AbstractFathead minnows (Cyprinidae:Pimephales promelas) from a population that is sympatric with predatory northern pike (Esocidae:Esox lucius)exhibited a fright reaction to the visual stimulus of a live northern pike significantly more often than minnows from a population that is allopatric with pike. The fright response included increased use of shelter, dashing and freezing. Minnows from the pike‐sympatric population also exhibited a significantly greater fright response, measured as a reduction in activity, following exposure to chemical stimuli from pike (i.e. water from a tank that had contained a pike) than did minnows from the pike‐allopatric population. There was no significant change in activity by minnows from either population following exposure to chemical stimuli from nonpiscivorous peacock gudgeons (Eleotridae:Tateurndina ocellicauda), suggesting that the difference between the two populations is specific to stimuli from pike rather than a general difference in response to chemical stimuli from heterospecific fishes. Fathead minnows apparently utilize at least a two‐tiered predator recognition system that incorporates both visual and chemical
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