How LED Lights Could Stop Sea Turtle Deaths
Researchers have found a bright way to keep them out of fishing nets
Sometimes a light bulb goes on and illuminates a simple solution to a vexing problem. And sometimes that solution involves light bulbs, or in this case, green battery-powered LEDs.
The problem: Sea turtles die when they’re caught in fishing nets because they’re unable to surface for air.
The solution: Using $2 battery-powered LED lights to illuminate fishing nets and keep the turtles out.
Conservation biologists at University of Exeter, with support from the UK Government’s Darwin Initiative and the National Oceanic and Atmospheric Administration (NOAA), conducted an experiment in northern Peru’s Sechura Bay to see how well the idea works.
"The specific idea for this work came from our co-authors John Wang and Yonat Swimmer at NOAA," Jeffrey Mangel, PhD, one of the lead authors on the paper, told SafeBee. "More generally, the idea of using the lights comes from asking how we can change the behavior of animals, in this case sea turtles, in ways that can reduce their interactions with fishing gear."
The bay is an active fishing ground. Some 100,000 kilometers (more than 62,000 feet) of net is cast each year, according to a University of Exeter press release. It’s also a popular feeding spot for a variety of sea turtles, thousands of which die as bycatch, or by being unintentionally caught by the net.
"Bycatch is a complex, global issue that threatens the sustainability and resilience of our fishing communities, economies and ocean ecosystems," said Eileen Sobeck, assistant NOAA administrator for fisheries, in a press release. "Funding research like this is key to NOAA's efforts to reduce bycatch. Through this work, we can better protect our natural resources."
In the study, the lights effectively warned turtles away from the nets and reduced the number of green turtle deaths by 64 percent without reducing the fish catch. "Basically we think that the light makes the net more visible in the water so the turtles are more alert, able to react to it, and avoid becoming entangled," says Mangel.
The cost of saving one turtle would amount to $34, the researchers note, but that figure could come down if the solution were rolled out on a larger scale.
“The turtle populations in the eastern Pacific are among the world’s most vulnerable and we are hoping that reducing bycatch, particularly in gillnets, will help with the management and eventual recovery of these populations,” says Mangel.
For the experiment, the researchers used 114 pairs of fishnets, about 1640 feet in length. In each pair, one net was illuminated with green LEDs every 32 feet along the float line (the top border of the net). The illuminated nets caught 62 green turtles; the others, 125.
Now the researchers are working with bigger Peruvian fisheries to see if the results can be repeated while also trying out different colored lights.
"Our hope is that this technology could be broadly applied to other turtle species and habitats. We are actively testing LEDs to address those issues. Next steps in the research — all of which are underway — are to test LED lights in other types of net fisheries, in terms of the types of nets but also the target catch and with different species of sea turtle bycatch, to see if we can replicate the results of this study. And we are testing these lights in fisheries that also suffer from bycatch of seabirds and small cetaceans," says Mangel.
The study was published in the Marine Ecology Progress Series journal.
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