Encyclopædia Britannica, Ninth Edition/Grayling
GRAYLING (Thymallus) are fishes belonging to the family of Salmonidæ, which resemble the vendace and gwyniad (Coregonus) in having scales of considerable size, and a narrow mouth with very small teeth. They are distinguished by their large, wing-like, dorsal fin. Only a few species are known, which inhabit clear streams of the north of Europe, Asia, and North America. The best known are the "Poisson bleu" of the Canadian voyageurs, and the European species, Thymallus vulgaris (the Asch or Aesche of Germany, Ombre of France, and Temola of Upper Italy). This latter species is esteemed on account of its agreeable colours (especially of the dorsal fin), its well-flavoured flesh, and the sport it affords to anglers. It is very fastidious in the choice of the rivers it inhabits. In England it is found in the Test, the Avon, the Dove, the Lug, the Wye, the Irvon, the Teme, the Clun, the Hodder, the Trent, the Dee, the Wiske, the Wharfe, the Ure, the Kibble, and the Derwent; but it is not found either in Scotland or in Ireland. It is more generally distributed in Scandinavia and Russia, and the mountain streams of central Europe southwards to the Alpine waters of Upper Italy. Specimens attaining to a weight of four pounds are very scarce. See Ichthyology.