The Tokyo bitterling (''Tanakia tanago'') is a temperate

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...

fish of the carp family (

Cyprinidae Cyprinidae is a family of freshwater fish commonly called the carp or minnow family. It includes the carps, the true minnows, and relatives like the barbs and barbels. Cyprinidae is the largest and most diverse fish family and the largest verte ...

). Taxonomically, it belongs to the subfamily Acheilognathinae. The species was first described as ''Rhodeus tanago'' by Shigeho Tanaka in 1909. It is widely known as ''Tanakia tanago'',''Tanakia tanago''. Catalog of Fishes. California Academy of Sciences
. 27 August 2014. accessed 4 Oct 2014 although a 2014 study suggests it is genetically distinct from other '' Tanakia'' species, and warrants placement it the monotypic genus ''Pseudorhodeus''.

Distribution

In the wild, this fish is found only on the Kantō Plain of

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

, an area near the capital city, Tokyo. The fish was formerly abundant in small streams, but its habitat has been overrun by people and pollution.

Threats

There is a real risk that it could become extinct in the wild. It also suffers from competition from the related but more aggressive rosy bitterling. Bitterlings lay their eggs in freshwater mussel shells. The Tokyo bitterling lays its eggs in only one type of mussel shell, limiting its chances of successful breeding. To help protect the fish, it has been declared a "national monument" by the

Japanese government The Government of Japan consists of legislative, executive and judiciary branches and is based on popular sovereignty. The Government runs under the framework established by the Constitution of Japan, adopted in 1947. It is a unitary state, c ...

, and this gives it special protection.

References

Tanakia Natural monuments of Japan Freshwater fish of Japan Endemic fauna of Japan Fish described in 1909 Taxa named by Shigeho Tanaka {{Acheilognathinae-stub