Feeding ecology of a stream fish assemblage in an Atlantic Forest remnant (Serra do Japi, SP, Brazil)

Abstract

This study aimed to characterize the trophic structure of the fish assemblage in streams of the Serra Japi, an ecotonal area between the Atlantic Forest and inland forests of São Paulo State, Southeastern Brazil. Fish were collected with electrofishing equipment in 15 sites covering different regions, substrate types and riparian vegetation, distributed throughout the Caguaçú River, Caxambú, Piraí and Guapeva River micro-basins, during the rainy (January/February) and dry season (June) of 2007. The 589 specimens analyzed from 22 species, were assigned to different trophic groups, discriminated through a matrix of similarity, based on the food index (IA i ). The results show the formation of seven groups with a predominance of insectivorous and omnivorous species, followed by detritivores, piscivores, omnivore-carnivores and herbivores, which consumed mostly items of autochthonous origin, where algae and young insects were dominant. Canonical correspondence analysis (CCA), correlating the biomass of trophic groups to environmental variables, showed that omnivores, insectivores and omnivorecarnivores displayed a wide distribution, while detritivores, herbivores and piscivores were restricted to specific locations, related to different physical and chemical variables as total nitrogen, conductivity and temperature. Despite the increase in total biomass at the most urbanized sites, the results indicate that the streams maintain a diverse community, suggesting that most of them are in preserved conditions. O presente trabalho teve por objetivo caracterizar a estrutura trófica da comunidade de peixes de riachos da Serra do Japi, uma área de transição entre a Mata Atlântica e o interior paulista, no sudeste brasileiro. Os peixes foram coletados com equipamento de pesca elétrica em 15 pontos localizados em regiões com diferentes tipos de substrato e vegetação ripária, distribuídos pelas microbacias do Ribeirão Caguaçú, Caxambú, Piraí e Rio Guapeva, durante as estações chuvosa (janeiro/fevereiro) e seca (junho) de 2007. Os 589 indivíduos analisados, pertencentes a 22 espécies, foram classificados em diferentes grupos tróficos, discriminados através de uma matriz de similaridade baseada no Índice Alimentar (IA i ). Os resultados mostraram a formação de sete grupos com predomínio de espécies insetívoras e onívoras, seguidas pelas detritívoras, piscívoras, onívoro-carnívoras e herbívoras, que consumiram principalmente itens de origem autóctone com predomínio de algas e formas imaturas de insetos aquáticos. A Análise de Correspondência Canônica, ao correlacionar a biomassa dos grupos tróficos às variáveis ambientais, mostrou que as espécies onívoras, insetívoras e onívoro-carnívoras apresentaram ampla distribuição, enquanto que as detritívoras, herbívoras e piscívoras estiveram restritas a determinados locais, relacionados a diferentes variáveis físicas e químicas tais como nitrogênio total, condutividade e temperatura. Embora o aumento da biomassa de alguns grupos tróficos tenha sido verificado nos locais com maior influênc...

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Fishes from first order streams of lower Paranapanema and Ivaí rivers, upper Paraná River basin, Paraná, Brazil

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