Observation of an invasion of the piranha <em>Serrasalmus marginatus</em> Valenciennes, 1847 (Osteichthyes, Serrasalmidae) into the Upper Paraná River, Brazil

Abstract

The building of Itaipu Dam, 150 km downstream from Sete Quedas Falls, resulted in the natural geographical barrier drowning, with subsequent mixing of the fish faunas. Serrasalmus marginatus (Osteichthyes, Serrasalmidae), a species that had been restricted to the river segment downstream from Sete Quedas, invaded the Upper Paraná River. The catching of Serrasalmus spilopleura, a resident species, decreased drastically after the invasion, contrary to S. marginatus, which increased in abundance. In the Piquiri River, where the latter species does not occur, the abundance of S. spilopleura remained high, due to the presence of Nhá Bárbara and Apertado Falls.