Signal Crayfish: an ecological threat to rivers in the UK

It is hard to comprehend the extent to which Signal crayfish have colonised our rivers and lakes over the last three decades and the impact they have had on our freshwater habitats. They burrow into the banks of rivers to spend the winter in a torpid state, undermining the banks in the process. They eat everything - true omnivores - including each other when other species have disappeared. I have seen them being taken by great crested grebes on the Serpentine in Hyde Park and they recently been seen at the Tring reservoirs. This individual was from the river Thame in Oxfordshire. The impact they have had on upland streams is shocking and something will need to be done to prevent ecological disaster.