Assessing Pacific salmon populations for viability using the "viability and risk assessment procedure" model

Northwest salmon are listed under the Endangered Species Act and must be monitored for abundance, productivity, and harvest and hatchery impacts each year as recovery actions to the habitat are being conducted.  Various models have been constructed and used for analysis of these data.  The “Viability and Risk Assessment Procedure” (VRAP) is one such model.  It has been used in Puget Sound for Chinook and Chum salmon and in the Lower Columbia River for Chinook salmon.  The model is designed to handle the multiple age returns of Chinook salmon and to address risk to population viability due to the variability, natural and human induced, on population returns from year to year.  In this paper we test the sensitivity of the model with constructed “known” populations both with and without sampling error.  Population data are created using survival estimates at various stages in the life history and with introduced annual natural variability.  The model assesses the population using spawner recruit functions with environmental covariates included.  The performance of the model under various conditions of survival is discussed.   Results from Puget Sound Chinook populations are also discussed.