Science Advisory Report  2011/018

Run Reconstruction and Escapement Goals for Alsek River Sockeye Salmon

Summary

• Alsek River Sockeye, including those sockeye returning to its tributary the Klukshu River, are considered a single Conservation Unit under the Wild Salmon Policy.  Management of this stock is conducted bilaterally through the Pacific Salmon Treaty (PST).
• The Salmon Standing committee of the Centre for Science Advice Pacific (CSAP) was presented updated analysis and results conducted by the Alaskan Department of Fish and Game (ADF&G) regarding the optimal escapement goals for Alsek and Klukshu River Sockeye salmon.
• Escapement and run reconstruction analysis incorporated stock assessment data from 1976 to 2008. Data and methods in the current analysis are considered an improvement over methods employed previously and take into account known sources of uncertainty.
• Bayesian analysis of data resulted in a posterior distribution for Smsy (spawning abundance needed to produce maximum sustained yield) with a mean of 29,710 sockeye and a median of 28,190 sockeye for the Alsek stock. Posterior distributions for Smsy for the Klukshu stock had a mean of 9,727 adults and a median of 9,102 adults.
• A range of optimal escapement goals, based on 60, 70, 80 or 90 % probability of achieving Smsy, is provided; allowing managers to make an informed decision when establishing escapement targets.
• Escapement goal ranges of 24,000 to 33,500 adults for the Alsek River and 7,500 to 11,000 adults for the Klukshu River were proffered in the reviewed report. These escapement ranges represented a 90-96% and a 79-90% chance of achieving at least 90% of MSY for the Alsek and Klukshu River’s, respectively.
• Given the incorporation of uncertainty in stock assessment data and the robust approach used to provide advice on the establishment of escapement goals, it is recommend that the methods used in this assessment be considered when providing escapement goal advice for other Canadian systems, where appropriate given the data available.

This Science Advisory Report has resulted from a Fisheries and Oceans Canada, Canadian Science Advisory Secretariat Pacific Regional Advisory Process. Additional publications resulting from this process will be posted as they become available on the DFO Science Advisory Schedule.

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