Hopes new study will help boost population of threatened NZ freshwater mussels, get them back on the menu

Lower North Island iwi and conservationists have launched an ambitious project in Wellington this weekend with an aim to boost the population of the at-risk New Zealand freshwater mussel.

An experiment is underway in Wellington to try to boost the mussels' survival rates by giving some a new home. Source: 1 NEWS

Two hundred kākahi have been relocated from Wairarapa Moana and Lake Kohangapiri to Zealandia eco-sanctuary in Wellington.

Zealandia conservation project leader Pascale Michel said the endemic species is known as an 'ecological engineer' due to the fact one mussel can filter around a litre of water per hour.

"The two reasons why we’re bringing back the kākahi is one, to expand the range of the kākahi itself and give it a new habitat… but also the species is quite important for the ecosystem,"she said.

Kākahi are classed as at-risk by the Department of Conservation and are in decline.

Amber McEwan, Victoria University kākahi researcher and freshwater ecology scientist, said it’s not known how many New Zealand freshwater mussels there are around the country, but young mussels are hard to find in many of the areas they dwell.

Degrading water quality is one reason behind their decline, she said, believing the next decade will be critical for intervention to stop the species from reaching a threatened status.

This weekend's relocation is the start of an ongoing study for Ms McEwan, who will be monitoring how successful moving mussels to a new, suitable home is for boosting their survival.

"We’re going to tag all the kakahi with external microchips… to work out what it is they need… and just how we can manage translocations in the future cause hopefully we’ll be doing a lot more," she said.

Studying the mussels in their new home, the upper lake at Zealandia, will provide valuable information for others attempting projects to improve the survival of kākahi, she said.

Several iwi are involved in the project, with the species a taonga (treasure) that used to be an important food source for Māori.

Taranaki Whānui attended the mussel collection at Lake Kohangapiri with flax kete (baskets) made for the event, to hold the mussels before they were put in buckets for acclimatisation.

Harmony Wright, one of the kākahi relocators, said it was a good experience to be part of.

"It's our first time seeing kākahi," Perzia-Rose Wright said.

Te Āti Awa Taranaki Whānui trustee Holden Hohaia, of Ngāti Kuri descent, said iwi want to rejuvenate the mauri (essence) of the Kaiwharawhara Stream, with Zealandia's waters forming part of the top catchment.

"It's awesome. One of the opportunities we're really keen to explore is whether we can re-establish this taonga so that it's so abundant that we can actually harvest it for kai," he said.

"Who knows, there might even be an opportunity there to harvest it commercially if it's plentiful enough."

The transferred mussels will spend 10 days in quarantine at Zealandia before being released into the upper lake, where it's hoped they’ll get to work cleaning up their new home.