Cambodian villagers on the Mekong River have caught what researchers say is the world's biggest freshwater fish ever recorded, a stingray that weighed 300kg and took around a dozen men to haul ashore.

Christened Boramy, meaning “full moon” in the Khmer language because of her bulbous shape, the four-metre long female was released back into the river after being electronically tagged to allow scientists to monitor her movement and behaviour.

“This is very exciting news because it is the world’s largest fish,” said biologist Zeb Hogan, ex-host of the Monster Fish show on the National Geographic Channel and now part of a conservation project on the river...