The Arctic grayling is a species native to northern North America. The only populations native to the lower 48 states were in Michigan and Montana, and the Michigan population is now extinct. Consequently, the fluvial or river-dwelling population in the upper Big Hole River are the last remnants of this native Fish of Special Concern. Originally, the fluvial Arctic grayling was widespread throughout the upper Missouri river drainage as far downstream as Great Falls. Lewis and Clark made note of these "new kind of white or silvery trout" in 1805.

The lake-dwelling form is fairly common in 30 or more lakes across the western half of the state. These lake fish are genetically, but not visibly, different from our native fluvial grayling. Grayling are gullible to the angler's lures and also seem to be easily out-competed by other salmonid species. This probably explains much of their demise from their native range.

They are spring spawners and broadcast their eggs over a gravel bottom in moving streams. Grayling can overpopulate, producing severely stunted populations in some mountain lakes. Grayling are truly a unique Montana species. The iridescent hues of a spawning grayling's dorsal fin are brilliant. Exceptional individuals can weigh up to 3 pounds and reach 20 inches in length. They are generalists, eating a variety of aquatic invertebrates.