OIA25-0161
2 April 2025
Dan Moskovitz
[FYI request #30306 email]
Dear Dan,
Thank you for your email of 5 March 2025 requesting information relating to the reduction in
Caulerpa biomass. Your request has been considered under the Of icial Information Act
1982 (OIA).
You requested the following:
•
It is my understanding that while Exotic Caulerpa continues to spread, some areas
have died back, to our own surprise. Can you please provide any briefings, reports,
or monitoring MPI has done which includes the Exotic Caulerpa dieback?
The Ministry for Primary Industries (MPI) contracted NIWA in late 2024, following reports of
exotic caulerpa reduction in various locations. Surveys were carried out in four locations,
Aotea, Waiheke, Kawau and Omakiwi Cove.
A preliminary report on this work showed large reductions in the cover of exotic caulerpa at
some sites, notably in Onetangi Bay, Waiheke Island and Okupu Blind Bay at Aotea.
The biggest areas of decline have occurred in exotic caulerpa on soft sediment or sandy
seabed. However, it is stil present in large amounts in rocky and intertidal areas and in
deeper waters. Not all caulerpa sites with soft or sandy substrates have experienced this
decline.
As well as Okupu and Waiheke Island, the team surveyed parts of Rangitawhiri/Tryphena
Harbour and Schooner Bay at Aotea. These results were more variable with some declines
in caulerpa cover but stil significant amounts on rocky reef substrate.
NIWA is now analysing samples taken during this research and reporting wil be finalised at
the end of June. Once received, this information wil be made available to the public.
You may be interested in an October 2024 summary of current known exotic caulerpa
locations, broken down by year and any removal treatments deployed. This can be found
here:
mpi.govt.nz/dmsdocument/65901-Summaries-of-known-exotic-caulerpa-locations-and-
Biosecurity-New-Zealand-funded-removal-trials-or-missions-October-2024
Note that since this summary was produced, exotic caulerpa has been detected at the
following additional locations: Paradise Bay on the western side of Urapukapuka Island, the
southern end of Motukiekie Island, and at Army Bay on Motorua Island in the Bay of Islands;
Repanga/Cuvier Island, between Aotea Great Barrier Island and Ahuahu Great Mercury
Island, Waikato; Square Top Island, off the tip of the Coromandel Peninsula, Waikato,
Hakaimango Point, Waiheke Island; Kaiaraara Bay, Aotea Great Barrier Island; and
Katherine Bay, Aotea Great Barrier Island.
Charles Fergusson Building, 38–42 Bowen Street
PO Box 2526
Wellington 6140, New Zealand
mpi.govt.nz
This latest information is recorded on a map on this page
: About exotic caulerpa and where
it's been found in NZ | NZ Government
•
I am not sure of how MPI monitors and reports on the Exotic Caulerpa incursion
However, if MPI does monthly reporting or monthly internal updates, can I please have
the ones produced since November.
MPI produces a newsletter that provides updates on the exotic caulerpa response. Further
information on the reduction in exotic caulerpa biomass can be found in the December 2024
and February 2025 editions. The newsletters can be found here:
mpi.govt.nz/biosecurity/exotic-pests-and-diseases-in-new-zealand/active-biosecurity-
responses-to-pests-and-diseases/exotic-caulerpa-seaweeds-caulerpa-brachypus-and-
caulerpa-parvifolia-in-new-zealand/exotic-caulerpa-newsletters/
Should you have any concerns with this response, I would encourage you to raise these with
the Ministry for Primary Industries at
[email address]. Alternatively, you
are advised of your right to also raise any concerns with the Office of the Ombudsman.
Contact details are: Office of the Ombudsman, PO Box 10152, Wellington 6143 or at
[email address].
Yours sincerely,
John Walsh
Director, Pest Management
2
