Each of the Cerrado watersheds has its own ichthyological fauna. The distribution patterns of ichthyological species are related to physical and biotic factors that act at different levels of scale, segment and habitats of rivers within each watershed. However, the knowledge on the river basins ichthyofauna of Cerrado is quite discrepant, with the Parnaíba river basin the least well known. Although the main channel of each river basin and its tributaries have been fairly listed, the small rivers and smaller tributaries are still scarcely known.
The Araguaia-Tocantins basin that is the richest in species, while the Rio São Francisco presents the average richness and Parnaíba is relatively poor, when considering the current state of knowledge. The richness of species in each Cerrado basin varies from 350 species in the Araguaia-Tocantins basin, 153 in São Francisco river and 95 in Parnaíba river. In order of importance stands out the Charadriiformes (catfish), present in all the watersheds of the target area. The presence of endemism within each river basin involves the presence of geographical barriers such as waterfalls that separate the great river section or positioning of the fauna in the water body, whether rising or mouth. Besides these conditions, there are still endemism related to fish that live in temporary ponds, thus very vulnerable to changes in environment (RIBEIRO, 2007).
