for National Geographic News
Researchers warn that dwindling populations of the Irrawaddy river dolphin may soon become extinct in the Myanmar (formerly Burma) river from which it takes its name. The mammal is known for its habit of assisting fisherman fill their nets. A recent survey of the Irrawaddy river dolphins tallied 35 percent fewer sightings than five years ago.
According to the survey, river dolphin populations are so depleted that concerned researchers plan to submit a proposal that the Ayeyarwady population be classified as critically endangered on the International Union for the Conservation of Nature (IUCN) list of species at risk of extinction.
The Wildlife Conservation Society (WCS) led the assessment of the Ayeyarwady River (formerly Irrawaddy) in Myanmar. Surveyors tallied 35 percent fewer sightings than a 1998 assessment of the same segment of the river. Poisoning from chemical processes used by the local gold mining industry and illegal and destructive fishing practices are suspect influences in the dolphin's population decline.
"Irrawaddy river dolphins are among the cetaceans at greatest risk of population extirpation and perhaps extinction," said Brian D. Smith, a conservation researcher in Myanmar. Smith is affiliated with the New York City-based Wildlife Conservation Society (WCS) and the Whale and Dolphin Conservation Society of the U.K. (WDCS).
Without protection from human activities, Irrawaddy dolphins may soon disappear altogether from Myanmar and neighboring nations, he warns.
The two- to three-meter-long (6.6- to 10-foot-long) Irrawaddy river dolphin (Orcaella brevirostris) is similar in appearance to the better-known Beluga whale. The river dolphin habitat is coastal tropical waters and mangrove swamps across Asia, from India to northeastern Australia and the Philippines.
River-dwelling populations of the dolphin are found in Indonesia's Mahakam River on the island of Borneo; in the Mekong River, which forms a border between Thailand and Laos and meanders through Cambodia and Vietnam; and in the Ayeyarwady River which serves as the cultural and economic lifeblood of Myanmar. Two small lake-bound populations in India and southern Thailand are also known.
"The three river populations are indeed some of the most endangered cetacean populations known," said dolphin conservation scientist and WCS researcher Isabel Beasley, at the James Cook University in Townsville, Australia.
Irrawaddy dolphins are appreciated by local fishermen in some parts of Myanmar for their habit of working with them to drive fish into old-fashioned throw nets. The dolphins may benefit by catching stunned and scattered fish.
"The fishermen's catch increases greatly when they fish with the dolphins," said Smith. "They have cooperated with dolphins while fishing for at least several generations, and they claim long term relationships with individual dolphins," he said.
Smith led the survey team who estimated that only a few Irrawaddy dolphins remain in the 2,170-kilometer-long (1,350-mile-long) river. Participants in the research team included conservation workers from the WCS, the WDCS, the Myanmar Department of Fisheries and Forests, and the University of Yangon.
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