Fish that live only in fresh water. Many families and orders of fish are considered to include only primary freshwater species, i.e. species that evolved without contact with a marine environment. Some families have a world-wide distribution, e.g. the Cyprinidae are found in freshwater basins all over the world, except for S. America and the Australian region. Others, e.g. the Cobitidae (loaches), are found only in the Eurasian region. A few families have a very restricted distribution, e.g. the Amiidae (bowfin) are found only in the eastern half of the USA.
Subjects: Ecology and Conservation — Zoology and Animal Sciences.