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Estimates of Biological Benchmarks for the Canadian-origin Yukon River Mainstem Chinook Salmon Stock Aggregate

Regional Peer Review – Pacific Region

January 18 – 20, 2022
Virtual Meeting

Chairperson: Erika Anderson

Context

In 2002, Canada and the United States (U.S.) confirmed the Yukon River Chapter of the Pacific Salmon Treaty (1985) where the spawning escapement goal of Canadian-Origin Yukon River Chinook was set at 33,000 to 43,000. This escapement goal was set based on the understanding of the dynamics of the stock and the specific assessment metrics used at that time. Since then, the metrics of assessment and associated data have become more informative and expansive, resulting in variations in this spawning escapement goal over the last two decades. These revised spawning escapement goals have always been considered interim in nature, until such time that a comprehensive review can be completed, and the Yukon River Salmon Agreement can be updated to reflect a new goal. There have been multiple analyses of the stock’s dynamics relevant to escapement goal considerations (Sandone 2010; Jones et al. 2012; Bue and Hamazaki 2014; Hamazaki and Decovich; Jones et al, 2018), but there have been no comprehensive reviews that were carried out entirely through joint Canada and U.S. efforts.

The Joint Technical Committee (JTC) is comprised of multiple Canadian and U.S. entities (including Fisheries and Oceans Canada [DFO]) and provides technical support to the Yukon River Panel (Panel). The JTC is charged to review existing assessment techniques and investigate new ways for determining total return and escapement and make recommendations on optimum spawning escapement objectives.  Furthermore, based on recommendations of the JTC, the Yukon River Panel may from time to time recommend spawning escapement objectives for implementation by the Governments of Canada and U.S. through their management entities (DFO and Alaska Department of Fish & Game [ADFG]), and the Panel may revise the spawning escapement objectives for rebuilt stocks.

In April 2019, the JTC signalled its decision to undertake a quantitative review of the Canadian-origin Chinook salmon escapement goal in response to the Panel’s expressed desire to explore the possibility of establishing a biologically-based escapement goal for this stock. As a critical first step, the JTC formed a bilateral working group comprised of individuals with expertise in the assessment and management of Yukon River Chinook salmon and individuals with expertise in modeling salmon population dynamics. The working group was tasked to review available data, develop statistical models, and estimate key biological benchmarks for the purpose of informing escapement goal recommendations.

DFO Treaties and Fisheries Unit, Yukon-Transboundary Rivers Area (YTRA), on behalf of the Joint Technical Committee of the Yukon River Panel, has requested that DFO Science Branch provide advice regarding estimates of biological benchmarks  for Canadian-Origin Mainstem Yukon River Chinook Salmon. This assessment will present an analysis and advice respecting biological benchmarks. Methods utilized for biological benchmark assessment will reference approaches and criteria previously developed (see Holt 2009a, Holt 2009b, Grant 2011, Fleischman and McKinley 2013).  The advice arising from this Canadian Science Advisory Secretariat (CSAS) Regional Peer Review (RPR) will be used to inform subsequent fisheries management recommendations to meet treaty/international obligations and Precautionary Approach commitments. Specifically, advice respecting biological benchmarks is needed to ensure that estimates are appropriate for informing future recommendations to the Yukon River Panel regarding escapement goals consistent with DFO’s Precautionary Approach (Fisheries and Oceans Canada 2009), emerging requirements under the 2019 amendments to Canada’s Fisheries Act (Fisheries Act, RSC 1985, c. F-14), and the State of Alaska’s Policy for the Management of Sustainable Salmon Fisheries and Policy for Salmon Escapement goals.

Objectives

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

Authors TBD. Estimates of Biological Benchmarks for the Canadian-origin Yukon River Mainstem Chinook Salmon Stock Aggregate. CSAP Working Paper 2013SAL02

The specific objectives of this working paper are, for the Canadian-Origin Yukon River Chinook stock aggregate, to:

  1. Develop a Bayesian integrated state-space run reconstruction and spawner recruitment model and fit it to available data.
  2. Derive estimates of biological benchmarks (e.g., Smsy, Seq, Smax, Sgen) and associated profiles (e.g., yield, recruitment, and overfishing).
  3. Document, and examine the consequences of, key data and methodological assumptions related to data weighting, biases in data, priors, and model structure.
  4. Explore, to the extent possible with available data, the sensitivity of biological benchmarks to change in escapement quality (e.g., total fecundity and egg mass) over time.
  5. Provide guidance on key considerations for next steps to identify an escapement goal and recommendations for future analyses and research to further develop them

Expected Publications

Expected Participation

References

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