Ōkahu Bay Restoration

We are proud to announce that Ngāti Whātua Ōrākei and the Revive Our Gulf project are working on a study that looks to build on past efforts to re-seed kūtai / mussel beds in Ōkahu Bay. 

This project forms part of a long-term, intergenerational environmental restoration kaupapa.  This includes re-planting of the whenua and improving the health of the Waitematā. 

This is rooted in a need to re-establish kaitiakitanga and the physical and spiritual connection to the whenua, rohe and moana, after a sorry history of gradual land confiscation and desecration. Only two generations ago, Ōkahu Bay was the blue pantry or pātaka kai of the hapū, with plentiful shellfish and an ocean that was said to be ‘red with snapper’.

By establishing kūtai beds in the Waitematā it is hoped that one day we can return to the traditional cultural practices of kohinga kai / food gathering from our moana.

Again we acknowledge our whānau, partners and all those that have contributed to the wider kaupapa so far. We are excited to continue this mahi with the whānau so we can all be involved in helping our hapū and iwi protect and care for our wai – divers, fisherman, kaimoana lovers, paddlers, tātou katoa!

Ōkahu Bay Restoration - Project Progress.

Mussel Deployment – Whiringa-ā-rangi

We are pleased to say that the foundation works have been completed and are ready for the final stage of Mussel deployment into our bay. We are looking to try to seed 60 tonnes worth of mussels onto the 3 prepared sites just off the Ōkahu breakwater – Pylons.

On November the 18th we look to undergo the first 20t drop of 3 planned mussel deployments. These drops will be over 3 week period with the last being on the 30th of November.

Due to Covid restrictions, we can’t have the big launch that we had initially planned but instead will still adhere to our Tikanga and make sure all these cultural elements are taken care of and our manuhiri are looked after. We hope that by the time we get to the last drop on the 30th, covid-19 restrictions will have eased and we can all celebrate together.

Shell deposition at Ōkahu Bay

This is just stage one of the works where the project team is working with Ports of Auckland to prepare a section of the bay for mussel beds using “up-cycled” shell hash from maintenance dredging.

A platform measuring 50m x 50m and approximately half a metre deep will be deposited on the inside of the breakwater piles. The shell hash will be extracted from the Rangitoto Channel just out from Ōkahu Bay. Using a shell substrate for the mussels beds is thought to improve survival rate and increase available habitat for juvenile mussels and other organisms to settle on.  We plan to deposit the mussels before the end of the year.

Click here for more. 

Toitū Te Waitematā – Whānau Workshops

Thank you to the whānau and our Waitematā hapori members have been apart of our Toitū te Waitematā workshops.

We are excited to continue to the kōrero with whānau so we can all be involved in helping our hapū and iwi protect and care for our wai – divers, fisherman, kaimoana lovers, paddlers, tātou katoa!

If you have any pātai or whakaaro around any of the Toitū Te Waitematā kaupapa click here.


Get in touch!
If you have any pātai or whakaaro around this kaupapa please get in touch with Mervyn Kerehoma – Toi Taiao Project Lead: mervyn@nwo.iwi.nz

Want to get involved? Click here to register to be apart of the group ‘Te Ohu Wai’ to receive info on upcoming workshops, training and opportunities about our wai and moana.

Learn More.

Learn About Revive Our Gulf

Revive Our Gulf works in partnership with iwi / hapū and communities to restore the mussel beds of the Hauraki Gulf.  We bring together expertise in marine science and mātauranga, consenting and biosecurity. We combine resources and funding to get mussel reef restoration projects supported and underway.  The professionals and volunteers behind Revive Our Gulf have deployed more than 150 tonnes of mussels to date across a number of project sites in the Hauraki Gulf / Tīkapa Moana / Te Moananui-ā-Toi.

Visit their website here – https://www.reviveourgulf.org.nz/

History of Ōkahu Bay Restoration Projects

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.

The current project builds upon work spearheaded by the late Richelle Kahui-McConnell, working closely with Ngāti Whātua Ōrākei whānau and two generations of the Tamaariki whānau—Tamaiti and his daughters Moana and Donna Tamaariki.  Working with the scientific community and early Revive Our Gulf volunteers, this group conducted a number of projects looking at feasibility of kūtai beds in the bay.  As Moana Tamaariki-Pohe, a long-term kaitiaki and advocate for the bay describes it, the goal is to create a bay that ‘smells different, tastes different, looks different, feels different.’

“Waters fit to swim in at all times, with thriving marine eco-systems that provide sustainable kaimoana resource for the Ngāti Whātua Ōrākei community who have a strong daily presence in and on the bay as users and kaitiaki” Ngāti Whātua Ōrākei long-term ecological restoration plan (Kahui-McConnell 2012)

Projects included a small pilot kūtai drop in 2014 and a pylon kūtai ‘wrap’ to attract spat in 2017.  Also instrumental to improving the health of the bay was lobbying Auckland Council to seek the removal of 154 boat moorings from the bay in 2019.  The removal of the boats reduced pollution from anti-fouling hull coatings and opened the bay up for safer recreational use such as waka ama (outrigger canoeing).   The foundational work on kūtai restoration, and clearing the bay of boats, now allows for this next phase.

FAQ - Get to know more about this kaupapa! .

Can people harvest and eat these kūtai?

No one can harvest and eat these kūtai as you’ll get really sick – it will also decrease chances of this experiment being successful. 

Did you know, Kūtai accumulated heavy metals, contaminants and bacteria in their flesh and Ōkahu Bay frequently is on the Safeswim high-risk list

However, our hope is that our mokopuna to come will one-day have tasty, edible, safe kaimoana from the Waitematā.

What is known about the historic beds in Ōkahu Bay?

Ōkahu Bay was once an important source of kai moana 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.

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.

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.

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 less welcome guests like starfish(!) to show up around the beds within 6–12 months.

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.