Mismatch in Chronology of Environmental Cues That Initiate Spawning Increases Predation Risk for Dispersing Lake...

Many species initiate reproductive activities, including migration and reproduction, in response to environmental cues that have historically been predictive of physical and biotic conditions favorable for offspring survival. Climate change can cause environmental variables including temperature levels and variability to become unreliable reproductive cues, potentially creating an evolutionary trap. For stream fishes inhabiting temperate environments, spawning may start at temperatures historically associated with high offspring survival; however, realized survival can be diminished due to mismatches with other ecological factors. We experimentally examined how an induced mismatch among historically temporally autocorrelated or matched stream physical and biotic environmental conditions present during lake sturgeon (Acipenser fulvescens) spawning and larval development and dispersal influenced larval predation rates. We used an artificial stream mesocosm to quantify the influences that matched or mismatched combinations of environmental variables including larval size (determined by incubation temperature), density of co-occurring prey species, lunar illumination levels, and interactions among factors had on larval lake sturgeon survival when exposed to rock bass (Ambloplites rupestris), a common stream predator. We documented comparatively higher survival during matched conditions when drifting prey density was high and larval body size was large, and when dispersal occurred during periods of simulated low lunar illumination. Survival rates decreased when the combination of ecological factors lake sturgeon larvae experienced was mismatched, and therefore, supported the prediction that lake sturgeon are vulnerable to a climatically induced evolutionary trap. Results suggested changing proportional contributions to population recruitment from early and late spawning lake sturgeon may be expected during years of matched compared to environmentally mismatched spawning conditions. Data supporting management efforts for species of conservation should be examined to determine the extent to which mismatched ecological conditions influence larval survival.