THE WHITE CLAWED CRAYFISH is a freshwater crustacean, related to lobsters and crabs. It is brown or dark olive green in colour but it gets its name from the fact that the under sides of its claws are paler. It is also sometimes called the Atlantic stream crayfish. It is slow growing and late to mature but can reach a length of around ten to twelve centimetres.
The species is found all over Europe but is in sharp decline and is listed by the IUCN as 'endangered'. The main reason for the decline is the introduction of the North American signal crayfish. They are much faster growing than white clawed crayfish and were imported so that they could be farmed for food. But they carry a disease called crayfish plague which they have an immunity to but white clawed crayfish don't. Ireland is one of the few European countries which has never imported signal crayfish. As a result of this we have probably the healthiest stocks of the animal left in the world and a special responsibility to protect them and their habitats.
They live in rivers, streams, lakes and canals, mostly in the Midlands, that have lime-rich water. They thrive best in unpolluted water but stocks have been found in waterways that are classified as 'slightly' or 'moderately' polluted. They are fully protected under Irish law but have some natural predators including herons, otters and, in particular, mink. Juvenile crayfish are also eaten by a wide variety of fish species.