Our South Cornwall team made an unusual find this week while carrying out some fish surveys on the rivers of South Cornwall. Matt Healey, Field Officer on the South Cornwall River Improvement Project, said, “We were out doing some electro-fishing when we unexpectedly came across two signal crayfish, a rare sight here in Cornwall.”
Signal crayfish were originally brought over from the United States and farmed as a commercial species, before they escaped and started colonising British rivers and streams. They pose a threat to our native white-clawed crayfish because they out-compete the natives for food resources. Signal crayfish also carry a potentially lethal disease which has spread throughout many native populations and caused a rapid decline in white-clawed crayfish population numbers.
Matt continued, “What makes this sighting unusual is that crayfish records are virtually unheard of in Cornwall. There are no records of white-clawed crayfish anywhere in the county at all. This is because of the predominantly acidic nature of the soils and underlying geology, making for unsuitable aquatic conditions for crayfish, as their exoskeleton is partly made up of calcium salts.”
Although finding signal crayfish in a Cornish stream can in general be considered bad news, the presence of crayfish at all is certainly an interesting find. Sadly, the pair caught this week, who were nicknamed Ronnie and Reggie (after the infamous Cray brothers), had reached the end of their time in this particular stream, as the law prohibits re-release of this invasive non-native species once caught.
There’s lots more useful information about crayfish in Britain on the Buglife website here:
http://www.buglife.org.uk/conservation/currentprojects/Species+Action/UK+Crayfish+Website
Significant populations of Crayfish have also recently been found on the Kensey near Egloskerry. The EA Trapped 19 in one trap in 24 hours! Further populations have been discovered on the Wolf.
If you know of more you should probably talk to Robert Hurrel at the EA who is investigating the Kensey and Wolf.
William
So what is the situation with trap catching the signals, do I need permission to trap them,
Hi Dave. Yes to trap crayfish you need a License from the EA https://www.gov.uk/guidance/permission-to-trap-crayfish-eels-elvers-salmon-and-sea-trout
Have crayfish been found on the fowey or camel rivers?
Hi Nick,
Signal Crayfish fave been found in the Upper Fowey but thankfully the Camel seems to be clear of them!
Hi,
Many thanks for your response, am I correct in thinking theses are the invader species, and is this at the upper fowey on the moor or further down?
Regards
Nick
Ps have they been found in great numbers?
They are in Draynes Valley, I don’t think they are there in huge numbers. And yes, Signals are an invasive species
Has anyone found significant number of signal crayfish in or around hayle?
Hi there, I live in Cornwall and I am trying to find a good population of crayfish. Dose anyone know any rivers or lakes to try out many thanks
So 7 years after how are the rivers doing ? What rivers in Cornwall are affected
Hello Ash – Buglife and the EA would be good contacts for details of Signal Crayfish populations in Cornwall. There may be some on parts of the Fowey Catchment and Par Catchment, and potentially elsewhere.
You could try the public data dashboard | Online wildlife Recording for Kernow & Scilly at erccis.org.uk – https://erccis.org.uk/explore/public/dashboard.
Hope this helps.