Once widespread in English streams and rivers, the white-clawed crayfish is now severely threatened and is close to extinction in Devon. The Upper Culm provides a fragile sanctuary to a small population of these fascinating creatures, which are the UK’s largest native freshwater invertebrate (ie an animal with a hard external skeleton). Only one other river in Devon also provides a home, and the situation is equally bleak in other English counties. It is classified as ‘endangered’ on the International Union for Conservation of Nature (IUCN) red list of threatened species and is at risk of global extinction.
One of the reasons we want to make the Culm a healthier river is to give the white-clawed crayfish a safe haven here in Devon. And, because the white-claw needs clear, unpolluted waters, it’s a good indicator of general river health.
It’s not only poor water quality that threatens the white-claw. An invasive sister species, the American signal crayfish, was introduced to this country around 40 years ago as a source of food. Much larger than the white-claw, it is more tolerant of poor water-quality and, fatally, it carries a virus called “crayfish plague” that kills white-claws. It also competes with our native crayfish for food. All told, signal crayfish are bad news for our native wildlife and they are present in large numbers on the Upper Culm, both upstream and downstream of the surviving white-claw colonies.
Since the white-claws of the Culm were re-discovered in 2010, they have been under close inspection and are now regularly surveyed. In 2018-19, through the Culm Community Crayfish project, funded by the Heritage Lottery Fund, we were able to recruit and train a team of crayfish surveyors (because they are endangered, you need a licence to survey for them). By monitoring closely and improving their habitat in the river, we can give them a fighting chance.
A short film about the white-clawed crayfish of the Culm
What can I do to help white-clawed crayfish?
Crayfish plague can be easily spread between sites, for example on wet angling kit, dogs or footwear.
There are some simple things that you can do to help to prevent the spread of crayfish plague such as following the ‘check, clean, dry’ code to stop the spread of crayfish plague.
- Get involved as a volunteer crayfish surveyor.
- Talk to us about how you could manage your land to help the white-clawed crayfish.
- If you are fishing in or using the river, check your equipment and clothing for live organisms and mud that could carry crayfish plague spores.
- Clean and wash all equipment, footwear and clothes thoroughly.
- Dry all equipment and clothing – some species can live for many days in moist conditions. Make sure you don’t transfer water elsewhere.
Find out more about white-clawed crayfish here.