Caulerpa Seaweed Detected Near Kawau Island

Information from Biosecurity New Zealand about the detection of exotic caulerpa seaweed near Kawau Island

You may have heard that in early July, the invasive pest seaweed exotic caulerpa was detected in small patches in an area of the Iris Shoal in the North Channel off Kawau Island.

This seaweed was first found at Aotea Great Barrier Island in 2021, and subsequently at Ahuahu Great Mercury Island and in Te Rāwhiti Inlet in the Bay of Islands.

For the past two years, Biosecurity New Zealand has been working with partners, including mana whenua, local authorities and communities to address exotic caulerpa at these locations. This has been a sustained, through and collaborative effort to contain caulerpa to the known locations, better understand the pest and its challenges, trialing treatments, and working to prevent its spread.

Work has included placing legal controls on risk activities (including fishing and anchoring) and widespread campaigns involving local communities, mana whenua, regional councils and others to educate people about Caulerpa. Since its discovery near Kawau Island, Biosecurity New Zealand has held discussions with Ngāti Manuhiri and Auckland Council and is planning the most appropriate actions in response to the emerging situation.

Ngati Manuhiri is partnering with MPI to combat the spread Te Wero Nui | Ngāti Manuhiri Settlement Trust (ngatimanuhiri.iwi.nz)

Local people can help in this work by noting the following actions:

  • If you believe you have seen exotic Caulerpa (either in the water, or washed up on the beach – see photo - take a photo if you can, note its location and report it – Phone 0800 80 99 66 or online at https://report.mpi.govt.nz/pest/

  • Try to avoid anchoring and fishing in the area of Iris Shoal. When anchoring around the island, before moving to another location, check your anchor and chain and remove any seaweed. Throw it back in the area it came from.

Full information about exotic Caulerpa is at: www.biosecurity.govt.nz/caulerpa. Should you need further information, please do not hesitate to contact Biosecrity or Ngāti Manuhiri

Download the full PDF map and details here