A fisherman in northern Cambodia caught a giant freshwater stingray, which scientists consider the world's largest freshwater fish, but they have little information about it.

The 42-year-old fisherman, Moul Thun, hooked the 661-pound, 13-foot-long fish on a remote island on the Mekong River in the Stung Treng district.

He caught the giant stingray with a hook and line on the evening of June 13 and then contacted researchers the next morning, per NBC News.

Before the stingray was put back into the river, a team of scientists from the Wonders of Mekong research project helped tag, measure, and weigh it. The researchers said it was healthy when released and expected it to survive.

A decades-long quest has culminated in the discovery of a 661-pound stingray in the Mekong River https://t.co/0YlMiV0To9

— National Geographic (@NatGeo) June 20, 2022

 The tag, which produces an acoustic signal attached to the creature, will help researchers trace the giant fish's movement and discover its species habits in the Mekong river.

The research team has been in contact with local fishermen for several months, encouraging them to notify them if they catch a large fish. In recent months, the group has assisted with the release of two other enormous giant freshwater stingrays. The fisherman who caught the giant stingray was compensated at market value.

Need For Further Studies

According to Zeb Hogan, a fish biologist at the University of Nevada, the catch emphasizes the relatively little information about such giant freshwater fish.

"You have a fish that's now the record holder for the world's largest freshwater fish, and we know little about it," he said.

Hogan, who is also the host of National Geographic's "Monster Fish" television series, said that the group started focusing on the Mekong area "as a stretch of river that's particularly important for biodiversity and fisheries, and as the last refuge for these big species."

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The expert said the giant freshwater stingray has a mouth the same size as a banana, per a report from National Geographic. They have no teeth, but they are equipped with "gripping pads" for crushing prey.

"They're on the bottom finding shrimps, mollusks, and small fish. They can suck them up with this banana-shaped mouth and crush them," Hogan disclosed.

Giant Fish At Risk Of Extinction

Hogan's search for enormous fish, called the Megafishes Project and backed by the National Geographic Society, began in 2005 when a fisherman in northern Thailand caught a giant catfish in the Mekong River, which previously held the record for a freshwater fish was a 293-kilogram (646-pound).

The Megafishes Project's original goal was to locate, research, and protect the world's largest freshwater fishes. The initiative focused on freshwater-only creatures that could grow to the size of a human-at least six feet long and weighing more than 200 pounds.

Hogan said that many giant fishes are migratory that need large areas to survive, per South China Morning Post.

"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," the expert said.

Although fishing for stingrays is allowed in Cambodia, it is rarely performed because they are not considered good food. The rays, though, sometimes can get caught unintentionally.

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