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Members of the public are being encouraged to report sightings of non-native species that threaten Britain's wildlife.
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The government has launched an appeal asking the public to track six non-native species that are threatening wildlife in the UK.
The Department for Environment, Food and Rural Affairs wants people to report any sightings of the species, including Chinese mitten crabs and zebra mussels.
Alison Debney, Marine and Freshwater Conservation: "The mussels have probably come through ballast water. Ballast water is the water that ships take on to keep them stable as they're crossing the seas.
"When it arrives at the destination dock, it will discharge this water into the river and then the zebra mussel, whether it's in its larvae form or as an egg will get into our rivers and then the colonies start to settle."
Once sightings have been reported online, experts from RISC, the Recording Invasive Species Counts project, will check the data to track the spread of the species and research ways that can limit their expansion. The records will then be added to a national database.
Non-native species are known to compete with, and prey on, other wildlife, as well as spread disease.
The species are estimated to cost the British economy at least £3 billion a year by threatening agriculture, forestry, fisheries and development.
To report a sighting of a non-native species visit the RISC website at www.nonnativespecies.org/recording
