Effects of Thermal Stress on Survival and Abundance of Wild Brook Trout in North Temperate Lakes

Brook trout (Salvelinus fontinalis) are common in waters ranging from the Appalachian Mountains to the Arctic Circle. These popular, coldwater sport fish face an uncertain fate in light of several climate change scenarios. Assessing the potential influence of variable temperature and hydrological regimes on brook trout populations poses an important challenge to fisheries biologists. We conducted a robust design mark-recapture study in three lakes in New York's Adirondack Park to estimate population parameters related to survival, abundance, detection probability and movement under contrasting thermal conditions. Each lake provides either ample, minimal or no thermal refuge during the warm summer months due to differences in morphometry, landscape position and stratification. The data analysis supports the hypothesis that brook trout experience reduced survivorship in lakes with little to no thermal stratification due to thermal stress in hot, dry years. Additionally, by incorporating covariates into the model set, the effects of a host of individual and environmental factors (e.g., body length, fat content, maximum summer water temperature, cloud cover, etc.) on movement, survival and detection probability were evaluated.