Sea Squirt (Clubbed Tunicate)

Sea Squirt (Clubbed Tunicate)

Styela clava

This pest is established in certain locations in New Zealand. It is an unwanted organism.

If you suspect you have found this in New Zealand in a location other than Hauraki Gulf, Tutukaka & Marsden Cove Marinas or Lyttelton, call 0800 99 66.

Description

  • Styela clava is a club shaped sea squirt (marine animal).
  • Individuals appear as a tough, leathery skinned cylindrical form, tapering to a stalk with a holdfast that anchors them to surfaces.
  • The sea squirt is usually brown in colour, and underwater often appears fuzzy with secondary growth coating it.
  • Styela clava individuals can grow up to 16cm long.
  • Underwater two short siphons or openings are visible at the top of the organism.

This sea squirt prefers to settle on hard surfaces, particularly man-made structures. It is most commonly observed on jetty and wharf pilings, on aquaculture structures and equipment, on ropes and lines, and on the hulls of infested vessels.

They may also be found attached to rocks, seaweed and on shellfish.

Styela clava can be mistaken for a native New Zealand species, Pyura pachydermatina, as they both have a stalk.

Pyura pachydermatina - a New Zealand native
Pyura Pachydermatina - a
New Zealand native

However, the stalk of Pyura pachydermatina is much longer – 2/3 to 3/4 the overall length of the organism. It is also white/purple in colour.

Impact

The Styela clava sea squirt poses potential threats to New Zealand’s aquaculture industry and biodiversity.

Spread

Styela clava is now known to be widely spread throughout the Hauraki Gulf. It has also been confirmed to be widespread but in low densities in Lyttelton Harbour (Port of Lyttelton and Magazine Bay Marina), and in the Tutukaka and Marsden Cove marinas in Northland.

There have also been detections of this organism on individual vessels in Picton, Nelson, and Opua. In all these instances, individual specimens have been removed from the vessels in question and extensive searches of the areas where the vessels were moored have failed to detect any further specimens.

Styela clava, as with other fouling organisms, can be spread on the hull of vessels. It is able to settle and grow on existing hull fouling material and thus be transported to new locations.

To prevent the spread of Styela clava, it is important vessel owners ensure their hulls are regularly cleaned and anti-fouled.

Locations of confirmed Clubbed tunicate finds:

Management

While eradicating this organism has been deemed unfeasible, Biosecurity New Zealand is continuing with research that may ultimately assist in its management, as well as running extensive communication programmes to help slow the spread of it from infected to non-infected areas.

One of the current research projects underway as part of the Styela clava response is a study of the reproductive biology of the creature. This research project will potentially provide information to underpin any future management actions.

Two scientific research agencies have been contracted to undertake population management trials at the two outlying sites of Styela infestation (outside of the wider Hauraki Gulf) - Lyttelton and Tutukaka.

These trials will determine if it’s feasible to control the organism sufficiently in those two locations to prevent its spread from there.

Public education campaigns targeting boaties and other marine users and encouraging them to keep their vessels and equipment clean and anti-fouled are currently underway.

Click images to view the advertisements in PDF format.

Information on viewing PDF files

Fact Sheet

Media Releases

General Documents

Useful Resources

Contact Us

Customer Services Officer

MAF Biosecurity New Zealand
PO Box 2526
Wellington
NEW ZEALAND

Phone: +64 4 894 0560
Fax: +64 4 894 0720

Email Lists

By joining our e-mail lists you will receive notifications of changes to standards, discussion documents etc.

Subscribe to our lists RSS