Pet goldfish released into the wild are wreaking havoc on native species because of their insatiable appetites and thuggish behaviour, new research suggests.
Once let loose in open waters they outcompete rivals and threaten biodiversity by gorging on insects and tadpoles.
It is for this reason that scientists warn that taking the ‘humane option’ of trying to save a goldfish may lead to catastrophic consequences for the planet.
The study’s lead author Dr James Dickey, of Queen’s University Belfast, said: ‘Our research suggests goldfish pose a triple threat.
Pet goldfish released into the wild are wreaking havoc on native species because of their insatiable appetites and thuggish behaviour, new research suggests (stock image)
‘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.’
The goldfish also contribute to poor water quality by mucking up the bottom sediments and uprooting plants, researchers added.
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 animals into the wild is a major problem.
The goldfish was first domesticated over a thousand years ago and has since established non-native populations around the world.
The research team compared the pet to the white cloud mountain minnow — a species with a limited invasion history to date.
Once let loose in open waters goldfish outcompete rivals and threaten biodiversity by gorging on insects and tadpoles (stock image)
They assessed the ecological impacts and risks of potential pet trade invaders based on availability, feeding rates and behaviour.
Goldfish were found to be voracious — consuming much more than the white cloud mountain minnow or native species.
In terms of behaviour patterns goldfish were also found to be much braver, which is a trait linked with invasive spread.
Dr Dickey said: ‘Our research highlights that goldfish are high risk, but we hope the methods developed here can be used to assess others in the pet trade across Ireland and further afield.
‘Readily available species are most likely to be released, so limiting the availability of potentially impactful ones, alongside better education of pet owners, is a solution to preventing damaging invaders establishing in the future.’
The findings 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.
Goldfish, which belong to the carp family, can easily reproduce and survive through low levels of oxygen during winter.
The findings 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
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.
In 2013, Scientific American reported that researchers trawling Lake Tahoe netted a goldfish that was nearly 1.5ft (46cm)long and weighed 4.2lb.
It is estimated that as many as 200 million goldfish are bred each year, with most ending up on domestic display.
The research has been published in the journal NeoBiota.
INVASIVE SPECIES ARE THOSE INTRODUCED IN A REGION TO WHICH THEY ARE NOT NATIVE
An invasive species is one – be it animal, plant, microbe, etc – that has been introduced to a region it is not native to.
Typically, human activity is to blame for their transport, be it accidental or intentional.
Hammerhead flatworms have become invasive in many parts of the world. They feast on native earthworms, as shown
Sometimes species hitch a ride around the world with cargo shipments and other means of travel.
And, others escape or are released into the wild after being held as pets. A prime example of this is the Burmese python in the Florida Everglades.
Plants such as Japanese knotweed have seen a similar fate; first propagated for the beauty in Europe and the US, their rapid spread has quickly turned them into a threat to native plant species.
Climate change is also helping to drive non-local species into new areas, as plants begin to thrive in regions they previously may not have, and insects such as the mountain pine beetle take advantage of drought-weakened plants, according to the National Wildlife Federation.