The Río Iguazú flows through the lush subtropical rainforest of Misiones Province in northeastern Argentina, forming part of the border between Argentina and Brazil before ultimately joining the Paraná River. This remarkable river system winds through one of South America's most biodiverse regions, where the Atlantic Forest — now reduced to less than 8% of its original extent — still shelters jaguars, tapirs, and black capuchin monkeys along its banks. The river is perhaps best known internationally for the spectacular Iguazú Falls, but for anglers, it represents something equally extraordinary: a richly diverse fishery with roughly 100 native fish species, approximately 70% of which are endemic to the river system. The falls themselves serve as a natural biological barrier, creating distinct fish communities above and below, and giving rise to a remarkable concentration of rheophilic (fast-water-adapted) species found nowhere else on Earth. Fishing excursions typically depart from a pier in Puerto Iguazú, where guides lead anglers not only to productive fishing spots but also to remote corners of the Misiones jungle accessible only by river.