Alien Crustacean Invaders

Crayfish are freshwater crustaceans that look like miniature lobsters. In some countries they are farmed and sold as luxury food items, which can be quite lucrative. Although there are around 500 different species of crayfish, there's only one British native - the white-clawed crayfish, Austropotamobius pallipes.

Native crayfish grow and breed relatively slowly in comparison to other farmed species. So when British farmers were encouraged to diversify and try crayfish farming in the 1970s they imported the faster growing and highly fertile North American Signal Crayfish. It was already being successfully farmed in Europe and was yielding high profits.

Unfortunately the crayfish market in Britain never really took off and the ponds and lakes containing the imported stocks were neglected. Given their extreme mobility - capable of climbing and walking over long distances - its not surprising that over the past decades they have spread widely.

Unfortunately it was discovered in the 1980s that Signal crayfish are the carrier of a fungus called Aphanomyces astacim, although it has been dubbed the 'crayfish plague'. This fungus doesn't kill Signals but it has had a devastating effect on our native crayfish population. The plague is also hard to contain as the fungal spores are carried through water and can be passed from waterway to waterway on damp fishing equipment or even Wellington boots.

Attempts have been made to eradicate the Signal crayfish, but with little success, once established they are very hard to remove. We need to know more about them if we want to control these cunning crustaceans and find a chink in their armour.

Ideas on how to control the signal crayfish have been made - perhaps by the use of pheromones as a deterrent or to impede breeding. But as yet there's no evidence to show what will work. So Jeama Stanton is studying their behaviour, logging their every move day and night by attaching tiny radio tags. Armed with her information, Jeama hopes a strategy can be found to save our natives.

There's a lot to be learned from her work, not just about crayfish but the knowledge can be applied to other animals. Jeama says we should learn from our mistakes and stop introducing foreign species as it usually ends with undesirable knock-on effects.