Invasive Signal Crayfish have now been found at a number of locations on the River Rye; the result of either deliberate release or poor biosecurity measures. These are a threat to our native White-Clawed Crayfish. With this in mind Duncan Fyfe, EA Catchment Coordinator reminds all who have an interest in the wider water environment – be it flood risk and land drainage, fishing or ecology – of the importance of taking biosecurity very seriously.
Failure to do so can result in rapid and widespread ‘invasions’ of a host of unwanted plant and animal species that can have a devastating impact not only upon native wildlife but upon flood risk too. Invasive Non Native Species (INNS) such as Himalayan Balsam will out compete native plant species and when they die back in the winter they leave bare ground, exposing river banks, streams and ditches to erosion. The Environment Agency and Natural England have been working with the Yorkshire Wildlife Trust and East Yorkshire Rivers Trust through the Derwent Restoration Project to map the extent of INNS problem on the Derwent and develop an action plan to control the spread.
Signal crayfish are not as immediately visible as Himalayan Balsam but the potential impacts are no less real and are serious for both ecology and flood risk. Until very recently the only known and established population on the Derwent was on Settrington Beck. However, they have now been found at a number of locations including the Seph and Riccal.
Signal Crayfish represent a very real threat to our native White–Clawed Crayfish – a protected species that is declining in this country. However, many rivers and streams in Yorkshire still contain good populations of White-Clawed Crayfish which is why its important to protect them. The invasive Signal Crayfish, introduced from North America are a larger, more aggressive species which outcompetes our native crayfish and can impact upon the wider food chain. Once established they may burrow into the banks of ditches, streams and rivers exacerbating erosion and bank collapse. They also carry a plague, caused by a water mould which is fatal to White-Clawed Crayfish.
Crayfish plague can be transferred between rivers by equipment and clothing if you enter the water. However, there are things that you can do to stop the spread of crayfish plague by taking appropriate biosecurity measures. All who work outdoors on the Derwent should be doing this as a matter of routine.
Biosecurity Measures to prevent spread of Crayfish Plague and other INNS.
The mantra is Check, Clean, Dry!
- It is good practice to do a visual check of all machinery, equioment and clothing, such as waders before you leave the site – Signal Crayfish have been known to cling to machines. Himalayan Balsam or other invasive plants can be carried off site too in the tracks of machinery
- A disinfectant may be used to clean kit, alternatively ensure nets, and all equipment is allowed to completely dry before putting into another watercourse.
Leeds University has developed a free on line training tool on biosecurity training which is available on the Leeds university website:
I have also attached a fact sheet on the Signal Crayfish and there is a link below to the Non Native Species website that has in turn lots of information about the Check Clean Dry Campaign and the whole host of other invasive species we need to be mindful of.