A Paihia-based commercial diver resumes his search for unwanted Mediterranean fanworm at Opua.
A Paihia-based commercial diver resumes his search for unwanted Mediterranean fanworm at Opua.
Divers will inspect more than 2000 boat hulls in a seven-month hunt for unwelcome marine hitchhikers around Northland harbours.
The six divers will begin the hull inspection programme in the Bay of Islands next month, looking for Mediterranean fanworm (Sabella Spallanzanii).
Pests threaten the marine environment and the fanworm hasbecome well-established in Whangārei Harbour over recent years.
Mediterranean fanworm is the largest fanworm in New Zealand, with a body up to 20mm wide and 800mm long. It has a banded orange, purple or white crown of fan-like feeding tentacles extending out of a leathery, flexible tube.
A close-up of one of the recovered Opua fanworm showing the fanlike crown of feeding tentacles that extend out of its tube, giving it its name.
It can quickly form dense colonies, forcing out native species. Sabella have been found growing on scallops in Whangārei Harbour and can potentially spread on to other shellfish, including farmed species.
Although prevalent in Whangārei Harbour, it was largely under control in other areas Northland Regional Council (NRC) biosecurity and biodiversity working party chairman Jack Craw said.
"Some has been successfully eradicated. We believe we can eradicate fanworm from the Bay of Islands and we're reasonably close. Records show a huge reduction."
Northland-based dive contractors Marine Environmental Field Services, who have done the surveys for the past three years, will be back in the water again this season.
Craw said if a vessel in Whangārei Harbour is found to have fanworm, an inspection notice and warning letter will be left on the vessel advising the owner its hull needs to be cleaned if it is going to move to another designated place/harbour.
In all other Northland harbours, Mediterranean fanworm found on a vessel hull will result in a direction to haul it out for cleaning immediately (at the owner's cost. The owner may also be prosecuted.
Most boat owners and marina operators have been co-operative and supportive, Craw said.
Authorities are keen to ensure vessels are free of marine pests before owners start travelling with the onset of warmer summer weather.
Marina operators had been requiring a receipt proving a vessel conforms to what's been dubbed the "six or one" initiative: being anti-fouled within the previous six months or having had a "lift and wash" within the previous month.
Covid-induced border restrictions have paused international marine pests, but divers would also be on the look-out for other foreign invaders already known to be in New Zealand.
NRC biosecurity marine manager Kathryn Lister said in addition to rules covering transportation of marine pests, council rules limit the amount of "biofouling" - build-up of microorganisms, algae, plants and pests - vessels can be carrying when they enter new spots.
Mediterranean fanworm on a Northland boat.
"Vessel hulls are the most common way for marine pests to hitch a ride and our Marine Pathway Management Plan aims to manage this issue."
Under the plan, any vessel entering Northland waters or moving from one harbour to another must have no more than light fouling, defined as a slime layer and/or barnacles and a few patches of macrofouling.
"Marine pests can hitchhike and hide within boat fouling, so preventing the movement of infested vessels is the best way to stop the spread of marine invaders."
She said marine pests found on vessels have often been concealed in "niche" areas, which require special attention when applying antifouling or during a lift and wash.
"We strongly recommend double-checking these niche areas, like the base of the keel, and inside intakes and bow thrusters, before your vessel goes back in the water."
Boat owners keen to know if their boat has been inspected – and the results – are welcome to email marinebiosecurity@nrc.govt.nz.
More information on the council's rules and requirements can be found at www.nrc.govt.nz/marinebiosecurity and www.marinepests.nz.
