Simple Green LED Lights Save Sharks and Turtles from Accidental Bycatch in Fishing Nets

February 9, 2022January 31, 2023 journo

Marine biologists have found that $8 green LEDs affixed to fishermen’s gill nets were enough to dissuade huge amounts of sea animals like turtles, rays, and sharks from falling prey to these nets.

Originally tested by the National Oceanic and Atmospheric Administration on sea turtles off the coast of Hawai’i, they are proving even more effective on Humboldt squid and the elasmobranch family which contains sharks and rays.

Gill nets are indiscriminate, and if a fisherman snags a thrashing shark, a four foot-long Humboldt squid—known in Spanish as the “Red Devil”—or an unwelcome stingray, it can be incredibly dangerous entangling them without out-rightly killing them first.

Termed bycatch, the catching of unsought marine life accounts for 40% of all net-caught animals around the world, and has been a major threat to sharks, rays, and turtles.

Jesse Senko, a biologist at the State University of Arizona’s School of Life Sciences, found that just a few green lights reduced the amount of elasmobranch and squid caught in fisherman’s nets by 95% and 81% respectively.

The all-important loggerhead sea turtle was also bycaught 51% less frequently.

Furthermore, even non-game species of fish steered clear of the green light more than in the unlit control nets.

“We were stunned with our findings,” one researcher told Reuters.

In their study published in Cell, Senko and the rest of the research team compared 5,000 lit nets to 5,000 unlit nets off the coast of the Baja Peninsula in Mexico, where several species of sharks and rays are declining due to bycatch, including the devil and manta rays.

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Somehow, even though regular non-game fish were reduced, there was no difference statistically in the amount of game species caught in the lit and unlit nets, meaning there was no change to fishermen’s income.

“Regardless, the increased operational efficiency and reduction in total bycatch could justify the costs to fishers that convert to illuminated nets. In cases of high biodiversity and conservation importance, governments and NGOs could subsidize their adoption,” Senko wrote.

“In other gillnet fisheries, net illumination has been estimated to cost as little as $16 to $34 to prevent a sea turtle bycatch event. We encourage conservation practitioners, fishery managers, and other stakeholders to work with industry to develop new technologies, domestically manufacture LED lights, and seek new methods to increase efficiency and availability.”

One of the unexpected and rather cool reactions of reducing this bycatch was the amount of time it took to haul in and untangle nets, saving an average of 63 minutes per trip.

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