As Chinese-built dams multiply, 1 in 5 Mekong fish species face extinction, report finds: ‘biggest threat is hydropower’

Unsustainable development threatens the health and diverse fish populations of the Mekong river, with one-fifth of fish species in Southeast Asia’s main artery facing extinction, a report by conservation groups said on Monday.

Threats to its fish include habitat loss, conversion of wetlands for agriculture and aquaculture, unsustainable sand mining, introduction of invasive species, worsening climate change and hydropower dams fragmenting the flow of the river and its tributaries, according to the report compiled by the WWF and 25 global marine and wildlife conservation groups.

“The biggest threat right now, and a threat that’s still potentially gaining momentum, is hydropower development,” said fish biologist Zeb Hogan, who heads the USAID-partnered Wonders of the Mekong, one of the groups behind the report.

Dams alter the flow of the world’s third-most biodiverse river, change water quality and block fish migration, he said.

Proliferating Chinese-built hydroelectric dams upriver have blocked much of the sediment that provides essential nutrients to tens of thousands of farms in the Mekong River Delta, Reuters reported in 2022.

Some 19 per cent of the 1,148 or more fish species in the Mekong are heading towards extinction, said the conservationists’ report, “The Mekong’s Forgotten Fishes”, adding that the number may be higher as too little is known about 38 per cent of the species to gauge their conservation status.

Among those facing extinction are 18 species listed as “critically endangered” by the International Union for Conservation of Nature, including two of the world’s largest catfish, the world’s largest carp and the giant freshwater stingray.

“Some of the largest and rarest fish … anywhere on earth occur on the Mekong