Abstract: The Indo-Pacific bottlenose dolphin (Tursiops aduncus) was first confirmed in the coastal waters of the Oita Prefecture in eastern Kyushu, Japan. Boat-based sighting surveys and opportunistic observations for this species were conducted during the survey periods of 56 d between June 2002 and December 2004 in the Oita region. There were five sightings of this species in April, May, and November in 2003 and December in 2004—two groups consisting of more than a dozen dolphins and three solitary dolphins. Seven individuals of these sightings were identified by dorsal fins. Among them, five individuals were confirmed as having been previously identified in Kagoshima Bay in southern Kyushu, suggesting that individual dolphins might travel over hundreds of kilometers. These five dolphins were considered temporary migrants to the Oita region because we could find them only in the spring of 2003. During the boat-based sighting surveys, the common bottlenose dolphin (T. truncatus) were found only in November for two consecutive years. These dolphins may be temporary, possibly seasonal visitors to the region. These two species used different water depth ranges in the same bay, indicating that the two species preferred different habitats. A single sighting in 2009 of Tursiops sp. in waters adjacent to the Oita Prefecture, Seto Inland Sea, is also reported.
Key Words: bottlenose dolphin, Tursiops aduncus, Tursiops truncatus, Japan, habitat preference, long-distance movements
Document Type: Research article
Page Numbers: 145-152