One of Auckland’s most loved and historic waterbodies is getting a much-needed helping hand.
This week, Auckland Council’s Environmental Services and Healthy Waters and Flood Resilience teams will carry out a major pest fish removal operation at Te Wai Ōrea / Western Springs Lake, an important step toward improving water quality and protecting native freshwater species.
Western Springs is no ordinary lake. Known to mana whenua as Te Wai Ōrea, it is the original water source for Auckland and has long been a place of cultural, ecological and community significance. While the city has grown beyond relying on the springs for drinking water, the lake remains a treasured green space and an important freshwater ecosystem.
Over time, however, pest fish such as koi carp and brown bullhead catfish have taken a toll. These species feed by rooting around in the lakebed, stirring up sediment and nutrients that cloud the water and fuel algal blooms.
Matthew Bloxham, Auckland Council’s Senior Regional Advisor Freshwater says koi carp are well known for their negative effects on water quality.
“When left uncontrolled, their feeding disturbs lakebed sediments and harms freshwater habitats. Reducing pest fish numbers is a proven way to help lakes recover.”
Catfish add further pressure by preying on native fish and kōura (freshwater crayfish), and by competing with native species for food.
Western Springs is also home to a regionally significant tuna (eel) fishery, with three species of eel present. Because of this, there is a proposal to declare the lake an eel sanctuary, making protection of the ecosystem even more important.
“This is about looking after taonga species and restoring balance,” says Bloxham.
“Cleaner water supports healthier eel populations and stronger native biodiversity overall and reduces the botulism risk.”
The operation will be led by a specialist team from the University of Waikato, using New Zealand’s only electrofishing boat of its kind. The technique uses a pulsed electrical current to temporarily stun fish, allowing pest species to be safely collected while native species, including eels, are returned unharmed.
“Electrofishing allows us to capture all sizes and species with minimal harm,” says Associate Professor Nick Ling from the University of Waikato.
“Unlike nets or traps, it’s highly effective while still being safe for native fish, which recover quickly and can be released back into the lake.”
Pest fish removed during the operation will be humanely euthanised and taken off-site to be turned into compost.
The work is scheduled for the week of 9–13 February. Water levels will be temporarily lowered from Sunday to improve the effectiveness of the operation, and parts of the lakebed, particularly at the western end, will be visible during this time.
Cultural monitoring will be carried out throughout the week by mana whenua (Te Ahiwaru).
Councillor Richard Hills says the project reflects a long-term commitment to protecting one of Auckland’s most iconic natural spaces.
“Western Springs is a place many Aucklanders have grown up with,” he says.
“This work shows we’re serious about restoring the lake, supporting native species, and doing the right thing for future generations. It’s good environmental stewardship and it’s the right thing to do.”
With no upstream source for reinvasion, ongoing management and community care, such as not releasing unwanted pet fish, gives Te Wai Ōrea a strong chance to remain a healthy, largely native freshwater ecosystem into the future.