6 Endangered giant Mekong catfish – one of the world's largest and rarest freshwater fish – spotted in Cambodia

Six critically endangered Mekong giant catfish – one of the world's largest and rarest freshwater fish – were recently caught and released in Cambodia, reviving hopes for the species to survive.

The underwater giants can grow up to 10 feet long and weigh up to 660 pounds, or as heavy as a grand piano. They are now only found in the Mekong River in Southeast Asia but in the past people lived along the 3,044 mile long river, all the way from the river her in Vietnam to the northern plains of Yunnan province in China.

The species' population has fallen by 80% in recent decades due to increased pressure from overfishing, dams that block the migration route that the fish take to spawn and other disturbances. According to the World Wildlife Fundsome experts believe that there may only be a few hundred Mekong giant catfish left.

Few of the millions of people who depend on the Mekong for their livelihood have ever seen a giant catfish. The discovery of six of the giants, caught and released within 5 days, is unique.

The first two were on the Tonle Sap river, a tributary of the Mekong not far from the Cambodian capital of Phnom Penh. They were given identification tags and released. On Tuesday, fishermen caught four more large fish, including two longer than 6.5 feet that weighed 264 pounds and 288 pounds, respectively. The fish caught were apparently migrating from their floodplain habitats near Tonle Sap Lake in Cambodia north along the Mekong River, presumably to spawning grounds in the north Cambodia, Laos or Thailand.

“It is a positive sign that the species is not imminently, as in the next few years, in danger of extinction, which will give time for conservation activities to be implemented and continue to bend the curve away from decline and toward recovery,” said Dr. Zeb Hogan, a research biologist at the University of Nevada Reno who leads the Wonders of the Mekong project funded by the US Agency for International Development.

Little is still known about the giant fish, but over the past two decades a joint conservation program with Wonders of the Mekong and the Cambodian Fisheries Administration has caught, tagged and released around 100 of them, ' get an insight into how the catfish move, where they live and the health of the species.

“This information is used to establish migration corridors and protect habitats to try to help these fish survive into the future,” said Hogan.

The giant Mekong catfish is woven into the cultural fabric of the region, depicted in 3,000-year-old cave paintings, revered in folklore and considered a symbol of the river, whose fishing feeding millions and valued at $10 billion annually.

Local communities play a vital role in conservation. Fishermen now know the importance of reporting accidental catches of rare and endangered species to authorities, allowing researchers to reach locations where fish have been caught and the measure and tag them before release.

“Their cooperation is critical to our research and conservation efforts,” Heng Kong, director of Cambodia's Inland Fisheries Research and Development Institute, said in a statement.

In addition to the giant Mekong catfish, other large fish on the river include the salmon carp, which was thought to be extinct until it was spotted earlier this year, and the giant stingray .

That four of these fish were caught and tagged in one day appears to be a “big fish story of the century for the Mekong,” said Brian Eyler, director of the Center's Southeast Asia Program. Stimson based in Washington. He said that the sighting proves that the annual fish migration was still strong despite all the pressure on the environment along the Mekong.

“We hope that what happened this week will show the Mekong countries and the world that the mighty Mekong fish population is very special and needs to be preserved,” he said.

Threats to endangered aquatic species

In addition to overfishing and plastic pollution, the Mekong River Basin has been depleted by upstream dams and climate change, which has had a major impact on water levels in the critically endangered catfish's aquatic home.

According to WWF, threats to the giant Mekong catfish include infrastructure development such as dams that block migration routes.

“Without the ability to move up and down rivers, the fish have fewer opportunities to breed,” WWF says.

Cambodia has imposed strict restrictions on fishing in the great river to try to reduce the number of endangered aquatic species killed in nets.

Numbers of Irrawaddy dolphins – which once swam through much of the mighty Mekong – have dwindled despite efforts to conserve them.

In 2022, Cambodian fishermen were shocked when they accidentally landed on an endangered giant freshwater stingray four meters (13 feet) long and weighing 180 kilos.

Over the past 25 years, the CFA and researchers have captured and released approximately 100 big catfish as part of a conservation program that encourages fishermen to report captures of rare species.

Conservationists said the recent large catches of catfish signal “a new era of conservation” and “new hope for the survival of a species that has become increasingly rare in much of its native habitat”.

Agence France-Presse contributed to this report.