Environment Agency moves to eradicate alien fish

A fast-breeding alien fish that has colonised two East Devon lakes and is threatening to wipe out the local fish population could soon be facing extinction itself.

Tomorrow Environment Agency is taking the first steps to eradicate the Top Mouth Gudgeon from lakes at Bicton College and Bicton Park Botanical Gardens near East Budleigh. By acting now, the Agency aims to prevent any further spread of the species to surrounding lakes and rivers.

Measuring only 3 - 4 cms in length, the Top Mouth Gudgeon can out-compete native species and may carry a damaging parasite, both of which could threaten fish diversity in the area if measures are not taken.

Topmouth gudgeon, a small Asiatic member of the carp family, appeared in mainland Europe in the 1960's. It has been introduced accidentally into a number of British lakes. This small fish is around the same size as the UK native gudgeon, which it resembles.

It can out-compete native species such as roach and rudd because it matures at one year old, whereas a rudd does not mature sexually until two or three. It can also breed up to four times a year.

The Agency recently installed a gravel filter on behalf of Bicton College to prevent the spread of the invasive fish. There was a slight setback after the ornamental lake overflowed following a thunderstorm and a number of Top Mouth Gudgeon were washed past the filter and carried down the Bicton Stream.

Agency fisheries officers later collected around 6,000 of the fish from the stream following the thunderstorm ‘break-out'. It is estimated that there could be up to 100,000 of the tiny invaders in the smaller lake alone.

On Thursday (June 29) the Agency will electro-fish approximately 400 • 500 metres of the Bicton Stream and remove any Top Mouth Gudgeon it finds. The fish will be sent to the Agency's national fisheries experts for analysis.

‘At the moment Bicton is thought to be the only site in Devon with a population of Top Mouth Gudgeon. We are keen to take action to eradicate them. They pose a very real risk to our native fish. It is important we act now,' said Dave Brogden for the Environment Agency.

The Agency has successfully removed the species from two sites in the North of England and one in the Midlands. Ultimately, the removal of Top Mouth Gudgeon from Bicton will probably involve the rescue of native fish from the lakes prior to final eradication of the alien species.

Last month special measures were introduced at Bicton during a BBC Springwatch event to ensure anyone using the main lake didn't accidentally transport Top Mouth Gudgeon fish or their eggs off the site.

These included using disinfectant to wash down boats using the lake, cleaning people's shoes and boots and cleaning/disinfecting fishing equipment.

• Top Mouth Gudgeon is listed as a category 5 risk species under the Importation of Live Fish Act (ILFA) which is the highest level of risk.
• The parasite they carry is believed to interfere with the breeding cycle of salmon and trout.
• The Environment Agency is working with the owners of the two lakes who have been issued with licences under the Importation of Live Fish Act (ILFA). These licences require the containment of the alien species within the lakes
• The smaller of the two Bicton lakes flows into the Bicton Stream, which feeds the Colaton Raleigh Stream which in turn flows into the River Otter.
• It is thought the Top Mouth Gudgeon were accidentally introduced to Bicton Lake as a result of fish stocking.