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Signal Crayfish

Signal Crayfish     Pacifastacus leniusculus

Photo credit: Trevor Renals

  • Appearance: Lobster-like crustacean, claws have red undersides and small turquoise/white blotch on the upper surface at the claw hinge. Much larger (adults 16-18 cm) than the protected native White-clawed crayfish (10-12 cm).
  • Diet: Fish, amphibian eggs, young fish, invertebrates, detritus and vegetation.
  • Impact: Carries Crayfish plague, a disease causing the decline of native White-clawed crayfish. Negative impact on the diversity and abundance of aquatic communities including commercial fisheries. Burrowing can cause erosion and destabilisation of riverbanks and increase flood risk.
  • Pathway: May have escaped or been deliberately released into the wild.
  • Legal status: Species of special concern listed under the retained EU Regulation 1143/2014 and the Invasive Alien Species (Enforcement & Permitting) Order 2019.


  • Unless you have a licence or permit or an exemption applies you must not:
    • keep them in your house, garden or business
    • sell them to other people
    • exchange them for goods
    • release them into the environment
    • let them breed or escape
    • import them into the UK
    • transport them within the UK
    • export them to other countries


  • What to do if you see Signal crayfish for sale or other offences being committed: Make a report by following the guidance here.


  • What to do if you see this animal in the wild: Record it with a photograph (where possible).