Arctic cisco is an anadromous species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of freshwater whitefish

Freshwater whitefish

The freshwater whitefish are fish of the subfamily Coregoninae in the salmon family Salmonidae. Along with the freshwater whitefish, the Salmonidae includes the freshwater and anadromous trout and salmon species as well as graylings...

 that inhabits the Arctic

Arctic

The Arctic is a region located at the northern-most part of the Earth. The Arctic consists of the Arctic Ocean and parts of Canada, Russia, Greenland, the United States, Norway, Sweden, Finland, and Iceland. The Arctic region consists of a vast, ice-covered ocean, surrounded by treeless permafrost...

 parts of Siberia

Siberia

Siberia is an extensive region constituting almost all of Northern Asia. Comprising the central and eastern portion of the Russian Federation, it was part of the Soviet Union from its beginning, as its predecessor states, the Tsardom of Russia and the Russian Empire, conquered it during the 16th...

, Alaska

Alaska

Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...

 and Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

. It also has a close freshwater relative in several lakes of Ireland

Ireland

Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...

, known as the pollan

Coregonus pollan

The pollan or Irish pollan is a freshwater whitefish that is known only from five Irish lakes, Lough Neagh, Lower Lough Erne, Lough Ree, Lough Derg and Lough Allen....

, alternatively regarded as conspecific with it, or as a distinct species.

The freshwater omul

Omul

The omul, Coregonus migratorius, also known as Baikal omul , is a whitefish species of the salmon family endemic to Lake Baikal in Siberia, Russia. It is considered a delicacy and is the object of one of the largest commercial fisheries on Lake Baikal...

 of Lake Baikal

Lake Baikal

Lake Baikal is the world's oldest at 30 million years old and deepest lake with an average depth of 744.4 metres.Located in the south of the Russian region of Siberia, between Irkutsk Oblast to the northwest and the Buryat Republic to the southeast, it is the most voluminous freshwater lake in the...

, formerly considered a subspecies

Subspecies

Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...

 Coregonus autumnalis migratorius of the Arctic cisco, has no close genetic relationship to it, and is now classified as a separate species Coregonus migratorius.