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White-clawed Crayfish Surveys, Mitigation & Licensing

jh ecology undertakes white-clawed crayfish surveys primarily in the South-west including: Cornwall, Devon, Dorset, Gloucestershire, Somerset and Wiltshire; but we also carry out crayfish surveys across the South-east including: Berkshire, Buckinghamshire, Hampshire, London, Oxfordshire, Surrey and Sussex; and the Midlands including: Birmingham, Herefordshire, Leicestershire, Warwickshire and Worcestershire; and the rest of England. jh ecology can advise on all aspects of white-clawed crayfish survey and mitigation.

White-clawed crayfish

White-clawed crayfish

The white-clawed crayfish is Britain’s only native species of crayfish and although this species remains widely distributed in England and Wales, only a tiny proportion of the pre-1970s population survives. Much of this dramatic decline has been primarily attributed to the introduction and spread of non-native American signal crayfish and the crayfish plague that it often carries. Additional threats include modifications to watercourses (including engineering, dredging and culverting), siltation, pollution, and increased urbanisation. Crayfish occupy a variety of habitats including canals, rivers, streams, reservoirs and quarry pools.

The white-clawed crayfish is protected under both European and UK law. Under UK legislation the white-clawed crayfish is protected under Schedule 5 of the Wildlife and Countryside Act 1981 (as amended), making it an offence to take them from the wild or sell them. They are also fully protected under Annex II and V of the European Habitats Directive (1992), requiring the designation of Special Areas of Conservation (SAC) for their protection and prohibiting the taking or disturbance of the species in the wild. The European Bern Convention lists white-clawed crayfish in Appendix III as a protected species.

White-clawed Crayfish Surveys

Survey reports and mitigation plans are required for development projects that could affect white-clawed crayfish as part of getting planning permission or a licence. White-clawed crayfish surveys are required where the distribution and historical records suggest they may be present and / or there is suitable habitat. Damage, repair or maintenance works to canals, rivers, streams, reservoirs and quarry pools may cause damage to populations of white-clawed crayfish, and so surveys may be required ahead of works commencing.

White-clawed crawfish found during hand-netting

White-clawed crayfish found during hand-netting search

We will typically conduct an initial site appraisal to identify the potential for white-clawed crayfish to be present on a site, and therefore the need for more detailed survey looking for white-clawed crayfish. We undertake white-clawed crayfish surveys following standard methods including:

  • Combined manual searching and hand-netting – involves hand searching potential refuges for crayfish such as boulders, cobbles, in channel vegetation, root systems of bankside trees, burrows in the bank, hollow logs or woody debris; and placing a hand net downstream and irritating sediments, woody debris and cobbles immediately upstream, as well as sweeping amongst submerged tree roots, accumulations of leaf litter and twigs, marginal vegetation and undercut banks. Such searches are only effective in clear, shallow water.
  • Night searching – involves searching by torchlight after sunset. This method can be used to survey inaccessible areas to manual searches such as in pools which are too deep to search by hand, and has been shown to be a good way of finding crayfish in areas that are not positive in daylight hours because crayfish are known to mainly forage in the dark in order to avoid predators. This survey method can only be used where the water is slow-moving.
  • Trapping – uses baited plastic mesh traps that are left for no longer than 24 hours at a time. This method can be used where the water is too deep or cloudy for manual searches.

As with many protected species there are seasonal constraints to undertaking white-clawed crayfish. Please refer to our Ecological Survey Calendar for seasonal constraints to undertaking white-clawed crayfish surveys.

White-clawed Crayfish Mitigation & Licensing

Should white-clawed crayfish be found where maintenance or repair works to structures on the bank or bed of a water-body or watercourse (e.g. bridges) are required, and it is likely that crayfish would be disturbed or killed, it will be necessary to move white-clawed crayfish away from working areas to safe locations prior to works commencing. A licence is required from Natural England to permit the movement of white-clawed crayfish.

Where white-clawed crayfish are found on a site, jh ecology can provide the following services:

  • Legal compliance advice, including preparation of licence applications.
  • Design of mitigation measures to avoid / reduce the risk of harm to white-clawed crayfish including: working methods that reduce the area of potential crayfish habitat affected and minimise the risk of pollution; excluding white-clawed crayfish from working areas; and vegetation planting.
  • Design of compensation measures including improving or replacing any habitat that will be lost and moving white-clawed crayfish (this must be within the same catchment to reduce the chances of disease spreading).
  • ‘Tool-box’ talks to site contractors and ecological clerk of works (i.e. ECoW).
  • Post-mitigation monitoring.

Please contact us on or 01823 530 084 for further advice or help.