November 14, 2013 — Because banning fishing altogether would do serious harm to local economies, conservationists have instead sought ways to warn sea turtles away from fishing nets. Studies have shown that the turtles can perceive light across the visible spectrum as well as into the ultraviolet, whereas the visual sensitivity of many fish drops off just before the UV range. “When we compare the visual spectrums, there's this disparity between what turtles and fish see,” says John Wang, a fisheries researcher at the University of Hawaii at Manoa. “That means there's a selective communication channel in the UV range where we could perhaps communicate to turtles but not to fish.”
Wang and his colleagues teamed up with fishers in Baja California Sur, Mexico, to experiment with reusable, battery-powered UV LEDs as a turtle deterrent. By securing UV lights at five-meter intervals on fishers' gill nets, they reduced accidental sea turtle capture, or bycatch, by around 40 percent, as compared with control nets with inactivated LEDs, the team recently reported in Biology Letters. Although the illuminated nets trapped slightly fewer fish than the control nets, the researchers found no significant difference in the financial value of the two catches.