Rhithropanopeus harrisii

Phylum: Crustacea
Class: Eumalacostraca
Order: Decapoda
Species name: Rhithropanopeus harrisii (Gould, 1841)
Synonyms: Pilumnus harrisii Gould 1841, Pilumnus tridentatus Maitland 1874, Heteropanope tridentata Tesch 1922.
Common name: Zuiderzee crab, dwarf crab
Date of introduction and origin
Rhithropanopeus harrisii was first found in Roath Docks, Cardiff, South Wales, in 1996. It is not known where the introduction came from, although this species is native to the east coast of the American continent from New Brunswick to north-east Brazil (Christiansen 1969).
Method of introduction
The method of introduction to Britain is unknown but was probably in association with ships, possibly in ballast water or clinging to hulls. Ships arrive in Cardiff Docks from all over the world, including coal barges from the U.S.A. It was first observed in Europe in the Zuiderzee, The Netherlands and Christiansen (1969) consider it probably arrived in the ballast or on the hulls of ships.
Reasons for success
Its reason for success is unknown. However, the dock water in which Rhithropanopeus harrisii has been found is of low salinity (about 12%o).
Rate of spread and methods involved
Rhithropanopeus harrisii spread through much of continental Europe between the 1870s and 1950s (Christiansen 1969). However, it has only very recently arrived in Britain. Its spread in Britain is unknown, and so far it has not been found outside Cardiff Docks. Its spread is probably associated with shipping.
In Britain this species has only been recorded as established throughout Cardiff Docks. Elsewhere in Europe it is found in Denmark, Belgium, The Netherlands (where it is much less common than previously), Poland, West Germany and France, and in Russia, Romania and Bulgaria - from the Black and Caspian Seas and also in the Sea of Azov (Christiansen 1969).
Factors likely to influence spread and distribution
Shipping routes are likely to affect the spread and distribution of this species.
Effects on the environment
Effects on commercial interests
Control methods used and effectiveness
None used.
Beneficial effects
None known.
Cardiff Docks harbour other non-native species, including the tube worm Ficopomatus enigmaticus, with which R.. harrisii may associate, possibly on trophic levels.
Ingle, R.W. 1980. British crabs. London & Oxford, British Museum (Natural History) & Oxford University Press.
Christiansen, M.E. 1969. Marine invertebrates of Scandinavia. No. 2 Crustacea, Decapoda, Brachyura. Oslo, Universitetsforlaget.
Acknowledgements (contributions from questionnaire)
Dr C. Mettam, University of Cardiff.
P.F. Clark, Natural History Museum, London.