Effort Underway To Manage Invasive Goldfish In Chaska Lakes

MINNEAPOLIS (WCCO) - Some Chaska lakes are dealing with an invasive species typically found in household aquariums.

In 2019, goldfish were first detected in Big Woods Lake and Lake Hazeltine.

Scientists say they disrupt the entire ecosystem.

And the concern in Chaska is that they could make their way to the Minnesota River.

On Big Woods Lake, it's a different kind of fishing opener.

"It's mostly just goldfish," said Jordan Wein of WSB and Associates.

The theory is that a couple years ago a pet owner released a goldfish or two into the lake not knowing it would lead to a population explosion. So now, Wein and his crew are using a method called "electroshocking" to learn more.

"That power sends some electricity into the water and it stuns the fish momentarily. Enough time for two netters to hang off the front of the boat, take some dip nets and scoop up whatever we are looking for," said Wein.

It's a catch and release effort but the fish will be tagged before they're released. Scientists want to know where they spawn and where they're going.

It's all part of a three-year plan. This is year one of the plan, with a goal of not necessarily eliminating the goldfish, but managing them.

"Last fall we removed close to 100,000 goldfish," said Tim Sundby of Carver County Water Management.

For the fish, it's strength in numbers. Sundby simply wants to find a way to bring their numbers down enough so vegetation along with fish like bluegills and sunfish, can return.

"If you are familiar with rough fish they really upset the whole ecosystem," said Sundby. "They stir up sediment and they can dig three feet down. Then it's basically a concrete bottom. Nothing is living. Nothing is producing oxygen."

Without a management plan they're worried the fish could eventually find themselves in the Minnesota River- which means time is of the essence.

"We'll have some year-to-year comparable data to see if we are making a difference," said Wein.

Carver County Water Management is hoping what they learn from this project can be applied to other Minnesota lakes dealing with goldfish infestations.