The National Aquarium of New Zealand has teamed up with Kohupātiki marae to release long-fin tuna or eel into the Ngaruroro Moko-tū-ā-raro-ki-Rangatira river.

One long-fin tuna and a short-fin tuna have spent more than 10 years at Napier’s National Aquarium and have now been returned to the awa as part of a partnership with the iwi.

Working with the hapū, the aquarium team released two tuna into the river so the native fish could fulfil their lifecycle.

Longfin eels live to at least 60 years and only breed once, at the end of their life.

Hapū of Kohupatiki Marae watch as a mature long-fin tuna makes its way into the awa after being released from the Aquarium of New Zealand. Photo / Warren Buckland

When they are ready to breed, the tuna will leave New Zealand and swim to the sub-tropical Pacific Ocean to spawn. No one knows precisely where, but the Department of Conservation suspects it is probably in deep ocean trenches.

Long-fin tuna are a taonga in New Zealand, and while not on the endangered list, they are on the at-risk declining list.

The native tuna cannot cope with changes to their environment and are heavily affected by human activities, such as pollution, the building of dams, loss of vegetation near their habitat, and overfishing.

Aki Paipper, who has been leading the call for restoring the Ngaruroro River back to its former glory, was excited to see the tuna released in the river.

Aquarium of NZ staff and hapū of Kohupatiki Marae whānau at the eel release along Ngaruroro River. Photo / Warren Buckland

With neighbouring industrial businesses and recreational fishing, Paipper worries that the river is becoming inhospitable for the tuna and other fish species living there.

The iwi is looking into several ways to help protect and look after the tuna for future generations, one of these being to put a rāhui in place to limit or stop the fishing of the long-fin tuna.

However, the partnership with the National Aquarium is the first step in looking after the tuna and goes hand in hand with Kohupātiki Marae’s work around cleaning and restoring the free-flowing river.

With help from the Kohupātiki Marae, the aquarium retrieved around five or six tuna to take back to the aquarium to continue conservation and storytelling in the community.

Tom McGuire, eel whisperer, caught long and short-fin tuna to replace mature eels from the Aquarium of New Zealand. Photo / Warren Buckland

The aquarium got its pick of the “bed” of eels when it came time to retrieve the hīnaki or eel trap; the net was packed, and it took home a healthy bunch of long-fin and short-fin tuna.

Now the tuna will be kept at the aquarium for five to 10 years, depending on where they are predicted to be in their lifecycle.

Hopefully, once the tuna is at a stage where they are ready to start mating and migrating, they will be released back into the Ngaruroro River, and the process will start over again.

Kaumātua Bevan Taylor said the tuna release was a historical event. To his understanding, this was the first time the aquarium had ever released the native tuna back into the wild.

He explained the partnership is special and helps continue the care of the local environment and fish species that live in the awa behind the marae.

“If we look after them, they will look after us,” Taylor said.