The researchers also found that calf survival was very low and that the overall population is in decline.
A small population living on the border of Cambodia and Lao People’s Democratic Republic may be in an even more perilous situation, with just 7 or 8 individuals. This is the only area in Lao PDR where dolphins remain.
WWF’s research was based on photographic identification of individual dolphins, using unique marks on their dorsal fins to help produce a population estimate.
Although the current population estimate is slightly higher than earlier estimates, the researchers note that more data and more advanced analysis mean that previously unidentified dolphins have now been included, and that the dolphin population has not increased over recent years.
“Evidence is strong that very few young animals survive to adulthood, as older dolphins die off and are not replaced,” said Dr Li Lifeng, Director of WWF’s Freshwater Programme.
Critically Endangered dolphin populations
The Irrawaddy dolphin is patchily distributed in shallow, coastal waters in the Indo-Pacific, from the Philippines to north-east India. Freshwater populations also occur in three river systems: the Mahakam of Indonesia, the Ayeyarwady (Irrawaddy) of Myanmar, and the Mekong of Cambodia, Lao PDR and Vietnam.
Although the species as a whole is classified as Vulnerable by the IUCN, the three freshwater populations are classified as Critically Endangered. Irrawaddy dolphins face a number of threats, including entanglement in fishing gear, pollution, the degradation of river systems, dam construction and live capture for aquarium display.
In the Mekong River, the Irrawaddy dolphin occurs in a 190 kilometre stretch between Cambodia and the border with Lao PDR, and although fully protected by law, it continues to face significant threats from entanglement in gill nets. The causes of the high calf mortality in this population remain unclear.
According to Dr Li, “This tiny population is at high risk by its small size alone. With the added pressures of gill net entanglement and high calf mortality we are really worried for the future of dolphins.”
Conserving dolphins in Cambodia
WWF is working to conserve this highly endangered dolphin through coordinated management with government agencies and local communities, and through the implementation of the Cambodian Mekong Dolphin Conservation Project. As part of this project, dolphin population surveys are being carried out at least twice a year, and research is being conducted into the causes of dolphin mortality.
The Irrawaddy dolphin is regarded as a sacred animal by many people in Cambodia and Lao PDR, and dolphin-watching ecotourism also provides a source of income and jobs for local communities.
WWF is calling on the Cambodian government to establish clear legislation for the protection of dolphins in Cambodia, which should include the designation of dolphin conservation zones and limits on the use of gill nets.
Read the full story at WWF – Urgent action needed to avoid extinction of Mekong dolphins.
Find out more about WWF’s work in Cambodia.
Liz Shaw, ARKive Species Text Author