Influence of hydrological changes on the fish community in two lotic environments of the Middle Parana Floodplain, Argentina

Temporal variations of fish abundance and species richness in two sites of a secondary channel of the Middle Parana Floodplain (Argentina) have been analyzed from 2010 to 2012. Relationships of these ecological attributes with alternations of floods and dry periods were appraised. Permutational analyses of variance were applied to determine significance in temporal changes of the fish community, taking into account catch per unit effort and species richness of the whole community, by groups of distinct reproductive strategy and considering fish sizes. The results reveal significant differences in structure and composition of fish assemblages at distinct stages of the hydrological regime. Those temporal differences are associated with changes in timing, duration, and magnitude of floods since the three groups have shown distinct responses to the hydrological variations. Long-distance migrants depend on major inundations for a successful reproduction, short-distance migrants seem to have distinct responses to floods according to the kind of species, and sedentary fish-developing parental care essentially needs high floodplain connectivity for juvenile development.