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Chinese Mitten Crab Invasion for Northern Waterways

Chinese mitten crabs are set to cause devastating problems for Britain’s environment, North East scientists are warning.

The crabs, which were brought to the UK during the last century in ships’ ballast water, are considered a threat because they prey on protected UK native species such as the white-clawed crayfish and salmon eggs and fry.

They also settle in river banks, burrowing into them and riddling them with holes up to half a metre long, which may eventually cause the bank to collapse. Scientists from the University of Newcastle upon Tyne have been carrying out the first comprehensive modelling of the crab’s migration through Europe and the UK, and have found that the crabs migration is most marked along the east coast northwards to the River Tyne and on the south coast westwards to the River Teign.

The scientists predict that the mitten crab - so called because its claws are coated with small clumps of dark brown fur, or mittens - has the potential to establish itself in all major UK estuaries in several years time. Dr Bentley, of Newcastle University’s School of Marine Science and Technology said: “With most invasive species, such as the grey squirrel, the problem is not recognised until it is too late to do anything and you can not eliminate it without taking drastic environmental measures.”

Options for controlling the crabs, suggested by the scientists, include a public awareness campaign where anglers and other users of rivers and the coastline are encouraged to report sightings of crabs. Measures which are currently used to monitor fish in our rivers - such as electrical fish counters - could also be adapted to include monitoring of mitten crabs. Chinese mitten crabs are about the size of a dinner plate when the legs are fully extended, and are a delicacy in Chinese and Japanese cuisine. Almost all crabs found in UK freshwater are likely to be Chinese mitten crabs.

This was posted in Bdaily's Members' News section by Ruth Mitchell .