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Biological benchmarks and building blocks for developing aggregate-level management targets for Skeena and Nass Sockeye Salmon, British Columbia

Regional Peer Review – Pacific Region

April 26-28, 2022
Virtual Meeting

Chairperson: Nicholas Komick


Under the renewed Pacific Salmon Treaty (PST) provisions, Fisheries and Oceans Canada (DFO) has agreed to complete a  comprehensive escapement goal analysis for Sockeye Salmon returning to the Skeena and Nass Rivers. An aggregate escapement goal for Skeena and Nass Sockeye Salmon is used to set Annual Allowable Harvests (AAH) for U.S. and Canadian fisheries targeting both stock aggregates. In addition to renewed PST provisions, biologically based escapement goals for Skeena and Nass River Sockeye Salmon are used for Canadian fishery management including the Nisga’a Treaty (British Columbia et al. 1999), First Nations and other fisheries in the Skeena and Nass Rivers.

Aggregate Sockeye Salmon returns to the Skeena and Nass Watersheds are comprised of numerous genetically distinct smaller stocks (Pestal et al., in prepFootnote 1), of which many are data-limited, and some are depressed and are considered stocks of concern. In addition, enhanced origin Sockeye Salmon from artificial spawning channels in two tributaries to Babine Lake account for a large proportion of aggregate Skeena Sockeye Salmon production. Canada is seeking to maintain the future productivity of Skeena and Nass Sockeye Salmon returns by maintaining the genetically unique wild Sockeye Salmon populations that contribute to overall returns consistent with Canada’s Wild Salmon Policy (DFO 2005).

The current aggregate escapement goals for Skeena and Nass Sockeye Salmon, based on previous estimates of aggregate spawner abundance to produce maximum sustained yield (Smsy) are 900,000 and 200,000 respectively (Bocking et al. 2002, Shepard and Withler 1958, Ricker and Smith 1975, Cox-Rogers 2013), do not take into account the complex stock structure of each aggregate, or the enhanced component of Skeena Sockeye Salmon from the Babine spawning channels. Furthermore, the productivity of Skeena and Nass Sockeye Salmon stocks has declined considerably in recent years. For these stocks, escapement goals based on maximum sustainable yield, which assumes long term average productivity, do not account for these changes and may not reflect current or future conditions.

Fisheries and Oceans Canada (DFO) Fisheries Management has requested that Science Branch develop and evaluate stock and aggregate-level biological benchmarks for Skeena and Nass Sockeye Salmon stocks that consider stock-level diversity, spawning channel capacity, and time-varying productivity. The assessment and advice arising from this Canadian Science Advisory Secretariat (CSAS) Regional Peer Review (RPR), will be used to inform the development of escapement goals for Skeena and Nass Sockeye Salmon through stakeholder engagement in a management strategy evaluation process that are consistent with the considerations described above, in addition to international obligations described in the Pacific Salmon Treaty (Chapter 2 para. 11).


The following working paper will be reviewed and provide the basis for discussion and advice on the specific objectives outlined below.

Pestal, G. and Carr-Harris, C. Biological benchmarks and building blocks for developing aggregate-level management targets for Skeena and Nass Sockeye Salmon (Oncorhynchus nerka)CSAP Working Paper 2018SAL05.

The specific objectives of this review are to:

  1. Develop an approach for the evaluation and selection of spawner-recruit model fits using alternative datasets and alternative model forms, including time-varying model forms, and apply this approach at the stock and aggregate levels for Skeena and Nass Sockeye Salmon.
  2. Develop an approach to identify plausible alternative productivity scenarios (e.g., long-term average vs. current productivity) and corresponding spawner-recruit parameter sets.
  3. Develop stock-level biological benchmarks using current datasets and appropriate methods for wild and enhanced Skeena and Nass Sockeye Salmon stocks including:
    1. Estimate and evaluate candidate biological benchmarks (e.g. Smsy, Smax, Sgen, Umsy) from model fits based on the plausible alternative productivity scenarios for wild Skeena and Nass Sockeye Salmon stocks.
    2. Review channel capacity and observed patterns in productivity for channel-enhanced Skeena Sockeye Salmon stocks originating from the Babine Lake Development Project.
  4. Compare alternative approaches for choosing aggregate-level biological reference points for Skeena and Nass Sockeye Salmon, and evaluate advantages and disadvantages for each approach.
  5. Identify priorities for future work to support the development of stock-specific escapement goals (DFO 2009) and aggregate reference points.
  6. Examine and identify uncertainties in stock-level benchmarks by comparing outputs generated using alternative spawner-recruit model forms and datasets, and compare uncertainties in aggregate reference points generated using alternative approaches.

Expected Publications

Expected Participation



Participation to CSAS peer review meetings is by invitation only.

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