How ‘alien’ invader’ is causing destruction in Norfolk

An environmental biologist is calling for volunteers to help carry out research into an 'alien invader' which is causing destruction in the Brecks.

The signal crayfish is causing damage to Britain's ponds, rivers and canals, and out-competes the country's native white-clawed crayfish on every front.

Now Abby Stancliffe-Vaughan, of Bury Road, Thetford, is researching their life in the Brecks and aims to discover whether trapping the invading crayfish has an effect on the size and sex ratios of their population. Signal crayfish are more fertile and faster growing than the white-clawed crayfish, and also carry crayfish plague, a fungal disease fatal to the white-clawed crayfish but which signal crayfish are mostly resistant to. They are also a predator of both plants and animals.

Ms Stancliffe-Vaughan, 43, a student at Anglia Ruskin University in Cambridge, who used to work for the Brecks Countryside Project, said inspiration from her study came from working with the Lark Angling and Preservation Society (LAPS).

'I was very heartened to see what this group were doing but at the same time there was this environmental problem being left to voluntary angling groups,' she said. 'It's really important that we understand more about the population structure of signal crayfish, especially the populations that have been trapped. Trapping is known to remove larger crayfish first, but as these are the most reproductively active this could have a long-term effect in reducing their population.'

The signal crayfish was introduced to the UK in the 1970s when farmers were encouraged to rear them as part of a farm-diversification initiative, but a number escaped. With large red claws and growing up to 30cm in length, the signal crayfish dwarf the native species, which are usually less than 10cm long.

Ms Stancliffe-Vaughan added: 'Signal crayfish are having a catastrophic impact on our indigenous white-clawed crayfish and the biodiversity of our rivers due to the erosion and siltation caused by their burrowing.'

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Anyone who could help with her fieldwork, which will involve data recording, trapping, collecting and sexing crayfish should email or call 07824 720405.

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