Rio Petorca flows through the Valparaíso Region of Chile, draining a watershed that spans roughly 2,800 square kilometers before reaching the Pacific coast. The river originates in the Andean foothills and descends through a Mediterranean-climate landscape characterized by dry summers and wet winters — a pattern that profoundly shapes both water levels and fish behavior throughout the year. The river's lower reaches and estuary zone represent a dynamic transition environment where freshwater and marine influences converge, creating a diverse ecological setting for anglers. The watershed sits within Chile's central Mediterranean zone, a biogeographically significant area that supports a mix of native, endemic, and introduced fish species.