Adult dorsum color ranges from dark purple to blue/black, and claret red spots are sometimes observed above ventral fins and on the caudal peduncle.

Adults can have dark lateral spotting, and the lower caudal lobe is often longer than the upper lobe [6] [7] East-Siberian grayling were first described by Valenciennes (1828) and were described as having a less acute pectoral fin, radiating streaks on the operculum, longer dorsal fin rays, and narrower maxillae than other Thymallus sp..[8] Additionally, Thymallus sp.

including T. pallasii often have plastic phenotypes distinguished by differences in relative length, rows of spots on dorsal fins and caudal peduncle color.

Eggs are laid in shallow areas of clear, fast-moving streams with rocky or sandy bottoms, and incubate for between 13 and 18 days before hatching.

[16] Additionally, grayling require rocky or sandy bottom streams and well oxygenated water- giving them important potential as an indicator species.