Salmonidæ, a large and important family of Teleostean fishes in the order Physostomi. The family includes salmon and trout (Salmo), smelt (Osmerus), grayling (Thymallus), vendace, pollan, and 'white-fish' (Coregonus), and four or five other genera—about a hundred species in all. They inhabit both salt and fresh water, and many migrate from the one to the other. With one exception (in New Zealand), the fresh-water forms are restricted to the temperate and arctic zones of the northern hemisphere. The body is generally covered with cycloid scales, the head is naked, there are no barbules, there is an adipose or fatty fin behind the dorsal, the pelvic fins are situated about the middle of the ventral surface, the outline of the belly is rounded, the air-bladder is large and open, and with the stomach numerous pyloric cæca are associated. The eggs are large and are shed into the abdominal cavity before they are spawned. In beauty, activity, and also in palatability, the Salmonidæ rank high among fishes.
See SALMON, SMELT, TROUT, &c.; Day's British and Irish Salmonidæ (1887); and for the acclimatisation of Salmonidæ since 1864 at the antipodes, works by Sir S. Wilson (1879) and Nicols (1882).