American Signal Crayfish

Crayfish ID features

  • Introduced for food in the late 1970s and 1980s this species soon spread quickly across the UK, distribution is limited in Scotland.
  • Once present in a watercourse they spread rapidly, can move both up and downstream and can cross land to colonise neighbouring water bodies.
  • The signal crayfish carry a fungal disease (crayfish plague) which is lethal to the endangered native white clawed crayfish in England, Wales and Ireland.
  • They feed on a range of aquatic invertebrates and fish eggs directly affecting native fish populations.
  • Their burrowing tendencies cause the undermining of river banks and increase erosion.
  • The stocking or movement of these crayfish in Scotland is illegal.
  • It is an offence to trap for crayfish in Scotland without a licence from SNH.  Unregulated trapping is ineffective and illegal traps have been known to trap and kill otters which is an offence.
  • There are known populations of signal crayfish both north and south of Ayrshire.  Loch Ken has a significant population and it is important that anyone who is moving between affected water bodies and clear water bodies do not transfer any live crayfish. (see the NBN gateway map of signal crayfish in UK  )

Download Poster here (pdf): Signal Crayfish Poster