Caulerpa brachypus: a non-native seaweed
The non-native seaweed Caulerpa brachypus was found in Blind Bay and Tryphena Harbour, Great Barrier Island (Aotea) in July 2021. This seaweed can spread rapidly and could affect native species. Find out about this unwanted organism and what's being done.
This seaweed can form vast, dense beds, overrunning native species
Caulerpa brachypus is a seaweed native to the Indo-Pacific region, ranging from Africa to Australia, the Pacific Islands, and southern Japan. It is considered an invasive pest in Florida, United States, and Martinique in the Caribbean.
Caulerpa brachypus has fronds up to 10 cm long that rise from long runners or roots known as stolons.
In Australia, it grows below the tideline at between 6 and 10 metres on both hard surfaces and in sandy areas.
In favourable conditions, it can spread rapidly, forming vast, dense beds or meadows.
It can smother and displace native species of algae and harm fish nurseries, disrupting the natural ecology of an area.
How Caulerpa brachypus can spread
Caulerpa brachypus 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 cray 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 this pest get to New Zealand?
It is not known how long this pest has been here or how it arrived. It may have been carried by a visiting international vessel or on a domestic vessel from another, as yet unidentified, infested area in New Zealand.
We do not know how long it has been in Aotea or the scale of the affected area.
What we're doing
Biosecurity New Zealand is working closely with Ngāti Rehua Ngāti Wai ki Aotea and the local community, along with Auckland Council and the Department of Conservation to collectively decide the most appropriate course of action.
A thorough dive survey of Blind Bay was carried out in August 2021. The seaweed was found to be widespread in the bay. It was also found in Tryphena Harbour.
Controlled Area Notice and Rāhui
To minimise the spread of Caulerpa brachypus, Biosecurity New Zealand will place a Controlled Area Notice (CAN) on Blind Bay and Tryphena Harbour to take effect on Monday 20 September 2021. Ngāti Rehua Ngāti Wai ki Aotea will impose a rāhui on the areas to take effect at the same time.
The CAN and rāhui are in place until the end of November. They'll be reviewed based on further information on the spread and potential management options.
Maps of the Controlled Areas
Controlled Area Notice – Legal [PDF, 833 KB]
What you can and can’t do
- You can swim, dive (without gathering kai moana), paddle or kayak, and boat in the Controlled Areas, so long as you do not anchor.
- You can launch a boat from Blind Bay or Tryphena to go fishing in other areas outside the 2 controlled zones.
- It will be illegal to remove any marine life (fish, seaweed, shellfish, or crayfish) from Blind Bay or Tryphena Harbour.
- Boats or equipment (like cray pots) cannot be taken into these areas for seafood gathering. Vessels can continue to move through the Controlled Areas but if they anchor, will need a permit from Biosecurity New Zealand to leave the Controlled Area. This will stipulate that the anchor and anchor chain must be thoroughly cleaned of any seaweed.
- All marine equipment used for water-based activities (footwear, wetsuits, boat trailers) 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 be cleaned with freshwater and completely dried (inside and out) before being reused in the ocean. It must not be used in the ocean for 48 hours after cleaning.
- Any vessels that have anchored within the 2 affected bays cannot be moved out of the Controlled Area without a permit.
To apply for a permit, complete the application form and email it to: Caulerpa2021_Liaison@mpi.govt.nz
Apply for permit form [PDF, 132 KB]
How you can help
Keep an eye out for Caulerpa brachypus. If you believe you have seen it in areas outside of Blind Bay or Tryphena Harbour:
- note the location
- take a photo if possible
- contact Biosecurity New Zealand on 0800 80 99 66.
Images to help you identify the seaweed
Caulerpa brachypus [PDF, 822 KB]
Caulerpa – Great Barrier Island biosecurity response [PDF, 943 KB]
Who to contact
If you have any questions about Caulerpa brachypus, email email@example.com