MEPS 306:295-302 (2006)  -  doi:10.3354/meps306295

Foraging of the green sea turtle Chelonia mydas on seagrass beds at Mayotte Island (Indian Ocean), determined by acoustic transmitters

Coralie Taquet1,2,*, Marc Taquet1, Tim Dempster3, Marc Soria4, Stéphane Ciccione5, David Roos1, Laurent Dagorn6

1Institut Français de Recherche pour l’Exploitation de la Mer (IFREMER), rue Jean Bertho, BP 60, 97822 Le Port Cedex, France
2Institut National Agronomique de Paris-Grignon (INA P-G), 16 rue Claude Bernard, 75005 Paris 5ème, France
3SINTEF Fisheries and Aquaculture, 7465 Trondheim, Norway
4Institut de Recherche pour le Développement (IRD), Campus Universitaire du Moufia, BP 172, 97492 Sainte-Clotilde Cedex, France
5Centre d’Etude et de Découverte des Tortues Marines (CEDTM), BP 40, 97898 Saint Leu Cedex, France
6Institut de Recherche pour le Développement (IRD), BP 570, Victoria, Mahé, Seychelles

ABSTRACT: We studied the foraging rhythms of green sea turtles Chelonia mydas on the seagrass beds of N’Gouja Bay, Mayotte Island (Comoros Archipelago) with acoustic transmitters and moored listening stations. We monitored 8 tagged turtles (4 probable males, 3 probable females and 1 immature), from 70 to 109 cm curved carapace length (CCL), for durations ranging from 5 to 92 d. The turtles exhibited a regular diel pattern: they foraged mainly during the day (on average 87% of seagrass detections were between 06:00 and 18:00 h) and rested on the inner reef slope during the night. Night time feeding activities were observed on the seagrass bed when the night light was high. The presence of turtles on the seagrass bed at night was significantly correlated with a night light index (r = 0.54, p = 0.002), which included both moon light and cloudiness indices. Behaviour of the only immature individual observed was similar to adult turtles, although it rested more frequently around noon. All turtles displayed a high fidelity to 1 foraging site within the seagrass bed. Acoustic transmitters and permanent listening stations are an appropriate technique for long-term behavioural studies of turtles, with no human interaction with turtles during tracking, and represent a suitable technique to assess the possible effects of environmental changes or human activities upon green turtle behaviour.

KEY WORDS: Chelonia mydas · Southwestern Indian Ocean · Mayotte · Green sea turtle · Acoustic transmitter · Listening station · Foraging rhythm

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