Gold Mining, Nets Imperil Rare Dolphin, Groups Say
for National Geographic News
|March 4, 2003|
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.
Using a hodgepodge of local watercraft, the team conducted a 27-day survey of the river's entire length in November and December 2002. In 1998, a tally of 14 separate sightings led to a population estimate of 59 dolphins in the upper part of the river at the time. However, only nine sightings were chalked up during the latest, more extensive survey.
The survey numbers suggest that the population has been reduced to as few as 37 dolphins, said Smith. More surveys would be required to confirm this though, he added.
In addition to a rapid plunge in total dolphin numbers, the species has retreated far into the range it once occupied, he said. British Naturalist John Anderson reported in 1879 that the species could be found a further 500 kilometers (800 miles) downstream from the current limits of its range.
"The decline in their range and the low numbers observed indicate that this population is critically threatened," said Smith.
The primary threat affecting dolphins in the Ayeyarwady river is gill net entanglement. Fishermen increasingly prefer them over traditional throw nets. Fishermen anchor gill nets to the riverbed. The nets indiscriminately trap fish, dolphins, and other animals that swim into them.
Eighty percent of the dolphins killed in Indonesia's Mahakam River are entangled in gill nets, said Danielle Kreb, a conservation biologist with the Conservation Foundation for the Protection of Rare Aquatic Species of Indonesia, in Samarinda, East Kalimantan on the island of Borneo. Kreb estimates that as few as 65 dolphins may remain in the Mahakam River.
Destructive Fishing Practices
A further threat to the Ayeyarwady dolphin population is the illegal practice of electric fishing. Electric fishing uses high voltage to kill everything in range, allowing fishermen to easily gather dead fish from the surface of the water. The practice often occurs clandestinely at night, said Smith.
Probable poisoning from the lucrative and culturally important gold mining industry is another likely reason for the dolphin's demise. "Gold plays a huge role in the ornamentation of pagodas and Buddhist worship in Myanmar," said Smith. Mercury, which is used in chemical processes to extract gold, leaches into the river and may be slowly poisoning the dolphins and other organisms.
"Accidental catch in local fishing gear is by far the largest current threat also facing the Mekong [river] population," said Beasley, who studies Irrawaddy dolphins in that river. "If this threat could be mitigated I have no doubt that the potential survival of the population would increase 100 fold," she said.
Conflict between humans and dolphins arises because of severe poverty in these developing nations, said Beasley. "It's not a simple matter of banning gill nets and other destructive fishing practices local communities depend solely on the fisheries resources for their livelihoods," she said. The answer may lie in persuading local people to implement conservation and management initiatives, she said.
"I believe there would be good support for a site-based conservation program," said Smith, citing the obvious affection the throw net fisherman have for the dolphins. He envisages a conservation scheme that encourages throw-netting with the incentive of lucrative eco-tourism. "A protected area could preserve both the dolphins and the traditional fishing practice of cooperating with the dolphins," he said.
Smith is Asia coordinator for the Cetacean Specialist Group of the IUCN. He plans to submit a proposal that the Ayeyarwady population be listed as critically endangered on the IUCN red list of extinction-prone species.
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