Goldfish

Description

Goldfish, a seemingly harmless pet from eastern Asia, has become one of the most widespread invasive fish species in North America. Due to their popularity as a pet species and adaptability to various environmental conditions, they have established populations in numerous water bodies across Canada and the United States. Goldfish can grow significantly larger in the wild than in captivity, with their feeding habits and reproductive capabilities posing threats to native species and habitats.

  • Scientific name: Carassius auratus

  • Common name(s): Goldfish

  • French common name: Carassin

  • Regulatory status: Goldfish are considered invasive in all Canadian provinces and many regions across the US where they have been introduced.

Wild Goldfish

Goldfish © Cameron Chevalier, some rights reserved (CC BY-NC)

Habitat

Goldfish prefer calm, vegetated waters such as ponds, streams, and lakes. They are often found in urban or suburban areas where they’ve been released by owners. They thrive in environments with low dissolved oxygen levels and can tolerate a wide range of water temperatures. Their resilience to poor water quality makes them a formidable invasive species.1

Identifying Features

  • Size: Adult goldfish can range from 12 to 40 centimeters in length.

  • Colour: Wild populations often lose the bright orange of domestic varieties and instead exhibit olive to grey coloring.

  • Body: Elongated bodies with a large head and eyes, and a small mouth without barbels.

  • Fins: A long dorsal fin with a single stout, serrated spine and a deeply forked tail fin.

Impacts

Goldfish can significantly impact local ecosystems through:

  • Competition: They compete with native fish for food.Predation: As predators, they consume young fish and other aquatic organisms , including snails, small insects, and fish eggs.

  • Habitat Disruption: Their feeding behavior can increase water turbidity, affecting aquatic plant growth.

  • Disease Transmission: They are capable of carrying diseases like koi herpesvirus which poses risks to native fish populations.

Spread and Control

Goldfish have been introduced globally, primarily through the aquarium trade and by being released into the wild intentionally or unintentionally by pet owners. Releasing a pet into the wild is not a good option – it’s illegal, dangerous to the environment and inhumane as many goldfish do not survive due to predation and environmental conditions The Goldfish’sability to reproduce quickly and adapt to different conditions has helped them establish populations throughout Canada,

What You Can Do:

  • Don’t Let it Loose – Do not release aquarium fish into natural water bodies. Find safe and humane alternatives to releasing pets and aquarium contents into waterways.

  • Educate others about the impacts of invasive species and proper rehoming of unwanted pets.

Reporting

If you encounter a goldfish or other invasive species in the wild, you are encouraged to report it to local authorities or through invasive species reporting programs to aid in management and control efforts.

For further information on identifying and managing goldfish invasions, and to learn more about their impacts on native ecosystems, visit the following resources:

1Boston, Christine & Larocque, Sarah & Tang, Rex & Brooks, Jill & Bowman, Jennifer & Cooke, Steven & Midwood, Jonathan. (2023). Life outside the fishbowl: Tracking an introduced population of goldfish (Carassius auratus) in an embayment on the Laurentian Great Lakes. Journal of Great Lakes Research. 50. 102253. 10.1016/j.jglr.2023.102253.

Invasive Species Categories

Stop The Spread: Report Invasive Species

How to Prevent and Manage Invasive Species

The Impact of Invasive Species on Canada’s Ecosystems and Economy

Invasive Species Resources: Guides, Manuals, and Best Practices