A city in Minnesota wants residents to give their pet goldfish to a "responsible friend" instead of throwing it in a waterway.
The city of Burnsville tweeted that it recently found large groups of goldfish at Keller Lake, and suspects residents could be the cause.
"Please don't release your pet goldfish into ponds and lakes! They grow bigger than you think and contribute to poor water quality by mucking up the bottom sediments and uprooting plants," the city said in a tweet.
The city has partnered with the city of Apple Valley and Carp Solutions to conduct a fish survey on Keller Lake to assess populations of invasive goldfish and other fish in the lake.
"Instead of releasing your pet goldfish in a local lake or pond, please consider other options for finding them a new home like asking a responsible friend or neighbor to care for it." the city of Burnsville said in a Facebook post.
Daryl Jacobson, natural resources manager for the city of Burnsville, told USA TODAY the city had received reports about goldfish being in Keller Lake before conducting an initial fish survey.
"We expected to get goldfish, but were surprised how big they were," he said.
Goldfish tend to match their environments and that's why they can be small in a home aquarium and larger in natural waterways, according to Jacobson.
"They are a tough species. They can survive under ice, with low oxygen and in unclear water," he said.
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In the past, other cities have brought up concerns about the "giant" fish and its effects on ecosystems.
In 2013, biologists were worried that Lake Tahoe's blue water may be affected by the large goldfish population, after they believed people were disposing of the pets in the lake.
Goldfish reintroduced to the environment are considered an invasive species, an organism that is not indigenous, or native, to a particular area that can cause great economic and environmental harm.
Last year, a man fishing in South Carolina caught what appeared to be a 9-pound goldfish, though the fish wasn't native to the area.
"It reminded me of when I was a little kid, my mom was a teacher and she brought a goldfish that was in a small fishbowl home," Ty Houck, Director of Greenways, Natural and Historic Resources for Greenville County's Department of Parks, Recreation and Tourism, told USA TODAY. "We put it in a bigger aquarium and we both were surprised (at) how big it grew."
In Burnsville, Jacobson said he believes there are probably more goldfish in the lake but due to preliminary findings, isn't sure if they are or will become a big problem.
For residents who decide they don't want them, he urges for them to find an alternative than throwing them in a waterway.
"You may think it's a humane thing to do, but these fish are not meant to be in our natural system in large numbers," Jacobson said.
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This article originally appeared on USA TODAY: Giant pet goldfish in Minnesota lake?Invasive species causing harm