INDIVIDUAL-RESPONSES TO PREDATION RISK AND FOOD DENSITY IN PERCH (PERCA-FLUVIATILIS L.)

Perch, Perca fluviatilis, of different sizes and ages were allowed to choose between two feeding patches differing in food ratio and (or) pr edation risk (presence versus absence of a pike, Esox lucius). The aim of our study was to test whether food-patch choice and risk-taking be haviour (time with the predator present) were related to size, phenoty pe (fast-versus slow-growing) and (or) stage of development (mature ve rsus immature). Movements of individual fish were continuously monitor ed with an automatic system employing passive integrated transponder ( PIT) tags. Food distribution did not seem to be important in determini ng perch distribution. Predation risk, however, had a significant infl uence. 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 characteristi cs, both the slow-growing phenotype and the mature fish spending a sig nificantly lower proportion of time in the risky patch than the fast-g rowing and immature fish. Switching rates, which differed between char acter groups, also had an effect on growth rate, varying with predatio n risk.