A population of 'killer shrimps' has spread to Wroxham Broad, prompting an urgent plea for boat users to 'check, clean and dry' any equipment which has been in contact with the water.

The invasive, non-native species dikerogammarus villosus had previously been recorded in Barton Broad, the associated River Ant system and a small area around the confluence of the Rivers Ant and Bure.

But on Thursday, the Environment Agency's monitoring programme found the shrimp at Wroxham – indicating the species is slowly spreading through Broadland.

The Environment Agency, Natural England and the Broads Authority are working together to monitor the spread and investigate the impact of the tiny 3cm shrimp.

If it becomes established and widespread, as other invasive species such as floating pennywort and signal crayfish have, conservationists warn it could threaten the native creatures which it feeds on, like damselfly nymphs, water boatmen and small fish.

Andrea Kelly, senior ecologist for the Broads Authority, said: 'People checking, cleaning and drying their equipment after use is essential to help stop the spread of all non-native species and we would really appreciate their full cooperation in doing this.

'We are working with our partners to investigate the shrimps' current population and range in the Broads and to investigate and implement measures to limit its spread to and from other water courses. There is no risk to the public or their pets from it.'

The Check Clean Dry campaign asks all water users to take simple steps to help prevent the spread of all non-native species between rivers, lakes and reservoirs. Clothing and equipment that has come in contact with the water should be checked for any living organisms and then thoroughly washed-down. Any organisms found should be returned to the water body they came from. Equipment and clothing should be dried as some species can survive for days in damp conditions.

Andrew Raine, from the environment monitoring team at the Environment Agency, said: 'As human activity is the most likely cause of spreading killer shrimp between sites it's imperative that all water users consider their actions particularly if they are moving equipment between water bodies whether that be boats, canoes or fishing nets.'