An invasive species of crustacean known as the killer shrimp (Dikerogammarus villosus) is feared to be establishing itself in the UK. First identified at Grafham Water in Cambridgeshire in September 2010, it has since been identified at two locations in Wales, and may be present elsewhere.

Already, surveys are being planned for high-risk sites in Wales, and at a large number of Sites of Special Scientific Interest (SSSIs) in England, to identify whether D. villosus is present there.

A campaign has been launched by a Task Group comprising the Environment Agency, Defra, and the Centre for Ecology & Hydrology among others. This will assess the risk of spread, carry out surveys, and raise awareness and about human vectors.

Killer shrimps can be transferred on boots, nets, boats, angling kit, and other aquatic equipment. A biosecurity poster alerting the public is available here:

www.environment-agency.gov.uk/static/documents/Leisure/Dikerogammarus-villosus-wanted.pdf.  

The killer shrimp inhabits freshwater or brackish lakes and other water-bodies with stony or gravelly bottoms. It voraciously predates, kills and out-competes other species.

Killer shrimps reach around 30mm in length, much bigger than the native British freshwater shrimp (Gammarus pulex) which reach 21mm (males) or 14mm (females). The invasive shrimps may be stripy in appearance, or lacking obvious markings. 

The name 'killer shrimp' refers to its voracious predatory and competitive nature. It is a threat to many native invertebrates and young fish, which it kills, and not always to eat. It can alter entire ecosystems.

D. villosus originates from the Ponto-Caspian region of eastern Europe, the grassy Steppe plains from Ukraine to Kazakhstan. It has become an invasive species across Western Europe. With a lifecycle of 4-8 weeks, it is able to spread quickly in many freshwater environments.

For more information or updates, visit the GB Non Native Species Secretariat website: secure.fera.defra.gov.uk/nonnativespecies/home/index.cfm