Fears the white-clawed crayfish, our only native crayfish species, may become victim to a lethal disease introducedfrom abroad have now come to pass. Outbreaks of crayfish plague, a disease that kills white-clawed crayfish, have been reported in the rivers Deel, Co Limerick, and Suir, Co Tipperary.
Attempts are being made to prevent its spread and a temporary ban has been placed on moving water sports and angling gear, such as boats, waders and nets, out of the affected rivers. Equipment currently in use in the catchments may continue to be used there, but should not be moved out.
Ireland holds the largest population of white-clawed crayfish, which look like small, brownish lobsters, in Europe. Inland Fisheries Ireland had warned the species, which is widespread, was at high risk that someone may accidentally, or even deliberately, introduce a another species that would bring in the deadly plague.
There are about 650 different crayfish species worldwide, but only six in Europe and one in Ireland. European crayfish are, or were, widely caught for food, but all are now threatened, chiefly by the plague carried by crayfish introduced from North America. There are now ten species of American crayfish across Europe, many which are in the wild in the UK. Each American species carries a different strain of plague, to which European stocks have no resistance and can be eradicated in weeks. The fungus produces spores which can be transferred on wet nets and boots, on boats, and even on fish for restocking.
Ireland is the last European country with no alien crayfish in the wild. However, keeping fish and other aquatic animals as pets, or in aquariums, carries a risk of these creatures getting into natural habitats.
A study in Biology and Environment magazine, says four, non-native crayfish species available through the pet trade here pose significant risk if introduced into the wild. Author Zen Faulkes, of the University of Texas, says we are lucky the inward movement of unwanted species is limited because we are separated by sea from Britain and other parts of Europe. But, he warns, barriers can be got around through human-assisted transportation. In 2015, 28 advertisements were recorded here offering more than 100 crayfish for sale by 19 individuals. Faulkes says the illegality of importing foreign crayfish barely affects the trade, and he calls for enforcement of laws to reduce their importation.