Mote Marine Laboratory scientists have published new research demonstrating that an electronic pulse device (EPD) can effectively deter and delay sharks from taking fish off fishing lines — a breakthrough that could help reduce shark depredation, the loss of catch or gear to marine animal encounters.
Focusing not only on human-centered benefits but also nature-centered benefits is the best way to support a "win-win" healthy economy and ecosystem. Protecting these essential apex predators, such as sharks, helps maintain a balanced multi-species population and biodiversity, as well as conservation and sustainable use of our ocean resources.
This study builds on Mote's legacy of pioneering shark repellent research, representing just one facet of Mote's nearly 70 years of diverse marine research and science-based conservation work. Today, Mote continues to serve as the only congressionally designated National Center for Shark Research.
In the newly published study, "Electronic pulse device deters and delays shark feeding in a depredation context" (Journal of Fish Biology, 2025), Mote researchers found that bonnethead sharks (Sphyrna tiburo) were more than 45 times less likely to consume bait when exposed to an active EPD compared to an inactive one.
The device, called 'Shark Guard' and manufactured by FiskTek Marine, emits brief electrical pulses that harmlessly overstimulate sharks' electroreceptors, delaying or deterring feeding behavior and showing strong potential to mitigate shark depredation. Shark Guard is fastened with the bait on appropriate fishing gear to simulate controlled, accurate fishing conditions. Even when sharks did feed, they took significantly longer to approach and consume the bait, often displaying what scientists referred to as a "rapid withdrawal," a quick, startled turn away from the food source when they sensed the electric pulse.
"We're seeing that a short, controlled burst of electricity can make a big difference in shark behavior, giving fishers precious seconds to reel in their catch and helping reduce conflict with these protected species," said Jack Morris, lead author and Senior Biologist in Mote's Sharks and Rays Conservation Research Program.
The research team conducted 198 controlled trials at Mote's Marine Experimental Research Facility (MERF) in Sarasota, Florida, that is managed by Morris, using captive bonnethead sharks. Each shark pair was presented with bait attached near either an active or inactive device, while high-definition cameras above and below the water recorded every interaction.
The findings suggest that EPDs like this could become valuable tools for resource managers seeking non-lethal solutions to reduce shark depredation, an issue that affects livelihoods of recreational fishing guides and commercial fishers alike, and may influence public support for shark conservation in many coastal regions.
Depredation can be harmful to both sharks and the fishers catch. When a hooked fish is unable to evade a shark, the shark may take the catch. Many recreational fishers and fishing guides who would otherwise release their fish alive never get the opportunity in these circumstances. Commercial fishers are left without their harvest as a result of shark depredation, which then requires additional time and financial cost to catch enough fish to meet their daily limit.
"Sharks are now beginning to recover in the U.S. Atlantic after overfishing in the 1980s and 90s, and people using the ocean are starting to notice that," said Dr. Demian Chapman, Director of Mote's Sharks and Rays Conservation Research Program. "Mitigating depredation will obviously benefit people who are fishing, but it will also benefit sharks because it will ensure that the strong public support that we see for shark conservation doesn't erode over time."
This study marks an important first step in exploring how electronic pulse devices can help reduce shark depredation. The results show strong potential for these tools to lessen unwanted shark interactions, leading to a safer and healthier environment for sharks, fish, and fishers. Mote researchers plan to continue testing these devices in both controlled and real-world settings.
"The research conducted by Mote's expert scientists is essential to advancing the protection of marine ecosystems and diverse economies that depend on long-term sustainability of healthy oceans," said Mote's President & CEO, Dr. Michael P. Crosby. "We look forward to expanding innovative research like this, in partnership with both fishing guides and commercial fishers to better understand and mitigate human–wildlife conflict using practical, science-driven approaches."
Dr. Perry W. Gilbert, Mote's former Lab Director, tested a shark repellent for the Navy called Shark Chaser. His countless studies helped expand scientific knowledge of sharks and propelled shark repellent research. Dr. Eugenie Clark, widely known as "The Shark Lady" and Mote's founder, was among the first scientists to investigate natural shark repellents. Her groundbreaking studies in the 1970s and 1980s revealed that the Red Sea Moses sole (Pardachirus marmoratus) produces a chemical substance capable of repelling sharks. These discoveries paved the way for generations of research exploring chemical and sensory-based deterrents.
"Dr. Gilbert and Dr. Clark showed the world that sharks could be studied, understood, and even deterred safely," said Morris. "Our research continues that same spirit, using science and technology to reduce conflict and ensure the conservation of these remarkable animals."
The study was supported by the Roe Foundation, the Perry W. Gilbert Chair in Shark Conservation, and the National Marine Fisheries Service Southeast Region (Grant NA25NMFX469G0022-T1-01).
The full study, titled Electronic pulse device deters and delays shark feeding in a depredation context, is available in Journal of Fish Biology, 2025. https://onlinelibrary.wiley.com/doi/10.1111/jfb.70220