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Casale P.,University of Rome La Sapienza | Freggi D.,Sea Turtle Rescue Center Italy | Dourdeville K.M.,Wellfleet | Prescott R.,Wellfleet
Vie et Milieu | Year: 2013

Loggerhead sea turtles (Caretta caretta) frequent very distant areas during their life stages, and information about migratory routes and geographical range is key for planning their conservation. Here we report on the first direct evidence of a loggerhead turtle migrating from the eastern Mediterranean to the North American coast. A juvenile of 57.1 cm curved carapace length was tagged and released from Lampedusa Island, Italy, in 2008 and found dead on the Massachusetts coast in 2012. Its size and first location fit with the current knowledge about Atlantic loggerheads entering the Mediterranean and this finding supports the hypothesis of homing behavior as the explanation for the low genetic flow estimated between the Atlantic and Mediterranean populations. Source

Casale P.,University of Rome La Sapienza | Mazaris A.D.,Aristotle University of Thessaloniki | Freggi D.,Sea Turtle Rescue Center Italy
Endangered Species Research | Year: 2011

It is widely accepted that the age at sexual maturity of sea turtles is a critical parameter for studying population dynamics and persistence. Estimates of the age at maturity for such longlived species are derived using somatic growth models, which are still lacking for several regions of the world. In the present study, the growth rate of the loggerhead sea turtle Caretta caretta in the Mediterranean was investigated using a length-frequency analysis of a dataset collected over a 19 yr period (1990 to 2008). A total of 2255 individuals were measured in the central Mediterranean, with turtle size ranging from 16.8 to 97.5 cm curved carapace length (CCL). Monthly length-frequency histograms were constructed, and strong size modes were identified, assumed to represent individual cohorts. Growth rates were calculated by tracking the progression of the modes, by means of a modal progression analysis. Annual growth rates ranged from 0.37 to 6.5 cm yr -1. A von Bertalanffy growth function was used to estimate the time required by turtles to grow within the observed size range. The results indicate that turtles would take from 23.5 to 29.3 yr to reach 80 cm CCL, considered an approximation of the size at maturity. This estimation integrates and confirms a previous estimate obtained using a different method. It provides information vital to understanding the population dynamics of loggerhead turtles in the Mediterranean, and highlights the value of datasets of longterm series when investigating critical demographic parameters. © Inter-Research 2011. Source

Casale P.,University of Rome La Sapienza | Casale P.,University of Exeter | Freggi D.,Sea Turtle Rescue Center Italy | Maffucci F.,Stazione Zoologica Anton Dohrn | And 2 more authors.
Scientia Marina | Year: 2014

Sea turtles show temperature-dependent sex determination (TSD) and information on sex ratios at different life stages is necessary both for population dynamics models for conservation and to shed light on the possible adaptive value of TSD. Adults represent the less abundant class of sea turtle populations and adult sex ratios at foraging grounds are very difficult to obtain. We first analysed biometric data of 460 juvenile and adult loggerhead sea turtles ranging from 60 to 97.5 cm curved carapace length (CCL), in which a clear bimodal distribution of tail length (the main secondary sexual character of adult males) was observed in the size class >75 cm CCL. We then sexed 142 adult turtles in this size class collected from the Tunisian shelf and from the southeastern Tyrrhenian Sea, observing a proportion of females of 51.5% (95% CI: 41.2-61.8%; n=97) and 40.0% (95% CI: 25.7-55.7%; n=45) respectively. Our results complement previous studies and support their findings of similar and more balanced sex ratios in adult and juvenile loggerhead turtles in the Mediterranean, in contrast with highly female-biased sex ratios of hatchlings. © 2014 CSIC. Source

Garofalo L.,University of Rome Tor Vergata | Garofalo L.,Centro Of Referenza Nazionale Per La Medicina Forense Veterinaria | Mastrogiacomo A.,University of Rome La Sapienza | Casale P.,University of Rome La Sapienza | And 12 more authors.
Aquatic Conservation: Marine and Freshwater Ecosystems | Year: 2013

In migratory species female- and male-mediated gene flow are important for defining relevant Management Units, and for evaluating connectivity between these and their respective foraging grounds. The stock composition at five Mediterranean foraging areas was investigated by analysing variation in the mitochondrial D-loop and six microsatellite loci in a sample of 268 loggerhead turtles (Caretta caretta) stranded or accidentally caught by fisheries. This involved a comprehensive Mixed Stock Analysis which considers also recent data from major rookeries in Libya and Turkey, and the generation of a standardized nomenclature of allele sizes at the microsatellite loci. The results indicate: that the north Adriatic, the Tunisian continental shelf, the waters around Malta and the Italian Ionian Sea represent important areas for the conservation of rookeries in Greece, Libya and Turkey, respectively; that waters off the Italian peninsula and the islands of Lampedusa and Malta are mainly inhabited by individuals of Mediterranean origin, with a major contribution from the nearest and largest colonies, while Atlantic turtles are restricted to the western areas; that specific migratory routes exist from rookeries to foraging grounds; a poor bi-parental genetic structuring, which suggests a high male-mediated gene flow in the Mediterranean; mixing of small turtles in waters distant from natal rookeries, and recovery of structuring for large-sized individuals; and that uncommon mtDNA haplotypes are more powerful markers than microsatellite alleles in assessing an individual's origin, owing to their higher geographic specificity. © 2013 John Wiley & Sons, Ltd. Source

Casale P.,University of Rome La Sapienza | Casale P.,University of Exeter | Freggi D.,Sea Turtle Rescue Center Italy | Furii G.,Centro Recupero Tartarughe Marine Legambiente | And 7 more authors.
Aquatic Conservation: Marine and Freshwater Ecosystems | Year: 2015

One of the major gaps in the knowledge of sea turtle population dynamics is survival probability, in particular of juveniles, which represent the bulk of the population and whose survival has the greatest effect on population growth. One of the major global threats to sea turtles is incidental bycatch, although not all animals die in the process. This is particularly acute for the loggerhead sea turtle (Caretta caretta). Here fisheries-dependent monitoring is used to seek insights into patterns of survival at multiple Mediterranean foraging areas: north and south Adriatic, north Ionian, and the Tunisian shelf. Annual survival probability was estimated using the catch curve method. Size data of 2191 loggerhead turtles ranging from 19 to 92cm curved carapace length were converted to age according to eight age-size curves available from the Mediterranean Sea. The mean annual survival probabilities for the four areas were heterogeneous and ranged between 0.710 and 0.862. Results suggest that the survival probabilities for Mediterranean loggerheads, especially in some areas, are lower than would be expected from a healthy population. This is of particular concern for the Greek rookeries, which appear most affected by anthropogenic mortality occurring in the study areas. This supports the implementation in those areas of measures mitigating the main threats, notably bycatch. © 2015 John Wiley & Sons, Ltd. Source

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