Invasive sea squirt species confirmed in Strangford Lough

by RYA 
Sea squirt (Didemnum vexillum)
The Northern Ireland Environment Agency (NIEA) has confirmed that a colonial sea squirt discovered in a recent survey of marinas and harbours is the invasive non-native species Didemnum vexillum commonly known as ‘carpet sea squirt’.

The identification was confirmed when larvae from the samples were examined by microscope at the NI Environment Agency laboratories in Lisburn to confirm the species. Following confirmation NI Environment Minister Alex Attwood said: 'I am extremely concerned that carpet sea squirt is now confirmed to be in Strangford Lough given its potential to affect the lough’s marine life and some of the economic activities it supports such as aquaculture.

'Fortunately these impacts have not been experienced to date at other locations where it has been found in Britain and Ireland, however it is essential to take a precautionary approach. I have therefore asked my officials to rapidly draw up a management plan in consultation with stakeholders and Lough users.'

Dr. Holt, Marine Biologist, Countryside Council for Wales, who has been leading a project over the last three years to remove the same species from Holyhead Marina in North Wales, said: 'It is crucial to take quick and decisive action to remove the species and minimise the risk of spread or reintroduction.

'Early investment can avoid much greater costs should the species become well established.'

The common name of carpet sea squirt well describes the potential problems it poses. It hangs from hard surfaces such as docks, lines and ship hulls or forms mats on seabeds and can grow rapidly to smother marine life such as sea weeds and marine fauna including mussels and oysters.

It is mainly transported over longer distances on boat hulls but larvae and fragments can also be spread by fishing equipment, the movement of aquaculture nets and tidal currents.

NIEA is encouraging all coastal water users, especially in the Strangford Lough area, not to attempt to remove suspected sea squirt from vessels or sea structures, to report possible sightings, with photographic evidence, through the ‘alien watch’ facility of the Invasive Species Ireland website.

What can you do?

You can help to prevent the spread of carpet sea squirt.

• Inspect and clean your boat and kit before and after use.
• Do not move fouled equipment from one area to another.
• Drain all the water from your boat before you leave a sailing site.
• Inspect and clean your trailer before and after use.
• For boat kept in the water permanently, hull fouling is the main means of transfer.
• Clean your hull regularly to minimise the risk.
• Try not to run through water plants and weed.

More advice and information on what you can do to help prevent the spread of non-native species.

RYA website
http://www.sail-world.com/103024