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Part of Invasive fish species

Goldfish and koi

These common ornamental fish can pose significant harm to aquatic ecosystems when released into the wild.

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Invasive fish species

Place of origin and introduction to Alberta

Goldfish (Carassius auratus) and koi (Cyprinus rubrofuscus) are common ornamental fish that can pose significant harm to aquatic ecosystems when released into the wild.

Goldfish and koi are native to eastern Asia. Both species have been introduced in Alberta as ornamental fish that have been released into waterbodies.

Over 100 locations of goldfish are known in Alberta, mainly in urban storm water ponds. Due to continuing illegal release of aquarium fish into the wild, more locations of goldfish in Alberta are found each year.

Koi fish have been illegally released into a few Alberta waterbodies as well. Koi fish were found in St. Albert in 2018 and have since been successfully removed by the city. In 2020, a repeated attempt to release koi fish into the same pond was stopped by confronting angler.

Identification

Goldfish

A small goldfish with limited gold colouring held beside a storm water pond

A small goldfish, with limited gold colouring, showing serrated first dorsal ray and first anal fin ray.

Goldfish, ranging from orange to silver, lined up on a measuring tape

As goldfish breed in the wild, they lose their orange colouring.

A koi fish and a silver goldfish placed lengthwise along a ruler

A colourful koi fish and silver goldfish from a storm water pond.

  • Plump and deep-bodied
  • Large head with terminal mouth
  • Gold-orange in colour, can also range from olive-bronze to silvery-white
  • Large scales, 25 to 31 along lateral line
  • Forked tail
  • Lack barbels on face
  • Distinguished by first dorsal fin ray and first anal fin ray being strongly serrated

Similar species: Prussian carp

Goldfish lose their orange colouration in the wild, making them indistinguishable from another invasive species in Alberta called Prussian carp. DNA analysis is needed to confirm the identification between goldfish and Prussian carp.

A Prussian carp, a fish species, laying sideways on a ruler

Prussian carp are indistinguishable from goldfish that have lost their orange colour in the wild.

A small goldfish with limited gold colouring held beside a storm water pond

Goldfish with limited or no gold colouring can easily be misidentified as Prussian carp.

Koi

A large orange koi laying on its side on a ruler

A large orange koi with barbels being measured.

A large white, orange and black Koi being held up

A large koi removed from pond in St. Albert.

  • Distinguished from goldfish by prominent barbels on chin
  • Adult typical length is 30 to 60 cm
  • Body is long and narrow
  • Vary largely in colour – often bright orange, can have black and white colour patterns

Reproduction

  • Goldfish and koi are prolific reproducers, allowing their populations to rapidly increase.
  • Female goldfish are ready to spawn within one year and can spawn up to 3 times per year. A single female goldfish can lay on average 500 to 1000 eggs per spawning period.
  • Koi are able to spawn as early as 3 years of age. A single large koi female can lay up to 100,000 eggs in a spawning period.

Issues

  • Both species are extremely hardy, rapidly reproduce, can tolerate low oxygen levels and poor water quality, where native fish cannot survive.
  • Both can carry pathogens capable of infecting other fish species.
  • Increase water turbidity with their destructive feeding habits, which reduces suitable habitat and available food for native fish.
  • Invasive fish response is extremely costly, difficult to manage, contain and remove once established.
  • Growth of cyanobacteria in goldfish intestines can increase risk of algal blooms.

Current management

  • Prevention is the best defence as there are no selective control measures. Prevention is prioritized through education on responsible fish ownership.
  • When feasible, manual removal through netting and angling can be used, but is labour intensive.
  • Pesticide treatment can be done as a last resort, but is often only feasible for use in isolated waterbodies, without other fish present.

Take action

Never release goldfish or koi into waterbodies. Never use goldfish or koi as bait, dead or alive. Penalties for introducing a fish into any waterbody other than where it was found can be up to $100,000 and/or a year in prison. See:

Be a responsible fish owner. If you are no longer able to take care of a fish, do not release it into the wild. Choose a responsible and humane way to end ownership:

  • Contact the retailer for advice, or for a possible return/surrender.
  • Give it to another aquarium or pond owner.
  • Donate it to a local aquarium society or school.
  • Talk to a veterinarian about humane disposal.

It is common practice to flush pet fish down the toilet, but this can introduce disease and parasites into waterbodies. Properly bury or dispose of deceased fish instead.

Report sightings of aquatic invasive fish:

By telephone: Aquatic Invasive Species Hotline
1-855-336-BOAT (2628)
Online via mobile or desktop: EDDMapS Alberta App

Report any unlawful activities to:

  • Report-a-Poacher phone line
    1-800-642-3800 (Toll free 24 hours a day, 7 days a week)

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