Spatial Patterns in Fish Assemblages of Ilha Grande National Park, Brazil

The aim of this study was to characterize spatial trends in composition and structure of the fish assemblages in Ilha Grande National Park, located on the Upper Paraná River. Fish were caught bimonthly between October 2001 and August 2002 with gillnets of different mesh sizes at 10 sampling sites. Over the course of the study, 9,858 fish were collected, representing 74 species; 63 species were recorded in tributaries, 59 in the main channel of the Paraná River, 48 in connected lagoons, and 38 in disconnected lagoons. Species richness, diversity, and evenness did not differ significantly, but composition and structure of the fish assemblages were significantly different among biotopes. There was no relationship between limnological variables and composition and structure of the fish assemblages in the biotopes studied. Species abundance (measured in number and biomass) was higher in lagoons compared with the other biotopes. The observed spatial variation in fish assemblages may be related to the dams situated upstream and downstream of Ilha Grande National Park. The spatial patterns in composition and structure of fish assemblages described here should be taken into account in the formulation of strategies for the management and conservation of Ilha Grande National Park.