Tursiops aduncus 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Cetartiodactyla Delphinidae

Scientific Name: Tursiops aduncus (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.
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.
Previously published Red List assessments:

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 occurrence:
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:
Indian Ocean – western; Indian Ocean – eastern; Pacific – western central; Pacific – northwest
Additional data:
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).
Current Population Trend:Unknown
Additional data:
Population severely fragmented:No

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).

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.

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. The IUCN Red List of Threatened Species 2012: e.T41714A17600466. . Downloaded on 21 September 2018.
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