Mekong river dolphin nearly extinct - WWF

Pollution in southeast Asia's Mekong River has pushed freshwater dolphins in Cambodia and Laos to the brink of extinction, a conservation report said, sparking a furious government denial.

The WWF said only 64 to 76 Irrawaddy dolphins remain in the Mekong after toxic levels of pesticides, mercury and other pollutants were found in more than 50 calves who have died since 2003.

"These pollutants are widely distributed in the environment and so the source of this pollution may involve several countries through which the Mekong River flows," said WWF veterinary surgeon Verne Dove in a press statement.

The organisation said it was investigating how environmental contaminants got into the Mekong, which flows through Cambodia, Laos, Myanmar, Thailand, Vietnam and the southern Chinese province of Yunnan.

However, the Cambodian government official tasked with caring for the country's Irrawaddy dolphins said there remained "about 150 to 160" of them in the Mekong, and alleged the WWF's report used flawed research methodology.

"It's big trouble - they [the WWF] should resign. They should leave Cambodia," said Touch Seang Tana, chairman of Cambodia's Commission to Conserve Mekong River Dolphins and Develop Eco-tourism.

"They published this without consulting me, and I'm the authority here," he said, adding he did not believe the river contained the pollutants listed in the WWF's report.

The WWF said it suspected that high levels of mercury found in some dead dolphins came from gold mining activities. It added that Irrawaddy dolphins in Cambodia and Laos urgently needed a health programme to counter the effects of pollution on their immune systems.

Inbreeding among the small population could have also contributed to weakened immune systems in the dead young dolphins, all of whom were under two weeks old.

"The Mekong River dolphins are isolated from other members of their species and they need our help," said WWF Cambodia country director Seng Teak, adding the mammals "can show remarkable resilience" if their habitat is protected.

The Mekong River Irrawaddy dolphin, which inhabits a 190-kilometre stretch in Cambodia and Laos, has been listed as critically endangered since 2004, the WWF said.