This report presents the assessment of Patagonian Shelf and associated river basins. The report focuses on the La Plata River Basin, the second largest watershed in South America, and the South Atlantic Drainage System, comprising basins that drain large arid areas of Argentina and one of the world's largest continental shelves. Pollution in the La Plata River Basin has caused considerable environmental degradation while fishing has changed marine habitats and communities. The root causes of environmental degradation in the Argentinean and Uruguayan Common Fishing Zone and the Uruguay River Basin, shared by Argentina, Brazil and Uruguay, are identified and potential remedial policy options are presented