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The carp effect: Data show there’s way too many carp in Long Lake

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LONG LAKE — Members of the Long Lake Waters Association thought there were a lot of common carp in Long Lake, but now they have scientific evidence proving there are more of the invasive fish than there should be. And it’s affecting water quality in the lake.

That’s according to preliminary data from the firm WSB, which contracted with the Long Lake Waters Association to tag and count common carp in Long Lake as part of the association’s effort to improve water quality in the entire Long Lake Creek Watershed.

Preliminary data from phase one of the nonprofit’s carp remediation project show there are 11,000 to 24,000 common carp in Long Lake, with WSB determining 21,000 individual carp would need to be removed to restore ecological balance in the lake.

Common carp degrade the water quality in lakes by rooting the lake bottom when searching for food. This stirs up sediment and devastates habitats for animals and plants and releases nutrients that are buried in the lake bottom, which contributes to excessive algal blooms.

“We definitely learned the carp population is three to four times larger than is recommended for good water quality, which guides our thoughts to carp management not only in Long Lake but in the entire Long Lake Creek Watershed,” Jane Davidson, treasurer of the Long Lake Waters Association, told Lakeshore Weekly News.

Davidson said they’ll use this data and additional data the nonprofit will collect through its partnership with the Minnehaha Creek Watershed District and the cities of Orono, Medina and Long Lake to determine the best ways to manage carp and improve water quality throughout both watersheds.

Managing carp

One way to manage carp is to actually remove the fish from the lake — a process called harvesting. Cassy Ordway, board chair and president of the Long Lake Waters Association said there’s a large market for carp, so the harvested fish don’t necessarily go to waste — they can be used for food, fertilizer or animal feed.

The association is hoping to do a harvest of carp this winter. WSB tagged 10 carp with high frequency radio tags so they’ll be able to track the fish and identify where they’re gathered together so they can be removed from the lake through commercial seine netting operations, WSB’s preliminary report said.

Long Lake Waters Association does need to raise $10,000 to fund the harvest, and it’s hoping to do so through Give to the Max Day on Nov. 15 (find out more information and donate at https://www.longlakewaters.org/).

“I think it’s really important that in this partnership we see the value of the data, but we also see the value of action. And we really want to make sure we’re moving forward with some implementation as well as just data collection,” Ordway said.

Another way to manage the carp population is to control the number of new carp that are introduced in the watershed by minimizing recruitment.

“There are kind of two aspects to that. One is that you learn where they lay eggs and then you can introduce native fish that like to eat the eggs,” Davidson said. “And then the other one is that you actually block the entry to the body of water with fish barriers. The water still goes through, but the fish can’t go through and therefore they don’t — their habitat has changed,” Davidson said.

Future research

Recruitment and other efforts to control carp populations will be part of the nonprofit’s future plans after it collects more data about carp migration patterns and water quality levels. The partners are hoping to get a $112,000 grant to fund research that will help them develop a strategic, long-term plan.

“That study would be very important in informing us what the most beneficial things to do would be. While we might say barriers is one choice, we still need to make a plan to determine where we should put them, where the money should go, and what’s the most effective means of improving water quality in our watershed,” Davidson said.

Down the road, the Long Lake Waters Association is confident they’ll be able to make a substantial difference in improving water quality with the help of all its partners.

“When we’re looking at a long-range plan, we are very cognizant that this is a long commitment. It’s something that we won’t ever say ‘we’ve reached our goal, we’re done,’” Ordway said. “It’s a commitment to the watershed and we will do everything we can, but it’s a long-term commitment. There’s no silver bullet that if we do the one thing, it’s going to be perfect. It’s an ecological balance.”

And that’s why Ordway says the partnership between the watershed and the cities in the watershed is so important. She says their efforts “can be much more effective and create greater change if we all work together” because all the lakes are connected, so if one city is doing a lot to mitigate storm water runoff but another city isn’t, they won’t be as successful in improving water quality throughout the watershed.

“Currently, we’re addressing issues that have built up over time as well as new sources of pollution from current rainstorms and so to be an environmentalist requires that you do this all the time. There’s no stopping,” Davidson said.

Ordway said the efforts of the partners and the watersheds will also help the cities meet water quality benchmarks that are set by the Minnesota Pollution Control Agency.


water quality

The Long Lake Creek Watershed encompasses 7,619 acres and includes seven large lakes — School, Holy Name, Mooney, Wolsfeld, Dickey’s, Long Lake and Tanager, as well as streams and creeks in the cities of Orono, Medina and Long Lake. Water from the watershed also flows into Lake Minnetonka through Tanager Lake and the Minnehaha Creek Watershed District.

The Long Lake Waters Association says five of the seven lakes in the watershed are identified by the Minnesota Pollution Control Agency as “impaired for excess nutrients.” Meanwhile, Long Lake was given a “D” water quality rating by the agency with the note that it “partially supports swimming” due to high phosphorus and pollution levels. The association adds that blue green algae and E. coli have prompted Long Lake beach closures during the summer months.

Melissa Turtinen is the community editor for Lakeshore Weekly News and Eden Prairie News. She's passionate about adding context to stories and informing people about what's going on in their community. She enjoys being outside, traveling and good beer.


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