For many years people who care about the Hauraki Gulf Marine Park came together at the Hauraki Gulf Forum’s annual seminar. Many attendees had seen great success on the islands where predators had been removed, trees planted and birds, and reptiles returning in great numbers.
The same could not be said for the marine environment. There were presentations on whales getting hit by boats, sediment clouding the waters, seabirds caught on hooks and all the issues facing Tīkapa Moana / Te Moananui-ō-Toi. Not wanting to leave the audience too depressed, conference organiser Tim Higham was always careful to end the day with a message of hope. In 2012 the seminar was titled “Charting the Enhancement Pathway” and the message of hope was to come from NIWA scientist Dr Darren Parson.
Dr Parson’s talk covered the wonder of the historic green-lipped mussel beds, how they had been decimated by over-fishing, and that surveys had show after half a century none had returned. Most of the audience knew this and the mood was grim. However, he then switched gears and showed how when he put mussels in cages, and placed them on the degraded seafloor, they survived! The mood in the room changed. Tim Higham called out to the audience for volunteers to look into restoring the mussel beds. A multidisciplinary group of more than 25 people signed up. These were scientists, planners, business people, fishing advocates, council staff, educators, environmental and community advocates. In June 2013 the group formed the Mussel Reef Restoration Trust which was registered as a Charitable Trust. The chair of the trust was John Laurence who had led the restoration of Motuihe Island. Members took up leadership responsibility for science and technical advice, logistics, planning and regulatory issues, communications, and relationships with iwi and industry partners.
Auckland University was a key partner as they had expertise in marine science and aquaculture and there was a lot to discover. Restoration of mussel reefs has never been attempted or achieved before. The trust adopted a “Learning by Doing” philosophy and the first deployments were to follow only a year later. Auckland University committed a doctoral student and resources to research the re-establishment of the mussel beds. The doctoral student was supervised by Dr Andrew Jeffs from the Institute of Marine Science at the University and Dr Shane Kelly from the Trust. The research investigated mussel survival, and the effects of bed size on mussel colonisation and the development of marine communities within seven pilot beds.
In late 2013 seven tonnes of green-lipped mussels were deposited off eastern Waiheke Island. The mussels were dropped by mussel barge and formed seven, dense, “living room” size plots within an embayment. The mussels matted together over a once barren seafloor and were colonised by a range of marine species. After some initial mortality, and some expected predation by starfish and snapper, the remainder served their intended ecosystem services.
In late 2014, an additional 63 tonnes of mussels was deployed and provided by North Island Mussels Ltd. The mussels were sourced from farms in the Coromandel area. Monitoring of these beds showed that they supported a diverse benthic community of molluscs, crabs, starfish, sponges and ascidians.
However, arrival of the unwanted Mediterranean fan worm in Coromandel posed biosecurity concerns for mussel restoration activities and the Trust was informed by the Ministry of Primary Industries that we would need a permit under the Biosecurity Act 1993 to continue restoration activities. Obtaining biosecurity permits was a lengthy process and required expensive and time-consuming procedures, such as submerging mussels in freshwater to kill any unwanted organisms.
Mahurangi Harbour was chosen as the next location, largely because there was an unused oyster farm nearby that had large enough tanks that could submerge one tonne bags of mussels. The one tonne beds created lots of biogenic structures and attracted baby snapper, koheru, goatfish, spotties and even squid. However, they struggled due to their limited size, so in 2017 the Mussel Reef Restoration Trust funded and co-ordinated the addition of five ten tonne beds. The project was warmly embraced the local community and iwi, and received a fair amount of media interest.
In 2018, Mussel Reef Restoration Trust added three more 10 tonne beds to the Mahurangi Harbour. However, fundraising activities stalled as the restoration method was very expensive, despite significant contributions from the aquaculture industry. Along with a new partner The Nature Conservancy who bought significant international shellfish restoration expertise, the Mussel Reef Restoration Trust increased its efforts to reduce biosecurity costs. These were eventually rewarded in late 2020 with Biosecurity NZ establishing a specific risk assessment framework for mussel reef restoration.
Mussel reef restoration efforts have now resumed in the Hauraki Gulf / Tīkapa Moana / Te Moananui-ā-Toi. Find out how you can get involved.