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Environment Agency warns of dangers of releasing ornamental fish into the wild

Goldfish and koi carp can affect course fish populations

People looking to release unwanted pet fish into local ponds and lakes are urged to find alternatives as the Environment Agency warns of the devastating impact this can have on native species and ecosystems.

The plea follows recent incidents where goldfish and koi carp have been caught by anglers, despite the angling clubs concerned never having introduced them into their ponds. Some of these ponds have gone on to suffer from major disease outbreaks, killing hundreds of fish.

Ornamental fish such as goldfish and koi carp can carry disease and parasites which can have a devastating effect on coarse fish populations and have major commercial impacts on fisheries. They should be kept in garden ponds and not transferred into the wild.

Jerome Masters, fisheries technical officer at the Environment Agency said:

“People don’t see the dangers, but this seemingly harmless thing to do is anything but. A disease carried by koi carp, the koi herpes virus, has the potential alone to wipe out all the carp in a fishery. If you have fish that you don’t want anymore, you could try getting them re-homed by contacting a local pet shop, garden centre or by placing an advert in the press or online.

“Releasing fish into the wild without getting consent from the Environment Agency is an offence under the Salmon and Freshwater Fisheries Act.”

Not only can diseases have a devastating impact on coarse fish, amphibians are also affected. The introduction of species such as goldfish into ponds not only increases the severity of diseases for amphibians but also greatly reduces the variety of the species living in the pond.

Goldfish and koi carp can also interbreed with crucian carp, a threatened species, leaving ponds with hybrid populations.

Some smaller aquarium species such as sunbleak and topmouth gudgeon, can become invasive, outcompeting and outnumbering native fish, and devastating the local ecosystem.

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