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Conservation & the Environment

Non-Native Crayfish Tracked

The Environment Agency is using radio transmitters to locate and track a ferocious predator invading English waterways.

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

Invasive species cost the UK economy an estimated £1.7bn 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 water- courses for the first time since the industrial revolution, rivers that harbour non-native species could fall short of these tough new standards.

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 the UK economy an estimated

£1.7billion every year.

The public is urged to help prevent the spread of invasive species by not dumping pets or aquatic plants in the wild. Waterways users, such as canoeists and fishermen, should to ‘Check, Clean and Dry’ their equipment to help prevent the spread of invasive species such as killer shrimp and crayfish plague between waterways.

Key facts about virile crayfish:

Home country: North America and Canada. UK distribution: So far, the virile crayfish has only been found East London, along and around the River Lee. European strong holds: There is just one other known European population of virile crayfish in the Netherlands. Method of invasion: It is believed that virile crayfish arrived in the UK after an aquarium owner released these beasts into an East London pond. Vital statistics: Maximum length, 14cm; Number of eggs per female, 490; Lifespan, four years. Impact on native species: The virile crayfish out-competes native white- clawed crayfish for food, preys on fish eggs and spreads crayfish plague.cts Regulations 2006

Tackling Invasive Weeds with Salt Water

and reduce its value for birds, and the lagoons could be a source to spread the weed to other places in the Conwy Valley.”

The RSPB is using salt water to tackle invasive weeds in the Conwy lagoons at Llandudno Junction. Three large pumps will bring seven million gallons (32 million litres) of saltwater into one of the lagoons, from the River Conwy, during next weekend’s high tides (8-10 March). The huge change, jointly funded by RSPB Cymru, Environment Agency Wales and the Countryside Council for Wales (CCW), is designed to eradicate an invading weed from Australia, known as Swamp Stonecrop or Crassula helmsii. Dave Thorpe, Environment Agency Wales’ Biodiversity Technical Specialist, said: “If we don’t undertake this work, Crassula could smother the mud

RSPB Conwy includes part of the estuary, providing a convenient source of saltwater. The saltwater will be kept in the lagoon for at least a year -salt is the one thing known to kill the Crassula plant. The project will provide RSPB with the opportunity to assess how undertake similar measures could be undertaken within the much larger adjacent lagoon. Dr Neil Smith, from CCW, said “It is not known how the weed arrived at the reserve, but it is widely imported on aquatic plants bought for garden ponds. It is sold as an oxygenating weed, but is thought to be causing millions of pounds worth of damage to wildlife sites across Wales, and elsewhere in northwest Europe”. This is thought to be only the second time that seawater has been used to tackle Crassula helmsii in the UK. It has previously been used successfully at the RSPB’s Old Hall Marshes reserve in Essex.

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