Eriocheir sinensis

Phylum: Crustacea
Class: Eumalacostraca
Order: Decapoda
Species name: Eriocheir sinensis H. Milne Edwards 1854
Synonyms: None
Common name: Chinese mitten crab
 
Date of introduction and origin
Eriocheir sinensis was most likely introduced from the Low Countries of Europe. It was first collected in Germany in 1912 (Clark 1986). The date of introduction to Britain is thought to be 1935 and this species was first introduced into the Thames at Chelsea in Greater London (Ingle 1986) and later to the Humber catchment in Yorkshire. This species' natural range is south-east Asia where it is found from China (26·N) to the Korean Peninsula (40·N) and Japan.
 
Method of introduction
This species may have been introduced by transport of small crabs or larvae in ballast water or through transport of adult crabs clinging to ships' hulls. Introduction may have been associated with scrap-metal yards on the Thames and Medway in Essex, and barges from the continent (P.F. Clark pers. comm.).
 
Reasons for success
Unknown.
 
Rate of spread and methods involved
Its dispersal is likely to be through pelagic larvae and mobile adults; the rate of spread is not known.
 
Distribution
In Britain this species occurs in the Humber, Thames and Medway estuaries (Clark 1986). It has also been reported specifically from the River Ancholme, a tributary of the Humber since 1976, and the River Wharfe and River Ouse in Yorkshire since 1986, where it is caught in nets laid by eel fishermen (B. Helmsley-Flint pers. comm.). European populations can be found from Finland to France (Ingle 1986).
 
Factors likely to influence spread and distribution
Currents may take the larvae onto the coasts of Europe. This species may be preyed on by pike Esox lucius, eels Anguilla anguilla and brown trout Salmo trutta (P.F. Clark pers. comm.). Limited reproductive success may be a limiting factor to its spread in Britain.
 
Effects on the environment
For most of its life E. sinensis lives in fresh water. During August adult crabs migrate seawards and gather in large swarms to breed in estuaries (Panning 1939). When population densities are high, E. sinensis causes considerable damage to soft sediment banks through burrowing which increases erosion and might affect flood defences. This species is an intermediate host for the mammalian lung fluke Paragonimus ringer.
 
Effects on commercial interests
It may damage the nets of eel fishermen. Damage caused to river banks may increase repair costs.
 
Control methods used and effectiveness
Those caught in eel nets are destroyed. It may be possible to use biological control through maintenance of fish populations leading to increased predation.
 
Beneficial effects
Parasite-free individuals, have a small commercial value: In the Japanese restaurant market E. sinensis was worth £20/kg in 1995.
 
Comments
Increases in population in the Thames in recent years may be attributable to drought conditions during 1989-1992 having facilitated greater settlement of young crabs (Atrill & Thomas in press). Adults occupy an essentially freshwater habitat but must migrate to mate and release larvae in the saline mouths of estuaries, congregating as they do so. Young crabs in turn migrate up estuaries (Barnes 1994).
 
References
Atrill, M.J., & Thomas, M.R. In press. Long-term distribution patterns of mobile estuarine invertebrates in relation to hydrological parameters. 30th European Marine Biology Symposium, September 1995.
 
Barnes, R.S.K. 1994. The brackish-water fauna of northwestern Europe. Cambridge, Cambridge University Press.
 
Clark, P.F. 1984. Recent records of alien crabs in Britain. Naturalist, 109: 111-112.
 
Clark, P.F. 1986. North-east Atlantic crabs: an atlas of distribution. Ross-on-Wye, Marine Conservation Society.
 
Hayward, P.J., & Ryland, J.S. eds. 1990. The marine fauna of the British Isles and north-west Europe. 2 vols. Oxford, Clarendon Press.
 
Ingle, R.W. 1986. The Chinese mitten crab Eriocheir sinensis H. Milne Edwards - a contentious immigrant. The London Naturalist, No. 65:101-105.
 
Panning, A. 1939. The Chinese mitten crab. Report of the Board of the Regents of the Smithsonian Institution (Washington) (1938), 361 - 375 plus 9 plates. (publication 3508.)
 
Acknowledgements (contributions from questionnaire)
P.F. Clark, Natural History Museum, London.
B. Helmsley-Flint, The Environment Agency, Northumbria and Yorkshire Region.