A giant stingray, weighing 660 pounds, has been caught in the Mekong River in Cambodia. Scientists believe it is the world’s largest recorded freshwater fish.

Wonders of the Mekong, a joint Cambodian-U.S. research project, said in a statement on Monday that the stingray was captured by a local fisherman south of Stung Treng in northeastern Cambodia on June 13. 

The fisherman immediately alerted a nearby team of scientists from the Wonders of the Mekong project. Scientists arrived at the scene within hours of getting the call and were amazed at what they saw.

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“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 fish measured almost four meters (13 feet) from snout to tail and weighed slightly under 300 kilograms (660 pounds).

The previous record for a freshwater fish was a 293-kilogram (646-pound) Mekong giant catfish, which was found in Thailand in 2005.

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

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

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