March 26, 2015 — For more than a decade, researcher Zeb Hogan has spent much of his time traveling around the world on a singular mission: to find and learn more about the world’s largest freshwater fish. Through his photographs and a show he hosts on Nat Geo Wild called "Monster Fish," he’s helped many people discover and appreciate these beasts.
The highlights of his research on the conservation status and accurate size of various fish are being presented beginning March 25 at the National Geographic Museum in Washington, D.C., an exhibition Hogan describes as a “one-stop-shop for everything megafish.”
His main finding: Most of these fish are now threatened with extinction due to habitat degradation, dam building, pollution and over-harvesting.
Throughout the course of his work, Hogan has seen some fascinating beasts. He has laid eyes on the two contenders for the world’s largest freshwater fish. Officially, that title goes to the Mekong giant catfish; fishermen in northern Thailand caught a huge specimen of the catfish that weighed 646 pounds and was 9 feet long, on May 1, 2005. “But a lot of people, myself included, think that giant freshwater stingrays may be larger,” says Hogan, a researcher at the University of Nevada, Reno. (Largetooth sawfish, which are found in fresh and saltwater, get even bigger, reaching weights of 1,300 pounds and growing to 23 feet in length.)
The Southeast Asian giant stingray (Himantura polylepis) can grow to 8 feet wide and over 15 feet long. The largest specimens found in the past few years haven’t been weighed, because that procedure can kill them, and they are endangered. Then there’s the animal’s Australian cousin, Himantura dalyensis, which can rival the Asian species in size. A similar variety found in Paraguay called the short-tailed river ray (Potamotrygon brachyura) grows to “at least 600 pounds, possibly much larger,” Hogan says.
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