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Health, Science and Environment

Stop releasing your pet goldfish into public waters

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MDNR-Fisheries Division
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A DNR staff member holds up a giant goldfish within the Lake Erie Basin.

Whether it’s flushing them down the toilet or sending them down the river, releasing live goldfish into public water does more harm than good.

In response to an outbreak of football-sized goldfish in some Minnesota lakes this summer, the Michigan Department of Natural Resources is warning people about the dangers of introducing live goldfish to non-native waters.

Michigan is not experiencing the same severity as Minnesota. But some large goldfish have already populated the Lake Erie Basin, said Seth Herbst, a DNR aquatic invasive species coordinator.

“Anytime you have a new species that is not native to an environment that gets introduced, it could cause a series of different threats,” Herbst said. “They could cause detrimental harm to the existing aquatic life and that water body.”

When released into the wild, Herbst explained, goldfish can grow to sizes much bigger than they do in domestic tanks. They may destroy habitats native fish use for reproduction, shelter and feeding.

This is what happened in Minnesota.

“Please don’t release your pet goldfish into ponds and lakes!” the city of Burnsville, MN said in a July 9 tweet. “They grow bigger than you think and contribute to poor water quality by mucking up the bottom sediments and uprooting plants.”

Additionally, goldfish increase the turbidity of the water and deplete aquatic insects that native fish and other organisms use for a primary food source.

“If that species is introduced, it becomes established and then it proliferates, like many invasive species have the ability to, it could really disrupt the aquatic ecosystem,” Herbst said.

It’s important to note there are differences between non-native species and invasive species said Sarah Lesage the aquatic invasive species program coordinator for the Department of Environment, Great Lakes, and Energy (EGLE).

Tropical fish that can be found in aquariums and pet shops are not native to the region, nor could they survive a harsh Michigan winter. The issue with goldfish and other invasive species - is that they can make a home here.

Lesage said it doesn’t stop at goldfish. Carp, koi and many non-native aquatic plants have the potential to disrupt native ecosystems.

Both Herbst and Lesage recommend donating live goldfish to a local pet shop to be resold if you can no longer take care of it.

The Reduce Invasive Pet and Plant Escapes (RIPPLE) program is a collaborative effort between EGLE, the DNR, the Department of Agriculture and Rural Development and Michigan State University Extension. Its main purpose is to advise aquarium and water gardener professionals, retailers, and hobbyists about what to do with unwanted plants and animals.

More information on how to properly part with goldfish can be found on the RIPPLE website.