River Barle Crayfish Project
In 2014 a population of the signal crayfish (Pacifastacus leniusculus) was found along a five mile stretch of the River Barle, designated a Site of Special Scientific Interest (SSSI) for its unmodified natural ecosystem.
Signal crayfish are one of the most widespread and damaging non-native invasive species in the UK. They are responsible for severe declines in populations of the native white-clawed crayfish (Austropotamobius pallipes) as well as having notable effects on wider floral and faunal communities. Negative impacts include:
- Carrier of the crayfish plague (Aphanomyces astaci) which our native crayfish are very susceptible to.
- Predation
- Competition for food and shelter from predators
- Increased siltation and flooding due to a high degree of burrowing in riverbanks leading to erosion.
The Trial
The River Barle Signal Crayfish Project, led by Nicky Green Associates, is an innovative volunteer focused approach attempting to control signal crayfish within our trial area on the River Barle. The project started in 2015 and the combination of trapping and male sterilisation has not been trialled in the UK before.
Our dedicated team of volunteers are out on the River Barle between April and October. Artificial refuge traps are checked weekly, the larger males are sterilised and returned and all other signal crayfish are humanely dispatched on site. Important information relating to the population structure is collected to help us determine if this method is working and so far, the results are looking promising.
You can find out more about the River Barle Signal Crayfish Project from the video below, an episode from ‘Nature Natters’ North Devon Biosphere’s ‘Pledge for Nature Project. Pledge for Nature hopes to inspire you to take action for nature. www.biosphere.org.uk/pledgefornature
We need your help!
Alongside the River Barle Signal Crayfish Project we have volunteers surveying for signal crayfish on some of Exmoor's other rivers and have since discovered them on the Exe as a result. If you have seen any invasive species within the National Park or would like to volunteer please visit our Get Involved page.
We can also give advice, so if you have an invasive species on your land that you are looking to control please do not hesitate to get in touch by email or phone.
It's really important that only trained volunteers and staff handle crayfish. Catching crayfish can seem fun, but it can have a devastating impact on our native species. Did you know it is illegal to trap crayfish without an Environment Agency licence and illegal to transport live crayfish? Catching crayfish also requires landowner permission. People often want to catch larger individuals as they will have more meat but, as crayfish are cannibalistic, removing larger crayfish allows lots of smaller crayfish to thrive and may have the result of increasing the invasive Signal Crayfish population. Transporting crayfish to other areas may also spread crayfish plague which is fatal to our native crayfish. There are populations of crayfish on Exmoor that have be subject to research since 2015 and encouraging people to go out and catch crayfish in these areas will have an impact on the data collected and skew the results.