Over the 18th-19th September, volunteers from the RGCG, Environment Agency, UCL and the Norfolk Non-native Species Initiative were involved in the third Glaven white-clawed crayfish transfer. As usual all volunteers were by guided by the brilliant Martin Pugh of Essex Wildlife Trust.
Unfortunately non-native American signal crayfish are present in the Glaven catchment and greatly threaten the river’s native white-clawed ones. The signal crayfish is a very aggressive species and it tends to out-compete native crayfish for habitat and food. But even more nasty is a fungal disease (crayfish plague), often carried by signal crayfish, which wipes out white-clawed populations very quickly.
Currently, the Glaven probably holds the biggest remaining river population of white-clawed crayfish in southern England. But we cant afford to be complacent! Although the trapping programme of Robin Combe (RGCG chairman) seems to be keeping signals out of the main river (see his blog post of June 2012), the future of the Glaven’s white-clawed crayfish is a little bit precarious. Thus we are now in year three of a programme which aims to create local “safe houses” for Glaven white-clawed crayfish. And just as a quick update, on 15/9/2013, Robin announced that he had caught 19297 signals from the pond on Watering Lane (a tributary of the Glaven). There is no stopping him!
Last year we transferred 100s of white-clawed crayfish to the Glaven’s sister river, the mighty River Stiffkey, in addition to a small Glaven tributary (see blog post for September 2012). This year, however, the chosen recipient site was a clean, clear-water pond on an undisclosed country estate in the Glaven catchment.
Around 150 white-clawed crayfish were transferred to the pond, all of which were measured and checked for any signs of ill health before clearance for travel. We wish them well!
And good news! On the 19th September Martin and a few other hardcore crayfishers checked on the River Stiffkey release sites. At both places juvenile white-clawed crayfish were found – a sure sign of success and crayfish happiness!
A thought came to mind as were doing the catching on the Glaven. If we keep it all going (the crayfish day is becoming an annual event) we could make the white-clawed crayfish more widespread in North Norfolk than when we started. But long may the signals keep out of the main Glaven.
Thanks to Anne Casey of the Norfolk Biodiversity Partnership for all photos.
Carl Sayer, September, 2013