Rio Cubatãozinho is a significant tributary of the Cubatão River basin, flowing through the Atlantic Rainforest region of Paraná, Brazil. The river originates in the first plateau of Paraná state, in the municipality of São José dos Pinhais, near the Guaricana Reservoir (approximately 25°40'S, 48°40'W), and ultimately drains toward the Guaratuba Bay on the southern Atlantic coast of Paraná. This river system is embedded within one of the most biodiverse biomes on the planet — the Atlantic Rainforest — and supports a rich and varied assemblage of native fish species. The basin includes several notable tributaries and associated water bodies, including the Arraial, São João, Castelhanos, Canavieiras, and do Meio rivers, as well as the Vossoroca Reservoir, all of which contribute to the ecological complexity and fishing opportunities of the broader watershed.