Science Advisory Report  2015/022

Wild salmon policy biological status assessment for conservation units of interior Fraser River Coho Salmon (Oncorhynchus kisutch)

Summary

• The Wild Salmon Policy (WSP) outlines Fisheries and Oceans Canada’s (DFO) strategies for managing Canada’s salmon resources. The status assessment (Strategy 1) involves developing benchmarks and determining the biological status of Conservation Units (CUs).
• In order to apply the WSP status assessment strategy to Interior Fraser Coho (IFC) salmon (Oncorhynchus kisutch), abundance-based benchmarks were calculated, based on previously published methods, and a comprehensive set of population dynamics, abundance, trend, distribution, and productivity information were reviewed for each of the five CUs.
• A workshop of scientific experts was held to review and integrate the benchmarks and other information and recommend the WSP biological status for each of the 5 IFC CUs. A Delphi method was used to integrate expert opinions and to arrive at concensus-based status determinations. Status recommendations from the workshop were brought forward to this Canadian Science Advisory Secretariat (CSAS) Regional Peer Review process.
• The biological (abundance-based) benchmarks have moderate to high amounts of uncertainty. This uncertainty was considered in the assessment of status.
• The estimates of the upper and lower benchmarks of abundance from the stock-recruitment analyses were imprecise. In many cases, the confidence intervals for upper and lower abundance benchmarks overlap. The sum of median estimates (50% credible interval) of the upper benchmark for the five CUs is 17,147 spawners. The sum of median estimates of the lower benchmark across the five CUs is 8,654 spawners.
• Three CUs were determined to have an integrated status of AMBER (Middle Fraser, Fraser Canyon, South Thompson) and two were determined to have an integrated status of AMBER/GREEN (Lower Thompson, North Thompson).
• The sum of median estimates of the upper benchmark (80% of sum of median estimates of the upper benchmark (S_MSY)) is slightly below the Conservation Strategy for Coho Salmon (Oncorhynchus kisutch) Interior Fraser River Populations (IFCRT 2006) recovery objective of 20,000 to 25,000 spawners. That the summed 80% of S_MSY is close to Interior Fraser River Recovery Team (IFCRT) recovery objective highlights the risks of managing to S_MSY, as there appears to be negative consequences for the MU if abundances fall significantly below S_MSY.
• The WSP status metric values varied considerably over short time periods and it is recommended that these parameters be monitored annually, and reassessed when there are signs that productivity, spawner abundance, smolt-adult survival, or smolt production patterns change. The benchmarks and the integrated status should be reassessed if there are significant revisions to exploitation rates, total spawner, or hatchery-origin spawner data.
• This assessment found no evidence that smolt-adult survival has improved or returned to the higher productivity regime. Because the productivity is low, the sustainable harvest that can be expected from the management unit is also low relative to historic levels.
• Further work regarding potential harvest strategies, which include analyses for both high and low productivity regimes, is recommended.

This Science Advisory Report is from the November 6-7, 2014 Assessment of Interior Fraser River Coho Salmon Conservation Units’ Benchmarks and Status. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

Complete document (PDF, 219 KB)

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