The virile crayfish, a highly aggressive non-native crayfish, is slowly invading waterways in East London. This unwanted visitor preys on native wildlife and spreads crayfish plague, a disease deadly to native white clawed crayfish.

The Environment Agency is tracking the progress of virile crayfish by installing small radio-transmitters on the backs of these environmental trouble-makers. Originally from North America, their spread is unabated by cold weather. They were first found on the River Lee near Enfield in 2004 and have since colonised over 17 kilometres of the river and connected waterways, spreading into Hertfordshire.

Preliminary results show that virile crayfish are moving upstream at a rate of 500 metres per month, substantially faster than their non-native cousin, the signal crayfish.

The UK’s only native crayfish, the white clawed crayfish, was wiped out along the River Lee following the invasion of the signal crayfish in the 1980s and the associated spread of crayfish plague. The Environment Agency’s work on the River Lee in Cheshunt will give a better understanding of the movement and lifecycle of the signal and virile crayfish. By better understanding the spread of virile crayfish, this work will contribute to efforts to safeguard native white clawed crayfish elsewhere in the country.Control of invasive species

Adam Ellis, Environmental Monitoring Officer at the Environment Agency said:

“Whilst rivers in England and Wales are cleaner than they have been for decades, there is still a lot to be done in order to return them to full health. This includes the control of invasive species like virile crayfish.

“By tracking the colonisation of the River Lee by virile crayfish, we will better understand how this species impacts the environment and our native wildlife. However, one of the most important ways to protect our wildlife is to stop the spread of non-native invasive species. We’re appealing to the public not to release unwanted pets into the wild.”

Invasive species cost UK £1.7 billion every year

Invasive species cost the UK economy an estimated £1.7billion every year. The rise of invasive species is a major challenge in meeting tough new EU targets on the ecology of rivers and lakes. Whilst otters, salmon and other wildlife returning to some watercourses for the first time since the industrial revolution, rivers that harbour non-native species could fall short of these tough new standards.