Caulerpa brachypus and Caulerpa parvifolia seaweeds

Help stop the spread of exotic caulerpa

Report sightings, keep your boat and gear clean, and know the rules

Caulerpa seaweed at the bottom of the ocean floor — A mat of exotic caulerpa seaweed on the seafloor near Aotea Great Barrier Island.

Tell us if you see it

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 80 99 66
Or complete the online form at report.mpi.govt.nz

Video: How to identify and report exotic caulerpa – YouTube

Keep your boat and gear clean

Exotic caulerpa can be easily spread as small pieces on vessels and marine equipment.

Before moving locations, check your anchor, anchor chain, and gear for any seaweed. Remove it and return it to the area it came from.
If you're already back at shore, remove it, and put it in the rubbish. Do not put it back in the sea.

Find out more about how to stop caulerpa spreading

Know the rules

There are rāhui and legal restrictions on anchoring and fishing in areas known to have exotic caulerpa. You may need a permit.

Check the Controlled Area Notice for details

How to recognise exotic caulerpa

The exotic seaweeds Caulerpa brachypus and Caulerpa parvifolia are closely related and appear identical.

They have green fronds up to 10 centimetres long in the shape of oar blades that rise from long runners or roots known as stolons.

They can be found growing below the tideline at between 2 metres and 30 metres on both hard surfaces and in sandy areas. When established, exotic caulerpa can cover large areas of the seafloor in dense mats.

Our images of caulerpa, both in the sea and washed up on shore, will help you recognise the seaweeds.

Photos of caulerpa

Diver photographing caulerpa seaweed. (Photo credit: NIWA)

Exotic caulerpa seaweed on the seafloor. (Photo credit: NIWA)

A diver holding clumps of caulerpa. (Photo credit: NIWA)

A mat of exotic caulerpa washed up on the beach. (Photo credit: NIWA)

A small patch of *Caulerpa brachypus* growing in Blind Bay, Aotea Island. (Photo credit: NIWA)

*Caulerpa parvifolia* at Ahuahu Great Mercury Island. (Photo credit: NIWA)

Why this seaweed is a problem

These exotic caulerpa can spread rapidly, forming vast, dense underwater fields.

They compete with other species, including our own native caulerpa species, for space and upset the balance of local ecosystems. This presents a risk to recreational, cultural, and commercial marine activities.

What we're doing to control exotic caulerpa

Biosecurity New Zealand, mana whenua and other partners including local authorities are working together to control this pest where possible.

Since its detection at Aotea Great Barrer Island in 2021, there has been a consistent and thorough effort to understand the pest and its challenges, trial treatments and work to prevent its spread.

This includes placing legal restrictions on some boating and fishing activities. Those restrictions are detailed in a Controlled Area Notice (CAN). Rāhui have also been placed over areas where the invasive seaweed is known to be present.

Experts are exploring and trialling options for killing or removing the seaweed, which international experience tells us is extremely challenging with a lack of control tools and the large scale of some of the infested areas in New Zealand.

Campaigns are underway to educate people about exotic caulerpa and how to stop its spread.

Surveillance to determine where the seaweed is present is ongoing.

Technical advice on controlling exotic caulerpa

Response actions and decisions are informed by scientific advice. Since the discovery of exotic caulerpa in New Zealand in 2021, groups of international technical and scientific advisors with expertise in marine algae, control methods and Mātauranga Māori, have convened to advise on the situation and recommended actions.

In June 2023, an advisory group gathered to provide advice on the use of diver-controlled suction dredging to remove exotic caulerpa.

The group recommended an immediate scientific trial to provide vital information on the method's potential in our unique environmental conditions and the remote locations of our caulerpa infestations. Trials are about to start at 2 locations – Aotea Great Barrier Island and Te Rāwhiti Inlet in coming weeks (dated 20 July 2023).

Exotic Caulerpa Suction Dredge Technical Advisory Group Report [PDF, 933 KB]

Impact of exotic caulerpa on native species at Aotea – a NIWA interim report

Biosecurity New Zealand commissioned NIWA to assess the impacts of exotic caulerpa on the ecosystem and taonga species at Aotea Great Barrier Island.

In a multi-year study, NIWA is monitoring 18 permanent sites in the 3 affected bays at the island - Blind Bay, Tryphena Harbour and Whangaparapara Harbour.

They are looking at any effects on native species, as well as how the caulerpa itself is affected by wave energy and light availability, including storms.

In an interim report, observations suggest that exotic caulerpa may be having a negative impact on the condition and population dynamics of taonga species. However, there is further sampling and analysis required before the extent of any impacts on most of the habitats will be known.

NIWA returned to the sites in May 2023. The report from this phase of the research project is still in development.

Impact of exotic Caulerpa on native species at Aotea/Great Barrier Island – Phase 1 [PDF, 1.9 MB]

Where exotic caulerpa has been found

Exotic caulerpa was first found in New Zealand waters in 2021 at Great Barrier (Aotea) Island and then later at Great Mercury (Ahuahu) Island.

In 2023, exotic caulerpa washed up at Omākiwi Cove in the Bay of Islands led to the discovery of a significant amount of the invasive seaweed in the Te Rāwhiti inlet.

In July 2023, small 20cm to 30cm patches of exotic caulerpa were found in waters near Kawau Island in the Auckland region.

Exotic caulerpa has most recently been found off the northern coastline of Waiheke Island, between Waiheke Bay and Thompson’s point. The caulerpa in this area appears to consist of small young plants in the early stages of development, but surveillance is required to determine its extent.

It is not known where or when exotic caulerpa first entered New Zealand waters. It is considered likely that it arrived on a vessel travelling from Australia or the Pacific. The amount found suggests it has been here for several years.

Controlled Area Notices

Legal controls are in place in 3 locations to help prevent the spread of exotic caulerpa from these affected areas to the rest of the country.

Controlled Area Notices (CANs) are in place at:

Aotea Great Barrier Island
Ahuahu Great Mercury Island
Te Rāwhiti Inlet in the Bay of Islands.

The restrictions on anchoring, movement of vessels, and fishing are largely similar in the 3 areas, but with some specific conditions for each location.

Mana whenua have imposed rāhui in these areas with the same restrictions.

Ngāti Paoa has imposed a rāhui at Waiheke Island on disturbing the seabed or anchoring within 1 nautical mile (1.8 kilometres) of Thompson’s Point or Onetangi Bay.

Te Rāwhiti Inlet Controlled Area Notice (CAN) and rāhui

It is illegal to fish or anchor a vessel in a defined area (refer to the map) of Te Rāwhiti Inlet.

The area under controls is bounded by Whau Point, the south-eastern tip of Te Ao Island, the eastern shoreline of Poroporo Island and the northern tip of Tokatokahau Point up to the high-tide area.

Under the CAN, it is illegal to remove any marine life (including fish, shellfish, koura (crayfish) or seaweed from the zone. This means any form of fishing is banned. This includes spearfishing, crayfishing, kina and other shellfish gathering, net fishing and drift fishing from any kind of vessel.

It is also illegal to take vessels or dive gear (for example, wetsuits, fins, tanks) into the controlled area for fishing.

No anchoring is allowed in the controlled area other than for a very few permitted activities such as for scientific research or where residents are reliant on a vessel for regular transport. For those activities, you'll need to get a permit from us. Anchoring in an emergency (for example, to shelter from weather) is allowed without a permit.

Permit application form for anchoring or moving vessels [PDF, 99 KB]

Map of Te Rāwhiti Inlet

Map of the affected area (coloured red) in Te Rāwhiti inlet, the Bay of Islands

Detailed caulerpa Controlled Area Notice map: Te Rāwhiti [PDF, 1.8 MB]

Controlled Area Notice for Te Rāwhiti Inlet [PDF, 731 KB]

Great Barrier Island and Ahuahu Great Mercury Island Controlled Area Notice (CAN) and rāhui

A Controlled Area Notice is in place over 3 affected harbours at Great Barrier Island – Blind Bay, Tryphena Harbour, and Whangaparapara Harbour. The CAN also covers an area of the south-western coastline of Ahuahu Great Mercury Island.

Mana whenua for the islands have imposed a rāhui on the same areas.

Aotea Great Barrier Island CAN conditions

You cannot anchor a vessel in the 3 harbours under controls – Blind Bay, Whangaparapara Harbour and Tryphena Harbour.
Anchoring is only allowed in an emergency (for example to seek shelter in a storm) or with a permit from Biosecurity New Zealand for some limited circumstances (for example if you live at Aotea and need a vessel for routine transport, or for scientific research).
A permit is not required in an emergency.
Rod and line and hand line fishing is allowed from the shore, or from structures fixed to the shore – for example wharves and jetties.
All other fishing is prohibited, including: spear fishing, gathering kina and crayfish, longlining, net fishing and drift fishing.
To apply for an exemption permit to anchor in Blind Bay, Whangaparapara Harbour, or Tryphena Harbour, complete the application form and email it to Caulerpa@mpi.govt.nz

Permit application form for anchoring or moving vessels [PDF, 99 KB]

Ahuahu Great Mercury Island CAN conditions

No fishing is allowed in the controlled area.
Anchoring is allowed in the controlled area, which covers an area of the south-western coast of Ahuahu Great Mercury Island between Ahikopua Point and Maunganui Point.
Vessel operators are required to check and clean the anchor and chain before moving to another area.
Any visible seaweed should be removed and returned to the water in the area, and the anchor and chain should be rinsed.

Controlled Area Notice for Great Barrier Island and Great Mercury Island [PDF, 1.4 MB]

Maps of the controlled areas

Caulerpa Controlled Area Notice: Zone A – Tryphena Harbour, Great Barrier Island [PDF, 234 KB]

Caulerpa Controlled Area Notice: Zone B – Blind Bay, Great Barrier Island [PDF, 229 KB]

Caulerpa Controlled Area Notice: Zone C – Whangaparapara Harbour, Great Barrier Island [PDF, 1.3 MB]

Caulerpa Controlled Area Notice: Zone D – Ahikopua Point – Maunganui Point – Great Mercury Island [PDF, 3.6 MB]

Permits and guidance

To anchor in any of the caulerpa controlled areas, you must have a permit.

Apply for a permit to anchor in a controlled area [PDF, 99 KB]

Permit guidance

Exotic caulerpa Controlled Area Notice permitting specifications – guidance [PDF, 830 KB]

Permit advice

Email caulerpa@mpi.govt.nz

Freephone 0800 80 99 66

Stop the spread of exotic caulerpa

One of the main ways this pest spreads is by breaking into fragments which can easily float to other areas and take root or attach to marine equipment and relocate to a new location.

Pieces can get tangled in or stuck on equipment (for example, boat anchors and chains, nets, dive and fishing gear, and crayfish pots).

It can survive out of water for up to a week or more if it's in a moist location (like in an anchor locker or a bunched-up fishing net).

Before you leave any anchorage or anchor site in New Zealand waters, check your anchor, anchor chain, ropes or fishing gear for seaweed.

If you have an automatic anchor retrieval system, still keep watch for seaweed pieces. Remove any seaweed and throw it back in the waters it came from.

If you suspect you’ve seen exotic caulerpa, report it.