The Rio Pacaás Novos is a significant river flowing through the state of Rondônia in western Brazil, where it serves as a tributary to the larger Mamoré River. The river and its surrounding headwaters are of considerable ecological importance, supporting unique biodiversity and forming part of the expansive Rio Madeira basin. A portion of its watershed is protected within the boundaries of the Pacaás Novos National Park, a transitional area characterized by mountainous terrain. While historically fishing activity was more concentrated at the river's mouth, the creation of a reservoir has led to more intensive fishing use throughout the system, raising important questions about the long-term sustainability of its fishery resources.