Fish diversity in the rivers that drain the Baixada Maranhense and the Mearim basin in northeastern Brazil

Abstract

The Baixada Maranhense Environmental Protection Area of the Brazilian state of Maranhão encompasses a biologically rich region that includes the basins of four principal rivers, the Mearim, Pericumã, Pindaré, and Turiaçu, which form a complex of wetlands. The present study provides a comprehensive inventory of the fish fauna of the rivers that drain the Baixada Maranhense based on the identification of voucher specimens that were deposited in a scientific collection. Expeditions were conducted between 2014 and 2020. The inventory identified a total of 100 fish species representing 79 genera, 34 families, and 11 orders, which are found in both freshwater and estuarine environments. Six (Potamotrygon orbignyi, Leporinus piau, Moenkhausia loweae, Serrasalmus spilopleura, Pachypops fourcroi and Peckoltia greedoi) of the 100 taxa identified here are considered to be new records for one or more of the basins surveyed during this study, based on the existing data, while four – Colossoma macropomum, Megaleporinus macrocephalus, Cichla sp. and Cichla kelberi – are not native. The most speciose orders were the Siluriformes and Characiformes, while the most diverse families were the Loricariidae, Characidae, Auchenipteridae, Cichlidae, and Serrasalmidae. These data are consistent with the findings of most of the previous studies of freshwater ecosystems in the Neotropical region, in particular those of the rivers of Maranhão. The results of the present study represent an important advance in the understanding of the diversity of the fish fauna of the Mearim, Pericumã, Pindaré, and Turiaçu rivers, which are still poorly studied, and have likely had their diversity underestimated up to now.

Molecular Evidence Reveals Taxonomic Uncertainties and Cryptic Diversity in the Neotropical Catfish of the Genus Pimelodus (Siluriformes: Pimelodidae)

“…However, a greater sampling effort and a more detailed study would be necessary to better understand this scenario. Some cases of species being introduced into the hydrographic basins of Maranhão have been reported [ 24 , 89 , 91 ]. In the present study, four specimens were collected from the Preto River, in the municipality of São Benedito do Rio Preto, in the state of Maranhão, which corresponds to one of the localities sampled by Vieira et al [ 91 ], in the most comprehensive survey ever conducted of the basin of the Munim River.…”

“…A recent study of Pimelodus , based on the use of molecular markers, confirmed the existence of two independent evolutionary lineages from the trans-Andean region, which were described as new species [ 23 ]. Studies of this type are still limited in the Brazilian Northeast, however, and most of the Pimelodus taxa known to occur in the hydrographic basins of the state of Maranhão have been catalogued based solely on classical taxonomic criteria [ 24 ]. In addition, given the confused taxonomy of the genus, the nomen P. blochii , for example, has been attributed arbitrarily to many types of long-whiskered catfish from different localities in the Amazon basin, which likely represent more than one species [ 25 ].…”