New Solution for Shark–Fisher Conflict

Shark versus human has been an almost entirely fictitious theme across movies, the media, and even our own minds while swimming in an open ocean; however, there is a very real ongoing battle between sharks and fishermen. Oftentimes, when fishers hook their line, a shark takes the catch before the fish can be landed, a phenomenon known as depredation. All those stolen fish add up and contribute to economic loss for both recreational and commercial fisheries.

Improvements in fishing technology, increased fishing pressure, and reduced fish populations have all intensified encounters between sharks and fishing gear. Dr. Demian Chapman, director of Mote’s Sharks and Rays Conservation Research Program, warned that without solutions to shark depredation, growing frustration among fishers could undermine public support for shark protection.

Jack Morris, senior biologist in Mote’s Sharks and Rays Conservation Research Program added, “We don’t have a shark overpopulation problem, we have a shark–human competition problem.”

New research from Mote Marine Laboratory suggests a promising, non-lethal solution that could benefit both fishers and sharks. In a study published in the Journal of Fish Biology, Mote scientists found that an electronic pulse device (EPD) can significantly deter and delay shark depredation, a potential “win-win” tool that reduces financial losses for fishers while supporting long-term shark conservation.

The device tested in the study, called Shark Guard, emits brief electrical pulses that harmlessly overstimulate sharks’ electroreceptors- specialized sensory organs that allow sharks to detect electrical fields in the water and are often used for hunting fish. The sensation startles the shark, causing it to turn away before taking the bait.

Morris emphasized that the pulses do not injure sharks, “It’s equivalent to dragging your feet across a carpet and touching someone- just a quick, harmless jolt,” he said. “We’ve seen sharks come back and investigate again, which tells us it’s not hurting them.”

Researchers conducted 198 controlled trials at Mote’s Marine Experimental Research Facility in Sarasota using captive bonnethead sharks (Sphyrna tiburo), and the results were striking. Sharks were more than 45 times less likely to consume bait when the EPD was active compared to when it was inactive. Even when sharks did take the bait, they took significantly longer to do so, often displaying what scientists called a “rapid withdrawal”- a sudden, startled turn away from the food source.

“What we’re seeing is that a short, controlled burst of electricity can make a big difference in shark behavior,” Morris said. “It gives fishers precious seconds to reel in their catch and helps reduce conflict with these protected species.”

So far, researchers have not identified major drawbacks. Overall, Morris has been very pleased with how the device works, although he would like to see future versions with slightly stronger performance.

Shark Guard was originally developed for large-scale operations overseas. “The initial design implementation of this device was intended for commercial longline fisheries out in the UK, primarily in the tuna fishery,” Morris said. Studies conducted there have reported promising results, including “about 70% retention of their catch and reduced bycatch of shark species.” However, Morris stressed that Mote has not yet tested the device in those contexts domestically.

Looking ahead, Mote researchers plan to broaden both the scope and scale of their work. “There are other individuals using a variety of devices and trying to see how effective they are,” Morris said. “But our plans going forward are to scale up our operations and start incorporating more species- particularly those more prone to depredation, like sandbar sharks, bull sharks, and even the great hammerhead.”

Testing is already underway in both controlled and real-world settings. “We started some field trials last December and got some really positive results,” Morris said. “We’re ramping up more as we move forward.”

At present, the device is not widely available. Manufacturers are continuing to refine the design, particularly the housing, to make it more practical for everyday use. While discussions are underway about whether similar technology could be adapted for broader applications, Morris said current conversations remain exploratory. “There have been people discussing ways of potentially amplifying this signal to make it more useful to a larger area,” he said, though that work is still hypothetical.

The recently published paper represents the first in a planned series of studies and can be found at this link: https://onlinelibrary.wiley.com/doi/10.1111/jfb.70220.