An adult red rock lobster, aka ‘crayfish’ or ‘kōura’ (Credit: John McKoy, NIWA)
Introduction
AGBET is a registered charitable trust whose mission is to “Work with Aotea’s mana whenua and community to protect biodiversity, re-introduce lost species, eradicate rats and feral cats, and grow a sustainable, ecology-based economy.”
AGBET has an extensive history of advocating for protection of the terrestrial and marine environment at Aotea Great Barrier Island.
A core underlying value of AGBET is to use robust evidence-based data in our assessment of the state of the environment and in our advocacy for ecosystem restoration and protection.
Accurate stock estimates of rock lobster / kōura populations within CRA2 is critical for sustainable management of this fishery. The recommendations in this review are predicated on a methodology used by Fisheries NZ that estimates there has been a dramatic recovery in kõura stock since the total allowable catch (TAC) was reduced in 2018. That conclusion is based on a modelling methodology that estimates the catch per unit effort (CPUE) based on biomass of kōura per potlift. This may not reflect actual abundance.
Independent studies based on diver-based surveys that compare stock in marine protection areas (MPA) versus fished locations conclude that the Fisheries NZ modelling approach severely overestimates recovery of kōura stock within CRA2. Qualitative observations by environmental organisations and recreational divers across the Hauraki Gulf support this conclusion.
Background: The Hauraki Gulf
The Hauraki Gulf / Tīkapa Moana is a taonga for Aotearoa, distinguished by its unique features and values. It is of significant historical and cultural importance for tangata whenua. With around 2 million people living on the shores of the Gulf it is one of the most heavily utilized marine areas in New Zealand. It is the seabird capital of the world and home to a resident population of tohorā / Bryde’s whale.
But climate change and human activity – on both land and sea - have taken a heavy toll on the health of the Gulf, which is currently described as on the edge of ‘ecological collapse’ with declining water quality, habitat loss and overfishing, , The kelp forests that sustain fish stocks and biodiversity within the Gulf are in serious decline, principally through kina predation, , and that has a huge flow on effect on the marine life within the Gulf. The collapse of seabird populations within the Gulf are one of the best indicators of the poor ecological state of health of the Gulf.
It is against this background that we have reviewed the Discussion Paper on proposed options around the future harvest of rock lobster / Kōura papatea (Jasus edwardsii) within CRA2, noting that the Hauraki Gulf is a significant component of this fishery.
In particular, our focus is on the implications of the management options proposed and how they might impact on the ecological health of the coastal waters around Aotea / Great Barrier island.
Proposed biomass management targets
Of the options proposed in this review AGBET supports a management biomass target greater than 3.5x BR (where BR is the Biomass reference target).
We have opted for this target rather than the Fisheries NZ preferred option of 2.5x BR because:
Independent studies involving diver-based surveys question the accuracy of the methodology used by Fisheries NZ in estimating kōura stock within CRA2.
The Fisheries NZ modelling methodology estimates catch per unit effort (CPUE) based on biomass of kōura per potlift. No independent ‘in ocean’ methodology is used to support the accuracy of this modelling approach. It is not possible to make ecological inferences using fishery-dependent data alone.
The independent studies compare stock in 3 marine protection areas (MPA) versus 6 fished areas across the Hauraki Gulf and conclude that the Fisheries NZ modelling approach severely overestimates recovery of kōura stock within CRA2.
They found that the biomass at fished locations was <10% of that in reserves and there was little evidence for stock recovery within CRA2 since the catch reductions made in 2018. These diver directed surveys allow a direct comparison of number, size and biomass of individual kōura at fished and unfished sites and take into account the highly variable ocean dynamics.
Qualitative diver-based observations by marine environmental organisations and recreational divers across the Hauraki Gulf do not support the conclusion by Fisheries NZ that there has been a dramatic recovery in the kōura stock.
Total allowable catch (TAC) options
AGBET supports Option A1: retention of the current settings. We prefer this option as
there is considerable uncertainty as to whether there has really been a recovery of the fishery stock since the adjusted take was reduced in 2018.
Independent diver-based surveys (see above) do not support a recovery of the magnitude proposed in this paper.
The consequences of closure of the inner Hauraki Gulf to both commercial and recreational rock lobster harvest will change the impacts on the remainder of the CRA2 fishery. Retention of the current settings may have considerably greater impact on the areas outside the inner Gulf than are already occurring.
If the Hauraki Gulf / Tīkapa Moana Marine Protection Bill is passed 12 additional High Protection Areas (HPAs) will be added to the current 8 marine reserves within CRA2 where there is a policy of no-take.
It is a high-risk strategy to increase the take while also making major adjustments to the areas from which commercial and recreational kõura harvest can occur.
Proposed spatial management measures
AGBET supports option B2 of closing the inner Hauraki Gulf to all commercial and recreational rock lobster fishing.
We support this option as rock lobster within the inner Gulf are close to being functionally extinct. It is an indictment of the previous CRA2 management measures that this part of the Gulf is now in such a dire state. Iwi have become so concerned they have taken independent action as exemplified by the successful Ngāti Paoa application for a section 186A temporary closure around Waiheke Island. The very small populations of rock lobster within the inner Gulf now make commercial rock lobster fishing within this area unviable.
The status quo (option B1) is not acceptable as it will allow ongoing recreational harvest, further depleting already low stocks and lead to total collapse of the population in this area.
However, closure of the inner Gulf, combined with a proposed increase in the total available commercial catch (TACC), will lead to huge pressure on the outer Gulf, and in particular at Aotea.
Pressure on Aotea coastline
Besides the potential impact of commercial fishing, the impact of recreational fishing on rock lobster around Aotea is also likely to increase.
It is estimated that there are over 100,000 recreational vessels in and around Auckland. While only a fraction of these boats come out to Aotea, the number of vessels visiting the island, especially over summer is still in the thousands, and many of these engage in fishing activities. Charter boats with divers add to that pressure, and can quickly result in depletion of kōura and other fish stocks from popular dive locations.
Surveillance and enforcement of fishing regulations at Aotea by Fisheries NZ is sporadic at best.
While kōura stock did recover a little in Tryphena, Okupe and Whangaparapara harbours when anchoring bans were imposed as part of the conditions of the controlled area notices (CAN) set up across this section of the west coast of Aotea following the identification of the highly invasive exotic seaweed, caulerpa (C. brachypus and C. parvifolia) in July 2021, that increase was short lived. Once the ban on diving was lifted when the CAN was renewed in November 2023, stocks of rock lobster decreased rapidly from the pressure of recreational divers.
The issuing of permits for crayfishing at Aotea, including within the CAN, in 2023, added further pressure on the rock lobster stocks at Aotea.
It is important to recognize that tangata whenua and the community of Aotea rely on the moana as a source of kai.
Therefore, management of the rock lobster stocks on Aotea must take into account the needs of the local community and place their rights ahead of those of visitors from off the island who fish on a recreational basis and are not dependent on the moana for kai.
The Ahu Moana Vision
AGBET strongly supports a vision of community management of local marine ecosystems.
This is possible without legislative change through section 11 of the Fisheries Act (1993).
We support an island led management structure as captured by the vision of the Ahu Moana pilot. This is a concept that was developed as part of the Sea Change Tai Timu Tai Pari / Hauraki Gulf Marine Spatial Plan in 2017, and is one of the core elements of the Government’s 2021 ‘Revitalise the Gulf Strategy’.
Ahu Moana, which sits within the Pou Moana of Ngāti Rehu Ngātiwai Ko Aotea Trust, has now been operating for three years (since October 2022) providing a model for mana whenua and community working together to observe, record and better understand the local ocean ecosystems. The regular surveys by Ahu Moana, using hauora moana methodology, provide a continuous record of the dynamics of the local ocean ecosystems, which is a richer and more comprehensive record of what is going on in the ocean than assessing stock using models based on catch data.
Conclusion
We support closure of the inner Hauraki Gulf to both commercial and recreational fishing for kōura but in doing so highlight the likely flow on negative effects, and the impact they will have on the ecological health of the Aotea fishery. To mitigate those effects we recommend the establishment of a local management model for Aotea that incorporates the vision of the Ahu Moana pilot. Such an approach will not require a legislative change.
We are seriously concerned at the potential flaws in the model used by Fisheries NZ to estimate current and future rock lobster stock within CRA2 and the uncertainty that generates in the quality of the recommendations made within this report.
We therefore recommend a conservative management approach that in the short term prevents a further decline of the ecological health within CRA2 and in the longer term allows the Gulf to ‘heal’ to ensure future generations enjoy both the ecological and economic benefits.