Boaties heading out on the water this summer are being urged to take extra care to prevent the spread of exotic caulerpa—a highly invasive marine pest that threatens to wreak havoc on our marine ecosystems and recreational waters.

Auckland Council, in partnership with the Ministry for Primary Industries (MPI), iwi, and neighbouring regions, is ramping up efforts to contain the spread of this marine pest across the Hauraki Gulf, Bay of Islands, Coromandel, and beyond.

Mayor Wayne Brown says he’ll be out on the water again this summer and remaining vigilant around caulerpa.

“Last season, before I went to Great Barrier, I arranged a mooring to ensure my anchoring actions did not spread this pest,” he says.

“It is good to see reminders going out to boaties – now it’s up to us to make sure we help prevent the spread of this nasty weed and protect our treasured marine environments for everyone.”

Chair of Auckland Council’s Policy and Planning Committee, Councillor Richard Hills, emphasises the importance of boaties playing their part in stopping the spread.

"We all love enjoying the stunning waters of the Hauraki Gulf and our neighbouring coastal areas, but we must remember that exotic caulerpa poses a serious threat to these ecosystems,” says Councillor Hills.

“We must do all we can to reduce the spread. Anchoring in infested areas can easily disturb this pest, allowing it to spread further."

"This is not just about following rules; it's about protecting the places we love to visit, fish, and play. If we don't act responsibly, we risk losing access to some of our most treasured marine environments.

Auckland Council’s Team Manager Pathways, Liz Brooks, says containment is currently our best strategy.

“This is a collective effort. We need people to remember that every action can make a difference, and we need everyone’s help to stop caulerpa from spreading."

Why is exotic caulerpa a problem?

Exotic caulerpa (Caulerpa brachypus and Caulerpa parvifolia) is a fast-spreading marine algae that blankets the seafloor, outcompeting native seaweeds and seagrass. This disrupts vital marine habitats for fish, shellfish, and other marine life, leading to a decline in biodiversity and threatening the recreational fishing and diving opportunities New Zealanders cherish.

Where is it found?

Currently, exotic caulerpa is found in several key areas:

Hauraki Gulf: Kawau Island, Waiheke Island (Onetangi Bay/Thompson Point), Rakino Island, Aotea/Great Barrier Island, and Mokohinau Islands.

Other areas (outside Auckland): Bay of Islands, Coromandel (Fantail Bay and Great Mercury Island/Ahuahu).

Check the Community Viewer for the latest information on infested areas or use this link to see where exotic Caulerpa has been found in the Auckland region and details on the rules and restrictions in place.

Controlled Area Notices (CANs) are already in place at Aotea/Great Barrier Island, Ahuahu Great Mercury and the Bay of Islands, and a CAN comes into effect around Waiheke Island at midnight allowing boats to anchor but boaties must check and clean anchors and chains after doing so. No fishing that disturbs the sea floor is permitted.

What can you do?

Boaties, fishers, and beachgoers can all help slow the spread of exotic caulerpa.

• Avoid anchoring or disturbing the sea floor in infested areas: anchors and chains can fragment caulerpa, causing it to spread to new locations.

• Check and clean gear: clean anchors, fishing gear, dive equipment, and any other gear when moving between regions.

• If you find it, bag it and bin it. If you can’t do this, return it to where it came from; do not move it to a new location.

Report sightings:

If you see any unusual seaweed, take a photo, record the location, and report it to MPI on 0800 80 99 66.

Respect Controlled Area Notices:

CANs are in place to protect vulnerable marine environments. Make sure you know where you can safely anchor and fish before heading out.

What’s at stake?

Failure to contain exotic caulerpa could have devastating consequences:

• loss of recreational areas: infested areas may be off-limits for anchoring, fishing, and diving

• marine biodiversity: the loss of native marine habitats affects fish populations and overall marine health

• interregional spread: the pest could spread further south to regions like the Bay of Plenty and East Cape, significantly expanding the containment challenge.

"Removing large-scale caulerpa infestations is currently not feasible. Although we are leaning on research and development for solutions, prevention is the only viable solution right now,” explains Councillor Hills.

“This summer, we’re working hard with MPI, iwi, and communities to develop new tools, trial new techniques, and provide alternative mooring options. But we need everyone’s cooperation to protect our waters."

Summer ambassadors on hand

Throughout the summer, ambassadors will be stationed at boat ramps and marinas to provide information and answer questions. Boaties are encouraged to engage with them and learn how to play their part in protecting New Zealand’s marine environment.

For more information, visit the MPI website

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