The White-Clawed Crayfish (Austropotamobius pallipes)

Description: A UK native species. Populations in some rivers have declined sharply due to 'crayfish plague'.
It is nocturnal; the females typically have broader and more hairy abdominal regions to accommodate their broods. Adult males have much larger claws than the females and are territorial, especially in the breeding season.

Habitats: clear, well oxygenated water, usually fast flowing rivers typically rich in calcite (calcium carbonate, CaCO3), which is essential for the hard outer shell of the animal. A chasmophite, it lives under rocks and stones in the river bed or holes burrowed in to the river banks below the water line.

Diet: Omnivorous, feeding on a wide range of freshwater macrophytes (small plants), macroinvertebrates (small insects) and detritus (organic debris). It is also cannibalistic, feeding on recently moulted individuals.

Breeding: In autumn the female attaches the egg cluster (around 100) to the underside of her abdomen. She overwinters in her burrow with her brood until late spring / early summer when they hatch into miniature crayfish but without their tail-fans. At this stage they are immobile and so cling to the female's abdomen.

The offspring moult into a second stage developing a hairy tail-fan enabling them to become mobile and active. After a second moult they develop an outspread tail-fan and have the appearance of mature crayfish.

Juvenile crayfish may undergo seven or more moults during their first full year of life but upon reaching maturity after three to four years they only moult once a year.

Lifespan: seven to twelve years.

Threats: The native white-clawed crayfish is under threat from the North American signal crayfish (Pacifastacus leniusculus) and the disease it carries, crayfish plague.

Signal crayfish have been farmed in Britain since the 1970's but are now widespread in rivers throughout much of the UK due to escapes and deliberate illegal introductions.  They carry crayfish plague, a virulent fungal disease (Aphanomyces astaci) which does not affect the signal crayfish but is lethal to the white-clawed crayfish.  It has caused drastic losses of native crayfish in rivers in the UK.

Being much larger and more aggressive, signal crayfish prey on native crayfish, out-compete them for food, and also seriously damage river habitats and native fish populations.  They have spread rapidly throughout the UK, spreading with them crayfish plague, wiping out native crayfish populations and adversely affecting fisheries.

The River Eden and tributaries are so far free from signal crayfish and crayfish plague and represent one of the last strongholds for the white-clawed crayfish.  In fact, all Cumbrian rivers are currently free of signal crayfish and crayfish plague, except the Derwent river system.  Unfortunately signal crayfish are not far away and pose a very real threat to the native crayfish in the Eden as well as other Cumbrian river systems.

Help us to save our white-clawed crayfish - click here for more details.
See also the following leaflets:
Stop the spread of alien crayfish and crayfish plague - Environment Agency leaflet for the general public.
Stop the spread of alien crayfish and crayfish plague - Environment Agency leaflet for restaurant owners.
Signal crayfish - an unwelcome addition to Scottish Streams - Fisheries Research Services leaflet.