White Clawed Crayfish Surveys
The white-clawed crayfish is the only native freshwater crayfish found in the UK. They are found in a variety of aquatic habitats including rivers, canals, streams and lakes although their distribution is largely determined by geology and water quality. White-clawed crayfish breed between September to November when water temperatures are often below 10°C for a period of time. They are primarily nocturnal but can sometimes be observed around dusk in shallow water. White-clawed crayfish were once widespread and common but have suffered severe population declines due to the introduction of non-native crayfish (such as the American signal crayfish), flood defence works, dredging and agricultural activities.
Survey Types & Timing
White-clawed crayfish surveys generally entail one or more of the following techniques:
- Manual searches (for live crayfish and field signs of crayfish)
- After-dark torch-light surveys
- Baited traps
White-clawed crayfish survey methods are often dependent on the site conditions. White-clawed crayfish surveys are typically undertaken between March to September inclusively. Torching methods only are recommended between April and June due to the potential risk to young crayfish.
Legislation & Planning
The white-clawed crayfish is listed in Appendix III of the Bern Convention, and Annexes II and IV of the EC Habitats Directive, and is protected under Schedule 5 of the Wildlife and Countryside Act (1981) in respect of taking from the wild and sale. Schedule 9 of the Act makes it an offence to release or allow to escape into the wild all three non-native species of crayfish in the UK, and the use of white-clawed crayfish as bait is also illegal under the Act.
A survey licence is required at sites where there is high potential that white-clawed crayfish might be present and will be caught and handled during a survey.
The Next Step
White-clawed crayfish are a material planning concern where their presence has been established on site. Therefore all efforts should be made to ensure that crayfish and their habitat are suitably protected/conserved within the proposed development site. Where this is not feasible it may be necessary to translocate the crayfish to suitable alternative habitat. Such actions will need to be done under a mitigation licence obtained from the relevant Statutory Organisation.