Divers counting Pāua near the entrance of Tory Channel have learned to look for one small detail: a patch of pale turquoise near the tip of the back of the shell.
That colour comes from the lack of direct sunlight young Pāua receive in a hatchery. Once a juvenile is released and starts being exposed to outside solar radiation, the shell it grows from then on is darker. The familiar colour of a wild Pāua of the Channel. But the blue tip stays behind for several years as a record of where that animal started life, an important marker in the process of recording the results of reseeding.
Counting those blue tips, along with DNA testing and several years of dive surveys, has let researchers test a question that matters to anyone who cares about Pāua in the Marlborough Sounds. When hatchery-raised juveniles are put back in the ocean, do they make a real difference?
Two recent studies, both connected to the hatchery at Arapawa Seafarms, suggest the answer is yes. They are equally clear about what it costs, and that part of the story matters just as much.
Table of contents
Why put Pāua back at all?
Blackfoot pāua (Haliotis iris) lives only in New Zealand. Abalone fisheries elsewhere around the world have collapsed, including California’s in 2017 (with decades of decline beforehand that wasn’t stopped by any meaningful or effective efforts). And researchers now describe New Zealand’s as one of the last wild abalone fisheries left.
Around the top of the South Island, the fishery known as PAU7 has had a difficult decade. The commercial catch limit was halved in 2017, stripping many small and large players of their catch rights in a fishery that began with over 200 tons of quota allocated in the 1980s.
In 2023 the industry voluntarily set aside, or “shelved”, a further half of what it was still allowed to take. Causes include fishing pressure (including poaching), changing water biomes, marine heatwaves, and sediment washing off land onto shallow-water reefs.
A 2024 inspection of the fishery by abalone scientist Dr Jeremy Prince found large areas of reef that look like good Pāua habitat but no longer hold Pāua. Commercial divers describe the same thing. They now travel further and search harder to find a day’s catch along coast they once worked end to end. The only way to ease pressure on the remaining beds is to cut the quota further, as the current catch rate is unsustainable and driven in part by a mix of commercial, customary, and recreational take. This is especially true when the take is under the size limit voluntarily implemented by commercial divers (132mm), or under the size limits implemented by the Ministry for Primary Industries (125mm).
When adult Pāua are too few or too scattered to breed well, or when the shallow boulder reefs where juveniles grow up are degraded, a ‘bed’ (a group of Pāua) can struggle to replace itself. But reseeding tries to bridge that gap. A hatchery raises juveniles through their most vulnerable early months, then moves them into nursery habitat in the foreshore/intertidal zone, which can significantly increase their survival to adulthood.
The Tory Channel trial
PāuaMAC7, the commercial management group for PAU7, released just over 159,000 hatchery-reared juveniles near the entrance of Tory Channel: about 99,100 in April 2012 and around 60,000 in 2014. They came from locally collected wild parents and had been raised for about nine months, to around 10mm long.
Divers placed them by hand. The juveniles clung to old Pāua shells, which the divers tucked into gaps between boulders 0.5 to 1 metre deep along roughly 2 km of shoreline. Two nearby stretches of coast were left untouched as controls.
From 2013 to 2017, divers swam the same GPS-marked transects every year and measured every Pāua they found. Dr Tom McCowan’s September 2025 report on the programme sets out the results.
On the reseeded coast, the average weight of Pāua per transect rose by 21%, from about 1,090g to 1,327g. On the control reefs, it roughly halved, from 795 g to 398g.
A clear wave of new Pāua also moved through the reseeded area. In 2015, there were more Pāua in the 60 to 100 mm range. In 2016 and 2017, the peak shifted to 100 to 130 mm as they grew. The control reefs showed no such pulse.
In 2016, divers sampled 146 Pāua from the reseeded coast. Using the blue tip and DNA parentage testing together, researchers estimated that about half had come from the hatchery. A separate genetic analysis found three distinct groups in the area, consistent with the wild population plus the 2012 and 2014 releases.
The report is careful about what this proves. Pāua live in clumps, so transect counts vary a lot, and a trial of this size can’t account for everything that happens on a reef. Its own conclusion is measured: at the very least, reseeding held Pāua numbers steady on a stretch of coast while untreated reefs nearby declined.
One detail suggests the hatchery contribution may be larger than estimated. DNA testing identified some hatchery Pāua that had no visible blue tip, so counts based on appearance alone probably miss some.
After the earthquake: the Kaikōura test
The 2016 Kaikōura earthquake lifted parts of the coastline by up to 6.4 metres. It killed large numbers of Pāua and stranded the shallow reefs where juveniles live, leaving them out of the water to perish quickly, along with other sea creatures, in the heat of the following days. This wiped out the most productive broodstock, along with subsequent generations that would have been recruited into the biomass (the growing population) over the following years.
The entire affected coastline had much of that important population liquidated as the land lifted upward by up to 6 metres.
In 2018 the Kaikōura commercial pāua group, PauMAC3, released 167,000 hatchery-reared juveniles along the earthquake-affected coast and at one site near Akaroa. Arapawa Seafarms produced the juveniles from wild Kaikōura parents and raised them for nine months. Shawn Gerrity and Professor David Schiel of the University of Canterbury followed them for four years, and published their results in the New Zealand Journal of Marine and Freshwater Research.
A year after release, 18% of the Pāua counted at the survey sites were hatchery-raised. Three years on, the figure was 11.8%. It held up even though an unexpectedly strong natural spawning had flooded the same reefs with wild juveniles in the meantime.
The hatchery Pāua grew fast: about 36 mm in their first year, and around 25 mm a year on average over three years. That is about the same rate as wild pāua in the region.
The most significant finding was that by 2021, 96% of the hatchery Pāua recaptured at the Kaikōura sites were longer than 82 mm. That is the size at which half of the region’s Pāua are expected to be mature. The researchers concluded that more than half had probably reached breeding age. In other words, the released Pāua were likely spawning and contributing to the next generation themselves, growing that biomass and creating juveniles that would not have existed without their presence.
The choice of site made a large difference. Two juveniles released at the same size, 12.5 mm, were later found at very different sizes: 35 mm at Akaroa and 100 mm at Omihi. At Waipapa, a site seeded in 2020, a severe storm buried the reef in gravel by 2023. Divers found only empty shells. The lesson the researchers draw is to choose sites carefully and spread releases across several locations.
Experiments closer to home
Raising juveniles for nine months is expensive because of labour costs and the need for consistent monitoring, so the Kaikōura programme also tested cheaper methods. Much of that work took place in the Sounds.
The first step was getting Pāua to spawn in captivity, and that alone took nearly two years and more than 40 attempts at the Arapawa Seafarms hatchery. Biosecurity rules meant the larvae couldn’t be taken to Kaikōura. The trials therefore ran at Okukari, a two-minute trip from the hatchery.
The researchers tried three approaches:
* Pouring swimming larvae straight onto the reef. This had no detectable effect. About 100,000 larvae released along a 50 m transect produced seven small Pāua when the site was checked around five and a half months later.* Holding larvae over small plots under mesh “tents” for 24 hours. A few more Pāua settled: eleven, from 45,000 larvae.* Settling larvae onto rocks in hatchery tanks, then placing the rocks on the reef. This was the most promising. After about four months, these plots held around 10 small Pāua per square metre. Plots of cleaned rocks without larvae held a single small Pāua across all four.*
The pre-settled rock method is also far cheaper. The researchers estimated it at around $90 per thousand, compared with about $800 per thousand for nine-month-old juveniles. It is an early result from a single site, pointing in a possibly useful direction, but shows there are many ways that the process can be done with improvements on location and techniques that may increase survival rate with further trials to refine the process.
Some larvae from the same spawning were also settled into tanks set aside for Pāua pearl work, a reminder that restoration and pearl cultivation at Arapawa draw on the same hatchery skills. And that the natural spawning of the Paua in the tanks means that the farm provides an already present source of larve during normal operations, as baby Paua have been found in the pipes and tanks simply from natural spawning.
The part that doesn’t add up yet
Both studies are candid about the money.
In Tory Channel, the report estimates that 3.1% to 4.3% of the 2012 juveniles survived to more than 90 mm. That falls within the range found in earlier Marlborough trials, 1.3% to 18.6%, but at the low end. The 2012 release cost about $41,640. The report’s modelling suggests the eventual commercial catch from those Pāua would leave a shortfall of more than $25,000.
The Kaikōura release cost about $136,000. To recover that through commercial catch alone, roughly 6.8% of the released Pāua (or their offspring) would need to reach harvest size, which takes six to eight years. They are not a fast-maturing species and need time to grow.
A further complication is who gets the Pāua first. Commercial divers often work to a larger minimum size than the recreational limit of 125 mm. On easily reached coastlines, hatchery Pāua can therefore be taken by recreational divers, under customary permits or by poachers well before they reach commercial size. The commercial industry has so far paid for reseeding, but every sector harvests the results.
Under current methods, then, reseeding is not a straightforward commercial investment. Both reports say so directly.
Measuring the right thing
Both reports also argue that breaking even is an incomplete way to judge reseeding.
McCowan describes reseeding as insurance: a way to hold the line on parts of the fishery that are declining, and to reduce the risk of further catch cuts. Gerrity and Schiel point to outcomes that are harder to price but still valuable. These include re-establishing a breeding population on depleted reefs, supporting recovery during a rāhui (a temporary customary closure), and building community understanding and stewardship.
The most promising use may be targeted, with Prince’s observation of empty reefs suggesting reseeding could focus on habitat that no longer holds Pāua, especially shallow nursery reef (juvenile habitats) connected to the deeper reef where adults live and spawn. Releases would work best alongside measures that protect the recovering Pāua, such as larger harvest sizes, seasonal closures and action on poaching.
Both studies add a caution. Reseeding is not a substitute for good fishery management, and protecting the Pāua that are already breeding comes first. But relying on the remaining numbers to repopulate without human intervention through reseeding, we feel, is not an effective practice and would hamper recovery.
Who should pay for reseeding?
McCowan’s report makes a specific proposal. PAU7 currently has a commercial catch limit of 93 tonnes, alongside allowances of 15 tonnes each for recreational and customary fishing. Because the benefits of reseeding are shared, the report suggests that industry funding be matched by roughly a quarter of the cost from government or other sectors, in line with the non-commercial share of the fishery.
The research also suggests where future funding would make the most difference:
Developing cheaper methods such as pre-settled rock.
Choosing sites based on habitat, food and existing Pāua numbers.
Keeping DNA samples from every set of hatchery parents so results can be traced (tissue from the 2012 Tory Channel parents wasn’t kept, which limited what the trial could show).
Pairing releases with protection for the reefs they go into
From where we sit, the evidence justifies continuing this work and sharing the cost of it.
What you can do
If you gather Pāua youself, stick to the size and bag limits. They give released and wild Pāua the chance to breed before they’re taken. Use blunt edged tools to remove them from rocks with a smooth but quick motion, so you’re not causing injury with prying them or cutting them in the removal process. Doing either of these things will kill the Pāua due to them being haemophiliacs and stress sensitivities.
If you see Pāua being taken illegally, report it to MPI on 0800 4 POACHER.
And if you find a Pāua shell on the Sounds coast with a pale blue patch near its tip, you’re probably holding one that started life in a hatchery tank.
Summary
Hatchery-raised pāua released into Tory Channel and along the Kaikōura coast have been tracked by divers for several years, and the results are encouraging. On reseeded reef in Tory Channel, pāua biomass rose 21% while nearby untreated reefs halved. At Kaikōura, most released pāua grew at wild rates and had likely reached breeding size within three years. Neither programme recovered its cost through commercial catch, which is the real obstacle. This article sets out what the research found, why cheaper methods such as pre-settled rock matter, and why the cost of reseeding should be shared across the sectors that benefit.
The Author: Jacob Radon
Jacob grew up on Arapaoa Island, surrounded by the lifestyle and aquaculture of his parents. From an early age, the rhythms of the island shaped the way he sees the world — the tides, the water, the quiet patience that good farming demands. He loves pāua and has a deep interest in understanding their biology, behaviour, and how best to optimise their growth. That curiosity, rooted in a childhood spent close to the ocean, is what makes Jacob such a natural and passionate part of the Arapawa Blue Pearls team.
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Frequently Asked Questions
What is Pāua reseeding?
Reseeding means raising young Pāua in a hatchery, usually for about nine months, and then placing them by hand into shallow boulder reef where wild juveniles would normally live.
How can you tell a hatchery Pāua from a wild one?
Hatchery Pāua usually have a pale blue patch near the tip of the shell, which comes from their hatchery diet. It fades after a few years as the shell becomes encrusted, so researchers also use DNA parentage testing.
Does Pāua reseeding work?
In Tory Channel and Kaikōura, reseeding added measurable numbers of Pāua to the reefs, and many released Pāua reached breeding size. Under current methods, though, it does not recover its costs through commercial catch.
Do hatchery Pāua grow as well as wild Pāua?
At most Kaikōura sites, yes. They averaged about 25 mm a year over three years, similar to wild Pāua in the region. Growth varied a lot between sites.
