Mongolian grayling (Thymallus brevirostris)
The species is living in the rivers and lakes of the Central Asian basin, in the basins of the Kobdo and Dzabkhan rivers (Mongolia), as well as in lakes located at the source of the Irtysh River in China. In Russia, this species is found in the southern Tuva, in small rivers and lakes belonging to the Khovd River Basin.
The scale cover is monophonic, blue-silver. Small black spots are present throughout the body or are absent. The caudal peduncle, pectoral, anal and caudal fins are gray with turquoise hue. The pelvic fins have 4-6 oblique stripes of red-burgundy color. On the dorsal fin there are 4-5 horizontal rows of brick red or crimson red spots. The spots of the lower rows are oval with a narrow border. Some spots of the upper row are vertically elongated and connected with a scarlet fin edge.
Mongolian grayling is very large; in some lakes it reaches a weight of more than three kilograms. In some reservoirs, this fish is represented by two forms – large predatory and small, feeding on benthos.
This fish was previously considered an ancestral form of all graylings, linking them to salmonids. Now the prevailing opinion is that this is a fairly young species, which was formed in isolation in the low-diversity fish communities of the drainless basin of the Khovd River in the Western Mongolia.