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Marine Ecology Progress Series

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MEPS 600:165-177 (2018)  -  DOI:

Stable isotopes reveal dietary differences and site fidelity in juvenile green turtles foraging around São Tomé Island, West Central Africa

Joana M. Hancock1,2,3,*, Sara Vieira3, Victor Jimenez3, Jorge Carvalho Rio4, Rui Rebelo1

1cE3c - Centre for Ecology, Evolution and Environmental Changes, Faculty of Sciences, University of Lisbon, 1749-016 Lisbon, Portugal
2CIBIO - Research Centre in Biodiversity and Genetic Resources, University of Porto - Campus do Vairão, 4485-661 Vairão, Portugal
3Associação Programa Tatô - Sítio da Pedragosa, 8600-013 Barão de São João, Portugal
4MARAPA - Mar, Ambiente e Pesca Artesanal, CP 292 São Tomé, São Tomé e Príncipe
*Corresponding author:

ABSTRACT: Green sea turtles are common in West Central Africa, but little is known about the occurrence of immatures in foraging grounds in the Gulf of Guinea islands, known for their volcanic origin and narrow coastal fringes. This study presents results of in-water surveys in foraging grounds off São Tomé Island, in the São Tomé and Príncipe archipelago, providing the first available data on the size distribution of immature green sea turtles of different life-stage groups on these islands. Two sites offering distinct types of food sources were studied, and isotopic signatures of immature turtles hand-captured at each foraging site were used to infer (1) how long they were established at the foraging sites and (2) their diet preferences. Recruitment in the region was estimated to occur at a minimum size of 34 cm curved carapace length (CCL), and resident immature turtles ranged from 53 to 87 cm CCL. Immatures sampled at each site showed clear differences in isotopic signatures, suggesting that they establish specific home ranges related to the available diet items and use them for extended periods of at least several months. Macroalgae were as important as or more important than seagrasses for the turtles’ diets, and there was evidence that these individuals are not strictly herbivorous. Our study provides the first dataset for comparison with demographic data from other locations in West Africa, where current knowledge on green turtle foraging behavior is limited, and indicates that even oceanic islands that are geologically recent like São Tomé may provide important recruitment and development habitats for juvenile green turtles.

KEY WORDS: Chelonia mydas · Settlement · Stable isotopes · Foraging ecology · Gulf of Guinea

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Cite this article as: Hancock JM, Vieira S, Jimenez V, Carvalho Rio J, Rebelo R (2018) Stable isotopes reveal dietary differences and site fidelity in juvenile green turtles foraging around São Tomé Island, West Central Africa. Mar Ecol Prog Ser 600:165-177.

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