DISTRIBUTION OF THE SOUTH-AMERICAN DOLPHIN SOTALIA-FLUVIATILIS

The marine form of the South American dolphin Sotalia fluviatilis has an extensive and possibly continuous distribution, from the Florianopolis region, Brazil (27-degrees 35'S, 48-degrees 34'W), north to Panama (approximately 9-degrees 22'N, 79-degrees 54'W). The high number of records from 25-20-degrees-S is due to the presence of many observers in those latitudes. The freshwater form of this species inhabits the Amazon and Orinoco drainages. It is commonly seen in the Amazon, and has been found as far inland as southern Peru. The southern limit of the range of the marine form of Sotalia is associated with the confluence zone of the Brazil and Falkland currents, suggesting that low sea-surface temperature is a limiting factor, whereas in fresh water the distribution of Amazonian Sotalia seems more closely related to the movements and concentrated occurrence of prey.