The Mekong’s fewer than 90 Irrawaddy dolphins at risk of slow and inexorable extinction

Known only by his identity code, ID#35 was the last individual of a doomed subpopulation of freshwater Irrawaddy dolphins (Orcaella brevirostris). He was the sole occupant of a deep pool in the Mekong River that spans the border between Cambodia and Laos, and fought for several weeks against lacerations to his tail from entanglement in illegal fishing gear. He had been struggling to swim, let alone to feed himself.

Mortally wounded, ID#35 died as many of his kin before him. Yet there was a deeper significance to the moment his pale and bloated body washed up on a riverbank in mid-February 2022: his death confirmed that the Irrawaddy dolphin is extinct in Laos.

Cetacean specialists have documented the loss of the dolphins from the Chheu Teal transboundary pool for years. In 1993, there were 17 individuals living in the pool. By 2009, the subpopulation had dwindled to seven; three years later to six; and by 2018, only three remained. In 2021, photo identification surveys led by Cambodia’s Fisheries Administration and WWF confirmed that ID#35 was all alone.

The species, found in both freshwater and marine environments in South and Southeast Asia, is considered globally endangered. However, the freshwater populations that inhabit the Irrawaddy in Myanmar, the Mahakam in Indonesian Borneo, and Cambodia’s stretch of the Mekong are critically endangered, each with fewer than 100 remaining individuals.

With the loss of the Mekong’s Chheu Teal subpopulation, the river’s fewer than 90 surviving dolphins now exclusively occur downstream in Cambodia, where they face the same range of threats that wiped out the transboundary group.

A slow and inexorable extinction

While injuries sustained through entanglement in fishing nets directly led to the death of the last transboundary dolphin, according to local media reports, conservationists say there were many factors that contributed to the subpopulation’s decline.

“The numbers in the [transboundary] pool have plummeted over the last few years, due to multiple threats,” Lan Mercado, Asia-Pacific director of WWF, said in a February 2022 statement, “including hydro-power dam construction causing disruptions to river flow and reduced fish abundance, drowning in gill-nets, and the use of damaging fishing practices such as electrofishing and overfishing.”

Of the numerous threats to dolphins in the Mekong, gill nets — vertical netting that hangs across a stretch of water — pose the greatest risk and underly the majority of accidental drownings and entanglement injuries, according to Somany Phay, deputy director of Cambodia’s fisheries conservation department and the government liaison at WWF-Cambodia.

In 2012, Cambodia established a ban on gill nets within a dolphin protection zone that spans their 180-kilometer (110-mile) core habitat and is patrolled by a team of 72 river guards. Phay said the country also established agreements with Laos on the protection and management of the Chheu Teal deep-water pool at both provincial and national levels, including gill-net bans.

However, a lack of commitment and coordination on these agreements enabled illegal fishing to continue, particularly within Lao waters, according to a 2022 report from the Cambodia Fisheries Administration, the IUCN Cetacean Specialist Group and WWF. The loss of the transboundary subpopulation ultimately came down to a “lack of participation of Lao’s authority and fishermen” in eliminating the use of gill nets and other illegal fishing practices, the report said.

The challenges of enforcing fishing regulations across national borders were brought into sharp focus during the last few weeks of ID#35’s life. Authorities and fishers had observed netting wrapped around the dolphin’s tail fluke weeks before his death, according to local media reports. However, it was unclear whether this was a result of illegal fishing in Cambodia or Laos, or which country was responsibile for the animal’s rescue and rehabilitation. Due to the ambiguity, neither country mounted a dedicated rescue.

“There are seven river guards patrolling the Cambodia side of the pool,” Phay told Mongabay. “But [because] part of the pool is in Laos, Cambodian officials have no authority to go inside Lao territory to confiscate gill nets and eliminate illegal fishing practices.”

Phay added that levels of illegal fishing in the Chheu Teal pool had ramped up since the completion of the Don Sahong hydropower dam in Laos, which began operating in 2020. Located less than 2 km (1.2 mi) north of the Cambodia-Laos border, the dam blocks one of the Mekong’s main channels where fishers once congregated, he said. As a result, fishers have been displaced further into the dolphin’s deep-pool habitat.

Wider implications

For people living near the Chheu Teal transboundary pool, the loss of the dolphins translates to a permanent loss of potential ecotourism revenues. In particular, the cetaceans once underpinned tourism-related livelihoods and businesses in Champassak province in southern Laos.

Twenty years ago, tourists could kayak to the transboundary pool to observe the dolphins “surfacing all around,” Inthy Deuansavanh, director of Green Discovery Laos, an ecotourism company that used to operate river dolphin tours, told Mongabay.

But with dolphin numbers in decline and sightings diminishing, Deuansavanh was forced to discontinue the tours five years ago, with knock-on consequences for the local community.

“We had to stop the kayaking activities there, which meant that the local people who were working as guides lost their jobs,” Deuansavanh said. “At that time, the dolphins were the main attraction of the area … boats, platforms, viewing points and restaurants, all owned and operated by local people, benefited from the business.”

The subpopulation loss has strengthened the resolve of authorities and conservationists in Cambodia to protect the remaining Irrawaddy dolphins in the river. The latest population estimate in 2020 indicated that just 89 dolphins are left in Cambodia’s waters, within a 180-km stretch of river between the Laos border and Kratie province. Like the extinct subpopulation, these last dolphins are largely confined to a series of deep pools, which renders them vulnerable to genetic isolation and further pool-by-pool extinctions.

Phay said the single most important factor is stopping gill-net use in the dolphin protection zone through public outreach, improving stakeholder cooperation, and increasing the capacity of river guards to enforce fishing bans.

“We need to safeguard all the remaining individual dolphins from suffering the same fate as the transboundary population,” Phay said. “We don’t want them to go extinct.”

This article by Carolyn Cowan was first published by Mongabay.com on 14 April 2022. Lead Image: An Irrawaddy dolphin photographed in the Mekong River in Cambodia. Photo © WWF-Cambodia / Tan Someth Bunwath.

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