Invasive Species Alert

Carpet sea-squirt

Didemnum vexillum (Kott, 2002)
Date Issued: January 2007

Why the concern?

  • Can smother commercial mussel lines, impact fish nursery grounds and also mussel beds.
  • Alter marine ecosystem functioning and threaten fishing and aquaculture.
  • Harm natural reefs (important biodiversity sites and fish feeding grounds).
  • First sighting was in 2005 at Malahide, Co. Dublin. Concern of further spread following new records in Strangford Lough, Malahide, Mayo and Galway.

What does it look like?

Looks similar to some native species, but the following characteristics can help with identification:

  • It can grow as thin flexible sheets, or hang down in long rope-like growths.
  • It has a uniform pale orange, cream or off-white colour.
  • The surface has a firm leathery texture (not slimy) and has a veined or marbled appearance.
  • Numerous small pores open on the surface, but close up out of water to produce pale spots.

Where might I see it?

  • It lives in shallow water, often in harbours and marinas, usually growing on hard surfaces (e.g. the
    underside of jetties).

What can I do?

  • Report suspected sightings with a photograph
  • Help prevent unintentional spread to new site by following the aquatic biosecurity Check Clean Dry guidance.