Students at the University of New England are studying how low-level electrical impulses might be used to repel sharks, a method they hope will protect fishermen’s valuable catch as well as the sharks that too often die trying to steal it.

If the concept proves itself in the field, the students hope to develop a long-lasting, affordable device that recreational and commercial fishermen can add to their lines to stop shark bycatch without hurting their chances at reeling in a halibut in the waters off Maine, or a tuna off Hawaii.

“Fishermen see sharks as a nuisance,” said junior Clayton Nyiri, a marine science major who is running the recreational fishing side of the project. “They’ll steal your bait and, if they can, your fish, too. They’ll swallow the hook whole, so you have to replace it. … All that trouble, but no commercial value.”

The National Oceanic and Atmospheric Administration and National Sea Grant College Program fund research projects like this to protect the economic value of lucrative fisheries, and to protect shark species that are vulnerable to overfishing in part because they are often inadvertently caught by commercial fishermen.

Since 1970, the number of oceanic sharks and rays has declined by 71% because of an 18-fold increase in fishing pressure, including both targeted and accidental catches, putting three-quarters of the species at risk of global extinction, according to a 2021 study by an international team of shark researchers.

Pelagic longliners, which can suspend thousands of individual fishing lines and baited hooks off a main fishing line that can run for miles behind a boat, pose a bycatch threat to several kinds of overfished Atlantic sharks, including scalloped hammerhead, dusky, sandbar and blacknose.

Under the supervision of marine science professor John Mohan, UNE students are now literally fishing for solutions in the Gulf of Maine, dropping lines in the heart of spiny dogfish territory about 11 miles east of the Biddeford campus to see if their devices will repel these slender, compact sharks in the field.

All sharks, including spiny dogfish, have special receptors ampullae of Lorenzini in their snouts to detect electrical fields, which helps them locate and attack their prey. Random electrical pulses should disorient and repel sharks, said Mohan, but not most fish, which lack these receptors.

Mohan’s students attach small cylindrical devices that emit a random pattern of weak, electric impulses to half of their fishing rods, about 8 inches from the baited hooks. If the concept works, the electrified lines should catch groundfish, but no dogfish. The emitter-free control lines should catch both.

Preliminary data shows the first round of emitters appeared to lower shark bycatch by about 50.

During a two-hour fishing lab on a recent weekday, the emitters warded off all but the youngest dogfish, which took the bait despite the presence of a bycatch reduction device. Perhaps the ampullae are not yet fully formed in young sharks, Nyiri said. He wonders if the aggregated data will eventually confirm that theory.

All the fishermen that day hauled in the kind of fish that recreational anglers like to catch, such as mackerel, hake and pollock. And the rods without bycatch reduction devices proved the waters were full of dogfish, bringing in sharks of both sexes and all sizes. Each was carefully measured and documented.

While fishing, Michael Nguyen, 24, a second-year graduate student from New Jersey, talked about work he did in a UNE lab and in the field over the summer testing 300 of these bycatch reduction devices on a commercial long-line boat off the North Carolina coast.

He hasn’t analyzed all the data yet but said it seems to be working. But he also learned that in North Carolina, sharks aren’t long-liners’ biggest bycatch threat. Pilot whales like to steal tuna or swordfish right off the lines there, he said, but the emitters could help solve at least part of the problem.

The challenge is to find a way to make the electrical field around the emitter broad enough to protect not only the baited hook, but the tuna or swordfish that takes the bait, without making the battery-operated device so big that its silhouette alone scares away fish or costs fishermen too much.

It’s a balancing act they’ll have to work out in the field and in the lab, Nguyen said. But fishermen know that every little advance helps them stem the costly bycatch problem, he said.

“They lose a lot of money, and they know it,” Nguyen said. “We are still trying to work out specifics. This is a long way away from being integrated into any commercial fisheries, but there’s a lot of interest, a lot of need, especially now that they see the electrical field isn’t scaring away the tuna.”

UNE is doing this work in partnership with University of Maine assistant professor Walter Golet, who is the head of Gulf of Maine Research Institute’s shark and tuna lab, as well as researchers at Indiana University at South Bend, the North Carolina Sea Grant, and the Virginia Institute of Marine Science.

These electrical emitters are not the only bycatch reduction technique scientists are studying to help fishermen and sharks avoid unwanted entanglements. Others include the use of circle hooks to minimize damage to sharks that are caught, switching to monofilament lines instead of wire and reducing the time fishing lines are left in the water.

Those methods will help sharks survive unwanted entanglements, but they won’t help fishermen protect their catch or their gear. Mohan believes the electrical emitters, which seem to deter sharks from taking that first costly bite, could one day be the solution to both problems.

One issue Mohan is not studying is whether this tech could one day be used to repel sharks from popular swimming beaches, divers, surfers, or spear fishermen. This technology is meant to deter the close-range bite response, within 1 to 2 feet. Maine is not currently involved in any anti-shark measures.

Copy the Story Link

« Previous

Storms muddy future for Maine’s ATV enthusiasts

Next »

Portland man who flew air patrols along Maine coast honored 80 years after World War II