Grayling , a soft-rayed fish, of the salmon family, and genus thymallus (Cuv.), found in the rivers of northern Europe, Asia, and America. The English grayling has the head and body elongated, the former pointed and flattened on the top; two dorsals, the first much longer than it is high and with numerous rays, the second small, adipose, and rayless; the mouth small; the teeth numerous, conical, small, in a single series on the jaws and anterior part of the vomer, none on the tongue; the scales rather large, and the lateral line not very conspicuous; the air bladder is capacious, and communicates with the gullet by a very small tube; the caudal is forked; branchios-tegal rays seven or eight. It is very handsome and lively, though less active than the trout; the general color is light yellowish brown, with reflections of golden, copper, green, and blue, and some dark spots; the head brown, and the fins darker than the body; the dorsal fin is varied with square dusky spots; the colors grow darker by age, and in dark waters; the iris is golden yellow, and the pupil blue.
This is probably the T. vulgaris (Nilss.), found in a few of the rivers of England, in restricted localities, in Sweden, Norway, and Lapland, but probably not in Ireland or Scotland. It prefers rivers with rocky and gravelly bottom, with alternate stream and pool; it swims deeper than the trout, and feeds on flies and aquatic larvae, especially on those which construct cases (like the May flies), and on small shells and crustaceans. It is excellent for the table, is in the finest condition in October and November, and should be dressed soon after being taken; it rises to the fly, but less readily than the trout. From the size of its dorsal it cannot stem rapid currents nor leap falls. The generic name was given from an alleged resemblance of the odor of its flesh to that of thyme; from its color and odor St. Ambrose is said to have called it the "flower of fishes." Unlike other salmonidoe, it spawns in April or May; the average length is 10 or 12 in., with a weight of about 1 1/2 lb., but they have been taken weighing 4 1/2 lbs.
For a full and interesting account of the habits and history of this fish, the reader is referred to the seventh "Conversation" in "Salmonia," by Sir Humphry Davy. Other species are the T. vexilli-fer (Ag.), from the rivers of France and the Swiss lakes and streams; and the naked-throated grayling (T. gymnothorax, Val.), in which the parts beneath the throat are destitute of scales, found in Prussia and Russia. The grayling is called ombre in French and Aesche in German, probably from its prevailing ashy gray color in the water. In America, this fish has been found in the cold clear waters of Great Bear and Winter lakes, and in streams emptying into Mackenzie river. Back's grayling (T. signifer, Rich.) has not been discovered south of lat. 62° N.; this is a large species, about 17 in. long, and highly esteemed by the Esquimaux and the voyageurs.
Back's Grayling (Thymallus signifer).