Tens of millions of sharks are caught every year as bycatch -- a term that refers to the capture of non-target species. There are only a few fisheries that don’t catch sharks as bycatch, according to the UN, and some actually catch more sharks than their targeted species. However, a new device could offer a possible solution.
SharkGuard is a small battery-powered device. The device is attached to a baited hook on a line, producing a small, pulsing electrical field. When used, it dissuades sharks from taking the bait, while not affecting other targeted fish.
SharkGuard was able to reduce the number of blue sharks (Prionace glauca) accidentally caught by commercial fishing gear in a French longline tuna fishery by 91% -- and as an added bonus, it also reduced the stingray bycatch by 71%, according to a new study.
"The main implication is that commercial longline fishing may continue, but it won't always necessarily result in the mass bycatch of sharks and rays," Robert Enever, study author, said in a statement, "This is important in balancing the needs of the fishers with the needs of the environment and contributes to biodiversity commitments.”
Testing the device
To find out how well the device worked, Enever and the group of researchers did a set of sea trials between July and August 2021 in southern France. Two fishing vessels fished 22 longlines on 11 trips, deploying over 18,000 hooks. The findings show SharkGuard significantly reduces the number of bycatches in blue sharks and stingrays.
Catch rates of bluefin tuna weren’t significantly influenced by the presence of SharkGuard on the hook, the study showed. The device offers a more comprehensive solution than catching and releasing bycaught species. If scaled up to the level of whole fisheries, it would reduce interaction between sharks and fishing gear, the researchers argued.
However, SharkGuard also comes with limitations, such as the need for frequent battery changes. The researchers are working to overcome this, so fishers can deploy it and forget about it while protecting species from bycatch. A full set of SharkGuard devices for 2,000 hooks would cost about $20,000 and last from three to five years.
The researchers hope the device will be commercially available by 2024. As well as working on the batteries, they wish to make it smaller so it can be operationally viable for fishermen. Based on the results obtained in the trial, they have high hopes the SharkGuard can make a big difference in reducing shark bycatch once deployed.
“Against the relentless backdrop of stories of dramatic declines occurring across all species, it is important to remember that there are people working hard to find solutions,” Enever said in a statement. “SharkGuard is an example of where, given the appropriate backing, it would be possible to roll the solution out on a sufficient scale.”
The study was published in the journal Current Biology.
