Tiny invader that has wreaked havoc in US set to mussel in on Scotland

Published on Friday 28 November 2008 21:16

INVASIVE Russian molluscs that have cost the American economy more than $3 billion (£2 billion) are heading towards Scotland, experts have warned, with little that can be done to stop them getting in.

The stripy zebra mussels are wreaking havoc in the United States and Ireland, clogging up power stations and water treatment plants and devouring crucial nutrients in lakes and rivers.

Now the tiny creatures, which can produce up to a million eggs a year, are on their way to Scotland, according to experts.

The fresh-water molluscs are the size of a fingernail and cling to any hard surface, and can be spread on boating or fishing gear, or even on the sole of a shoe. In the Republic of Ireland, they have spread to at least 50 loughs and it is estimated 300 more are at risk of invasion.

In the US, they have spread out of control since arriving in the mid-1980s, infiltrating lakes and rivers in most states and costing billions of dollars to clean up.

In some states the problem is taken so seriously that fines are handed out to people if zebra mussels are found on their gear.

Joe Starinchak, an invasive species expert with the US Fish and Wildlife Service, told The Scotsman he thinks that it is highly likely they will end up in Scotland.

"You have got people coming from America and people coming from Ireland," he said.

"We live in a globalised economy. We are moving goods and services around at a rate this world has never seen. With that goes invasive species. I think you have got to do everything you can to stop them."

He said that the mussels are so small, they could even be spread on the sole of a shoe. "You may be inadvertently carrying these things and you may not even know it. When they are in immature form, they are very small." He said that the scale of the problem was first realised when air-conditioning went off during a scorching summer in America.

"The original catalyst to address them was when they shut down power plants, which in turn switched off people's air-conditioning in the very hot and humid summers of the Midwest," said Mr Starinchak. "That's when it really started to resonate with people."

As well as clogging up equipment, the mussels feed by filtering water, which removes the particles and algae that are the basis of the food chain.

Without algae the water is very clear, meaning sunlight gets through and encourages weed growth, clogging up riverbanks and waterways. The mussels also filter vital zoo-plankton out of the water, damaging fish numbers, with a knock-on impact on recreational fishing and tourism. And in Lough Erne in Ireland, where the mussels are prolific, competition from the invasive species has put native swan and duck mussels under threat of extinction.

Robin Payne, the invasive non-native species co-ordinator at Scottish Natural Heritage, said: "People should take the threat of zebra mussels very, very seriously. As with a number of invasive species, they are already close to our borders and could have really significant effects on our ecosystem and wildlife."

He thinks people need to be made more aware of their potential to spread the mollusc, and the need to wash fishing or boating gear. However, Mr Payne said most important was that countries already host to the pest make sure it does not leave.

"With a species such as this one, trying to stop it at the gates is the wrong strategy," he said. "It must be about stopping it leaving where it is, so we need to support the initiatives in Ireland and work with them."

Invasive species are considered the largest threat to biodiversity after climate change and habitat destruction.

Scotland is already plagued with alien invasive creatures. These include the grey squirrel, which has put the native red at risk since arriving from America, and Japanese hogweed, which clogs up buildings and train tracks.