A conference next week will discuss ways of keeping out marine species that threaten local eco-systems, reports Dick Ahlstrom
It's not quite the invasion of the body snatchers of movie fame, but it is an invasion nonetheless. Each year new species of fish, crustaceans and seaweeds invade our shores, sometimes to the detriment of existing species.
The infamous zebra mussel is an example of a nuisance species familiar to most. It arrived here on the hull of a boat and has since spread itself into 55 named waterways, from the Shannon and Erne waterways to the Co Clare lakes and lakes in the midlands.
An international conference next week, organised by the Institute of Technology, Sligo, will hear about international efforts to control the spread of damaging marine species. The 13th annual International Conference on Aquatic Invasive Species, to be held in Ennis, Co Clare, has attracted more than 300 delegates from 32 countries including New Zealand, Russia, China and the US, according to Frances Lucy, who chairs the conference's technical programme committee.
"The conference is about the science of invasive species, methods of control and methods for disseminating information on the species and preventing their spread," she explains.
Not all newcomer species are a problem, she says. It may be unclear until an invasion has begun, however, whether a species will become an issue.
"A number of species have caused major problems by affecting local ecosystems and even man," says Lucy.
Some invaders are hardly visible but can still represent a threat. An example is a planktonic species, Gyronodinium catenatum, which produces toxins that cause paralytic shellfish poisoning. Another is a fish louse, Gyrodactylus salaris, which currently exists in Scandinavia but is feared by Irish fish farmers.
"If that came in it could reduce salmon stocks," says Lucy.
The conference is about identifying new risks and finding ways to prevent the spread of harmful species. It is also about the sharing of research.
"There is very little control over the spread of these species," says Lucy. Yet an invading species could threaten jobs and coastal economies dependent on those jobs.
Water discharged from the ballast tanks of ships is one of the most important vectors for the spread of invasive marine species, explains Lucy. "When they are near a port where they are going to take on cargo they discharge ballast water and this can carry eggs and adults. If they arrive, and like the habitat, they will spread. Ships can also be vectors for things travelling on hulls, like the zebra mussel."
Dr Dan Minchin, of Marine Organism Investigations and a member of the conference's technical committee, describes how a hull can support a surprising variety of species. Large barnacle shells can harbour small crabs, fish eggs, tube worms and more.
He has investigated the species that reached the Liffey River on the hulls of visiting tall ships. He has also investigated "ecosystem engineer" species, such as the zebra mussel and imported oysters.
These leave behind large volumes of material that in turn provides a home and environment suited to yet other invaders.
"The oyster has a long history of introductions," he says.
Some species aren't here yet but are feared for the damage that they can do, such as the Chinese mitten crab.
"They are predators and they burrow into the sides of riverbanks," thus weakening the bank and causing it to collapse, says Lucy. The crab has reached the south of England and its arrival here may only be a matter of time.
"It is not realistic to keep everything out, but it is to be able to manage it - for example, to have a 'wanted list' of species," says Lucy. "Education is a big issue. Once they come in, it is very hard to close the door."
Another prime example of a problem species is Sargassum muticum, an Indian and Pacific Ocean seaweed that cast up on our shores, most likely in ballast water.
"It is taking over the native species" right around the coast, Lucy says. "Seaweeds are deadly because you only need a few fragments for it to take off."
Lucy specialises in fresh-water invaders such as Gammarus tigrinus, a rapidly spreading fresh-water shrimp species.
"We have also found a new invasive shrimp-like creature in Lough Kee," she adds, though this creature is not causing any problems so far.
Invasive species do not recognise borders, so officials North and South are joining together to formulate a response, Lucy adds. The National Parks and Wildlife Service and the Northern Ireland Environmental Heritage Service together have prepared a policy document on the problem known as The Quercus Report. It has been submitted for consideration by officials on both sides of the Border.