Biological benchmarks and building blocks for aggregate-level management targets for Skeena and Nass Sockeye Salmon (Oncorhynchus nerka)

Abstract

Under the renewed Pacifc Salmon Treaty (PST) provisions, Canada has agreed to complete a comprehensive escapement goal review for sockeye salmon (Oncorhynchus nerka) returning to the Skeena and Nass rivers, which include 31 stocks with a range of life histories and observed productivities. We tested alternative spawner-recruit model fts, developed guidelines for chosing alternative productivity scenarios based on the model fts, and calculated biological benchmarks for the selected scenarios. We also compare alternative approaches for combining stock-level estimates of biological benchmarks into aggregate reference points. A large proportion of sockeye salmon returns to the Skeena originates from the Babine Lake Development Project (BLDP), a low-intensity enhancement program that consists of a series of spawning channels and managed river sections on two Babine Lake tributaries (Pinkut and Fulton). As part of this review, we summarized production trends in BLDP production data and found that while loading densities for these systems have remained relatively constant over time, the overall productivity for the enhanced component of Skeena sockeye has decreased during the past 20 years.