Looking after native species

What are White-clawed Crayfish?

The White-clawed Crayfish is our only native Crayfish and is the largest freshwater invertebrate in the UK. Sadly, their numbers have declined significantly over the last ten years, with a loss of 50-80% across its European range and it is now classified as ‘endangered’ and at risk of extinction.

Their decline has primarily been caused by the invasion of a non-native species the American Signal Crayfish. Signal Crayfish out compete the White-clawed Crayfish for homes and food, they carry a disease called Crayfish plague which is harmless to themselves but lethal to White-clawed Crayfish and they are bigger and stronger than the White-clawed and can eat them! Other contributing factors to the fall in their numbers include loss of habitat and pollution in the rivers.

What is the connection to Wallington?

Wallington is one of the few places in England that continues to have a healthy population of White-clawed Crayfish, with no invasive species present. Living in the River Wansbeck and its tributaries, which meander through the 13,500 acre estate, the White-clawed Crayfish are now the focus of a conservation project led by the Countryside team at Wallington, looking to safeguard their future on the estate. We are also working in partnership with other interested conservation bodies such as the Environment Agency, Northumberland Wildlife Trust, Northumberland National Park and the Rivers Trusts to protect this endangered species across the North East of England.

The Project – what’s the conservation plan?

The first step is to find out exactly where across the 20 square mile Wallington estate the White Clawed Crayfish are located. As such, the team at Wallington have recently been laying artificial refuge ‘traps’ at a number of different locations in the River. These don’t actually trap the Crayfish, they simply provide a home or ‘refuge’ for them from which they can come and go. They are a series of open-ended pipes, attached to a baseplate, which are placed in the river in locations attractive to the Crayfish. They naturally seek refuge under stones and they are attracted to these dark, safe refuge ‘traps’. Left in situ for a period of approximately 3 weeks, the team then recover the traps, lifting each to record what is found within. Each Crayfish is measured and a record is made of its sex, any disease or damage present and stage of moult (the process by which Crayfish shed their hard outer shell).

Once the surveying is complete, we will be able to identify strategies to protect and enhance the populations of White-clawed Crayfish. This will be achieved through improving our understanding of the threats to populations, agreeing our priorities and taking appropriate actions. We’ll be looking at how we can reduce the risk from invasive species and increasing existing populations through informed habitat and land management practices.

We will also be looking for suitable ‘Arc’ sites. These are sites which don’t currently have populations of White-clawed Crayfish but are suitable habitats and are isolated from the risks associated with the Signal Crayfish. We can then move some White-clawed Crayfish from a healthy population to the ‘Arc’ site.  This would then mean if the worst case scenario was to happen and a population of White-clawed crayfish was wiped out by plague they could be re-populated from the 'Arc' site.  

There’s a lot to be done but things are underway.

What can you do to help?

It is very easy to make small changes, which can help protect the White-clawed Crayfish. In the very first instance, you can help limit the transfer of Crayfish plague, which devastates populations of White-clawed Crayfish and is easily transferred between watercourses. In order for you to play your part in the protection of this species, we ask you to follow the CLEAN-CHECK-DRY set of principles if you have been in water.

The cause of Crayfish Plague is a water mould which attacks the soft tissue of crayfish and has a 100% mortality rate. Were it to get into the upper catchment of a river it would wipe out an entire population within a couple of weeks. You can unwittingly transfer it from one watercourse to another on items such as wellies, clothing and even on your dog! The microscopic spores can survive out of water for 48 hours and if in wet or muddy items it can survive for up to 3 weeks. If accessing our watercourses we would ask that that people follow the Check, Clean, Dry protocol for biosecurity for invasive species. This link will tell you more about what to do http://www.nonnativespecies.org/checkcleandry/

Next steps

Whilst we’re busy with the first stages of the project, you can keep an eye out for updates on our social media channels and website. We’ll be making sure that we keep you up to speed on the results of our initial survey. We can’t wait to share what we find out!