Abstract
Abstract: The ichthyofauna of streams in the Neotropical region is not yet fully known. This study aims to investigate the ichthyofauna composition of six streams of the Ijuí River sub-basin, Rio Grande do Sul State, inserted in the Uruguay River basin, as to contribute to the knowledge of fishes species richness and distribution in the south of Brazil. Sampling was carried out between July 2015 and May 2016, bimonthly, using the technique of electric fishing to collect the fishes. Spatial variations (per sampled stream) in the ichthyofauna composition were tested with a permutational multivariate analysis of variance. In total, we collected 5,029 individuals from 55 species, 13 families and five orders. From these species, 17 are endemic to the Uruguay River basin. Five species alone represented approximately 70% of the ichthyofauna abundance sampled. Our hypothesis that the fish community composition is not homogeneous along the streams sampled was confirmed and we observed that species complexity increases from the upstream closest area to the downstream according to the river continuum concept.
Highlights
The ichthyofauna of the Neotropical region comprises 4,475 valid species, and perhaps more than 1,550 undescribed ones (Reis 2013)
This study aims, to evaluate the composition of the fishes community and the pattern of species distribution in streams located along a longitudinal gradient in the hydrographic sub-basin of the Ijuí River, tributary of Uruguay River, intending to contribute to the knowledge of the richness and abundance of species in this region of the south of Brazil
The species richness found in the streams of the Ijuí River sub-basin follows the pattern of freshwater fishes in the Neotropical region, with Characiformes and Siluriformes as the richest orders in number of species (Lowe-McConnell 1999, Malabarba & Malabarba 2014)
Summary
The ichthyofauna of the Neotropical region comprises 4,475 valid species, and perhaps more than 1,550 undescribed ones (Reis 2013). Among the habitats occupied by the ichthyofauna, streams are known as lotic environments, with unidirectional water flows from headwaters to mouth and may have non-persistent flooding areas during rainy seasons (Esteves & Aranha 1999, Uieda & Castro 1999). They are known to have a wide variety of mesohabitats due to environmental gradients ranging from rocky riffles and runs to sandy pools and backwaters, in addition to a variety of marginal vegetation in the stream bank (Araújo-Lima et al 1995, Esteves & Aranha 1999). In southern and southeastern Brazil, the streams may present high dissolved oxygen concentration and large seasonal temperature variation, with influence of drainage basin geomorphology under abiotic components as transparency, pH and conductivity (Araújo-Lima et al 1995, Esteves & Aranha 1999)
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