Abstract
Abstract: In the present work, we conducted an extensive long-lasting inventory of the fishes, using different collection methodologies, covering almost the entire Pindaré River drainage, one of the principal tributaries of the Mearim River basin, an area included in the Amazônia Legal region, northeastern Brazil. We reported 101 species, just three of them being non-native, demonstrating that the composition of this studied fish community is majority composed of native species. We found a predominance of species of the orders Characiformes and Siluriformes, corroborating the pattern usually found for the Neotropical fish fauna. Similar to other studies, this inventory was mainly dominated by small characids, representing 21% of the species herein recorded. When comparing the present survey with other species lists published for this region (including the States of Maranhão and Piaui), we can conclude that the freshwater fish fauna of the State of Maranhão is probably still underestimated. We reported 41 more species, and one more species than Soares (2005, 2013) and Abreu et al. (2019) recorded for the entire Mearim River basin, respectively. We believe, however, that the number of species presented by Abreu et al. (2019) is overestimated. We compared our results with all other freshwater fish species inventories performed for the hydrological units Maranhão and Parnaíba sensu Hubbert & Renno (2006). With these comparisons, we concluded that our results evidenced that a high effort was put in the inventory here presented. The two works including more species recorded from coastal river basins of the hydrological units Maranhão and Parnaíba were the works published by Ramos et al. (2014) for the Parnaíba River basin, one of the main and larger river basin of Brazil, and the compiled data published by Castro & Dourado (2011) for the Mearim, Pindaré, Pericumã, and upper Turiaçu River drainages, including 146 and 109 species, respectively. Our survey recorded only 45 less species than Ramos et al. (2014), and eight less species than Castro & Dourado (2011). However, it is essential to emphasize that the number of species presented by Castro & Dourado (2011) is probably overestimated since they did not update and check the taxonomic status of the species of their compiled data. In several cases, they considered more than one name for the same species.
Highlights
The South America is the continent with the richest ichthyofauna of the world, with currently estimates of more than 9,100 species, about 27% of all the fishes around the world (Reis et al 2016)
The Amazonia biome, which occurs in the Neotropical region, extends across all countries in northern South America (Martins & Oliveira 2011, Van Der Sleen & Albert 2018, Val 2019), comprising an area of more than eight million km2 (Van Der Sleen & Albert 2018), with more than five million km2 belonging to Brazil (Val 2019)
In addition to the Amazon River basin, the Amazonia biome comprises other river basins and drainages (Van Der Sleen & Albert 2018, fig., 1), such as Orinoco River basin and Guiana shield basins, both located to the north of the biome region; and a series of coastal river basins and drainages in its eastern portion, after the mouth of the Amazon River, in the State of Pará, and in the west and center of the State of Maranhão; forming the Amazônia Legal area (Martins & Oliveira 2011, Van Der Sleen & Albert 2018)
Summary
The South America is the continent with the richest ichthyofauna of the world, with currently estimates of more than 9,100 species, about 27% of all the fishes around the world (including freshwater fishes and nearshore marine waters) (Reis et al 2016). The Amazonia biome, which occurs in the Neotropical region, extends across all countries in northern South America (Martins & Oliveira 2011, Van Der Sleen & Albert 2018, Val 2019), comprising an area of more than eight million km (Van Der Sleen & Albert 2018), with more than five million km belonging to Brazil (Val 2019). The biome is covered with dense tropical rainforests, being a large and important center for freshwater fish diversity, having more than 3,000 species (Van Der Sleen & Albert 2018). This high diversity is distributed in several aquatic ecosystems, such as large rivers, lakes, streams, floating vegetation, and beaches (Santos & Ferreira 1999). In addition to the Amazon River basin, the Amazonia biome comprises other river basins and drainages (Van Der Sleen & Albert 2018, fig., 1), such as Orinoco River basin and Guiana shield basins, both located to the north of the biome region; and a series of coastal river basins and drainages in its eastern portion, after the mouth of the Amazon River, in the State of Pará, and in the west and center of the State of Maranhão; forming the Amazônia Legal area (Martins & Oliveira 2011, Van Der Sleen & Albert 2018)
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