Seafood Magazine: Harvesting bioactives from seastars to save kuku/mussel beds

Shared with permission from Seafood New Zealand Magazine - December 2021:

An over-abundance of pātangaroa (11-armed seastars) is causing a dramatic decline in populations of kuku/kutai (mussels), pipi and cockles in coastal areas of Aotearoa New Zealand, in particular Ōhiwa harbour. Local iwi, with the support of the Bay of Plenty Regional Council and Ōhiwa Harbour Implementation Forum (OHIF), are working with Sustainable Seas Challenge researchers to develop innovative products from harvested pātangaroa to fund the necessary management action.

“Seastars are ferocious predators, they just smash through the mussels,” says Matt Miller (Cawthron), who co-leads the Pātangaroa hua rau project with Kura Paul-Burke (University of Waikato) and Mathew Cumming (Plant & Food Research). “I didn’t realise how big they get. I thought they were hand-sized, but they can be bigger than a dinner plate. They remind me of the film Alien – they could wrap round your head!”

Because they can regrow lost limbs, pātangaroa may have bioactive properties that could aid human wound healing and skin health. They could also be a source of marine collagen, which is in high demand for cosmetics and supplements due to its high solubility, effective extraction and high bioactivity.

Although the idea is to set this up as an innovative income stream, the driver isn’t commercial profit. It’s about improving the ecosystem health, to support thriving kuku beds where people can harvest kai for generations to come.

“The aim is to generate enough income to support people to harvest and process the seastars. There are lots of fantastic people engaged in the harbour, but it’s on volunteers’ own time. We shouldn’t keep expecting people to do it for free,” says Miller.

“It’s also important to remember that the seastars are meant to be there, they are native not a pest species. We’re not trying to remove them from the harbour completely, just to help the ecosystem rebalance. There’ll need to be ongoing ecological assessment to determine how many seastars need to be harvested.”

As well as improving the kuku fishery and providing monetary support for local people to manage pātangaroa, the biodiversity in the harbour should also improve. Kuku form important habitat for other species to live on and around. Results from an aligned project, Awhi Mai Awhi Atu (also led by Paul-Burke), show a dramatic increase in both the number of species and individual critters at kuku restoration stations in Ōhiwa Harbour.

Working with the local iwi, hapū, regional council and interested communities has led to some critical strategic decisions.

“We’re not looking at specialised high-end – and therefore expensive – equipment and processing that is only feasible for big corporates. We’re trialling processing that involves buckets and industrial kitchen gear as much as possible, based on the kind of equipment and facilities that is much more easily available to iwi, hapū and local communities,” says Miller.

The team is also identifying potential commercial players that iwi and hapū could connect with if needed for specific steps.

“We’re halfway through our sampling but are already seeing interesting, unique properties compared to other marine collagen, such as fish-sourced,” says Cumming. “We’ve got an idea of the process, there’s still some refinement to do, and the economic case is still to be determined to see if it is a feasible proposition for a self-sustaining management plan.”

By January 2023 the team should have all the information that iwi, hapū and OHIF need to determine if there is a viable business case.

If there is, then the collaboration will have co-created an opportunity for a circular economy model to fund pātangaroa management, which supports an ecosystem-based management approach of the harbour that aligns with local Māori values.

Building on a decade of work

This mahi stands on the shoulders of Paul-Burke’s work with the local iwi, hapū and regional council over the last decade.

Kuku are a taonga (treasured) species for the local iwi, and crucial to the health of this ecosystem. Paul-Burke,  iwi and interested kai gatherers have all watched the kuku population deplete – and the pātangaroa population explode – over the last 20 years.

“In 2007, there were 112 million baby kuku in a continuous 2km reef – by 2019 there were less than 80,000 in the entire harbour,” says Kura Paul-Burke. “Meanwhile, in 2019 we found 50,000 seastars per hectare – you’d expect to see around 15 per hectare in a healthy balanced ecosystem.”

Three of the four kuku beds in the harbour have disappeared in the last 10 years, affecting the harbour’s kaimoana (seafood), mahinga kai (cultivation) and mauri (vital essence), and reducing the ability of mana whenua to express manaakitanga (expression of respect and hospitality to visitors through provision of kaimoana).

The exact causes of this ecosystem degradation are not yet fully understood.