Auckland Lake Undergoes Pest Fish Cull to Restore Ecosystem

Auckland Council is undertaking a major operation to remove pest fish from Te Wai Ōrea / Western Springs Lake, aiming to improve water quality and protect native freshwater species. The initiative, which began this week, focuses on removing koi carp and brown bullhead catfish that have negatively impacted the lake’s ecosystem.

The Problem with Pest Fish

Western Springs, a historically and culturally significant waterbody for Auckland’s mana whenua, has suffered from the effects of invasive fish species. Koi carp, known for their destructive feeding habits, stir up sediment and nutrients from the lakebed, leading to cloudy water and algal blooms. Brown bullhead catfish prey on native fish and kōura (freshwater crayfish), further disrupting the natural balance. Auckland Council explains that these species harm freshwater habitats when left uncontrolled.

Electrofishing Technique

To address the issue, the council is employing electrofishing, a technique that uses pulsed electric currents to temporarily stun fish. This allows teams to safely collect the pest species for removal. According to 1News, this is the first time Auckland Council has used an electrofishing boat, having previously tried other removal methods. The team has already caught Koi weighing up to 14kg.

Protecting Native Species

The operation is designed to minimize harm to native species, including three eel species (tuna) that inhabit the lake. Researchers can recover native species unharmed and return them to the lake although euthanizing the pest fish. A proposal is also underway to declare Western Springs an eel sanctuary, highlighting the importance of ecosystem protection. Auckland Council emphasizes the importance of protecting taonga species and restoring balance within the lake.

Responsible Pet Ownership

Authorities have noted that many of the unwanted fish found in the lake are former pets released by owners who can no longer care for them. Experts warn against releasing unwanted pets into waterways, as they are ill-equipped to survive and can disrupt the natural ecosystem. The council recommends finding new owners, returning the fish to the pet store, or contacting fish rehoming groups like Auckland Fish Rescue or North Shore Turtle Rescue.

From Fish to Fuel

The removed pest fish are not simply discarded. They are sent to a plant where they are processed into bio-ethanol, a renewable energy source. This sustainable approach minimizes waste and provides a beneficial use for the removed species.

Looking Ahead

The pest fish removal operation at Western Springs Lake represents a significant step towards restoring the health and biodiversity of this important Auckland waterbody. By addressing the issue of invasive species, the council aims to ensure the long-term sustainability of the lake’s ecosystem for future generations.