Composition and distribution of fish assemblages in a tropical river–estuarine continuum

The damming in a watershed alters all its fluvial dynamics, affecting the patterns of occurrence and distribution of the fish community. Despite being an important refuge for fish communities in tropical Brazil, the river–estuarine continuum is strongly affected by human activities that have considerably disturbed the natural dynamics. In this study, our objective was to evaluate the spatial and seasonal composition of the fish community in three distinct regions along the river–estuarine continuum of the São Francisco River, raising the hypothesis that the seasonal effect does not interfere in the structuring of the fish assemblage. Our results demonstrate that seasonality does not influence the composition and distribution of fish species in the lower São Francisco, this differentiation is due to the spatial effect of the regions studied. These findings add to the available knowledge about the absence of the seasonal effect in highly dammed environments.