Studies on the implications of dietary factors in growth hetogeneity in common perch Perca fluviatilis

Growth heterogeneity in fishes is influenced by environmental, genetic, behavioral and hormonal factors. All these factors interact to influence growth and, most of all, the alimentary functions which provide the fish with the energy necessary for its growth. Our work focuses on the implication of alimentary factors (ingestion, digestive capabilities, assimilation) that can influence growth heterogeneity in common perch (Perca fluviatilis). This work is part of a PhD, in association with a european-sponsored research programme on interspecific competition and cannibalism in reared predatory fishes. In a first step, we have seeked to establish a correlation between individual growth rate and food consumption, with the corollary question resulting from the putative existence of a feeding hierarchy in perch. These experiments have shown that sex, as early as the juvenile period, plays a key role in the determination of growth heterogeneity. As opposed to this, the social and feeding hierarchies do not seem to play an important role in growth heterogeneity in this species. The study of digestive enzymatic activities, assimilation rate, proteic turnover and speed of digestion however indicate that physiological factors do play a role in this phenomenon.