Abstract
Loggerhead turtles nesting in the Mediterranean Sea exhibit remarkable genetic structuring. This paper tests the hypothesis that young loggerhead turtles from different rookeries do not distribute homogeneously among the major Mediterranean foraging grounds, due to a complex pattern of surface currents. We extracted long fragments of mitochondrial DNA from 275 stranded or bycaught juvenile turtles from six foraging grounds (Catalano-Balearic Sea, Algerian basin, Tyrrhenian Sea, Adriatic Sea, northern Ionian Sea and southern Levantine Sea). We used a Bayesian mixed-stock analysis to estimate the contributions from rookeries in the Mediterranean, the North-west Atlantic and Cape Verde to the studied foraging grounds. Differences were found in the relative contribution of juvenile turtles of Atlantic and Mediterranean origin to each foraging ground. A decreasing proportion of Atlantic juveniles was detected along the main surface current entering the Mediterranean, with a high prevalence of turtles from eastern Florida in the Algerian basin and lower numbers elsewhere. In regard to the turtles of Mediterranean origin, juveniles from Libya prevailed in central and western Mediterranean foraging grounds other than the Algerian basin. Conversely, the Adriatic Sea was characterised by a large presence of individuals from western Greece, while the southern Levantine Sea was inhabited by a heterogeneous mix of turtles from the eastern Mediterranean rookeries (Turkey, Lebanon and Israel). Overall, the distribution of juveniles may be related to surface circulation patterns in the Mediterranean and suggests that fisheries might have differential effects on each population depending on the overlap degree between foraging and fishing grounds.
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Acknowledgments
We are thankful to all the researchers, assistants and volunteers who collaborated in sample collection. This study was cofunded by projects CGL2009-10017 and CTM2010-22218 of the Spanish Government (CICYT) and partially funded by the EU project Protección de Praderas de Posidonia en LICs de Baleares LIFE00NAT/E/7303 and Zoo de Barcelona. The tissue samples used in this paper were provided by the BMA tissue bank managed by the Fundació Bosch i Gimpera with the support of the Fundació pel Desenvolupament Sostenible and by the Italian TARTANET network of rescue centres, with a special thanks to Marco Affronte of Fondazione Cetacea, Giovanni Furii of Legambiente Oasi di Lago Salso and Annalisa Liotta of CTS Brancaleone. Marcel Clusa was supported by the Biodiversity Research Institute (IRBio) of the University of Barcelona and Carlos Carreras by the Beatriu de Pinós programme of the Generalitat de Catalunya. All the IRBio authors are part of the research groups 2009SGR-842 and 2009SGR-636 of the Generalitat de Catalunya. JT and JAR are supported by project PROMETEO/2011/40 of the Generalitat Valenciana and project CGL2011-30413 of the Spanish Ministry of Sciences and Innovation. Maps created with Maptool (www.seaturtle.org). We thank Michele Masuda for her help with Bayes and Gregg Ashcroft for English grammar corrections.
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Clusa, M., Carreras, C., Pascual, M. et al. Fine-scale distribution of juvenile Atlantic and Mediterranean loggerhead turtles (Caretta caretta) in the Mediterranean Sea. Mar Biol 161, 509–519 (2014). https://doi.org/10.1007/s00227-013-2353-y
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DOI: https://doi.org/10.1007/s00227-013-2353-y
Keywords
- Libya
- Loggerhead Turtle
- Nest Beach
- Mediterranean Origin
- Atlantic Origin