The Rio Iguaçu is one of South America's most significant river systems, stretching approximately 1,320 kilometers (820 miles) through the state of Paraná, Brazil, before joining the Paraná River near Foz do Iguaçu. Its name derives from the Guarani words y guasú, meaning "big water" — an apt description for a river that drains a basin of roughly 62,000 square kilometers. Rising in the Serra do Mar near Curitiba at an elevation of around 1,200 meters (3,900 feet) above sea level, the river descends dramatically westward, dropping to approximately 110 meters at its mouth. This elevation gradient gives the river tremendous energy and variety, culminating in the world-famous Iguazu Falls before its confluence with the Paraná. The Iguaçu basin is recognized as a distinct fish ecoregion of exceptional biological significance, harboring an extraordinary concentration of endemic ichthyofauna found nowhere else on Earth. For anglers, this means fishing in a system unlike any other — one where native species have evolved in relative isolation and where the river's character shifts dramatically from its mountain headwaters to its broad lower reaches.