Itaipu reservoir (Brazil): impacts of the impoundment on the fish fauna and fisheries

Abstract

Changes in the fish fauna of Itaipu reservoir following completion in 1982 are described. Of 113 species identified prior to inundation, only 83 were caught after impoundment. Fish species diversity increased (1985-86) initially but declined thereafter. The predominance of Characiformes and Siluriformes found before impoundment was maintained in the reservoir. Of the species abundant in the river, only Plagioscion squamosissimus, a piscivore introduced in 1968, remained among the most abundant in the reservoir fishery. The planktivore Hypophthalmus edentatus and the insectivore Auchenipterus nuchalis, both sporadic in the catch before inundation, were prolific in the catches from the reservoir. The Parana basin has five species of Siluriformes with internal fertilization and three of them were among the seven most frequent in the reservoir. Any proposed reservoir management for the future will depend on future construction of reservoirs upstream of Itaipu.