Diving behavior and delayed mortality of olive ridley sea turtles Lepidochelys olivacea after their release from longline fishing gear

  • Published source details Swimmer Y., Arauz R., McCracken M., McNaughton L., Ballestero J., Musyl M., Bigelow K. & Brill R. (2006) Diving behavior and delayed mortality of olive ridley sea turtles Lepidochelys olivacea after their release from longline fishing gear. Marine Ecology Progress Series, 323, 253-261.


This study is summarised as evidence for the following.

Action Category

Release accidentally caught (‘bycatch’) reptiles

Action Link
Reptile Conservation
  1. Release accidentally caught (‘bycatch’) reptiles

    A controlled study in 2001–2003 in pelagic waters on the Pacific coast of Costa Rica (Swimmer et al. 2006) found that sea turtles released back into the water after becoming caught on longline hooks travelled similar distances and dived to similar depths compared to free-swimming turtles. Longline-caught turtles travelled similar total distances (117–520 nautical miles) and distances each day (5 nautical miles/day) compared to free-swimming turtles (total distance: 50–443 nautical miles; 5 nautical miles/day). Longline-caught turtles made similar depth daily maximum dives (81–408 m) compared to free-swimming turtles (84–264 m). Longline-caught turtles made more deeper daytime dives than free-swimming turtles, which were more likely to make deeper dives at night (no statistical tests carried out, see original paper for details). None of the longline-caught turtles died during the study; one free-swimming turtle mortality occurred. In total nine olive ridley turtles Lepidochelys olivacea and one green turtle Chelonia mydas caught by fishermen were monitored using radio tags in November 2001–August 2003. Hooks were removed from the turtle’s jaw or mouth (except for one individual, see paper for details) and turtles were released. At the same time, five free-swimming olive ridley turtles were collected by the boat, radio-tagged and released for behavioural comparisons. On average, tags remained on line-caught turtles and free-swimming turtles for 54 and 60 days respectively.

    (Summarised by: Katie Sainsbury)

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