The white clawed crayfish is the UK's only native crayfish and our largest crustacean; its distribution and numbers have declined catastrophically in recent years, and now it is the rivers and streams of Cumbria that are its main stronghold.
|White clawed crayfish.|
White clawed crayfish inhabit clean mineral rich water, usually in limestone areas; this releases calcium carbonate into the water which the crayfish needs to build its hard carapace or outer shell. It is intolerant of pollution, so its presence is often a sign that the water quality is good. It plays an important role in maintaining a stable water ecology. It certainly does not thrive when cattle waste mixed in with mud and silt threaten to overwhelm water courses.
|Part of the fencing work.|
For this reason, N.T Rangers based at St. Catherine's were given the go ahead to fence off hundreds of metres of a watercourse, with known populations of crayfish upstream; However, the cattle still needed to drink, and a way to reliably provide water for them from the original source was needed. -The answer was to pipe water by gravity feed from a header dam into a water trough put in place many metres further downstream. The following images illustrate the most recent phase of the project, which is still ongoing.
|Building the header dam...The fun bit but COLD!|
|The completed dam.|
|The blue alkathene pipe on its way to the water trough.|
|through the wall......|
|........and into the trough.....|
|....and back out through the wall into the stream again!|
|The water trough fills up rapidly.|
|a new gate was needed to allow stock movement past the fenced off beck.|
|The new gateway.|
|Ideal habitat for crayfish, with plenty of watercress for the juveniles to take cover!|
|The water pipe is well hidden, and the gap in the wall normally has a hurdle placed across it to deny access to stock.|
The main reason for the massive losses in native White Clawed numbers was the introduction of the American Signal Crayfish in the Seventies. It is a voracious predator that has annihilated the White Clawed from many waterways, especially in the South of the country. It breeds much more prolifically, outcompetes it for food and worst of all, carries a fungal plague that is fatal to the native species. The Signal does major harm to the eco systems of rivers in the UK. It severely depletes fish stocks by devouring fish eggs and small fish, as well as impacting on plants, invertebrates and snails. The Signals burrow into river banks in such numbers, that in the worst infested sites, people have reported seeing banks retreating under the relentless pressure.
Please help maintain the populations of the White Clawed Crayfish in Cumbria; clean and dry any equipment. you may use around rivers and lakes. This will reduce the risk of spreading the "Crayfish Plague" , the fungus of which thrives on damp boots, fishing gear etc.