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content@managingwater.co.uk Conservation & the Environment Beetles help to control invasive water plant


Thousands of tiny weevils are to be released into a river near Boston, Lincolnshire, to reduce the volume of azolla, also known as the fairy or water fern, growing there.


Azolla is an ultra-fast growing plant which can double in size every four to five days. It can quickly form dense mats up to 30cm thick.


Above: An Azolla eating weevil


Below: Azolla, which can double in size every four to five days.


Debbie Sylvester, Environment Agency, Operations Delivery Team Leader, said: “Azolla grows extremely quickly and can completely cover the water’s surface. These weevils eat


only this plant and should help to control its spread.”


Azolla is extremely invasive and difficult to control because of its fast growth rate and ability to regrow from the tiniest fragment. The beetles were used last year to control the weed on the River Till and River Witham, near Lincoln.


Like many other invasive plants, azolla was first introduced to the UK as an ornamental exotic from the Americas in the 1800s.


Invasive species cost the UK


economy an estimated £1.7- billion every year. They cause damage to riverbanks and buildings, increase flood risk, crowd out and can kill off native wildlife. They can also become so prolific on waterways that anglers and boaters are unable to use them.


Homeowners can do their bit to help prevent the spread of invasive species like azolla by not dumping aquatic plants in the wild and always disposing of old plants and pond material responsibly, by composting or using a green waste bin.


Saving native crayfish from extinction


500 juvenile crayfish have been released into a tributary of the River Irfon as part of continued efforts to save the species from extinction.


The one year old crayfish, reared at the Environment Agency’s fish hatchery near Brecon, have been released into a carefully selected site on the river to breed. They were released in conjunction with the Wye and Usk Foundation, as part of the European Union’s Life+ funded Irfon Special Area of Conservation Project (ISAC).


Work to reintroduce crayfish into the area began in 2009, when egg carrying females were caught and transported to the hatchery from selected wild populations.


After a year in captivity the juvenile crayfish are stocked into carefully selected ‘Ark’ sites. These sites are chosen for their good habitat and water quality and because they are free from non-native crayfish and crayfish plague, a lethal fungus-like disease.


Oliver Brown, from Environment Agency Wales said:


“This project is an essential part of the Agency’s crayfish conservation strategy which involves protecting existing populations and establishing new safe havens for the species. “Working with the Wye and Usk Foundation has allowed us to develop our rearing facilities so we can release larger numbers


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of this threatened species back into the wild to help ensure its survival.”


Simon Evans, from the Wye and Usk Foundation and Project Manager of ISAC said:


“This work provides a beacon of hope for our native crayfish and is part of our efforts to improve the Irfon catchment as a whole. “We are also recovering the river’s habitat and water quality that the introduced crayfish need to thrive”


The White-claw is Britain’s only native crayfish. It is under threat from disease, climate change, habitat degradation and competition from the more aggressive American Signal crayfish.


Their status has recently been elevated from threatened to endangered and experts believe that without intervention there is real risk of the species becoming extinct from mainland Britain within the next three decades. This project is a small part of the wider work taking place to mitigate for the many threats facing the White-clawed crayfish. Elsewhere, water quality and habitats are being restored to a condition suitable for them and the invasive Signal crayfish are being controlled.


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