Inventário da ictiofauna da bacia do rio Munim, Maranhão, Nordeste do Brasil

Abstract

The Neotropical region, which comprises the region from South America to southern Mexico, comprises a great variety of habitats, in addition to a very diverse fauna and flora, comprising 7 of the 35 world's hotspots. This region posses a huge freshwater fish species richness species, with more than 6,000 valid species and with estimates of 8,000 to 9,000 species (including undescribed species). Brazil, the largest country in the Neotropical region, stands out for its freshwater fish diversity, with more than 2,500 described species. This great diversity is mainly composed of small and medium-sized fish, which are distributed in different aquatic environments (rivers, streams, streams, lakes, swamps, and others). However, even though Brazil has a rich native fish diversity, in recent decades, non-native species have been introduced, more and more frequently, into Brazilian freshwater systems. These introductions come from different human activities, such as: aquaculture, intentional introductions and releases, aquarium trade, mosquito larvae biological control interventions, transposition of water between isolated river basins, sport fishing, amongst other activities. The state of Maranhão has an extensive hydrographic network, which includes the following freshwater systems: Gurupi, Maracaçumé, Turiaçu, Pericumã, Mearim, Itapecuru, Munim, Periá, Preguiças, Parnaíba, in addition to other smaller isolated coastal rivers, and parts of the lower and middle Tocantins River. This fact makes the state extremely relevant for taxonomic, ecological and conservation studies of freshwater organisms. Therefore, this work carried out an inventory, based on data from 12 years of collection, and 84 sampled locations, of fish species that occur in the Munim River basin, Maranhão, Northeastern Brazil. A total of 123 species were recorded, two of them are non-native species. This study increased the number of known species for the Munim River basins to 64 species, when compared to previously published studies. The Munim River basin was subdivided into 4 sections (upper, middle, lower and estuary), and the diversity of these sections was compared. The middle and lower sections had the most similar diversities, while the estuary section had the greatest difference between the diversities of the other sections.