Hauraki Gulf Mussel Reef Restoration

Taking the Long View
Gord Stewart


Thirty eight million litres of cleaned water every year for a one-time $25 donation. Now that’s what I call good value.

That’s the calculated cost-benefit of reseeding the Hauraki Gulf seabed with our native green-lipped mussels. Oysters and other bivalves have been used overseas to filter and improve water quality and increase the abundance and diversity of marine life, but it’s not something that had been tried here at home.

The Mussel Reef Restoration Trust is changing all that. Established in 2012, the Trust admits the “Revive Our Gulf” project is an ambitious, long-term – even multi-generational – effort. It’s experimental, a trial-and-error approach and it appears to be working.

There was a time when mussel reefs proliferated in the Hauraki Gulf and Firth of Thames. They covered some 500 square kilometres of sea floor and it was estimated they could filter all the water of the Firth of Thames in a day.

But that wonder of nature was eventually lost with the advent of a commercial mussel dredging industry. Starting in the early 1900s, the industry reached its peak in 1961 when 2800 tonnes were harvested.

By the end of that decade the industry had collapsed. The reefs have never recovered and the modest remnants that remain would now take about two years to filter the Firth’s water.

Attempts at a comeback appear to be in good hands.

“The Revive Our Gulf project is new and innovative,” says Nick Prebble. “It’s different and moving quickly. That’s what attracted me.”

Prebble, a young graduate in environmental management from The University of Otago, has been involved for about a year now. He’s part of a core group that meets every month or so to scheme, plan, and push things along.

The background and skills of those leading and contributing to the cause are indeed impressive – ranging from marine biology, environmental science and conservation to community engagement, photography and design.

“The approach of the people behind this is pretty amazing,” says Prebble. “The project went from just an idea to 70 tonnes of mussles on the seabed in a little over a year.”

The first seven tonnes of green-lipped mussels were purchased from North Island Mussels Ltd and deposited off the eastern side of Waiheke Island in December 2013. They were dropped by a mussel barge and form seven, dense, “living room” size plots.

Things have ramped up with the support and active involvement of the mussel industry. Last September, 63 tonnes of mussels – about three and a half million live adults – were provided free of charge and placed in the same general vicinity as the first beds.

The Trust is currently supporting Ngati Whatua as they restore mussel beds in attempts to repair damage to Auckland’s Okahu Bay. The bay suffers from high sedimentation and elevated levels of heavy metals and other industrial pollutants sometimes found in an urban setting.

To make sure nothing is left to chance, research and analysis is a key part of the project. Auckland University, in partnership with the Trust, has committed a PhD student and resources to study the re-establishment of the mussel beds. The research is investigating mussel survival, and the effects of bed size on mussel colonisation and the development of marine communities within the beds.

The Trust also intends to look at whether empty shells attract spat and smaller mussels to form self- sustaining reefs. If this is successful, it would be a big win for industry and for the environment as currently the empty shells must go to landfill.

There appears to be real opportunity here for the wider mussel industry to fully embrace the initiative and perhaps, together with the trust, design mussel sorting and processing equipment that would further enable restoration.

Boaties, fishers and other fans and users of the Hauraki Gulf have to be pleased with the Revive Our Gulf efforts so far, but ongoing support and resources are needed to ensure the project continues to flourish.

Nick Prebble put it nicely when he said, “The Gulf is a unique and special place. It can regain some of its former beauty, but it needs a hand to do it.”
Gord Stewart is an environmental sustainability consultant. He does project work for government, industry, and non-profit organisations.

More Info …
Check out the Mussel Reef RestorationTrust’s website at www.reviveourgulf.org.nz for more details and to make a donation.
“Treasures of the Hauraki Gulf Marine Park” is a beautiful A2 poster noting the ecological benefits of mussel reefs. Great for school classrooms, it can be downloaded from the Trust’s website. Printed copies can be ordered from GulfPosters@aucklandcouncil.govt.nz.

[Photos provided]


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