The critically endangered Irrawaddy dolphin population in the Mekong River numbers just 85, according to the reseach of WWF.

Calf survival was found to be very low, leading researchers to conclude that the small population is declining and at high risk of extinction.

Irrawaddy dolphin. [WWF]?

Irrawaddy dolphins (Orcaella brevirostris) inhabit a 190km stretch of the mainstream Mekong River between Kratie, Cambodia and Khone Falls on the border with Lao PDR.

According to Dr Li Lifeng, Director of WWF's Freshwater Programme, the research is based on photographic identification of dolphins through individually unique features of their dorsal fins. "Most of the dolphins can be identified, and we use that information to estimate the population size."

Although this population estimate is slightly higher than the previous estimate, the researchers were quick to note that the population had not increased over the last few years.

"With a larger dataset and recent analytical advances, previously unidentifiable dolphins which had few marks on their dorsal fins have been included," Dr Li said.

However, surveys conducted from 2007 to 2010 show the population slowly declining.

"Evidence is strong that very few young animals survive to adulthood, as older dolphins die off and are not replaced," Dr Li explained.

The population is ranked as critically endangered on the IUCN Red List , the highest international threat ranking for endangered species, and Irrawaddy dolphins are fully protected under the highest level of Fishery Law in Cambodia and Lao PDR. Dolphins in the Mekong continue to be threatened by gill net entanglement and the causes of calf mortality remain unclear.

"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," Dr Li said.

The research also indicates that the small population resident in the transboundary pool on the Cambodia – Lao PDR border may number as few as 7-8 individuals. This is the only area in Lao PDR where dolphins remain. WWF is working to coordinate transboundary management with government agencies and local communities in Cambodia and Lao PDR at this most critical dolphin site.

"Our best chance of saving this iconic species from extinction in the Mekong River is through joint conservation action," Dr Li said. "WWF is committed to working with the Fisheries Administration, the Dolphin Commission, and communities all along the river to reverse the decline and ensure the survival of this beautiful species in the Mekong."

WWF is asking the government of Cambodia to establish a clear legislative framework to protect dolphins in Cambodia. This should include the designation of dolphin conservation zones and should allow a ban or limit on the use of gillnets where needed. Doing so will require formalizing special legislation to protect dolphins or amendments to existing Fishery Law.

Mekong Dolphin Conservation in Cambodia

WWF is implementing the Cambodian Mekong Dolphin Conservation Project in collaboration with the Fisheries Administration and the Cambodian Rural Development Team. The project conducts research on the dolphin population and causes of mortality, environmental education, and alternative livelihood development for local communities in dolphin habitat areas.

Each year, the Cambodian Mekong Dolphin Conservation Project conducts at least two population surveys of Irrawaddy dolphins in the Mekong River. The current population estimate is based on 11 surveys from 2007-2010, usually conducted in March to May when dolphins congregate around deep pool areas in the low water.

The 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.

Irrawaddy dolphins are found in coastal areas in South and Southeast Asia, and in 3 rivers, the Ayeyarwady (Myanmar), the Mahakam (Indonesian Borneo) and the Mekong. All riverine populations are red-listed by the IUCN as critically endangered, and the species in general is listed as vulnerable.