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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.

The Mekong, stretching nearly 5,000 km (3,000 miles) from the Tibetan Plateau to the South China Sea, is a farming and fishing lifeline for tens of millions of people in China, Laos, Myanmar, Thailand, Cambodia and Vietnam.

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 World Wildlife Fund 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 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.