The alien Chinese mitten crab, Eriocheir sinensis (Crustacea : Decapoda : Brachyura), in the Thames catchment

Eriocheir sinensis, the Chinese mitten crab, is a native of east Asia and p redominantly lives in freshwater but migrates seawards to breed. In 1912 a specimen was collected in the River Aller, a tributary of the Weser, German y and now this exotic species has a European distribution from Finland to t he Atlantic coast of southern France. In the UK, the mitten crab has been r eported from the Humber, Medway and Thames catchments. Although the populat ion in Thames had remained low, recent evidence suggests it is increasing, which has potential environmental implications.