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Signal crayfish targeted

16/08/2008

Information on how to deal with one of Scotland's most notorious alien species, the signal crayfish, will be published today.

The species is an increasingly common sight, particularly in Loch Ken where it has become the dominant species.

A new leaflet on the signal crayfish and the threat it poses will be launched by Environment Minister Michael Russell at the Galloway Game Fair.

Mr Russell said:

"Alongside the grey squirrel, Japanese knotweed and the American mink, the signal crayfish is one of the most problematic invasive species introduced to these shores.

"As well as competing with valuable native fish such as trout and salmon, the holes they bore into river banks for their nests can leave the land weak and lead to a greater risk of flooding.

"The leaflet I am launching seeks to raise awareness of the signal crayfish, which is a particular problem in the Galloway area.

"Any angler who catches one is urged to kill it on sight, not to throw it back into the water or take it away alive and contact the Scottish Government, Fisheries Research Services, Scottish Natural Heritage or SEPA."

The leaflet has been produced by Scottish Natural Heritage in partnership with a range of other organisations.

Signal crayfish are voracious predators which feed on insects, frogs and juvenile fish and their eggs, including those of Atlantic salmon. Signal crayfish also burrow into, and undermine, riverbanks. This can de-stabilize the riverbanks, leading to increased erosion and damaging the spawning grounds of a variety of fish species, including Atlantic salmon and trout. Unstable banks can also be a safety risk for both humans and livestock.

The non-native lobster-like creature was introduced to waters in England and Wales through fish farms about 20 years ago. In Scotland, signal crayfish were first recorded in the catchment of the Kirkcudbrightshire Dee in 1995. Since that date, specimens have been found in Scottish ponds, rivers and lochs as far north as Inverness-shire. Once established signal crayfish may compete aggressively with indigenous wildlife such as Atlantic salmon and trout for both food and habitat. It is against the law to keep, transport or release live signal crayfish or release them into the wild.

The leaflet appeals to anglers, canoeists, boaters and anyone who visits Scotland's rivers and lochs to look out for signal crayfish and help to eliminate them from our freshwater. The species is extremely mobile and has a limited ability to move over land in search of food or a new habitat. This means that they can spread very easily once introduced to a new waterbody.

The leaflet advises three groups to be particularly vigilant:

The advice for anglers is:

  • Check your landing and keep-nets before you leave the waters edge
  • If you accidentally catch any crayfish - bring them ashore or onto the boat for humane destruction.

The advice for boaters is:

  • Check the bilge and interior for any crayfish;
  • If you are taking your powerboat away flush out the engine cooling system with freshwater from a piped supply, if possible
  • Check the boat exterior for the presence of young crayfish - especially important for clinker-built boats.

The advice for canoeists is:

  • Drain your boat as usual;
  • Check the interior for any signs of crayfish presence
  • If it is possible, flush the boat out with freshwater from a piped supply before you leave.