The East Siberian grayling ''(Thymallus pallasii)'' is a grayling in the

salmon Salmon (; : salmon) are any of several list of commercially important fish species, commercially important species of euryhaline ray-finned fish from the genera ''Salmo'' and ''Oncorhynchus'' of the family (biology), family Salmonidae, native ...

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Salmonidae Salmonidae (, ) is a family (biology), family of ray-finned fish, the only extant member of the suborder Salmonoidei, consisting of 11 extant genera and over 200 species collectively known as "salmonids" or "salmonoids". The family includes salmo ...

.Yury Valentinovich Dyldin. ''A review of the genus Thymallus''
/ref> Berg, L.S. (1962) ''Freshwater fishes of the U.S.S.R. and adjacent countries.'' volume 1, 4th edition., Israel Program for Scientific Translations Ltd, Jerusalem. (Russian version published 1948). Males can reach a size of .

Distribution

East Siberian grayling was first described to be found at the

Kolyma River The Kolyma (, ; ) is a river in northeastern Siberia, whose basin covers parts of the Sakha Republic, Chukotka Autonomous Okrug, and Magadan Oblast of Russia. The Kolyma is frozen to depths of several metres for about 250 days each year, b ...

basin by

Peter Simon Pallas Peter Simon Pallas Fellow of the Royal Society, FRS FRSE (22 September 1741 – 8 September 1811) was a Prussia, Prussian zoologist, botanist, Ethnography, ethnographer, Exploration, explorer, Geography, geographer, Geology, geologist, Natura ...

. Its distribution range is still insufficiently understood, and is believed to include most of the rivers flowing to the Arctic coast eastward from the

Khatanga River The Khatanga () is a river in Krasnoyarsk Krai in Russia. The river is navigable. The river port of Khatanga is located on the river. Course It begins at the confluence of the rivers Kotuy and Kheta. The Khatanga is long ( including its hea ...

, across the East Siberian Plain, and further east to easternmost Siberia, including the rivers in the

Chukotka Peninsula The Chukchi Peninsula (also Chukotka Peninsula or Chukotski Peninsula; , ''Chukotskiy poluostrov'', short form , ''Chukotka''), at about 66° N 172° W, is the easternmost peninsula of Asia. Its eastern end is at Cape Dezhnev near the village ...

as well as rivers of the

Sea of Okhotsk The Sea of Okhotsk; Historically also known as , or as ; ) is a marginal sea of the western Pacific Ocean. It is located between Russia's Kamchatka Peninsula on the east, the Kuril Islands on the southeast, Japan's island of Hokkaido on the sou ...

basin, such as the

Ola River The Ola () is a river in Magadan Oblast, Russian Far East. It is long, with a drainage basin of . The R504 Kolyma Highway crosses the Ola about north of its mouth. Course The river has its source in the Olsky Plateau, at the eastern end of ...

in the

Magadan Oblast Magadan Oblast is a federal subjects of Russia, federal subject (an oblast) of Russia. It is geographically located in the Russian Far East, Far East region of the country, and is administratively part of the Far Eastern Federal District. Magadan ...

and the Kukhtuy in

Khabarovsk Krai Khabarovsk Krai (, ) is a federal subjects of Russia, federal subject (a krai) of Russia. It is located in the Russian Far East and is administratively part of the Far Eastern Federal District. The administrative centre of the krai is the types of ...

Description

''Thymallus'' can be distinguished by their elongated, often cylindrical body, greatly enlarged dorsal fin, small mouth and striking dorsal coloration. 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 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.''. Additionally, ''Thymallus sp.'' can be distinguished by the extension of the upper jaw beyond the anterior of the eye but not to the midpoint of the eye. ''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.

Reproduction and development

''Thymallus'' spawn polygamously in the spring in rivers and lakes, with males guarding independent territories. 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. Adults do not perform any parental care. Juveniles reach sexual maturity at around 2 – 6 years old, and maximum sizes recorded are 515 mm and 488 mm, for females and males, respectively. Grayling live up to 22 years, and are known to have complex local migrations corresponding with the seasons.

Behavior, diet and predation

Adults are visual predators and stay in depths of 110 – 152 cm. Grayling feed primarily on aquatic and terrestrial insects, aquatic insect larvae, fish, small mammals, and crustacean zooplankton, and often require clear streams to feed. East-Siberian grayling predators include humans, as well as pike (''Esox sp.'').

Economic importance and conservation status

While ''Thymallus'' do not have significant commercial economic importance, they are culturally relevant and are harvested massively by anglers. Additionally, grayling require rocky or sandy bottom streams and well oxygenated water- giving them important potential as an indicator species. ''Thymallus'' pallasii are considered a species of least concern, and recent genetic work indicates ''T. pallasii'' may be part of a larger group, ''T. arcticus sl.'', composed of ''T. mertensii'', ''pallasii'' and ''signifer''.Weiss, S. J., Duarte, &, Gonçalves, V., Secci-Petretto, G., Englmaier, G. K., Gomes-Dos-Santos, A., Denys, G. P. J., Persat, H., Antonov, A., Hahn, C., Taylor, E. B., & Froufe, E. (2020). Global systematic diversity, range distributions, conservation and taxonomic assessments of graylings (Teleostei: Salmonidae; Thymallus spp.). https://doi.org/10.1007/s13127-020-00468-7/Published

References