Patches of the invasive seaweed Exotic Caulerpa have been located at three sites off the North-East coast of Te Hauturu-o-Toi (Little Barrier Island).

Nicola Rata-MacDonald, Chief Executive of the Ngāti Manuhiri Settlement Trust, says the discovery of caulerpa at Hauturu is yet another indication that Te Moananui-a-toi (the Hauraki Gulf) is under threat, and is in need of urgent restorative action.

"Hauturu is one of the most significant conservation areas in the world—New Zealand’s first ever nature reserve—and decisive action is needed to protect this taonga.” Nicola says.

“Today, our team marked the beginning of the Hauturu Rapid Response by laying a karakia over the area, and we will lead the attack on Caulerpa at Hauturu to eliminate this pest from our rohe moana.

“Our work with officials has shown that swift operational action is not hindered by a culturally informed response—it has been Ngāti Manuhiri pushing for action since this incursion was first discovered at Hauturu.”

Despite claims that Caulerpa cannot be eradicated, the Trust successfully removed an infestation at Omaha Cove in Leigh in June 2024—the first and only instance of this happening in New Zealand. Ms Rata-MacDonald says that time is of the essence to ensure a successful response.

“While the patch of caulerpa we managed to eradicate at Leigh was small, we were successful because we didn’t wait for it to spread and get out of hand.” Nicola says.

“Our kaitiaki responded immediately to treat the infestation, in partnership with Te Kaunihera o Tamaki Makaurau and supported by the University of Auckland, showing that if treated with the urgency that any biosecurity incursion deserves, we can get on top of this invasive pest.

“We cannot continue to treat caulerpa as a case study, it must be confronted with action which recognises the existential threat to our moana that it is. That’s what our team will be doing over the coming days.”

Recent comments from the Minister for Oceans and Fisheries confirming the Government will not take action to prevent bottom trawling in the Gulf has alarmed the Trust, who say that trawling will only help to spread exotic caulerpa further throughout the Gulf.

“Almost three-quarters of the Hauraki Gulf is open to bottom trawling and Danish seining - a destructive fishing method where weighted nets are dragged along the seafloor, ripping up everything in their path.” Nicola says.

“Caulerpa is already spreading throughout the Gulf, and allowing bottom trawling to continue only increases the risk of fragmentation and further spreading of this invasive seaweed.

“We are under siege from this pest, and rather than committing the investment needed to remove and eliminate exotic caulerpa, the Minister has confirmed the Government will only make it easier to destroy our benthic habitats, whether with nets or with weeds.

“We’re calling on the Government to protect the Gulf by banning bottom trawling, investing in the eradication of exotic caulerpa, and urgently progressing the Hauraki Gulf / Tīkapa Moana Marine Protection Bill—without amendment—to ensure we can restore the waiora and mauri of the Gulf.”

NOTES:

Exotic Caulerpa was first detected at Hauturu on 6 May 2025 at the following sites:

Site 1 - The Queen South (-36.1727, 175.1082)

Site 2 - Waimaomao Bay (-36.1677, 175.0968)

Site 3 - Waimaomao Bay (-36.1693451, 175.0952474)

About Ngāti Manuhiri Settlement Trust

Ngāti Manuhiri Settlement Trust is the post settlement governance entity (PSGE) responsible for representing the Ngāti Manuhiri hapū and iwi members, giving effect to the Ngāti Manuhiri Claims Settlement Act 2012. Established in 2011, the Trust is committed to ensuring a prosperous future for Ngāti Manuhiri whānau.

Our rohe, moana, and interests are across Te Moananui-ā-Toi including the inner and outer islands and rocky outcrops from Aotea, to Te Paepae o Tu, to Hauturu, and Takapuna. Te Moananui-ā-Toi is the greater oceans encompassing the Hauraki Gulf and Hauraki marine park and so, we refer to the Hauraki Gulf / Tīkapa Moana as Te Moananui-ā-Toi.

The Trust’s work centres on the protection of the taiao, reinvigoration of community purpose and service, maintenance of cultural integrity and investing to support the economic prosperity of future generations. More information on Ngāti Manuhiri Settlement Trust can be found at www.ngatimanuhiri.iwi.nz.

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