Bowled Over: What Happens To Goldfish When They’re Released Into The Wild

A study of aquatic invasive species reveals that goldfish are being released into the waters off Hamilton Harbour in Ontario, Canada, growing to a huge size.

The goldfish were pulled out of the harbor on the western tip of Lake Ontario at the end of November.

“Ever wonder what happens to a pet goldfish when it ends up in our waterways? This one was pulled from Hamilton Harbour, where we’re studying this aquatic invasive species to learn how it’s affecting our waters,” Fisheries and Oceans Canada posted online with accompanying images of bloated goldfish.

“By tracking these goldfish using acoustic tags, we’ve learned that they’re breeding in the harbor, targeting key spawning sites for native species like Northern Pike,” Canadian government agency said.

“This is a big problem because 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.”

The agency said most goldfish “likely end up in our waters after being released into local entry points like stormwater ponds, which is why it’s so important to never release any pets into the wild.”

In its online post, the agency encouraged people to learn more about how to prevent the spread of aquatic invasive species. 

Invasive aquatic species, whether introduced intentionally or accidentally, can spread quickly.

“They can establish themselves in our waters and spread rapidly when they don’t face natural predators or competitors,” the agency states on its website. “In recent years, the introduction and spread of aquatic invasive species has been much more rapid because of globalization, including increased international shipping, online shopping and travel.

“Prevention is the most efficient and cost-effective method of dealing with aquatic invasive species.”

The agency posted general measures to prevent the introduction and spread of aquatic invasive species, including:

• 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
• keeping any aquatic plant or animal, such as live bait or pets from aquariums, out of the natural environment or sewers.

“Under the federal Aquatic Invasive Species Regulations, it is illegal to introduce an aquatic species into a body of water where it is not native, unless authorized under federal, provincial or territorial law,” the government said.

Edited by Judith Isacoff and Kristen Butler