Taxonomic name: Eriocheir sinensis (Milne-Edwards, 1854)
Synonyms: Eriocheir japonicus de Haan, Eriocheir leptognathus Rathbun, Eriocheir rectus Stimpson
Common names: Chinese freshwater edible crab (English), Chinese mitten crab (English), chinesische wolhandkrab (Dutch), chinesische wollhandkrabbe (German), crabe chinois (French), kinesisk ullhandskrabba (Swedish), kinesiske uldhandskrabbe (Danish), kinijos krabas (Lithuanian), kitajskij mokhnatorukij krab (Russian), krab welnistoreki (Poland), kraba welnistoreki (Polish), villasaksirapu (Finnish)
Organism type: crustacean The Chinese mitten crab (Eriocheir sinensis) is a migrating crab which has invaded Europe and, more recently, North America. It contributes to the local extinction of native invertebrates and modifies habitats. As well as causing erosion by its intensive burrowing activity, the crab may cost fisheries and aquaculture industries several of hundreds of thousands of dollars per year by stealing bait and feeding on trapped fish. The female carries 250,000 to 1 million eggs and control strategies such as electrical screens have failed to prevent crab migration. Description
The main identifying features of Eriocheir sinensis are a light brown colour, hairy claws with white tips (normally equal in size) which make the crab appear to be wearing "mittens", a smooth round carapace or body shape, a notch between the eyes, four lateral carapace spines (fourth spine is small), and a maximum carapace width of approximately 3 inches (80mm). The legs of the adult crab are generally more than twice as long as the carapace width (EATM 1999; Washinton Sea Grant Program 2000). Similar Species
Eriocheir japonicus, Eriocheir leptognathus, Eriocheir rectus
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Occurs in:
estuarine habitats, lakes, riparian zones, water courses, wetlands Habitat description
Eriocheir sinensis tolerates a wide range of abiotic conditions. It is found in temperate climates around the world. However the temperature range within these regions is large and laboratory studies indicate the crab is able to tolerate a wide range of temperatures. The Chinese mitten crab has exhibited a remarkable ability to survive in highly modified aquatic habitats, including polluted waters (Rudnick A. Deborah et al. 2003). It reproduce in the brackish waters of estuaries. General impacts
In Britain zoologists fear that the Chinese mitten crab could both eat and out-compete vulnerable freshwater species (Owen 2003). Because there isn't already a freshwater crab in Britain, species like the native crayfish (which is already in decline) are likely to be affected. Since the early 1990s numbers of the crab have mushroomed. The crab, which can travel over dry land, has now spread to many other English rivers. Furthermore there is a lot more available habitat for the crab to invade, increasing its potential for invasiveness in Britain.
The Chinese mitten crab impacts freshwater and estuarine ecosystems on a number of levels; it has an opportunistic diet including algae, detritus, and a variety of macroinvertebrates (Panning 1939; Hoestlandt 1948; Gollasch 1999; Rudnick et al. 2003). Juvenile crabs form dense colonies and create burrows in the intertidal portions of streams, a process which has undermined the integrity of stream banks in both Europe and the USA (Peters and Panning 1933; Dutton and Conroy 1998; Rudnick et al. 2003).
The introduced Chinese mitten crab may have a number of economic impacts. The monetary impact caused by this invader in German waters totals to approximately 80 million Euro since 1912 (Financial impacts). Additional negative impacts in Germany, such as impacts on biodiversity, recruitment of commercial species, and erosion rates are known but cannot be easily quantified (Gollasch 2005, in preparation). It steals bait and damages fishing gear which hinders commercial and recreational fishing (Panning 1939; Rudnick and Resh 2002). Crabs may also feed on trapped fish in commercial aquaculture ponds. In California, adult crabs have become a major nuisance to anglers, taking a variety of baits including ghost shrimp and shad (Washington Sea Grant Program, 2000). Chinese mitten crabs may also block water intakes in irrigation and water supply schemes (Ministry of Fisheries Undated). In California, the Chinese mitten crab has disrupted water diversion plants with large numbers of downstream-migrating crabs becoming trapped in holding tanks meant to keep fish out of turbines. This has caused fish mortality and high costs are needed to prevent the crabs entry (Siegfried 1999).
Lastly, the Chinese mitten crab may carry a lung fluke that infects humans (Ministry of Fisheries Undated). The mitten crab is the secondary intermediate host for the Oriental lung fluke, with mammals, including humans, and the final host. Humans can become infested by eating raw or poorly cooked mitten crabs. However, neither this human parasite nor its primary snail host have been found in California (EATM 1999). Uses
The Chinese mitten crab is a culinary delicacy in Asia and supports a $1.25 billion per annum aquaculture industry in China (Herborg et al. In Press 2005). Crabs have been used as bait for eel fishing, to produce fish meal, cosmetic products and as fertilizer in agriculture. Notes
The Chinese mitten crab was given its intriguing name because its large claws, covered by soft bristles, resemble mittens. Its scientific name Eriocheir sinensis is derived from the Greek and means means 'wool hand, Chinese' (The Natural History Museum 2005). To see a picture of these unique "mittens" please visit Chinese Mitten Crabs.
The taxonomy of Eriocheir sinensis is still under debate. Recent work by Zhao and collegues (2002) has suggested that the following four species be considered in Eriocheir: sinensis, japonicus, leptognathus, formosa. Geographical range
Native range: The Chinese mitten crab originates, unsurprisingly, from China with a native distribution in the province of Fukien, China (~26°N northwards to the Korean Peninsula ~40°N).
Known introduced range: Its present estimated distribution ranges from Finland through Sweden, Russia, Poland, Germany, the Czech Republic (Prague), the Netherlands, Belgium, England and France. The southernmost Atlantic coast record is the Portugal, but the crab has extended its range via the Garonne canal system to Sigean, Languedoc-Roussillon, southern France. The crab has also been reported from North America with reports from the Detroit River and Great Lakes (without establishment) as well as an isolated occurrence from Hawai‘i. Recent evidence suggests that the population in San Francisco bay is steadily on the increase (NHM). Introduction pathways to new locations
Live food trade: The mitten crab is a delicacy and crabs have been imported live illegally to markets.
Natural dispersal: The invasion potential of this crab may be enhanced by its reproductive strategy, which utilizes the dispersion of planktonic larvae to colonize new areas (Kobayashi. S., pers.comm., 2003).
Ship:
Ship ballast water: A likely method of introduction is accidental release via ballast water
Ship/boat hull fouling: Some specimens in empty ""shells"" of cirripeds have been reported on a ships hull.Fouling communities are typically composed of encrusting or sessile species, however they can include mobile species. This vector can introduce species through a variety of means.
Smuggling: The mitten crab is a delicacy and crabs have been imported live illegally to markets. Management information
Control of this species may be difficult because of its abundance, ubiquity, high reproductive rate, and wide range of physiological tolerances (Deborah et al. 2003).
The physical trapping of crabs has not been sufficient to mitigate the damage caused by crabs. In order to prevent the migration of the crab up rivers in Germany electrical screens were installed on the river bottom in the 1930-40’s and pulses 30-40 times per minute were used to disable and kill the crabs but this method of control met with little success (McEnnulty et al. 2001).
Alternatively, zoologists at the Natural History Museum in London, England have suggested (in the Biologist) that commercial fishermen should be called upon to target this species and send it back to China where it is a prized culinary ingredient (Owen 2003). The export of British-caught mitten crabs could help to take the pressure off native plants and animals at risk from the advancing invaders. Nutrition
The Chinese mitten crab is an omnivore. Juveniles primarily eat vegetation. As they mature, they increasingly prey upon small invertebrates including worms and clams (Washington Sea Grant Program 2000). Reproduction
Mitten crabs have been reported to take between 1 and 5 years to attain sexual maturity, with shorter time frames reported from aquaculture populations in southern China (Zhang et al. 2001), and longer time periods of 4-5 years reported from Germany (Panning 1939). The females carry 250,000 to 1 million eggs until hatching, and both sexes die soon after reproduction. Lifecycle stages
This sizeable crab 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 (The Natural History Museum 2005). 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 Natural History Museum 2005). In China's Yangtze River, mitten crabs have been reported 800 miles upstream from the Yellow Sea (Washington Sea Grant Program 2000). This species has been nominated as among 100 of the "World's Worst" invaders Reviewed by: Major update under progress
Dr. Stephan Gollasch, Institute of Marine Research, Duesternbrooker, Germany.
Compiled by: Dr. Stephan Gollasch, Institute of Marine Research, Duesternbrooker, Germany & IUCN/SSC Invasive Species Specialist Group (ISSG)
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Last Modified: Monday, 3 April 2006
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