Mekong dolphins on the brink of extinction

Mekong River dolphins on the verge of extinction June 2009.

Pollution in the Mekong River has pushed the local population of Irrawaddy dolphins to the brink of extinction, according to a new WWF report.

Less than 80 dolphins left

The Mekong River Irrawaddy dolphin (Orcaella brevirostris) population inhabits a 190 kilomtere stretch of the Mekong River between Cambodia and Lao PDR. Since 2003, the population has suffered 88 deaths of which more than 60 percent were calves under two weeks old. The latest population is estimated between 64 and 76 members.


Immune system depressed by pollutants

"Necropsy analysis identified a bacterial disease as the cause of the calf deaths. This disease would not be fatal unless the dolphin's immune systems were suppressed, as they were in these cases, by environmental contaminants," said Dr Verné Dove, report author and veterinarian with WWF Cambodia.


Researchers found toxic levels of pesticides such as DDT and environmental contaminants such as PCBs during analysis of the dead dolphin calves. These pollutants may also pose a health risk to human populations living along the Mekong that consume the same fish and water as the dolphins.


"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. WWF Cambodia is currently investigating the source of the environmental contaminants," said Dr Dove.


High levels of Mercury

High levels of mercury were also found in some of the dead dolphins. Mercury, suspected to be from gold mining activities, directly affects the immune system making the animals more susceptible to infectious disease.

"A trans-boundary preventative health programme is urgently needed to manage the disease affected animals in order to reduce the number of deaths each year," said Seng Teak, Country Director of WWF Cambodia.

Inbreeding

Limited genetic diversity due to inbreeding was another factor in the dolphin deaths.
"The Mekong River dolphins are isolated from other members of their species and they need our help. Science has shown that if the habitat of cetaceans is protected then populations can show remarkable resilience," said Mr Teak.

The Mekong River Irrawaddy dolphin has been listed as critically endangered on the IUCN Red List of Threatened Species since 2004.



Mekong River

WWF is working to conserve 600,000km2 of the world's most biologically diverse, economically viable and seriously threatened forests and rivers within the Greater Mekong, home and life source to over 300 million people in Cambodia, China, Lao PDR, Myanmar, Thailand, and Vietnam.

The Mekong River Irrawaddy dolphin is regarded as a sacred animal by both Khmer and Lao people, and is an important source of income and jobs for communities involved in dolphin-watching ecotourism initiatives.

More than 60 million people in the lower Mekong basin depend on the river system for food, transport and economic activity. The Mekong River produces an estimated 2.5 million tons of fish per year, with a value of at least US$2 billion, making it the largest inland fisheries in the world. Eighty percent of the animal protein for Mekong inhabitants comes from the Mekong, with 70 percent of the commercial catch being long distance migrant species.


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