Novel use of a shark model to elicit innate behavioral responses in sea turtles: application to bycatch reduction in commercial fisheries

Published source details Bostwick A., Higgins B.M., Landry A.M. & McCracken M.L. (2014) Novel use of a shark model to elicit innate behavioral responses in sea turtles: application to bycatch reduction in commercial fisheries. Chelonian Conservation and Biology, 13, 237-246.
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This study is summarised as evidence for the following.

	Action	Category
	Use visual deterrents on fishing gear Action Link

Use visual deterrents on fishing gear

A replicated, controlled study (year not given) in laboratory conditions in Texas, USA (Bostwick et al. 2014) found that shark-shaped and spherical deterrents did not deter captive-reared loggerhead turtles Caretta caretta from biting squid bait, but that shark models resulted in changes in four out of five behaviours prior to biting compared to when spheres or no deterrent was used. The number of trials in which turtles did not bite the squid was similar across treatments (shark model: 11%; sphere: 9%; no deterrent: 3%). Turtles took longer to bite the squid in the presence of the shark model compared to no deterrent (shark model: 5 minutes; no deterrent: 2 minutes), but the time was statistically similar to when the sphere was used (2 minutes). Turtles approached the squid fewer times in the presence of the shark model (10 times/15 minutes) compared to the sphere (13 times) and no deterrent (16 times). Time spent away from the bait and the number of carapace turns were also affected by the deterrent, but the number of breaths taken was not (see paper for details). Forty-two captive-reared turtles (30–33 months old) were individually presented with either a shark model (91 cm long) with squid bait, a sphere (28 cm diameter) with squid bait or just a squid in three separate trials (1 turtle/trial). Turtles had a gap of three weeks between each trial and were fasted for three days before the trial started. Trials were conducted in a fibreglass tank (90 x 74 x 406 cm) with a water depth of 59 cm. Trials (15 minute acclimation and 15 minute trial) were video recorded, and the six behaviours were measured.

(Summarised by: William Morgan)