Predicting the effects of rainbow smelt on native fishes in small lakes: Evidence from long-term research on two lakes

We assessed predictability of negative interactions between native fishes and exotic rainbow smelt (Osmerus mordax) through field experiments and long-term data analysis for two lakes in Wisconsin. Predictions were made based on thermal preferences, diet characteristics, and published accounts of interactions between smelt and yellow perch (Perca flavescens) and smelt and cisco (Coregonus artedii). Our results indicate predation is the most likely cause for the extirpation of cisco from Sparkling Lake in 1990. In Crystal Lake, native yellow perch experienced significant overlap in distribution and diet with smelt. The condition of adult perch was negatively correlated with smelt abundance indicating competition was occurring. Smelt feed on a wide size range of prey items making this species a threat to native fishes, especially when spatial overlap is high. Information on spatial and temporal overlap and diet enable useful predictions about the effect of smelt invasions on native fishes.