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White-Clawed Crayfish Surveys

The white-clawed crayfish is the UK’s only native crayfish. It is a crustacean protected under schedule 5 of the Wildlife and Countryside Act (1981) (as amended) making it illegal to harm, disturb or take them from their habitat. They are currently under threat from the competition and disease risk presented by American signal crayfish. Since 1907s there has been a dramatic decline in areas where white-clawed crayfish occur.

White clawed-cray fish spend most of their day under large stones or in the riverbank. They are mainly nocturnal and not very active in the winter. They are omnivores with their main diet composed of animal matter and decaying vegetation. They will also eat invertebrates and aquatic plants. They are a good indicator of good water quality as they are intolerant of pollution. Their main habitats are rivers, stream, lakes and canals, and they prefer mineral rich waters.

There are various survey techniques which can be used, including:

  • Habitat assessment
  • Manual searching (if the water is clear and water flow is low);
  • Hand netting;
  • Night searching by torch (if the water is too deep for hand search and the water flow is slow);
  • Trapping using bait

A licence from the Environment Agency is required to catch and handle crayfish (e.g. to use bait traps). The breeding season is late May to June, and this is when females may be carrying newly hatched young. If habitat is going to be destroyed then it is best to move female crayfish with eggs earlier in the breeding season, rather than wait for the young to hatch as catching the young is much harder. It is best to survey outside the breeding seasons with the optimum period being July to September.

Phlorum can offer advice for developers concerned about impacting upon white-clawed crayfish; contact us for more information about our white-clawed crayfish surveys.

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