White Clawed Crayfish

This week I attended a one day introductory workshop, organised via CIEEM, on the native white-clawed crayfish (Austropotamobius pallipes). It was held at an outdoor centre near the upper reaches of the River Kent near Windermere and run by Paul Bradley who runs his own consulting firm.

After a classroom session in the morning looking at the ecology of the species, the rest of the day was spent outdoors.

First, we walked up to the local reservoir. En route, we carried out a visual search of the river bank and saw claws discarded by feeding otters, so could confirm presence without even touching the water. At the reservoir, we raised some lobster pot type traps set the night before, and got three adult males out of eight traps.  We had a chance to have a look at the finer points of their physiology in the flesh, had a first go at handling them, and learnt how to measure the carapace length with dial callipers.

After a picnic lunch in the sun, we walked down to the stream and learned how to do a refuge search. The first crayfish caught by the tutor was a female still carrying young! We then had 15 minutes in the water in wellies trying to find crayfish. I found eight, but they are extremely fast and agile and difficult to catch. I did manage to catch two, and we got some more practise handling them as we filled in survey forms detailing their gender and size. 

Later in the afternoon we drove up to another reservoir, even further up the valley, and had a discussion about habitat management, species conservation, and how best to deal with invasive species. Our native white clawed crayfish are very vulnerable, due to predation and displacement by the larger more aggressive American signal crayfish, but also due to diseases being spread and carried by them and other introduced species. The importance of biosecurity was stressed throughout the day, though unfortunately the outlook seems bleak for our native population, which is continually dwindling with remnant populations becomes increasingly isolated and vulnerable.

It was a useful course and great to get close to these fascinating little creatures, and I'm pleased to have picked up some useful new survey skills.