Chinese mitten crab

Eriocheir sinensis


Photo credit: ©The Food and Environment Research Agency (Fera)
Eriocheir sinensis
  • It spends most of its life in rivers, but must migrate to the sea to breed. Once the crabs have mated the males are thought to die, leaving the females to brood the eggs. In the spring the eggs hatch into larvae and after about six to seven weeks these metamorphose into juvenile crabs, which then migrate back up the river into freshwater to complete the life cycle.

  • The Chinese Mitten Crab is very distinctive crab, light brown in colour, with hair growing on equal sized claws that are often referred to as ‘mittens’. It is currently the only crab to live in freshwater in Ireland and Britain and therefore may have significant impacts on the functioning of this environment. This species is also able to migrate across land unlike all other crab species in Ireland. Mitten Crab are an intermediate host for the mammalian lung fluke Paragonimus ringer, known to infect humans. They burrow into river banks causing holes about 3 cm in diameter. Dead bodies (carapaces) may be found though positive identification would require the mittens to be present.

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Origin and Distribution:
  • The species is originally from Asia where it is considered a delicacy in local cuisine. Now found in Europe, where it invaded nearly a century ago, Mitten crabs have now spread to North America. For reasons that are not understood, the populations of mitten crabs in England and North America did not at first expand like those in mainland Europe, but numbers are currently rising, prompting concern.

  • When population densities are high, the species causes considerable damage to soft sediment banks through burrowing which increases erosion and might affect flood defences. This has been documented in Europe and North America. In Ireland there is concern that the species may impact on the native and endangered White Clawed Crayfish as well as fish species such as the protected Twaite Shad fish.
  • Additional negative impacts, such as loss of biodiversity and recruitment of commercial species are expected. There are economic impacts associated with introduction of this species. To date, in Germany, the species is known to have cost at least 80 million Euro in monetary value. The Mitten Crab is also an intermediate host for the mammalian lung fluke Paragonimus ringer, known to infect humans.

Is it found in Northern Ireland?
  • It has not been recorded in Northern Ireland.
  • Further distribution information can be found on the NBN Atlas NI.

It has been recorded in neighbouring Ireland:
  • Recorded on three occasions in Ireland in Waterford estuary.
  • One individual in 2006, 16 crabs in 2009 and one berried female with eggs showing signs of development to Zoea stage, was captured by net on 25th January 2021 in Waterford harbour.
  • Another female was photographed 25th December 2020.
  • See Invasive Species Alert from Biodiversity Ireland for further details.

How did it get here?
    • It is unclear at present how exactly the Chinese Mitten Crab arrived in Ireland. Likely vectors for introduction include ship ballast water and hull fouling. Other human mediated vectors such as a hitchhiker in aquaculture such as in seed mussel imports, the live food trade and smuggling may be possible as the mitten crab is a delicacy.

You can help by reporting any sightings: @ the Centre for Environmental Data & Recording (CEDaR) - Or via the iRecord App.
Prevent Spread
  • Do not introduce to new sites
  • Inspect all aquaculture imports
  • Clean all equipment before moving between waterbodies
  • Do not move water from one body to another
  • Report all sightings

Further Resources:
Current Legislative Position (Listed on 03 August 2016)
  • This species must not intentionally be brought into the Union; kept; bred; transported to, from or within the United Kingdom, unless for the transportation to facilities in the context of eradication; placed on the market; used or exchanged; permitted to reproduce, grown or cultivated; or released into the environment.
For further queries, you can contact the Invasive Non Native Species (INNS) Team in the Northern Ireland Environment Agency on 028 9056 9558 or Email:  

Species Related Files:

Invasive Species Northern Ireland

Invasive Species Northern Ireland