An estimated 40 million to 50 million goldfish inhabit the waters of Lake Ontario, threatening native species.

Millions of dollars, meanwhile, are being spent on trying to keep their cousins, the Asian carp, out of the Great Lakes. Scientists fear that the carp will outcompete native species for both food and space.

“Asian carp are definitely the number one priority species we’re trying to keep out of the Great Lakes system,” Becky Cudmore, a senior science advisor on aquatic invasive species at Fisheries and Oceans Canada, told CTV’s Peter Akman.

But while the carp are an emerging and growing threat, goldfish have already firmly established themselves in Canada’s waterways.

Tys Theysmeyer, the head of natural lands at the lakefront Royal Botanical Gardens, near Hamilton, Ont., says goldish populations have exploded in recent times. The source, he says, is people setting their pets free -- a simple act that’s decimating the ecosystem by shrinking food supply for native species.

"Populations of frogs, fish, turtles, salamanders -- they’re all significantly down," Theysmeyer explained.

40-50 MILLION! That’s how many goldfish researchers believe are in Lake Ontario. @FishOceansCAN says they are also now in most lakes, rivers and water reservoirs across the country. Most from people dumping or flushing their pets.



Tonight on @CTVNationalNews pic.twitter.com/GysKpOjY2t — Peter Akman (@PeterAkman) September 14, 2018

The problem, however, isn’t confined to the Great Lakes.

In Western Canada, cities like St. Albert, Alta., near Edmonton, are facing their own goldfish invasions.

Crews have been spraying the city’s tiny Lacombe Lake recently with poison, killing everything in the water in the hopes of wiping out a massive population of invasive goldfish and koi.

“There’s a real threat to the city’s ecosystem if these species are able to enter our natural waterways,” the city’s environment manager, Christian Benson, told CTV News. “They are prolific breeders. They will breed a couple times a year.”

It’s the third time a massive cull has occurred in the area. In 2017 alone, moreover, more than 45,000 goldfish and koi -- equaling two tonnes of fish -- were removed from storm water facilities.

In the massive Great Lakes, however, such a widespread cull is not an option. So, while the government attempts to manage the goldfish population, they are simply asking people to stop dumping their pets.

With a report from CTV’s Peter Akman