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Surface circulation patterns drive the genetic structuring of juvenile loggerhead turtle populations in the Mediterranean sea

Dimitris Margaritoulis, ALan F. Rees,Thomas E. Riggal
ARCHELON, the Sea Turtle Protection Society of Greece, Athens, Greece
he Bay of Kyparissia in western Peloponnese, Greece, contains the second largest nesting aggregation of loggerhead turtles in the
Mediterranean. The Bay’s coastline includes a 44km long beach from the river Alfios in the north to the river Arcadikos in the
south. Although turtles nest along the entire beach, the majority of nesting (about 84%) occurs within the southernmost 9.5km which is
considered the core area. Since the early 80s, ARCHELON has undertaken a long-term monitoring and conservation project in
Kyparissia Bay. Tagging of nesting turtles started in 1982 and was performed in the core nesting area. Two types of tags were used:
metal Monel 681-style tags on front flippers and plastic Jumbo Rototags usually on hind flippers. In total 1,358 loggerheads were tagged
during the period 1982-2012. Of the tagged turtles, 69 individuals (5.1%) were recovered from 1 September 1985 until 5 June 2013, at
various localities in the Mediterranean; specifically 27 in the Ionian Sea (incl. 3 in the Gulf of Taranto), 20 in northern/central Adriatic,
9 in the Gulf of Gabes, 8 in the Aegean Sea, 3 in the eastern Mediterranean and 2 in southern Adriatic. Excluding the turtles that were
recovered relatively close to the nesting area in the Ionian Sea, the greatest concentrations of tag returns were observed in the
northern/central Adriatic Sea (47.6%), in the Gulf of Gabes (21.4%) and in the Aegean Sea (19%). Although the first two areas are
known foraging grounds of loggerhead turtles in the Mediterranean, the Aegean Sea has not previously been identified as important for
turtles nesting in Kyparissia Bay. The longest migrations (about 1,400 km) were directed to the Gulf of Trieste, Slovenia, and to Sinai
Peninsula, Egypt. The elapsed time (in days) between last observation at the nesting area and first recovery averages 901 days for turtles
recovered in the Ionian Sea (range: 11-5,493 days), 795 days (range: 77-2,015) in the Gulf of Gabes, 760 days (range: 101-2,641 days)
in northern/central Adriatic and 525 days (range: 33-1,154) in the Aegean Sea. It is worth to note that one turtle was observed alive in
the Ionian Sea after 5,493 days, which was about 15 years from its last observed nesting in Kyparissia Bay. Elapsed times in relation to
the distance of the recovery location can provide an idea of the average travelling speeds of migrating turtles; the maximum of these
speeds reached about 12km/day for five turtles (3 migrating to northern Adriatic, 1 to Gulf of Gabes and 1 to the Aegean Sea); this
speed concurs with similar research elsewhere. The present study highlights three important regions for loggerhead turtles in the
Mediterranean with one of them identified for first time as a preferred site for loggerheads nesting in Kyparissia Bay. Many thanks to
fishermen, coast guard and fisheries officers, concerned citizens and colleagues in several countries that provided information on
recovered turtles. Also, many thanks to the hundreds of ARCHELON volunteers and field assistants for tagging turtles in Kyparissia
Bay over the decades.
Marcel Clusaa, Carlos Carrerasb, Marta Pascualb, Stephen J. Gaughran a,c, Susanna Piovanod, Cristina Giacomad, Gloria
Fernándeze, Yaniv Levyf, Jesús Tomásg, Juan Antonio Ragag, Fulvio Maffuccih,i, Sandra Hochscheidh, Alex Aguilara, Luis
a Department of Animal Biology and IRBio, University of Barcelona, Av. Diagonal 643, 08028 Barcelona, Spain
b Department of Genetics and IRBio, University of Barcelona, Av. Diagonal 643, 08028 Barcelona, Spain
c Sackler Institute for Comparative Genomics, American Museum of Natural History, Central Park West at 79th Street, New York, NY
10024 USA
d Department of Life Sciences and Systems Biology, University of Torino, Via Accademia Albertina 13, 10123 Turin, Italy
e Fundación Aspro Natura, c/ Garcilaso de la Vega 9, E-07181, Costa d’en Blanes, Calvià , Spain
f The Israel Sea Turtle Rescue Centre, Nature Parks Authority, Mevoot Yam, Mikhmoret 40297, Israel
g Cavanilles Institute of Biodiversity and Evolutionary Biology, University of Valencia, Aptdo. 22085, 46071 Valencia, Spain
h Stazione Zoologica Anton Dohrn, Villa Comunale, 80121 Naples, Italy
i Dipartimento di Scienze, Università Roma Tre, Viale G. Marconi 446, 00146 Rome, Italy
urtles of both Atlantic and Mediterranean origin share common foraging grounds in the Mediterranean Sea. However, the detailed
structuring and distribution at sea of specific loggerhead turtle populations in the basin is still unclear. We analyse the origin of 275
stranded or bycaught juvenile loggerhead turtles (30-69 cm CCL) from six distinct foraging grounds within the Mediterranean Sea
through a Bayesian mixed-stock analysis with longer fragments of mtDNA. We aimed to describe the distribution of juveniles of Atlantic
origin within the Mediterranean Sea, unveil the use of Mediterranean foraging grounds by juveniles from the Mediterranean populations
and understand the mechanisms of such distributions. 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 Sea, with a high prevalence in the Algerian basin and lower numbers elsewhere. In regards to the
turtles from Mediterranean populations, 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, whilst
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 could be directly related to the surface circulation patterns observed, revealing that the
contribution of different nesting beaches to any particular juvenile foraging ground strongly depends on the pattern of surface currents
connecting these beaches with the foraging ground used. These results have deep implications for the assessment of bycatch impacts on
the populations using Mediterranean foraging grounds.
Yakup Kaska
Bektaş Sönmez
Onur Türkecan
Çisem Sezgin
© International Sea Turtle Society
This book can be cited as
Kaska, Y., Sonmez, B., Turkecan, O., Sezgin, C. (2015). Book of abstracts of 35th Annual Symposium on Sea
Turtle Biology and Conservation. MACART press, 250pp. Turkey.
Press in April 2015 ISBN 978-9944-0847-9-6
MacArt Grafik Basım Yayın Sırakapılar Mah. 1521 Sk. No:23/1 DENİZLİ
TEL: (258) 265 96 24
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Cover Design:MACART
Press/ Volume: Asude Ofset Matb.Rekl.Oto.Mak.San.Tic.Ltd.Şti./ Antalya
Contact Information: Prof. Dr. Yakup KASKA
Pamukkale University
Faculty of Arts and Sciences
Department of Biology
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