Project background
Invasive bigheaded and silver carp continue to threaten Minnesota waters as they attempt to move north through the Mississippi River. While dams can block fish movement, navigation locks remain a pathway that allows invasive carp to swim upstream. Building on earlier research that successfully prevented carp from passing through a model lock and dam, this next phase focuses on refining deterrent strategies that can be used in real-world navigation systems.
MAISRC researchers are working with a custom-built scale model lock and dam designed and constructed by the Applied Research and Engineering team at the St. Anthony Falls Laboratory (SAFL). With design input from researchers, SAFL created a tank that included features like lock and miter gates, a spillway, and systems to manage water flow.
All experiments will be conducted at the MAISRC containment lab, where researchers can safely test fish behavior under controlled conditions before applying the findings in the field. The results will help inform the design and operation of proposed invasive carp deterrent systems at locations such as Lock and Dam 5 on the Mississippi River and other high-priority navigation structures throughout the region.
This research can provide state and federal resource managers with practical, science-based tools to help prevent the spread of invasive carp while maintaining river navigation and protecting native fish communities. By improving selective deterrent technologies, this project moves Minnesota closer to effective, long-term strategies for keeping invasive carp out of vulnerable waters.
Phase I
Project title: Increasing effectiveness of bigheaded carp deterrents by carbon dioxide integration
Project manager: Allen Mensinger, Swenson College of Science and Engineering at University of Minnesota Duluth
Funded by: MAISRC and the Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources
Project timeline: 2021-2023
Research findings:
Researchers found that adding carbon dioxide (CO₂) to existing fish deterrent systems can improve their ability to prevent invasive bigheaded carp from moving upstream. In laboratory experiments, bubble curtains infused with CO₂ were more effective at blocking common carp than bubble curtains using air alone, while having only limited effects on a native fish species. This suggests that CO₂-enhanced barriers could help target invasive carp while minimizing impacts on non-target fish.
The team also tested a combined sound-and-bubble barrier, known as a Bio-Acoustic Fish Fence (BAFF). Adding CO₂ increased the barrier's effectiveness, raising blockage rates for both common carp and bighead carp. Although the improvement was modest, researchers concluded that even a small increase in effectiveness could make a meaningful difference in slowing the spread of invasive carp at critical locations such as locks and dams.
Researchers also demonstrated that bigheaded carp can learn to associate sound with rising CO₂ levels. After conditioning, the fish moved away from the sound source more quickly and stayed away longer than unconditioned fish. While this learned response weakened over time, the findings show that pairing sound with CO₂ has the potential to strengthen acoustic deterrents and could improve future barrier technologies.
The research shows that integrating CO₂ into existing deterrent systems is a promising strategy for reducing the spread of invasive carp. Future studies will evaluate these technologies in larger experimental systems and real-world lock and dam settings to determine how they perform under field conditions.
Phase II
Project title: Evaluating CO2/sound bigheaded carp deterrents in model lock/dam
Project manager: Allen Mensinger, Swenson College of Science and Engineering at University of Minnesota Duluth
Funded by: MAISRC and the Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources
Project timeline: 2023-2024
Research findings:
Researchers tested eight schools of bigheaded carp in a model lock and dam and successfully conditioned them to associate sound with carbon dioxide release. The deterrent system achieved a 100% success rate in preventing upstream carp passage through the lock during more than 200 trials. Before conditioning, the fish freely swam through the lock chamber and generally preferred the upstream pool. After conditioning, carp rarely approached the lock entrance and almost never entered the lock chamber. This is the first carp deterrent system to achieve a 100% success rate under these experimental conditions.
Phase III
Project title: Evaluating CO2/sound bigheaded carp deterrents in model lock/dam
Project manager: Allen Mensinger, Swenson College of Science and Engineering at University of Minnesota Duluth
Research team: Jack Vannurden, Graduate scholar, MAISRC
Funded by: MAISRC and the Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources
Project timeline: 2024-2026
Research findings:
Bigheaded carp can get around dams by swimming through lock chambers, creating a challenge for preventing their spread into Minnesota waters. Researchers tested whether combining an acoustic deterrent with carbon dioxide (CO₂) could be more effective than sound alone. Fish were trained to associate sound with CO₂, and the combined approach completely prevented upstream passage of the trained fish. Even more promising, the trained fish helped deter untrained fish from moving upstream, suggesting that the approach could work even when not every fish can be conditioned.
Researchers also studied how quickly CO₂ dissipates from flowing water. They found that CO₂ can remain elevated for hundreds of meters or more in a river when there is little dilution, although the rate at which it returns to normal depends on factors such as turbulence and wind. This information will help researchers determine how CO₂ could be used effectively while minimizing potential impacts on native fish.
Overall, the findings suggest that intermittent CO₂ combined with acoustic deterrents could provide a promising new tool for preventing bigheaded carp from moving upstream through locks and dams, while also helping managers understand how to safely deploy the approach in natural waterways.