The Chinese mitten crab大閘蟹,also known as the big sluice crab and Shanghai hairy crab上海毛蟹, is a medium-sized burrowing crab, named for its furry claws that look like mittens, that is native in the coastal estuaries of eastern Asia from Korea in the north to the Fujian province of China in the south. It has also been introduced to Europe and North America where it is considered an invasive species.
Mitten crabs spend most of their life in fresh water, but they must return to the sea to breed. During their fourth or fifth year in late summer, the crustaceans migrate downstream, and attain sexual maturity in the tidal estuaries. After mating, the females continue seaward, overwintering in deeper waters. They return to brackish water in the spring to hatch their eggs. After development as larvae, the juvenile crabs gradually move upstream into fresh water, thus completing the life cycle.