Structure of the ichthyofauna of adventitious streams in the South Pantanal area (Alto Taquari River basin, MS, Brazil)

Virginia Sanches Uieda, César Yuji Fujihara

Resumo


For the Taquari River, one of the main tributaries of the South Pantanal, the ichthyofauna has been studied since the 1970s in rivers, streams and lagoons, but not in adventitious streams. Those are defined as small tributaries that flow directly into large rivers, with at least three orders of magnitude. The aim was to analyze and compare spatially and seasonally the structure of the ichthyofauna of five adventitious streams of the Upper Taquari River. Thirty-seven species were collected, from which 22 are species with wide distribution in the Upper Paraguay Basin and only Ituglanis eichorniarum was cited for the first time for this basin. The deterministic co-occurrence pattern, obtained by the C-score analysis, confirmed the existence of spatial variation in the ichthyofauna structure of the streams sampled, with higher similarity between streams with greater proximity, interpreted in function of the mobility of the species and opportunism in the exploration of the streams. Although the Taquari River presents a set of rapids and a small waterfall between the mouths of those streams, they do not appear to form significant barriers for most fish species in the region, and similarity patterns were related to the distance between the streams and to the conservation conditions of the environments. The stream with higher values of diversity and equitability presented greater size, and the diversity of the ichthyofauna could be indicative of greater environmental stability and habitat diversity. On the other hand, the stream with reduction in the riparian forest and proximity to urban area presented the lowest diversity. For most streams, there was seasonal similarity in composition, but greater richness, abundance and dominance of species in the dry season. The increase of the current in the rainy season should promote large drag of the sandy substrate, leading to a homogenization and less availability of microhabitats. The small size of these adventitious systems should serve as protection against large predators and, in addition, their greater heterogeneity of habitats and the presence of riparian vegetation should offer shelter and food supply for small species.




Iheringia Série Zoologia

Museu de Ciências Naturais, Fundação Zoobotânica do Rio Grande do Sul

Rua Dr. Salvador França, 1427, 90690-000 Porto Alegre, RS, Brasil

E-mail: iheringia-zoo@fzb.rs.gov.br