Rio Arraial is a tributary within the Cubatão River basin, located along the southern coastal region of Paraná state in Brazil. Flowing through the Atlantic Rainforest, this stream is part of a richly biodiverse watershed that also includes the Cubatãozinho River, São João River, Guaratuba Bay, and the Guaricana and Vossoroca reservoirs. The river winds through lush Atlantic Rainforest terrain, making it a scenic and ecologically significant waterway. Its position within this globally recognized biodiversity hotspot means the surrounding riparian zone is characterized by dense tropical and subtropical forest cover, contributing to the stream's ecological health and the diversity of fish species it supports.