A the distribution and structure of fish assemblages in a river suffering anthropogenic influences, located in the upper Paraná River basin - Central Brazil

Abstract

This study aims to compare the differences between the assemblages of fish considering the abundance, richness, the Shannon-Wiener diversity Index and constancy, to determine the quality of the aquatic environment taking into account the relation biomass/abundance. The Samples were obtained in five stretches (1.000 m) located along the main channel of the Meia Ponte River, between March 2006 and February 2007. Fish were captured using four set of nets (meshes 12, 15, 20, 25, 30, 35, 50 and 70 mm) and five minnow-traps. It was collected 2.736 individuals distributed in 64 species. The results show that the pattern of the number of constant species along the channel river contrasts with those of the accessory and occasional species. Significant differences between stretches are observed considering the abundance, richness and Shannon-Wiener diversity Index. The cluster analysis indicates that the fish assemblages of the stretches 1, 2 and 3 are different from those downstream the hydroelectric reservoir of Rochedo (stretches 4 and 5). The ABC curves suggests that upper stream stretches (1 to 3) are less polluted than those (4 and 5) downstream the Rochedo reservoir. Anthropogenic impacts influence on the results obtained.