Cumbria’s unique rivers and lakes are under serious threat from an increasing number of invasive alien species. Aquatic plants, non native fish and other unwelcome visitors have already wrought ecological mayhem in other parts of the country by destroying habitat and pushing out our own native wildlife. Many are already heading our way but anglers can play a big part in helping to prevent new introductions or the spread of those already established in the region.
The Cumbria Freshwater Invasive Non-Native Species Initiative aims to coordinate action thoughout Cumbria by providing information on freshwater invasive non-native species, relevant policies, work being carried in the county, how you can get involved and much more.
Himalayan Balsam and Japanese Knotweed
Groups throughout the county are already tackling Himalayan Balsam and Japanese Knotweed, vigorous weeds that crowd out our native plants, particularly along riverbanks. Both die back in the winter leaving the banks bare and increasingly susceptible to erosion. Washed out silt can then smother the spawning gravel used by salmon and trout. Clubs and riparian owners can help by pulling up or strimming Himalayan Balsam on their waters and anglers should avoid transferring seeds to new sites through muddy footwear. Japanese Knotweed does not succumb quite so easily to mechanical methods and invariably has to be tackled through a longer term spraying regime.
Australian Swamp Stonecrop
In the lakes, several exotic pond plants have become established, growing prolifically to out-compete native plants and smother the water surface. The worst offender is Crassula helmsii, also known as Australian Swamp Stonecrop or New Zealand Pygmyweed. This is already established in Derwent Water, Bassenthwaite Lake, Grasmere, Coniston and others. At the moment there is no effective control method, so anglers must always check and clean tackle when moving between sites to prevent it spreading further.
A number of Cumbrian rivers, particularly the Eden and Kent catchments support healthy populations of our native White-clawed Crayfish. These are rare elsewhere in the country due to the introduction of the American Signal Crayfish. These more aggressive invaders not only muscle out the white-clawed crayfish but also carry crayfish plague; a disease that kills all native crayfish. Plague spores can be transferred on angling kit so it’s essential that fishing tackle is dried or disinfected before moving between rivers and catchments. On top of this signal crayfish have also been shown to greatly reduce the number of young salmon and trout in some becks. There is no known method of eradicating signal crayfish once they’ve arrived. This makes it vital for all anglers to prevent them getting a foothold in the first place.