Colonial Sea Squirt

(Didemnum spp.)

The Colonial Sea Squirt (Didemnum spp.) is an invasive marine pest that is spongy and orange/yellow in colour. It grows rapidly, smothering aquatic species, such as mussels and oyster populations.

While this exotic species has not been found in South Australia, it is important that we are on alert to protect the biosecurity of our marine habitats. It can spread rapidly by attaching itself to the hulls of vessels. It can also form new colonies from broken up fragments travelling in the current or attached to ropes and other marine equipment.

Watch the video to see what Colonial Sea Squirt looks like

Video courtesy of Ashley Coutts (Aquenal Pty Ltd)

The species is well established in northern Europe, the United States, Japan and other global waters, including New Zealand.

A suspected case of sea squirt in Twofold Bay, NSW has been confirmed to not be the invasive marine pest Didemnum vexillum, but it is a reminder that all users of waterways need to be aware of marine pests and follow the National Biofouling Guidelines to ensure that they are not introduced into Australian waters. This pest has not been confirmed in any areas of Australia. More information (external link).

Fishers, aquaculture operators, vessel operators and divers are asked to adhere to the following reporting and decontamination guidelines.

Any suspected species should not be removed or broken up in the sea because this increases the chance of it spreading.

Reporting

Any possible sightings should be reported by:

  • taking a photo, if possible
  • recording an accurate location, by GPS and landmarks
  • reporting it to FISHWATCH on 1800 065 522.

Decontaminate

  • Inspect your fishing, diving gear and vessel for any possible fragments.
  • Wash any suspected fragments thoroughly with fresh water and make sure the debris does not wash back into the sea or down drains. Dry gear adequately.
  • Check your trailer, boat/vessel, moorings, anchor, chain, ropes and fishing gear for any possible sea squirt fragments.
  • Dispose of any suspect pieces in a rubbish bin.

More information

Colonial Sea Squirt (Didemnum spp.) brochure (.pdf)

The pest is listed as a priority marine pest species on the National System for the Prevention and Management of Marine Pest Incursions. More information is available from the Australian Government.

More information on the situation in NSW is available from the NSW Department of Primary Industries.