Why exotic caulerpa is a risk to NZ
There are two almost identical species of exotic caulerpa now known to be in New Zealand waters – Caulerpa brachypus and Caulerpa parvifolia. Together we refer to them as exotic caulerpa.
These 2 pest seaweeds can spread rapidly, forming large underwater fields.
The risks from exotic caulerpa
Exotic caulerpa covers more than 1,500 hectares (August 2024) of the upper North Island seabed. Density ranges from thick carpets in some areas to sparsely distributed plants in others. It can compete with other species for space and upset the balance of local ecosystems. This presents a risk to recreational, cultural, and commercial marine activities.
Where exotic caulerpa has been found
Exotic caulerpa was first found in New Zealand in July 2021 at Aotea Great Barrier Island. It has since been confirmed at Ahuahu Great Mercury Island, Te Rāwhiti Inlet in Northland, Kawau Island, Waiheke Island, Mokohinau Islands, Rakino Island, Fantail Bay, Coromandel Peninsula, and Omaha Cove/Leigh Harbour (although this was a small, discrete patch which has been removed).
It is not known where or when exotic caulerpa first entered New Zealand waters. It is considered likely it arrived on a vessel travelling from Australia or the Pacific. The amount found in the various locations suggests it had been here for several years before its first discovery at Aotea.
Current map of known exotic caulerpa locations
Auckland Council has produced an interactive map called the 'Community exotic caulerpa viewer'. The map shows areas where surveillance for exotic caulerpa has taken place and the known locations of exotic caulerpa. As soon as new information is received and validated, the map is updated. Areas surveyed where no exotic caulerpa has been found are shown in green and all known locations of exotic caulerpa are shown in red.
You can expand the map to show all of New Zealand, although exotic caulerpa has only been detected in the upper North Island.
You can use this map to guide decisions on areas to visit by vessel. Areas of exotic caulerpa are best avoided, particularly for any activities that would make contact with the seabed – for example anchoring and fishing.
If you believe you have seen exotic caulerpa in areas outside of those marked, report it to 0800 809 66 or report.mpi.govt.nz
Community exotic caulerpa viewer – marinepests.nz
Maps of known areas in the upper North lsland
These maps may not be as current as the 'Community exotic caulerpa viewer'.
Aotea Island [PDF, 863 KB]
Great Mercury Island [PDF, 1.5 MB]
Te Rāwhiti Inlet [PDF, 2.8 MB]
Waiheke Island [PDF, 3.9 MB]
Kawau Island [PDF, 1.9 MB]
Mokohinau Islands [PDF, 1.4 MB]
Rakino Island [PDF, 983 KB]
Fantail Bay [PDF, 12 MB]
The work being done on exotic caulerpa
Since its discovery in 2021, Biosecurity New Zealand has been working closely with partners, including mana whenua at affected places, local councils, and communities, to try to stop its spread and find or develop potential ways to manage it.
Over $20 million has been spent or allocated to scientific research to understand the pest, surveillance to find it, development and testing of techniques to remove or minimise it, and communications and legal controls to prevent its spread.
While the complete and permanent removal of caulerpa from New Zealand is not feasible with the current tools and the scale of the infestation here, future efforts may include suppression (reducing density to lower the risk of spread) and eliminating it from specific sites.
In 2024, the Government allocated $15 million to enable the creation of an accelerated programme of activities to develop new tools for surveillance and treatment.
Find out about the accelerated programme
Help stop the spread
Everyone working in or enjoying our coastal waters can help stop the spread.
If you operate a vessel, go diving or fishing, or you’re out on the water, you should always check your anchor and gear for seaweed before you move to a new location. If you find any seaweed, bag it and put it in the rubbish on shore.
How to stop the spread of exotic caulerpa
You can also help by following the legal restrictions on anchoring and fishing that are in place at 3 of the areas with exotic caulerpa – Aotea Great Barrier Island, Ahuahu Great Mercury Island and Te Rāwhiti Inlet, Northland.
Find out about the exotic caulerpa legal rules in force
Tell us if you find any exotic caulerpa
Keep an eye out for exotic caulerpa species and report suspected sightings to us. Take a photo, if possible, and note the location. Then either:
- freephone 0800 809 966
- or complete the online form at report.mpi.govt.nz
