The Irrawaddy Dolphin (Orcaella brevirostris) is a euryhaline species of Oceanic dolphin found in discontinuous sub-populations near sea coasts and in estuaries and rivers in parts of the Bay of Bengal and Southeast Asia.Etymology and Taxonomic HistoryThe Irrawaddy Dolphin was first described by Sir Richard Owen in 1866 based on a specimen found in 1852, in the harbour of Visakhapatnam on the east coast of India.
Genetically the Irrawaddy Dolphin is closely related to the Orca. The species name brevirostris comes from the Latin meaning short-beaked. In 2005, genetic analysis showed that the Australian Snubfin Dolphin found at the coast of northern Australia forms a second species in the Orcaella genus.
Overall grey to dark slate blue, paler underneath. No distinctive pattern. Dorsal fin small and rounded behind middle of back. Forehead high and rounded; beak lacking. Broad rounded flippers. The similar species that can be found in Borneo is the Finless Porpoise, Neophocaena phocaenoides, is similar and has no back fin: the Humpback Dolphin, Sausa chinensis, is larger, has longer beak and larger dorsal fin.
The several common names for Orcaella brevirostris (Latin) include: English: Irrawaddy dolphin, Local Chilika dialect: Baslnyya Magar or Bhuasuni Magar (oil yielding dolphin), Oriya: Khem and KheraDescriptionIrrawaddy dolphins are similar to the Beluga in appearance, though most closely related to the Orca. They have a large melon and a blunt, rounded head, and the beak is indistinct. The dorsal fin, located about two-thirds posterior along the back, is short, blunt and triangular. The flippers are long and broad. It is lightly coloured all over, but slightly more white on the underside than the back. Adult weight exceeds kg and length is m at full maturity. Maximum recorded length is of a male from Thailand.ReproductionThese dolphins are thought to reach sexual maturity at 7 to 9 yrs. In the Northern Hemisphere, mating is reported from December to June. Its gestation period is 14 months, giving birth to a single calf every 2 to 3 years. Length is about at birth. Birth weight is about . Weaning is after two years. Lifespan is about 30 years.BehaviorIrrawaddy dolphins communicate with clicks, creaks and buzzes at a dominant frequency of about 60 kilohertz which is thought to be used for echolocation. Bony fish and fish eggs, cephalopods, and crustaceans are taken as food. Observations of captive animals indicate that food may be taken into the mouth by suction. Irrawaddy Dolphins sometimes spit streams of water, sometimes while spyhopping, during feeding, apparently to expel water ingested during fish capture or possibly to herd fish. Some Irrawaddy Dolphins kept in captivity have been trained to do spyhopping on command. The Irrawaddy Dolphin is a slow swimmer, but swimming speed of 20–25 km/hour was reported when dolphins were being chased in a boat.
It surfaces in a rolling fashion and lifts its tail fluke clear of the water only for a deep dive. Deep dive times range from 70–150 seconds to 12min. When 277 group dives were timed (time of dis-appearance of last dolphin in group to emergence of first dolphinin the group) in Laos, mean duration was 115.3 s with a range of 19 s to 7.18 min.
Habitat and sub-populationsthumb|250px|Irrawaddy Dolphin on Kratié, Cambodia/" class="wiki">Mekong River at Kratié, Cambodia
Although sometimes called the Irrawaddy River Dolphin, it is not a true river dolphin but an oceanic dolphin that lives in brackish water near coasts, river mouths and in estuaries. It has established sub-populations in freshwater rivers, including the Ganges and the Mekong as well as the Irrawaddy River from which it takes its name. Its range extends from the Bay of Bengal to New Guinea and the Philippines.
It is often seen in estuaries and bays in Borneo Island. With sightings from Sandakan in Sabah, Malaysia, to most parts of Brunei and Sarawak, Malaysia. A specimen was collected at Mahakam River in East Kalimantan.
No range-wide survey has been conducted for this vulnerable species, however it appears that the worldwide population is over 7,000, with over 90% occurring in Bangladesh. Populations outside Bangladesh and India are classified as critically endangered. Known sub-populations of Irrawaddy Dolphins are found in eight places, listed here in order of population, including conservation status.
right|thumb|200px|Chilka Lake, Orissa, India, habitat of Irrawaddy Dolphins- Bangladesh; 5,832 (VU) in coastal waters of the Bay of Bengal
- and 451 (VU) in the brackish Sundarbans mangrove forest
- India; 138 (VU) in the brackish water Chilka Lake
Interaction with HumansIrrawaddy dolphins have a seemingly mutualistic relationship of co-operative fishing with traditional fishers. Fishers in India recall when they would call out to the dolphins, to drive fish into their nets.
Threatsthumb|200px|Fishers with fishnets in Bangladesh
Irrawaddy Dolphins are more susceptible to human conflict than most other dolphins who live farther out in the ocean. Drowning in gillnets is the main threat to Irrawaddy dolphins throughout their range. The majority of reported dolphin deaths in all subpopulations is due to accidental capture and drowning in gillnets and dragnets, and in the Philippines, bottom-set crabnets. In Myanmar, electrofishing and gold mining are also a serious and continuing threat. Though most fishers are sympathetic to the dolphins plight, it is difficult for them to abandon their traditional means of livelihood.
In several Asian countries, Irrawaddys have been captured and trained to perform in public aquariums. The charismatic appearance and unique behaviors of Irrawaddy dolphins, including spitting water, spyhopping and fluke-slapping, make them very popular for shows in dolphinariums. The commercial motivation for using this dolphin species is high because it can live in freshwater tanks and the high cost of marine aquarium systems is avoided. The region within and nearby the species’ range has developed economically and theme parks, casinos and other entertainment venues that include dolphin shows has increased. In 2002 there were more than 80 dolphinariums in at least nine Asian countries
The IUCN lists five of the seven subpopulations as critically endangered, primarily due to drowning in fish nets.[ Database entry includes a brief justification of why this species is of vulnerable.] For example, the Malampaya population was first discovered and described in 1986, at the time consisting of 77 individuals. Due to anthropogenic activities, this number dwindled to 47 dolphins in 2007.ConservationEntanglement in fishnets and degradation of habitats are the primary threats to Irrawaddy Dolphins. Multiple conservation efforts are being made at international and national levels to alleviate these threats.International efforts  Listed as Critically Endangered in Laos, Malaysia, Myanmar, Philippines, and Thailand
These dolphins are classified by the IUCN as a critically endangered species in Laos, Malaysia, Myanmar, Philippines, and Thailand and a vulnerable species in Bangladesh and India. They are thus are legally protected from hunting; however, enforcement may be poor along thousands of miles of coast line.
The UNEP-CMS Action Plan for the Conservation of Freshwater Populations of Irrawaddy Dolphins notes that multiple-use protected areas will play a key role for conserving freshwater populations of Irrawaddy dolphins. Protected areas in fresh water could be a particularly effective conservation tool and can facilitate management, due to the fidelity of the species to relatively circumscribed areas. The Action Plan provides details on strategies for mitigating by-catch that includes:
-establishing core conservation areas where gillnetting is banned or severely restricted -promoting net attendance rules and providing training on the safe release of entangled dolphins -initiating programs to compensate fishers for damage caused to their nets :by entangled dolphins that are safely released -providing alternative or diversified employment options for gillnet fishers -encouraging the use of fishing gears that do not harm dolphins, :by altering or establishing fee structures for fishing permits to make gillnetting more expensive while decreasing the fees for non-destructive gear -experimenting with acoustical deterrents and reflective nets. National efforts '
Several national efforts are resulting in the reduction of threats to local Irrawaddy Dolphin sub-populations:Bangladesh
Portions of Irrawaddy dolphin habitat in the Sundarbans mangrove forest of Bangladesh are included within of 3 Wildlife sanctuaries which are part of the Sunderbans World Heritage Site. The Wildlife Conservation Society is working with the Bangladesh Ministry of Environment and Forests to create protected areas for the 6000 remaining dolphins[Cambodia]
The Cambodian Department of Fisheries has drafted a Royal Decree for protection of Irrawaddy dolphins in the Mekong River, which includes the designation of eight protected areas, totaling , in a segment of the river above Kratie.[ The establishment of community-managed deep water Fish Conservation Zones with government support may represent the best opportunity for reducing dry season dolphin mortality from large-meshed gillnet entanglement. Efforts to establish protected areas for dolphins are currently underway. in 2005 the The World Wildlife Fund (WWF) established the Cambodian Mekong Dolphin Conservation Project with support from government and local communities. The aim is to support the survival of the remaining population through targeted conservation activities, research and education.]
The Irrawady Dolphin (under the common name of Snubfin Dolphin, with the scientific name misspelled as Oreaella brevezastris'') is included the Indian Wildlife Protection Act , Schedule I , which bans their killing, transport and sale of products. [ A major restoration effort to open a new mouth between Chilika lake and the Bay of Bengal in 2000 was successful in restoring the lake ecology and regulating the salinity gradient in the lake waters. This has resulted in increases in the population of Irrawaddy dolphin due to increase of prey species of fish, prawn and crabs.]
At East Kalimantan Island, the Semayang National Park has been proposed as a Irrawaddy Dolphin Sanctuary.[ Local conservationists have also been pressing for protection of the lake and its watershed, the Berambai Forest.]
Canadian conservationist Ian Baird set up the Lao Community Fisheries and Dolphin Protection Project to study the Irrawaddy dolphins in the Lao part of the Mekong. Part of this project compensated fishers for the loss of nets damaged to free entangled dolphins. This project was expanded to include Cambodia, after it was determined that the majority of the dolphin population had been killed or migrated to Laos' southern neighbour. The Si Phan Don Wetlands Project has successfully encouraged river communities to set aside conservation zones and establish laws to regulate how and when fish are caught.
In 2005, the Department of Fisheries established a protected area for Irrawaddy dolphins in a -km segment of the Ayeyarwady River between Mingun and Kyaukmyaung. Protective measures in the area include mandatory release of entangled dolphins, prohibition of the catching or killing of dolphins and trade in whole or parts of them and the prohibition of electro-fishing and gill nets more than long, or spaced less than . apart.[ Mercury poisoning and habitat loss from gold mining dregding operations in the river have been eliminated]
In 2000, Malampaya Sound was proclaimed a protected seascape. This is the lowest possible prioritization given to a protected area.
In 2007, the Coral Triangle Initiative, a new multilateral partnership to help safeguard the marine and coastal resources of the Coral Triangle, including the Irrawaddy dolphin sub-population in Malampaya Sound, was launched.
In 2002 the Marine and Coastal Resources Department was assigned to protect rare aquatic animals such as dolphins, whales and turtles in Thai territorial waters. To protect the dolphins, patrol vessels ensure that boats stay at least away from dolphins and that there is no chasing of or running through schools of dolphins. Many fishers on the Bang Pakong River have been persuaded by authorities to stop shrimp fishing that area, and 30 to 40 fishing boats have been modified so they can offer dolphin sightseeing tours.
In 2008, the Department of Forestry and Sarawak Forestry Cooperative in Sarawak established a protected area for Irrawaddy Dolphins in Santubong and Damai (Kuching Wetland).[ And they are also plan to established more beach in Miri as a protected area for Irrawaddy dolphins. The protected measures in the area include prohibition of the catching or killing of dolphins and trade in whole or parts of them and the prohibition of gill nets. The government may also start small and medium research of this species at Sarawak Malaysia University with sponsorship from Sarawak Shell.]
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