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Te Wero Nui: Combatting Caulerpa
We have been working with NIWA, Biosecurity New Zealand and the Auckland Council to contain and remove Exotic Caulerpa since it was first discovered in our rohe in 2023.
Exotic Caulerpa is an invasive seaweed that colonises the seabed by forming large dense mats, killing our native seaweeds that many of our kaimoana - like snapper and crayfish - feed off.
Exotic Caulerpa is easy to spread and hard to remove: a small fragment of the plant caught up in netting or on an anchor and released in another location is more than enough to help this invasive plant spread further.
That's why we're calling it 'Te Wero Nui' - it's a big challenge for us to tackle and get under control but it's important we move quickly. Our approach is remove, reduce, eliminate and that's what we've been doing since caulerpa was discovered in our waters in July 2023.
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Last updated: 15 May 2025
What is Exotic Caulerpa?
Exotic Caulerpa is a seaweed that grows below the tidelines on hard, rocky surfaces and in sandy areas. It can grow up to 40 metres deep, forming dense mats with extensive root systems, suffocating native seaweeds, seagrasses and marine fauna.
They have green fronds up to 10 centimetres long in the shape of oar blades that rise from long runners or roots.
It's able to grow quickly and form large dense mats across the seabed which chokes other plants that our marine life depend on. This can displace fisheries and shellfish resources, and threaten biodiversity.
Exotic Caulerpa has been seen growing on scallops and dog cockle beds, and while no formal research has been completed on the impacts of Exotic Caulerpa in New Zealand, it is likely to negatively impact these species.
Exotic Caulerpa can reproduce from a small fragment and is often picked up by fishing gear or boat anchors which helps spread it to other areas. It is difficult to remove properly and should only be attempted by trained divers.
Exotic Caulerpa Timeline
How you can help
Our best tool against Exotic Caulerpa is awareness. Familiarise yourself with what it looks like, and share this knowledge with your friends and whānau.
Check your fishing and boating equipment for any pieces of Exotic Caulerpa that may have been caught up. If it looks like Exotic Caulerpa, treat it as Exotic Caulerpa, bag it, record the location, take it home to dispose of in the bin or compost, and report the location to MPI.
If you see Exotic Caulerpa in the water, do not try to remove it as this can help it spread further. Take a photo if possible, record the location and report it to MPI.
Sightings and locations can be reported to MPI by:
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freephone on 0800 809 966, or
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completing the online form at report.mpi.govt.nz
If you're a diver willing to train in Caulerpa removal, please get in touch by emailing caulerpa@ngatimanuhiri.iwi.nz
Exotic vs Native Caulerpa
Two types of the non-indigenous algae were discovered in mid-2021 in Aotea, identified by NIWA researchers as Caulerpa brachypus and Caulerpa parvifolia. Both types were given the status of Unwanted Organisms under the Biosecurity Act in September 2021, and are called Exotic Caulerpa to distinguish them from our native seaweeds.
Aotearoa New Zealand has a number of native Caulerpa that occur in similar habitats to Exotic Caulerpa, and these native Caulerpa could be impacted if Exotic Caulerpa continues to spread.
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