Thursday, 22 September 2016

Softly, Softly, Catchee Crayfish.

Scout Beck is a stream flowing past High Lickbarrow Farm near Windermere.

Shortly after the National Trust acquired the farm, Storm Desmond hit Cumbria in December, 2015; the ensuing flood caused extensive damage to stone pitching that was built into this stream bed many years ago. 
Damage to the pitching at Scout Beck and the eroded stream bank.

This pitching work was sanctioned by the Environment Agency  to protect neighbouring property from erosion.
     
The National Trust undertook to repair the damage. But the stream is home to endangered and protected white clawed crayfish so a plan of works was submitted to the Environment Agency; they approved  and granted a licence for the work to proceed.
Work began on Tuesday, September 20th.

The first task was to use nets to catch the crayfish in the vicinity of the work site and then move them away to a safe distance. Above from left to right...Bekka, from South Cumbria Rivers Trust and a licenced crayfish handler, supervised the capture and handling of the crayfish. James, NT Area Ranger and Bruna, NT Academy Ranger. 
While James carefully lifts a large pitching stone, dislodged in the flood, Bekka is using a bathyscope to view any crayfish that may be taking refuge underneath.  
A crayfish is gently deposited into a container ready to be moved away from the work-site to safety. Nearly seventy crayfish were caught in an area of approximately only six square metres!
Little and Large.
The word crayfish is derived from Old French... escrevisse.

 White clawed crayfish (Austropotomobius pallipes) are on the IUCN Red Data List of threatened species. (International Union for The Conservation of Nature). Classified as endangered, they are the UK's only native crayfish.
The UK is the most north westerly limit of their range.

Once widespread, Cumbria is now the last major stronghold for the native white clawed crayfish in England; they are not found north of the border.
Native crayfish numbers have declined drastically since the introduction of the American signal crayfish in the seventies. This alien species carries a fugal plague that is fatal to the white clawed crayfish.
This specimen is an adult male. Their claws are usually larger than the female's. 
Crayfish are capable of a surprising turn of speed.
Bruna,..her reflexes are amazing...scooping up another crayfish!
Numbers, sex, size and condition of the crayfish are noted down for the records.
With the area cleared of crayfish repairs to the pitching work may at last begin!
The scattered pitching stones still had to be carefully lifted up in case any crayfish had escaped the initial search...of course some had and these too were moved to safety!
Straw bales were used to filter out sediment arising from the repair work. Crayfish are intolerant of sediment as it clogs their gills.
Work well underway with just the retaining wall to be completed.
On the day the work was finished (21st September), a thunderstorm broke out during the night. The torrential rain considerably increased the flow of Scout Beck giving the repaired stone work a stern test; this image was taken on the morning of the 22nd September.

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