Composition and trophic structure of a fish community of a clear water Atlantic rainforest stream in southeastern Brazil (original) (raw)

2001, Environmental Biology of Fishes

As part of a larger project that aimed to determine the factors that regulate fish productivity in a clear water river of the Atlantic rainforest, São Paulo State, Brazil, composition and the trophic structure of the fish community of the middle course of the river were studied from January 1995 to May 1996. Of the 17 species collected, Mimagoniates microlepis, Schizolecis guentheri, Phalloceros caudimaculatus and Kronichthys heylandi accounted for 83.2% of the total fish abundance. Most of the species were insectivorous (35.7%), followed by detritivores (21.4%), benthivores (14.2%), omnivores (14.2%), herbivores (7.1%), and piscivores (7.1%). Results of food overlap analysis as calculated by the Index of Morisita showed that 17.5% of the species pairs overlapped. Habitat segregation, however was observed among most of the species, suggesting some degree of food partitioning. Despite the characteristics of this escarpment river, which produces spates year round, no seasonal variation in diet was observed, suggesting that although food abundance may fluctuate throughout the year, most items are in constant supply. The importance of allochthonous food was considered and it appears that, though only a few species feed on this source (including detritivores), they make up 87.2% of the total fish abundance. The low abundance of most of the fishes, the high number of endemic species and the strong dependence of the species on a few food resources suggest that these systems are sensitive to anthropogenic impacts and require future studies. 1 Buckup, P.A. 1998. Biodiversidade dos peixes da Mata Atlântica. pp. 1-9. In: Base de Dados Tropical (ed.) Biodiversity Angermeier & Karr (1983) suggest that large scale alterations in forest structure may have serious impacts on stream biodiversity, affecting effects of shading, discharge variability, siltation and available food types. Although some studies on fish communities of clear water streams of the Atlantic rainforest describe community composition and main food habits of species (Sabino & Castro 1990, Uieda 1995, Buck 2000), several aspects of the ecology of these communities still remain unknown. As the escarpment clear water river here studied is subject to unusual conditions as spates throughout the year, which may provide changes patterns of South and Southeast Atlantic Rainforest.