Solar-powered lights keep sea turtles out of fishing nets

(Press-News.org) Studies have shown that lighted nets can reduce bycatch of sea turtles and sharks, but the idea has faced many hurdles to adoption. The batteries are short lived, expensive to replace and raise disposal concerns. The lights are too heavy and prone to snagging nets. Fishers find them difficult to work with.

To get past these hurdles, researchers at Arizona State University collaborated with a team of coastal gillnet fishers to develop solar-powered lights that function as buoys, like any others threaded onto the float line of a fishing net. The LED lights flash on and off to conserve energy and can stay active for over five days with no sunlight.

The net-illuminating gear is highly effective at preventing sea turtles from entanglement in gillnets, ASU marine biologist Jesse Senko and colleagues report in a new study published in Conservation Letters. In controlled experiments in Mexico’s Gulf of California, sea turtle bycatch rates were 63% lower in the solar-powered illuminated nets compared to unlit control nets. And the lighted buoys did not interfere with fishing success. The researchers recorded higher catch rates of targeted yellowtail fish in the illuminated nets, although the difference was not statistically significant.

“The results were pretty exciting,” said Senko, an assistant professor in the ASU School of Ocean Futures. He said the study is the first to show the effectiveness of harnessing solar energy and flashing light to deter sea turtles from fishing nets. “It's a win-win in the sense that you're getting a light that lasts significantly longer, and it also seems to reduce bycatch just as effectively as lights that require replaceable batteries.”

Fishing gear entanglement is a primary threat to endangered sea turtles, along with climate change, pollution, habitat loss and emerging diseases. Despite signs of recovery among some species, current population numbers remain a small fraction of the total that once existed.

“Sea turtles are important for maintaining healthy oceans, which are needed to sustain resilient fisheries,” Senko said. “They have been around for over a hundred million years, and they fulfill ecological roles that no other species fulfill.”

Senko has made it a priority in his lab to work with fishers to develop ways to make fishing gear less harmful to sea turtles, sharks and other threatened species. The goal is to develop practical solutions that can be widely deployed to reduce wasteful bycatch while maintaining productive fisheries.

In coastal North Carolina, where many forces have threatened the fishing way of life, Senko Lab members are collaborating with fishers to reduce bycatch in pound nets, bottom-anchored net systems that funnel fish into a trap. The ASU researchers are comparing the numbers of turtles, sharks and other species caught in nets on days with or without solar-powered lights. They are also gathering observations of sea turtle behavior never seen before using custom-designed underwater video cameras and data recorders.

Sustaining resilient fisheries

Small-scale coastal fisheries provide nearly half of the world’s seafood, Senko points out, and they are crucial to sustaining coastal communities with food, income, and livelihoods.

The idea for integrating solar-powered LED lights into buoys came from fishermen in Mexico, brothers Juan Pablo Cuevas Amador and Felipe Cuevas Amador, who are co-authors of the new study.

"They took us into account and gave us the freedom to give our opinions and make modifications,” said Juan Pablo Cuevas Amador. “For us, it's important that it be done in collaboration because with what they know and what we know, we can do quite interesting things.”

Senko said fisher-led ideas are “where the real magic happens; that's the meaningful innovation. Because their ideas went into it, they're more likely to want to use it and to share that information with their friends and their community and with neighboring communities.”

After completing the fishing experiments, the Cuevas Amador brothers asked Senko if they could keep the solar-powered lighted buoys. The gear made fishing easier because they no longer had to waste much time and effort removing turtles from nets.

“When I heard that, I knew we were onto something,” Senko said. “And they've been fishing with these lights ever since. As far as we know, they are the only fishers on the planet fishing with solar-powered lighted nets.”

Senko and colleagues are now working with a manufacturer, Fishtek Marine, to produce commercially available solar-powered lighted buoys for fishing nets. Senko said it’s possible to make them available for purchase within 2 to 3 years. Research on their effectiveness could encourage conservation organizations and government agencies to provide grants or subsidies to help fishers buy them. Senko has received funding for the research from Schmidt Marine Technology Partners, the Disney Conservation Fund, and the National Philanthropic Trust.

The researchers are pursuing future studies to understand the behavioral responses of sea turtles to flashing light, and use that knowledge to maximize the deterrent effects of net illumination.

“A 63% reduction in sea turtle bycatch is a magnificent starting point. However, there's no reason why that can't be improved, right?” Senko says. “My goal is how do we get that 63% reduction to a 95% reduction.”

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