Trophic structure of ichthyofauna in streams of the Contas River basin, Brazil

Understand how environmental factors correlate with the trophic structure of fish communities is a fundamental step to allow designing models for the functioning of stream ecosystems and planning conservation actions. Thus, this study aims to characterize the trophic structure of fish communities of streams of the Contas River basin and evaluate the relationships between local environmental factors (stream structure and limnological variables) and trophic structure. We sample nine streams of the Upper Contas sub-basin and nine of the Gongogi sub-basin using electric fishing. We analyzed the diet of 24 species, arranged in six trophic guilds, according to stomach contents: detritivores, omnivores, insectivores, invertivores, piscivores, and algivores. The results show high proportions of detritivores (46.62%), omnivores (28.55%), and insectivores (11.8%). Invertivores were correlated to colder streams, and with little proportion of sand in the substrate. Algivores were positively related to temperature and proportion of sand in the substrate. The relationship between other guilds and the environmental factors was not significant, probably due to limitations in the number of streams in the analysis. The sub-basins did not differ regarding the trophic structure, corroborating the perception that the trophic structure is more influenced by local factors than by broader scale factors.