The Japanese mitten crab (Eriocheir japonica), is a species of crab native to Korea and Japan. It is catadromous, being usually found in freshwater and brackish environments, but moving downstream into coastal marine environments to breed. 
It is commonly eaten and economically important in its native range.
Distribution.
The species is found in Japan, Korea, western Taiwan and the southeastern coast of Russia. Sporadic introduced populations are also present in the United States, and a degree of introgression of the species has occurred in the invasive European populations of its close congener, the Chinese mitten crab.