Northland teams up to take on invasive squirts

More than 10,000 sea squirts have been removed from a Bream Bay marina in a ground breaking pest control partnership between local authority staff, the marina and student volunteers.
In what organisers believe is a Northland-first, a locally-funded team of four divers removed thousands of Styela clava - an invasive sea squirt and biosecurity threat - in a six-day operation last week.
Organisers are cautiously optimistic the $20,000 clean-up will contain the ocean invader in the Bream Bay area.
The pest was discovered in the Marsden Cove Marina during a national marine surveillance programme in April, prompting officials to try removing it before it became established.
The project was initiated by the Northland Regional Council and marina developer Hopper Developments, supported by staff and students from NorthTec and carried out by local divers from Whangarei-based Northland Underwater Technical Services.
It is largely funded by the regional council and Hopper Developments, the first partnership of its type in Northland.
Craig Brown, chair of the council's environmental management committee, said all too often authorities are left to deal with marine pests which had been allowed to spread unchecked.
"Because in this case the sea squirts were contained within a relatively small area, we were presented with a rare opportunity to both size up the impact of a potential marine pest early and take proactive action to try to limit its spread," he said.
Mr Brown said regular maintenance would be needed to make sure sea squirts stayed out of the marina, but the cost would be lower than controlling the species if it had been left to spread.
Hopper Developments manager Stace Hopper said the company was happy to take part in the clean-up.
"We take marine pests seriously and want to encourage boaties to clean their hulls regularly," Mr Hopper said.
Previous dive surveys, conducted at the nearby Marsden Pt port facilities and just outside the marina, indicated Styela clava was confined to the marina.
Classified as an `unwanted organism' by Biosecurity New Zealand, the sea squirt can bulk up in very high numbers to form large heavy bunches, attaching to almost any surface _ from mooring ropes and marine structures to vessel hulls.
"We don't know how Styela clava will behave in New Zealand over time, but the Northland Regional Council wants to find out if acting now is better than waiting until it's too late, especially when dealing with a valuable harbour like ours," he said.
So far the impact of Styela clava in Whangarei Harbour is thought to be low, although large populations of the pest are building up in Auckland ports and marinas.
Styela clava is usually club-shaped with a tough, leathery skin that varies, it can be brownish-white, yellow-brown or reddish-brown. It favours protected areas like bays and harbours.
Its body is cylindrical, tapering to a stalk. It prefers to settle on hard surfaces, especially man-made ones like jetty and wharf pilings, aquaculture structures and equipment, ropes and lines, and boat hulls. It grows up to 16cm long and grows from the low tide mark down to about 25m.
" For more information, see www.biosecurity.govt.nz/seasquirt.
Caption: Pictured with a few of the 10,000-plus sea squirts removed from the Marsden Cove Marina are, back row from left, Northland Underwater Technical Services divers Murray Smith and Matt Conmee, and Regional Council Marine Officer Craig Gardner. Front row, from left, are divers Irving Nayoan and Kathy Conmee.