The Rio Preto, also known as Igarapé Preto, is a significant watercourse in the municipality of Cruzeiro do Sul, Acre, Brazil. As a tributary within the vast Amazonian basin, it represents a classic lowland tropical stream environment, characterized by its connection to the Juruá River system. The river flows through a region of rich biodiversity, where the aquatic ecosystem supports a distinct community of fish species adapted to the warm, often turbid waters typical of this part of the Amazon rainforest. Its ecological importance is underscored by scientific studies focused on documenting its ichthyofauna, providing a foundational understanding for both conservation and recreational angling pursuits in this remote and biologically rich area.