Having a pet goldfish is a rite of passage. Maybe you go on to get a pet hamster, or guinea pig, or cat/dog/rabbit/snake/turtle.
We all know it's a bad idea to free all those other pets. But did you know it's also a bad idea to free your pet goldfish?
WHAT, ARE YOU TELLING ME SOMETHING'S GOING TO EAT MY POOR BABY FINN IN THAT POND?
Other domestic pets aren't able to take care of themselves in the wild. Whatever common genetic traits they have with their wild cousins (such as wolves, or big cats, or wild rabbits) have long since been bred out of them as they were domesticated into human companion animals.
That's terrible and sad, of course. If the abandoned pet is lucky, they may get rescued and re-homed. If they're not so lucky, they end up dead (and possibly in painful, excruciatingly cruel ways).
Goldfish, however, are a different story.
GOLDFISH ARE ACTUALLY A SPECIES OF CARP
The scientific name is Carassius auratus, and yes--they're carp. If you've seen news reports about various freshwater carp invasions wherever you live, you probably know where this is going.
SO WHAT'S GOING ON IN AUSTRALIA?
Blinky the 4.2-lb. goldfish. That's what's going on.
Image: Murdoch University
These once-tiny carp may have conquered the world as pets, but they're not native to most of it. Since they're plucky and able to thrive anywhere there's freshwater, food, and a good temperature, they outcompete native species.
Not only that, but they bring unknown diseases (think about what you learned in American history class about Native Americans and smallpox blankets). On a more minor (but still harmful) note, they also stir up algal blooms due to their intrinsic feeding habits.
IF I'M NOT IN AUSTRALIA, WHY SHOULD I CARE?
Australia is just the most recent in a string of the exact same story of non-native goldfish being released into the wild and taking over. The moral of this story is, goldfish shouldn't be released into the wild ANYWHERE, EVER.
Here's a story from Colorado in 2015:
And here's an official UK government warning from 2015 as well:
This Smithsonian article focuses on Alberta, Canada's problem, but links to many other instances of goldfish invasion around the world:
Now back to our current problem in Western Australia, with plenty of photos of giant goldfish: