Authorities in Northland expect to check more than 2000 boat hulls this summer as their annual hunt for marine pest species gets under way. Photo / NRC
Authorities in Northland expect to check more than 2000 boat hulls this summer as their annual hunt for marine pest species gets under way. Photo / NRC
Summer hull checks of about 2000 vessels will begin again in Northland soon.
The checks are especially significant this year as officials celebrate the eradication of Mediterranean fanworm from Mangōnui Harbour.
The milestone for Mangōnui follows five years of monitoring and removal by the Northland Regional Council (NRC) withBiosecurity New Zealand co-funding seabed and structure searches under a cost-share agreement - each agency investing about $3500 annually in these surveys.
The infestation began in 2020 when a vessel moored in the harbour was found during NRC’s annual surveillance programme to be carrying a large quantity of fanworm. NRC hauled the boat out and cleaned it, while divers removed several fanworms from the seafloor beneath.
NRC biosecurity manager marine Kaeden Leonard said while there had been no official announcement as to Mangōnui Harbour’s fanworm-free status, the council and Biosecurity NZ were confident this incident had not resulted in the spread of fanworm throughout the harbour.
Leonard said there had been no further detections of fanworm in five years of ongoing annual dive surveys, “which is extremely encouraging and suggests the response was effective”.
He said the case underscored the critical importance of ongoing surveillance. It also reinforced the need for boaties to ensure their vessels are clean before moving to a new harbour or destination.
Under NRC’s Marine Pathway Management 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, Leonard said.
Leonard said when cleaning their vessels, boaties needed to double-check niche areas, including the base of the keel, inside intakes and bow thrusters.
Mediterranean fanworm has been present in Whangārei Harbour for more than a decade and is now widespread on artificial structures and the seafloor.
There are no practical tools to make a lasting difference where this pest is already well-established. A single fanworm can release more than 20,000 larvae per spawning event, so reinfection happens quickly even after localised removals.
Leonard said; “Many artificial structures, such as the Parua Bay floating jetty, are inspected twice annually as part of MPI’s High Risk Site Surveillance programme. This surveillance focuses on detecting new-to-NZ species or detecting range extensions early, so that we can respond effectively if required”.
They needed to be conscious that some of Northland’s harbours (Tutukākā and Mangōnui) are currently fanworm-free and that active removal is under way in others, including Mangawhai Harbour.
As part of NRC’s annual summer hunt for marine pests, its staff divers and contract divers will, in November, begin inspecting more than 2000 boat hulls across Northland.
“Summer is the peak boat movement time in Northland, and this work is part of an ongoing search targeting unwanted pests threatening the region’s marine environment,” Leonard said.
The programme typically runs until May and targets local and visiting vessels, from small recreational craft to large commercial ones.
Council works closely with Northland haul-out facilities, which report anything unusual in their area. Hull surveillance is critical because it detects vessels in the water that have transferred pests such as fanworm, enabling rapid mitigation.
Last summer (2024/25), NRC inspected 2310 hulls at 14 locations. While most boat owners complied with the biofouling rules, several vessels were still found carrying listed pests, including fanworm, in areas where those species are not known to be present,” Leonard said.
“Our team works closely with these vessel owners to ensure risks are mitigated quickly. This often means hauling the vessel out of the water for cleaning at the owner’s expense.”
Illegal in-water cleaning can result in a $750 fine. Anyone who finds a marine pest should contact NRC immediately on 0800 002 004. Boat owners could email marinebiosecurity@nrc.govt.nz to check if their vessel was inspected.
Sarah Curtis is a news reporter for the Northern Advocate, focusing on a wide range of issues. She has nearly 20 years’ experience in journalism, most of which she spent reporting on the courts in Gisborne and on the East Coast.
