One day in 2008, marine science student Kura Paul-Burke was diving in Ōhiwa’s murky waters when the grey-brown of the sea floor suddenly gave way to a brilliant orange. At first, she was struck by the beauty of it. Then she realised she was looking at hundreds of thousands of 11-armed sea stars—pātangaroa, a native species—stacked five or six layers deep. Behind them, the seabed was littered with empty green-lipped mussel shells.
In 2007, the Bay of Plenty harbour was home to an estimated 112 million mussels. By 2019, only 78,000 were left.
Paul-Burke’s Ngāti Awa elders had noticed signs of decline well before then. No-one knew why the mussels were dying. Was it overharvesting? Sedimentation? But they knew there used to be more mussel beds, and in 2006, they urged her to investigate—then helped her to map the old mussel beds using both traditional landmarks and scuba surveys.
Researchers are still confirming the starfish are to blame, and figuring out what is causing the ecosystem imbalance in the harbour. In the meantime, Paul-Burke—now a professor of mātai moana (marine research) at the University of Waikato—wanted to see if it was possible to save the mussels and the harbour. The project wove together four iwi (Ngāti Awa, Te Ūpokorehe, Te Whakatōhea and Waimana Kaakū [Tūhoe]) and three councils, kaumātua and young people (pictured below, L-R: Megan Ranapia, Te Waikamihi Lambert and Cameron Phillips), mātauranga Māori and marine science.
Together, they built four restoration stations where baby mussel spat could attach and grow. Instead of using commercial plastic spat lines, they experimented with natural fibres. The strongest were made from fallen tī kōuka leaves woven into rope by master weaver Rokahurihia Ngarimu-Cameron and her students. In late 2018, the team hung them on floats in midwater, out of the reach of clambering starfish.
It worked. Mussels began growing in such numbers that they dragged the floats under the surface. When the tī kōuka lines eventually degraded, young mussels fell to the bottom “as a whānau”, Paul-Burke says, before reattaching to the sea floor.
As the researchers describe in a new paper, by 2021, three new mussel beds had formed close to the restoration stations, and the mussel population had increased ten-fold—showing what can be accomplished, says Paul-Burke, when several knowledge streams and communities pull together.