Spatial patterns in fish distributions and structure of the ichthyocenosis in the Agua Nanci stream, upper Parana River basin, Brazil

Samples of fishes were collected quarterly at three reaches in the Agua Nanci stream, upper Parana River basin, Brazil: near the spring, in the middle course, and near the mouth. Richness and evenness of the fish fauna increased between reaches towards the river mouth showing a correlation with stream width, pH and the presence of riparian vegetation. These variations in species richness and evenness, verified through Principal Component Analysis and Pearson correlation, suggest relations to habitat complexity, especially characterized by both the degree of preservation of dense riparian vegetation and high width at the lower reaches of the stream, providing a wide variety of hiding places for fish. Abundant species showed correlations with some environmental factors, suggesting habitat preferences.