Stock status and lake-based production relationships for wild Skeena River sockeye salmon

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Abstract

This paper outlines stock status for wild Skeena River sockeye salmon based on updated assessments of freshwater production in nursery lakes, available catch and escapement data, and modelled exploitation rates. The aggregate stock is dominated by sockeye returning to the Babine Lake spawning channels at Pinkut and Fulton Creeks. In addition to Babine Lake, wild sockeye spawn in at least 28 other nursery lakes throughout the Skeena River drainage. Skeena River sockeye are harvested in mixed-stock marine commercial fisheries in south-southeast Alaska and northern British Columbia, in Skeena River First Nations food, social, and ceremonial fisheries, and in recreational fisheries within the Skeena River drainage. The fisheries primarily target the enhanced Babine Lake component which can withstand higher exploitation rates compared to the un-enhanced wild stocks.

Recent analyses of limnological, acoustical fall fry, and spawning ground survey data indicate that, in most cases, wild stock escapements are much too low to fully utilize lake rearing habitat and maximize smolt production. Although many lakes still require evaluation and production parameter estimates are still under review, our findings re-enforce previous assessments (Shortreed et al. 1998, 2001) concluding that the majority of Skeena nursery lakes that have been surveyed are oligotrophic, appear to be largely fry-recruitment limited (not enough spawners) and producing sockeye below potential production. In addition to recruitment limitation, some lakes are also being limited by factors such as low spawning ground capacity or quality, low in-lake growth and/or survival, nutrient limitation, glacial turbidity, and species competition. All of these factors act to reduce sockeye productivity and limit sustainable exploitation rates. Increased fry recruitment through increased escapements, combined with lake-specific restorative and/or enhancement techniques, has been suggested for improving sockeye production from non-Babine nursery lakes (Shortreed et al. 1998, 2001).