Rio Itapecuru is one of the significant river systems flowing through the state of Maranhão in northeastern Brazil, draining a basin that sits within one of the most ecologically diverse regions of the country. The river traverses a landscape where two of Brazil's major biomes — the Amazon and the Cerrado — converge, along with extensive biome transition zones that make the region exceptionally rich in terms of freshwater biodiversity. The Itapecuru basin ranks as the fourth most species-diverse freshwater system in Maranhão, trailing only the Mearim, Tocantins, and Parnaíba river basins, and it supports a remarkable assemblage of native fish species that reflects the ecological complexity of this transitional environment. DNA barcoding studies have confirmed high levels of genetic diversity among the fishes of the Itapecuru basin, underscoring its importance as a freshwater habitat and making it a compelling destination for anglers interested in exploring the native ichthyofauna of northeastern Brazil.