Killer shrimp (Dikerogammarus villosus) is a highly invasive shrimp which can be considerably larger than our native shrimps, growing up to 30mm in length and usually has a striped appearance, although it can be uniform in colour.
Native to the Black Sea, killer shrimp have spread over western Europe in the last 20 years, most probably through commercial shipping.
Killer shrimp live for about one year, and are fast breeders, with the females able to produce three broods, each with an average of 150 eggs per brood. Killer shrimp are able to tolerate a range of environmental conditions, but they prefer to colonise waters with moderate to slow flow speeds, instead using faster-moving water to drift to new locations. Usually nocturnal, killer shrimp spend the daylight hours hidden away.
First discovered in British waters in 2010, killer shrimp is considered to be one of the most damaging invasive species in Europe, with the potential to significantly affect the ecology of our major rivers, canals and lakes. The shrimp preys on a range of native species, such as freshwater invertebrates - particularly native shrimp - and even young fish. It often kills its prey and leaves it uneaten. This alters the ecology of habitats it invades, and could cause extinctions.
Species at risk are thought to include many insects such as damselflies and water boatmen, as well as the other species which feed on these insects.