Mekong dolphins on the brink of extinction | WWF

Mekong dolphins on the brink of extinction

Posted on 18 June 2009
Mekong dolphins photographed during population surveys within 190km stretch of the River.
© CMDCP / WWF Cambodia
The Mekong River Irrawaddy dolphin (Orcaella brevirostris) population inhabits a 190km stretch of the Mekong River between Cambodia and Lao PDR. Since 2003, the population has suffered 88 deaths of which over 60% were calves under 2 weeks old. The current population is estimated to be between 64 and 76. This estimate does not include calves and juveniles.

“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 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.

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.

For more information, contact:
asnarith.tep@wwfgreatermekong.org
Mekong dolphins photographed during population surveys within 190km stretch of the River.
© CMDCP / WWF Cambodia Enlarge
The latest population is estimated between 64 and 76 members.
© CMDCP / WWF Cambodia Enlarge
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.
© CMDCP / WWF Cambodia Enlarge
This freshwater mammal displays interesting playful natural behaviour in areas where they are less disturbed.
© CMDCP / WWF Cambodia Enlarge

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