If that trapped goldfish starts to lose its luster, think twice before tossing it into the river or canal – the creatures may look harmless, but their voracious appetites, tolerance for cold and habits for eating compared to native species can be catastrophic for local wildlife.
New research shows that goldfish consume much more than comparable fish in UK waters, eat more than other invasive fish and are also much more willing to aggressively target other competing species.
That means goldfish pose a triple threat, according to Dr James Dickey of Queen’s University Belfast, the study’s lead author.
“Not only are they readily available, but they combine insatiable appetites with daring behavior,” he said. “While Northern European climates often present a barrier to non-native species surviving in the wild, goldfish are known to be tolerant of such conditions and can pose a real threat to native biodiversity in rivers and lakes, eating the resources of which other species depend On.”
The study couldn’t measure whether more goldfish were being released into the wild by pet owners who bought new fish during the lockdown, but anecdotal reports have suggested this could be the case.
“While our investigation has not focused on whether this problem has worsened since the lockdown, there is reason to believe that it has, or at least will be,” said Dickey.
“There have been recent news reports of finding released Amazon catfish in Glasgow, which may be related. There may also be a delay, and it may not be until this summer, when normality resumes and people want to travel, for example [and leave their pets behind]that we are starting to see the effects.”
The study, published Wednesday in the journal NeoBiota, examined the two most-traded fish species in Northern Ireland: goldfish, an invasive species around the world, and the white cloud mountain minnow, which remains much of an invasive foothold on the island. ground. Both species are members of the carp family and are native to East Asia.
The researchers have developed a new method to assess and compare the effects of both species by looking at availability, feeding rates and behavior. By these standards, goldfish far outnumbered white cloud minnows and were shown to be able to devastate native wildlife populations in British ponds, rivers and streams.
Goldfish prey on tadpoles and other small fish when released into UK waterways, disrupting natural ecosystems.
In the US, goldfish have been found to exceed 30 cm (1 ft) in length in some waterways due to their adaptability.
Many pet owners feel they are acting humanely by releasing their goldfish into the wild, but Dickey warned that doing so was destructive.
Another way to limit damage, the study said, would be for pet stores to stock more alternative varieties that don’t pose as much of an invasive risk.
“Goldfish are a high risk,” Dickey said. “Limiting the availability of potentially impactful [species, such as goldfish] in addition to better training for pet owners is a solution to prevent harmful invaders from settling in the future.”
Flushing an unwanted fish down the toilet is also a no-no, according to Dickey. But he said some pet shops would take fish back, although usually not with refunds, and there are websites such as Preloved.co.uk where they can be given away or bartered.