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Dwarf crab, Rhithropanopeus harrisii


Short description of Rhithropanopeus harrisii, Dwarf crab

A small, brown to olive green crab; the carapace is up to 26 mm wide and has four spines on each side.  The four pairs of walking legs are long, slender and hairy.  One claw is always larger than the other and both have white tips.

Description of Rhithropanopeus harrisii, Dwarf crab status in GB

The dwarf crab was first found in Roath docks, Cardiff in 1996.  No other GB records to date. 

Habitat summary: Rhithropanopeus harrisii, Dwarf crab

The dwarf crab can tolerate a wide range of salinities from 0.5 to 38 psu, but prefers the brackish water of estuaries and lagoons.  It commonly inhabits shallow subtidal waters with muddy/sandy substrate, oyster reefs, shoreline vegetation and debris among which it can hide. 

Overview table

Environment: Marine and Freshwater
Species status: Non-Native
Native range: Mexico, Eastern United States Temperate, Eastern United States Tropical, South Eastern Canada, North East United States, Far East United States
Functional type: Predator
Status in England: Non-Native
Status in Scotland: Non-Native
Status in Wales: Non-Native
Location of first record: Cardiff docks
Date of first record: 1996

Distribution map

Map of the UK with areas shaded to show the UK distribution of Dwarf crab

GB Distribution from NBN Atlas

Author's name:

Natalie Sweet

Last updated:

October 3rd 2019

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