The characterization of the limnological variables and of the fish fauna of a open lake and of the main channel in the Rio das Mortes floodplain was conducted in order to compare these environments and indicate the influencing environmental factors of the fish communities in each one of them. A significative difference was observed between the open lake and the river channel in relation to the water transparency, higher in the open lake, and water velocity, higher in the river channel. Species diversity was also different between the sites, with significantly higher value in the open lake. In both envitonments the highest richness and diversity values were obtained during the low water period, and the relative density (CPUE) values in the rising water period. The environments were more similar during the wet season, in relation to both fish abundance and limnological characteristics. This happens due to the homogeneization of the water and habitat structure caused by flooding. The results indicate that the flood pulse, associated with water velocity, was the major driving force for the fish fauna structure in the environments sampled in this study.
Diversity; flood pulse; limnology; similarity
