Taimen are monster trout and are the largest members of the salmonid family. They can live for fifty years and some reach 60 inches in length. Fish in the 30 inch range are commonly caught.  All fishing is with barbless hooks and strictly catch and release.
The Taimen are what take most fishermen to Mongolia, and the chance to catch a trout that can sometimes go as large as 60 inches, on a dry fly is one of those bucket list experiences that every fly fisherman dreams of. 
Lodges where you can find them: Mongolian River Outfitters, Mongolian Taimen Camps,
Zhupanova River Float Trips,