Electrical pulses help keep sharks and stringrays away from fishing nets

University of Exeter researchers and conservation engineers at Fishtek Marine developed the ‘SharkGuard’ device, which attaches to longline fishing rigs to scare off sharks and rays.

It tested the device on French boats fishing for tuna and saw reductions in so-called bycatch (i.e. accidental catching) of blue sharks by 91 per cent and stingrays by 71 per cent.

Powered by a small battery, the device works by targeting the area around a shark’s nose and mouth, which is packed with electrical sensors, called the ampullae of Lorenzini.

These sensory organs get overstimulated by the electric field generated by the line’s pulse device, which makes the sharks swim away from the danger of the baited fishing hooks.

Catch of the target species, bluefin tuna, also appeared to decline, but further testing is needed to fully understand the effects of the device on target species.

“Many shark and ray populations are declining due to overfishing, particularly oceanic species such as blue sharks and pelagic stingrays that are commonly caught on longlines globally,” said Exeter researcher Dr Phil Doherty.

“There is an urgent need to reduce bycatch, which not only kills millions of sharks and rays each year, but also costs fishers time and money.

“Our study suggests SharkGuard is remarkably effective at keeping blue sharks and pelagic stingrays off fishing hooks.”

While the tests saw significantly reduced catch of bluefin tuna (42 per cent), the total number caught in the test period on both lines with and without SharkGuard was also low, so further trials are needed to fully explore the results.

“On the back of these exciting results, the engineers at Fishtek Marine are modifying SharkGuard so it is smaller and self-charging after every haul,” said Dr Doherty.

“Research will continue at Exeter, where we test SharkGuard’s effectiveness at sea across multiple species and fisheries”.

Pete Kibel, co-founder and director of Fishtek Marine, said: “When SharkGuard is used, sharks do not take the bait and do not get caught on the hooks and that gives us a huge sense of hope.

“Against the relentless backdrop of stories of dramatic population declines occurring across all of our marine species, it is important to remember that there are people working hard to find solutions.

“SharkGuard is an example of where, given the appropriate backing, it is possible to roll the solution out on a sufficient scale to reverse the current decline in global shark populations.”

Researchers have previously found that attaching LEDs to fishing nets to indicate an available exit hole for non-target species could help to minimise bycatch.