During a volunteer work day dismantling a bridge, staff and volunteers dropped a nut & washer into the stream. While searching to retrieve them, they reported a possible sighting of White-clawed Crayfish.

The headwaters of the Bishopston Stream present the ideal habitat for White-clawed Crayfish. Rocky stream bed and stream banks made up of soft substrates. The tributaries to the north of Barlands Common are isolated from the downstream part by a long section of underwater stream.

White-clawed Crayfish are a rare and struggling species. The idea of them possibly being in an isolated section of stream on one of our reserves was exciting. 

But how could we confirm whether they really are present?

Our "Protecting tomorrow by managing invasive species today" project allowed us to carry out e-DNA sampling. Whilst carrying out the sampling we decided to also test for the invasive non-native North American Signal crayfish. This larger and more aggressive species is one of the biggest threats to our native White-clawed Crayfish.  

Sadly the results came back negative for the presence of our native species. North American Signal Crayfish were detected at all three sample locations. Signal Crayfish populations are established in many watercourses throughout Wales and England. Their unwelcome impact is that they spread crayfish plague, the big threat to our native White-clawed. They can also de-stabilise riverbanks through burrowing. And, they have a large impact on native species by feeding on fish and amphibian eggs, young fish and other aquatic species.