Off the scales: world's largest freshwater fish caught in Cambodia

An almost four-metre-long giant stingray snared in the Mekong River in Cambodia is thought to be the world’s largest recorded freshwater fish.

The stingray weighed slightly under 300 kilograms, scientists from the South-East Asian nation and the US said on Monday.

The fish was caught on June 13 by a local fisherman south of Stung Treng in north-eastern Cambodia.

The fisherman alerted a nearby team of scientists from the Wonders of the Mekong, a joint Cambodian-US research project, which has publicised its conservation work in communities along the river.

The previous record for a freshwater fish was a 293-kilogram Mekong giant catfish, discovered in Thailand in 2005, the group said.

Scientists arrived within hours of receiving a post-midnight call with the news — and were “stunned” by the sight that greeted them.

“Yeah, when you see a fish this size, especially in freshwater, it is hard to comprehend, so I think all of our team was stunned,” Wonders of the Mekong leader Zeb Hogan said in an online interview from the University of Nevada in Reno.

The university has entered into a partnership with the Cambodian Fisheries Administration and USAID, the US government’s international development agency.

Freshwater fish are defined as those that spend their entire lives in freshwater, as opposed to giant marine species such as bluefin tuna and marlin, or fish that migrate between fresh and saltwater such as the huge beluga sturgeon.

The stingray’s catch was not only about setting a new record, he said.

“The fact that the fish can still get this big is a hopeful sign for the Mekong River, ” Mr Hogan said, noting that the waterway faces many environmental challenges.

The Mekong River runs through China, Myanmar, Laos, Thailand, Cambodia and Vietnam. It is home to several species of giant freshwater fish but environmental pressures are rising.

In particular, scientists fear a major programme of dam building in recent years may be seriously disrupting spawning grounds.

“Big fish globally are endangered. They are high-value species. They take a long time to mature. So, if they are fished before they mature, they don’t have a chance to reproduce,” Mr Hogan said.

“A lot of these big fish are migratory, so they need large areas to survive. They are impacted by things like habitat fragmentation from dams, obviously impacted by overfishing. So, about 70 per cent of giant freshwater fish globally are threatened with extinction, and all of the Mekong species.”

The team that rushed to the site inserted a tagging device near the tail of the mighty fish before releasing it. The device will send tracking information for the next year, providing unprecedented data on giant stingray behaviour in Cambodia.

“The giant stingray is a very poorly understood fish. Its name, even its scientific name, has changed several times in the last 20 years,” Mr Hogan said.

“It is found throughout South-East Asia, but we have almost no information about it. We don’t know about its life history. We don’t know about its ecology, about its migration patters.”

Researchers say it is the fourth giant stingray reported in the same area in the past two months, all of them females. They think this may be a spawning hotspot for the species.

Local residents nicknamed the stingray “Boramy”, or “full moon,” because of its round shape and because the moon was on the horizon when it was freed on June 14.

In addition to the honour of having caught the record-breaker, the lucky fisherman was compensated at market rate, meaning he received a payment of about $600.