MORE than 100 foreign species are now creeping and crawling their way around Ireland, to the mounting alarm of scientists, after hitching a ride on ships or hiding out in imported plants

MORE than 100 foreign species are now creeping and crawling their way around Ireland, to the mounting alarm of scientists, after hitching a ride on ships or hiding out in imported plants. The latest threat to hit Irish shores is a crab from the Far East that has already caused ecological and economic damage in other countries.

Experts fear the discovery of three Chinese mitten crabs in Waterford estuary is proof of an invasion by a creature Chinese Mitten Crabthat preys on native fish eggs and because of its habit of burrowing will damage river banks. It is not alone in threatening Ireland’s indigenous wildlife. The crustacean joins other exotic species of plants and animals that have established themselves in Ireland including Lagarosiphon major, or curly waterweed, which originates in southern Africa and probably escaped from an ornamental garden pond after being imported. An earthworm native to central Africa, and never before seen in Britain or Ireland, has been found at a hotel in Cork. And settling in nicely is the zebra mussel, which has colonised the Shannon and Erne and laid waste the microscopic food supply, depositing its faeces in the water. We are really concerned about the Chinese mitten crab, said Joe Caffrey, senior scientific officer with the Central Fisheries Board, who describes it as a beastly creature. It was discovered in January and since then we have found another two. Where there are three there may be more and we could be dealing with an infestation. If we are, it’s bad news.

The crab is believed to have arrived in ships’ ballast water, which is pumped into tanks and later discharged. The first crab was found by a fisherman on the Suir estuary in Waterford. The Southern Fisheries Board has since sought co-operation from fishermen to discover if there are more. The burrowing of the mitten crab, so named because its claws resemble fingerless gloves, could destroy Ireland’s river banks by causing them to collapse, said Caffrey. It could also pose a threat to fish stocks, especially salmon. The crab, which can travel across land from one river to another, eats fish eggs. Curly weed, which is sold at garden centres, also causes damage when left to grow wild, according to Caffrey. It is currently affecting parts of Lough Corrib, about 30 acres in all, where it has formed dense infestations that pose serious problems for angling, boating, environmental and tourism interests, he said. Brown trout, for example, could be forced to move away from parts of the lake and this would be a disaster for what is an internationally renowned fishing area. In some parts of the lake, the vegetation is now so dense that ducks are able to walk across its surface. Dan Minchin, a Clare-based expert on non-native creatures, works for Daisie, a European Union-funded project that charts invasive species.

He has found 70 in the Irish marine environment and up to 100 animals and plants in freshwater, many of which have the potential to damage existing habitats. Alien species arrive in several ways. They may be imported as pets, destined for ponds or acquariums from which they escape. People are moving home and they don’t want to take fish with them, so they release them. They may have them in a pond that floods and the fish escape to wild water, said Minchin. We have a large number of invasive plants, too, that are sold for gardens and used in aquariums. It is not just Ireland’s rivers and lakes that are being attacked. Patrons and management at a Cork hotel became alarmed when they noticed bright red worms in the drains of the shower rooms and in cracks in the grouting between floor tiles next to the hotel pool. It turned out to be Dichogaster bolaui, an exotic invader from Africa. This was an extremely interesting case because there aren’t many species that have actually invaded indoor environments, said Olaf Schmidt, a lecturer in the department of environmental resource management at UCD. A possible source for the infestation was potted ornamental plants, believed to be imported, that had been placed in the pool room after it was refurbished. After repeated applications of salt solutions into drains and on to floor tiles, all the worms were killed. Minchin is also concerned about the topmouth gudgeon, the most invasive fish in Britain. It probably came to Europe mixed in with golden orph, a pond or aquarium fish, and is now established in 40 sites in Britain. Richard Oakley and Jan Battles © Sunday Times