Composição da Ictiofauna de quatro trechos de diferentes ordens do Rio Capivara, Bacia do Tietê, Botucatu, São Paulo

Sanches Uieda, VirginiaGalvão Barretto, Marluce

The present work aims at characterizing the ichthyofauna of the Capivara River, the most important tributary of the left margin of Middle Tietê River Basin (State of São Paulo, Brazil), in four sections: one of firstorder, one of third-order and two of fourth-order. The first two sections are located on the top of the Cuesta (~900 m of altitude) while the two others are in the Peripheric Depression (~600 m of altitude). Twenty six fish species were sampled in the river. The addition process was found to have a broader magnitude than the substitution process along the river. The sections at the Peripheric Depression presented high diversity indexes, low dominance values and uniform distribution among individuals of each species, these factors been related to an increase in habitat heterogeneity and reduction of environmental fluctuation. An oppositesituation was observed in the Cuesta sections, probablyrelated to their irregular topography and anthropicactivities. Such factors highly stresses the communityand brings about the low species diversity with a highdominance curve.