Developing visual deterrents to reduce sea turtle bycatch in gill net fisheries

Published source details Wang J.H., Fisler S. & Swimmer Y. (2010) Developing visual deterrents to reduce sea turtle bycatch in gill net fisheries. Marine Ecology Progress Series, 408, 241-250.
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This study is summarised as evidence for the following.

	Action	Category
	Add lights to fishing gear Action Link
	Use visual deterrents on fishing gear Action Link
	Add lights to fishing gear Action Link

Add lights to fishing gear

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.

(Summarised by: Katie Sainsbury)
Use visual deterrents on fishing gear

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 floating shark shapes to gillnets reduced unwanted catch of green turtles Chelonia mydas. Shark shapes attached to nets reduced the catch of green turtles by 54% (6 turtles/12 h soak of 100 m net) compared to unmodified nets (12 turtles/12 h soak of 100 m net). Commercially-targeted fish catch was reduced in nets with shark shapes (6 fish/12 h soak of 200 m net) compared to unmodified nets (11 fish/12 h soak of 200 m net). Dark-painted cut-out shark shapes were weighted and attached every 10 m to gillnets. Shark nets were deployed in pairs with unmodified nets < 1 km away. In total, 14 trials were placed at the surface to test sea turtle catch (60–95 m gillnets, July 2006, May–September 2007–2008) and 22 trials were carried out to test fish catch rates on commercial fishing vessels in a bottom-set gillnet fishery (200–400 m nets set 200 m apart at 10–30 m depths, May-September 2009). All nets were deployed in daylight.

(Summarised by: Katie Sainsbury)
Add lights to fishing gear

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.

(Summarised by: Katie Sainsbury)