Spatial variation of the fish assemblage structure from the upper Rio Paraná floodplain, Brazil, in a dry year

PETRY¹, A.C., AGOSTINHO², A.A. & GOMES², L.C.

¹ Programa de Pós-Graduação em Ecologia de Ambientes Aquáticos Continentais

² Departamento de Biologia, Nupélia, Universidade Estadual de Maringá, Av. Colombo, 5790, CEP 87020-900, Maringá, PR, Brazil, e-mail:anapetry@bol.com.br; agostinhoaa@nupelia.uem.br; lcgomes@nupelia.uem.br

ABSTRACT: Although the upper Rio Paraná floodplain is subjected to impacts generated by hydroelectric plants upstream, studies on fish assemblage reveal its importance to the maintenance of regional biodiversity. The purpose of this study was to analyze the spatial variation in the structure of fish assemblage and to identify processes determining species composition and abundance. Quarterly samples were taken with gill nets in 19 sites during the year 2000. Fish assemblage of three subsystems (Rio Paraná and two tributaries, Baía and Ivinheima) and four categories of biotopes (rivers, channels, connected and disconnected lagoons) were analyzed. No significant differences in richness, diversity and evenness were detected among subsystems and biotopes, in spite of the significant differences detected in abiotic factors among subsystems. On a broad spatial scale, fish assemblage structure of the upper Rio Paraná floodplain was characterized by the dominance of few typical species, unevenly distributed, and influenced by abiotic factors, such as water transparency, dissolved oxygen and pH.

Key-words: neotropical fish; floodplain; fish assemblage structure; abiotic factors.