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Undergraduate study detects invasive shrimp

03 March 2011

Dikerogammarus villosus females resting on zebra musselsDikerogammarus villosus females resting on zebra mussels

An invasive and damaging species of shrimp is more widespread in Cardiff Bay than first thought, a University undergraduate’s research has shown.

Dikerogammarus villosus, dubbed "killer shrimp" by scientists, was discovered during November at two Welsh sites, Cardiff Bay and Eglwys Nunydd. University investigations have now revealed that the Cardiff Bay population is well-established and already extremely large. Cardiff researchers are now working with other agencies to control the shrimp in Wales and to understand its potential effects.

Zoology student Caroline Rees, from the School of Biosciences, first made the discovery during work for her undergraduate dissertation. While studying another invasive species, the zebra mussel, she found Dikerogammarus distributed across large areas of the 200 hectare Bay at densities sometimes greater than 4,000 per square metre.

Cardiff Bay now contains many millions of the invasive zebra mussels, which share the origins of Dikerogammarus in the region around the Black Sea and the Caspian Sea. This could explain why the shrimp has done so well since its chance arrival in the Bay.

Caroline’s supervisor, Professor Steve Ormerod, School of Biosciences, said: "The shrimp population must have developed very rapidly over the last one to two years because we did not find it during very extensive surveys of zebra mussels during 2006-2009. It appears to be taking advantage of the large aggregations of the zebra mussel, which is also an invader. The shrimp is using the zebra mussel beds as habitat and may well be feeding on their waste."

Caroline ReesCaroline Rees

The invasion of Britain by the "killer shrimp" worries environmentalists because of its likely effects as a predator and competitor of other freshwater species. The shrimp can establish large, damaging populations very quickly from just small numbers. The shrimp has also been found at one other UK location, Grafham Water in Cambridgeshire.

The Environment Agency and Cardiff Harbour Authority have been informed of the Cardiff team’s findings and have supported their investigations. The Welsh Assembly Government and Defra have established a national Task Group to tackle the shrimp in England and Wales that includes Environment Agency Wales and the Countryside Council for Wales.

The national Task Group urges that anyone who uses waters where the shrimp are present to take steps to prevent the species from spreading. Simple things like cleaning and drying equipment thoroughly after use and checking equipment when leaving the water are vital.

Professor Ormerod said it was crucial to enforce as stringently as possible the biosecurity measures put in place by the authorities to contain both invasive species in the Bay. Understanding the ecological effects and developing control methods are now urgent priorities.

Professor Ormerod said: "The presence of zebra mussels is a complicating factor at the Cardiff site, and stringent biosecurity should benefit the battle to contain this species as well. Zebra mussels now number many millions in Cardiff Bay, and in the summer every single litre of water contains 10-15 of their larvae which could so easily be transported to other lakes."

Chris Mills, Director, Environment Agency Wales said: "As the national action programme develops, the most important thing is to contain the shrimp. We ask that people who use Cardiff Bay and Eglwys Nunydd follow the Task Group’s advice to help tackle this unwelcome guest."