Bayesian decision analysis for status of Snake River spring?summer Chinook salmon Oncorhynchus tshawytscha populations at extinction risk

Abstract

The viability of populations was assessed using population trend data and the Diffusion Approximation (DA) model. Various extinction risk metrics for a population are functions of the DA model parameters, and thus, estimates of the DA model parameters are key quantities. Using Bayesian methods, we showed uncertainty in those estimates, and further proceeded to a decision analysis to assess viability of populations. These methods were demonstrated using population trend data from return years since 1980 on naturally produced Snake River spring-summer Chinook salmon Oncorhynchus tshawytscha populations. Of 19 populations examined, the Catherine Creek population was assessed at serious risk, Tucannon River Spring and Grande Ronde Upper Main stem populations were assessed at minor risk, and the other populations were not at risk. This assessment helps managers to prioritize populations at risk for recovery management.