Ling, NicholasRowe, KatRoche, Ben2026-06-182026-06-182026Ling N., Rowe, K., Roche, B. (2026). Pest Fish Removal by Boat Electrofishing, Western Springs Lake - Te Wai Orea, February 2026. ERI Report No. 181. Client report prepared for Auckland Council. Environmental Research Institute – Te Tumu Whakaora Taiao. Division of STEM, University of Waikato. Hamilton, New Zealand. 25pp.https://hdl.handle.net/10289/18380Invasive exotic fish species were removed from Western Springs Lake Te Wai Orea by boat electrofishing in February 2026. Over five days, a total of 372 fish (252 goldfish, 43 koi carp, 77 brown bullhead catfish) totalling 509.6 kg were removed from the lake. These were the only exotic species captured or observed. Eels were abundant in the lake, and three smaller native fish were also captured (īnanga, common smelt, common bully). Due to targeted fishing effort in areas frequented by fish rather than employing a randomised sampling method, and varying electrofishing pulsator settings to target particular species, a reduction in catch per unit effort (CPUE) was not observed for the two less common species (carp and catfish). However, a reduction in CPUE was observed for goldfish, and analysis of goldfish catch data by the Leslie plot method estimated 78% removal of this species from the lake. Goldfish catch rate declined from a peak of 18.7 fish per hour on day one to three fish per hour by day five. Most goldfish and catfish were captured in weedy habitat in Pumphouse Bay at the south-eastern end of the lake. Goldfish and koi carp were also associated with marginal beds of papyrus sedge (Cyperus papyrus) and also occurred in shallow bays on the western side of the lake. Few fish were captured or observed in devegetated central areas of the lake.enReport