Factors determining the structure of fish communities in Pantanal lagoons (MS, Brazil)

The fish communities of lagoons in the Nhecolandia Pantanal were studied to determine the factors which are responsible for the composition and abunda nce of species. Fishes were collected in 19 lagoons during August 1997, aft er their isolation from the River Negro, using beach seines (15 x 1.5 m; 2 mm mesh). A total of 51 species were collected. In the lagoons, or in parts with dense macrophytes, a screened box trap was used. Fishing was also acc omplished with hooks of several sizes. Species richness was estimated by th e jack-knife procedure, after adjustment to the log-normal distribution and with von Bertalanffy's equation (asymptotic). The most important factors i n the community organization were macrophyte cover, piscivore abundance and depth of the lagoons. The role of these habitats in the Pantanal ecosystem was discussed.