Divers from Bay of Plenty Regional Council and University of Waikato will start searching high risk areas of Tauranga Harbour this week for the unwanted marine pest Mediterranean fanworm (Sabella spallanzanii).

The search has been prompted by the find of three Mediterranean fanworm individuals last week, during routine marine biosecurity surveillance work commissioned by Ministry for Primary Industries.

The Mediterranian Fanworm.

Two fanworms were found in Sulphur Point Marina and one in Bridge Marina.

'It's really disappointing to find this pest in our harbour again,” says Regional Council natural resource general manager.

'Our team put in a huge effort to contain this pest when it was first found here last year and we'll work with MPI do the same again this time.

'We all want to keep Tauranga Harbour healthy, but it's boat owners that can make the biggest difference in preventing the spread of marine pests.

'We need both local and visiting boaties to be vigilant by keeping their anti-fouling paint in good order and ensuring their hull, trailer and fishing gear is thoroughly clean before they travel to a new region or harbour.”

Mediterranean fanworm was first detected in Tauranga Harbour in September 2013 when a single specimen was found by a diver in Pilot Bay.

A further four fanworms were found during subsequent dive surveys.

One was on the hull of a boat that was also infested with clubbed tunicate, another marine pest.

Clubbed tunicates were also found on the hull of a second boat. Both boats had recently travelled to Tauranga from Auckland, and were hauled out for cleaning as soon as they were discovered.

'Once we know just how numerous and widespread the Mediterranean fanworms are, we'll put a plan in place to contain and manage the problem,” says Warwick.

'In the meantime, Tauranga-based boaties can help us to prevent any further spread through the region by taking extra care to clean their gear before heading down the coast or into a new part of the harbour.”

The initial dive survey is expected be completed by the end of next week, subject to favourable weather conditions and water clarity.

The divers will methodically search both marinas where the fanworms were found last week.

The Mediterranean fanworm grows inside a tube it makes itself and can grow to more than 40cm in length.

If established, it can grow in dense clumps, competing with native filter-feeders for food and space.

In high densities it is likely to impact on mussels, oysters and scallops. It can also interfere with boating, aquaculture, and recreational pursuits.

Along with Auckland Harbour, Mediterranean fanworm is also found in Lyttleton and Whangarei harbours, was discovered on two barges in Coromandel Harbour last year, a vessel in Waikawa Bay earlier this year, and is the subject of an elimination programme currently underway in Nelson Marina.