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Mekong giant catfish
Credit: Zeb Hogan
One of the largest fish in the world, the Mekong giant catfish grows to 10 feet (3 meters). Native to the Mekong, it is critically endangered. Current threats to the Mekong giant catfish include overfishing, dam building and habitat destruction, said Zeb Hogan, host of the Nat Geo WILD's "Monster Fish." This photo was taken in Cambodia's Tonle Sap River in 2007.
In Thailand, cave paintings thought to be of the fish date back thousands of years, Hogan said. Fishermen caught a 646 pound (293 kg) giant catfish in northern Thailand in 2005; this catch is the current record holder for world's largest freshwater fish, Hogan said.