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Orcaella brevirostris
– Data Deficient
Taxonomy
Assessment Information
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Red List Category & Criteria:
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DD ver 2.3 (1994)
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Year Assessed:
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1996
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Annotations:
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Needs updating
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Assessor/s:
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Cetacean Specialist Group
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Justification:
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Extract from Reeves et al. (2003, pp. 43): "The distribution of Irrawaddy Dolphins overlaps areas of intensive use by humans. For example, in the Mekong delta, rows of netting stretch across many channels, providing a likely explanation for the lack of recent dolphin sightings in the area even though several skulls are preserved in local "whale temples" (Smith et al. 1997a). The species apparently has been seriously depleted in parts of Thailand (Andersen and Kinze in IWC 1994, p.110). Incidental mortality in fisheries (e.g., gillnets, explosives) is likely the principal cause of depletion, although the degradation of river and lake systems caused by damming, forestry practices, and mining could also play an important role (Baird and Mounsouphom 1997, Smith et al. 1997b, Kreb 1999, Smith and Hobbs 2002). Live-capture for captive display poses an additional pressure on small, localized [sub]populations such as those in the Mahakam River and possibly the Ayeyarwady River. In Australia, Irrawaddy dolphins are killed in anti-shark nets and gillnets (Parra et al. 2002).
Recent surveys indicate dramatic declines in range and abundance of the Mekong and Mahakam freshwater [sub]populations (IWC 2001). The latter was classified as Critically Endangered in the Red List in 2000 after surveys found only a few tens of dolphins, confined to an approximately 300km segment of river (Kreb 1999, 2002). Another small group of animals living at the head of Malampaya Sound in Palawan, Philippines, appears to be geographically isolated (Dolar et al. 2002). If this proves to be the case, the Malampaya population should also be classified as Critically Endangered simply by virtue of its low numbers. Surveys in 2001 resulted in an estimate of 77 individuals (CV 27.4%) confined to a 133km² area of the inner sound (B.D. Smith, unpublished data)."
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History:
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| 1988 | - | Insufficiently Known (IUCN Conservation Monitoring Centre 1988) |
| 1990 | - | Insufficiently Known (IUCN 1990) |
| 1994 | - | Insufficiently Known (Groombridge 1994) |
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Geographic Range
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Range Description:
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Extract from Reeves et al. (2003, pp. 43): "Irrawaddy Dolphins are patchily distributed in shallow, near-shore tropical and subtropical marine waters of the Indo-Pacific, from northern Australia in the south, north to the Philippines (Dollar et al. 2002) and west to northeastern India (Stacey and Leatherwood 1997, Stacey and Arnold 1999). Their distribution is centered in estuaries and mangrove areas. Freshwater subpopulations occur in three river systems; the Mahakam of Indonesia, the Ayeyarwady (formerly Irrawaddy) of Myanmar (formerly Burma), and the Mekong of Laos, Cambodia, and Viet Nam. Irrawaddy Dolphins also occur in completely or partially isolated brackish water bodies, including Chilka Lake in India and Songkhla Lake in Thailand. The animals in northern Australian waters are morphologically distinct from those in Asia (Beasley et al. 2002)."
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Countries:
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Native:
Australia; Bangladesh; Cambodia; India; Indonesia; Lao People's Democratic Republic; Malaysia; Myanmar; Papua New Guinea; Philippines; Thailand; Timor-Leste; Viet Nam
Uncertain presence and origin:
Brunei Darussalam; Singapore
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FAO Marine Fishing Areas:
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Native:
Indian Ocean-eastern; Pacific-western central
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Habitat and Ecology
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System:
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Freshwater; Marine
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