Situated 10 minutes drive along the waterfront from Auckland’s CBD is Ōkahu Bay. Looking out across the Waitematā towards Rangitoto there was once a carpet of kūtai / mussels forming extensive reefs in the Rangitoto channel. Working in partnership with Ngāti Whātua Ōrākei, the Revive Our Gulf project is working to establish kūtai beds and restore the mauri / life force of Ōkahu Bay.
For Ngāti Whātua Ōrākei, this work has been multigenerational, and follows a vision for Ōkahu Bay laid down almost 10-years ago in the Ngāti Whātua Ōrākei long-term ecological restoration plan:
“Waters fit to swim in at all times, with thriving marine eco-systems that provide sustainable kaimoana resources to a Ngāti Whātua Ōrākei community who have strong daily presence in and on the bay as users and kaitiaki”.
Ngāti Whātua Ōrākei long-term ecological restoration plan (Kahui-McConnell 2012)
We hope to see Ōkahu Bay become a ‘living laboratory’ where others can come and learn about kūtai reef restoration and help to turn our big blue backyard back into a place that is once again filled with abundance.
🌊🌧⛈ Our intrepid Trustee diver finds mussel beds intact after flood and cyclone!
This week, Shaun Lee took the plunge and explored the mussel beds at Ōkahu Bay for the first time since the 27 January flood and Cyclone Gabrielle. Shaun observed clumps of mussels stretched out over the seafloor in a similar density and pattern as his last dive in December, with no observable losses from weather events. He dived over the mussels placed on a shell base and we`ll be interested to see if there are any marked differences at our next formal monitoring between the shell-base beds and the soft sediment beds.
Ngā mihi Shaun Lee for the observational dive!
📷 Shaun Lee
#shellfishrestoration #shellfishrestnz #HaurakiGulf #kūtaiōkahu
The recent storms have left their mark on the Hauraki Gulf / Tīkapa Moana /Te Moananui ā Toi. Although we’ve not yet been able to assess the impacts on the mussel restoration sites, we remain committed to the revitalisation of the Gulf and its ecosystems. We appreciate all the support we`ve received and look forward to working together on the other side of this storm in our efforts to re-mussel the Gulf. We’re hoping to have eyes on the restoration sites soon and we`ll be back in touch to let you know how they are. Kia haumaru te noho (stay safe everyone).
📷 Manuel Greenland
#haurakigulf #shellfishrestoration #kūtaiōkahu #teauomorunga #shellfishrestnz
Last week Shaun Lee dived at Ōkahu Bay to check on the mussel reefs. The settled weather meant that visibility was good, and he captured these stunning photos. Shaun was chuffed to see the amount of wildlife that had moved into the restoration area. It shows that even in degraded sites, with help, the seafloor will try to heal itself. We’ll continue to learn lots from this site.
@[17841442116032401:@shaunswildlife]
#haurakigulf
#kūtaiōkahu
#shellfishrestoration
The results of our 12-month monitoring of the mussels at Ōkahu Bay are in. Although early days, these reefs provide a valuable test case for learning and knowledge building. Read more here…
https://buff.ly/3ja6OgJ
#kūtaiōkahu #shellfishrestoration #haurakigulf #reviveourgulf
Weather delayed our 6-month monitoring of Ōkahu Bay, but results now out… Beginning to see a marked difference in survival of the kūtai on shell (S1..S3) 😀 vs, those on bare sediment (M1..M3) 😫. A few more 11-arm starfish moving in and the water looking a bit clearer this time. Getting interesting!
#kūtaiōkahu #shellfishrestoration #haurakigulfregeneration #haurakigulf
6-month monitoring at Ōkahu Bay underway. Watch this space for an update on how the mussel beds doing.
#kūtaiokahu #shellfishrestoration #haurakigulfregeneration #haurakigulf
Check out these amazing images of two of the Ōkahu Bay kūtai (mussel) beds. Constructed from a whole series of images stitched together as an orthomosaic. Only 30-40cm of visibility at the time – but you wouldn’t know that from the results. Can you spot the 11-armed starfish?
https://www.reviveourgulf.org.nz/news/photogrammetry-reveals-okahu-bay-kutai-beds-in-stunning-detail/
Photogrammetry: Seascape/New Zealand Geographic with support from LiveOcean Foundation
#kūtaiōkahu #shellfishrestoration #haurakigulf #marinerestoration
Our latest 3 month survey results are in!!
The mussels we put down last year seem to be settling in to their new home nicely, even though we`ve seen higher than usual sea-temperatures.
Mussel density is high within the restored mussel beds varying from 243 ± 48 per m2 to 426 ± 115 per m2. Densities within each bed are similar to those we found in our one month surveys.
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#kūtaiōkahu #kutaiokahu #musselrestorationōkahu
Our latest 3 month survey results are in!!
The mussels we put down last year seem to be settling in to their new home nicely, even though we`ve seen higher than usual sea-temperatures.
There was no obvious difference in dead mussels between mud (M1-M3) and shell beds (S1-S3).
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#kūtaiōkahu #kutaiokahu #musselrestorationōkahu
Ōkahu Bay 3 Month Monitoring.
Carina, Jen and our PhD candidate Sophie checked out the Ōkahu Bay mussel beds on Tuesday. Visibility wasn`t the greatest but after a summer of high temperatures and cyclones the kūtai appear to be happy and healthy.
3 Month survey results coming soon!
#kūtaiōkahu #kutaiokahu #musselrestorationōkahu
Ōkahu Bay 3 Month Monitoring.
Carina, Jen and our PhD candidate Sophie checked out the Ōkahu Bay mussel beds on Tuesday. Visibility wasn`t the greatest but after a summer of high temperatures and cyclones the kūtai appear to be happy and healthy.
3 Month survey results coming soon!
#kūtaiōkahu #kutaiokahu #musselrestorationōkahu
Ōkahu Bay 3 Month Monitoring.
Carina, Jen and our PhD candidate Sophie checked out the Ōkahu Bay mussel beds on Tuesday. Visibility wasn`t the greatest but after a summer of high temperatures and cyclones the kūtai appear to be happy and healthy.
3 Month survey results coming soon!
#kūtaiōkahu #kutaiokahu #musselrestorationōkahu
Pic #4 NZ Triple fin finding a new home within the reseeded Kūtai reef in Ōkahu Bay.
60 tonne of mussels seeded into Ōkahu Bay ✔️
Over the past 2 weeks we`ve been busy working to recreate Kūtai reefs in Ōkahu Bay.
Link In Bio
#kūtaiōkahu #kutaiokahu #musselrestorationōkahu
Pic #3 Kūtai on the seafloor hours after being seeded in to Ōkahu Bay.
60 tonne of mussels seeded into Ōkahu Bay ✔️
Over the past 2 weeks we`ve been busy working to recreate Kūtai reefs in Ōkahu Bay.
Link In Bio
#kūtaiōkahu #kutaiokahu #musselrestorationōkahu
Pic #2 Ngāti Whatua Tiaki about Te Kawau watching Kūtai being seeded in to Ōkahu Bay.
60 tonne of mussels seeded into Ōkahu Bay ✔️
Over the past 2 weeks we`ve been busy working to recreate Kūtai reefs in Ōkahu Bay.
#kūtaiōkahu #kutaiokahu #musselrestorationōkahu
Pic #1 Mussels being seeded in to Ōkahu Bay.
60 tonne of mussels seeded into Ōkahu Bay ✔️
Over the past 2 weeks we`ve been busy working to recreate Kūtai reefs in Ōkahu Bay.
For more info Link In Bio
#kūtaiōkahu #kutaiokahu #musselrestorationōkahu
Another 250 cu.m of shell hash goes in to prepare Ōkahu bay for kūtai / mussels. That’ll be 1,200 cu.m in total – about 120 truck loads! #kutaiokahu #musselreefrestoration
A beautiful morning in Ōkahu bay! #kutaiokahu
The preparations for bringing kūtai/mussels into Ōkahu bay have begun with the deposit of a shell base to lift these green lipped kūtai off the sea-floor to improve their survival.
Only two generations ago, the bay was the blue pantry or pātaka kai of Ngāti Whātua Ōrākei, with plentiful shellfish and an ocean that was ‘red with snapper’.
As eco-system engineers, kūtai beds can filter vast volumes of water and bring back marine creatures large and small – such as tāmure / napper, whēke / octopus, sea snails – by providing a habitat and food source.
In the near future, we will deposit 60 tonne of kūtai into this area to help create a bay that a ‘smells different, tastes different, looks different, feels different’.
Ngā mihi nui to all of those involved – past and present – who had this wonderful vision and those who have worked alongside us to help make it a reality!
kūtaiōkahu #kutaiokahu #musselrestorationōkahu
Frequently Asked Questions
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Can people harvest and eat these kūtai?
No, please don’t! Even if you happen to be uri o Ngāti Whātua Ōrākei. You’ll wreck our experiment and chances are you’ll get really, really sick. Kūtai accumulated heavy metals, contaminants and bacteria in their flesh and Ōkahu Bay frequently is on the Safeswim high-risk list. Our hope is that our grandchildren’s grandchildren’s grandchildren will one-day have tasty, edible, safe kaimoana from the Waitematā.
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What is known about the historic beds in Ōkahu Bay?
Ōkahu Bay was once an important source of kai moana for Ngāti Whātua Ōrākei, with large shellfish beds of pipi and tuangi / cockles. Historical records from mussel dredging show that there were dense beds of green-lipped mussels in the Rangitoto channel and other places in the Waitematā. It’s not clear how close to the Ōkahu Bay shoreline these beds came, although we have found some large kūtai shells in and around the area we are working. All up, over 500 sq.km of kūtai reefs were dredge fished from the inner Hauraki Gulf between 1910 – 1965.
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Why haven't the beds recovered on their own?
Generations upon generations of kūtai went into forming the reefs. Fishers in the day recall the kūtai coming up like ‘rolls of carpet’. Marine scientists believe this fundamentally damaged the habitat, removing structure critical to the settlement of kūtai larvae / spat like filamentous algae, hydroids and hard shell surfaces. Sedimentation adds to the challenge, where poor land use practices have resulted in the loss of filtering wetlands and deforestation allowing large volumes of sediment to flow into the Gulf, making the water more turbid and the seabed conditions more muddy.
Despite shellfish beds being one of the most threatened marine habitats on Earth, there is still a lot to learn about shellfish bed ecology. Our subtidal, soft-sediment kūtai (Perna canaliculus), a species unique to Aotearoa / New Zealand, present some specific challenges, with different habitat needs across its lifecycle when compared to well studied shellfish such as oysters.
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Why is a shell-base being trialed at Ōkahu Bay?
Kūtai are quite hardy and can handle a moderate amount of sediment suspended in the water. However, they don’t like being buried in it. The shell hash base used in Ōkahu Bay (50m x 50m and approx. 30-50 cm high) will be used in a large-scale test to compare survival of kūtai placed on a shell vs soft sediment. We expect the shell to improve survival and encourage recruitment by lifting the kūtai out of the muck and providing an attachment substrate for juvenile mussels and other marine life.
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Will this project make a difference to water quality and biodiversity in Ōkahu Bay?
A single adult kūtai can filter between 150–350 litres of seawater per day. Assuming each of our six plots has around 700,000 mussels that’s about 630+ million litres of filtration per day! It sounds big, but let’s not get too excited, it’s a drop in a bucket considering the volume of water in Ōkahu Bay (and tidal currents etc). However, we will be keeping an eye out for any localised improvements in turbidity across the beds. Biodiversity improvement should be more apparent and we expect to see more species, like crabs and shrimps, juvenile fish and starfish to show up around the beds within 6–12 months.
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Why is kelp part of the experiment?
The presence of kelp (in our case Ecklonia radiata) is known to reduce the accumulation of sediments, reduce predation by starfish, and there is also evidence that kūtai growth is enhanced. By monitoring the health, growth rates and biological communities, it is hoped that the study will provide evidence that kelp can help to establish kūtai reefs.
News
Reflections on the Australian Coastal Restoration Network Symposium: Strengthening Partnerships
Last week, a delegation from Revive Our Gulf headed to Townsville to participate in the Australian Coastal Restoration Network Symposium. This two-day conference brought together specialists in coastal restoration, from across Australia, fostering collaboration and knowledge exchange. A New Zealand delegation and the infusion of Māori tikanga into the conference gave the conference a distinctive... Read more »
26 May 2023
12 months on at Ōkahu Bay
This kaupapa is long-term and intergenerational, and for that reason, milestones defined simply by the passing of time can seem a little arbitrary. But, time itself can also be a marker of progress. Although it’s early days, we were excited to reach the 12-month anniversary of the Ōkahu Bay mussel reefs. I will confess to... Read more »
20 December 2022
Ōkahu Bay 6 months monitoring
Weather delayed our 6-month monitoring of Ōkahu Bay, but results now out… Beginning to see some difference in survival of the kūtai on shell (S1..S3) 😀 vs, those on bare sediment (M1..M3) 😫. A few small 11-arm starfish moving in but the water was clearer this time. Visit the Ōkahu Bay project page
25 August 2022
Photogrammetry reveals Ōkahu Bay kūtai beds in stunning detail
You could be forgiven for thinking that the kūtai / green-lipped mussels have been hard at work clearing the murky waters of Ōkahu Bay. Unfortunately, we would need square kilometers of kūtai beds to get the water this clear! These images were stitched together from lots of smaller, close-up photos to form a composite image... Read more »
23 May 2022
Ōkahu Bay three month monitoring results
It's been 3-months since we deployed 60 tonnes of kūtai into Ōkahu Bay. Here's the results of the 3-month monitoring that we recently carried out.
8 March 2022
60 tonnes of kūtai for Ōkahu Bay
Today we finish the job of depositing 60 tonnes of mussels / kūtai into Ōkahu Bay. Over the past two weeks our friends at NIML/Sanford have made three trips across from the Eastern Firth of Thames, bringing 20 tonnes of kūtai on each trip.
30 November 2021
Tangata Whenua
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