top of page
seaweed-being-held-under-the-water.jpeg

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.

On this page

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

  • 2021
    July: Caulerpa brachypus first found at Blind Bay and Tryphena Harbour September: Controlled area notice and rāhui imposed on Blind Bay, Tryphena Harbour, and Whangaparapara Harbour. December: Caulerpa detected in Western Bays of Aotea Great Barrier.
  • 2022
    August: Hauraki Gulf Forum public meeting with Biosecurity New Zealand to raise alarm about threat of Caulerpa to the Gulf.
  • 2023
    April: NIWA releases report: Impact of Exotic Caulerpa on native species at Aotea/Great Barrier Island - Phase 1. May: Caulerpa spreads to the Bay of Islands June: Controlled area notice put in place in Omakiwi Bay July: Caulerpa detected northwest of Kawau August: Caulerpa detected at Waiheke
  • 2024
    January: Caulerpa detected at another location at Aotea Great Barrier Island. February: Government boost to fight against caulerpa. April: Caulerpa found at Mokohinau Islands and Rakino Island. May: Caulerpa detected at Fantail Bay in Coromandel. June: Caulerpa detected at Omaha Cove, but is successfully eliminated by Ngāti Manuhiri and Auckland Council. August: Further funding boost for second phase in exotic caulerpa battle. August: NZIER report on Caulerpa published. December: Controlled area notice put in place at Waiheke.
  • 2025
    February: Caulerpa detected at Repanga/Cuvier Island and Square Top Island, and at new locations at Waiheke and Aotea Great Barrier Island. February: Multi-million-dollar exotic caulerpa control tool projects underway. April: Caulerpa detected between Motukiekie Island and Waewaetorea and Moturua Islands, Poroporo Island, Mohenoititi Islands (including Hauai), Paradise Bay, Otaio Bay, Cable Bay, Waewaetorea Channel, Sunset Bay, Paroa Bay, and Tapeka Point.

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:​

 

 

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.​

bottom of page