Sturgeon. They are prehistoric fish and have been around for “some 245 to 208 million years ago” (via wikipedia.org).

There are 46 different fish species that inhabit Fort Peck Reservoir, according to Montana Fish, Wildlife and Parks. Of these, FWP states 28 species are native to this stretch of the Missouri River system, including sauger and paddlefish. The other 21 species are listed as introduced species, including walleyes, smallmouth bass and northern pike. (via fortpeckguide.com) 

Among the native fish to Montana are the Shovelnose and Pallid Sturgeon.   Here’s a look at these dinosaur fish at Fort Peck:

(Feature photo via noaa.gov)