NATURE The plight of our native crayfish

Our freshwater crayfish - not pretty, but precious


Country sights and sounds
John Shelley

Another fox came screaming through the darkness last night. An in-heat vixen calling for a mate, uttering a series of disconcertingly half-human screeches, each one as cold as the stars, as she passed close to the house and across the moor beyond. Even the dog looked discomfited and peered nervously into the night; she knew her duty, but this? Couldn’t she wait until it went away?
We looked for tracks in the morning but found none. The vixen is light on her feet. We tried to get the dog to use her nose to find the path taken. The spicy scent of hare or deer is guaranteed to get the blood pulsing through her veins. Those animals she would follow to the far hills and beyond. But this? She claimed disinterest, or that there had been nothing there at all, until we gave up and went for breakfast.
The makeshift path that follows the hedge line appears to be the dividing line between two mink territories. Every ten metres or so, one or other of the animals has left a small signpost, in the form of little piles of scat, or droppings, to let the animal the other side of the boundary know to come no further. Scientists tell us there is much information contained within these deposits, including the age, sex and health of the individual that left them.
We looked, though not too closely, and prodded with a stick, and found them to be full of fish scales and a few small bones. We would have liked to find evidence that the mink had been feeding on Austropotamobius pallipes, the white-clawed crayfish, the only native Irish freshwater crayfish species.
It seems that Ireland is one of the few European countries where this peculiar little lobster-like creature is not especially endangered or even extinct. In many parts of Britain it has been ousted from its range by the considerably larger and infinitely more aggressive cousin, the Signal crayfish, which was somehow introduced, either accidentally or deliberately. This had at one time been a popular choice for the home aquarist; its habit of rearranging the contents of the fish tank or pond where it was living meant that many were soon regarded to be unwise purchases and were rather foolishly let free into the environment. They have also been farmed for their tasty flesh and many escapes have been made from captivity.
The white-footed crayfish has suffered a similar fate in many parts of mainland Europe, to the point where it is considered as a critically endangered species in danger of worldwide extinction. We know that they used to occur in the stream that runs close to our home (we have seen them there many times in the past) but the absence of shell particles in the mink scat suggests that this might be just one more small location where this sensitive creature can no longer survive.
The possible disappearance of crayfish from our local stream will be due to the continuing decline in water quality, rather than to the introduction of non-native species. There are presently no records of foreign crayfish in this country, though this situation is unlikely to remain.
Yet there is good reason to abstain from introducing any more exotic species. Don’t we already have enough problems with rhododendron, knotweed and Gunnera (giant rhubarb), as well as with the mink that triggered this chain of thought in the first place? It is claimed that in the UK, the signal crayfish has cost a good deal more money in control measures and biological diversity than it ever generated, even in the 1980s, when it was intensively farmed for the restaurant trade.
Haven’t we shared that same experience? Look at the already spiralling cost of controlling the spread of Gunnera on Achill and elsewhere. And haven’t the mink already cost us a fortune since their initial introduction just s few decades ago?
The National Parks and Wildlife Service have produced an excellent fact sheet entitled ‘Protect Irish Crayfish’ that anybody with an interest in the countryside would do well to read.
The variety of wild things to be found in Ireland might not be nearly as great as that found in other lands, but it is specific and worth preserving. Give me the call of the fox on a winter’s night. It is the very breath of this wild and wonderful land.