Estrutura trófica da ictiofauna do reservatório de Itaipu (Paraná-Brasil) nos primeiros anos de sua formação

Abstract

The Itaipu Reservoir, formed in November 1982, submerged an area of 1,460 square kilometers in a-151 km extension. Monthly collections from November 1983 to February 1989 were carried out in this environment with gill nets of different meshes. The aim of the research work was to evaluate the occupation process of the new environment with special regard to trophic structure. Combining different analytic methods the feeding habit of fish (69 species) was undertaken by examining stomachs preserved in 4% formaldehyde. Based on the predominant food in more than 50% of the diet of each species, nine trophic categories were established: planktivores, benthivores, aquatic insectivores, terrestrial insectivores, piscivores, omnivores, ileophagous, detritivores and herbivores. During the study period piscivores, aquatic insectivores, planktivores, benthivores and ileophagous species were the most important in number and biomass. Percentages among categories evaluated by Capture per Unit Effort (CPUE) showed relevant variations in different zones of the reservoir and years of collection. Benthivores and detritivores biomass was larger in the river area whereas planktivores, ileophagous, piscivores and terrestrial insectivores species biomass was larger in the lacustrine area of the reservoir. On the other hand, the number of aquatic insectivorous species increased during the years, whereas herbivores and piscivores species decreased in number.