White-clawed crayfish by Martin Pugh 1/1

White-clawed Crayfish Austropotamobius pallipes

The white-clawed crayfish is the largest native freshwater crustacean species. It is being severely affected by the non-native signal crayfish. They have pinkish-white claws and a pitted appearance ranging in colour from brown to olive. Being predominantly nocturnal and partial to hiding in crevices, this species is particularly hard to find.

Conservation status

White clawed crayfish are protected by the Wildlife and Countryside Act and the Countryside Rights of Way (CROW) Act. This means that a special licence is required from Natural England to survey for crayfish or to use crayfish traps. A Norfolk Biodiversity Action Plan has been drafted by the Environment Agency.

Our native crayfish have been severely affected by the introduction of the non-native signal crayfish. The signal crayfish was introduced to this country in the early 1980’s for farming and commercial aquaculture, but unfortunately many escaped and entered our water courses. Signal crayfish grow up to twice the size of white-clawed crayfish and are highly aggressive, therefore outcompeting the smaller and retiring native species by predation and direct competition for food.

Some non-native crayfish can carry a fungus (Aphanomyces astaci) commonly known as crayfish plague, which does not affect them but can be lethal for our native crayfish. Local warnings have been given to all water users in the River Waveney area regarding this crayfish plague following a recent outbreak. The Environment Agency is advising the public to clean any equipment with disinfectant, bleach or anti-fungicidal products

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Did you know?

This species was once widespread in Europe, but many populations have been wiped out by habitat modification, pollution and, most importantly, by the introduction of non-native species such as signal crayfish. Ireland and the UK still provide some important strongholds for the white-clawed crayfish, although they have disappeared from much of southern England and the species is now only found in small pockets of the UK. In Norfolk, white-clawed crayfish have been recently spotted in the River Wissey, River Glaven and River Wensum (an SAC site for native crayfish).

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