Add lights to fishing gear
Overall effectiveness category Awaiting assessment
Number of studies: 5
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Background information and definitions
Reptiles, particularly sea turtles, use visual cues as part of their foraging behaviour (Wang et al. 2009). Taking advantage of this reliance on visual cues by adding lights to fishing gear could be a way to reduce turtle interactions with fishing gear.
See also: Use visual deterrents on fishing gear.
Wang J., Fisler S. & Swimmer Y. (2009) Developing visual deterrents to reduce sea turtle bycatch: testing shark shapes and net illumination. Proceedings – Proceedings of the technical workshop on mitigating sea turtle bycatch in coastal net fisheries, Honolulu, USA, 49–50.
Supporting evidence from individual studies
A replicated, controlled study in 2006–2009 in surface waters of a coastal lagoon and on the sea floor in the Baja California peninsula, Mexico (Wang et al. 2010) found that attaching LED lights to gillnets reduced unwanted catch of green turtles Chelonia mydas. LED-lit nets reduced turtle catch by 40% (7 turtles/12 h x 100 m net) compared to unmodified nets (12 turtles/12 h x 100 m net). Catch of commercially targeted fish was similar in LED-lit nets (11 fish/12h x 200 m net) compared to unmodified nets (11 fish/12 h x 200 m net). Green LEDs were attached every 10 m to the float line of gillnets. LED-lit gillnets were deployed in pairs < 1 km away from nets that had inactive LEDs attached (unmodified nets). In total, 15 trials were carried out at surface level to test sea turtle catch (60–95 m gillnets, July 2006, May-September 2007–2008) and 23 trials were carried out to test fish catch rates on commercial fishing vessels in a bottom-set gillnet fishery (200–400 m gillnets set 200 m apart at 10–30 m depths, May–September 2009). All nets were deployed in the dark.Study and other actions tested
A replicated, controlled study in 2006–2009 in surface waters of a coastal lagoon and on the sea floor in the Baja California peninsula, Mexico (Wang et al. 2010) found that attaching chemical light sticks to gillnets reduced unwanted catch of green turtles Chelonia mydas. Light stick-lit nets reduced turtle catch by 59% (8 turtles/12 h x 100 m net) compared to unmodified nets (19 turtles/12 h x 100 m net). Catch of commercially targeted fish was similar in light stick-lit nets (12 fish/12h x 200 m net) compared to unmodified nets (13 fish/12 h x 200 m net). Green chemiluminescent light sticks (15 cm) were attached every 5 m to the float line of gillnets. Illuminated nets were deployed in pairs < 1 km away from gillnets that had inactive light sticks attached (unmodified nets). In total, six trials were carried out at surface level to test sea turtle catch (60–95 m gillnets, July 2006, May-September 2007–2008and 17 trials were carried out to test fish catch rates on commercial fishing vessels in a bottom-set gillnet fishery (200–400 m gillnets set 200 m apart at 10–30 m depths, May–September 2009). All nets were deployed in the dark.Study and other actions tested
A replicated, controlled, paired study in 2011–2013 on the seafloor in Sechura Bay, northern Peru (Ortiz et al. 2016) found that LED net illuminators reduced unwanted catch of green turtles Chelonia mydas in a bottom-set gillnet fishery. Green turtle bycatch was reduced using illuminated nets (0.5 individuals/km/day) compared to unlit nets (1.4). Commercially-targeted fish species catch was not affected by LED lighting (illuminated: 10.4 individual fish/km/day, unlit: 10.6). Eleven vessels were equipped with a pair of bottom-set gillnets (56.4 x 2.8 m), one without illumination and the other with green LED lights every 10 m along the float line. Boats set lines for a total of 114 overnight deployments. Pairs of nets were separated by 200 m to avoid lighting the control nets. The catch of sea turtles was recorded on board.Study and other actions tested
Referenced paperOrtiz N., Mangel J.C., Wang J., Alfaro-Shigueto J., Pingo S., Jimenez A., Suarez T., Swimmer Y., Carvalho F. & Godley B.J. (2016) Reducing green turtle bycatch in small-scale fisheries using illuminated gillnets: The cost of saving a sea turtle. Marine Ecology Progress Series, 545, 251-259.
A replicated study in 1992–2015 in pelagic longline fisheries in the Atlantic and North Pacific (Swimmer et al. 2017) found that using more light sticks on longlines resulted in a higher chance of catching loggerhead turtles Caretta caretta but had no impact on leatherbacks Dermochelys coriacea (data reported as statistical model results). Pelagic Observer Program data from (1992–2015) was used to determine the number of turtles caught/1,000 hooks, and variation in the number of light sticks/hook (average of 0.4–0.9 sticks/hook) was used to test its effect on bycatch.Study and other actions tested
A randomized, controlled, paired study in 2015–2016 in sandy-muddy bottom habitat in the north Adriatic Sea, central Mediterranean Sea (Virgili et al. 2018) found that using UV lights on bottom-set gillnets led to fewer loggerhead turtles Caretta caretta being caught. No statistical tests were carried out. No turtles were caught in lit gillnets, compared to 16 individuals in unlit gillnets (1 turtle/1,000 m net length/12 h). Five turtles died after being caught. Catch rates of commercially-targeted fish were similar between lit nets (15 individuals/1,000 m net length/12 h; 17 kg catch/1,000 m net length/12 hours) and unlit nets (14 individuals/1,000 m net length/12 hours soaking time; 17 kg catch/1,000 m net length/12 hours soak time). Data were collected in June–July 2015–2016 during 18 fishing trials. Fishing gear included bottom-set gillnets (average depth of deployment: 54 m) comprising connected netting panels (mesh size: 140 mm, panel length: 100 m, 3 m stretched drop). UV LED lights were positioned 15 m apart along the top line (‘floatline’) of some of the net panels (70 lights/km). Lit (3 km average net length) and unlit panels (1 km average net length) were randomly distributed along each net. A gap of 150 m was left between lit and unlit panels. Nets deployed from a single fishing vessel (18:00–06:00 h; average soak time: 15 hours). Catch of target, discard and unwanted species was monitored.Study and other actions tested
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This Action forms part of the Action Synopsis:Reptile Conservation
Reptile Conservation - Published 2021