ABSTRACT
Environmental variation affects the availability of spatial and trophic resources in Amazonian streams and may be important factors structuring the diet of fishes. We analyzed the diet composition and trophic niche breadth of the lebiasinid splash tetra, Copella arnoldi, aiming to evaluate how environmental variation in Amazonian streams affects the species' trophic niche. Fish were captured and environmental factors were recorded in 20 streams in the Caxiuanã National Forest, in the eastern Amazon, in November 2010. We made a semi-quantitative analysis of stomach contents of 200 individuals. Copella arnoldi exhibited an omnivorous diet composed mainly of detritus and allochthonous invertebrates. Environmental variation (stream width, stream depth, canopy cover and flow) did not affect the diet composition or trophic niche breadth of the species, possibly due to the regional integrity of the forest within the boundaries of the protected area. Riparian cover probably minimizes the effect of the small-scale variations in food resources, thus leading to a locally homogeneous diet composition in the splash tetra C. arnoldi. (AU)
Subject(s)
Amazonian Ecosystem , Ecology , Fishes , Food ResourcesABSTRACT
We described the feeding habits of Colomesus asellus from riverbanks of the upper-middleTocantins River, Central Brazil. Two sampling expeditions were carried out in August (dry season) and inOctober (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 betweenindividuals captured in the dry season and in the rainy season. Individuals exhibited marked temporalsegregation, with a predominance of adults on the riverbanks during the dry season and the predominanceof juveniles in the rainy season. The diet of this species was based on diverse benthic prey, mostlyEphemeroptera nymphs (Insecta). Contrary to our expectations, the diet composition of C. asellus was notinfluenced by seasonal changes or ontogenetic factors, but the size of individuals determined the numberof prey consumed. Thus, C. asellus can be classified in its trophic ecology as an insectivore without relationwith fish size and seasonality.
Descrevemos os hábitos alimentares de Colomesus asellus capturados nas margens do rioTocantins, Brasil Central. Duas expedições de coleta foram realizadas em agosto (estação seca) e emoutubro (estação chuvosa) de 2013, a jusante da Usina Hidrelétrica de Lajeado, Estado do Tocantins. Adieta de C. asellus foi caracterizada e comparada entre juvenis e adultos e entre indivíduos capturados naestação seca e na estação chuvosa. Os indivíduos apresentaram marcada segregação temporal, compredominância de adultos nas margens do rio durante a estação seca e predominância de juvenis na estaçãochuvosa. A dieta desta espécie foi baseada em diversas presas bentônicas, principalmente ninfas deEphemeroptera (Insecta). Contrariamente às nossas expectativas, a composição da dieta de C. asellus não foiinfluenciada por mudanças sazonais ou fatores ontogenéticos, mas o tamanho dos indivíduos determinou onúmero de presas consumidas. Assim, a espécie pode ser classificada como insetívora, sem variação em suaecologia trófica relacionada à sazonalidade do ambiente ou ao seu tamanho.