'Ark' will ensure survival of native crayfish
By Martin Paul - Senior Reporter
A SMALL beck feeding into the River Balder, near Cotherstone, could soon play an important part in saving the UK’s only native freshwater crayfish from extinction.
Plans are afoot to turn a section of the beck into an “ark” to protect its population of white-clawed crayfish.
It is one of only a handful of streams in the River Tees catchment area where the species still exists.
Now conservation groups – including Darlington and Teesdale Naturalists' Field Club, the Environment Agency, the Tees Rivers Trust, Durham University and North Pennines AONB Partnership – are planning to working together to protect remaining populations.
The groups met at East Briscoe Farm Cottages earlier this month, to discuss the establishment of a crayfish ark nearby.
Ian Marshall, who is the Environment Agency’s white clawed crayfish conservation national lead, told the gathering that the native species came under threat following the introduction of alien species, including the signal crayfish, in the 1970s.
He blamed the Ministry for Agriculture, Fisheries and Food which had been promoting the farming of the invasive crayfish at the time.
He added that not only did the signal crayfish out-compete the British species, but it brought with it crayfish plague.
Mr Marshall said: “There is 100 per cent mortality when it gets into the white clawed crayfish population.”
He warned that something as simple as a fisherman wandering from an infected stream to an uninfected one could spread the disease.
The expert added: “It only takes one set of dirty wellies, one dirty net, to wipe out a whole population.”
Dr Martyn Lucas, of Durham University, who has been monitoring the spread of signal crayfish in Teesdale since 2011 said the species was also having an effect on fish populations, particularly on stone loach and bullhead.
He said: “Bullhead have declined by, on average, 80 per cent and at the same time the density of crayfish has gone up by 90 per cent. The bottom line is it is not a good situation to have signal crayfish and ot is important to get rid of them.”
Since his study began, signal crayfish had spread to Sudburn Beck, in Staindrop, Thorsgill Beck, at Egglestone Abbey and the River Lune, at Grassholme Reservoir.
He added: “They turned up in Grassholme reservoir and suddenly downstream the Lune is full of them. Someone, somewhere illegally released them.”
Mr Marshall said white-clawed crayfish arks need to be established in areas that are “physically, chemically and biologically remote” such as quarries, or upstream from waterfalls or dams.
Ben Lamb, of the Tees Rivers Trust, said the beck at East Briscoe had potential to be turned into an ark.
He said: “The population here is really good and if there is any way to protect that we should do it.”
Also attending the gathering was Darlington MP Jenny Chapman who was last year declared white-clawed crayfish species champion by Bug Life UK.