Cage fish farm causes the homogenization of wild fish diets of different sizes

Abstract

We evaluated the influences of cage fish farm on the individual diet of Geophagus sveni, a wild species nonnative to the Paraná river basin, and hypothesized that, in areas where there are no cage fish farms (CT), differences in feeding occur between larger and smaller individuals. In addition, in cage fish farm areas (CF), there are no differences in feeding between smaller and larger individuals due to the consumption of pelleted feed. For this, we evaluated the stomach contents of individuals of different body sizes sampled in CT and CF areas. We observed significant differences in diet between larger and smaller individuals only in the CT area, corroborated by positive and negative relationships between food items and standard length. In the CF area, we observed pelleted feed consumption by individuals of different sizes and only positive relationships between food items and standard length. Thus, the cage fish farms interfered with the consumption of natural food resources, promoting a more homogeneous diet among smaller and larger individuals. In this context, because of the importance of trophic segregation for intrapopulation coexistence and population stability, this homogenization can promote an imbalance in population dynamics.