Restrictions on boating and fishing to stop spread of pest seaweed in Aotea

From 20 September, Biosecurity New Zealand is placing legal controls on parts of Aotea Great Barrier in a bid to contain the invasive seaweed Caulerpa brachypus, while the local Mana Whenua governance group on Aotea are supporting a dual response by imposing a rāhui over the same areas.

The legal controls, known as a Controlled Area Notice (CAN), will make it illegal to take seafood from Blind Bay or Tryphena Harbour. Anchoring in the two areas is also banned without a permit. A rāhui will also be imposed.

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.

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

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, Biosecurity New Zealand said.

It 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.

“We’re working with our partners, the Mana Whenua governance group, and the local board to try to minimise this spread while we continue to assess where the pest seaweed is and what we can do in response,” said Biosecurity New Zealand’s director readiness and response, John Walsh.

Martin Cleave (Ngāti 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.

“After robust discussions with mana whenua, and leadership from Rangatira Hori Parata, this hard and realistic call was made.

“Aotea is a precious and unique environment, and we need to do everything to try and prevent this pest from spreading to other areas of our beautiful coastline. We urge people to comply with the rules.”

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

“People can still swim, dive, paddle, or use a vessel in the Controlled Areas, so long as they don’t drop anchor.

“It’s the movement of equipment along the seabed which poses the risk of picking up fragments of Caulerpa and moving it elsewhere.”

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

Maps of the controlled areas, permit application, and more information on Caulerpa brachypus can be found on MPI’s website.