NO-ONE knows exactly how or when it arrived on Scotland's shores, but this alien invader appears to be here to stay.
Since it was first sighted at Loch Ryan in the south-west in 2004, Japanese wireweed, a coastal plant native to the Pacific, has spread steadily north, into the Firth of Clyde and on up the coast, out-competing our native sea grass and altering the m
ake-up of the ecosystem.
Now, Scottish Natural Heritage (SNH) is calling for the public to help track its progress to aid research and in the hope it will raise awareness of the potential dangers posed by alien species in general.
A new arrival - brought to Scotland by international shipping, by deliberate or accidental introduction - can find itself in an ideal environment for growth, unchecked by competitors seeking to exploit the same niche in a habitat.
And with climate change altering the temperature of the sea, Scotland is likely to become a territory available to different invaders than in the past.
Dr David Donnan, SNH's marine ecosystems policy and advice manager, said wireweed, or Sargassum muticum, was comparable to rhododendrons on land in its ability to take over from native plants.
While this may not have a direct economic effect on humans, Dr Donnan warned there were other species that could be heading Scotland's way which have caused millions of pounds of damage.
"Invasive, non-native species are coming here through unnatural sources, like shipping or some other human-related activity. They would never naturally reach the UK and they can take off in a big way. Sargassum has not caused huge commercial problems, but it should be something we use as a wake-up call to say how easily it can get here, how quickly it spreads and, once it is here, how difficult - almost impossible - it is to remove.
"We should do everything we can to avoid other species like that turning up in the UK."
SNH is asking anyone who finds the plant to report it, with an exact location or grid reference if possible.
Fiona Manson, a marine advisory officer at SNH said: "The spread of wireweed in Scotland is a cause for concern. It poses a threat to our native marine wildlife, as well as to boats and fish-farming.
"The species is very difficult to control once it has established and can spread rapidly because broken-off fragments float and remain reproductively active for some weeks.
"We are very keen to find out where wireweed is in Scotland," said Ms Manson. "Knowing where it is now will be the first part of helping us decide how to deal with it."
Dr Liz Cook, a lecturer in marine biology at the Scottish Association for Marine Science, said another alien invader - skeleton shrimps, also from the Pacific - appeared to be found associated with wireweed.
They were first seen in Scottish waters in 1999 and are now known to be all round the coast in large numbers.
"It looks like a preying mantis and it will grow up to four centimetres in length and in an incredibly high density," Dr Cook said.
"If you put them on the same net as our native shrimps, the native ones will just do a runner. The skeleton shrimps attack them and eat them.
"They attack each other, but our guys are a little bit smaller and they lose out."
Dr Cook said there had been reports from mussel farms that lines of rope put in the sea so wild juvenile mussels have a safe place to grow had come up full of skeleton shrimp instead.
This may be due to local conditions and the situation is being investigated, but Dr Cook said: "The shrimps are everywhere and they are there in their masses."
• To report a Japanese wireweed sighting, send an e-mail to
wireweed@snh.gov.uk.
DANGERS TO THE DEEP
• SARGASSUM or Japanese wireweed: Outcompetes native seaweeds and grasses, changing the natural habitat. Can foul boat hulls, propellers and water intakes, and cause problems for shellfish farming.
• Skeleton shrimp: Also from the Pacific. First seen in Scotland in 1999, it is all round the coast and found living on mussel lines used in cultivation.
• Slipper limpets: Currently found in southern England and Wales, could spread by accidental introduction.
• Chinese mitten crabs: At the River Tyne and heading north. Their burrows undermine the banks of rivers and estuaries and they eat salmon eggs.
• Didemnum, a sea squirt, found in Ireland. Creates mucus-like material that can smother shellfish.
