This study aims to describe the fish assemblage using ecological descriptors (richness, abundance, diversity of Shannon-Wiener, uniformity, relation richness/abundance and constancy. Fish sampling were carried out every two month from August 2004 to June 2005 in a stretch of 50 m long in nine tributaries and in the main channel of the Ribeirão Ouvidor. Four thousand forty-nine fish were collected using electric fishing equipment. These individuals are distributed in 35 species, six Orders and fourteen families. The most abundant species were Astyanax cf. fasciatus Cuvier, 1819 (762 individuals), Poecilia reticulata Peters, 1859 (725) and Astyanax altiparanae Garutti & Britski, 2000 (650). The correlation between the channel width and the richness suggests that width streams has greatest richness that those with narrow channels. Only the diversity of Shannon-Wiener showed significant differences among streams. Astyanax cf. fasciatus and Rhamdia quelen Quoy & Gaimard, 1824 were present in all the streams sampled, whereas the greatest number of constant species was found in the Santo Antonio stream.
Central Brazil; ecological descriptors; neotropical fish; Paranaíba river system
