The City of Ottawa is making preparations to euthanize a group of invasive goldfish residing in a stormwater pond in the Central Park neighborhood, although the exact population size is uncertain. In March, city personnel removed around 5,000 deceased goldfish from the pond in Celebration Park using nets and manual methods, as per a statement. Recently, the city has identified a new cluster of goldfish in the same pond. The surviving population is estimated to range between 500 and 1,000 based on a preliminary visual assessment, stated the city.
Councilor Riley Brockington, who represents the area, expressed astonishment at the significant number of fish found in the pond this year. Carleton biology professor Steven Cooke suggested that the actual goldfish population could surpass the city’s estimate and might already be in the millions, primarily consisting of newly spawned tiny fish.
Goldfish, originally from eastern Asia, are classified as invasive species and have spread across Canada and the mainland United States. In stormwater ponds, these fish multiply rapidly, outcompeting native species and disrupting aquatic plant growth by stirring up sediment from the pond bottom. Cooke emphasized the detrimental impact of goldfish on these ecosystems, highlighting their ability to dominate and suffocate the water.
The origin of the goldfish in the stormwater pond remains unknown. The city, following regulations from the Ontario Ministry of Natural Resources and Forestry, is mandated to euthanize invasive fish captured in such ponds. While netting can help reduce the population size, Cooke cautioned that it may not completely eradicate the population if even a single breeding pair remains.
Cooke suggested that using a fish-specific pesticide in closed water systems would be the most effective method for eliminating all fish. However, he acknowledged the challenges in obtaining public approval for such measures. Cooke emphasized the importance of preventing similar incidents by advising against releasing pet goldfish into natural habitats.