Improving freshwater systems – the Case of the Crayfish

The Trust have identified issues with American Signal Crayfish in the Soar catchment area, and since 2017 have been running a research programme to identify population size within the brook around the Burrough Court farm.  An active eradication programme is in place with a significant amount of crayfish being removed from the system each year. In 2019 our staff, trainees and volunteers removed over 1,000 crayfish from a 1.5km length of freshwater, indicating the extent of the problem.  The Crayfish had caused significant problems with the freshwater systems around the farm adding to flooding, pollution and sedimentation all of which reduce environmental and biodiversity levels. 

American Signal Crayfish were reared in the UK during the 1970’s and sold to restaurants as a replacement to the native white-clawed crayfish (following a population crash due to the crayfish plague) . Signal crayfish escaped and due to their aggressive and competitive nature, they soon dominated waterways and are now classed an invasive species.  

Impacts 

Soil erosion and flooding – Signal crayfish burrow into river and canal banks and as a result they increase the amount of sediment entering the water. Their burrowing activity also causes bank collapse and this increases flood risk. 

Water pollution – The sediments found along the bankside of farm streams and watercourses often contain nitrogen, phosphorus and the residues of pesticides and herbicides used to manage crops. This sediment pollution can cause increases in pollution in the water body. 

Biodiversity loss – White clawed crayfish numbers have reduced between 50 – 80% in the last 10 years and is now endangered. Signal crayfish are  aggressive and easily outcompete their native cousins. They can decimate a food chain because they feed on almost everything in the water body, and when resources are low, they can cannibalise their own species. Their burrows can be up to 2m deep with a network of many interconnecting tunnels and have been known to displace the native water vole. They can travel across land quickly (with records showing they can travel several hundred metres during one night to reach water). 

What we are doing about it 

The Sustainable Land Trust works with the Environment Agency and holds a research licence to trap, record, and carry out humane destruction techniques. The Trust recognises this is not a long term sustainable solution as the species breeds quickly and therefore easily replace populations taken out of the water system.  

What do we want to do next  

Having recognised the significance of the issue, we are now looking for funding to train volunteers to work with farmers, landowners, anglers and canoeists to raise awareness of the issue so they can improve biosecurity and reduce the spread of the species across farms, waterways and landscapes,  and to improve water habitats so they can support otters and eels which are known to predate upon the species. 

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