Mekong River dolphin death reduces Lao population to five

Mekong River dolphin death reduces Lao population to five
Irrawaddy dolphin, Mekong River, Cambodia Irrawaddy dolphins (Orcaella Brevirostris) at Koh Kon Sat, Mekong River, Cambodia. Credit: David Dove / WWF Greater Mekong

The discovery of a deceased female Irrawaddy river dolphin on Cheutal Touch Island, Cambodia – close to the border with Laos – is yet another reminder of the plight of this critically endangered cetacean in the Mekong River, WWF said on Tuesday. With just five animals remaining in Laos, WWF urged Laos and Cambodia to work together on common solutions to save one of the world's most iconic species and a major source of tourist revenue.

The dolphin, weighing 223 kilogrammes and measuring 2.4 metres in length, was believed to be one of just six remaining in a 6-km2 trans-boundary river pool that spans the Laos-Cambodia border.

Locals spotted the dolphin on the island's beach last Wednesday and immediately alerted the river authorities, which then transferred her to Kratie, Cambodia for inspection. Although the cause of death is yet to be determined, marks on her body indicate she was elderly.

"This is a very sad time for this dwindling population of dolphins," said Thomas Gray, Manager of WWF's Greater Mekong Species Programme. "There are now just five dolphins left in Laos and it is another warning that the species is facing the grave risk of extinction from the country, and also throughout the Mekong River."

The dolphins that inhabit the Wang Paa Khaa river pool have been fighting for survival in recent decades, with the placement of gillnets and the use of illegal fishing methods such as explosives and poison seriously reducing their population. Gillnet entanglement has been identified as the major cause of dolphin mortality in the river, as local fishermen have been using these nets more and more over the last few years.

Cambodia has banned gillnet fishing in the entire pool and nearby areas on its side of the border, but Laos has only prohibited their use in the pool's deepest parts within its territory.

Perhaps most threatening of all is the planned construction of the 260 megawatt Don Sahong Dam in Laos, just 3 km upstream from the pool. This will involve the use of explosives to excavate millions of tonnes of rock and has the potential to kill or seriously harm the sensitive hearing of the nearby dolphins.

Mekong River dolphin death reduces Lao population to five
The construction of the Don Sahong dam threatens a key population of the endangered Irrawaddy dolphin. Credit: Roland Seitre / WWF

"The small population size and high calf mortality means these rare and beautiful dolphins are facing a highly uncertain future, but there is still hope for them. Joint conservation action between both countries is paramount," said Teak Seng, WWF-Greater Mekong Conservation Director.

Historically, as many as 40-50 dolphins are believed to have used the trans-boundary pool, with numbers falling to around 25 in the mid-1990s. Despite this, they are a massive tourism draw and attract about 20,000 visitors annually, with almost guaranteed dolphin sightings by all.

There are an estimated 85 remaining in the Mekong River, of which Cambodia is home to the vast majority.

"The key is collaboration between Laos and Cambodia," said Seng. "It's time to end the use of all types of gear and strictly regulate the use of gillnets and boat traffic. Working on these issues is the only long-term hope for the dolphin's survival in Laos and the greater Mekong."


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Citation: Mekong River dolphin death reduces Lao population to five (2015, April 8) retrieved 22 July 2019 from https://phys.org/news/2015-04-mekong-river-dolphin-death-lao.html
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