• Goldfish

    (Carassius atratus)

    The Goldfish is one of the first invasive species to reach North America. Originating in eastern Asia, it was first kept as a pet in China and has since been sold around the world for use in aquariums, ponds and water gardens. It was brought to North America in the 1600s and was established in New York ponds by 1842.

    Found wild in quiet areas of ponds, streams and pools in urban and suburban areas across Ontario, Goldfish are able to tolerate fluctuations in water temperature and oxygen levels. Goldfish do not compete well with some native species in healthy ecosystems, but in degraded conditions it may threaten some native species due to its tolerance of poor water quality. Goldfish typically live for 6 to 7 years, although it can live as long as 30 years and grow up to 40 cm in length and 3 kg in weight. Goldfish are closely related to the Common Carp (Cyprinus carpio), which it has hybridized with leading to complex crosses of the two species.

    Control methods include physical removal in small and shallow water bodies and lowering of water levels or draining of water in ponds.


    Introduced around the world, Goldfish are established in all the Canadian provinces and all the American states, except for Alaska. Ontario has established populations on the north shore of Lake Erie, the west end of Lake Ontario and in other water bodies across the province.

  • Identification

    • Goldfish have elongated, stout bodies, typically reaching up to 12-25 cm in length and 100-300 g in weight.
    • Their colouring ranges from the typical bright orange to olive green to creamy white, with wild populations typically ranging from olive to grey.
    • They have large heads and eyes.
    • Goldfish have a long dorsal fin and a short anal fin, both with a single stout spine with a serrated trailing edge, as well as a deeply forked tail.
    • The mouth is small without trailing whiskers (barbels).
    • Goldfish are differentiated from other Asian carp (cyprinids) by its two serrated spines — the other species have non-serrated spines. The Common Carp also has two pairs of barbels on the upper jaw while the Goldfish has none.


    • Little is known about the ecology and impacts of Goldfish on North America’s water bodies, but the behaviour of Ontario populations suggest Goldfish may reduce the province’s biodiversity.
    • Due to its varied diet of snails, small insects, fish eggs and young fish, Goldfish are potential competitors with and predators of native fish species.
    • Goldfish increase the cloudiness of water bodies by stirring up mud and other matter when feeding, which can affect the growth of aquatic plants.
    • Goldfish are most successful in degraded habitats.
    • Goldfish can produce large populations under some situations.
    • Goldfish also carry harmful diseases such as Koi Herpesvirus, which can harm native fish populations.

    How can you help?

    • Learn to identify Goldfish and how to prevent its spread to other water bodies.
    • Do not release Goldfish or any other live fish into Ontario’s water bodies. Return or donate unwanted aquarium fish to a pet store or local school.
    • Inspect your boat and equipment and remove any plants, animals or mud before leaving a water body.
    • If you catch or observe a Goldfish or other invasive species, please contact the Turtle Island Invaders hotline at 1-844-872-2348 (1-844-TRACE-IT) toll-free or report the sighting to your local Lands or Natural Resources officer.
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