White-clawed crayfish: surveys and mitigation for development projects
Standing advice for local planning authorities to assess impacts of development on white-clawed crayfish.
Survey reports and mitigation plans are required for development projects that could affect protected species, as part of getting planning permission or a mitigation licence. Surveys need to show whether protected species are present in the area or nearby, and how they use the site. Mitigation plans show how you’ll avoid, reduce or manage any negative effects to protected species.
This is Natural England’s species standing advice for local planning authorities who need to assess planning applications that affect white-clawed crayfish.
Local planning authorities should use this advice to decide what is needed for surveys and planning mitigation measures to protect white-clawed crayfish.
If a local planning authority consults Natural England and the Environment Agency on the same planning application, Natural England will use this standing advice and the Environment Agency will lead on providing additional advice.
Ecologists need to decide which survey and mitigations methods are right for the project they’re working on. If this standing advice isn’t followed, they’ll have to include a statement with the planning or licence application explaining why.
Where this guide says ‘you’ it means the ecologist.
Get more detail on:
- construction near protected wildlife (for developers)
- how planning authorities can assess applications involving protected wildlife
When you need to survey
Survey for white-clawed crayfish if distribution and historical records suggest they may be present.
White-clawed crayfish live in rivers, streams, canals and quarry pools. Development or repair works may cause damage to populations, and so may require survey under licence.
Acceptable methods for surveying crayfish are:
- manual searching (when the water is clear and the flow is low)
- night searching by torch (when water is deep and slow-moving, or in pools which are too deep to search by hand)
- trapping using a baited plastic mesh trap approved by the Environment Agency (when water is too deep or cloudy for manual searches)
You’ll need a licence survey crayfish if you’re going to catch and handle them. You may also need permission from the Environment Agency to use crayfish traps.
You are breaking the law if you:
- use illegal traps
- recklessly allow water voles to drown in crayfish traps
- put traps in the entrances to water vole tunnels
You need to kill and dispose of non-native crayfish if you trap them because you can’t release them back into the wild
Read more about acceptable trapping techniques.
Find out about biosecurity and disinfection when trapping.
Timing for surveys
Survey for white-clawed crayfish after the breeding season (mid-July to mid-September). Avoid late May and June when females may be carrying newly hatched young.
If works involve the loss of habitat, it’s better to move female crayfish with eggs earlier in the breeding season, rather than wait until the young are released, as you’re unlikely to be able to catch the young.
Assess the impacts
Assess the potential impacts of your plans without any mitigation in place.
You must aim to avoid negative effects, eg by redesigning the scheme. If this isn’t possible, use mitigation measures to reduce the impacts and use compensation measures if there are still negative impacts for crayfish.
Mitigation and compensation methods
Mitigation measures can include:
- reducing disturbance to the river bank
- reducing the amount of sediment released into the water
- reducing the area affected
- doing work in small sections
- reducing water pollution including silt
- adding appropriate vegetation
- excluding crayfish from construction areas, but only when the water temperature is 4°C or higher
Compensation measures can include:
- providing habitat to replace any that will be lost
- moving the crayfish (but only within the catchment to reduce the chances of disease spreading)
White-clawed crayfish need refuges so they can avoid being attacked or washed away in high waters.
They use natural and artificial refuges,like rocks or rock baskets, that are:
- fully submerged
- big enough to cover the crayfish, but not too big for the size of animal
- stable and resistant to high waters
- not being used by other wildlife
Selecting Crayfish Ark Sites shows how you can help with the long term survival of white-clawed crayfish.