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From old-school nets to unmanned kayaks, biologists and commercial anglers are experimenting with new tools in their arsenal to stem the advance of invasive carp while they await the construction of deterrents at the Brandon Road Lock and Dam in Joliet.
Recently, they removed 750,000 pounds of silver carp from the Illinois River over 10 days in what they believe to be a record for freshwater harvest in the country. It is also the largest single removal effort of its kind led by the Illinois Department of Natural Resources.
This success came after years of trial and error, delayed by issues like lost or broken nets or bad weather.
“It’s one of those things that there’s a lot of pieces that have to fall into place for it to be effective,” said Brian Schoenung, aquatic nuisance species program manager for the department. “But we’ve done a really good job of mitigating those things that can go wrong, and we’ve just gotten better and better. So, yeah, it was a combination of the right conditions, the right people, the right gear and just really good execution of our plan.”
Invasive carp, particularly silver and bighead carp, are a danger to aquatic life due to their large numbers and reproductive capacity. When they reach a new stream, river, lake or anywhere water touches, like wetlands, they can easily outcompete and starve native fish and mussels by eating all the plankton from the base of the food chain.
Given the threat they pose to ecosystems and the fishing industry — as well as tourism — in the Great Lakes region, millions of dollars have been spent and thousands of minds have been put to work at federal, state and local levels to face these unrelenting fish head-on as they continue to advance toward Lake Michigan.
Between Nov. 27 and Dec. 6, biologists from the state and from the Illinois River Biological Station met with contracted fishermen in Starved Rock Pool just southeast of the village of Utica to use an experimental technique that would allow them to remove greater numbers of silver carp than commercial fishing would normally allow.
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For the operation, the group used a 900-foot seine, or fishing dragnet, to surround schools of fish on the sides and from underneath, essentially jockeying and maneuvering them toward the riverbank. Crews have quickly gained experience and improved their effective use of the seine, which allowed them to more than double the amount of fish removed this year.
Schoenung estimated that this year’s haul translates to anywhere between 75,000 and 107,000 silver carp.
The department has used seines at different locations for over 10 years, with some hauls topping over 100,000 pounds of invasive fish, but never collected as much as the recent “exceptional” catch. On many occasions, fish were captured but escaped when the net split open due to weight; crews have since added a sack to the middle of the seine, and it can now hold up to 350,000 pounds if needed.
Schoenung said that using a seine is most effective in cool water. As coldblooded creatures, carp have a metabolism that’s dictated by water temperature; colder water makes the fish less likely to move so they can conserve calories. This, in turn, discourages silver carp — who are “notorious jumpers” — from leaping up and escaping over the net.
The fishermen were able to empty the net while it was still in the water, to return any native fish to the river. Fish processing plants will convert the silver carp into products like fertilizer.
The operation was so effective that anglers are hopeful it can be scaled up in the future, Schoenung said.
Using funds from the U.S. Environmental Protection Agency, the state of Illinois contracts with commercial fishers who each year remove over 1 million pounds from Starved Rock, Marseilles and Dresden Island along the Illinois River — the latest catch alone will bolster this year’s numbers to 1.7 million pounds.
In the past 13 years, these efforts alongside commercial fishermen have led to an almost 95% reduction in the density of the invasive fish in these areas close to the electric barrier in Romeoville, slowing their upstream migration and suppressing their adult populations.
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As the state of Illinois prepares to sign a partnership agreement for a $1.14 billion project — which would kick-start the construction of a series of physical deterrents for invasive carp at Brandon Road — big-scale efforts like the recent seine operation have continued to slow the invasion downstream. If the agreement is signed in the next few weeks, the earliest construction could begin on Brandon Road would be October.
Plans for another large removal operation are underway farther south at the Emiquon Nature Preserve, where scientists will send out four unmanned kayaks into its wetlands over the next two years. As the boats quietly navigate in the dark of night, sonar will gather crucial data on unsuspecting invasive carp so fishermen can target heavily populated areas and remove them.
The Nature Conservancy — a conservation organization that manages the preserve, what they call an “outdoor laboratory of sorts” — is lending its grounds for researchers with the U.S. Geological Survey to study silver, bighead and common carp, which hadn’t breached the preserve until eight years ago.
Despite the human-made earthen levee that separates the wetlands from the river, heavy flooding in 2015 allowed larval carp to get through a patch of dirt that had been loosened during a construction project. Low estimates put the invasive carp population in Emiquon at about 150,000, according to Randy Smith, Illinois River Project Director at the conservancy.
But in learning more about the invasive fish, exactly how many there are, and where in the preserve they hide, the conservancy hopes to eventually be able to remove large quantities of the population from Emiquon to better protect its 3,000 acres of wetlands.
“The ultimate removal technique — we could do it, we don’t want to do it, but we could — is to dry the wetland out entirely, and then remove all of the fish. That’s always an option,” Smith said. The preserve is equipped with a water control structure that would allow this.
He said other wetland managers in the state have gone that route, but he’d want to exhaust all other options before doing that at Emiquon.
“We maybe would try to figure out something else, even beyond the established techniques,” Smith said. “And that is, a little bit, what we’re doing here. This is kind of new and emerging research, and we’re hopeful that it will be effective.”
Fish biologist Josey Ridgway, who has been using sonar technology and potentially groundbreaking methodology to study fish at the U.S. Geological Survey for several years, has been leading a team in experimenting with more affordable and efficient techniques — such as run-of-the-mill kayaks equipped with recreational sonars — in Missouri, Minnesota and, now, Illinois.
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“It’s got a lot of benefits because it’s low-cost, and we can use this technology that a lot of management agencies already have equipped on a lot of their boats,” Ridgway said.
Recreation-grade sonar systems also don’t require advanced technical training, and kayaks cost less than normal survey vessels. “This is kind of cutting-edge technology applications that we’re developing,” he said.
In preparation for the four deployments next year and the other four deployments after that, researchers have gone out to Emiquon twice to preprogram the survey routes into the GPS-enabled kayaks.
The information collected will be analyzed using artificial intelligence, and the conservancy will use data on the invasive fish and their behavioral patterns to plan a large-scale removal operation — that they hope will fill multiple semitrucks — in 2025.
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Ridgway said the researchers will also be simulating removal scenarios by driving fish around with stimuli and obstacles like sound, electricity and nets and in doing so push them to a centralized location in shallow water. Having worked in deep water habitats, Ridgway said he is hopeful the Emiquon wetlands will allow them to more easily influence the fish and move them around.
Smith said the conservancy is open to any and all techniques that the survey data supports, but they’re hoping that whatever large-scale approach they implement will be nontraditional and, even if laborious, will yield faster results that can be replicated elsewhere.
“We don’t want to be a stand-alone, stand-back-and-admire-it type of site,” he said. “We want it to be collaborative, we want it to be a learning laboratory, we want folks to be able to gain some knowledge and whatnot from the work that we do. So working with researchers on a project like this just really plays well into that.”
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While scientists look for a large-scale answer, commercial fishermen continue to contribute using traditional methods of spooking silver and bighead carp out of the water with loud boats and catching them with landing nets as they jump.
Other efforts, while rooted in commercial fishing methods, don’t necessarily have a commercial goal; rather, average citizens concerned with preserving access to waterways and conserving aquatic ecosystems have become determined to catch the carp themselves. For example, on a summer weekend for almost two decades, visitors and residents sail into the Illinois River from the village of Bath to see which boat or team can capture the most silver carp.
While these startle tactics can remove thousands of pounds of fish in a day — Smith said it can be anywhere from 5,000 up to 8,000 pounds — this amount would be minuscule to the fish population at Emiquon. And, he said, only 1% to 2% of invasive silver and bighead carp have been removed from the preserve using these commercial tactics.