PANTROPICAL SPOTTED DOLPHIN (Stenella attenuata): Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE There are two species of spotted dolphin in the Western Atlantic — the Atlantic spotted dolphin, Stenella frontalis, formerly S. plagiodon (Perrin et al. 1987), and the pantropical spotted dolphin, S. attenuata. These species are difficult to differentiate at sea. The pantropical spotted dolphin is distributed worldwide in tropical and some sub-tropical oceans (Perrin et al. 1987; Perrin and Hohn 1994). Sightings of this species in the northern Gulf of Mexico occur over the deeper waters, and rarely over the continental shelf or continental shelf edge (Mullin et al. 1991; SEFSC, unpublished data). Pantropical spotted dolphins were seen in all seasons during recent seasonal aerial surveys of the northern Gulf of Mexico, and during recent winter aerial surveys offshore of the southeastern U.S. Atlantic coast (SEFSC unpublished data). Some of the Pacific populations have been divided into different geographic stocks based on morphological characteristics (Perrin et al. 1987; Perrin and Hohn 1994); however, there is no information on stock differentiation in the Atlantic population.