New rules to restrict boating, fishing to stop spread of pest seaweed off NZ’s Aotea Great Barrier Island

Biosecurity New Zealand is placing legal controls on parts of Aotea Great Barrier Island in a bid to contain the invasive seaweed Caulerpa brachypus, while the local Mana Whenua governance group on Aotea is supporting a dual response by imposing a rahui (restriction of access) over the same areas.

Caulerpa brachypus, which has been found in Blind Bay and Tryphena Harbour, is an Unwanted Organism under the Biosecurity Act and can spread rapidly and create dense mats.

John Walsh, Biosecurity New Zealand’s director readiness and response, said the seaweed can be spread to new locations by small fragments and is easily moved by people going about water activities like boating, and fishing, including dredging.

On Monday, September 20, Biosecurity New Zealand began issuing legal controls, known as a Controlled Area Notice (CAN), which will make it illegal to take seafood from Blind Bay or Tryphena Harbour. Anchoring in the the areas is also banned without a permit.

At the same time, a rahui will be imposed.

Martin Cleave (Ngati Wai representative), the deputy chair of the Governance Group for the biosecurity response, said the discovery of Caulerpa brachypus in Aotea waters, and the extent of the infestation, has been upsetting for mana whenua.

Under the CAN, it is illegal to remove any marine life (fish, seaweed, shellfish or crayfish) from the Controlled Area.

All equipment used for marine activities – for example, footwear, wetsuits, craypots, dredges, and boat trailers – cannot be removed from the controlled zones without first checking for seaweed and removing it, leaving it in the area it came from.

Importantly, anyone wanting to move a boat that has been anchored out of the two affected bays can only do so with a permit.

Mr Walsh said the controls aim to protect the island’s wider coastline while trying to not be too onerous for mana whenua and local people.

The CAN is in place until at least the end of November 2021.