Fanworm find raises concerns

The Acheron pictured at the Poor Knights recently, before Mediterranean fanworm was found on its hull. Photo / Facebook

A cluster of invasive Mediterranean fanworms have been found on a vessel brought into the Tutukaka marina by one of New Zealand's top marine tourism operators.

Fourteen juvenile worms were found on the hull of Dive! Tutukaka's new charter vessel Acheron last week during a routine survey of the marina by Northland Regional Council divers.

The fanworm (Sabella spallanzanii) can live in tidal mud or sand, on rocks and marine structures, forming dense colonies that can affect native and farmed shellfish species.

The boat was known to be infested with the vigorous pest at its previous home port of Auckland, where it was bought by Dive! Tutukaka.

Company co-owner Jeroen Jongejans said he believed the boat became infested at Tutukaka, a theory he said was backed up by the worms being in a juvenile stage.

He was satisfied the Acheron was clean before it came north from Auckland about six months ago. The vessel had been out of the water in Whangarei for four weeks before being taken to Tutukaka.

Before the infestation was found, the award-winning dive and boat excursion company had already taken the new charter vessel on a trial to the Poor Knights Islands Marine Reserve.

Mr Jongejans said he was taking the find very seriously.

"We found out about it on Tuesday and we had an action plan in place the next day."

That plan involves divers treating the infected areas with chlorine and sealing them. Small sections of damaged wood on the hull will be sealed with copper plates to reduce the "real estate" fanworm can set up home in, marina manager John Warren said. The owners have a week to do the work.

Northland Regional Council's inflatable floating dock, purchased to assist with isolating vessels during fanworm treatment, is too small to use on the 121m Acheron.

Council biosecurity manager Don McKenzie confirmed the fanworm on the Acheron were the only ones found in last week's search.

He said the 14 worms - too young to breed - "posed no risk".

Mr McKenzie said the organisms were in an inaccessible place on the hull.

Meanwhile, Tutukaka marina trustee Ian Russell said he is angry that, in light of the Acheron's history of serious infestation, it had not been flagged as a danger before being brought into Northland.