Caulerpa exotic seaweeds found at Great Barrier and Great Mercury islands

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, 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).

How did they get to New Zealand?

It is not known how long these 2 Caulerpa species have been here or how they arrived. It is possible the 2 different seaweeds were carried together by a visiting international vessel or on a domestic vessel from another, as yet unidentified, infested area in New Zealand.

What we're doing

Biosecurity New Zealand is working closely with Aotea and Ahuahu mana whenua and the local communities, along with 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.

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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 Caulerpa brachypus and Caulerpa parvifolia, Biosecurity New Zealand has placed a Controlled Area Notice (CAN) on the 3 affected harbours at Great Barrier Island – Blind Bay, Tryphena Harbour, and Whangaparapara. Aotea mana whenua has imposed a rāhui on the same areas.

The CAN and rāhui are in place until at least 30 June 2022.

At 11.59pm on 19 April 2022, this CAN was extended to include similar restrictions at Ahuahu Great Mercury Island.

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]

What you can and can’t do

You can't remove any marine life (fish, seaweed, shellfish, or crayfish) from the water at Blind Bay or Tryphena and Whangaparapara harbours or the western bay of Ahuahu Great Mercury Island between Ahikopua Point and Maunganui Point. This is to prevent any Caulerpa that may be in the area being disturbed by fishing activity and then spread to other areas.
Boats or equipment (like crayfish pots) cannot be taken into these areas for seafood gathering.
Any vessels that have anchored within the 3 affected locations at Aotea Great Barrier Island cannot lift anchor and move out of the Controlled Area without a permit. This permit will stipulate that the anchor and anchor chain must be thoroughly cleaned of any seaweed before moving.
There is no permitting system at Ahuahu Great Mercury Island. There, vessel operators are required to check and clean the anchor and chain before moving from the Controlled Area. This means removing any visible seaweed and rinsing the anchor and chain.
You can swim, dive (without gathering kai moana), paddle or kayak, and boat in the controlled areas without a permit. 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 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 4 controlled areas.
Vessels can continue to move through the controlled areas but anchoring, permitting or cleaning requirements must be met.

To apply for a permit, complete the application form and email it to Caulerpa@mpi.govt.nz

Apply for a permit [PDF, 132 KB]

For advice about permits:

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

How you can help

Keep an eye out for exotic Caulerpa species. If you believe you have seen them in areas outside of Blind Bay, Tryphena Harbour, and Whangaparapara harbours at Great Barrier Island, or the coastline of Great Mercury Island between Ahikopua and Maunganui Points: