Decision Analysis for the Reintroduction of Bull Trout into the Lower Pend Oreille River, Washington

The decision to reintroduce a species can be difficult owing to conflicting opinions and objectives as well as uncertainty over the outcome. Structured decision making addresses these considerations by identifying realistic fundamental objectives and building achievable management alternatives within a quantitative modeling framework. The process is driven by participation of stakeholders that represent diverse objectives, policy mandates, and opinions regarding decision alternatives. We applied structured decision making to evaluate the reintroduction of Bull Trout Salvelinus confluentus into the lower Pend Oreille River in northeastern Washington State. We engaged stakeholders from tribal, municipal, county, state, and federal agencies to specify fundamental objectives, formulate feasible reintroduction decisions, and conceptualize a modeling framework that included biological information and stakeholder assumptions. Stakeholders requested iterative decision sets to determine the optimal recipient streams and release strategies. The optimal decision-based on the fundamental objective of maximizing adult abundance at year 10-was artificial propagation of 4,500 juvenile Bull Trout coupled with translocation of 25 adult migrants to be reintroduced into a tributary and lake system (Sullivan Lake/Harvey Creek) that produced at least 18% more adult fish relative to alternatives. Sensitivity analyses were robust to the identity of the recipient stream (i.e., Sullivan Lake/Harvey Creek was always the optimal recipient stream) but suggested that maximizing the number of artificially produced juveniles released could generate a similar number of adult Bull Trout as the coupled-release strategy. Results also suggested that ensuring fish passage at Albeni Falls Dam on the main-stem Pend Oreille River could increase the abundance of adult fish. The process followed for this case study can be adapted to similar decisions regarding reintroduction or other translocations of fish in other systems.