Individual responses to predation risk and food density in perch (Perca fluviatilis L.)

Abstract

Perch, Perca fluviatilis, of different sizes and ages were allowed to choose between two feeding patches differing in food ratio and (or) predation risk (presence versus absence of a pike, Esox lucius). The aim of our study was to test whether food-patch choice and risk-taking behaviour (time with the predator present) were related to size, phenotype (fast- versus slow-growing) and (or) stage of development (mature versus immature). Movements of individual fish were continuously monitored with an automatic system employing passive integrated transponder (PIT) tags. Food distribution did not seem to be important in determining perch distribution. Predation risk, however, had a significant influence. The presence of a predator in a patch significantly reduced the proportion of time spent in that feeding patch by all perch. However, the strength of this effect was dependent on individual characteristics, both the slow-growing phenotype and the mature fish spending a significantly lower proportion of time in the risky patch than the fast-growing and immature fish. Switching rates, which differed between character groups, also had an effect on growth rate, varying with predation risk.