For 17 years, biologist Zeb Hogan has been searching for the largest freshwater fish in the world. On June 13, his team found it – a gi...
For 17 years, biologist Zeb Hogan has been searching for the largest freshwater fish in the world. On June 13, his team found it – a giant freshwater stingray, or Urogymnus polylepis.
The stingray, which emerged from the troubled waters of the Mekong in Cambodia, was 13 feet long before being returned to the river. And at 661 pounds, it was 15 pounds heavier than a giant Mekong catfish caught in Thailand in 2005. Dr Hogan said he had previously established that freshwater fish were the biggest ever caught.
Although this species of giant stingray has an extremely dangerous venomous barb that can grow to nearly a foot in length, it does not generally pose a threat to humans. Most often, they end up on the market as a cheap source of protein.
Fishermen in Cambodia first alerted Dr Hogan and his team to the Wonders of the Mekong project, which works to protect the aquatic diversity of the Southeast Asian river and is sponsored by the United States Agency for International Development , that they had caught a stingray bigger than anyone had ever seen. Team members rushed to the small river island, called Koh Preah, and lined up three industrial ladders. Using a tarp, they hoisted the stingray out of the water and onto the scales to check its weight.
Discovery comes less than a month after another giant stingray – this one weighing 400 pounds – was caught and released nearby. Two other huge rays were also caught this year.
“The fact that the largest freshwater fish in the world was caught in the Mekong is remarkable,” Dr Hogan said. “It’s a very populated area 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 a year with an array of 36 underwater receivers that were also recently installed in a stretch of River.
“This is the first fish we’ve tagged since the array was deployed,” said Dr. Hogan, who is also an associate research professor at the University of Nevada, Reno. In the coming months, they plan to tag hundreds more fish.
With so many giant rays caught in recent months and all of them female, Dr Hogan believes this stretch of the river and the deep pools it contains are a key breeding ground for the species. The area is also home to freshwater dolphins, giant soft-shelled turtles, giant catfish and giant barbs, which belong to the carp family.
“So it’s a very unique and very understudied place,” he said. North American and European river systems receive much more scientific attention.
While breaking the world record was not scientifically significant, Dr Hogan said the existence of this fish is an indicator of the health of its ecosystem. He also hopes the discovery will remind the local community how special this river is and how much it needs to be saved.
Due to a combination of factors including dam construction, overfishing and climate change, large freshwater fish populations are generally declining. And many species of big fish are in danger of disappearing forever.
“In 2020, one of the contenders for the world’s largest freshwater fish, known as the Chinese paddlefish, was declared extinct,” Dr Hogan said. “It was very sad news, and I felt like we were going to see more extinctions of these big fish, rather than breaking records.”
Luckily, giant stingrays aren’t the only giant fish stories of recent times. In 2021, a record 240 pound lake sturgeon was captured and released into the Detroit River. And in May, a nearly 300 pound alligator may have broken the Texas state record for freshwater fish, although the angler chose to release the animal rather than kill it and bring it back for weighing.
“When you hear stories about record fish, that’s a good sign,” Dr Hogan said.
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