Goldfish are invasive problem in Twin Cities lake

CHASKA, Minn. (AP) — A small fish commonly found in pet stores and purchased for home aquariums has become an invasive problem in a Twin Cities lake.

The Carver County Water Management Organizations recently removed an estimated 50,000 goldfish from an inlet connected to Big Woods Lake, which is part of the Grace Chain of Lakes in Chaska.

The most like scenario is that someone released goldfish into the lake and the hardy fish began to multiply, according to the organization’s spokeswoman Madeline Seveland.

Big Woods Lake has relatively poor water quality and few other predatory fish species, conditions that have allowed the goldfish to multiply, Minnesota Public Radio News reported.

Last week’s massive haul of goldfish from the inlet is part of a three-year plant to manage and study the species.

“If we’re going to remove the fish, we need to keep track of a percentage of the population that we’re removing, until we can get it down to a certain level where that population may no longer be harmful to the lake ecosystem,” said Andrew Dickhart, the group’s aquatic invasive coordinator.

Since there’s been relatively little research done on goldfish, it’s not yet clear what that threshold is.

Fisheries biologist professor at the University of Minnesota, Peter Sorensen, said goldfish haven’t gotten as much attention as invasive carp, but they are causing significant problems in parts of Europe, Canada and Australia as well as the United States.

“It just hasn’t reached a high level of awareness,” he said. “They don’t jump and knock people out of boats and break bones. But it’s a global issue.”