Population differences in the reaction of minnows to alarm substance

Experiments showed that minnows, Phoxinus phoxinus, sympatric with pike, Esox lucius, responded more vigorously to alarm substance than minnows from a population with no experience of pike predation in the wild. Minnows from the pike‐sympatric (Dorset) population were more likely to hide and less likely to risk feeding than their pike‐allopatric (Gwynedd) counterparts. The reaction to alarm substance in the pike‐sympatric population was further increased when it was presented along with the visual stimulus of a ‘stalking’ model pike. When the Dorset minnows experienced both alarm substance and the pike model together they reduced their inspection behaviour to a level below that of the Gwynedd minnows. Minnows from the Gwynedd (pike‐allopatric) population displayed increased levels of shoaling in the treatments in which alarm substance was used.