Ocorrência e ecologia trófica de quatro espécies de Astyanax (Characidae) em diferentes rios da bacia do rio Tibagi, Paraná, Brasil

Abstract

ABSTRACT. Occurrence and trophic ecology of four species of Astyanax (Characidae) in different rivers of the Tibagi River Basin, Paraná, Brazil. Stretches of the Rivers Fortaleza, Iapó and Tibagi were monthly sampled with gillnets of different mesh sizes and castnets from May 2001 to April 2002 in the Tibagi River basin. Specimens of four species of the Astyanax genera were captured. In order to assess how they use habitat and food resources in the different rivers, their constancy was calculated and the number of specimens was compared by using the Bray-Curtis similarity analysis. The composition (percentage) of food items consumed was ordered by using the Principal Components Analysis (PCA). The proportion of different food items in the diet was assessed and classified according to type (animal or plant material) and origin (allochtonous or autochtonous). The low similarity and constancy showed differences in the type of habitat preferred by the four fish species. Astyanax altiparanae Garutti & Britski, 2000 and A. fasciatus (Cuvier, 1819) were present in the large rivers but were constant only in the Tibagi River. Astyanax eigenmanniorum (Cope, 1894) was present in all rivers but prefers habitats in the mouth of affluents of large rivers. Astyanax scabripinnis (Jenyns, 1842) was restricted to Fortaleza River, a small Tibagi River affluent. The number of food items consumed by the different species varied from 11 to 23. Among the main food, three items were common for the four species: 1-plant residuals (leaves and seeds from the earth community of plants), 2-insect residuals (from different origins and unidentified) and 3-aquatic vegetation. So plants and insects were the main food consumed by all the species. Astyanax eigenmanniorum showed the highest distinction in the diet composition among the species studied. Such distinction was due to its ability of exploring an abundant food resource: the aquatic plants that were consumed together with portions of coal/sediments near the rocky shores at the Iapó River. The similarity of the origin and type of food consumed by the four species and the differences in terms of the habitat occupied may explain why one species is abundant and constant in only one of the river stretches studied. KEYWORDS. Astyanax, trophic ecology, Tibagi River Basin, rivers.RESUMO. Na bacia do rio Tibagi, trechos dos rios Fortaleza, Iapó e Tibagi foram amostrados mensalmente, de maio de 2001 a abril de 2002, com tarrafas e redes de espera de diferentes malhagens. Foram capturados indivíduos de quatro espécies de Astyanax. Para conhecer como essas espécies utilizam o hábitat desses rios, foi calculada a constância, e as freqüências em número de exemplares foram comparadas pela análise de similaridade Bray-Curtis. A composição percentual dos alimentos consumidos foi ordenada usandose a Análise de Componentes Principais (ACP). As proporções dos recursos alimentares foram avaliadas e classificadas quanto à natureza (animal ou material vegetal) e origem (alóctone e autóctone). A constância e ...

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