PS 10-94 - Identifying a pathway toward recovery for depleted wild Pacific salmon populations in a large watershed under multiple stressors

Background/Question/Methods

Pacific salmon (Oncorhynchus spp.) support coastal and freshwater ecosystems, economies, and cultures, but many populations have declined. We used Priority Threat Management (PTM), a decision-support framework for prioritizing conservation investments, to assess management strategies to support thriving populations of wild salmon over 25 years. We evaluated the potential costs, feasibility, and benefits of 14 strategies spanning fisheries, habitat, pollution, pathogens, hatcheries, and predation management dimensions to 19 conservation units (CUs) - genetically and ecologically distinct populations - of Pacific salmon in the lower Fraser River, British Columbia, Canada.

Results/Conclusions

Based on the PTM assessment, under ‘business as usual’ zero CUs were predicted to have >50% chance of thriving in 25 years. Implementation of all management strategies at an annual investment between 45-110 million CAD was, however, predicted to achieve >50% chance of thriving for 16 of 19 CUs, with seven above 60% chance, indicating there is a pathway toward recovery for most populations if we invest now. In fact, substantial gains could be made by investing in five combined habitat strategies, costing 20M CAD annually. These habitat strategies were estimated to bring 14 of 19 salmon CUs above this 50% threshold. Co-governance between Indigenous and Canadian Crown governments to manage salmon populations and harvest, and improved CU-level monitoring emerged from the expert elicitation as critical ‘enabling’ strategies, underpinning the successful management of wild salmon in this region.

This research demonstrates the successful application of PTM to prioritize conservation investments for migratory species subject to multiple stressors and complex management structures. Our results emphasize the ability of holistic management approaches to support resilient wild salmon populations.