Tutukaka fanworm discovery concerns

23 Apr 2015, 9:55 AM

Experts are cautiously optimistic one of Northland’s most iconic coastal areas may have escaped a potentially disastrous Mediterranean fanworm invasion – but warn an unwelcome discovery there shows the need for ongoing vigilance.

Mediterranean fanworm on boat hullThe discovery of fanworm on the hull of this boat in Tauranga sparked the Tutukaka fanworm search.

An extensive search for fanworms at Tutukaka's marina – sparked by the Tauranga discovery of an infested vessel that had spent some months in Northland – recently turned up three juvenile fanworms on marina structures. The Northland Regional Council (NRC) and Ministry for Primary Industries (MPI) have joined forces to respond to this detection.

Irene Middleton, an aquatic biosecurity specialist for the NRC, says results just back from the Marine Invasives Taxanomic Service (funded by MPI in Wellington) have fortunately confirmed the young Tutukaka fanworms were too immature to have reproduced.

"However, we will need to wait until spring to resurvey the marina to ensure divers have not missed any young worms, which if present now would simply be too small to be seen with the naked eye."

In the meantime the council was stepping up detection efforts and working with marina management to better assess the biosecurity risks of vessels before they enter the Tutukaka marina. Tutukaka is a well-known gateway to the world-renowned Poor Knights Islands Marine Reserve, ranked among the world's top 10 dive sites.

"If it's suspected there may be fanworms on your hull, council divers will inspect the vessel and you'll be asked to haul it out and clean it if marine pests are present."

Ms Middleton says the initial discovery came after a vessel hauled out of the water in Tauranga was found to have several hundred large fanworms on its hull. That same vessel had earlier spent nine months in the Tutukaka marina, including over winter and spring when the fanworm is known to spawn.

"The Tutukaka discovery was the first time we have found fanworms on a structure or substrate anywhere outside of Whangarei Harbour, where the pest was first encountered in Northland in 2012."

Mediterranean fanworm is an internationally recognised marine animal pest that competes with native filter-feeding species like scallops and mussels, can heavily foul marinas and other structures and may impact on farmed shellfish.

Northland is currently one of only two New Zealand regions to recognise the value of its marine environment with specific rules to prevent the establishment and spread of marine pests.

Ms Middleton says as part of the Tutukaka marine checks – which had been supported by MPI and the Department of Conservation – fanworms had also been found on two other vessels in the marina.

"Both had originated from Auckland, which has an established fanworm problem in its marinas. Although their hulls had been cleaned prior to visiting Northland, it appears 'niche' areas on those vessels had not been checked for fanworms'."

"These include places like intakes and outlets, propellers, around rudders, keel bases, behind anodes, inside bow thrusters, and the places where cradle arms or props sit." Marine pests can be concealed in these areas and can easily be missed during antifouling or cleaning.

Kathy Walls, a senior adviser for MPI, says the Tutukaka discoveries show the importance of checking and cleaning boats' entire hulls. Vessel owners can help by fully disclosing the visits they have made to locations known to have fanworm problems in the preceding few months.

"Know what pests are or may be present in your local marina and know any rules surrounding these, especially when travelling to other places."

Ms Walls says it makes far more practical and financial sense for people to ensure their hulls are clean before heading to regions like Northland, as well as helping ensure that marine pests aren't spread from place to place.

Marie Jordan, Marine Ranger from the Department of Conservation, says that the Poor Knights Islands Marine Reserve is one of the most pristine and popular marine reserves in the country.

"With over 30,000 visitors a year the marine reserve also supports a growing local economy based primarily out of Tutukaka which is its closest port of call."

Ms Jordan says it's really important that users of the reserve are aware they may be carrying marine pests and to check and clean, if necessary, their vessel's hull before arriving in the area.

Mediterranean fanworm information can be found at: www.nrc.govt.nz/marinebiosecurity or www.biosecurity.govt.nz/pests/mediterranean-fanworm