Influence of the hydrological level on an assemblage of fishes at a seasonally isolated lagoon of the Upper Paraná River floodplain

Abstract

The purpose of this paper was to assess the effect of different hydrological periods on the structure of a fish assemblage at Canal do Meio Lagoon (Upper Paraná River floodplain), taking into account richness, diversity, equitability, density and standing crop. Specific density was estimated in years with different hydrological regimes, by using the Zippin maximum likelihood method. The first year analyzed, 1996, was characterized by low water levels, short inundation period and interrupted floods. In 1998, the opposite was observed. The differences in the fish assemblages was attributed to these differences in hydrological regimes. Species richness, overall density and, specially, the density of migratory fishes was lower in 1996. These results demonstrate the importance of uninterrupted and long floods (as observed in 1998) to the conservation of fish biodiversity in floodplain ecosystems.