An Auckland boat infested with Mediterranean fanworm and clubbed tunicate sea squirt was discovered on a Pilot Bay mooring in Tauranga Harbour last week.

The discovery was made by Bay of Plenty Regional Council contracted divers during the first round of a new proactive marine pest surveillance programme.

Mediterranean fanworms on the heavily fouled hull of a boat found moored in Pilot Bay, Tauranga Harbour.

This is the third time the marine pest has been found in Tauranga Harbour.

'We've been negotiating with the boat owner to get it hauled out and cleaned as soon as possible,” says Regional Council Biosecurity Officer Hamish Lass.

The vessel was brought to Pilot Bay from Auckland in December last year.

It's estimated to be carrying more than 100 individual fanworms on its hull, as well as a number of clubbed tunicate sea squirts.

Both pests are classified as unwanted organisms under the Biosecurity Act 1993 and are a threat to seafood stocks, aquaculture and local marine life because of their growth and feeding habits.

They can also cause costly damage to boat equipment and marine structures.

The unwanted fanworm and sea squirt have become well established in Auckland's Waitemata Harbour.

'It's frustrating that the boat owner didn't clean his boat hull before travelling to Tauranga, or even when he arrived here,” says Hamish.

'He moored up just after we'd completed our last round of dive surveys in Pilot Bay and found it clear of Mediterranean fanworm.”

The latest find is the third pest-infested boat found in Tauranga Harbour since September last year.

'Mooring holders have an important role to play in preventing incursions like this,” adds Hamish.

'They can stop marine pests from taking hold in Tauranga Harbour by making sure that any boats they allow onto their mooring have clean hulls before they're brought here.”

Hamish says due to the size and number of fanworms on the hull, and the duration that it's been moored locally, it's possible that the fanworms will have spawned in Pilot Bay during the winter and autumn season.

'That will add scale and complexity to our containment efforts,” he says. 'We're working with the Ministry for Primary Industries to develop and implement an appropriate response. It's likely to involve many hours of underwater searching.”

Hamish asks everyone who uses the harbour to keep an eye out for marine pests and boats with heavily fouled hulls, and report them immediately to him at Bay of Plenty Regional Council by calling: 0800 884 880.