Carpet sea squirt

What is it?
A colonial sea squirt from the genus Didemnum (pronounced Die-DEM-num). Some species have become invasive worldwide, ranging fromintertidal to continental shelf. In Ireland thecolonies have been found fouling boats and marina structures. The scientific name for this species is Didemnum vexillum.
What does it look like?
There are a number of native Didemnum species. The invasive carpet sea squirt tends to form long, ropey or resembling candle wax dripping hanging from hard surfaces such as docks, aquaculture facilities and ship hulls, or found as extensive mats covering rocky sea beds (pebbles, cobbles, boulders and rock outcrops).
An ID sheet can be downloaded – Didemnid Sea Squirts
This species is known to:
  • Smother commercial mussel lines;
  • Alter marine ecosystem functioning and threaten fishing and aquaculture;
  • Impact fish nursery grounds;
  • Overgrow and smoother natural shellfish sites;
  • Harm natural reefs (important biodiversity sites and fish feeding grounds).
What can I do?
  1. Report all sightings – in Ireland to and if located in Northern Ireland –
  2. Follow the Check, Clean Dry Guidelines to help prevent spread.
  3. Take care not to break off pieces underwater or spread it around this will encourage new colonies to grow.

Invasive Species Ireland produced a D.vex Management Plan

Carpet sea squirt in the news:

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