Football-size goldfish are taking over US lakes

One of the enormous fish discovered in Lake Keller.

(Image credit: City of Burnsville)

Football-size goldfish are taking over a Minnesota lake after being dumped by their owners.

Officials at Burnsville, a city roughly 15 miles (24 kilometers) south of Minneapolis, issued a warning urging residents to stop releasing their pet fish after recovering multiple foot-long aquatic invaders from the waters of the city's Lake Keller.

And despite their propensity to die while in captivity, the fish are as tough as they come in the wild — capable of living 25 years and surviving for up to five months without any oxygen. (The fish evolved to live in ponds that freeze over in the winter, so their bodies will instead convert carbohydrates into alcohol during this period, which they release through their gills). When these traits are coupled with rapid reproductive rates, goldfish are quickly able to dominate new habitats at the cost of native species.

"A few goldfish might seem to some like a harmless addition to the local water body — but they're not," according to a statement from the Minnesota Department of Natural Resources. "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."

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Ben Turner is a U.K. based writer and editor at Live Science. He covers physics and astronomy, tech and climate change. He graduated from University College London with a degree in particle physics before training as a journalist. When he's not writing, Ben enjoys reading literature, playing the guitar and embarrassing himself with chess.