Research fish biologist, Marybeth Brey (USGS), standing next to the steel soundbar containing 16 underwater speakers (located under the white covers) prior to installation in the lock approach channel in February 2021. Photo by Christa Woodley, ERDC.
Lock 19 at upper Mississippi River mile 364.2 has a new piece of technology—a giant underwater soundbar. In 2021, a 106-foot-long metal structure that contains 16 underwater speakers was deployed on the bottom of the river in the lock approach channel. This soundbar wasn’t installed to play music for the passing barges, instead it was installed to test whether it could deter invasive carp from moving upstream of Pool 20. The process to get this soundbar designed, constructed and installed at Lock 19 is co-led by the U.S. Geological Survey and the U.S. Army Engineer Research and Development Center, and includes close coordination and collaboration with 10 state and federal agencies.
The invasion of four species of invasive carp (bighead, silver, grass and black carp) to U.S. rivers is not new. Since the 1990s, state and federal agencies have been working at decreasing populations of invasive carp and slowing their progression toward the Great Lakes and to new habitats within the Mississippi River Basin.
Bighead carp and silver carp are the two most abundant invasive carp species in the Mississippi River Basin. Invasive carp can be harmful to native fish communities because of a combination of factors. First, they grow to a large size (up to more than 40 inches!) and out of the gape limit of predators very quickly. Because invasive carp grow so quickly, there are few natural predators after about their first year of life. Second, they consume vast quantities of food (phytoplankton and zooplankton), and, finally, they have similar food preferences as early life stages of game fish. This competition for food resources has resulted in declining body condition of native fish (fish are skinnier than they should be) in areas with large numbers of invasive carp. Expansion of invasive carp populations into the Great Lakes and other portions of the Mississippi River, could impact native fish communities and have negative impacts to local economies. Therefore, scientists and managers are exploring multiple ways to control them.
Large numbers of adult invasive carp are removed annually from the rivers through contract and commercial fishing with gill and trammel nets. Over the last decade, several other strategies have been developed that can be combined with fishing to bolster efforts to control invasive carps.
Behavioral deterrents (also called non-structural barriers) are devices intended to control the movement of invasive carp and limit their spread. These devices emit stimuli that fish may avoid, such as annoying sounds, bubbles, electricity, noxious gases (like carbon dioxide) or bright lights. They are deployed with the goal of stopping fish from moving past the deterrent and into areas such as the Great Lakes or the upper Mississippi River and can be used in conjunction with contract or commercial fishing to remove the deterred fish. Yet, all deterrents or barriers are not created equal, and no single deterrent will be effective under all conditions or at all locations. More recently, there has been increased interest in deterrents that are selective for invasive carps that limit impacts to native species, particularly migratory fishes.
Bighead, silver, black and grass carp all have specialized anatomy that makes them different than most native fish species in the Mississippi River Basin. Their specialized hearing makes them particularly sensitive to sound stimuli at certain frequencies (tones measured in hertz) and loudness levels (volume in decibels) compared to most native fish. The visible response of silver carp to sound is most apparent when you drive a motorboat on the river where there are large numbers of carp. Silver carp respond to these sounds by jumping into the air (or into the boat!).
In a laboratory setting, invasive carp also swim away from certain sound signals. So, we wondered, could sound be the Achilles’ heel of invasive carp!? The trick, however, was developing a system that could be deployed at a navigation lock without impacting lock operations or vessel traffic and that used sound signals that deterred invasive carp without impacting the migration of native fish. That is how a large-scale, long-term, multi-agency experimental study to design, construct, deploy and evaluate an underwater acoustic deterrent system (uADS) started at Lock 19 on the Mississippi River near Keokuk, Iowa and Hamilton, Illinois.
Lock 19 was selected as the location for testing the uADS. The dam itself is generally impassable to fish as they would need to jump more than 15 feet out of the water during even the highest water levels just to reach the upper pool. Instead, upstream fish passage is limited only to the lock chamber where a deterrent could be readily deployed. There are also abundant populations of invasive carp and native migratory species around the lock and dam that could be monitored during the study.
In 2019, the U.S. Geological Survey (USGS) and the U.S. Army Engineer Research and Development Center (ERDC) convened a team from (an ad hoc committee of the Fisheries Technical Section of the Upper Mississippi River Conservation Committee) the Upper Mississippi River Invasive Carp Partnership (an ad hoc committee of the Fisheries Technical Section of the Upper Mississippi River Conservation Committee), comprised of agencies representing the five upper Mississippi River states, including the Illinois Department of Natural Resources (DNR), Illinois Natural History Survey, Iowa DNR, Missouri Department of Conservation, Minnesota DNR, and Wisconsin DNR, and three federal agencies (USGS, U.S. Fish and Wildlife Service, and the U.S. Army Corps of Engineers [USACE]) to develop a plan to install and evaluate an underwater acoustic deterrent system for invasive carp at Lock 19. The initial focus was on the three invasive carp species with sizeable numbers around Lock 19 (silver carp, bighead carp and grass carp) and a selection of native species of interest (bigmouth buffalo, blue sucker, lake sturgeon, freshwater drum, flathead catfish, American paddlefish and white bass) to determine if there would be any negative impacts to native fish as a result of the uADS.
The process of developing and testing the uADS would never have happened without the collaboration and support of all the state and federal partners. After the initial study plan development and system design (completed by USGS, ERDC and USACE), the uADS was installed in February 2021 in the lower lock approach channel and recessed into one of the discharge troughs where water is discharged during lock emptying to be out of the way of vessel traffic. Partner agencies continued to assist with the permitting process, monitoring the uADS, tagging and tracking fish, and participating in a briefing event at the start of the project.
We used tagged fish to evaluate the changes in fish behavior as they entered the lock approach channel and encountered the uADS. Tagging fish involves making a small incision in the fish’s belly and inserting a small transmitter. The incision is then sewn up with the same suture material found in the doctor’s office. The transmitter sounds are detected by hydrophones (listening devices) at the lock that can then position the fish akin to the way vehicles and phones are positioned by GPS. Over the course of five years (2021 – 2025) we have tagged and tracked 3,100 fish as part of this project! Some of these fish even provide movement information for other projects as they move into other rivers throughout the Mississippi River Basin.
Even with the help of excellent project partners, this study faced challenges. The Covid-19 pandemic occurred over the first two years of the study and increased project costs, limited the availability of equipment and supplies, and hampered our ability to readily meet in person and communicate. As anyone that spends any time on the river knows, we also have no control over the river conditions or the weather. We experienced historic flooding that nearly flooded the on-site trailer that held all the electronics equipment. We also experienced a drought that caused the water level at the uADS to be extremely low. Animals, such as river otters and beavers, seem to enjoy the taste of electronic equipment and attempted to chew through cables and ropes. Barges and river debris inadvertently damaged equipment, mayfly hatches blacked out communication to our devices, and storms caused power surges. Despite these challenges, we managed to continue operating!
The big question – does it work!? Fortunately, we can conduct this type of study and provide the data and results to natural resource managers to help make decisions on whether the effectiveness is acceptable and worth consideration as a management tool for invasive carp control. The results from our first two years (2021 – 2022) of the study suggest the sound decreased silver carp upstream passage past the uADS, through the lock, and into the upstream pool by about half. Sound had little to no effect on most native fish species, however we observed a 20% decrease in lock passage by bigmouth buffalo. The year-to-year variability in efficacy of the uADS as well as effects on native fishes will have to be considered by fisheries managers to determine whether the benefits of implementing this technology outweigh any costs. More information on the first two years of the study with preliminary results can be found here, and results from 2023 and 2024 will be shared soon.
As we learn more about the efficacy, impacts, and operation of the uADS, we continue to make modifications that may enhance the efficacy of the device and increase the longevity of the equipment. Knowledge gained from this project is actively being used to inform the design and operation of other proposed or designed invasive carp deterrents across the Mississippi River Basin, including the Brandon Road Interbasin Project in Illinois, an invasive carp deterrent at Lock and Dam 5 in Minnesota, and a pilot program for deterrent deployments in the Tennessee, Cumberland and Tombigbee River Basins. Pending funding availability and continued partner support, the uADS will operate as an experimental deterrent through 2026.
Dr. Marybeth Brey is a research fish biologist with the U.S. Geological Survey Upper Midwest Environmental Sciences Center in La Crosse, Wisconsin. She co-leads studies, with Dr. Christa Woodley (U.S. Army Engineer Research and Development Center), to develop and evaluate underwater acoustic deterrent systems for invasive carp control.
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