Lakes poisoned to wipe out the silver invaders
Topmouth gudgeon, a species that originated in China and Japan, have been found in 32 locations around the country.
The fish, which are just three inches long, can dominate waterways and compete with native fish and mammals, such as water voles, for food.
They also carry a disease that can kill native salmon and trout. Fishermen fear the topmouth gudgeon, which can establish populations of hundreds of thousands in a single lake, will destroy water systems if they spread further.
Officials at the Environment Agency will now carry out an eradication programme, using specially adapted boats and hovercraft to spray poison into the lakes where the topmouth gudgeon have been found.
The decision is controversial. Critics claim that it can take years for waterways to recover, which could be devastating for businesses that rely upon fisheries.
Experts, however, insist that poisoning is necessary to prevent the invasive species from spreading.
Matt Brazier, non-native species technical adviser at the Environment Agency, said: “Topmouth gudgeon is one of the most invasive non-native species in western Europe.
“Our objective is, between now and 2017, to eradicate topmouth gudgeon and remove the threat it poses.” Topmouth gudgeon are thought to have been brought to the UK as ornamental fish before entering into the wild, probably by accident.
The species was first identified in a Hampshire lake in 1986 before rapidly spreading across the country. It has now been found in lakes in Llanelli, South Wales, near Kendal in the Lake District, and in several sites in Yorkshire.
Previous attempts to remove the topmouth gudgeon using electrofishing — where electricity is used to stun fish so they can be scooped up in a net — have proven unsuccessful.
In 2005 the Environment Agency began a trial of fish poison — or piscicide — at some sites and found it to be far more effective.
Officials first try to remove native fish from the water using nets and they are kept in large tanks or nearby lakes, leaving the topmouth gudgeon behind.
Boats and hovercraft equipped with jet-powered sprays are used to pump the poison into the water, killing all fish that remain.
This breaks down and disappears over a number of weeks and the native fish can then be reintroduced.
The technique has proved to be controversial as it can also affect other species living in the water, such as invertebrates, but experts say they recover quickly.
Mr Brazier added: “The only method that is effective is to use a piscicide. It is an organic chemical that is specifically used to target fish in the water and it is not harmful to mammals or birds.”
Mark Lloyd, the chief executive of the Angling Trust, said: “Unfortunately this is a necessary evil. If topmouth gudgeon spread throughout our river systems then it will be an ecological disaster for fisheries.
“Although poisoning water bodies may seem extreme, the ends justify the means at this stage.”
The Environment Agency is aiming to treat six sites before the end the year.
Last year 17 lakes at Clawford Vineyard Fishery in Devon were treated but its managers says business was affected. John Ray, 69, said: “All the frogs disappeared and fish stocks are only just starting to recover now.”
Source : The Telegraph