Biosecurity New Zealand, local mana whenua, and the Northland Regional Council are working together on next steps after divers searching the waters around Te Rāwhiti, the Bay of Islands, found a substantial amount of exotic Caulerpa seaweed, suggesting it’s likely been in the area for a number of seasons.
Biosecurity New Zealand and its partners have been responding to an earlier detection of what was believed to be exotic seaweed found washed up on a beach in the Omākiwi Cove area earlier in the month.
Biosecurity New Zealand’s deputy director-general Stuart Anderson says while the find of large areas of exotic Caulerpa is disappointing, it isn’t unexpected.
"Climate change, warmer temperatures and the ease of international movement will continue to present biosecurity challenges, but we’re committed to work through them with our partners, including local councils and mana whenua.
"We expect to have a controlled area notice (CAN) in place next week for a defined area around Omākiwi in the Bay of Islands, which will set restrictions and conditions. Local mana whenua may also put in place a Rāhui. The extent of the CAN will be further reviewed when delimiting surveillance in the area is completed by the end of next week, weather permitting.
"We have initiated a technical advisory group (TAG) to look at suction dredging which has had some recent success in controlling exotic Caulerpa in California and we’re also organising to send a small group of scientific experts and mana whenua to California to inspect attempts to remove exotic Caulerpa there."
Mr Anderson said dive work since the first clump of seaweed was identified in the Bay of Islands earlier this month had involved the Northland Regional Council and NIWA.
"Divers have been meticulously working through sites with suitable habitat and that are known anchorage points. The infestation found so far in Omākiwi Cove extends out into the Albert channel and varies in density from 90% coverage in sheltered areas to small sparse patches in the deeper waters, suggesting it’s been in the water for a number of seasons.
"I want to thank all those who attended a hui at Te Rāwhiti today. We had a good conversation and are committed to working together. I understand people’s concern, but international research and experience tells us that successfully eradicating Caulerpa is extremely challenging."
Mr Anderson said since exotic Caulerpa was first found at Aotea Great Barrier Island in July 2021, and then, later, at Ahuahu Great Mercury Island, a lot of work has been done in partnership with regional councils and mana whenua to minimise spread.
"That work includes a controlled area notice (CAN) that remains in place on 3 affected harbours at Great Barrier Island and bans some activities; Mana whenua putting in place a rāhui; extensive surveillance; testing a treatment option by smothering Caulerpa patches with salt; seeking expert international scientific advice about our options; and running ambassador programmes and an awareness campaign to ensure boaties and the public know what to do.
"We’ve spent about $2 million to date and acknowledge Caulerpa is difficult. It’s a further reminder, especially as climate change creates more biosecurity challenges, that we all have a role to play.
"People need to keep their boats and other equipment used in the waters clean to reduce the risk of introducing or spreading any exotic seaweeds. We’ll continue to back the work of councils and mana whenua in Northland and Great Barrier."
People can report suspected finds to Biosecurity New Zealand on 0800 809 966 or by completing the online reporting form at report.mpi.govt.nz .
Help stop the spread:
- Check your gear – anchors and chains especially. If you see any seaweed on your equipment, chuck it straight back.
- Know where Caulerpa is
- Know the rules about anchoring and fishing there
For more information email: BiosecurityNZ_media@mpi.govt.nz