At first glance they don't look like the stuff of horror movies, but these little aquatic critters have been dubbed the "Killer Shrimps" for good reason.  They are voracious predators, killing a range of native species, including young fish, and can significantly alter ecosystems.

The Environment Agency fear they could soon start killing off native damselflies and water boatmen, which would impact on the species which in turn feed on them like birds and amphibians.

The Killer shrimps (Dikerogammarus villosus) were first discovered in England last September in Grafham Water, Cambridgeshire by a couple of keen-eyed anglers.  Although they pose no threat to humans, Anglian Water immediately put in precautionary biosecurity measures around Grafham Water in an effort to contain the shrimps.

They've now been found at two sites in Wales - Cardiff Bay and Eglwys Nunydd reservoir in Port Talbot.  The Welsh Assembly Government and Defra have considered the threat serious enough to establish a national task group to tackle the killer shrimps.

Originally from Eastern Europe, the shrimps have rapidly spread to nearly all of Western Europes large rivers (Rhône, Loire, Seine, Moselle, Meuse, Rhine, Main, Danude) and the Baltic Sea basin.  The shrimps range in size from 3mm to 30mm and thrive best amongst hard surfaces such as rock and gravel.

They're very similar in appearance to our native shrimps, but conical projections on the dorsal sides of the first and second tail segments distinguish them.  The corresponding segments on our native shrimps have fine hairs or spines, but no conical projections.

Anyone who thinks they may have seen one of the Killer Shrimps is asked to email a photograph to the Centre for Ecology & Hydrology for identification.  The address is: alert_nonnative@ceh.ac.uk

Related Pages

• Video Clip of Killer Shrimps (Dikerogammarus villosus)
• Freshwater Shrimps Fact File
• UK Safari Freshwater Wildlife Section
• UK Safari News