New DNA testing has revealed the presence of an endangered native fish, in a stream near Ilkley. Detailed Environment Agency tests revealed the presence of endangered native white-clawed crayfish at Carr Beck, Burley Woodhead.
An innovative procedure was used, that seeks out DNA from sloughed off cells of organisms present in the environment.
Samples are then collected, sent off to a laboratory and tested to verify the presence or absence of crayfish in the beck system.
Since native crayfish were confirmed as being present, the Environment Agency’s Fisheries Biodiversity and Geomorphology team has monitored the situation.
A suitable ark site is being sought, to relocate the crayfish to if necessary.
An ark site is somewhere that allows a species such as white-clawed crayfish to exist in an isolated refuge site, away from the dangers of non-native crayfish disease and other threats.
The survey was done after the Environment Agency applied to Defra for a drought order when water levels were low at the end of last summer, to reduce water flowing into Carr Beck from Carr Bottom Reservoir for a while.
At this time the presence of white-clawed crayfish in the beck was uncertain.
Environment Agency officer Sue Penn said: “Now we know native white-clawed crayfish are in the beck, we will monitor the crayfish and move them to a suitable ark site, if it becomes necessary.
“The reservoir was not being used by Yorkshire Water for public water supply at the time, but levels were low and there would otherwise be a risk that compensation water flow into the beck might have to stop altogether.
“Reducing the flow of water allows the compensation release to continue for longer if dry conditions continued.
“The drought order application was subsequently withdrawn as the reservoir refilled, due to substantial rainfall during December.
“In our application to Defra, we considered the likely effect of the reduced flow on the environment.
“We did not know if native crayfish were in Carr Beck, so we surveyed to find out.”