Indo-Pacific bottlenose dolphin

Tursiops aduncus


Indian Ocean bottlenose dolphins reach a maximum size of about 2.5 meters. As their common name suggest, they have a bottle-like snout. They have relatively large flippers, dorsal fin and flukes. Their color pattern is basically grey with a slightly darker cape extending below the dorsal fin. Dark bluish spotting often extends from the belly to the throat and around the mouth, especially in older animals.

Bottlenose dolphins in the Swatch-of-No-Ground have been the focus of a photo-identification study which uses distinctive marks on the dorsal fin to identify individuals. Almost half of the dolphins identified from photographs exhibit scars and mutilations from rope and net entanglement. A population likely exceeding 1,000 Indo-Pacific bottlenose dolphins inhabits the marine waters of Bangladesh from the coast to the over 200 m deep waters along the rim of the Swatch-of-No-Ground.

Indo-Pacific bottlenose dolphins living along the Swatch-of-No-Ground take advantage of the high productivity created by upwelling currents along the canyon edge. The general absence of Indo-Pacific bottlenose dolphins in nearshore waters more strongly affected by freshwater flow may reflect inter-specific competition with Irrawaddy and Indo-Pacific humpback dolphins and possibly finless porpoises, species that are perhaps better adapted to estuarine conditions.

A major emphasis of current conservation efforts is on reducing mortality and injuries due to interactions with gillnet and trawl fisheries.