Head to head
White-clawed Crayfish vs Signal Crayfish
White-clawed Crayfish
VS Signal Crayfish
The white-clawed crayfish and the signal crayfish share rivers in Britain and western Europe, and their story is one of the best-known examples of a native animal overwhelmed by an invader.
| White-clawed Crayfish | Signal Crayfish | |
|---|---|---|
| Scientific name | Austropotamobius pallipes | Pacifastacus leniusculus |
| Origin | Native to Britain, Ireland, and western Europe, and the only crayfish native to Britain | Native to rivers and lakes of north-western North America, and introduced to Europe from the 1960s to be farmed |
| Size | Usually around 8 to 12 cm long | Often 12 to 16 cm long, with big, smooth claws |
| Claws | Brown to olive body, with claws that are pale, whitish underneath | A white to bluish-white patch at the joint of each large claw |
| Habitat | Clean, hard-water streams and rivers with stony beds | Rivers and lakes, digging burrows into banks that can cause erosion |
| Crayfish plague | Highly susceptible, and populations across Europe have been wiped out | Carries the water mould without being harmed, and passes it to native crayfish |
| Diet | Insect larvae, snails, worms, fallen leaves, water plants, and dead animals | Insect larvae, snails, fish eggs, small fish, water plants, and dead animals |
| Conservation status | Endangered, declining across its range and surviving in isolated populations | Least Concern in its native range, and a widespread, damaging invader across Europe |
White-clawed Crayfish vs Signal Crayfish: common questions
Which crayfish is native to Britain?
The white-clawed crayfish, which is the only crayfish native to Britain.
Why does the signal crayfish threaten the native species?
It carries crayfish plague, a water mould that does not harm it but kills native European crayfish, and it also competes with them for food and shelter.
How can you tell them apart?
The signal crayfish is larger and has a white to bluish-white patch at the joint of each large claw, whereas the white-clawed crayfish has pale claw undersides.