White colonial sea squirt


Have you seen white colonial sea squirt? There have been confirmed detections in Queensland.

Be on the lookout for white colonial sea squirt, and if you see it in areas outside of those where it is already known to be present, report it to Biosecurity Queensland on 13 25 23.

Understanding the spread and extent of this pest will help protect Queensland's high value natural marine assets and industries.

  • There have been confirmed detections of white colonial sea squirt in the Gulf of Carpentaria, Townsville, Airlie Beach, Abbot Point, Mackay and Brisbane.
  • It is not considered feasible to eradicate due to the pest's high reproductive capacity and inability to effectively treat established populations or control its further spread.
  • White colonial sea squirt is a colonial ascidian and can overgrow native species.
  • It is introduced via fouling on ship hulls and possibly in ballast water and internal seawater systems.
  • It is illegal to import, keep, breed or sell white colonial sea squirt as it's a prohibited marine pest.
  • White colonial sea squirt is predominately found growing on submerged and floating man-made structures such as buoys, moorings, pontoons, pylons and boats. It can also be found on hard natural substrates.
  • Biosecurity Queensland will continue to monitor the extent and spread of this species working closely with port authorities and maritime industries.

Scientific name

Didemnum perlucidum


  • White colouring.
  • Grows in an encrusting manner across artificial structures such as buoys and pontoons.
  • Can grow over the top of other organisms.


  • Subtropical to tropical.
  • Estuarine to marine.
  • Is known to survive water temperatures between 15–30oC.
  • Commonly found in depths approximately 1–3 metres.
  • Can be found at depths of up to 8 metres.
  • Attaches to hard surfaces (e.g. hulls, buoys and pylons, rocks) but can also grow on sea grass beds.


  • Known distribution in Queensland:
    • Gulf of Carpentaria (south of Weipa)
    • Townsville
    • Abbot Point
    • Airlie Beach
    • Mackay
    • Brisbane
  • The white colonial sea squirt was first described in the Caribbean then subsequently found in Brazil, West Africa, the Gulf of Mexico and some areas of the Indo-Pacific (including Hawaii, Guam, the Panama Canal), and Australia (including Western Australia and Northern Territory where it is widely established at ports and marinas across many locations. Also known to be present in New South Wales).

Life cycle

White colonial sea squirt becomes sexually mature within a few weeks of larval settlement and is highly prolific. It can reproduce sexually and asexually throughout the year, releasing large numbers of larvae daily. It is most abundant during summer months, with colony sizes decreasing in the colder months.

Affected animals

  • Sedentary animals
  • Native aquatic plants



  • Potential to be highly invasive due to its rapid reproductive output.
  • Fast growing and can occupy disturbed habitats.
  • Can overgrow native species.


  • Fouling of wharf pylons, buoys, pontoons, marinas, vessel water intake systems and marine aquaculture farms.
  • Threatens marine industries, including ports, marinas, commercial fisheries, tourism and aquaculture.


  • Can create an eyesore and affect our way of life.
  • Can lead to boating and fishing restrictions in affected areas.


Look. Report. Protect. Marine biosecurity—everyone plays a part.

If you think you have seen white colonial sea squirt outside of known distribution areas, report it to Biosecurity Queensland on 13 25 23.

You should also:

  • clean your boat regularly
  • check for marine pests on structures and surrounds
  • report any suspected marine pests.

Slipway operators, vessels inspectors and vessel owners should regularly and thoroughly check and clean vessel hulls looking out for pests or growth, paying particular attention to the nooks and crannies of your vessel including internal seawater systems.

Inspect, clean and dry equipment and gear before moving to a different location. This includes pots, nets, fishing or diving gear, anchors and ropes.

Biosecurity Queensland will continue to monitor the extent and spread of this species working closely with port authorities and maritime industries.

Legal requirements

  • White colonial sea squirt is a prohibited marine animal under the Biosecurity Act 2014.
  • Any sighting of white colonial sea squirt must be reported to Biosecurity Queensland on 13 25 23 preferably within 24 hours.
  • Biosecurity is a shared responsibility and by law everyone has a general biosecurity obligation to take all reasonable and practical steps to avoid causing a biosecurity event, and to avoid any behaviour that may impact on a biosecurity event caused by attempting to deal with biosecurity matter.

Further information