Caulerpa brachypus and Caulerpa parvifolia in Northland

These seaweeds can form vast, dense beds

Caulerpa brachypus and Caulerpa parvifolia are seaweeds exotic to New Zealand. Exotic means they have come from overseas. They are native to the Indo-Pacific region, ranging from Africa to Australia, the Pacific Islands, and southern Japan. Caulerpa brachypus is considered an invasive pest in Florida, the United States, and Martinique in the Caribbean.

Both seaweeds are closely related and appear identical. They have fronds up to 10 centimetres long 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.

In favourable conditions, they can spread rapidly, forming vast, dense beds or meadows.

How exotic Caulerpa species can spread

The 2 seaweeds can be spread through breaking into little pieces. This can happen, for example, by wave action or when anchors and fishing gear are moved into or through weed beds.

Fragments are also carried easily on coastal currents.

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).

Detection in Bay of Islands – 31 May 2023

Divers searching the waters around Te Rāwhiti, the Bay of Islands, found a substantial amount of exotic Caulerpa seaweed in May 2023. The infestation found so far in Omākiwi Cove extends out into the Albert channel and varies in density from 90% coverage in sheltered areas to small sparse patches in the deeper waters.

It is likely that a controlled area notice (CAN) will be placed on a defined area around Omākiwi Cove in the Bay of Islands, which will set restrictions and conditions to prevent the spread of this seaweed. Local mana whenua may also put in place a rāhui. The extent of any CAN will be further reviewed when further dive surveillance in the area is completed.

Find out more

Media release issued 31 May 2023 about the Omākiwi detections

Boaties and fishers can help stop the spread of exotic seaweed

You can help

Keep an eye out for exotic Caulerpa species and report suspected sightings to us. We are particularly keen to hear about sightings outside of the known areas at Blind Bay, Tryphena Harbour, and Whangaparapara harbours at Great Barrier Island; the south-western coastline of Great Mercury Island, and Omākiwi Cove in Northland. If you've seen exotic Caulerpa:

note the location
take a photo if possible
contact Biosecurity New Zealand on 0800 80 99 66
or complete the online reporting form at report.mpi.govt.nz

Images to help you identify the seaweeds

A dense mat of *Caulerpa brachypus* in Blind Bay.

*Caulerpa brachypus* growing in Blind Bay

*Caulerpa parvifolia* at Great Mercury Island

Prevent the spread

If boating, diving, or fishing – check your gear – anchors and chains especially. If you see any seaweed on your equipment, chuck it straight back in the waters it came from. Don’t move it somewhere else.

Know where Caulerpa is

Know the rules about anchoring and fishing there

What we're doing

Biosecurity New Zealand is working closely with Aotea, Ahuahu and Te Taitokerau mana whenua and the local communities, along with Northland Regional Council, Auckland Council, the Waikato Regional Council, and the Department of Conservation to collectively decide the most appropriate course of action.

To find out more, you can subscribe to receive regular Caulerpa newsletter updates.

Subscribe to the Caulerpa newsletter

Questions we’re frequently asked about exotic Caulerpa and its management [PDF, 417 KB]

Public presentation on the biosecurity response to exotic Caulerpa [PDF, 4 MB]

Controlled Area Notice and rāhui at Aotea Great Barrier Island and Ahuahu Great Mercury Island

To minimise the spread of exotic Caulerpa species, Biosecurity New Zealand has placed a Controlled Area Notice (CAN) on 3 affected harbours at Great Barrier Island – Blind Bay, Tryphena Harbour, and Whangaparapara Harbour, and over 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.

These controls are in place until 31 October 2023.

An exotic Caulerpa species was found in Omākiwi Cove in the Bay of Islands in May 2023. Work is underway with mana whenua and the Northland Regional Council to determine next steps in this region.

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]

Clarification on shoreline boundaries of CANs

From 11.59pm on 30 April 2023, there will be a small update in place to the Controlled Area Notice for both islands clarifying the shoreline boundaries of the controlled areas. The CAN covers up to and including the high tide mark in all four bays under controls (Tryphena Harbour, Whangaparapara Harbour and Blind Bay at Aotea Great Barrier Island, and Ahikopua Point – Maunganui Point at Ahuahu Great Mercury Island).

Conditions of the CAN

Aotea Great Barrier Island

You cannot anchor a vessel in the three 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 remains prohibited. Spear fishing, gathering kina and crayfish, longlining, net fishing and drift fishing are not allowed.
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

Apply for a permit [PDF, 150 KB]

Exotic Caulerpa Controlled Area Notice Permitting Specifications – Guidance [PDF, 830 KB]

For advice about permits:

email Caulerpa@mpi.govt.nz
freephone 0800 80 99 66

Ahuahu Great Mercury Island

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.

Further CAN information for both islands

Boats or equipment (for example, crayfish pots) cannot be taken into the controlled areas for seafood gathering.
You can swim, dive (without gathering kai moana), paddle, kayak, and boat in the controlled areas. However, all marine equipment used for water-based activities (for example, footwear, wetsuits, boat trailers, kayaks) cannot be removed from the controlled areas without first checking for seaweed and removing it.
Any weed or plant matter found on gear must be placed back into the same waters in the controlled area. This equipment must then be rinsed off with water before being reused in the ocean.
You can launch a boat from any of the controlled areas to go fishing in other areas outside the controlled areas.
Vessels can continue to move through the controlled areas but anchoring, permitting, or cleaning requirements must be met.