Mapping Killer Shrimp Colonies

Over 100 traps, that have been proved effective in Environment Agency trials, will be deployed at ‘high priority’ sites which offer the perfect habitat, such as boulders just below water, are used for water sports and recreation, or are important conservation areas, to check if the shrimp is present.

Two other trap designs and different types of bait are also being trialled by the Environment Agency. One is based on a trap for the non-native American signal crayfish, while the other is a drop net designed for catching larger shrimps and prawns. Both will be used in the national trapping programme this spring if the trials are successful.

The Dikerogammarus villosus‏ shrimp, nicknamed 'killer' because of its voracious appetite, was first discovered at Grafham Water, in Cambridgeshire, last Autumn. Within weeks it was also found at Cardiff Bay and Eglwys Nunydd Reservoir in Port Talbot.

Strict biosecurity measures requiring boaters and anglers to thoroughly clean and dry all equipment before and after use were immediately put in place at all three locations.

A Task Group, made up of biodiversity experts from the Environment Agency, Defra, Wales Assembly Government, Natural England and the Countryside Council for Wales, was also set up to advise on how to tackle the aggressive crustacean.

Task Group lead Paul Raven said: "This shrimp may be small but it poses a big threat to native wildlife in our rivers, lakes and streams. Native freshwater shrimps, damselflies and water boatmen could be particularly at risk, with knock-on effects on the species which feed on them.

"Since the first discovery at Grafham our focus has been on containing it through effective biosecurity measures and investigating how far it may have spread. Extensive monitoring of rivers, reservoirs and lakes through the winter has not uncovered any new colonies but trapping will now be used to help ensure no invasive shrimp populations go undetected.

"D. villosus has spread from the Black and Caspian Seas across most of Western Europe over the last 10 years and there are numerous ways it could have reached the UK – in the bilge waters in ships, on the bottom of a yacht or boat, on fishing tackle or on other water sports equipment.

“We'd like to thank all those anglers and boaters who are being highly responsible and supporting the containment measures. People can also help by reporting any suspected sightings of the shrimp – which at up to 30mm long can be much larger than our native shrimp and often has striped or spotted markings - to this email address: alert_nonnative@ceh.ac.uk’ or ‘to this website: http://www.brc.ac.uk/risc/alert.php?species=killer_shrimp”