Invasive “jumping carp,” also known as bighead carp or Asian carp, are moving up the Mississippi River into Minnesota, with 50 of them caught at one time by a commercial fisherman this spring.

But researchers have discovered something that deters them: noise, researcher Nick Phelps said during this season’s fourth and final Water Talk hosted by the Legacy of the Lakes Museum in Alexandria.

Particularly, he said, it’s the sound of outboard motors. So now there are big speakers in the Mississippi River blasting the sound of outboard motors in order to keep the invasive species out of Minnesota.

“When you see the YouTube videos, and these carp are jumping out of the water, it’s that outboard motor noise that is bothering the heck out of them,” said Phelps, director of the Minnesota Aquatic Invasive Species Research Center and an assistant professor at the University of Minnesota. “They’re scared and they jump. It’s just a defense mechanism.”

Rock music, he said, didn’t work as well. And the sound of outboard motors doesn’t seem to bother native species nearly as much.

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Blasting sound at carp is one method researchers have discovered to protect Minnesota lakes, rivers and wetlands from invasive species, of which there are quite a few, including Eurasian watermilfoil, zebra mussels and starry stonewort. The research center was established in 2012 specifically because of their threat.

Invasives are “a big deal” in Minnesota, Phelps said.

“They are fundamentally reengineering our lakes, rivers and wetlands,” he said. “They cost the state millions of dollars in direct management costs at the county and state levels and it’s really changing the way we use our lakes.”

He and Meg Duhr, the center’s research outreach specialist, outline research highlights for some well-known invasive species.

Zebra mussels

Last year, researchers finished sequencing the genome for this sharp-shelled invasive mussel that, while they do remove pollutants from water, can also cut swimmers’ feet and clog up water intake pipes.

By mapping their family tree, researchers know that only one or two separate introductions brought zebra mussels to the Alexandria area, because they’re not genetically linked to other zebra mussel hotspots like Lake Mille Lacs, the Mississippi River or Lake Minnetonka, Phelps said.

While one chemical containing a form of copper looks promising, researchers are still looking at other means of control, including a controversial method involving the alteration of its DNA.

If they identify the gene that forms shells, for instance, researchers could snip it out so that shells won’t form and the mussel would die, Phelps said.

Gene altering could eradicate entire populations of zebra mussels, he said.

“This has huge ethical and regulatory implications,” he added.

Curly-leaf pondweed

In Minnesota for more than 100 years, this plant forms dense mats on the water surface and can also litter the shore when it dies off in mid-summer. Harvesting and herbicides have had mixed results, Duhr said.

Researchers have found that curly-leaf pondweed worsens in the season after a winter with a light snowpack, because more light penetrates the ice and allows it to grow.

They have also discovered that treatments have to take place for at least three years in order to be effective, and should take place in early spring, before the native plants start growing.

“One or two year treatments were almost a complete waste of money,” she said.

Eurasian watermilfoil

This plant is everywhere and costly to manage. It has been in Douglas County since at least the mid-1990s, and is now in six lakes.

One of the worst things about it, Duhr said, is that researchers have discovered it is forming hybrids with the native northern watermilfoil and becoming much more aggressive and difficult to kill.

“It’s a big problem,” she said.

Most at risk are areas that are home to both native and invasive species, as is the Alexandria area. Researchers have been mapping where it grows and are accumulating more data about it.

Common carp

Researchers have learned that unlike other fish species, common carp eat corn, which could prove a possible lure to remove them, Duhr said. There are good reasons to move them, as water quality improves when carp are removed en masse. They are looking at using a pathogen specific to carp to control populations.

How to get involved

The research center can’t look for invasive species in Minnesota’s thousands of lakes, wetlands and streams. So it enlists members of the public to help.

It offers free training in identifying native and invasive plants and animals through its AIS Detectors Program, which formed in 2017.

It also offers Starry Trek, a one-day annual event that brings volunteers and professionals to search for starry stonewort which spreads rapidly and easily and has no known control tools other than removing small infestations by hand, Duhr said.

Since 2017, volunteers found five new infestations, a quarter of all the starry stonewort detections in the state, she said. That helped the state respond quickly.

For those who want to learn more about invasive species, the research center is hosting a three-day virtual event Tuesday-Thursday, Sept. 22-24 called the “Research and Management Showcase.”

Its researchers will speak in much more detail about their efforts. It costs $10 to join. To learn more, visit www.maisrc.umn.edu.