Tursiops aduncus

Status_ne_offStatus_dd_onStatus_lc_offStatus_nt_offStatus_vu_offStatus_en_offStatus_cr_offStatus_ew_offStatus_ex_off

Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA MAMMALIA CETARTIODACTYLA DELPHINIDAE

Scientific Name: Tursiops aduncus
Species Authority: (Ehrenberg, 1833)
Common Name(s):
English Indo-pacific Bottlenose Dolphin, Indian Ocean Bottlenose Dolphin
French Grand Dauphin De L'Océan Indien
Spanish Delfin Mular Del Oceano Indico
Taxonomic Notes: Until recently, the genus Tursiops was monospecific, but a second species - the Indo-Pacific Bottlenose Dolphin - is now also recognized (Rice 1998). It is known to be taxonomically distinct based on concordance in genetics, osteology, and external morphology (Wang et al. 1999, 2000a,b). The taxonomic status of several subpopulations of Tursiops (for example off South Africa and western Australia) is questionable, and the genus may be split further (Natoli et al. 2004).

Assessment Information [top]

Red List Category & Criteria: Data Deficient ver 3.1
Year Published: 2012
Date Assessed: 2008-07-01
Assessor(s): Hammond, P.S., Bearzi, G., Bjørge, A., Forney, K.A., Karkzmarski, L., Kasuya, T., Perrin, W.F., Scott, M.D., Wang, J.Y. , Wells, R.S. & Wilson, B.
Reviewer(s): Rojas-Bracho, L. & Smith, B.D.
Justification:
Although the species is widespread in Indo-pacific coastal waters and its aggregate abundance is probably in the tens of thousands in multiple local populations, habitat destruction and incidental takes (of unknown but possibly large magnitude) may have a significant impact on this species. However, the lack of available information precludes an assessment of this impact.
History:
1996 Data Deficient

Geographic Range [top]

Range Description:The Indo-Pacific Bottlenose Dolphin has a discontinuous distribution in the warm temperate to tropical Indo-Pacific, from South Africa in the west, along the rim of the Indian Ocean (including the Red Sea, Persian Gulf and Indo-Malay Archipelago as far east as the Solomon Islands and possibly New Caledonia) to the southern half of Japan and southeast Australia in the east (Wells and Scott 2002, Möller and Beheregaray 2001). It is also found around oceanic islands distant from major land masses within this range.

The map shows where the species may occur based on oceanography. The species has not been recorded for all the states within the hypothetical range as shown on the map. States for which confirmed records of the species exist are included in the list of native range states. States within the hypothetical range but for which no confirmed records exist are included in the Presence Uncertain list.
Countries:
Native:
Australia; Bahrain; Bangladesh; Brunei Darussalam; Cambodia; China; Comoros; Egypt; Eritrea; India; Indonesia; Iran, Islamic Republic of; Japan; Kenya; Madagascar; Malaysia; Mayotte; Mozambique; Myanmar; Oman; Pakistan; Papua New Guinea; Philippines; Saudi Arabia; Singapore; Solomon Islands; Somalia; South Africa; Sri Lanka; Taiwan, Province of China; Tanzania, United Republic of; Thailand; Timor-Leste; United Arab Emirates; Yemen
Possibly extinct:
Viet Nam
FAO Marine Fishing Areas:
Native:
Indian Ocean – eastern; Indian Ocean – western; Pacific – northwest; Pacific – western central
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population: Few estimates of abundance have been made. There are estimated to be 520–530 Bottlenose Dolphins off KwaZulu-Natal, South Africa, most of which are probably T. aduncus (the rest T. truncatus – Cockcroft et al. 1992). Between 136 and 179 (95% Cis = 124-212) are known off Zanzibar, Tanzania (Stensland et al. 2006); at least 1,200 in the Persian Gulf (Preen 2004); at least 400 photo-identified along the rim of the Swatch-of-No-Ground, Bangladesh (Rubaiyat Mansur Mowgli and Brian D. Smith pers. comm.); about 218 off western Kyushu, Japan (Shirakihara et al. 2002); 169 off Mikura Island, Japan (Kogi et al. 2004); low tens at the southern tip of Taiwan and about 50 from the northeastern Philippines (J. Y. Wang pers. comm.); 1,099 off Queensland, eastern Australia (Chilvers and Corkeron 2003) and at least 2,000–3,000 in Shark Bay western Australia (Preen et al. 1997).
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: Indo-Pacific Bottlenose Dolphins generally occur over shallow coastal waters on the continental shelf or around oceanic islands. They sometimes occur in mixed groups with Common Bottlenose Dolphins and other delphinid species. They feed on a wide variety of schooling, demersal and reef fishes, as well as cephalopods (Ross 1984; J.Y. Wang, unpubl. data).
Systems: Marine

Use and Trade [top]

Use and Trade: It is harvested for food in some places, and for international trade as display animals.

Threats [top]

Major Threat(s): The species’ near-shore distribution makes it vulnerable to environmental degradation, direct exploitation, and fishery conflicts (Curry and Smith 1997, Wells and Scott 1999; Reeves et al. 2003). Until hunting was outlawed in 1990, this species was hunted in a large-scale drive fishery in Taiwan’s Penghu Islands. Some Indo-Pacific Bottlenose Dolphins are taken in the small cetacean fisheries of Sri Lanka.

Incidental catches occur in a number of fisheries throughout the range, including gillnets and purse seines. A Taiwanese shark gillnet fishery operated in northern Australian waters during the early 1980s and took up to 2,000 per year (Harwood and Hembree 1987). Incidental catch in Taiwan continues to be a serious problem. For example, multiple individuals have been seen observed in single catches there and throughout most of the species’ range (J.Y. Wang pers. comm.). A large proportion of dolphins (~40%) off Bangladesh exhibit scars and mutilations consistent with rope and net entanglement in trawl and gill-net fisheries (Rubaiyat Mansur Mowgli and Brian D. Smith pers. comm.). In South Africa and Australia, Indo-Pacific Bottlenose Dolphins also suffer considerable mortality in the large-mesh nets set to protect bathers from sharks (Peddemors 1999, Reeves et al. 2003).

Live-captures for oceanarium display have taken place in Taiwan, Indonesia and the Solomon Islands in recent years from unassessed populations; their preference as a captive display species makes them vulnerable to depletion from such catches (Wang et al. 1999, Reeves et al. 2003, Kahn ).

Indo-Pacific Bottlenose Dolphins in coastal areas are exposed to a wide variety of threats in addition to direct and indirect takes. Threats that are cause for concern include: 1) the toxic effects of xenobiotic chemicals; 2) reduced prey availability caused by environmental degradation and overfishing (Jackson et al. 2001); 3) direct and indirect disturbance and harassment (e.g. boat traffic and commercial dolphin watching and interactive programs); 4) marine construction and demolition and 5) other forms of habitat destruction and degradation (including anthropogenic noise). Although these and other threats are technically challenging to quantify by comparison with takes, their cumulative impact is likely to result in longitudinal population declines. Lack of historical data in many cases hampers understanding of long-term trends, possibly resulting in shifting baselines.

Conservation Actions [top]

Conservation Actions: The species is listed in Appendix II of CITES.

More research is needed to establish the range and clarify the taxonomy of the genus Tursiops. More information is also needed on population size and the extent and magnitude of direct and indirect takes so that their impact on this species can be assessed.

Bibliography [top]

Chilvers, B. L. and Corkeron, P. 2003. Abundance of Indo-Pacific bottlenose dolphins, Tursiops aduncus, off Point Lookout, Queensland, Australia. Marine Mammal Science 19(1): 85-95.

Cockcroft, V. G., Ross, G. J. B., Peddemors, V. M. and Borchers, D. L. 1992. Estimates of abundance and undercounting of bottlenose dolphins off northern Natal, South Africa. South African Journal of Wildlife Research 22: 102-109.

Curry, B. E. and Smith, J. 1997. Phylogeographic structure of the bottlenose dolphin (Tursiops truncatus): stock identification and implications for management. In: A. E. Dizon, S. J. Chivers and W. F. Perrin (eds), Molecular genetics of marine mammals, pp. 227-247. The Society of Marine Mammalogy, Allen Press, Lawrence.

Harwood, M. B. and Hembree, D. 1987. Incidental catch of small cetaceans in the offshore gillnet fishery in northern Australian waters: 1981-1985. Reports of the International Whaling Commission 37: 363-367.

IUCN. 2012. IUCN Red List of Threatened Species (ver. 2012.2). Available at: http://www.iucnredlist.org. (Accessed: 17 October 2012).

Jackson, J. B. C., Kirby, M. X., Berger, W. H., Bjorndal, K. A., Botsford, L. W., Bourque, B. J., Bradbury, R. H., Cooke, R., Erlandson, J., Estes, J. A., Hughes, T. P., Kidwell, S., Lange, C. B., Lenihan, H. S., Pandolfi, J. M., Peterson, C. H., Steneck, R. S., Tegner, M. J. and Warner, R. R. 2001. Historical overfishing and the recent collapse of coastal ecosystems. Science 293: 629-637.

Kahn, B. 2006. Oceanic cetaceans and associated habitats in the western Solomon Islands. In: A. Green, P. Lokani, W. Atu, P. Ramohia, P. Thomas and J. Almany (eds), Solomon Islands Marine Assessment: technical report of marine survey – May 13 to June 17, 2004. The Nature Conservancy – Pacific Islands Countries Report.

Kogi, K., Hishii, T., Imamura, A., Iwatani, T. and Dudzinski, K. M. 2004. Demographic parameters of Indo-Pacific bottlenose dolphins (Tursiops aduncus) around Mikura Island, Japan. Marine Mammal Science 20(3): 510-526.

Moller, L. M. and Beteregaray, L. B. 2001. Coastal bottlenose dolphins from southeastern Australia are Tursiops aduncus according to sequences of the mitochondrial DNA control region. Marine Mammal Science 17(2): 249-263.

Natoli, A., Peddemors, V. M. and Hoelzel, A. R. 2004. Population structure and speciation in the genus Tursiops based on microsatellite and mitochondrial DNA analyses. Journal of Evolutionary Biology 17: 363-375.

Peddemors, V. M. 1999. Delphinids of southern Africa: a review of their distribution, status and life history. Journal of Cetacean Research and Management 1(2): 157-165.

Preen, A. 2004. Distribution, abundance and conservation status of dugongs and dolphins in the southern and western Arabian Gulf. Biological Conservation 118: 205-218.

Preen, A. R., Marsh, H., Lawler, I. R., Prince, R. I. T. and Shepherd, R. 1997. Distribution and abundance of dugongs, turtles, dolphins and other megafauna in Shark Bay, Ningaloo Reef and Exmouth Gulf, Western Australia. Wildlife Research 24(2): 185-208.

Reeves, R. R., Smith, B. D., Crespo, E. A. and Notarbartolo di Sciara, G. 2003. Dolphins, Whales and Porpoises: 2002-2010 Conservation Action Plan for the World's Cetaceans. IUCN/SSC Cetacean Specialist Group, Gland, Switzerland and Cambridge, UK.

Rice, D.W. 1998. Marine Mammals of the World. Systematics and Distribution. Society for Marine Mammalogy, Lawrence, Kansas.

Ross, G. J. B. 1984. The smaller cetaceans of the south east coast of southern Africa. Annals of the Cape Provincial Museums (Natural History) 15: 173-410.

Shirakihara, M., Shirakihara, K., Tomonaga, J. and Takatsuki, M. 2002. A resident population of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in Amakusa, western Kyushu, Japan. Marine Mammal Science 18(1): 30-41.

Stensland, E., Carlen, I., Sarnblad, A., Bignert, A. and Berggren, P. 2006. Population size, distribution, and behavior of Indo-Pacific bottlenose (Tursiops aduncus) and humpback (Sousa chinensis) dolphins off the south coast of Zanzibar. Marine Mammal Science 22(3): 667-682.

Wang, J. Y., Chou, L. S. and White, B. N. 1999. Mitochondrial DNA analysis of sympatric morphotypes of bottlenose dolphins (genus: Tursiops) in Chinese waters. Molecular Ecology 8: 1603-1612.

Wang, J. Y., Chou, L. S. and White, B. N. 2000. Differences in external morphology of two sympatric species of bottlenose dolphins (genus Tursiops) in the waters of China. Journal of Mammalogy 81(4): 1157-1165.

Wang, J. Y., Chou, L. S. and White, B. N. 2000. Osteological differences between two sympatric forms of bottlenose dolphins (genus Tursiops) in Chinese waters. Journal of Zoology (London) 252: 147-162.

Wells, R. S. and Scott, M. D. 1999. Bottlenose dolphin Tursiops truncatus (Montagu, 1821). In: S. H. Ridgway and R. Harrison (eds), Handbook of marine mammals, Vol. 6: The second book of dolphins and the porpoises, pp. 137-182. Academic Press, San Diego, CA, USA.

Wells, R. S. and Scott, M. D. 2002. Bottlenose dolphins Tursiops truncatus and T. aduncus. In: W. F. Perrin, B. Wursig and J. G. M. Thewissen (eds), Encyclopedia of Marine Mammals, pp. 122-128. Academic Press.


Citation: Hammond, P.S., Bearzi, G., Bjørge, A., Forney, K.A., Karkzmarski, L., Kasuya, T., Perrin, W.F., Scott, M.D., Wang, J.Y. , Wells, R.S. & Wilson, B. 2012. Tursiops aduncus. In: The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 02 October 2014.
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