Traditional knowledge and the kōura nursery cycle

Exhibition experience developer Dan Parke spoke with Tamati Stevens a kairangahau, kairuku, and educator specialising in rocky reef ecosystems.

Tamati’s mahi blends mātauranga and scientific research, making him a leading expert in traditional management of taonga species of the rocky reef, such as kōura. Tamati believes that understanding of the kōura nursery cycle is the key to growing this precious resource.

A man in a wetsuit is holding a crayfish up in front of himself. He is looking at the camera.

Tamati in dive gear holding a crayfish. Photo courtesy of Tamati Stevens

The kōura nursery cycle

The characteristic buzzing of kihikihi signals the height of summer for many of us in Aotearoa New Zealand. For most of us, their song evokes the memory of long hot days, swimming, and barbeques. For Tamati, kihikihi sound also signals the arrival of kōura at their kōhanga. There, the kōura undergo the three-month-long process of moulting and mating.

Watch to see where Tamati finds a kōura hiding.

New arrivals to the kōhanga have pale, clear-looking flesh visible on the underside of their tails. The crayfish begin fasting in preparation for moulting their hard exoskeleton.

Hands holding a crayfish upside down. Someone else is holding a white ruler across the middle of the crayfish.

Pale flesh of a crayfish not in moulting phase. Photo courtesy of Tamati Stevens

For several weeks, they crowd into sites like the whare of maratea – rocky crevices hidden under rimurimu.

The closer they come to moulting, the darker that visible flesh under the tail becomes. First starting to look murky rather than clear, then becoming noticeably brown, and finally almost black. Kōura in this state are now ready to moult.

Two hands holding a crayfish upside down. There is a white ruler placed across the belly of the crayfish.

Black flesh of the crayfish just before moulting. Photo courtesy of Tamati Stevens

Moulting is a time of great vulnerability for kōura – they can be locked into position for several weeks, unable to defend themselves. They climb into the rimurimu for camouflage and slowly expand back out of the shell, through the gap between the carapace and the tail.

The whirling currents contribute an essential pressure to help the shedding process. The fresh case underneath takes several days to harden.

Parts of a crayfish exoskeleton sitting in pieces on a boat deck. There is a hand holding part of it and the front part of a gumboot.

Crayfish carapace. Photo courtesy of Tamati Stevens

Mating begins after moulting. Females carry their fertilised eggs underneath their tails and are said to be “in berry” at this time. She carries her eggs for a few months before making her way to the outer reef to spawn – releasing larvae by the thousands into the ocean currents.

Only a tiny percentage of these individuals will make their way back to these kōhanga in adulthood.

Maintaining and growing the kōura population depends on getting as many adults as possible through the nursery cycle each year.

An upside-down crayfish showing a lot of small red berries near it's tail. There is a hand holding one end of it.

A female crayfish with eggs. Photo courtesy of Tamati Stevens

Sustainable harvest

Current regulations state that crays cannot be harvested recreationally or commercially while their exoskeletons are still soft immediately after moulting, or while they are in berry.

Tamati believes the rules do not go far enough to protect these taonga. He recommends that no crayfish be taken during their pre-moult stage in the nurseries.

By allowing the kōura a three-month season to gather and moult, reproductive success is significantly increased. At a time when food security and climate change are key issues, Tamati believes there’s a strong case for a change in regulations.

Knowledge of the kōura nursery cycle draws on both mātauranga passed down by Tamati’s Nan Rehe Perry, and the extensive research and monitoring undertaken for his masters and PhD theses.

Tamati’s research has since supported this traditional understanding and has been key to his success in establishing new crayfish nurseries and thriving reef ecosystems. In his wānanga, he encourages kairuku to observe the colour of the underside of the kōura’s tail and use this to judge whether it should be taken.

Tamati addresses the rōpū (group). Photo courtesy of Tamati Stevens

Learner divers in the shallows. Photo courtesy of Tamati Stevens

Tamati and his supporters. Photo courtesy of Tamati Stevens

Processing kina on the beach. Photo courtesy of Tamati Stevens

One of the rangatahi at the wānanga holding up a kōura from the catch. Photo courtesy of Tamati Stevens

Wānanga campsite at sunset. Photo courtesy of Tamati Stevens

Kōura as rongoā

According to Tamati, there is one notable exception to this rule: the near-black pre-moult kōura may be taken by experts for use as rongoā. Tamati has been following this traditional practice for many years now, to attend to kuia or koroua suffering from cancers or heart conditions.

With permission from the whānau of the elder, he travels to the coast of their tūrangawaewae to seek out kōura at just the right stage in the moulting cycle. The flesh looks dark where it’s visible underneath the tail. The darker the better for use as rongoā, and like his Nan who taught him, Tamati refers to the kōura as tangata whenua.

Two people standing by the ocean. One man is in a wet suit. They are holding a large crayfish and looking at the camera.

Tamati and kaumātua (respected elder) Matutaera Te Nana Clendon ONZM. Photo courtesy of Tamati Stevens

Tamati selects a kōura tangata whenua for the kuia or koroua and takes it back to them. He prepares it for eating and feeds it to them, telling of his journey to collect this special kai from their home.

He explains that the meat of the kōura tangata whenua has different properties to that of a regular cray. The prepared flesh is much pinker than usual, and it is easy on the stomach for those who have trouble keeping food down.

The effect of this rongoā is remarkable. Tamati has had kuia who haven’t been able to eat properly in months sit up in bed and take great enjoyment from this kai.

Without exception, elders who have been treated in this way by Tamati outlive the life expectancy they are given at diagnosis.

Teaching the next generation

Kōura are just one of the many species of the rocky reef. In his teaching practice, Tamati does not focus only on kōura. Tamati’s ākonga learn about all the relationships of the reef.

Kōura exist interdependently with other species such as maratea, rimurimu, kina and mararī. Each species relies on the others to perform essential roles in the ecosystem to thrive. Tamati hopes that teaching the next generation how to use this knowledge will ensure they inherit these precious resources.

A man and woman and several children are huddled together and looking at the camera. The man is holding a crayfish and a ruler.

Tamati and rangatahi demonstrate how to measure a cray