Thymallidae is a family of fishes in the order Salmoniformes. The dorsal fin is long and the scales are large. The lateral line is full. The mouth is small. Teeth are not visible. Freshwater fish of swift rivers and cold lakes. Spawns in spring on stony and gravelly bottoms. Reaches 50 cm and more. Counted as 5 species. Occurs in waters of Europe (except Crimea and Caucasus), Asia and North America. There are 3 species in Russian waters - Th. thymallus, Thymallus brevirostris and Th. arcticus. Target of local and recreational fisheries.
Thymallidae are distinguished from salmonids by their long dorsal fin, which contains 17 to 24 rays. The dorsal fin of Thymallidae is very high and long, in some it takes the form of a feather and is often very brightly coloured. There is evidence that during spawning, the male creates swirls of water with his fin to prevent the milk from being carried away by the current, thus increasing the efficiency of fertilisation.