Mekong Eye

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From friends to strangers: The decline of the Irrawaddy dolphin

Today the Mekong’s dolphins face a new threat. The proposed Sambor Dam on the river’s mainstream in Cambodia.

An Irrawaddy dolphin in Cambodia. Photo Credit: Stefan Brending, licensed under CC-by-sa-3.0 de. via Mongabay

By Sabrina Gyorvary, Namthip Khudsavanh

Sambor, Cambodia, November 21, 2017

Mongabay

  • Now critically endangered, the last of the Irrawaddy dolphins (Orcaella brevirostris) are concentrated in nine deep-water pools over a 190-kilometer stretch of the Mekong between Cambodia’s Sambor district and Khone Falls on the Lao border.
  • Today the Mekong’s dolphins face a new threat. The proposed Sambor Dam on the river’s mainstream would catalyze the extinction of the remaining dolphin population and have disastrous consequences for many other fish species, as well as the communities that depend on them.
  • Can Cambodia bring this river dolphin back from the brink of extinction?
  • This post is a commentary. The views expressed are those of the author, not necessarily Mongabay.

Sitting on the banks of the Mekong River repairing his fishing net, 60-year-old Saron recalls a story from the time of his grandfather: “One cool November morning, Uncle Somnang was casting his net off the shore of his island home when a wave knocked him off balance and into the river. He struggled to right his overturned boat, but was quickly exhausted by the swift current. Suddenly, he felt a surge from below. A grey river dolphin appeared, helped him to right his boat, and gently nudged him back aboard.”

Saron’s wife Pin chimes in. “In the past, there were so many river dolphins,” she says, “they would startle us by suddenly jumping up along both sides of our fishing boats. In fact, they were just coming up to greet us and smile at us.

“Dolphins are like human beings who live under water,” Pin explains. “Like us, they feed their babies with milk. That’s why our elders taught us to never eat them.”

Sambor district sits astride the Mekong River in Central Cambodia. The river is the life force of the district — most of Sambor’s 50,000 inhabitants fish and farm along its fertile banks, or on the large islands that characterize this stretch of the Mekong.

Now critically endangered, the last of the Irrawaddy dolphins (Orcaella brevirostris) are concentrated in nine deep-water pools over a 190-kilometer stretch of the Mekong between Sambor district and Khone Falls on the Lao border.

 

Fisherfolk on the Mekong at dawn. Photo Credit: Sabrina Gyorvary via Mongabay

The first major decline in dolphin numbers occurred during the genocidal Pol Pot regime, when the Khmer Rouge used dolphin oil in lamps, motorbikes, and boat engines, and also ate dolphin meat. After the Pol Pot regime, when guns were abundant throughout Cambodia, Vietnamese and Khmer soldiers reportedly shot at dolphins for target practice.

Today, the Mekong’s dolphins face a new threat. The proposed Sambor Dam on the river’s mainstream would catalyze the extinction of the remaining dolphin population and have disastrous consequences for many other fish species, as well as the communities that depend on them. Large hydropower dams cause significant shifts in habitat size, water flow, sedimentation, and animal mobility, destroying fish and dolphin habitats and blocking migration to spawning grounds. In addition, the use of explosives during dam construction creates strong sound waves that pose a critical danger to dolphins due to their highly sensitive hearing structures.

Already, the Don Sahong Dam in Laos, less than two kilometers from the Cambodian border, has blocked the only year-round migratory channel for fish and dolphins on this section of the Mekong. Due to the impacts of the Don Sahong Dam, in combination with the illegal use of electroshock devices, poison, explosives, and nylon gill fishing nets, the dolphin population is now functionally extinct in Laos.

Kampi pool, near Sambor town, is home to around 20 of Cambodia’s last remaining 80 river dolphins. The area is home to a budding ecotourism industry, and local women, in particular, report benefits from the extra household income earned from selling boat rides to see the dolphins.

According to WWF, “Research indicates a minimum mortality rate of 16-20 percent over the last 3 years, which is clearly unsustainable. In fact, scientists suggest that mortality rates should not exceed one to two percent to ensure this small population’s long-term survival. Calf mortality rates are mysteriously high, and there is no evidence that a single calf has survived to independence during the last 3 years.”

In addition to sounding a death knell for the Mekong dolphins, the Sambor Dam would contribute to the looming food security crisis posed by a series of large hydropower dams planned for the Mekong River’s lower mainstream. If built, these dams would block the major fish migrations that are essential to the life cycle of around 70 percent of the Mekong River’s commercial fish catch. This would result in a total estimated fishery loss of 26 to 42 percent, placing the livelihoods and food security of millions of people at risk.

The dam wouldn’t just increase hunger; it would also cause many families to lose their homes. The Mekong River Commission’s 2010 Strategic Environmental Assessmentestimates that around 20,000 residents would be evicted from their homes and land to make way for the Sambor Dam’s massive reservoir.

With their way of life along the river under threat, local residents worry that their children and grandchildren will only know of dolphins as mythical creatures of the past. “The dolphins have gone from being friends to strangers,” Saron lamented.

As Mekong dolphins are revered by local people, the species makes an ideal flagship to mobilize support for broader river environment conservation issues. Rather than investing in environmentally destructive hydropower dams, the Cambodian government could take the opportunity to embrace cost-competitive renewable electricity technologies. At the same time, Cambodia could lead the region in environmental stewardship by bringing the river dolphins back from the brink of extinction.

The names of people in this article were changed to protect their identities.

Sabrina Gyorvary is Mekong Program Coordinator with International Rivers. She is based in Thailand.

Namthip Khudsavanh is a freelance researcher and folklorist based in Laos.

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