The isolated population of Irrawaddy dolphins (Orcaella brevirostris) residing in the Chheu Teal transboundary pool of the Mekong River on the Laos-Cambodia border is on the verge of disappearing.
The Mekong dolphin population has long been IUCN red-listed as Critically Endangered. Its primary habitat is now limited to waters between Kratie, Cambodia, and the border below Khone Falls in Laos. A 2020 survey resulted in an estimate of only about 89 individuals, not including recently born calves, still present in a 180 km stretch of the river. However, numbers in the transboundary pool have plummeted due to changes in the Mekong upstream, limited transboundary law enforcement, and deaths due to age. The population was considered ‘functionally extinct’ in 2016.
“The very small transboundary population of dolphins, which is thought to have been isolated for some time from the larger groups downstream in Kratie and Stung Treng, is essentially lost,” said Dr. Randall Reeves, Chairman of the International Union for Conservation of Nature Species Survival Commission’s Cetacean Specialist Group.
In 2007, photo-identification surveys, conducted by the Royal Government of Cambodia’s Fisheries Administration and WWF, recorded eight adult dolphins in this transboundary pool. Periodical photo-identification surveys indicated that this number fell to seven in 2009, six in 2012, three in 2018, and now just one, with an individual identity code ID#35, remaining in 2021.
“The slow disappearance of the transboundary dolphin population signals an alarming warning for the future of one of the world’s most threatened species. Currently, although only one dolphin remains in the transboundary pool, the Fisheries Administration will still reinforce its protection and strengthen our cooperation with Laos in managing this valuable fishery resource,” said His Excellency Poum Sotha, Delegate of the Royal Government in Charge of the Director General of Fisheries Administration. He added that the dolphins are fully protected under Cambodia’s Fisheries Law and the sub-decree on management and protection of the Mekong dolphins.
The Mekong dolphins have faced mounting threats for decades. Major known causes of the decline of the transboundary population have included drowning in gill-nets, disruptions to river flow from upstream dams, overfishing, and use of damaging fishing practices such as electrofishing. These threaten the continued survival of all dolphins in the river.
In 2020 and the first half of 2021, river patrols covering the dolphins’ habitat, in Kratie and Stung Treng provinces, removed nearly 112,000 metres of illegal gill-nets and more than 131,000 metres of illegal hook long lines. Patrols also stopped 20 cases of electrofishing.
“We urge authorities from Laos and Cambodia to closely collaborate to co-manage transboundary fisheries for the benefit of local communities in both countries and help ensure the survival of the remaining Mekong dolphins,” said His Excellency Poum Sotha.
“We are witnessing the tragic loss of the transboundary population of this iconic species. It’s truly devastating,” said Dr. Uzma Khan, Asia Coordinator for the River Dolphin Rivers Initiative, WWF, and Member of the IUCN-SSC Cetacean Specialist Group.
“We call on Laos and Cambodian governments to join hands, recognising the near extirpation of the transboundary dolphin population, stop gill-net use and other illegal fishing methods in and around the transboundary pool and urgently devise a plan to restore the habitats by maintaining flows for both dolphins and mega-fish species,” she urged.
Dam operations along the Mekong have had serious impacts along the river’s length. The planned construction of dams on the Mekong mainstream further threatens the survival of the remaining dolphins and other aquatic megafauna.
“All development activities, especially the construction of dams, should include full studies on environmental and social impacts and consequences for decision-making," His Excellency Poum Sotha urged. “I thank the Royal Government of Cambodia for their moratorium decision on the construction of dams along the Mekong River, such as the Sambo dam in Kratie province,” he added.
“The Mekong dolphins are regarded as sacred animals by Cambodian people. They support our livelihoods, providing an important source of income and jobs for communities involved in dolphin-watching tourism,” said Mr. Kung Chanthy, Chief of Community Fishery Network in Borei O'Svay Sen Chey district, Stung Treng province, Cambodia. “Cambodian people believe that where there are dolphins, there are fish. Without fish and dolphins, our livelihoods will be destroyed,” he added.His Excellency Poum Sotha and Mr. Seng Teak, WWF-Cambodia Country Director, have agreed that the Fisheries Administration and WWF will set-up a memorial dolphin statue at the Chheu Teal pool to remind the public and future generations of this last dolphin who once called these waters home.