We have been working with Bristol University PhD student Jack Greenhalgh on the distribution of invasive signal crayfish in our becks. For his PhD Jack is developing novel methods of detecting crayfish using environmental DNA (eDNA) from filtered water samples.
Jack and his PhD student colleague Duncan Edgley, spent a week with us in early September taking samples from our four main becks.
We have known for a long time that there were populations of invasive crayfish in Town Beck and Back Beck, but we wanted to find out how far up the becks the crayfish had moved and whether they had invaded Lumb Beck.
After months of lab work back in Bristol Jack has now sent us his results (see map). He detected crayfish DNA at all sites where crayfish were found by hand sampling (see a small one in Jack’s hand!) in Town Beck and Back Beck.
The good news is that crayfish haven’t (yet) moved up Town Beck beyond the Townhead Trading Estate or up Back Beck beyond Bridge 55. The long culvert at Townhead and the high step at Bridge 55 may be acting as barriers.
The bad news, however, is that crayfish DNA was found in Lumb Beck. No crayfish were found by hand sampling and we have not had any sightings of crayfish in Lumb Beck. This is a worrying discovery as there are no barriers to upstream movement in Lumb Beck.
Thanks to Maire, Lesley, Jan and Duncan for their help in the field! And thanks to Jack for his excellent work and his interest in trialling his new methods in our becks.