''Stenodus leucichthys'' is a species of

freshwater whitefish The freshwater whitefish are fishes of the subfamily Coregoninae, which contains whitefishes (both freshwater and anadromous) and ciscoes, and is one of three subfamilies in the salmon family Salmonidae. Apart from the subfamily Coregoninae, the ...

in the family

Salmonidae Salmonidae is a family of ray-finned fish that constitutes the only currently extant family in the order Salmoniformes . It includes salmon (both Atlantic and Pacific species), trout (both ocean-going and landlocked), chars, freshwater whitefis ...

. In the strict sense its natural distribution is restricted to the

Caspian Sea The Caspian Sea is the world's largest inland body of water, often described as the world's largest lake or a full-fledged sea. An endorheic basin, it lies between Europe and Asia; east of the Caucasus, west of the broad steppe of Central Asia ...

basin, and it is known as beloribitsa (literally meaning "the fish that is white" in Russian). The beloribitsa is now considered

extinct in the wild A species that is extinct in the wild (EW) is one that has been categorized by the International Union for Conservation of Nature as known only by living members kept in captivity or as a naturalized population outside its historic range due ...

, but survives in cultured stocks. The

nelma ''Stenodus nelma'', known alternatively as the nelma, sheefish, siifish, inconnu or connie, is a commercial species of freshwater whitefish in the family Salmonidae. It is widespread in the Arctic rivers from the Kola Peninsula (White Sea basin) ...

(''Stenodus nelma''), a more widespread species of Eurasian and North America, is sometimes considered its

subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...

Systematics

Alternatively, the name ''Stenodus leucichtys'' has been used in a broader sense, referring to a widespread species composed of two

. In addition to the landlocked subspecies ''Stenodus leucichthys leucichthys'', it comprises the

, ''Stenodus leucichthys nelma'' (

Pallas Pallas may refer to: Astronomy * 2 Pallas asteroid ** Pallas family, a group of asteroids that includes 2 Pallas * Pallas (crater), a crater on Earth's moon Mythology * Pallas (Giant), a son of Uranus and Gaia, killed and flayed by Athena * Pall ...

, 1773) which lives in Eurasian and North American rivers of the

Arctic The Arctic ( or ) is a polar regions of Earth, polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Canada (Yukon, Northwest Territories, Nunavut), Danish Realm (Greenla ...

basin. Nelma, also known as the

sheefish ''Stenodus nelma'', known alternatively as the nelma, sheefish, siifish, inconnu or connie, is a commercial species of freshwater whitefish in the family Salmonidae. It is widespread in the Arctic rivers from the Kola Peninsula (White Sea basin) ...

or inconnu, is currently often considered as a distinct species ''Stenodus nelma''. At a higher level, the genus ''Stenodus'' is not phylogenetically distinct from the broader lake whitefish genus ''

Coregonus ''Coregonus'' is a diverse genus of fish in the salmon family (Salmonidae). The ''Coregonus'' species are known as whitefishes. The genus contains at least 68 described extant taxa, but the true number of species is a matter of debate. The type ...

'', although it is phenotypically characterized by a specialized predator morphology.

Description and status

The fish has a large mouth with a protruding lower jaw and a high and pointed

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

. It is generally silver in color with a green, blue or brown back. The meat is white, flaky and somewhat oily. An adult fish weighs from . The fish eat

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

for their first year of life and then become

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

s of smaller fish. Beloribitsa used to inhabit particularly the

Volga The Volga (; russian: Во́лга, a=Ru-Волга.ogg, p=ˈvoɫɡə) is the List of rivers of Europe#Rivers of Europe by length, longest river in Europe. Situated in Russia, it flows through Central Russia to Southern Russia and into the Cas ...

Ural Ural may refer to: *Ural (region), in Russia and Kazakhstan *Ural Mountains, in Russia and Kazakhstan *Ural (river), in Russia and Kazakhstan * Ual (tool), a mortar tool used by the Bodo people of India *Ural Federal District, in Russia *Ural econ ...

and Terek rivers, and migrate up to upstream from the Caspian to their spawning grounds in the spring. Following the construction of dams and hydropower reservoirs, the migration and natural reproduction has been impeded, and the taxon is now considered as

by the

IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

. The stock however survives in hatcheries and some populations are maintained by stocking.

References

External links

''Stenodus leucichthys nelma''
Illustration of the sister species by N.N. Kondrakov. NOAA Photo Library. {{Taxonbar, from=Q855485 Stenodus Freshwater fish of the Arctic Fish described in 1772 Taxa named by Johann Anton Güldenstädt