Invasive goldfish are a ‘big problem,’ Fisheries and Oceans Canada said, because they take away key spawning sites from native fish species.
Have you ever wondered what happens when an unwanted pet goldfish gets released into the wild?
It turns out it grows and grows until it becomes a comically large version of its former self.
Fisheries and Oceans Canada posted photos to Facebook that show some of the humongous, large-bellied goldfish that were found in Ontario’s Hamilton Harbour.
“The ones my dad flushed 40 years ago must be as big as whales by now!” one person commented on the Facebook post. Others said they had seen bigger, adding that goldfish grow to adapt to their environment.
Don’t want your goldfish anymore? Rehome it on Kijiji
Monster-sized goldfish are taking over Alberta city (2017)
But the giant goldfish are taking away key spawning sites from other native fish species, the ministry said.
Spawning is a mass method of fertilization. Female fish release their eggs into the water, and the males release sperm to fertilize them. Spawning sites are key to the reproduction of native species, including the Northern Pike.
Invasive goldfish are a “big problem,” Fisheries and Oceans Canada wrote in a Facebook post last week. “In large numbers, goldfish can destroy aquatic habitats by tearing up aquatic plants for food and clouding the waters, which means less sunlight and less food for our native species. They can also thrive on toxic blue-green algae and may even aid in toxic algal growth.”
Hamilton is tracking invasive goldfish using acoustic tags — small sound emitting devices that allow for remote tracking in aquatic environments, like the Hamilton Harbour. Officials have found that the goldfish in the harbour are rapidly reproducing, quickly becoming classified as an invasive species.
Fisheries and Oceans Canada has a few recommendations to prevent introducing invasive species to waterways: “Learning about them, including how to recognize them, cleaning, draining and drying any equipment used in the water before storing it or moving it to a different body of water, never moving species, organisms or water from one body of water to another and keeping any aquatic plant or animal, such as live bait or pets from aquariums, out of the natural environment or sewers.”