Variação espacial na estrutura das assembléias de peixes da planície de inundação do alto rio Paraná, Brasil.

Abstract

Spatial variation on fish assemblages structure of the upper Paraná River floodplain, Brazil. Although the upper Paraná River floodplain is subjected to impacts produced by hydroelectric plants upstream, fish assemblages studies acknowledge its importance in the maintenance of regional biodiversity. Fish assemblages of four categories of biotopes belonging to three subsystems were analyzed. The aim was analyse the spatial variation in the structure and to identify processes responsable to species composition and abundance. Quarterly samples were carried out with gill nets in 19 sites during the year 2000. The sites comprised rivers, channels, connected and disconnected lagoons in the subsystem Paraná and two tributaries, the Baía and Ivinheima Rivers. Connected lagoons showed greater species richness and similar species composition. There were not detected significant differences in diversity and in eveness among categories of biotopes and subsystems. Dominance pattern is achieved by species whose life strategies allow to take advantages of the intensity, duration and frequency changes of the flood pulses. Biotic (predation) and abiotic (local processes) factors explained satisfactorily the assemblages structure