Friends of the Dales recently met at The Knights Table, Stainforth, to see director of PBA Ecology, Paul Bradley and PBA Ecologist, Alex Gould.
The aim of the day was to learn more about one of the Yorkshire Dales’ most threatened species, the white-clawed crayfish and the conservation efforts which are in place to save it from local extinction.
Paul summarised the history of the species in the upper Ribblesdale catchment which had previously been home to a strong population of white-clawed crayfish.
The introduction and spread of the invasive American signal crayfish and the fungal-like pathogen crayfish plague now means our only native freshwater crayfish species has been lost from much of its former range.
However, Paul’s survey efforts had identified a relict population protected by a waterfall in the headwaters of the Yorkshire Dales.
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The waterfall forms a physical barrier which prevents the spread of invasive species and disease.
Crayfish from this population are now being used as breeding stock in one of the UK’s largest white-clawed crayfish captive breeding facilities in the Yorkshire Dales.
The aim being to use juveniles raised in the facility to try to reintroduce the species to parts of its former range.
The group went to visit the facility which is owned and managed by former Environment Agency fisheries officer Neil Handy. It is part of Stories in Stone, a scheme of conservation and community projects focused on the Ingleborough area.
It was opened in 2001 and refurbished in 2018. Since its refurbishment more than 250 juveniles have been bred and raised in the facility.
This local stock has been released into sites where the species has recently been lost.
One site is a private fishing tarn managed by Manchester Anglers’ Association. Until 2015 it had been home to one of the largest known still-water populations of white-clawed crayfish. But it suffered a catastrophic collapse in 2016, most likely caused by an outbreak of crayfish plague.
The first step to reintroduction is ensuring the site is able to support the species again. Bioassay tanks are installed which house live juveniles, their survival and health regularly monitored.
Once it has the all-clear, the first wave of reintroductions can begin under a licence from Natural England.
In 2018 they were reintroduced to suitable areas of the tarn and surveys in 2019 confirmed they had survived their first year in the tarn.