Crayfish in Devon
Devon has only two remaining fragile wild populations of WCC, both of which are under threat of extinction from expansion of American signal crayfish and declining water quality.
Creedy Yeo
Surveys during the summers of 2021 and 2022 established that a population of WCC survives along a 5km stretch of the Creedy Yeo river between Crediton and Newton St Cyres.
Native crayfish were previously found over a much wider length of the river but now only around 10% of the original population survives.
River Culm.
Signal crayfish have expanded downstream and WCC have disappeared from areas where the signals have moved into.
2022/23 surveys found that the WCC population is now mixed with signal crayfish.
River Culm
WCC were believed to have died out on the Culm in the 1980s but were rediscovered in 2006.
Extensive surveys in 2018/2019 established that a WCC population survived along a 4km stretch of river between Hemyock and Uffculme.
Surveys also found that signal crayfish populations are present above and below the native crayfish in the main river and its tributaries.
The WCC is slowly disappearing at the upstream edge of its range in
response to the downstream expansion of signal crayfish.
The Culm population is not yet fully mixed with signal crayfish–stretch of the river near Culmstock remains free of the invasive signal crayfish.