SharkGuard reduces bycatch of endangered sharks, sea trials show

For sharks living in the open ocean, longline fishing is the main threat, with an estimated 20 million pelagic sharks caught each year by fishermen looking for tuna and other desirable species. Now a new study is reported in Modern biology Nov. 21 shows that a new technology known as SharkGuard could allow longline fishing to continue while halting a sharp decline in the number of endangered sharks worldwide.

“The bottom line is that commercial longline fishing can continue, but it will not always result in massive bycatch of sharks and skipjack,” said Robert Enever of Fishtek Marine, Dartington, Devon, UK. “This is important to balance the needs of fishermen with the needs of the environment and contributes to national and international biodiversity commitments for long-term sustainability.”

Enever and his colleagues saw a huge need to slow or even reverse the decline of global shark populations, based on evidence that more than 100 million sharks, skates, and rays are caught by commercial fisheries worldwide each year. A quarter of sharks and rays are now classified as endangered. They thought that shark deterrents were a promising means of protection scuba divers and shark surfers will also be used in the tuna fishery to protect sharks from bycatch.

How does it work?

SharkGuard emits a small, localized, pulsating electric field. When joining the Art fishing line, it creates an electric field around the baited hook. The goal is to prevent sharks and anglers, which pick up electrical signals through their electroreceptors, from biting without preventing other fish from being hooked.

To find out how well it works, the researchers conducted sea trials in July and August 2021 in the south of France. Two fishing vessels caught 22 lines in 11 separate trips, running a total of over 18,000 hooks. Their findings showed that SharkGuard hooks significantly reduced the number of blue sharks and pelagic rays caught compared to standard control hooks. Catch rates of these species per unit effort decreased by 91% and 71% for sharks and walleyes, respectively. The presence of SharkGuard in the bluefin tuna fishery did not significantly affect the catch a hook.

“Sharks are not baited or hooked,” Enever said.

The researchers note that compared to the catch and release of captured animal species, including sharks, SharkGuard offers a more comprehensive solution. If its use were scaled up to the level of all fisheries, it would mean a significant reduction in the interaction between sharks and fishing gear.

However, the device currently has limitations, including the need to change the battery frequently. They are now working to overcome this barrier so that fishermen can “fit and forget” while maintaining protection sharks and other types of bycatch. A full 2,000-hook inductively charged SharkGuard device set is expected to cost around $20,000 and last three to five years (~$4-7k per year), which they note is a modest annual cost for most commercial tuna fishing operations.

They are now encouraging fishermen experiencing high bycatch of sharks and rays, as well as retailers looking to improve the sustainability of their supply chain, to seek contact with Fishtek Marine as soon as the commercialization of sea trials and engineering is planned.

“There is hope,” Enever said. “Amidst the relentless stories of drastic declines in all species, it’s important to remember that there are people working hard to find solutions. SharkGuard is an example of where, with the right support, a solution could be implemented on a scale sufficient to reverse the current decline in global shark populations.”