In March 2018, Storm Emma caused significant damage to Holyhead Marina in North Wales. Clean-up operations followed and are ongoing.

As part of clean-up operations, actions are being taken to reduce any potential environmental impacts that may occur as a result of this incident.

We are advising interested parties as, despite efforts to contain debris from the damaged marina, some debris has drifted out of the harbour area into the wider marine environment.

A consequence of this incident means there is potential for carpet sea-squirt Didemnum vexillum (D. vex), a marine invasive non-native species known to inhabit the area, to spread to other areas. However, the risk of spread may be reduced due to the current sea temperature, which at this time of year is not thought to be favourable for D. vex to reproduce.

Prior to Storm Emma, D. vex was being contained in the marina after being discovered living on the submerged artificial structures, commonly found on the floating pontoons, ropes and chains. The resin surface of the floating pontoons provided a suitable area for D. vex to live.

D. vex (a factsheet is available online) is considered to be an invasive species because it has the potential to negatively impact fisheries, aquaculture and the conservation of native marine habitats.

Areas of potential spread

Evidence suggests that debris has the potential to spread quite far from Holyhead. Remains of a floating pontoon with resin coating has been recorded approx. 37km away from the marina.

There have also been reports of polystyrene (believed to be from Holyhead pontoons) washing up in Wicklow in Ireland. There have been no further reports of debris at other locations at this time. 

(Right: Photo credit: Ashley Williams)

What to do if you see any potential debris.

All sightings of possible debris should be reported to the Scottish Environment and Rural Services (SEARS) telephone number 08452 30 20 50 or

Where it is possible and safe to do so we suggest any debris found is moved above the high tide line to prevent it from returning to the sea. It would also be helpful to record the date, time and location of any findings, and if possible map or GPS coordinates. Photographs or descriptions of the debris and any organisms growing on it would also be helpful.

Specimens in the fouling community appeared similar to D. vex but had dried out too much to confidently identify.

This information has been provided by the Welsh Government and Natural Resources Wales. Marine Scotland is working in partnership with other UK Governments and agencies via Marine Pathways.

For further information on reducing the spread of non-native species please find out more from the The Green Blue on our website.