Feral Goldfish are Invading the Great Lakes

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What if I told you there was a species making its way into the Great Lakes that could devastate local ecosystems?

Sounds ominous right?

What if I told the animals everyone was worrying about was a goldfish?

Sounds less ominous now.

But it’s true.

Goldfish are making their way into local waterways and causing havoc. 

Most people think of goldfish swimming around little glass bowl aquariums but in the wild goldfish can grow to impressive sizes and can reproduce quickly.

“None of that is ecologically or aesthetically desirable,” says Hugh MacIssac, a researcher in Windsor.

Feral goldfish have been a growing problem in North America for a while but their numbers are starting to grow.

The exact reason for their sudden growth is not known but one speculation is that invasive carp species are being better controlled so goldfish are taking their place. 

Also, people are dumping unwanted fish in stormwater ponds which can overflow and connect to greater waterways. 

Most people think of goldfish as the small aquatic animals many kids have for their first pet. But National Geographic reports that these are hardy fish that can grow up to 16 inches when in the wild and live up to 40 years. 

To make matters worse they are essentially the perfect invasive species. They can live in a variety of temperatures and oxygen conditions and they reproduce faster than predators can take them out. 

Previously, not much was known about wild goldfish but researchers are studying them and figuring out how to manage them. Christine Boston at Canada’s Great Lakes Laboratory for Fisheries and Aquatic Sciences in Ontario is studying the fish and how to make sure they don’t get out of control.

They were able to capture 19 fish and placed acoustic tags on them so they could follow the fish and learn their habits. 

Soon they noticed patterns emerging.

They overwintered in the same areas each year, and returned to the same spawning habitat each spring,” says Boston.

Boston also found they would gather in the same area before moving to spawning grounds.

Maclssax says this gives them an opportunity to manage the fish.  “If we can geolocate where they are, we can use selective fishing to eliminate or reduce them,” he said.

He explained the ‘Judas Fish” technique where the tagged fish mix in with others and allow them to target the whole group of them.

It is similar to how invasive carp are managed. 

“We’ve seen significant drops in invasive carp populations, so we know control works,” says Boston. “If we can get our hands on them, we can make a real dent in their population.”

The best place to start managing them is to Akko sure that they do not end up in the Great Lakes at all.

“Biologists must fight any perception that goldfish are harmless species when released into the wild,” says Anthony Ricciardi, who studies invasive species at McGill University.