Seasonal variation in the use of food resources by small fishes inhabiting the littoral zone in a Neotropical floodplain lake

This study evaluated the effect of seasonality on diet composition and overlap in fish species inhabiting the littoral zone of a small lake. We analyzed whether the way the species exploit food resources may help explain their coexistence. Fish samples were collected in a lake in the Upper Paraná River floodplain in September (dry period) and December (rainy period) of 2010. The diet of six species was evaluated through stomach content analysis, which showed that the most consumed resources were microcrustaceans, aquatic insects, aquatic higher plant and algae. Diet composition was significantly different between periods for all species studied. Diet overlap values were low in both periods, but trophic segregation was even higher in the rainy period, indicating that with greater abundance of food resources, species could exploit preferential resources. Trophic segregation, evidenced by the low overlap values in both periods, indicates the absence of interspecific competition, which may explain the coexistence of these species in the littoral zone of this small lake.