Influence of environmental variables and anthropogenic perturbations on stream fish assemblages, Upper Parana River, Central Brazil

The Ouvidor River, a tributary of the Upper Parana River, drains areas covered by cerrado vegetation in Central Brazil. We collected data for environmental variables (water temperature, dissolved oxygen, pH, conductivity, turbidity, water velocity, luminosity, channel substrate and width) and anthropogenic perturbations (industry, reservoirs, urban areas) that may structure the fish assemblage in ten stream sites of the Ouvidor River basin. In each stream we delimited one 50 m long site where fish were captured by electrofishing and abiotic data were collected every two month between August 2004 and June 2005. Co-inertia analysis indicated that pH, water velocity, channel width and water temperature most strongly structured the fish assemblages. The interactions of water velocity and channel width with the fish assemblage were not directly affected by wet and dry seasons but the opposite was true for pH and water temperature.