Resource partitioning among syntopic Characidae corroborated by gut content and stable isotope analyses

Abstract

We aim to test the hypothesis that an assemblage of characid fishes coexist by partitioning food resources. We calculated dietary niche overlap of four syntopic species of the Characidae using gut content analysis. Secondly, we used a carbon (13C) and nitrogen (15N) isotope Bayesian mixing model to estimate relative assimilation. All characids consumed large proportions of plant material and aquatic insects; however, Pianka’s index indicated low dietary overlap among species throughout most of the sampling period. The low degrees of dietary overlap were due to discrepancies in the relative consumption of Ephemeroptera and aquatic insect remains. Secondly, there was high correspondence between the gut content analyses and isotope mixing model estimates. Astyanax xiru and Bryconamericus iheringii were the only species that ingested and assimilated large fractions of aquatic plants and algae, respectively. Astyanax procerus consumed and assimilated large fractions of terrestrial invertebrates, whereas Bryconamericus sp. assimilated mainly aquatic invertebrates. Therefore, we demonstrate that the assimilated nutrients were consistent with the relative consumption of food items. These results are consistent with the hypothesis that this characid assemblage may coexist via resource partitioning.