Seasonal Temperature and Precipitation Related to Brook Trout Abundance Across the Southern Appalachian Mountains, USA

Forecasting fish population responses to climate change may be informed by retrospective analysis. We evaluated the influence of seasonal precipitation and temperature (PRISM) on abundance of age-0 and adult Brook Trout (Salvelinus fontinalis) using a hierarchical Bayesian framework that accounted for imperfect detection of individuals. The dataset comprised multiple-pass backpack electrofishing samples collected by governmental agencies over 33 years (1982-2014) from 291 sites spanning >800 km across the southern Appalachian mountains, USA. Covariates on detection included sampling day-of-year and total precipitation during the week prior to data collection. Observed effects of precipitation and temperature on abundance varied among seasons and fish age classes. For instance, above-average winter precipitation tended to decrease age-0 abundances in the following year (i.e., 95% Credible Interval < 0) but did not affect adult abundances, suggesting gravel scouring and loss of eggs during high winter flows. Above-average winter temperatures were associated with increasing age-0 abundances but decreasing adult abundances in the following year, demonstrating the importance of age-class specific effects. Analysis of spawner-recruit relationships indicated that age-0 abundance was more important for predicting adult abundance in the subsequent year than the converse.