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/

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.

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.

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.

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.

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.

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.

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.