National Geographic –
We know that the whale shark is the biggest fish in the ocean, but what is the world’s largest freshwater fish? The answer to that seemingly simple question has remained a mystery as murky as the Southeast Asian rivers in which it’s most likely found.
Officially, the heavyweight title belongs to the Mekong giant catfish, with a specimen caught in northern Thailand in 2005 weighing an astounding 646 pounds. But researchers have long believed there are bigger fish out there, with a mysterious giant freshwater stingray being the top contender.
Now, there is increasing evidence they might be right. A recent survey of rivers in Indonesia suggests that a species known as the giant freshwater stingray may indeed grow much heavier than the giant catfish, with one stingray caught by a fisherman in South Sumatra said to have weighed more than 800 pounds, or twice as much as an adult mountain gorilla. Unverified reports from Borneo suggest catches of rays of similar size or even larger.
Zeb Hogan, a fish biologist at the University of Nevada, Reno, and a National Geographic Explorer, has been searching for the world’s largest freshwater fish species for the past 15 years. He says it’s almost impossible to confirm such accounts, but he’s convinced that giant stingrays can grow to record sizes.