Oversize Goldfish Are Taking Over One Minnesota Lake, Causing Issues For Local Fish

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Large goldfish, released by pet owners into bodies of water, are contributing to poor water quality in some lakes and ponds in Minnesota. / City of Burnsville, Minn.

Pesky, oversize goldfish are causing problems in Minnesota.

Authorities in Burnsville, Minn., have urged residents and owners of pet goldfish not to dispose of the family pet in lakes and ponds. The city tweeted a warning that doing so has resulted in the takeover of one local lake by overgrown goldfish.

"They grow bigger than you think and contribute to poor water quality by mucking up the bottom sediments and uprooting plants," authorities wrote on Twitter. "Groups of these large goldfish were recently found in Keller Lake."

This isn't the first time Minnesota lakes have become overrun with oversize goldfish.

Last November, wildlife officials found thousands of goldfish swimming in Big Woods Lake in Chaska, a suburb of Minneapolis. A team had to remove a truckload of 500,000 of the goldfish due to environmental issues caused by the fish.

The problem has also cropped up in Boulder, Colo., and Lake Tahoe, Nev., where researchers found thousands of goldfish in local lakes in both areas years ago.

The act of dumping unwanted goldfish into local ponds is actually illegal in most states, including in Minnesota, where the problem has recently cropped up.

It's considered "illegal fish stocking," and it has turned up in every corner of Minnesota, as laid out in a piece in Minnesota Conservation Volunteer, a magazine from the state's Department of Natural Resources. Such fish stocking upsets the balance of existing natural fish communities and spreads disease, the piece points out.

Goldfish are considered invasive species that uproot underwater plants and compete with native fish for food and shelter. Speedy reproducers, the fish live up to 25 years and are a real pain to remove, according to Carver County, Minn., officials.

If you're a pet owner and have realized a decades-long commitment with your goldfish is not what you had in mind, the U.S. Fish and Wildlife Service recommends putting Goldie up for adoption. Another alternative is to contact a local veterinarian or pet retailer to find ways to humanely dispose of the fish without causing harm to native fish species in your local neighborhood.

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