Juvenile Chinook Salmon : A Need for Population-Specific Bioenergetics Models ?

Growth of juvenile salmonids is a critical variable affecting survival and recruitment to successive life history stages, essentially affecting the strength of subsequent cohorts. Consumption and temperature are key variables affecting growth for fishes in general. Temperature dictates the metabolic efficiency of prey conversion to production, and is thus a primary variable affecting growth. However, temperature optima and thresholds are variable for Pacific salmon populations. Yet many researchers using bioenergetic approaches to understand growth use temperature-dependent equations and coefficients for Chinook Salmon published in Steward & Ibarra (1991), which is based on adults from Lake Michigan, and uses coefficients from other salmonid species. To address this problem, we are using an approach using several lines of evidence to better understand relationships between temperature and growth. We focus this effort on juvenile Chinook Salmon used in the San Joaquin River Restoration Program, which seeks to restore the southern-most run in North America. Our approach includes a meta-analysis of growth rate and temperature relationships for wild populations, simulations with inSTREAM and bioenergetics models, and hatchery data sets. Results from these multiple lines of evidence suggest that juvenile Chinook Salmon growth rates in southern rivers are quite robust, despite the degraded conditions of these ecosystems. Our broader main objectives are to generate population and habitat specific bioenergetics algorithms and encourage a broader use of population-specific relationships of temperature and growth rate. A focus on these approaches can help fisheries managers set realistic expectations for restoration projects.