Once a very common inhabitant of Dales waterways, numbers of the white-clawed crayfish are dwindling partially due to an invasion of an American variant. Jenny Cornish talks to a Settle firm helping to protect the species
At a secret location deep in the Yorkshire Dales, a battle is commencing to save a native species, which is being targeted by foreign invaders and biological warfare.
Numbers of the white-clawed crayfish, Britain’s only native crayfish, have been dwindling for years, due to water pollution, the invasion of the American crayfish, and a disease brought in by the intruders.
But now PBA Applied Ecology, a small company in Settle is working with the Environment Agency to breed the native crayfish and release them back into the wild.
Paul Bradley, director of PBA, said: “The white-clawed crayfish used to be really common in the Yorkshire Dales and in the Craven area – people used to be able to find them all over Craven. They prefer rivers coming off limestone and this area is ideal for them.
“They are facing three problems. The first problem is water pollution. Then they face the problem of an invasive crayfish, the American crayfish. The third is a disease that’s being brought in by the American crayfish – kind of like biological warfare. It’s known as crayfish plague. It’s killed millions of crayfish in the area.”
PBA has set up a captive breeding programme and currently has about 200 crayfish, onto the fourth and fifth generations. They have just released the first 20 back into the wild – just 14 females and six males, but each female will produce around 100 eggs.
“We’ve set up what’s become the most successful breeding site for white claw crayfish,” said Paul. “The idea is that if we can take a small number and put them somewhere safe, where they can’t get this disease, if we breed them, then that’s giving them a better chance for the future.
“We’ve just done the first release from a captive breeding site, into a very carefully selected stream in the Yorkshire Dales, which we’ve been investigating for a couple of years now.
“We’re completely confident that it has the water quality that this species requires, and it’s protected from this disease by a very large waterfall. We call it the Ark site – because it’s like Noah’s Ark.”
Experts will monitor the site, which is being kept as a secret location due to the need to preserve the bio-security of the site, and because it is on private land.
They will revisit the stream next summer, at night when the crayfish are more active, to find out if the project has been successful.
The ecologists are also asking members of the public, particularly swimmers, boaters and fishermen, but anybody who goes into the water in the area, to be aware that they may be carrying species and diseases on their clothing and equipment.
Andy Blincow, an ecologist at PBA, said: “This is part of the broader problem which faces the Dales – the problem of invasive species. The government has just launched a campaign called ‘Check, Clean, Dry’ – we need this to protect the water courses and lakes within the Yorkshire Dales.
“The government is asking people to check before they go into rivers, that they are clean and they’re not carrying invasive species in from another site, and that they’re dry before they go in because that’s the best way of controlling the risk.”