Grass carp graze on aquatic plants. In fact, fish biologist James Wamboldt of the U.S. Geological Survey said they were intentionally introduced to waterways throughout the nation to control plant growth underwater.
“What we’ve found over the decades of doing this, they really disrupt the food web by removing all of that vegetation which is really important for larval fish and young fish for cover and habitat as well as food,” Wamboldt said.
“They’ve caused quite a bit of havoc now that they’re spreading.”
The loss of plants has also caused water quality to decrease, which could intensify algae blooms that can be harmful to humans and wildlife.
Wamboldt said it’s also an issue for commercial fishers, who are interested in bighead and silver carp rather than grass carp.
“If you look at their catch data the last ten years or so, you can see that there’s a substantial increase in grass carp captures that are somewhat incidental because it’s not their main target,” Wamboldt said.
The USGS will spend the next couple of months installing bait stations on pool 19, which is a 46-mile stretch of the Mississippi River from Keokuk to Burlington.
The goal is to catch around 100 grass carp and implant acoustic transmitters. The fish will then be released back to the river so researchers can monitor their behavior.
Wamboldt said scientists have done similar work in Michigan and Ohio. They’re now focused on the Mississippi because it has a more substantial population of grass carp.
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