An initiative aimed at securing the future of New Zealand’s rarest whitebait species, the shortjaw kōkopu, was launched today in the Waitākere Ranges.

800 fingerlings were released into the Huia catchment in a collaborative effort between Kawera a Maki, Watercare, Manāki, and Auckland Council.

The young fish, bred in captivity, will be released into streams that feed the Upper Huia Reservoir in an initiative aimed at boosting the fish’s prevalence in the wild.

Chair of Auckland Council’s planning, environment, and parks committee Richard Hills highlighted the urgency of this initiative.

“Freshwater fish are among the most endangered groups of vertebrates on earth,” Hills said.

“Developmental impacts have severely degraded kōkopu habitats. Establishing more wild populations is crucial for the conservation of this species, serving as an insurance policy for their survival.”

Threats and resilience

According to Auckland Council’s senior regional freshwater advisor, Matt Bloxham, the shortjaw kōkopu primarily inhabit streams within regional parkland, rendering them less susceptible to urban development impacts compared with other kōkopu species.

However, Bloxham warned that extreme weather events, exacerbated by climate change, pose significant threats.

“We witnessed the devastation in 2023 when Cyclone Gabrielle decimated a key shortjaw kōkopu stream in Piha,” he recalled.

In a pioneering effort, the fingerlings were bred from scratch by whitebait preservation organisation Manāaki, using parent stock from the Waitākere Ranges.

These young fish will be transported to the dam site in a fish tank, transferred by boat, and then carried upstream to their release sites by staff.

“The release of these fingerlings has been meticulously planned over several years and represents a significant milestone,” Bloxham said.

“The goal is to enhance the resilience and distribution of the species within the Waitākere Ranges.”

Long-term monitoring and collaboration

Bloxham emphasised the importance of boosting the shortjaw kōkopu population for both their survival and the broader ecosystem.

Due to the presence of the reservoirs’ dam walls, the fish can’t naturally reach these catchments anymore.

Once relocated, the fish can complete their entire life cycle in freshwater, without the need to migrate between ocean and freshwater environments.

The project will be monitored for several years to evaluate the species’ adaptation to their new habitat and their reproductive success above the reservoir.

This conservation effort exemplifies collaborative work between Auckland Council, Manāaki, Watercare, Te Kawerau a Maki, and NIWA, demonstrating a unified commitment to preserving New Zealand’s unique aquatic biodiversity.