Seasonal and ontogenetic diet patterns of the freshwater pufferfish Colomesus asellus (Müller & Troschel, 1849) in the upper-middle Tocantins River

Resumo

We described the feeding habits of Colomesus asellus from riverbanks of the upper-middle Tocantins River, Central Brazil. Two sampling expeditions were carried out in August (dry season) and in October (rainy season) of 2013, downstream from the Lajeado Hydroelectric Power Plant, Tocantins state. The diet of C. asellus was characterized and compared between juveniles and adults and between individuals captured in the dry season and in the rainy season. Individuals exhibited marked temporal segregation, with a predominance of adults on the riverbanks during the dry season and the predominance of juveniles in the rainy season. The diet of this species was based on diverse benthic prey, mostly Ephemeroptera nymphs (Insecta). Contrary to our expectations, the diet composition of C. asellus was not influenced by seasonal changes or ontogenetic factors, but the size of individuals determined the number of prey consumed. Thus, C. asellus can be classified in its trophic ecology as an insectivore without relation with fish size and seasonality.