Giant goldfish may sound like something straight out of a sci-fi movie, but according to Canadian authorities they’re very real—and quickly becoming a serious threat. They’ve recently been spotted in a number of Canada’s waterways and appear to be multiplying at an alarming rate.
So where did these monstrous goldfish come from? They’re the same tiny goldfish that humans, looking to be rid of pet-related responsibilities, have released into the water. They’re just bigger.
Free from the constraints of small bowls and habitats, these goldfish just keep growing—and growing, and growing. Eventually, they reach such massive sizes that they look like they’ve been hit with some sort of mutant growth ray. And now they’ve become an invasive species that’s wreaking havoc on Canada’s streams and rivers.
If the conditions are right, goldfish can simply continue growing as long as they have plenty of food and space. How big do they get? In 2022, an angler caught a 67-pound koi-carp hybrid, which was found swimming in Bluewater Lakes, France. (He named it Carrot.) Fisheries and Oceans Canada have also pulled massive goldfish from Lake Ontario’s Hamilton Harbour. They looked like miniature sea monsters.
The issue with giant goldfish is that they love to chow down on larvae, fish eggs, and aquatic plants. Their constant search for food ends up damaging their habitats while they bully other species, pick up and carry diseases, and create waters that are too cloudy from the dust they kick up for underwater plants to receive enough sunlight.
Another concern: female goldfish can spawn about 150,000 eggs a year — and they don’t even need a male to do it.
According to Brain Heise, a Thompson Rivers University professor who spoke to CBC News, the goldfish reproduce via cryogenesis, a mechanism that kickstarts egg development even without fertilization.
Ever wonder what happens to pet goldfish when they end up in our waterways? This one was pulled from Hamilton Harbour, where we’re studying this #InvasiveSpecies using acoustic transmitter tags. pic.twitter.com/GFCsBcIadV
— Fisheries and Oceans (@FishOceansCAN) November 30, 2021
So what’s the fix? According to Canada’s Invasive Species Center, just stop dumping fish in the water.
“It is essential to not release your pet goldfish into the wild to protect the integrity of natural ecosystems in Canada,” the Center stressed in a written statement. While giant goldfish might sound cool, it’s not sustainable for the environment. And, also, it’s kind of creepy.
Might want to correct the “cryogenesis” statement. From the linked BBC article, it’s gynogenesis ” They have a special process called gynogenesis in which the female will get the sperm from a different kind of minnow … to start the eggs developing, even though they’re not fertilized,” he said.”
I could see the winter weather freezing things a bit, but not that much.