1 September 2010 Last updated at 20:37 ET

Fears over red crayfish 'invader' in London canal

Red swamp crayfish have been spotted in Regent's Canal in central London

Sightings of an invasive species of crayfish have prompted concerns by ecologists over its potential spread in the UK.

Red swamp crayfish, a native of the south-eastern United States, have been spotted in London's Regent's Canal.

Ecologists are concerned that the crustacean could cause harm to the native white-clawed crayfish.

A study has been started by King's College London into the creature's impact on other wildlife.

The white-clawed crayfish is a protected species in the UK.

Its numbers have already been reduced by the spread of the American signal crayfish, another invasive species which competes with and eats the indigenous crustacean.

'Essential' research

Red swamp crayfish have become established in mainland Europe in recent years.

In Europe, they have already had a significant negative impact on smaller indigenous crayfish and other wildlife and ecosystems.

The King's College study aims to build up a comprehensive picture of the red swamp crayfish's impact by catching and analysing crayfish species in Regent's Canal.

"I hope that my research project will improve our understanding of how different species of crayfish will interact," said Laura Cross, who is leading the study.

The research was welcomed by British Waterways, which manages the canal as part of a 2,200-mile (3,540km) network of waterways across the UK.

"It's essential that we understand the extent to which invasive species are colonising the canals and rivers we manage across the UK," said British Waterways ecologist Leela O'Dea.

Trapping crayfish on British Waterway's canals and rivers is normally strictly prohibited, and the organisation stressed that the public should not remove any without permission.