (Oncorhynchus nerka) runs to Bristol Bay, Alaska for use by the Alaska Department of Fish and Game (ADF&G) in evaluating biological escapement goals for component populations. Annual inshore run sizes (1963-2011) were reconstructed for each of the 18 observed age classes by partitioning annual catches from the mixed-stock terminal fishing districts and accounting for observed interception of stocks in non-destination fishing districts. Age and genetic composition of catch data were used to partition catches and estimate escapement age composition for years in which those data were unavailable. Results of this reconstruction process indicate that in western Bristol Bay the traditional run reconstruction methods routinely overestimated the productivity (recruits/spawner) of Igushik River (mean: 32%) and Nushagak River (mean: 15%) stocks while underestimating the productivity of the Wood River stock. In eastern Bristol Bay, differences in annual productivity estimated by the run reconstruction procedure incorporating both age and genetic-composition of catch data and that estimated by traditional methods were more varied across the time series, with productivity of the Egegik River stock routinely overestimated (mean: 9%) and productivity of the Alagnak River stock routinely underestimated (mean: 15%) by the traditional method.
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