This is fishy...
"Fishermen in northern Thailand have netted a fish as big as a grizzly bear, a 646-pound Mekong giant catfish, the heaviest recorded since Thai officials started keeping records in 1981. The behemoth was caught in the Mekong River and may be the largest freshwater fish ever found."
Via JD Lasica.
Update...WWF report on the story too, so maybe this isn't a hoax...