A giant stingray may be the world’s largest freshwater fish

 

 For 17 years, Zeb Hogan, a biologist, has been searching for the world’s largest freshwater fish. On June 13, his team found it — a giant freshwater stingray, or Urogymnus polylepis. The ray, hauled out of the murky waters of the Mekong River in Cambodia, measured 13 feet in length before it was returned to the river. And at 661 pounds, it was 15 pounds heavier than a Mekong giant catfish caught in Thailand in 2005. Dr. Hogan said he had previously established that freshwater fish as the largest ever caught.
While this species of giant stingray has an extremely dangerous venomous barb that can reach nearly a foot in length, they are not usually a threat to humans. More often, they wind up in the market as a source of cheap protein.

Fishers in Cambodia first alerted Dr. Hogan and his team at Wonders of the Mekong Project, which works to protect the Southeast Asian river’s aquatic diversity and is sponsored by the U.S. Agency for International Development, that they had caught a stingray larger than anyone had ever seen. Team members rushed to the small river island, called Koh Preah, and lined up three industrial scales. Using a tarp, they hoisted the stingray out of the water and onto the scales to verify its weight.
The discovery comes less than a month after another giant stingray — that one weighing 400 pounds — was caught and released nearby. Two other enormous rays have also been caught this year.
“The fact that the world’s largest freshwater fish was caught in the Mekong is remarkable,” Dr. Hogan said. “This is a heavily populated region, and the river faces a ton of challenges, including lots of fishing.”
In another first, Dr. Hogan’s team was able to fit the stingray with an acoustic tag to track the animal for up to one year with an array of 36 underwater receivers that were also recently installed in a stretch of the river. “This is the first fish that we’ve tagged since having the array deployed,” said Dr. Hogan, who is also a research associate professor at the University of Nevada, Reno. In the months ahead, they plan to tag hundreds of additional fishes.