A local group that hopes to see Lake Winona’s water quality improve is planning to conduct a study on the carp population in the lake. The Winona City Council approved a grant application last Monday that would fund an effort to catch and tag carp in the lake in order to determine how to handle the carp population in the future. A previous study found the fish were exacerbating water quality issues by stirring up phosphorus in lake sediment.

The Healthy Lake Winona group is applying for a pilot program called the Clean Water Legacy Partners Grant from the Minnesota Board of Water and Soil Resources to get an understanding of where the carp in Lake Winona are spawning. The grant would fund a study, which in the future could be used to apply for grants that would aid the city in the removal of the invasive species from the lake.

The common carp is an invasive species introduced to Lake Winona likely sometime in the late 1800s, according to Natural Resources Sustainability Coordinator John Howard. The species were probably purposely put into the lake for sport and eating, he added. 

Howard and Healthy Lake Winona member and Winona State University (WSU) Biology Professor Neal Mundahl said the city tried to solve the lake carp problem in the 1970s and 80s by poisoning all the fish species in the lake, but carp eventually found ways back into the lake. Howard added that this wouldn’t likely be the case in the future, as the new Mankato Avenue roundabouts construction included the installation of new fish barriers between Lake Winona and Gilmore Creek.

Currently, there are concerns about the fish worsening water quality in the lake. Carp are bottom feeders, digging around the bottom of waterways for food, and scrounging up lake-bottom sediment. The city of Winona is trying to clean up pollutants, such as excess phosphorus, in Lake Winona as part of its new watershed plan. Naturally, phosphorus settles at the bottom of the lake, but the carp’s eating habits stir it up, increasing phosphorus levels in the water, Howard said. Too much phosphorus causes algae blooms, depleting oxygen for other fish and making the lake a not-so-pleasant body of water to swim in.

Applying for the grant is the first step of the city’s process to begin cleaning up the phosphorus from the lake. The $50,000 study from a company called Carp Solutions would see that carp are caught, tagged, and released back into the lake in order to track the fish’s population and spawning environment. Currently, the city does not know where the fish go during mating season, so the study would help determine that.

Once researchers are able to follow where the fish are going, they can find ways to mitigate their spawn rates and prevent them from returning to the lake with electric fences, according to Mundahl.

Mundahl said that the carp have popped up as a nuisance on Healthy Lake Winona’s radar in recent years, as data from WSU students’ research and the University of Minnesota information showed the population was doing too well. “It ended [up] being considerably higher than what’s recommended for Minnesota lakes,” Mundahl said.

If the Healthy Lake Winona group is awarded the grant, the city can then conduct the study during the summer and later apply for different grants that would help cover the costs to remove or at least manage the carp from the lake. One option would be to bring in commercial fishing boats to net up the carp, Howard said.

“I hope we’re able to figure out how many carp there are in there,” Mundahl said. “Either way, if it's too many, we can hopefully facilitate some kind of plan to start managing better. If it’s too few, we’d still need to keep an eye on it in the future, and make sure it doesn’t get bad.”