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Plea for boaties to prevent spread of marine pests

Wednesday, 20 November 2013 12:22 p.m.

A boat infested with the unwanted marine pest Styela clava, also known as clubbed tunicate sea squirt, has been found berthed in Tauranga Harbour.

Bay of Plenty Regional Council Natural Resource Operations Manager Warwick Murray said that it’s the second boat with Styela clava on its hull that has been found in Tauranga Harbour in the last month.

“The first boat was moored in Pilot Bay and this latest one was berthed at Bridge Marina.  Both boats have been recently brought here from Auckland, without prior cleaning of their hulls.”

“Both boat owners have been very concerned and co-operative but we need boaties to be much more vigilant if we are to keep Tauranga Harbour free from marine pests that have become established elsewhere,” said Mr Murray.

Mr Murray said that recreational boats are not the only way that marine pests are spread, but they are high risk.

“Pests like the clubbed tunicate and Mediterranean fanworm are more likely to attach themselves to the hull of a boat that’s left moored for long periods of time. It’s absolutely critical that boaties keep their boat hulls clean, anti-fouling paint fresh and take extra care to remove fouling growth from their vessel responsibly, before travelling from one area to another,” he said.

The infested boat hulls were discovered during a dive survey in the southern end of Tauranga Harbour.  Divers from Bay of Plenty Regional Council and Waikato University have completed the survey over the last month, following the detection of a single specimen of another unwanted marine pest - Mediterranean fanworm (Sabella spallanzanii) in Pilot Bay in late September.

Survey divers completed inspections of 340 boat hulls, 4061 metres of marina pontoons, 907 wharf piles and 97 moorings as well as large areas of sea-bed, shoreline and rocky reef around Pilot Bay.

Numerous clubbed tunicate sea squirts (Styela clava) were found during the survey, but only on the two boat hulls.

During the survey, divers also found two individual Mediterranean fanworms; one was located on the boat moored at Pilot Bay and the other on a pontoon at Bridge Marina. 

“Both of the infested boat hulls have been cleaned at a haul-out facility where the fouling was safely captured and contained. We’re hopeful that we’ve been able to find and remove the marine pests before they’ve had a chance to spread into the harbour.  We’re now working with the Ministry for Primary Industries to determine the best approach for detecting and preventing any further spread of both Mediterranean fanworm and clubbed tunicate sea squirts,” said Mr Murray.

Both the Mediterranean fanworm and clubbed tunicate are classified as unwanted organisms under the Biosecurity Act.  Both have become established in other parts of New Zealand, including in Auckland’s Waitemata Harbour and in Lyttelton Harbour.

“If they became established in Tauranga Harbour, both of these marine pests could have a negative impact on our kaimoana including mussels, oysters and scallops. They can interfere with boating, aquaculture and recreational pursuits,” Mr Murray said.

A boat owners guide to preventing the spread of marine pests is available at

Ministry for Primary Industries (MPI) and the Regional Council are encouraging boaties to report any unusual sea life by calling the MPI Exotic Pest and Disease Hotline, phone 0800 80 99 66. Reports should include location details, a clear description and a photo if possible.  Also where possible, a specimen should be collected and chilled so as to assist with species identification.

Marine pest identification guides are available online at


Visit for more information about the Mediterranean fanworm or clubbed tunicate sea squirt.

For further media information please contact Katrina Knill, Communications Advisor, on 0800 884 880.


Click on image below for high resolution version (5.84MB, JPG)

Styela clava on boat hull

Photo caption: Unwanted pest  - clubbed tunicate sea squirt (Styela clava) on hull of boat hauled out from Tauranga Harbour for cleaning.

Click on image below for high resolution version (9.44MB, JPG)

Close up styela clava on Tauranga boat hull

Photo caption: Close up of unwanted pest - clubbed tunicate sea squirt (Styela clava) on hull of boat hauled out from Tauranga Harbour for cleaning.


Styela clava on boat hull