Goldfish owners have been warned not to release their pets into the wild as they are wreaking havoc on native species. The Mirror reports that according to new research, once out of the aquarium tank and let loose in open waters, they can turn into fat two-foot long "giants" that gorge on insects and tadpoles, outcompeting rivals and threatening biodiversity.
Lead author Dr James Dickey, of Queen's University Belfast, said: "Our research suggests goldfish pose a triple threat. Not only are they readily available, but they combine insatiable appetites with bold behaviour.
“While northern European climates are often a barrier to non-native species surviving in the wild, goldfish are known to be tolerant to such conditions. They could pose a real threat to native biodiversity in rivers and lakes, eating up the resources that other species depend on.”
They also contribute to poor water quality by mucking up the bottom sediments and uprooting plants. In addition, invasive species are one of the leading causes of global loss and the pet trade is responsible for a third of all aquatic invasive species.
Owners releasing unwanted creatures into the wild is a major problem and the goldfish is popular across the world, often awarded to children as a prize at funfairs. It was first domesticated over a thousand years ago and has since established non-native populations around the world.
The findings in the journal NeoBiota follow appeals to aquarium owners in Minnesota to stop releasing pets into waterways after several huge goldfish were pulled from a local lake. Officials in Burnsville, about 15 miles south of Minneapolis, said they can grow to several times their normal size.
As many as 50,000 goldfish were removed from local waters in nearby Carver County. They can easily reproduce and survive through low levels of oxygen during winter.
Ecological destruction caused by aquarium pets is a growing phenomenon. Carnivorous lionfish, native to the Indo-Pacific, were released by Florida pet owners after Hurricane Andrew in 1992.
They killed off dozens of Caribbean species, allowing seaweed to overtake the reefs. Goldfish have received less attention than other invasive species, but warnings have also been issued in Virginia and Washington state as well as Australia and Canada.
It is estimated as many as 200 million goldfish are bred each year. Most of these end up on domestic display.
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