Experts Warn About Football-Size Goldfish Taking Over Lakes After Owners “Free” Their Pets

Now in most cases, a standard goldfish will tip the scales at little more than 8oz, at most; length-wise we’re talking 1-2 inches. They’re perfect for smaller fish tanks at home, as well as being easy to manage. But the giant goldfish that are wreaking havoc in Minnesota’s waters blow those numbers away. The creatures are absurdly large, some weighing about 4 pounds. That’s the equivalent of a laptop! And they’re leaving aquatic experts slack-jawed.

One of those experts spoke to the KARE 11 news station in July 2021 by the side of Keller Lake in Minnesota. His name is Caleb Ashling, and he’s Burnsville’s natural resources specialist. He noted, “I knew that [goldfish] could get a little bit bigger than what we see in the pet store, but it is hard to imagine that these tiny little animals can grow to that size.” On top of that, the sheer numbers of them found in the lake was stunning Ashling, too.

“We had some reports from residents of some increasingly large groups of goldfish out on the lake,” Ashling explained in a different interview with CNN in July 2021. “Folks were seeing them from shore, or if they were out kayaking, they would catch a glimpse of them when they were out in their boat.” As a result of that, the community then reached out to Carp Solutions — a local organization that deals with “invasive common carp” — for some help.

An investigation was launched into the strange sightings, but no one could’ve predicted the results. Continuing his chat with KARE 11, Ashling revealed, “So far, between our two rounds of surveys, we’ve caught 28 of these very large goldfish. The largest I believe is about 15 inches in size, and many were kind of close to that range. So they’re pretty significant.” Imagine coming across nearly 30 of these things in a lake!

It’s important to keep in mind that as comical as their large size might seem, these giant goldfish have the potential to cause chaos to a lake’s ecosystem, as well as the surrounding wildlife. After all, the bright-orange creatures are an invasive species: they don’t belong in that habitat. And the long-term consequences of their presence could be dire if the problem isn’t properly addressed: we’re talking aquatic mass destruction here.

Touching on that, Ashling reeled off some of the issues that Keller Lake in particular was facing thanks to the giant goldfish. He told KARE 11, “The biggest problem is that goldfish are bottom-feeders. So, they like to muck around in the bottom, and that uproots a lot of the aquatic plants which help provide a lot of habitat for other fish and animals. In general, they just muck up all the sediments, which releases nutrients into the water. And that can drive a lot of algae blooms.”

So yes, a once-clear lake can quickly turn into a grotty green mess. No one wants to see that, right? Przemek Bajer also added some additional details while discussing this topic with CNN in July 2021. He not only runs Carp Solutions, but he holds a position at the University of Minnesota, too, as a research assistant professor. Bajer said, “Often, [giant goldfish] don’t eat aquatic plants, but the plants simply cannot establish roots in those lakes, they’re just uprooted physically.”

“So if you have a lot of goldfish and carp in the lake, usually the first thing that happens is all the aquatic plants disappear,” Dr. Bajer continued. What do the goldfish actually snack on, then? Do they have a preference? Well, while the little guys sitting in your tank might not look it, these creatures can develop a scary appetite in the wild, turning into eating machines. That certainly explains how they get so big!

Goldfish are known to consume anything from tiny bugs to snails in lakes, but that’s not all. They’ll eat fish eggs and other aquatic offspring as well. Local fish struggle to keep pace with their crazy eating habits, and that can lead to even more problems. This is a common theme with invasive species in the water, hogging food sources to the point where animals in the surrounding area could eventually die out.

Alongside goldfish, there are a number of other invasive species leaving their mark around American waters, too. Animals such as cane toads, lionfish, Nile perch, alewife, bullfrogs, sea lamprey, and flathead catfish have been causing headaches for a long time now. Zebra mussels and Asian carp can’t be forgotten about, either. They’re all playing a part in decimating aquatic ecosystems. But in the case of goldfish, how were they even getting into the likes of Keller Lake to begin with?

The answer’s painfully simple: humans are to blame. People had been letting their pet goldfish go free by dropping them into the Minnesota lake. And according to Dr. Bajer, the issue isn’t just limited to Keller Lake, either. Folks from all over the country have seemingly been doing this across the last few years, not knowing the damage they’re ultimately causing. He went into more detail during an interview with The Washington Post newspaper in July 2021.

Dr. Bajer told the publication, “[The goldfish] seem to be getting more and more widespread. You think about how many of those fish are sold nationally and how many are being released. That’s a pretty big vector of introduction.” To give you a better idea of the spiraling numbers, a different Minnesota county made a jaw-dropping revelation. The officials there believed that they cleared “close to 100,000 goldfish” from local lakes in 2020 alone. 

Now, that doesn’t mean that 100,000 pet owners descended upon the lakes with their fish bowls in hand over the course of a year. Goldfish can reproduce in great numbers, as some females are capable of laying nearly 1,000 eggs in a single period. They also have a surprisingly long lifespan compared to other species of fish, potentially reaching an age of 25. That definitely gives them the time required to grow in stature if they enter a larger habitat in the wild.

But going back to Dr. Bajer’s point about this being a “widespread” problem, here are some other examples to mull over. Away from Minnesota, a guy found a giant goldfish that tipped the scales at close to 4 pounds in a Virginia lake in May 2021. And just a few months before that, a different person said they reeled one in that exceeded 14 inches in Syracuse, New York. In terms of length, that’s the equivalent of a standard toaster!

Mind you, one of the wildest discoveries came in Kentucky in 2019. At that stage, a fisherman pulled in a giant goldfish that weighed a whopping 20 pounds. To help visualize that, imagine tugging on a sledgehammer that’s underwater. Props to the guy for finding the strength to catch it! It couldn’t have been easy. Yet this isn’t just an American problem. As Dr. Bajer explained to CNN, other countries are being forced to deal with the invasive species as well.

“All goldfish are invasive, basically worldwide,” Dr. Bajer stated. “In the whole of North America, Australia, parts of Europe, they are really, really widespread.” Before they became must-have pets across the globe, the original habitats for goldfish were in east Asia and China. So how has this species been able to survive in various different climates after being released into the wild? Well, another expert offered their view on the topic following a lot of in-depth research.

Yes, Dr. James Dickey, of Queen’s University Belfast in Northern Ireland, fronted a project to learn more about goldfish as an invasive species. Specifically, he was looking at their impact on the aquatic ecosystems around the United Kingdom. The report was eventually shared in the NeoBiota science journal in May 2022. Now, while Dr. Dickey’s work touched on plenty of points we’ve already covered, he did also shine a light on the fish’s hardiness in changing environments.

Speaking in May 2022 to The Guardian newspaper, Dr. Dickey said, “Not only are [goldfish] readily available, but they combine insatiable appetites with bold behavior. While northern European climates are often a barrier to non-native species surviving in the wild, goldfish are known to be tolerant to such conditions and could pose a real threat to native biodiversity in rivers and lakes, eating up the resources that other species depend on.” Yep, they’re equipped to deal with differing temperatures.

In fact, goldfish can survive even the harshest of habitats, such as frozen beds of water during the winter. One of the advantages they have over lots of other fish in that respect is that they don’t need a steady supply of oxygen. You see, goldfish are more than capable of holding out for weeks and months on end. Dr. Bajer told The Washington Post, “[That quality] makes them really, really tough and allows them to dominate certain types of ecosystems.”

There’s another issue to consider here, too: when goldfish enter a new habitat, that doesn’t mean they’ll stay there. The animal does have a tendency to spread to new environments if the opportunity presents itself, which makes catching them even harder. As The Minnesota Department of Natural Resources explained, “[Goldfish] work their way through city storm water ponds and into lakes and streams downstream with big impacts, by rapidly reproducing, surviving harsh winters, and feeding in and stirring up the bottom.”

Due to the ecological dangers they pose, it’s actually against the law to drop goldfish in “public waters” around Minnesota. Yet despite that serious deterrent, folks seem to have been getting away with it in recent years. So how do experts plan to clear up areas such as Keller Lake going forward? Well, even back in 2021 Dr. Bajer recognised that any such efforts would need to be a meticulous process, likely to be beset by tricky challenges along the way.

The biggest of those challenges is trying to remove the giant goldfish in a way that won’t negatively affect the local animals. Dr. Bajer had a very delicate balancing act on his hands there. But after using his knowledge of the invasive species, he came up with a potential solution. Of all the food that goldfish like to eat, they’re particularly struck by seeds. So with that in mind, he has been “baiting” specific spots along Keller Lake with bits of cracked corn.

After getting the attention of the goldfish, Dr. Bajer has been gathering all of them inside “specialized nets.” The expert told CNN, “Because goldfish are smart, they can quickly learn where the food is, and also because they are social animals. Once a few of them learn about the food, that information passes through the rest of the population.” In other parts of the country, though, solving the goldfish problem has come at a cost.

For instance, a stretch of water found close to Spokane, Washington, was absolutely teeming with goldfish in 2018. The numbers were so great that the trout originally living there couldn’t sustain their own population, losing out on the resources needed to survive. So, in an attempt to correct the issue, state officials unveiled a plan of action that would set them back by an eye-watering $150,000. That figure alone should give you some idea of how severe the situation had become!

But why has this problem seemingly grown in the last few years? Is there a reason? Well, looking at the U.K.’s goldfish surge, Dr. Dickey believed that there was a potential link to the COVID-19 lockdowns. Quite simply, the suggestion was that some people who’d purchased additional fish while cooped up would let the old ones go “free.” And even though his NeoBiota paper couldn’t confirm that for certain, he’d heard a number of stories that pushed his personal opinion in that direction.

Dr. Dickey told The Guardian, “Whilst our research didn’t focus on whether this problem has got worse since lockdown, there is reason to believe that this is, or at least will be, the case. There have been recent news stories about released Amazonian catfish being found in Glasgow, which may be linked. It may also be that there’s a time lag, and it may only be this summer, when normality kind of resumes and people want to go traveling [and leave their pets behind], that we start to see the effects.”

As for how to keep the issue from getting worse, Dr. Dickey suggested that pet-shop owners could do their part. Yet he didn’t stop there. The expert added, “Goldfish are high-risk. Limiting the availability of potentially impactful [species such as goldfish], alongside better education of pet owners, is a solution to preventing damaging invaders establishing in the future.” The spotlight has been put on those stores back in America as well, but for a slightly different reason.

Instead of being encouraged to limit sales, certain pet shops around the country can actually accept unwanted goldfish. It’s worth asking if you’re looking to part ways! Should that fail to work, though, folks have been urged to seek out other potential takers, whether it’s a pal or member of the family. The nearby nursing homes and schools shouldn’t be dismissed, either. Any of those choices would be better than releasing the fish into an ecosystem that it could have a hand in destroying.

So that brings us back to the giant goldfish at Keller Lake. Despite all the drama that they caused there, Ashling took a crumb of comfort from the attention it ultimately generated. He told KARE 11, “It’s great that people are learning more about some of the dangers or harm that pets can cause if they’re released into the wild. And hopefully [they’re] learning that releasing goldfish, or any type of pet, into the natural environment can cause a lot of unintended consequences.”