Fish assemblages in the Upper Paraná River floodplain

Abstract

We aimed to characterize the composition of the fish assemblages and identify possible indicator species in the four main biotopes (i.e. rivers, channels, connected lagoons, and disconnected lagoons) of the Upper Paraná River floodplain. Quarterly samples were taken from February 2000 to August 2002. A total of 107 species belonging to 27 families were recorded. Gillnetting captured 91 species whereas seining captured 68. In all, 79 species were captured in rivers, 61 in channels, 74 in connected lagoons, and 91 in disconnected lagoons. Among the species with the highest numerical abundances was L. platymetopon, A. altiparanae, S. marginatus and S. notomelas. Results of an ordination and the index of indicator species revealed that each biotope in the Upper Paraná River floodplain, except the river, shared a roll of common species. In rivers, however, there was an absence species with commercial importance. Several species were indicators of biotopes and have fewer ecological restrictions and diverse feeding habits and reproductive strategies. A higher number of indicator species in rivers may be a result of the higher heterogeneity of the species composition among subsystems, mainly between the Paraná River and its tributaries (Baia and Ivinheima Rivers).