200 Kākahi (fresh water mussels) have been relocated to Zealandia in Wellington as part of a translocation and monitoring project.

Kākahi (fresh water mussels) are in decline in New Zealand, but 200 have been relocated to Wellington where their growth will be studied.

At wildlife sanctuary Zealandia, the Kākahi will be tracked by microchip and monitored by scientists.

Project lead researcher Amber McEwan said the monitored translocation on Thursday was the first of its kind in New Zealand.

LINTON MILLER/SUPPLIED Onlookers at Zealandia watch as Kākahi are released in the sanctuary's upper lake.

"It provides numerous learning opportunities for what's the best way to be able to translocate Kākahi."

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One of the country's lesser-known species, Kākahi are said to be more threatened than the little spotted Kiwi or Kōkako.

LINTON MILLER/SUPPLIED The monitored translocation on Thursday was the first of its kind for moving Kākahi in New Zealand.

The two species of Kākahi are considered as "At Risk – Declining" by the Department of Conservation

McEwan said researchers would watch them for at least three years.

"Hopefully that population will set itself up, will settle in, and start breeding."

Kākahi typically live for 50 years, and there was the potential to monitor them for their whole life.

There was nearly no risk the Kākahi would not survive the translocation and new environment, McEwan said.

The Kākahi microchips are attached to their shell using a type of superglue and dental cement the same material you would use to fill a tooth.

"Both of those materials have been trialled overseas."

Kākahi are beneficial for water quality and an important part of healthy freshwater ecosystems, she said.

"In the long-term, if there's a sufficient sustainable population of fresh water mussels, that will go a long way to filet out particles in the water like algi."

One Kākahi can filter about one litre of water per hour.

The Kākahi were collected from Parangarahu Lakes and Wairarapa Moana and transported to Zealandia, as part of their wider Sanctuary to Sea/Kia Mauriora te Kaiwharawhara programme.

McEwan's research was being conducted through Victoria University of Wellington.

Zealandia conservation manager Dr Danielle Shanahan said the highlight of the day was working with local iwi.

They worked closely with Taranaki Whānui, Rangitāne o Wairarapa, and Ngāti Kahungunu on the translocation project.

The young family of the iwi carried the Kākahi to the lake, she said.

"This is really important for us because it's one of our first projects as we start to focus on wetlands."