Giant goldfish were found in a Minnesota lake last week. But the invasive species is a problem in Lehigh Valley waterways, too

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In this image provided by the City of Burnsville, Minn., a large goldfish caught in Keller Lake during a water quality survey is held, Friday, July 2, 2021. Officials in Minnesota say they're finding more giant goldfish in waterways, prompting a plea to citizens to stop illegally dumping their unwanted fish into ponds and lakes. The goldfish, which can grow to the size of a football, compete with native species for food and increase algae in lakes. (City of Burnsville via AP)

Have you ever thought you were doing something nice or helpful, but it turned out you were causing more harm than good?

Well, people across the country may be finding that out about themselves as officials from a Minnesota city are urging residents to stop releasing their pet goldfish into ponds and lakes, where they grow to super-sized proportions and wreak havoc on the local environment.

And the problem isn’t just in the Midwest — it’s right here in the Lehigh Valley, too.

Last week, officials in Burnsville, Minnesota asked residents to stop putting their pet goldfish in area waterways after “groups” of football-sized goldfish were found in the city’s Keller Lake.

“Please don’t release your pet goldfish into ponds and lakes,” said a post on the city’s Twitter page. “They grow bigger than you think and contribute to poor water quality by mucking up the bottom sediments and uprooting plants.”

Since the post, the issue has become widely popular with social media users, who have asked how the fish taste battered and fried and why goldfish don’t grow as large while in home aquariums. One person shared a photo of a bald eagle snatching a goldfish from the lake.

Goldfish, native to eastern Asia and arriving in the U.S. in the 1600s, have been reported invasive across the country by every state except for Alaska, according to Pennsylvania’s Field Guide to Aquatic Invasive Species. In the commonwealth, they’re established in Northampton, Erie and Philadelphia counties.

While goldfish are not included on a list of aquatic invasive species on the state Fish and Boat Commission website, they are featured on the PA AIS, an app state conservationists uses to identify, report and catalog non-native animals and plants. It’s also available to the public.

Zachary Rudd, a waterways conservation officer for the state Fish and Boat Commission, said he doesn’t hear much about goldfish in the county’s waterways when talking to anglers.

“I’m sure that it is happening to some extent, but I would say it’s not a huge amount of that happening currently,” Rudd said. “Although goldfish may not be at the forefront of my mind, we do have a couple of other aquatic invasive species within the county that have really started to crop up.”

The New Zealand mud snail, as well as another invasive species of fish, snakeheads, are cropping up in the Lehigh Valley, he said.

“That is kind of one of concern, just because it’s spreading very easily,” Rudd said of the snail. “So from an enforcement standpoint, if there’s people that are using certain bait fish, we don’t want them released into the water body.”

Anglers should dispose of their bait properly — not just dump them into a body of water.

“Probably a lot of this is inadvertent, and some of it is probably pretty innocuous, and that people will have pets and instead of being, kind of, heartless in a sense and and either disposing of the goldfish by digging a hole and burring them, they think they’re doing the right thing by releasing them,” Rudd said. “For the ecosystem, that is not the best thing.”

And, although officials focus on education, residents can face legal repercussions.

Transporting or releasing one of the species that known as an injurious species in the commonwealth can be charged with a misdemeanor, Rudd said. Meanwhile, transporting or introducing a species that’s not listed as native within the watershed — like a goldfish — can garner a $75 fine.

“Be mindful about what you’re moving, what you’re doing and that sort of thing,” he said. “Because a lot of these, once they get introduced into the waterways, they can be extremely difficult to eradicate, if at all, just like we’ve learned with the spotted lanternfly and many other invasive species before, once they’re introduced, it’s extremely difficult to manage.”

Goldfish, which are members of the carp and minnow family and live in fresh water, can be intentionally introduced for ornamental purposes in ponds and fountains, according to the guide.

“Many introductions of goldfish were also due to their use as live bait,” according to the guide. “In addition, goldfish are often released into the wild by pet owners not realizing the environmental repercussions of setting the fish free.”

The size of a goldfish’s environment will affect its growth, with typical sizing between 4 to 8 inches. However, it could grow to a maximum length of 23 inches.

They don’t always have their golden color, either.

“While goldfish were mostly golden in color one thousand years ago, they now come in a variety of colors, including orange, yellow, white, black, silver, olive-green or greenish-brown and combinations of these colors,” according to the guide. “When found in nature, goldfish are most often a shade of green, brown or gray.”

While they prefer a habitat with a muddy bottom and thick vegetation, they can tolerate pollution and temperature fluctuations.

And, with a lifespan anywhere from five to 10 years in captivity but up to 25 years in the wild, it’s something to consider the next time someone wins a goldfish at a fair or decides to purchase one from a local pet store.

Morning Call reporter Molly Bilinski can be reached at

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