Saving mussel beds with a bi-cultural approach

4:51 pm on 29 January 2021

Māori knowledge and western science are being combined to save disappearing mussel beds in an eastern Bay of Plenty harbour.

Waikato University marine scientist Kura Paul-Burke.

Waikato University marine scientist Kura Paul-Burke says mussel beds have been disappearing fast in Ōhiwa Harbour. Photo: Supplied.

Between 2007 and 2019, the mussel/kuku population at Ōhiwa Harbour fell from 112 million to just 80,000, according to Waikato University Associate Professor in mātai moana (marine research), Kura Paul-Burke.

In a bid to bring them back researchers are integrating mātauranga Māori into western conservation methods, with excellent results.

Paul-Burke told Morning Report many factors were causing mussels to decline in the harbour.

"In 2009, we discovered an estimated 672 tonnes or 1.2 million eleven-armed sea stars predating on the mussels.

"Sea stars are… a voracious consumer of mussels," Paul-Burke said.

While 15 sea stars per hectare was considered a sustainable number, in 2019 there were an estimated 100,000 sea stars in a two-hectare pipi bed in the bay.

Climate change was warming sea water and increasing the acidity of the ocean, causing further problems for mussels, she said.

"Ocean acidification… reduces carbonate in the sea.

"Mussel shells are made of calcium carbonate, so reduced carbonate in the sea water makes it harder for mussels to grow thick, strong shells that help them to better resist predation by sea stars."

Paul-Burke said elders from local Māori tribes were asked to help locate shellfish beds when the research began in 2007.

Waikato University marine scientist Kura Paul-Burke.

Kura Paul-Burke says kaumatua helped locate shellfish beds in Ōhiwa Harbour using traditional landmarks. Photo: Supplied.

"They would, using traditional landmarks, say to us 'the mussel beds start here and there and you will find scallops there'," Paul-Burke said.

"It was amazing. They were spot on, even though many of them hadn't dived for 30 or 40 years."

The Awhi Mai, Awhi Atu project has been co-developed with hapū/iwi of Ōhiwa harbour and is supported by Bay of Plenty Regional Council and the seven partners of Ōhiwa Harbour Implementation Forum.

Since 2019, the project has trialled using mussel lines made of natural fibres, with early success.

Mussels/kuku have grown on lines made from cabbage tree/Tī Kōuka leaves that were gathered from the ground and prepared in a similar way to flax, before being woven into ropes.

"Commercial mussel lines are good at growing mussel beds, but are heavily plastic-based, so we thought 'what if you use natural materials' to see if mussel spat would attach and grow and at the same time be kinder to the harbour," Paul-Burke said.

"It's estimated approximately 8 million tonnes of plastic pollution ends up in our oceans every year, so growing mussels on biodegradable, natural lines, there will be less micro-plastic pollution in our harbour and in our kai moana and in ourselves."

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