Six facts about crayfish to keep you environmentally compliant

Do you have a project with a river, lake, stream or pond close to it? If so, you might find yourself in deep water if you haven’t had any ecological surveys carried out to identify white-clawed crayfish. Senior Ecological Consultant, Felicity Andruszko, is leaving no stone un-turned, bringing you six snappy crayfish facts to help you keep your development projects on track.

White-clawed crayfish © Natural England/Jenny Wheeldon
White-clawed crayfish © Natural England/Jenny Wheeldon

Where to find them

White-clawed crayfish require water-bodies to be alkaline, calcium-rich, clean and well oxygenated. They can be found in streams and rivers as well as deeper lakes and ponds, and favour habitats with refuges such as large stones, and submerged tree roots where they can hide from predators.

White-clawed crayfish are found in scattered locations across England and Wales and in a few areas in Northern Ireland but are almost entirely absent from Scotland.

Different species and populations

There are seven species of crayfish currently known to be present in the wild in the UK. However only one of these species is native – the White-clawed crayfish (pustropotamobius pallipes).

Approximately 70% of the UK population has been lost since the 1970s, due to pollution, habitat loss and the introduction of non-native crayfish. The Non-native signal crayfish (pacifastacus leniusculus), which was introduced to the UK from North America in the 1970s, was sold to farmers looking to diversify into new markets.

American signal crayfish © Mark Philpott
American signal crayfish © Mark Philpott

The signal crayfish escaped from these farms and established populations in our rivers and lakes. Non-native crayfish, such as the signal crayfish, aggressively out-compete white-clawed crayfish for food and habitat and spread diseases such as crayfish plague, to which white-clawed crayfish have no resistance.

Signal crayfish are listed on Schedule 9 of the Wildlife and Countryside Act, which makes it an offence to release or otherwise allow them to spread.

If a project has non-native species present, like the signal crayfish, bio-security measures will need to be implemented to ensure they do not spread, which in turn can spread diseases.


White-clawed crayfish are protected in the UK under Schedule 5 of the Wildlife and Countryside Act 1981 (as amended). Under this Act, it is an offence to intentionally take white-clawed crayfish from the wild; and sell or attempt to sell any part of a white-clawed crayfish – alive or dead; or advertise that one buys or sells, or intends to buy or sell, any part of a white-clawed crayfish.

White-clawed crayfish, Essex © Thomson Environmental Consultants
White-clawed crayfish, Essex © Thomson Environmental Consultants

A survey licence from the relevant statutory body (e.g. Natural England) is required for surveying (handling and taking) of white-clawed crayfish. If a development may harm or involve the ‘taking’ of white-clawed crayfish, a licence will be required from the relevant statutory body for conserving the species.

When to survey

Most surveys for crayfish can be carried out all year round. However, due to the habits of white-clawed crayfish, there are different types of surveys that need to be carried out at specific times. These include: habitat surveys only – due to reduced crayfish activity; hand searching, torchlight, trapping and substrate searching.

When to mitigate

The optimal time for licensed capture and exclusion for white-clawed crayfish is in April and July through October.

We can help you

To learn more about these different types of surveys and mitigation techniques, get in touch with us today and ensure you’re meeting environmental compliance requirements when it comes to non-native species and protected freshwater species.

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