Awhi mai awhi atu – kuku restoration

Mātauranga Māori and science are helping to solve a few questions in Ōhiwa Harbour:

• What has caused the mussel beds to disappear?
• Can we restore the mussel beds?
• Is it possible to use natural fibres as mussel lines?
• Which natural fibres are the strongest/best fit for this restoration project?

The questions form the basis of Awhi Mai Awhi Atu: Enacting a kaitiakitanga-based approach to EBM – a Sustainable Seas project.

Tangaroa – Māori-led research

The Sustainable Seas National Science Challenge helps Aotearoa New Zealand enhance the value of our marine resources while ensuring they are safeguarded for future generations. One of its research themes is Tangaroa – Māori-led or partnered research that is informed by mātauranga and tikanga Māori. Projects in this theme enable direct benefits to the iwi and hapū involved.

The Awhi Mai Awhi Atu restoration project combines multiple aspects of mātauranga, which are helping lead researcher Associate Professor Kura Paul-Burke and her team re-establish kuku/kūtai/mussel beds in Ōhiwa Harbour.

Kuku/mussel beds and ecosystem services

Kuku are a taonga species for the local iwi. They provide kaimoana and are important for expressing manaakitanga. Kuku have several important roles within marine ecosystems. Mussels are filter feeders – as they draw in seawater to trap phytoplankton, they also remove sediments and other substances that make the water murky. Kuku beds provide habitats for other sea creatures and act as nurseries for juvenile fish.

Disappearing kuku beds

In 2007, Ōhiwa Harbour hosted a continuous 2 km reef of kuku beds with around 112 million juvenile kuku. By 2019, the number was down to just 80,000.

When the kuku beds first began to disappear, a rāhui was put down for 8 years as the losses were blamed on overfishing, but the kuku continued to disappear. Researchers considered other causes such as warming seas due to climate change. The likely culprit appears to be pātangaroa (sea stars). Sea stars eat mussels, and their numbers have increased dramatically. Kura sees this issue as a wicked problem. She says, “Pātangaroa have their own mana and their own mauri because they are from here. They are meant to be here.”

Using mātauranga and tikanga Māori to aid kuku recovery

Kura and the team used mātauranga ā iwi (local knowledge) to establish the size and shape of traditional mussel beds as well as the number of beds that had originally existed in the harbour. This information provided a valuable baseline for research.

Mussels are a major aquaculture species in Aotearoa. Mussel farmers have trialled numerous ways to seed mussel spat onto lines. They’ve found using fibrous plastic ropes is the best way to encourage spat to settle and grow into adults. However, the research team wanted to avoid microplastics entering the water and the kaimoana. To solve this problem, they are making mussel lines from natural materials. Kura enlisted weaving experts to create lines from harakeke, tī kōuka and kiekie (a woody climber) in hopes that kuku spat would attach to each. When the team went out to check the buoys and lines a few months later, they couldn’t find them. To their surprise, the mussel lines were so heavy with about 20,000 kuku per line that they were under the water!

Tī kōuka was the hardiest material. Lines created with tī kōuka lasted up to 5 months before breaking from the buoys and settling on the harbour floor. The weavers are trying a new combination of materials – a core of pirita (supplejack) for strength with either tī kōuka, pīngao or neinei woven around it. Renowned weaving expert Whaea Roka Ngarimu-Cameron shared her mātauranga and expertise, so she and her students were invited to help the research team place the new lines in the harbour.

It’s lovely to use a traditional resource in a new way. I am very interested to see how the kuku like pīngao and neinei – and how long they last!

Whaea Roka Ngarimu-Cameron, weaving expert

The Awhi Mai Awhi Atu restoration project has set up four kuku restoration stations. They’ve discovered three early-stage kuku beds near where they had deployed their initial sets of lines. When the lines break off and fall, the kuku stay as a group and grow as a whānau, while the lines safely biodegrade.