The white-clawed crayfish is the UK's only native crayfish species. Other crayfish species have been introduced from other countries. Since the 1970s there has been more than a 50% decline in the areas where white-claws occur in England and Wales, and they are still declining rapidly.
They are nocturnal creatures and aren't very active during the winter, which means that this secretive invertebrate is rarely seen. They have an important role in the freshwater environment because of their diet, as well as providing food for other animals, such as fish, herons and otters. They are also important indicators of good water quality as they are intolerant of pollution.
Status: listed as Endangered on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species
Typical size: maximum 12cm, typically 6-8cm.
Lifespan: 12 years
Appearance: the white-clawed crayfish is one of our largest freshwater invertebrates. They are omnivorous, so eat everything from other invertebrates to carrion and water plants.
They have large pincers (claws) that are coloured cream or rosy white on the underside, and it is this distinctive feature that gave white-claws their name.
The carapace (hard upper shell) is generally brown to olive in colour, with a pitted appearance. However, all colour variations have been observed, including blue and red white-claws.
Where to see white-clawed crayfish
White-claws are found in rivers, streams, lakes and canals, and prefer clean, mineral-rich waters.