There are currently about 25,000 species of fish and, based on the number of new species being described each year, this total may eventually rise to about 29,000. However, less than 200 species of fishes occur in the Arctic.
In relative terms, the freshwater environment has more species per volume than the marine environment because the oceans make up 70 % of the Earth's surface, while inland waters make up only 1 %. But in the Arctic, the situation is reversed. Of the 200 or more so arctic fishes, only a dozen breed in freshwater.