The Arctic char or Arctic charr (Salvelinus alpinus) is a cold-water fish in the family Salmonidae, native to alpine lakes and arctic and subarctic coastal waters. Its distribution is Circumpolar North. It spawns in freshwater and populations can be lacustrine, riverine, or anadromous, where they return from the ocean to their fresh water birth rivers to spawn. No other freshwater fish is found as far north; it is, for instance, the only fish species in Lake Hazen on Ellesmere Island in the Canadian Arctic. It is one of the rarest fish species in Great Britain and Ireland, found mainly in deep, cold, glacial lakes, and is at risk from acidification. In other parts of its range, such as the Nordic countries, it is much more common, and is fished extensively. In Siberia, it is known asgolets (Russian:голец) and it has been introduced in lakes where it sometimes threatens less hardy endemic species, such as the small-mouth char and the long-finned char in Elgygytgyn Lake.