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The latest stage in an ongoing project to restore and replenish severely depleted mussel/ kūtai beds throughout the Hauraki Gulf is being pursued by reef restoration trust Revive Our Gulf (ROG).
Working in collaboration with Ngāti Manuhiri Settlement Trust and Ngāti Whātua Orakei, ROG has already deployed 370 tonnes of kūtai in two experimental projects around the Gulf, including a major drop of 150 tonnes in the waters off Mahurangi Harbour over Matariki last year.
The mussel reef restoration group has now teamed up with Kelly Tarlton’s Marine Wildlife Trust and the Institute of Marine Science at the University of Auckland to learn more about baby mussels and why they’re not settling in significant numbers in local waters.
ROG executive director Katina Conomos says it remains a scientific mystery why kūtai numbers haven’t come back naturally after being almost wiped out last century, despite all the mussel farms dotted around the Gulf, but says it could have something to do with the very young mussels, known as spat.
“We know there are mussel spat in the Hauraki Gulf, but it seems that generally, they won’t settle in significant numbers and if they don’t settle down and start a community, there are no mussel reefs,” she says.
“Understanding their reluctance to put down roots, and grow into kutai, is a vital part of the restoration puzzle.”
Conomos says seaweed is one of the surfaces spat latch onto, so over the next few months researchers will try to find out if there’s a particular type of seaweed that might entice spat to start new communities on the ocean floor.
“We have iwi and scientists, conservationists and volunteers working hard to try and figure out how we can do this at scale,” she says.
“What’s obvious is that we need to enable nature to get in behind our efforts, to bring back the mauri, the essence of this magical stretch of water.
“If we find out the sort of home they prefer, then we can build them a place to stay, taking us one step closer to re-musseling Tīkapa Moana.”
Tens of thousands of spat have brought in for the research, via chilly-bin, from a commercial hatchery in Nelson to the Kelly Tarlton’s Aquarium in Auckland.
Mussel reefs once covered more than 600 square kilometres of the Hauraki Gulf seabed, but were destroyed by a boom-and-bust commercial dredging industry. The reefs never came back after their demise, partly due to sediment flowing off the land and into the gulf.
“Right now, the bottom of the Gulf in large parts is a sludgy, gloopy mess of mud and sediment,” Conomos says. “Ask any diver.”
