An experimental release of the rare and giant kōkopu whitebait at Tāwharanui Regional Park aims to establish two self-sustaining kōkopu populations to support the national conservation of the vulnerable species.
This will be the largest reintroduction of whitebait in New Zealand.
Councillor Penny Hulse, Chair of Auckland Council’s Environment and Community Committee, says protecting our native fish is important because they maintain healthy aquatic ecosystems.
“A diverse and thriving aquatic environment is important for supporting a rich natural array of plants and animals, many of which are found nowhere else in the world,” she says.
Giant kōkopu is one of only five whitebait species in Auckland. If they continue to decline, they will be at risk of extinction in the wild.
Auckland Council Senior Ranger Open Sanctuaries Matt Maitland says surveys showed giant kōkopu were no longer present in Tāwharanui Regional Park and various other sites across the region.
“There has been a significant decline in the numbers of giant kōkopu over the past two decades. Nationally, this is likely to have been a result of habitat loss, water quality decline and land-use changes,” Maitland says.
Tāwharanui Park staff, community partner Tāwharanui Open Sanctuary Society, along with technical support from NIWA have all contributed to the restoration of the park's waterways and enabling the return of the whitebait.
Work to improve conditions in Tāwharanui’s streams and wetlands has included reducing water use for the farm and nursery and water losses through leaky infrastructure, restoring wetlands and creating a passage through the pest-proof fence to allow fish out but stops pests coming in.
By offering a predator-free environment, giant kōkopu, which can reach up to 600mm in length and 2.7kg, will have a better chance of survival.
Matthew Bloxham, the council’s senior regional advisor for freshwater, says “after an absence of 30 years, we’re excited at the prospect of returning giant kōkopu back to Tāwharanui. This will be a test case for further Auckland releases and will tell us more about how previously modified freshwater environments can be restored for native fish species.”
Once the whitebait have been released into the sanctuary, they will be monitored to inform conservation efforts of giant kōkopu in the future.
If the reintroduction is successful, the council plans to release a further 120 adult fish into the sanctuary.
10,000 kōkopu will be released at Tāwharanui Regional Park this Saturday 10 June.