Arctic Grayling

One of 11 fish species native to Yellowstone National Park, fluvial (entirely stream-dwelling) Arctic grayling (Thymallus arcticus) were historically common within the Madison, Gibbon, Firehole, and Gallatin rivers. However, with the introduction of competing non-native fishes such as brown trout (Salmo trutta) and brook trout (Salvelinus fontinalis), and the fragmentation of migratory pathways caused by the construction of the Hebgen dam, fluvial grayling have most likely been eliminated from their entire native range in the upper Missouri River drainage within the park. Although anglers occasionally catch grayling in the Gibbon River, research has shown they are from the headwater lakes. The only known grayling populations that remain in the park are adfluvial (lake-dwelling).