Page last updated at 00:25 GMT, Thursday, 14 August 2008 01:25 UK

'Dirty dozen' threaten waterways

Red-eared terrapin
The red-eared terrapin is a threat to birds' eggs and insect larvae

A "dirty dozen" of the 12 non-native species most likely to harm native wildlife along rivers has been highlighted by British Waterways.

They include red-eared terrapins which were introduced after the Teenage Mutant Ninja Turtle craze of the 1990s.

Zander, mink, American signal crayfish, giant hogweed, floating pennywort and Japanese knotweed are also on the list.

British Waterways urged people to think about the environmental impact of releasing such species into the wild.

American signal crayfish
Australian swamp stonecrop
Chinese mitten crab
floating pennywort
giant hogweed
Himalayan balsam
Japanese knotweed
red-eared terrapin
water fern
zebra mussels

Invasive species can cause problems because they are normally bigger, faster growing or more aggressive than native ones and are often resistant to traditional methods of control.

The organisation spends 1m a year dealing with the problems caused by such species.

Its national ecologist Chris John said: "Whilst not all non-native species are harmful, many pose real problems to our native wildlife, to boaters and to our historic channels, locks and bridges.

"With no natural predators to control them they can overwhelm wildlife, channels, banks and towpaths.

Mink are often mistaken for otters but are smaller and far more aggressive

He added: "British Waterways invests a large amount of time and money to protect our canals and rivers through identifying, monitoring and controlling damaging species.

"This is very costly and diverts resources that could be used elsewhere on the waterway network.

"We are therefore asking people to help us by disposing of non-native plants safely and carefully selecting alternative plants for gardens, ponds and aquariums."

Waterways 'have the golden touch'
29 Oct 07 |  Science & Environment
Volunteers gather to fight weeds
26 Jul 08 |  Bristol/Somerset

The BBC is not responsible for the content of external internet sites

Has China's housing bubble burst?
How the world's oldest clove tree defied an empire
Why Royal Ballet principal Sergei Polunin quit


Americas Africa Europe Middle East South Asia Asia Pacific