What’s the problem? Dikerogammarus villosus was found in Cardiff Bay, Grafham Water and Eglwys Nunnyd reservoir in 2010, and the Norfolk Broads by 2012. D. haemobaphes was found in the Severn in 2012, followed by the Thames, Trent, Witham, and Kennet and Avon Canal. Both Ponto-caspian shrimp are a very serious threat to native species, they can live in a wide range of aquatic habitats, with low oxygen levels and even 20 per cent salinity. Growing up to 30 mm long, D. villosus are much larger than native freshwater shrimp, and have been dubbed “killer shrimp” for their tendency to shred prey without eating it. Other invertebrates, fish eggs and juvenile fish may be attacked, with vulnerable species driven into local extinction. Research on the River Churnet shows that D. haemobaphes, the “demon shrimp”, is likely to have a similar impact.
What you can do
Take careful biosecurity measures when you leave an area where Ponto-caspian shrimp are present. Apart from stringent biosecurity, no effective means of control are currently known. NB: If you suspect you’ve seen these shrimp in any other locations, email details and a photograph to alert_nonnative@ ceh.ac.uk as soon as possible.