Thymallus - Two species of the genus Thymallidae. Freshwater river and lake fish. They have teeth on the jaws, scolex, on the palate and sometimes on the tongue, a long and high dorsal fin. Thymallus thymallus lives in the waters of Europe, there is no it in the Caucasus and the Crimea. It reaches 50 cm in length and weighs up to 1 kg. It reaches sexual maturity in 2-3 years, in the north in 7 years. Spawns in May-June. It lays its bottom eggs on sandy bottoms on the waves. Fecundity from 3 to 36 thousand eggs. It feeds on molluscs, aquatic insect larvae, insects that fall into the water, young fish and eggs. Thymallus arcticus lives in Siberian rivers from the Kara River to Kamchatka. It forms numerous subspecies of West and East Siberian, Amur, Baikal (white and black) Thymallus. It has a large mouth compared to the European, the teeth on the jaws are very prominent. It has a body length of 50 cm or more. It matures at the age of 3-5 years. Fecundity of 5-10 thousand eggs. Spawns in spring in a fast current. It feeds on aquatic invertebrates, larvae and adult insects, sometimes on fish. Thymallus is an object of local and sport fishing.
A characteristic feature is a large dorsal fin, the posterior part of which, when folded in mature males, reaches the adipose and sometimes the base of the caudal fins. Thymallus has one of the most beautiful colours of any Holarctic reservoir fish. The fish has a monotonous dark grey back, on the sides of the body of some species scattered black spots of various shapes. Siberian, Baikal, Amur, Lower Amur and yellow-spotted thymallus have a relatively large reddish spot above the pelvic fins. The pelvic fins have oblique reddish-brown stripes with a purplish tinge. The caudal and anal fins of adults are red-burgundy. The posterior part of the dorsal fin of males is higher than the anterior part. In females this part of the fin is smaller or of the same height. Several horizontal rows of reddish spots are clearly visible, ranging from rounded to long vertical stripes of turquoise or purple hues. The largest individuals (up to 5-6 kg) are found in Mongolian and European Thymallus. Dwarf forms are also known from the high mountain lakes of Siberia, which retain their fry colouration in the form of dark transverse stripes on the sides of the body throughout their lives.
Thymallus lives in clear, cold mountain streams and oligotrophic lakes at altitudes of up to 2000-2300 m above sea level. Its diet consists of zoobenthos organisms: larvae of maggots, oarworms, mayflies, chironomids, their adults and, in the warm season, a variety of airborne insects. Some species can eat other fish and, especially in larger individuals, even small rodents.
Spawning takes place at shallow depths and even on rolls, and is generally (except for the timing) very similar to that of other salmonids. It begins as early as April in more southerly areas (as early as March in Western Europe), but in the north it usually begins in May or even early June. Spawning sometimes lasts for a very long time - almost a whole month. It is likely that Thymallus, like other fish in its vicinity, releases its eggs in several stages. Thymallus meet in pairs - a female with one male, rarely with two or three. They can often be seen rubbing their bellies against rocks, exposing almost the entire belly, which then turns red. To lay their eggs, which are not particularly large, females dig small holes in the cartilage with their tail fins and cover the eggs with small stones after fertilisation. These eggs, in large quantities, are destroyed by the fish. Caviar develops quite quickly, young fish have a small yolk bladder, rise to the surface of the water, soon after being turned off, grow very quickly. Under favourable conditions, they can reach a weight of one pound or more in 2 years, and generally reach sexual maturity in the third year. After spawning, Thymallus congregate in small schools and, unlike salmon and trout, are eaten very quickly.