The word crayfish is derived from the Old French word escrevisse.
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| White Clawed Crayfish are classified as Globally Endangered. Up to 95% of UK populations have been lost in recent years. |
The white clawed crayfish (Austropotamobius pallipes) is the UK's only native crayfish and our largest fresh water 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 in England.
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.
It certainly does not thrive when cattle waste mixed in with mud and silt threaten to overwhelm water courses.
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| Part of the fencing work |
For this reason, N.T Rangers based at St. Catherine's, Windermere were given the go ahead to fence off hundreds of metres of a watercourse, located near Windermere, Cumbria, with known populations of crayfish upstream; crayfish are also to be found downstream. Through a conservation plan the work was grant aided by Natural England.
"Cleaning up" the watercourse by excluding cattle will hopefully allow crayfish from the populations both downstream and upstream to spread into and colonise this stretch of water.
"Cleaning up" the watercourse by excluding cattle will hopefully allow crayfish from the populations both downstream and upstream to spread into and colonise this stretch of water.
However, the cattle still have to drink. On average a cow needs 15 gallons of water per day; 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 large water trough put in place many metres further downstream.
The following images illustrate the most recent phase of the project, which is still ongoing.
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| Building the header dam...The fun bit but COLD! |
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| The completed dam. |
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| The blue alkathene pipe on its way to the water trough. |
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| through the wall...... |
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| ........and into the trough..... |
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| ....and back out through the wall into the stream again! |
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| The water trough fills up rapidly. |
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| a new gate was needed to allow stock movement past the fenced off beck. |
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| The new gateway. |
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| Ideal habitat for crayfish, with plenty of watercress for the juveniles to take cover! |
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| 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 much larger 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.
The Signal breeds much more prolifically, outcompetes the White Clawed for food, and worst of all, carries a fungal plague that it is immune to.... but 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 adversely on plants, invertebrates and snails.
The Signals burrow into river and canal banks in such numbers, that in the worst infested sites, people have reported seeing banks retreating under the relentless pressure.
IMAGES FROM AN EARLIER PROJECT TO IMPROVE HABITAT CONDITIONS FOR THE WHITE CLAWED CRAYFISH:
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| An earlier fencing project further downstream, which incorporates a new bridge for the cattle to cross the beck. |
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| A series of Pasture Pumps were used here instead of a water trough to allow cattle to get water from the beck. |
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| A Pasture Pump bolted onto two railway sleepers. A hard stand is being constructed infront of the pump. The stream runs between the wall and the new fence. |
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| As the cattle drink, they push the counter balanced weight or pendulum back and forth with their noses; this action pumps up more water from the stream for them as they drink. See image below with pendulum pushed back. Clever Cow!  |
Encouraging Update!
Adult white clawed crayfish spotted recently by the stream near a fenced off area. (May 2014)
Roland Wicksteed: Central and East Lakes.
Are there American Crayfish in any of Cumbria's lakes or rivers? Is there any hope for the white claw in the long term?
ReplyDeleteThank you for your query. The Derwent River System in the North Western Lakes does unfortunately have the American Signal Crayfish. Far too close for comfort. 80% of our waterways are estimated to be infested by the Signal Crayfish. It not only wipes out the smaller native crayfish but also causes immense ecological harm to our waterways and destroys river and canal banks with its burrowing activities. The rest of the Cumbrian waterways are free of infestation for now.
DeleteThere is hope for The White Clawed Crayfish, as long as people are careful. See various web sites including an E.A. leaflet: Stop the Spread of Alien Crayfish and Crayfish plague.
Bristol Zoo Gardens and Bristol Conservation and Science Foundation run a successful breeding programme, in which they release captive bred white claws into “Ark Sites”. These are usually streams that are ideal for the native crayfish, and in theory, too far away or isolated for the Signals to find. Some of Cumbria’s streams are similar, so yes, there is hope!
Bad news. I need to update the above reply. Recently, American Signal Crayfish have been found within the Eden catchment area. Eden Rivers Trust tell me that they are in an isolated watercourse that forms part of the Eden Rivers System. On an encouraging note, they may be able to be contained there.
ReplyDelete