How the fishing industry can save sharks and seafood with LED lights

NEW YORK (BLOOMBERG) - LED lights can save more than energy. A first-of-its kind study found that when attached to fishing nets, they dramatically reduce the incidental killing of sharks and other top predators that help keep marine ecosystems healthy and seafood on dinner plates.

Global shark populations have plummeted 71 per cent since 1970, largely due to overfishing and the inadvertent capture of the species in fishing nets, according to a 2021 paper.

The biomass of this bycatch of sharks and rays, however, fell 95 per cent when researchers placed green LED lights on more than 4.9km of nets off Mexico's Pacific coast, scientists wrote in a peer-reviewed paper published in the journal Current Biology.

The researchers from the United States and Mexico found that overall bycatch declined 63 per cent compared with control nets that were not lit. That included a 51 per cent drop in the killing of endangered loggerhead turtles and an 81 per cent drop in the capture of giant Humboldt squid, another top predator. That also meant that fishermen improved their productivity as they spent 57 per cent less time untangling unwanted species from their nets, according to the researchers.

Past studies have documented how LED lights can deter sea turtles from entering fishing nets. But the Mexico research is the first to show how illuminating nets can benefit a range of marine species that are also under pressure from climate change, said Dr Jesse Senko, lead author of the study and an assistant research professor and senior sustainability scientist at Arizona State University.

"The implications are huge," he said. "These top predators regulate prey populations and transfer nutrients in the marine ecosystem. When you remove them, there are a lot of ecological consequences."

The researchers wrote that it was unclear if sharks and rays are disturbed by the LEDs and avoid nets, or if the illumination allows them to see the nets and steer clear of entanglement.

In Mexico, the LEDs were attached to gill nets, which are vertical walls of fine-mesh material that can stretch for more than a mile and are nearly invisible to marine mammals and fish. Dr Senko said experiments indicate that LEDs are also effective when attached to other types of nets.

Dr Senko said that fishermen in Mexico embraced the LEDs as the drop in bycatch allowed them to return to port faster and more profitably sell their catch as it was fresher.

Still, obstacles to the widespread deployment of the lights remain. Each LED costs about US$7 (S$9.40) and run on batteries that must be frequently replaced. "That's a huge recurring operational cost for them," said Dr Senko.

He and his colleagues have developed a solar-powered LED that can operate for a week on an hour of sunlight and is currently being tested in Mexico.

Dr Michel Kaiser, a professor of fisheries conservation and chief scientist at Heriot-Watt University in Edinburgh, Scotland, was not involved in the research but he said in an e-mail that the study's results are "very encouraging".

He said, though, that more research is needed on the impacts of illuminating fishing nets with LEDs.

"There are critical questions that need to be answered - namely what wavelengths of light work best and how do different species respond to different wavelengths," said Dr Kaiser, who is conducting research with SafetyNet Technologies, a company that makes LEDs for fishing nets. "Some are attracted to light, others are repelled by light - hence this could cause complications in some mixed-species fisheries."