What is exotic caulerpa?
There are many species of ‘Caulerpa’ seaweed, however an exotic (non-native) species smothers native flora and fauna, suffocates benthic communities, extinguishing their ability to survive where exotic caulerpa is growing.
Why is caulerpa a problem?
Professional divers have compared exotic caulerpa to astro-turf, as within a very short amount of time it can become very thick, matted and dense inhibiting anything else from growing.
When was caulerpa discovered in the Bay of Islands?
On 5 May 2023 a Hapu member was undertaking his regular after storm erosion checks at Omakiwi and noticed a seaweed that he had never seen before on any of our beaches . He collected a sample and sent it to Biosecurity NZ (BNZ) to have it tested. With a positive result for exotic caulerpa, the Ministry for Primary Industries (MPI) and Northland Regional Council (NRC) initiated action.
Why has a Controlled Area Notice (CAN) been implemented?
The Biosecurity Act 1993 mandates MPI to implement a CAN in any area where a biosecurity risk has occurred. The CAN relating to the exotic caulerpa outbreak was issued on 15 June 2023. You can read the Notice here: https://www.mpi.govt.nz/dmsdocument/57259-Te-Rawhiti-Exotic-Caulerpa-Controlled -Area-Notice-
What is a Rāhui?
A rahui is a prohibition of an activity which is put in place to protect a resource.
How did caulerpa get here?
Exotic caulerpa was first discovered in 2021 at Aotea, Great Barrier Island. It is believed that foreign ships may have unknowingly transported caulerpa from other areas of the world. The incursion was unexpected and not quickly contained. Therefore, smaller visiting boats may have carried fragments from Great Barrier Island to Omakiwi Bay, which is a very popular bay for sheltering in the Bay of Islands.
If caulerpa is allowed to spread, what are the anticipated outcomes?
Because of the speed at which caulerpa spreads (3cm per day upwards and outwards) and the aggressiveness of the spread, it is anticipated thatmarine life would be impacted in any areas where caulerpa is not eradicated or controlled. Such an impact would be catastrophic for our recreational, economic and biological futurity.
What is being done to eradicate or eliminate caulerpa?
In the Bay of Islands, Johnson Brothers engineering firm developed a technology to vacuum the seabed to remove caulerpa. Sand and other marine life do get caught up in the suction dredging, however initial trials have proved successful and divers continually monitor the dredged areas to determine the efficacy of this technology and report mitigation options.
What other technologies are being trialled?
Benthic matting, using chlorine tablets if necessary, deprives caulerpa of light and the chlorine can penetrate through the thin cell structure of the caulerpa so it dies. Salt trials have been trialed on Aotea, however it has been determined that the amount of salt required to kill caulerpa may be detrimental to the moana.
Why can’t we collect pipis from the bays not affected by Caulerpa, when we see people doing it now?
When there is a biosecurity threat identified in NZ a Controlled Area Notice and Rahui provide an opportunity for the situation to be assessed to ensure that any collection of seafood is safe. Small fragments of caulerpa may be present on any kaimoana that is harvested, if the shells are reinterred back to the sea, it can pose an opportunity for those small fragments to grow in other areas.
If Caulerpa spreads so fast and we can’t control it why can’t we go out on our boats and collect kaimoana and fish while we can?
A Rahui is not permanent, the non harvesting for a period of time allows us the opportunity to eliminate as much of the mass amount of caulerpa as we can, then continue to monitor
Aren’t boats more liable to spread Caulerpa with anchors and trailers taking boats out of the water etc. Why can’t we fish from the rocks and dive from rocks as we have done so all our lives?
We have undertaken lots of education on boat ramps making people aware of the rahui area and making sure they check their anchors and boats, trailers do not normally enter the affected waterways so they are not a concern. Fishing and diving from the rocks is prohibited due to the harvested kai potentially carrying fragments of caulerpa being spread to other areas.
Is it not better to fish and harvest kai while we can, because all the things I have read about the spread of Caulerpa tells me that you can’t stop it or eradicate it?
Caulerpa has been eradicated in some areas and if not eradicated it has been controlled with kaitiaki implementing safe practices. Some of the safe practices that work include keeping the caulerpa confined by restricting boat and fishing access to reduce the likelihood of transfer to other areas.
I want to take my children and mokos’ out and show them what my father and his father showed me when I was small, precious memories to pass on. Yet, are you telling me that you can eradicate it? Is this a certainty and if you don’t stop it you are taking the chance from me and mine a memory we could have before it is too late?
Every effort is being made to eradicate exotic caulerpa from Omakiwi Bay and stop it spreading to other parts of the Bay of Islands. It is not possible at this early stage to predict whether or not these efforts will be 100% successful, but as a community we have decided that we must make a strong effort to work together for the common cause of saving our Ipipiri from any further spread of this weed.
When I see so many boats, launches, scenic commercial boats out there spreading this weed and we the local people of this area are getting told “no, we need to try and save this for the future generations” we ask what chance do you think your group can stop it?
It is not possible for a small group to do this work alone. It takes a concerted effort by everyone to exercise our kaitiakitanga roles to help protect the moana during this time. When a foreign body has entered our shores is our responsibility to do everything we can to get rid of any unnatural intrusion that could potentially devastate our kai source
Climate change is happening worldwide the seas are getting warmer this Caulerpa thrives in warmer water can you stop Nature from thriving in this warmer environment, how do you stop Nature/evolution?
It is better for us to know that at least we tried than for us to sit back and do nothing. Whether climate change can be controlled by us or not should not determine our level of input into doing everything we can to eradicate it from our shores.