There are few abundance estimates available for any significant portion of the range (Brownell and Cipriano, 1999). The total number of dusky dolphins in the one area off the Patagonian cost was estimated to be close to 7,252 individuals (Dans et al. 1997), and the number given by Schiavini et al. (1999) for the area between Punta Ninfas and Cabo Blanco, Argentina is 6,628. Some subpopulations are thought to have been seriously depleted by human activities (e.g., those off Peru, Van Waerebeek 1994.).

There is a hiatus in distribution spanning about 1,000 km along the Chilean coast, and the animals off Patagonia are smaller than those off northern Chile and Peru, suggesting that the subpopulations in western and eastern South America are separate. It remains uncertain whether the groups around oceanic islands in the western South Pacific (Campbell, Auckland, and Chatham), South Atlantic (Gough and the Falklands), and Indian Ocean (Amsterdam, Prince Edward, and St. Paul) are discrete or regularly mix with animals in other areas (Brownell and Cipriano 1999).

Unknown