Divers discover fanworm pest on boat

Mediterranean fanworm (Sabella spallanzanii) is an invasive aquatic pest.

A second fanworm has been found in Pilot Bay.

The Mediterranean fanworm (Sabella spallanzanii) and several clubbed tunicate sea squirts (Styela clava) were found on the hull of a boat moored in Pilot Bay, Mount Maunganui.

Divers from the Bay of Plenty Regional Council and University of Waikato found the pests, which have become established in other parts of New Zealand, including Auckland's Waitemata Harbour and Lyttelton Harbour.

The pest can grow in dense, thick mats and compete with native plants and animals for nutrients and space.

It can also interfere with boat equipment and aquaculture and affect recreational activities such as diving, by changing the underwater character.

Regional council natural resource operations general manager Warwick Murray said yesterday it made contact with the owner of the boat, who was concerned and agreed to have the vessel hauled out and cleaned.

The divers have been searching for Mediterranean fanworms in the southern end of Tauranga Harbour since the discovery of a single specimen in Pilot Bay in late September. Their dive search is now about 85 per cent complete.

Mr Murray said the fanworms found were too immature to breed.

"We're hopeful that we've caught these incursions before they've become more widely spread," Mr Murray said.

Boat owners are encouraged to clean their hulls regularly and keep their anti-fouling paint in good order. The dive survey is expected to be completed this month, subject to favourable weather and water clarity.