MAF Biosecurity New Zealand and iwi join forces to clear marine pest

9 August 2010

MAFBNZ Senior Marine Adviser Katherine Walls says the sea squirt Pyura praeputialis (known simply as Pyura) has been an aggressive invader of rocky shorelines where it has established outside of its native Australian habitat.

It was first detected at the remote Twilight Beach near Cape Maria van Diemen and MAFBNZ surveys have since found Pyura at a number of sites around the Far North coastline.

Because of the species' ability to smother and displace native green shell mussels (surveys have already shown it growing over mussels in some Northland locations), the decision was made to test the effectiveness of removal techniques.

"Also taken into consideration was the presence of this introduced species in areas of high value to Maori," says Ms Walls.

"MAFBNZ has already determined that fully eradicating this well established sea squirt is not feasible. There is, however, such a high level of interest in the local community that we consider there's merit in trying to remove the species from some sites where population numbers are relatively low.  This pilot treatment at a couple of sites will tell us whether it's worthwhile attempting to manage Pyura at other places where numbers are low."

The four day programme begins today with a workshop covering treatment measures and Pyura biology. Local iwi, Northland Regional Council and the Department of Conservation have been invited to attend.

From tomorrow four local people, working with a marine scientist who has been engaged by MAFBNZ, will spend three days clearing all visible Pyura from two locations - the Bluff at 90 Mile Beach and Whareana Bay.  At the same time, a scientific control trial will also be carried out on a population at the entrance to Parengarenga Harbour, where one marked area will be treated and one left alone to compare results.

The field teams will be careful to completely remove all Pyura, bag specimens and dispose of them well away from the sea to avoid any re-infestation.

The programme will be repeated in six months and its effectiveness evaluated. Ultimately it will be up to communities involved to determine if they wish to continue with management of this sea squirt after the trial.

"This teamwork is an exciting development which supports MAFBNZ's goal of enabling communities to lead long-term management of pest incursions, raising local awareness of biosecurity issues and preparing communities ahead of any future marine biosecurity events, Ms Walls says.

For photos and more information contact:
Lesley Patston, Senior Communications Adviser, 029 8940163 or

Full information on Pyura is at:

To report an exotic pest or disease call the MAF Biosecurity hotline on 0800 80 99 66



Last Updated: 22 September 2010

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