Scientists working in the Eg and Uur rivers in northern Mongolia
in 2006 found this 5-foot-long (1.5-meter-long) taimen that had choked to death on a 3-foot-long (0.9-meter-long) taimen.
The taimen, a voracious and cannibalistic predator, has earned the nickname "river wolf" because it hunts in packs.
"These fish will eat anything they can fit into their mouths—ducks, muskrats, even bats," said Zeb Hogan, who leads National Geographic Society's Megafishes Project
, an effort to document the 20-some species of giant freshwater fish found around the world.
Despite its status as an apex predator in these remote rivers, the taimen is threatened with extinction due to poaching and habitat destruction throughout its range in Russia, Mongolia, and China.
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Photograph courtesy Zeb Hogan/ WWF Conservation Science Fellow/National Geographic Emerging Explorer