Killer shrimp: Advice for customers visiting our recreational sites

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On 3 September 2010, a species of shrimp never before found in the UK was discovered at Graftham Water, a reservoir in Cambridgeshire run by Anglian Water.

The shrimp, known as 'dikerogammarus villosus' is more commonly known as the 'killer shrimp', due to its voracious appetite.

The shrimp can grow to 3cm in length, much larger than our native species. It kills a range of native species, such as young shrimps, fish, and other insects - as a result, it can alter the ecology of the habitats that it enters, sometimes causing the extinction of native species.

The Environment Agency is determining the extent of the problem in the UK, but in the meantime it is important that we take practical action now to avoid the spread of this species.

Good practice and guidance measures for recreational users

We are asking for your help to prevent the spread of this invasive species by following some simple measures.

When visiting one of our sites:

  • Anglers - please ensure that your nets and equipment are dry and that they have been thoroughly cleaned since last used. In particular we would ask you to visually check for any signs of the shrimp, which has striped or spotted markings and relatively large mandibles.
  • Sailors and windsurfers - please ensure that your boats / boards have been washed since they were last used and that bilge pumps are empty.

When leaving one of our sites:

  • Visually check all equipment that has come in contact with the water, for signs of the shrimp.
  • Wash down boats and windsurfing equipment, ensuring that the washwater does not drain into the reservoir.

We ask any users also using Grafham Water to take particular care in following these guidelines.

What to do if you find a shrimp

If you think that you have found one please check with the identification details on the non-native species secretariat website. Images of suspected non-native shrimp can be sent to

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