The Guiana Dolphin (sensu Flores and da Silva 2009) is found mostly in shallow waters near shore and in estuaries along the Atlantic coast of northwestern South America, from Florianópolis, Santa Catarina State, southern Brazil (27º35'S), northwards into the Caribbean Sea and along the coast of Central America to the mouth of the Layasiksa River, the west side of Waunta Lagoon (13°40'N), northeastern Nicaragua (Carr and Bonde 2000) and possibly Honduras (15°58'N, 79°54'W) (Flores and da Silva 2009). In the Orinoco River, there are frequent records of Sotalia dolphins at Ciudad Bolívar, some 300 km upstream, which are suspected to correspond to S. guianensis (da Silva and Best 1996, Meade and Koehnken 1991, Flores and da Silva 2009). Boher et al. (1995) reported a sighting in the middle Orinoco, 800 km inland. Although there are disputed reports of Sotalia dolphins in the upper Orinoco, and even in the Apure River (Hershkovitz 1963, Borobia et al. 1991, but see Boher et al. 1995), there are no confirmed records from the upper Orinoco and Apure Rivers, or in the lower reaches of most of the major Orinoco tributaries, in a compilation of sightings over the period from 1983 to 1990 (Meade and Koehnken 1991). It is assumed that Sotalia dolphins cannot traverse the rapids at the Casiquiare Channel, which connects the Orinoco and Amazon River basins (da Silva and Best 1996).
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