Thursday, August 18, 2016


It’s probably been portrayed on TV several times: letting a fishbowl or aquarium pet you can no longer care for go. Flushing a goldfish down the toilet probably means a quick end, but if you live closer to nature, like on a riverside, dumping your pet into the water there could have some unforeseen consequences.

Mashable Australia reports how freed goldfish have become a natural nuisance in Western Australia’s Vasse River. Why? Because once they get access to large amounts of food not controlled by a pet owner, these dainty little fishes can get a major growth spurt. And a larger size means greater consumption of resources.

This has been a problem on the Vasse for an astonishing 12 years, according to Murdoch University’s Centre of Fish and Fisheries. As goldfish grow and multiply, they compete against – and likely feed on – native fish populations as throw the river ecosystem way off balance. A CFF research team led by Stephen Beatty conducted a year-long study on how the goldfish have spread throughout the wild, and have published their findings on the “Ecology of Freshwater Fish” scientific journal.

Regarding their research, Beatty tells Mashable Australia that they were spurred by the alarming increase in goldfish and other aquarium fish now in the Vasse for the past 15 years. And who is the culprit? Obviously it’s the fish owners who thought that releasing their pets into the river and its connecting waterways was harmless, he says. These people don’t know that they may have brought about a localized catastrophe in nature.

Wild goldfish are omnivores, eating both aquatic plants and fish eggs, dirtying the water by constantly stirring up the riverbed sediments into a muddy storm. Their feeding habits are, for lack of a better word, destructive outside of the aquarium. Not only are the native species being robbed of feeding and living space, they may also fall victim to any disease the goldfish have that they’re not immune to.

That’s not all. When a goldfish is not confined in a closed space, they can grow ridiculously big. Beatty’s research group caught a 1.9 kilo goldfish monster, and they even electronically tracked another one swimming at an epic 230 kilometers for a year. This explains their rapid spread in the Vasse River.

Fortunately, the invaders have also revealed a weak point that the researchers can exploit. The goldfish have begun using a particular spot in the wetlands near the Vasse as a dedicated spawning ground where they multiply. Beatty proposes setting traps in the wetlands’ narrow opening to the river, in order to catch the goldfish whenever they travel there to spawn.

But all in all, the team believes that prevention is better than cure. Beatty enjoins all fish keepers not to set their animals free in the wild. Better to ask if the pet shops will take them back, he suggests, or to euthanize them by putting the fish in the freezer before taking them to the trash.

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