The role of riverine forests for food supply for the omnivorous fish Brycon opalinus Cuvier, 1819 (Characidae) in the Serra do Mar, Southeast Brazil

O objetivo foi caracterizar a dieta do peixe Brycon opalinus (Characidae) sazonalmente e localmente, sendo possível determinar os itens alimentares e as relações tróficas com os ambientes aquáticos e terrestres. A área de estudo abrange três rios (Paraibuna, Ipiranga e Grande) da bacia do Paraibuna, Sudeste do Brasil. Foram realizadas doze coletas mensais de janeiro a dezembro de 2004. O grau de repleção estomacal e o grau de acúmulo de gordura visceral foram analisados, assim como o comprimento intestinal em cada classe de comprimento total. A freqüência de ocorrência e o grau de preferência alimentar (GPA) dos itens alimentares de Brycon opalinus foram obtidos separando-se os itens vegetais e animais, autóctones e alóctones, por ordem de insetos e por família de vegetais consumidos. A freqüência de ocorrência dos itens de origem animal equivale à dos de origem vegetal, caracterizando assim a onivoria na alimentação de Brycon opalinus.The purpose of this study was to characterize the diet of the fish Brycon opalinus (Characidae) seasonally and locally, allowing for the determination of its food items and trophic relations with the aquatic and terrestrial environments. The study area encompasses three rivers (Paraibuna, Ipiranga and Grande) in the basin of the Paraibuna, southeast Brazil. Twelve monthly collections were made from January to December 2004. The degree of stomachic repletion and of accumulated visceral fat was analyzed, as was the intestinal length in each class of total length. The frequency of occurrence and the degree of food preference (DFP) of the food items of Brycon opalinus were determined by separating the vegetal and animal items, autochthonous and allochthonous, by insect order and vegetal family consumed. The frequency of occurrence of items of animal origin was found to be equivalent to that of vegetal origin, thus characterizing the omnivorism of Brycon opalinus feeding.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP