An impressive conservation effort has seen the successful relocation of more than 1400 native fish and koura during construction of the Huntly section of the Waikato Expressway.
The construction is a massive undertaking and involves creating 15km of four-lane expressway, 3million m3 of earthworks, over 100ha of forest, bush and wetland enhancement, and permanent protection of a sacred lagoon and two pā.
John Turner, WSP Opus Technical Principal Ecology, says that protection of the local environment is a crucial component of the project, with the Huntly section requiring the creation and realignment of several streams, rivers, and wetlands to accommodate the footprint of the new expressway.
Turner says that surveys carried out by freshwater ecologists showed that the waterbodies that would be impacted by the Huntly construction provided habitat for a diverse range of native and endemic (only found in New Zealand) freshwater fish species and a crayfish (koura) species. To comply with resource consent conditions these native species needed to be captured and translocated to a new location before construction work could commence.
“WSP Opus ecologists worked closely alongside RiverLake Ltd, the wider Fulton Hogan - HEB Joint Venture construction team, the NZ Transport Agency, and local kaitiaki representatives to undertake the fish translocation of over 1400 native and fish and koura to suitable nearby natural or restored habitats in 2016, with many more translocated in 2017.”
Of the eight species moved, four are rated by the Department of Conservation as having a conservation status of At Risk- Declining and at risk of becoming Threatened. These included the longfin eel, the ‘whitebait’ species giant kokopu and inanga, and the black mudfish - a species unique to the area. The other native species included the Cran’s bully, shortfin eel, banded kōkopu, and koura.
Rare and unexpected
It was during the translocation that things got even more interesting.
“One of our ecologists discovered a population of at least 17 black mudfish in a drain near the expressway. The black mudfish are amazing creatures, they can survive out of the water, sometimes for several months, when their wetland habitat dries out over summer. They keep moist by burrowing under tree roots or into mud or damp leaf litter and lower their metabolism. When the water returns they immediately wriggle back into life.”
This species is endemic and only found in the Waikato, Auckland, and Northland regions. While the species used to be more widespread, habitat loss, reductions in water quality, and predation by pest fish are thought to have reduced their range.
This meant a change in plan. Originally the team has planned to assist a local farmer with drain cleaning, however, once the rare black mudfish were discovered, a unanimous decision was made to fence the waterway off and the riparian area enhanced with over 1300 voluntarily planted native plants.
“Black mudfish used to be more widespread, however, habitat loss, reductions in water quality, and predation by pest fish are thought to have reduced their range. This work has provided important protection for this population of black mudfish.”
Turner says it was heartening to see the construction partners so dedicated to ensuring wildlife were protected from the impacts of the project, both during the translocation of native species and the positive outcome for the black mudfish.
“At WSP Opus we’re focused on creating what matters for future generations. That means we take a holistic approach to our projects to ensure that the built environment is in harmony with the natural environment.”