Advanced Search | Help
6 October 2005
Biosecurity New Zealand is investigating a confirmed find of the exotic
marine pest the 'clubbed tunicate' (sea squirt), Styela clava in two New Zealand
The clubbed tunicate has been found in Auckland at the Viaduct Harbour and in
Lyttelton Harbour in Christchurch. The Auckland find was made recently by a
visiting UK marine scientist and the Lyttelton specimen was located as a part of
routine baseline port surveys undertaken by Biosecurity New Zealand.
The clubbed tunicate is a tough, leathery club-shaped organism that grows up
to 160 mm long. It is a prolific breeder, spawning every 24 hours or so from
maturity. The tunicate tends to settle in protected areas such as bays and
harbours, out of wave action. It is frequently found on wharves, aquaculture
structures and equipment, boat hulls, mooring lines and other man made
The clubbed tunicate originated in Korea, but is now spread throughout much
of the world, including parts of Australia. It can travel on the hulls of boats
(hull-fouling) or in bilge water. Hull-fouling is the most likely source of its
arrival into New Zealand.
Biosecurity New Zealand's Senior Marine Adviser, Brendan Gould, says there
are potentially significant impacts if the clubbed tunicate becomes established
in New Zealand waters – particularly for the aquaculture industry.
"Clubbed tunicates can settle on lines and grow over shellfish cultures,
including mussels and oysters. They compete for food and space and also predate
on shellfish larvae."
Mr Gould says Biosecurity New Zealand's initial response is to survey the
Viaduct Harbour and nearby Freemans Bay to determine just how widespread the
"We're moving quickly to set up this delimiting survey and we should know the
extent of the problem within a month."
If necessary, the survey will extend to the whole Waitemata Harbour. A survey
of the Lyttelton incursion will also be carried out.
Brendan Gould says work is also underway to have the clubbed tunicate
declared an unwanted organism, which will allow Biosecurity New Zealand to
implement control measures under the Biosecurity Act.
Potential treatment options will be investigated once it's established how
just how widespread the pest is. Overseas experience, however, has demonstrated
clubbed tunicate is difficult to manage.
Biosecurity New Zealand will be asking the aquaculture industry, boaties and
wharf users for help identifying any further clubbed tunicate. Awareness
material with photographs and information about the pest is being prepared and
will be circulated to those most likely to come across the clubbed tunicate.
For further information, please contact: Lesley Patston, Senior
Communications Adviser, Ph: 04 474-4246 or 027 2051418 or Phil Barclay, Senior
Communications Adviser, Ph: 04 4702753 or 027 2299145
Note: a photo of the clubbed tunicate is attached. Photo supplied courtesy of
Kevin Heasman of the Cawthron Institute. The photo is of the clubbed tunicate in