ANOTHER LIFE: Lurking under stones in Irish limestone lakes and streams, or backed into shadowy holes beneath the banks, is one of the island's least-known water creatures, Austropotamobius pallipes, otherwise known as the white-clawed crayfish, writes Michael Viney.
This little greeny-browny freshwater lobster grows no longer than 15 centimetres, but glimpsed on its hunt for snails or tadpoles, its magnification in the water can make it look quite fearsome. Caught in the hand, however, it rarely uses its pincers aggressively (or so I am told).
Austropotamobius is a scientific name best taken at a gallop. There is no distinctive common name in Irish; nor does the animal seem to figure in our folklore. This gap in national awareness suggests an alien origin, a fact now confirmed in genetic studies by Dr Julian Reynolds of TCD and colleagues in Poitiers in western France. Our native freshwater crayfish is thought to be an introduction from that region, perhaps brought in by French monastic orders.
It has flourished in the smaller limestone lakes of the midlands, in rivers such as the Barrow, Nore and Suir, and even in Blessington Reservoir, where numbers reach more than 500 adults on 100 square metres of rocky bottom. In all these waters, calcium builds the animal's body-armour and allows twice-yearly moultings in the course of a long and leisurely growth.
Like the ocean lobster, Austropotamobius turns bright red in boiling water. It is actually a somewhat smaller version of the red-clawed freshwater écrevisse of French restaurant menus.
My wife, ordering écrevisse Provençale for the first time and receiving a dish of unshelled crustaceans smothered in thick red sauce, rolled up her sleeves, called for finger bowls and napkins and set about a brave dismemberment, while her French fellow diners turned in their chairs to watch.
However the species was introduced to Ireland, our white-clawed crayfish are now the strongest population left in Europe. Elsewhere, from Croatia to Iberia, all crayfish have been greatly reduced by pollution and loss of habitat, and the white-clawed species was particularly hit by a plague fungus carried by American signal crayfish, brought to Britain and Europe for crayfish farming. Ireland was the last country to be hit by the plague, brought in by foreign fishermen with infected keepnets in the 1980s.
Five midland lakes lost their crayfish populations before the plague burned itself out. In the UK, meanwhile, where the white-clawed crayfish is actively endangered, government scientists are trying poison, predator fish, and even draining lakes and streams in efforts to eradicate the marauding American crayfish.
Since Austropotamobius pallipes seems not to have reached Ireland naturally in post-glacial colonisation, would it really matter if we lost it now? It captures and eats almost any kind of smaller water creature, helps to control water plants, and can even, reputedly, leave the water during warm summer nights to graze on the bankside vegetation (to reach the upper Liffey, it may actually have climbed a waterfall). In turn, it provides an often important food for trout and eels, otter and mink.
Thus, like other aquatic species introduced to Ireland, it holds a distinctive place in our freshwater ecosystems. In its control of plant growth in the clear waters of lime-rich lakes, it actually became an ecological keystone species. Its survival here in such healthy numbers while dwindling elsewhere in Europe makes it a "heritage" invertebrate, worthy of its protection under the EU Habitats Directive and Ireland's Wildlife Act.
For the 50 international crayfish scientists who have gathered in Kilkenny this weekend, mostly from Italy, France and Spain, Ireland offers the ideal situation in which to study Austropotamobius and its habitat needs. Their conference, organised by Dr Julian Reynolds, focuses on it both as a species important to biodiversity and as a possible "bioindicator" of water quality.
French scientists are particularly keen on the crayfish as a conservation flagship species and guardian of pristine rivers and lakes: pollution has hit their populations badly in the past decade. Reynolds and some of his British colleagues, on the other hand, believe that Austropotamobius will live in moderately polluted water. The argument will run, but for either side there is virtue in a conservation policy that allows the crayfish to be caught for food on a carefully licensed and sustainable basis.
Made notable on gourmet menus, wild Irish crayfish would register in public awareness and add an extra economic value to protection of water quality. Large-scale reintroductions to plague-swept lakes are perfectly feasible. Crayfish farming, on the other hand, especially with bigger introduced species from Europe or the US, would bring inevitable risks along with the profits.