Increased visibility with illuminated nets

Increased visibility with illuminated nets The sun sets as fishermen set out nets with green LED lights attached. Photo: NOAA Pacific Islands Fisheries Science Center.

Scientists are testing nets illuminated with LED lights to see if increasing net visibility reduces sea turtle bycatch in gillnet fisheries.

Studies comparing traditional nets with illuminated nets show that nets made more visible with simple LED lights can reduce by-catch of sea turtles without reducing target catch. Studies in Mexico show green sea turtle bycatch is reduced between 40-60% with no changes in target catch.

Studies in Peru show green sea turtle bycatch is reduced between 65-80% with no changes in target catch, while studies in Indonesia show green, Olive Ridley and hawksbill sea turtle by-catch is reduced by 60% with increases of target catch and catch value.

In addition, recent research indicates that net illumination also reduces by-catch of other protected species such as seabirds, elasmobranchs, and cetaceans.

The use of illuminated gillnets could prove beneficial for both sea turtles and fishermen by reducing sea turtle bycatch and damage to gear.

In North Carolina, inshore state gillnet fisheries are carefully managed to reduce by-catch of sea turtles. Researchers from Duke University and NOAA Fisheries are collaborating with North Carolina coastal fishermen and the North Carolina Fishermen’s Association. They are testing the effectiveness of net illumination in the coastal flounder fishery. Initial studies indicate that net illumination does not change target catch rates and may decrease the by-catch of unwanted fish species. These findings could one day provide more options for fishermen to continue fishing.

John Wang leads gillnet bycatch research at the NOAA Pacific Islands Fisheries Science Center. He and his colleagues studied sea turtle vision and tested LED lights in different wavelengths (green, orange, ultraviolet) to see if they had different effects. All of the lights reduced sea turtle by-catch at a similar rate without impacting target species catch.

Scientists are also investigating the effectiveness of sound as a deterrent. They have equipped nets with audio devices that emit an acoustic signal to alert turtles to the net and deter them. John Wang said the next step is to combine the two existing approaches – lights and sound – into one gillnet experiment, to see if this combination can reduce by-catch even more.

Ultimately, he hopes that these gillnet bycatch reduction techniques can be used in international communities in Indonesia and the Philippines to protect the highly endangered Pacific leatherback turtle.

“These turtles migrate vast distances across the Pacific, traveling from Indonesia to the U.S. Pacific Islands and back many times during their lifetime,” he explained. “If we want to protect our species and fisheries, we need to work to implement better practices worldwide.”

NOAA regularly provides technical advice and support to international partners seeking to reduce gillnet by-catch. Interest in gillnet by-catch reduction techniques is growing worldwide. Research into net illumination is also taking place in other fisheries, such as Pakistan’s drift gillnet fishery, the Italian/Slovenian/Croatian coastal gillnet fisheries in the Adriatic, small-scale fisheries in Gabon, coastal fisheries in Turkey and Ecuadorian gillnet fisheries.

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