Summary report: Removal of Goldfish and Koi from the lakes of Studmaster Park, Wanneroo

Abstract

The freshwater fishes of south‐western Australia are highly endemic to the region (~82% found nowhere else) and have been impacted by a number of stressors including habitat and water quality decline and introduced fishes (Morgan et al. 2011). The rate of introduced fish species detected in wild systems in the region has increased alarmingly over the past decade (Beatty & Morgan 2013). Introduced freshwater fishes are known to have potentially severe and unpredictable detrimental impacts on aquatic ecosystems and once established (i.e. population that is self‐maintaining) are often difficult or impossible to completely eradicate with control or containment the only viable option to mitigate their impacts. Koi (Cyprinus carpio) and Goldfish (Carassius auratus) are cyprinids that are native to central and south‐eastern Asia and are now relatively widespread in south‐western Australia (Morgan & Beatty, 2007; Hourston et al. 2014). The species were recently detected by the Friends of Yellagonga Regional Park in the lakes of Studmaster Park, Wanneroo. Goldfish and Koi are known to have negative impacts on water quality as their vigorous bottom feeding methods resuspends nutrients making them available to algae. It has also been demonstrated that significant growth of cyanobacteria is stimulated by the passage through Goldfish intestines thereby potentially exacerbating algal blooms. Recognisiing these potential impacts, the City of Wanneroo engaged the proponents to undertake an intensive fish‐out of introduced cyprinid fishes in the lakes of Studmaster Park. The current project aimed to determine (qualitatively and quantitatively) the native and introduced aquatic fauna present within the lakes of Studmaster Park and undertake an initial, intensive removal program of Koi and Goldfish