Rivers at risk from march of the 'Mandelson' crab

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The Independent Online

The Chinese mitten crab's predatory habits once led John Prescott to compare it to his Labour Party colleague Peter Mandelson, another creature with fearsome claws and a tendency to approach its prey sideways on.

Mr Mandelson's influence has spread in the eight years since - but not nearly so dramatically as that of the crab, according to research by the University of Newcastle. The mitten crab is now rampant throughout Britain's coast and rivers and could cause devastating environmental problems if populations are not monitored and controlled, the university's scientists say. Able to walk for miles overland, the crab has taken over the Thames and Medway estuaries and colonised rivers as far north as the Tyne and west into Devon.

The study, which is the first comprehensive modelling of the crab's migration through Europe and the UK, demonstrates how the mitten crab - so called because its claws are coated with small clumps of dark brown fur - has the potential to establish itself in all major UK estuaries over the coming years. From 1997 to 1999 the spread along the coast was 448km (278 miles) per year - nearly six times the average spread of 78km per year from 1976 to 1999. In rivers, the increased spread from 1995 to 1998 was 49km per year, compared with 16km per year from 1973 to 1998.

The spread of the mitten crab (Eriocheir sinensis, from the Greek meaning "wool hand of the Chinese") was most marked along the east coast northwards to the river Tyne and on the south coast westwards to the river Teign. Hundreds of thousands have spread up the Thames, out-eating native white-clawed crayfish, preying on salmon eggs and fry and weakening river banks and canals by burrowing into the soil.

When they settle in a river bank, they riddle them with bore holes up to half a metre long which may eventually cause the bank to collapse. Some experts claimed they were undermining the Millennium Dome several years ago after spotting scores of holes in the banks of the Thames near by.

"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," said Matt Bentley, of Newcastle University's School of Marine Science and Technology.

The study recommends that a nationwide monitoring and trapping system for the crab should be introduced before it is too late to control the population.

Scientists from the Natural History Museum recommend the more radical solution of eating the crab. It is a delicacy in the Far East, commanding high prices in restaurants in Japan and Hong Kong. It is flown to London by the crate-load for the capital's Chinese restaurants, which pay importers £6 a pound.