Food resource used by small-sized fish in macrophyte patches in ponds of the upper Paraná river floodplain

Abstract

This study analyzed the diet of seven small-sized fish species (Characidae) and assessed their use of food resources. The species were collected in 2001 from nine ponds with aquatic macrophytes in the Paraná river floodplain, Brazil. Astyanax altiparanae, Astyanax fasciatus, Hemigrammus marginatus and Moenkhausia intermedia consumed aquatic and terrestrial insects. Bryconomericus stramineus and Moenkhausia sanctaefilomenae co-dominantly ate insects and microcrustaceans, whereas Hyphessobrycon eques had microcrustaceans as their most important food resource. Overlapping feeding coefficients varied from intermediate (0.4-0.6) to low (< 0.4) for the majority of the combination pairs. A high mean intestinal length was verified for A. altiparanae and A. fasciatus, while a smaller mean was found for H. eques. When comparing all these results, it is possible to conclude that the species were partially segregated by the trophic niche dimension. Thus, the co-existence and higher abundance of these small fish in the shoreline of the ponds is explained by high feeding adaptability, absence of specializations in the feeding tract (except intestinal length) and the wide food supply provided by aquatic macrophytes.