Distribution of the rough-toothed dolphin (Steno bredanensis) around the Windward Islands (French Polynesia)

Abstract

The rough-toothed dolphin (Steno bredanensis) has been described as a primarily pelagic cetacean species that is found in tropical and subtropical oceans throughout the world. Information on distributional patterns or habitat preference in most regions where S. bredanensis has been reported is limited. This study reports on the distribution of S. bredanensis around the Windward Islands of French Polynesia. Data were obtained from vessel surveys between 1996 and 2000, where rough-toothed dolphins were sighted 38 times. Group sizes of rough-toothed dolphins ranged between 1 and 35 individuals, with an average size of 10.8 individuals. When corrected for effort, results indicated that in French Polynesia S. bredanensisis found over a wide area but is more commonly distributed in shore than offshore. Rough-toothed dolphins were usually sighted 1.8 to 5.5 km from the barrier reef, in water depths between 1,000 and 2,000m. Our results also demonstrate the year-round presence of this species around Tahiti and Moorea. Steno bredanensis has been reported in many oceanic archipelagos, and our findings may provide insight into preferred habitat and small-scale oceanographic conditions associated with regions where this cetacean species is relatively abundant.