Chinese Mitten Crab

• GeneralIts hairy claws look like mittens; it migrates from the river to the sea to breed.
• It is on the IUCN list of the 100 most damaging invasive alien species in the world.
• Its burrows dug into the banks destabilise slopes, dykes and canals, at repair costs running into the millions.
• It can travel more than a thousand kilometres upriver from the estuary and get around obstacles by walking overland.
• It is catadromous, which is unusual in a crab: it spends almost its whole life in fresh water and returns to the sea only to breed, after which it dies.
• It owes its name to the dense bristles covering its claws, which look like mittens.
• It invaded northern Europe in the early twentieth century and San Francisco Bay much later; the most likely vector is ships' ballast water.
• The economic damage comes mainly from its burrows, which destabilise banks and dykes, and from its mass migration, which interferes with fishing, irrigation and even power stations.
• It can carry the crayfish plague pathogen.
• It is an intermediate host of the fluke Paragonimus: eating it undercooked can infect people.

Habitat & environment

Estuaries, rivers and canals

Sexual maturity

1-3 years

Sources consulted: IUCN Global Invasive Species Database; Rudnick et al. (2003); Herborg et al.; US Fish and Wildlife Service