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Burnsville, MN. = Once-tiny goldfish are causing ginormous problems in Minnesota, a state that prizes itself for fishing opportunities and clean waters.
Goldfish are tossed carelessly in lakes, such as Keller Lake in Burnsville, Minnesota, by people who no longer want to care for their aquarium fish and think it's more humane than other means of disposing of unwanted fish.
It's fine for the goldfish. But not so much for the other fish in lakes and rivers.
They grow and grow and grow until they're the size of a football or larger, gaining a big, bad reputation as they do — to the point that they're on par with their bottom-feeding cousins, the much-maligned carp, which are notorious for disrupting freshwater ecosystems.
The goldfish found in Keller Lake in the Minneapolis suburb are causing a whale of a problem for city officials.
"Please don't release your pet goldfish into ponds and lakes!" the city said in a tweet. "They grow bigger than you think and contribute to poor water quality by mucking up the bottom sediments and uprooting plants."
Just ask Jessie Koehle, a water resources specialist for the city of Eagan, about 7 miles from Burnsville. The goldfish population spun out of control in a pond at city park, and getting rid of them was an expensive, time-consuming job.
"We tried netting them out," Koehle told the Minnesota Department of Natural Resources, "and we got thousands of them, but we couldn't get them all."
Eagan officials eventually resorted to chemical treatments to kill off all the fish in the pond and started over. The pond water is again clear, and the native plants are thriving, according to the DNR, but the time and expense to the city could have been avoided if people hadn't dumped their fish into the pond.
Minnesota conservation officials say other ornamental and pet fish found in the state's waters include koi, pacu and piranha.
"A few goldfish might seem like a harmless addition to the local water body — but they're not," the DNR said in a story for Minnesota Conservation Volunteer magazine. "Goldfish are in the minnow family and can work their way through city stormwater ponds and into lakes and streams downstream with big impacts, by rapidly reproducing, surviving harsh winters, and feeding in and stirring up the bottom like their close relatives, the common carp."
The supersized goldfish problem has been growing in recent years, according to Przemek Bajor, an aquatic invasive species professor at the University of Minnesota and the owner of a business known as Carp Solutions.
"They seem to be getting more and more widespread," Bajor told The Washington Post. "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."
The problem is global, with out-of-control goldfish populations reported from the East to West Coasts, in Canada and Europe. In Lake Tahoe, Nevada, invasive species have accounted for about half of the fish in the Lake Tahoe Basin. In 2018, the Washington Department of Fish and Wildlife estimated it would spend $150,000 to eradicate feral goldfish from a lake at a corporate medical park.
Supersized goldfish don't just do their damage wherever they are dumped. Goldfish have a yen for travel and can migrate quickly across bodies of water. For example, a few were released into an Australian river early in the 21st century and migrated to the Vasse River, where they've created a ginormous, long-lasting problem, according to one study that found fish traveled 3.35 miles in just 24 hours.
Goldfish came to the United States by way of China, where they were selectively bred for food 2,000 years ago. They eventually went from the table to ornamental gardens, where they were regarded as symbols of luck and fortune, and came to the United States around the mid-19th century.
Goldfish look fairly banal when swimming around in their small tanks, but they're actually quite smart and hold onto memories for about three months. Goldfish can discriminate between music by Bach and Stravinsky and can push tiny soccer balls into a net.
"We think of goldfish as not being very intelligent — more like furniture or home accessories than sentient creatures," Dean Pomerleau, an engineer from Pittsburgh told The New York Times.
Giant goldfish causing havoc in lakes after being released by pet owners
