Chinese mitten crabs are officially listed as one of the World's 100 worst invasive species. They can cause damage to fishing gear and river banks, block intake screens, modify natural habitats and compete with native species. It is this economic and ecological damage that makes this crab such an unwelcome arrival. The full extent of these exotic pests in English and Welsh waters is currently unclear and by reporting any sightings of these crabs, you may help research institutions gain a greater understanding of the distribution of these species and how to prevent further damage.
If you have the iNaturalist app (available on iOS and Android), a useful tool to record any wildlife sightings both in the UK and overseas, you can submit the record directly on the app or via the iNaturalistUK website. You can also upload records to iRecord, which like iNaturalistUK, shares the data with the NBN Atlas, a national biodiversity database. Alternatively, you can email the Marine Biological Association through dassh.enquiries@mba.ac.uk with your photograph, location, time and date of the sighting and they can record the sighting for you.