Styela clava seasquirt found on Nelson vessel

Biosecurity New Zealand is currently investigating the detection of a single adult specimen of the invasive sea squirt Styela clava on the hull of a commercial fishing vessel in Nelson.

Work is currently underway to determine whether this find represents an established population in Nelson that has subsequently infested this vessel, or whether the specimen was picked up at another location.

Senior Marine Adviser Brendan Gould says early information suggests that Styela was most likely picked up in Nelson.

“This is because the vessel had been berthed in Nelson for almost nine months and had not been used over this period. Prior to this, the vessel had only made short trips to other ports for restocking and refuelling, limiting the chance of Styela being picked up elsewhere.”

Mr Gould says there is also no history of the vessel visiting any known infested locations. The boat had a significant amount of bio-fouling (marine fouling species) growing on the hull.

“This raises the possibility there may be a small population in Nelson,” Brendan Gould says.

The port had been surveyed for Styela in late 2005 and it was not detected there then. “This suggests that if there is a population there, it does not appear to be widespread. Biosecurity New Zealand is currently checking to determine whether the particular area the vessel was berthed was examined in the original survey.”

In response to the find, Biosecurity New Zealand will be undertaking surface and in-water surveillance of the area where the vessel was berthed and surrounding locations. Should a population be detected, the extent of the infestation will need to be determined to inform any further response action - possibly population containment/management.

Meanwhile, NIWA (contracting to Biosecurity New Zealand) has just this week completed checks of five additional locations around the country for the presence of Styela and it was not detected.

The surveillance was undertaken at Opua, Onehunga/Manukau Harbours, Wellington (Evans Bay and Clyde Quay marinas), Mana Marina and Timaru port and the inspections failed to find any sign of the sea squirt.

This round of surveillance was in addition to an earlier national surveillance exercise (late 2005) and was to gain a clearer picture of where the organism is present in New Zealand.

The national investigation, combined with public reports of finds, has established that Styela is widely spread throughout the Hauraki Gulf, in Lyttelton and in Tutukaka Marina in Northland.

Biosecurity New Zealand is undertaking other research projects as part of the response to Styela clava. A study has begun on the reproductive biology of the creature and this will potentially provide information to underpin any future management activities.

And two scientific research agencies are to undertake population management trials at the two outlying sites of Styela infestation (outside of the wider Hauraki Gulf) - Lyttelton and Tutukaka.

These trials will determine if it’s feasible to control the organism sufficiently in those two locations to prevent its spread from there. This could be particularly helpful in preventing the spread from Lyttelton to important aquaculture areas such as the Marlborough Sounds.

Biosecurity New Zealand continues to run an ongoing public awareness campaign targeting boaties and other marine users and encouraging them to keep their vessels and equipment clean and anti-fouled.

This is the best possible way of preventing the spread of this sea squirt and other marine organisms.

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