In the 1970’s the Signal Crayfish were available on the menus in many British restaurants. They aren’t native of the UK and were imported from the US and farmed to meet the demand. For the indigenous white clawed crayfish, this must have come as good news and it’s unlikely they shed any tears or objected to the introduction of their American cousins. Their joy was short lived as some of their crafty American species made a run for it and escaped into the streams and rivers of their host land.
The Signals are identifiable by the blood red colouring on the underside of their claws, they are large, aggressive predators who will even eat their own young. They are impossible to eradicate and, since their emergence in British rivers have declared a ‘Claw War’ on the native white clawed crays.
What our little ‘Whites’ failed to realise, was the threat their colonial colleagues posed to them. Similar in a way the the bigger American Grey Squirrel had on the native red, being bigger and stronger, stealing the reds habitat, the Signals carry a plague to which the native Whites have no protection. Thus, without assistance, and, almost guaranteeing, the complete eradication of the Whites.
The Whites are now down to only 5% of their population prior to the introduction of the Signals and they are now, on the verge of extinction and have being eradicated from most of England. But, in the limestone rich calcium rivers of the Yorkshire dales, there are still some colonies of them displaying true Yorkshire resilience and holding out, but, even there, they are now under threat.
In certain sections of plague free Yorkshire rivers, of which the signals are known to be encroaching, measures are underway to assist the whites whenever possible. The method is quite simple, as, neither form of crayfish can ascend the rivers over the fast flowing waterfalls and rapids, existing whites are simply being hand picked from beneath the shallow river stones where they shelter, placed into protective tubes, then, carried up river to safer waters, prior to being released into higher parts ,where, safe from plague, they can build new colonies. A pregnant white can release 100 eggs at a time, so, hopefully, once they have being transported, their chances of survival and multiplying, are far greater than previously.
Ecologist Paul Bradley has received government permission to take emergency measures to collect and move the whites up river to safer waters, and, hopefully, safeguard a threatened species.