Source: Northland Regional Council
A small patch of invasive exotic Caulerpa seaweed has been detected and treated at Smugglers Bay near the entrance to Whangārei Harbour.
The roughly one-metre-wide patch was discovered by Northland Regional Council (NRC) divers undertaking marine surveillance alongside the Department of Conservation.
The seaweed has now been confirmed as exotic Caulerpa, an invasive species already present in parts of the Bay of Islands.
NRC Chair of the Biosecurity and Biodiversity Working Party, Councillor Jack Craw, said the early detection highlights the importance of ongoing biosecurity work and having an in-house dive team.
“This is exactly why we invest in marine biosecurity surveillance, including maintaining our own dive capability. Early detection gives us the best possible chance to respond quickly and prevent spread.”
NRC immediately implemented a rapid response, treating the affected area using a benthic mat with chlorine applied underneath, an established method for small infestations.
“Our teams acted quickly to contain and treat the site using proven methods. Taking a cautious approach is critical with Caulerpa, which can spread from even very small fragments,” says Councillor Craw.
Follow-up dive surveys of the surrounding area have not identified any further Caulerpa. However, additional surveillance will continue as a precaution.
Councillor Craw say the detection reinforces the importance of vigilance.
“We know Caulerpa doesn’t move long distances on its own. This is most likely human-assisted spread, which highlights how important it is that everyone using our coastal waters plays their part.”
NRC’s Coastal Central Councillor Cr Macdonald says the swift action should reassure the community.
“It’s encouraging to see such a fast and coordinated response. Protecting our harbour is a shared responsibility, and simple steps from boaties and fishers can make a real difference.”
Exotic Caulerpa can be spread when fragments are carried on anchors, chains, or fishing and dive gear.
Boaties, fishers and divers are urged to:
- Check anchors, chains and equipment before leaving a site
- Remove any seaweed and secure it so it cannot return to the water
- Dispose of it in a rubbish bin on land.
Anyone who thinks they have seen exotic Caulerpa is urged to report it immediately to Biosecurity New Zealand by calling 0800 80 99 66 or by completing the online reporting form at report.mpi.govt.nz
NRC is working closely with Biosecurity New Zealand (MPI), the Department of Conservation, local hapū and iwi on ongoing surveillance and response planning.
Councillor Craw said monitoring would remain a priority.
“We will continue working closely with our partners to maintain surveillance in the area and take any further action needed to protect Northland’s marine environment.”