Wildlife Conservation Group in the

Forest of Dean


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22 August 2023

Dean Heritage Centre

Water sampling to check for Signal Crayfish


We met at the Dean Heritage Centre to do water sampling around the lake and the streams.

Invasive species pose a major threat to global biodiversity. In the UK, one of the most notorious of these invaders is Signal Crayfish, (Pacifastacus leniusculus).Their extensive burrowing has eroded river banks throughout the UK, and they pose a grave threat to native wildlife, including Britain's only native crayfish species, the White-Clawed Crayfish (Austropotamobius pallipes). Signal crayfish carry a disease known as crayfish plague, which is 100% lethal to the native white-clawed if contracted. But even signal crayfish free of the disease tend to outcompete their native counterparts over time. Pollution also threatens white-clawed crayfish across much of their range, and as a result, they have suffered tremendous declines, estimated at over 90% in some English counties, leaving them vulnerable to extinction.


The team are setting up their equipment which consisted of latex gloves, a pole with a dipper to collect a litre of water in a bag. Once collected, the water is filtered through a syringe and then an alcohol preservative is used for the samples to be taken to a scientific laboratory.

The water dipper is quite small so frequent lifting and pouring is required

This is the stream running into the Mill Pond with a beautiful old pack horse bridge which had been restored in recent years.