The UK spread was most marked along the east coast northwards to the River Tyne and on the south coast westwards to the River Teign.
Dr Matt Bentley, one of the research team*, said: "The pattern of the spread in the UK since the 1970s mirrors the spread in mainland Europe and in the Baltic region which experienced an major outbreak. This is a fairly good indication that the UK is set for a similar situation."
Mitten crabs can be found in the sea or rivers because they are catadromous - meaning they mainly live in freshwater but must migrate to the sea to breed. Their potential for widespread colonisation is increased by the fact they can cross dry land and can migrate up to 1,000km while growing to adult size.
A decrease in river pollution and a prolonged period of drought in the late 1980s - which together improved habitat conditions for mitten crabs - are potential reasons for the recent population rise.
Dr Bentley, of Newcastle University's School of Marine Science and Technology added: "This study demonstrates the importance of a monitoring programme for the mitten crab, even if its appearance is just a rare occurrence in an estuary. Records demonstrate the crab's ability to rapidly expand once the local population reaches a critical density and or conditions become favourable.
"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.
"This study shows there is a need for a monitoring system for the mitten crab which could help manage the spread at an early stage. Low cost options could 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 the electri
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Contact: Dr Matt Bentley
m.g.bentley@ncl.ac.uk
44-191-222-5350
University of Newcastle upon Tyne
7-Feb-2006