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21 March 2006
Biosecurity New Zealand is moving into a longer-term phase of its response
to the invasive sea squirt, Styela clava.
The unwanted organism was first detected in New Zealand in August last year
and subsequent surveillance of high risk locations around the country revealed
its widespread presence in Auckland's Hauraki Gulf and smaller
populations in Lyttelton Harbour and Tutukaka in Northland.
Senior Marine Adviser Brendan Gould says Biosecurity New Zealand has taken
advice from some of the world's leading marine biosecurity and ascidian
experts (the biological class the sea squirt belongs to) and the best
scientific information available says it is not feasible, with today's
available technologies, to eradicate it from New Zealand waters.
"The sea squirt is in such numbers in the Hauraki Gulf that you would
never be able to accurately say you'd found the last one," Brendan
Gould explains. "You could have vast teams of divers working
perpetually removing Styela clava from marine structures and
you'd never complete the task. Eradication on a national scale is
simply not feasible."
Mr Gould says Biosecurity New Zealand has evidence that the sea squirt has
been in the Auckland area for several years, and anecdotal stories indicate it
may have been around for as long as ten years.
Over the remaining three months of this financial year (to end of June) the
agency is putting in place a number of research initiatives. These will
look at ways to hold back the spread of Styela clava to high value
areas such as the aquaculture-intense Marlborough Sounds, to gain a wider
picture of where it is, and to better understand how the organism operates in
the New Zealand environment.
"We're kicking off research into small-scale control measures in
the two satellite locations of Tutukaka and Lyttelton. In the case of
Lyttelton, the aim is to scope the actual size of the population there and
investigate treatments and controls that could reduce the risk of spread from
there," says Brendan Gould.
Biosecurity New Zealand is also planning to survey a handful of additional
marinas and ports that were not checked in the 24-location surveillance
programme in November and December 2005.
"These additional locations will be selected on the basis of their
proximity to high-value locations and the degree of vessel movements through to
high-value locations," says Mr Gould.
Biosecurity New Zealand says raising public awareness of how the sea squirt
is spread remains the most effective means of slowing its spread to
Imposing movement controls on vessels travelling from infested areas or into
non-infested areas was investigated, but has been ruled out as impractical by
both Biosecurity New Zealand and those involved in boating and transport.
"In the end, it is the responsibility of marine users, whether
they're boaties, marine farmers, shipping companies, fishing boats…
to ensure the sea squirt and other marine pests that could arrive here are not
spread around the country," says Brendan Gould.
"Keeping vessel hulls clean of fouling is going to have to become as
second nature as clicking your seatbelt."
Biosecurity New Zealand will continue to target the boating public and other
marine users with information on how to prevent the spread by ensuring vessel
hulls are cleaned and treated with anti-fouling paints where appropriate.
Since the sea squirt incursion was detected, Biosecurity New Zealand has
spent approximately $1.5 million on researching the organism, surveillance for
its geographical spread, following up more than 300 public calls about
suspicious finds and undertaking public education and awareness.
A proposal for the long term management of Styela clava after the financial
year ending June 2006 is being finalised.
Information about the seasquirt is available at: www.biosecurity.govt.nz/seasquirt
Senior Communications Adviser
Biosecurity New Zealand