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Source: Auckland Council

A conservation project to create a secure future for New Zealand’s rarest whitebait species, the shortjaw kōkopu, is getting a helping hand to increase the fish presence in the wild.

Auckland is home to just a handful of populations of shortjaw kōkopu (Galaxias postvectis) and all but two are found in the Waitākere Ranges.

The Huia catchment is about to become home to up to 800 fingerlings (baby kōkopu). Bred in captivity, the fish will be released into streams feeding the Upper Huia Reservoir.

Planning, Environment and Parks Committee Chair Councillor Richard Hills says freshwater fish are one of the most endangered groups of vertebrates on earth.

“Developmental impacts have degraded kōkopu habitat,” says Hills.

“Establishing more wild populations is an important step in the conservation of this species, and acts as an insurance policy for their ongoing survival.

“We hope this fish release will ultimately result in a healthy, self-sustaining population taking hold, so the species can fulfil its important natural role in the ecosystem. I acknowledge and thank everyone involved on this important work,” adds Hills.

Auckland Council’s Senior Regional Freshwater Advisor Matt Bloxham says the shortjaw kōkopu occupy streams in regional parkland and are usually less vulnerable to urban impacts than some of their kōkopu buddies.

“However, major storm events, which we can expect more of under predicted climate change scenarios, have the potential to annihilate whole populations, even within pristine regional parkland.

“We saw this in 2023, when one of the key shortjaw kōkopu streams was destroyed by cyclone Gabrielle in Piha,” adds Matt. 

In preparation for the species’ return to the wild, the fingerlings have – in a world first – been bred from scratch by Manāki Whitebait, using parent stock from the Waitākere Ranges. They were transported to the dam site in a fish tanker before being transferred by boat, then carried upstream to the release sites by staff.

“The release has been many years in the planning and is a significant milestone. The intent of the release is to broaden the resilience and distribution of the species in the Waitākere Ranges,” says Matt.

“Boosting the population of these fish is important to their survival and to the ecosystem.

“It is no longer possible for the kōkopu to reach these catchments naturally because of the presence of the reservoirs’ dam walls. Once repatriated, the recovery becomes easier as their whole life stages are retained in fresh water, rather than being split between ocean and fresh water.

“And they are better buffered against major weather events as they are less likely to be displaced.

“The work we do to save threatened native species like the kōkopu, giving them a fighting chance in our changing world, is rewarding,” explains Matt.

The project will be monitored for several years to assess how well the species take to their new home and whether the fish are reproducing above the reservoir.

This project is a great example of collaborative conservation work between Auckland Council, Manāki Whitebait, Watercare, Te Kawerau ā Maki and NIWA.