ECOLOGICAL CORRELATES OF FEEDING FLEXIBILITY IN NORTHERN PIKE (ESOX-LUCIUS)

We describe the summer diet and habitat use of northern pike (Esox lucius) in a small lake where potential fish prey were limited to one other species. During May, June, and July, pike fed almost exclusively on invertebrates. In August the diet was characterized by an increase in the frequency of vertebrates, a decrease in the number of prey items per stomach, an increase in mean prey size, and an increase in the percentage of empty stomachs. Direct observation by snorkel and SCUBA did not reveal a shift in the spatial distribution of pike during June, July, and August. Highest densities were recorded in shallow water with tall, penetrable vegetation. We suggest that the observed dietary change was not related to variation in habitat use, but rather to a change in the abundance of prey in the littoral zone. © Taylor & Francis Group, LLC.