Suction dredge to combat exotic caulerpa on Aotea Great Barrier and Kawau islands

Publish Date : 10 May 2024
Rocky coastline

As part of MPI’s accelerated caulerpa response programme, Auckland Council is enhancing its biosecurity response in the Hauraki Gulf. This includes the Aotea perimeter management project on Aotea Great Barrier Island.

This project will involve a suction dredge operation to protect the perimeter of Port Fitzroy and Katherine Bay by removing caulerpa at:

  • Man of War Passage (Governor Pass)
  • Motuhaku / Port Abercrombie
  • Ahuriri Point.

These three areas were chosen by the Aotea Caulerpa Governance Group because Port Fitzroy is a key anchorage and Katherine Bay is an area of particular  cultural significance.

Survey work (funded by the council, MPI and the Aotea/Great Barrier Local Board) has been undertaken to determine caulerpa locations in these three areas.

The suction dredge operation supplier has been commissioned and will commence in May with planning already well underway.

“It’s really great news that suction dredging will take place in these areas where growth has not yet got a strong foothold,” says Aotea / Great Barrier Local Board Deputy Chair, Chris Ollivier.
“By removing caulerpa from these locations, we can slow the spread. It’s still important to continue to report new sightings and follow the ‘bag it and bin it’ advice.”

Removal work underway at Iris Shoal, Kawau Island

MPI, NIWA and Bay Underwater, working closely with Ngāti Manuhiri, are currently using hand-held suction dredges to remove exotic caulerpa from an area of Iris Shoal near Kawau Island.

The caulerpa is sparsely spread in the area but it is situated in a difficult marine environment with changing depths, tides and currents.

The work started on 26 April and is expected to finish on 12 May, when the team expects to have cleared an area of over 10,000 square metres. The project will provide good information about the use of the diver-controlled suction technique in this kind of environment.

What should I do if I find exotic caulerpa?

If you bring it up (on your anchor or hook), bag it and bin it! This means securing it safely on board in a bag or container, and binning it (by disposing of it safely, away from the water, for instance in your household rubbish bin or compost).

If you find it on the beach, pin, pic, and phone. That is – note the location, take a photo, and report on 0800 80 99 66 or at

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