The Mechanistic Influence of Climate on Fish Population Dynamics and Distribution and Its Implications for Stock Assessment

Climate may impact fish population dynamics directly through changes in vital rates or indirectly through changes in connectivity or ecosystem productivity. This project aims to determine how variation in fish population vital rates and connectivity between subpopulations across time and space can account for observed shifts in distribution and productivity, how this variation can be incorporated into a stock assessment framework, and how this impacts management. The effect of climate on fish demographic rates and connectivity were considered as a potential driver of distribution patterns and explored through stock recruitment and biomass-productivity relationships. Simulations for Paralichthys dentatus included temperature as a covariate predictor of population life history parameters critical to population persistence. The effects of climate and spatial dynamics can be integrated into a spatially explicit stock assessment model. These simulations explored the impact of temperature-dependent life history parameters on biomass reference points (BRPs) estimated by age-structured stock assessment methods. The results decribe patterns in productivity over time as influenced by temperature to improve accuracy of future BRPs. The mechanistically-based population model elucidates the relative importance of climate in observed changes in abundance and distribution, and will allow for better predictive ability under various scenarios of climate change and fishing intensity.