Diversity of fish species in the River Paranapanema Jurumirim Reservoir transition region (Sao Paulo, Brazil)

The diversity of fish species in an transition zone between the River Paran apanema and the head mouth of the Jurumirim Reservoir was evaluated. Fish s amples were collected from October 1995 to September 1996, by experimental fishing (gill-nets and sieve), in three marginal shallow lagoons and two ch annel river zones, Gill-net collections resulted in 21 taxons of native fis hes. Detritivorous Characiformes such as Steindachnerina insculpta were pre dominant Sieve collections resulted in 31 taxa and the Tetragonopterinae su bfamily was the most representative group, which included small species as Cheirodon stenodon. The equitability index characterized the high heterogen eity of fish numeric abundance, reflecting the dominance of a few groups. A significant relationship between biotic and abiotic variables was indicate d by the first canonical function. In comparison with other regions of the drainage basin, the ecotone zone studied indicated a higher species richnes s and, in the case of some species, fishes in all stages of development. Th is study demonstrated the necessity to preserve the ecological zone for the fishing and fishery management in the reservoir.