Greyling are native in cold-water regions of the Northern Hemisphere.  In North America, their native range was across northern Canada with southern extensions into Michigan and the upper Missouri Drainage above the falls.  Greyling have been introduced into a number of high mountain lakes in Wyoming, several of which are in the Big Horn Mountains.  Though they are cold-water species, greyling generally do best in relatively shallow high lakes with more moderate summer water temperatures and a longer growing season.  The greyling is a spring spawner, migrating into inlet tributaries to spawn over gravel beds.  Food of the greyling is similar to other Wyoming salmonids with perhaps a higher preference for terrestrial insects.  Greyling are easily distinguished from other trout by their larger scales and very large dorsal fin.