Few studies have been published on the taxonomy, biology and ecology of the fish fauna of the rivers and reservoirs from the Brazilian Caatinga. Considering the importance of fish surveys as subsidies for future studies and fishing resources management, the purpose of the present study was to assess the fish assemblage of the two largest reservoirs in the middle Acaraú river basin, the Paulo Sarasate and the Edson Queiroz reservoirs, state of Ceará, Northeastern Brazil. Eight nycthemeral samplings were performed with gillnets (mesh size ranging from 3 to 12 cm between opposite knots) during rainy and dry season between 2010 and 2012. We captured 1,626 specimens belonging to three orders, nine families and 17 species, six of which are endemic to the Caatinga. Approximately 30% of the species observed were non-native and had been introduced for stocking purposes.