Fishes of the Vermelho River, São Lourenço River basin, Mato Grosso state, Brazil

We present a list of ichthyofauna of the Vermelho River, a tributary of the Sao Lourenco River, Paraguay basin. Fishes were caught with seine nets measuring approximately 10 m in total length and with a mesh size of 0.5 cm. We list 38 species, representing five orders, 11 families, eight sub-families and 28 genera. Characiformes were represented by 23 species, Siluriformes by 11, Perciformes by two, and Gymnotiformes and Pleuronectiformes by a single species each.


Introduction
The Pantanal Mato-grossense is a vast sedimentary floodplain located in the midwest region of Brazil (Britski, et al., 2007). In this floodplain, tributaries of the Paraguay River, which drains the system, are environments that fluctuate seasonally and determine the seasonal changes in food and movement of fish that occupy the lower parts of the floodplain. The Vermelho River starts at Poxoréu city (Mato Grosso State) and it is the main left margin tributary of the São Lourenço River which in turn flows into the northeastern edge of the Pantanal. In recent decades this river has suffered from the constant removal of riparian vegetation causing silting and gradual decrease of the flow of its waters. The Vermelho River is located near the city of Rondonópolis (Mato Grosso State), but it also drains other municipalities.
The number of valid species of fishes in general is over 32,000 (Eschmeyer, 2012). According to Reis et al.

Abstract:
We present a list of ichthyofauna of the Vermelho River, a tributary of the São Lourenço River, Paraguay basin. Fishes were caught with seine nets measuring approximately 10 m in total length and with a mesh size of 0.5 cm. We list 38 species, representing five orders, 11 families, eight sub-families and 28 genera. Characiformes were represented by 23 species, Siluriformes by 11, Perciformes by two, and Gymnotiformes and Pleuronectiformes by a single species each.  stretch of Vermelho River between 16º25'/16º30'S and 54º40'20"/54º34'50"W ( Figure 1). The predominant climate in the region is Aw (Köppen Climate Classification System) which is characterized by warm wet summers and dry winters with mean annual temperatures exceeding 25.0ºC. Precipitation varies between less than 60 mm to 1,566 mm in the region (Orioli et al., 1982).
In littoral areas of river, fish species were collected with 10 m long seine nets (0.5 cm mesh size) during the day. The specimens were preserved in formalin (10%). The sampling work was standardized to a constant time and number of drags employed (two) at each point. Fishes were collected under ICMBio (Instituto Chico Mendes de Conservação da Biodiversidade) permits (21546-1/2009).
In the laboratory, fishes were identified up to the lowest possible taxonomic level. Identification was initially performed using the identification keys of Britski et al. (2007) and later confirmed by experts.
Voucher are deposited in the fish collections of the Laboratório de Zoologia (LZCUR) of the Universidade Federal de Mato Grosso -campus Rondonópolis and Núcleo de Pesquisas em Limnologia, Ictiologia e Aquicultura of the Universidade Estadual de Maringá (NUP).
The results obtained in this study, with a total of 38 fish species captured, are very modest when compared to surveys presented by Britski et al. (2007), who registered 269 fish species for the Pantanal region, suggesting the need for an increased sampling effort and more detailed taxonomic studies in rivers that form the Pantanal.
However, our results are useful for studies about the distribution of ichthyofauna in tributaries of the Paraguay basin. Future studies with other capture methods must be employed to obtain additional other species to the presented list.