grayling, common name for a brilliantly colored fish belonging to the genus Thymallus, of the family Salmonidae (salmon family), and closely allied to the smelt. Graylings are found chiefly in clear, cold, fresh waters of the Northern Hemisphere. They average 1 ft (30 cm) in length and 1 lb (.45 kg) in weight and exhibit hues of silver, gold, violet, blue, and olive brown. The American species include the arctic grayling, said to reach 4 lb (1.8 kg), the now scarce Michigan grayling, and the Montana grayling, found in the tributaries of the Missouri. The genus name, Thymallus, refers to the odor of wild thyme characteristic of the delicious flesh of fresh specimens. Graylings are classified in the phylum Chordata, subphylum Vertebrata, class Osteichthyes, order Clupeiformes, family Salmonidae.