The Presence of the Green Turtle, Chelonia mydas, in Italian Coastal Waters During the Last Two Decades (original) (raw)
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Mediterranean sea turtles: current knowledge and priorities for conservation and research
Endangered Species Research
The available information regarding the 2 sea turtle species breeding in the Mediterranean (loggerhead turtle Caretta caretta and green turtle Chelonia mydas) is reviewed, including biometrics and morphology, identification of breeding and foraging areas, ecology and behaviour, abundance and trends, population structure and dynamics, anthropogenic threats and conservation measures. Although a large body of knowledge has been generated, research efforts have been inconsistently allocated across geographic areas, species and topics. Significant gaps still exist, ranging from the most fundamental aspects, such as the distribution of major nesting sites and the total number of clutches laid annually in the region, to more specific topics like age at maturity, survival rates and behavioural ecology, especially for certain areas (e.g. southeastern Mediterranean). These gaps are particularly marked for the green turtle. The recent positive trends of nest counts at some nesting sites may be the result of the cessation of past exploitation and decades of conservation measures on land, both in the form of national regulations and of continued active protection of clutches. Therefore, the current status should be considered as dependent on such ongoing conservation efforts. Mitigation of incidental catch in fisheries, the main anthropogenic threat at sea, is still in its infancy. From the analysis of the present status a comprehensive list of re search and conservation priorities is proposed.
e-Journal of New World Sciences Academy
A new nesting site that is not previously designated as a nesting beach was investigated for the green turtle (Chelonia mydas) nesting. The Yeniyurt Beach is bordered by BOTAŞ Port to the south and Seçil Holiday Houses to the north. The small water channel in Yeniyurt Public Beach is taken to the reference point of which can be divided as the north, 2600 m long, and the south, 1400 m long. The beach was monitored between 15 June and 15 September in 2019. A total of 182 green turtle emergences occurred, and 85 (46.7%) of them were recorded as nests. The nest density was found as 21.2 clutches yr-1. The temporal distribution of the nests was found to be 52.9%, 45.8% and 1.3% in June, July and August, respectively. Besides, the average nest depth and incubation duration was 71.9cm ±8.2 (n=70) and 52.6 days ±4.4 (n=70), respectively. A total of 7362 eggs were laid in these nests and 6274 (85.2%) of them hatched. The average clutch size and number of empty eggshells were found to be 105.2 ±30.1 (40-199) and 89.6 ±26.4 (35-154), respectively. The average number of hatchlings reaching the sea was 62.8 ±20.8 (70.1%). Yeniyurt beach can be considered as a moderate dense beach (20−99 clutches yr-1 ; ≥6.5 clutches km-1 yr-1) for green turtle nesting based on previous studies in the Mediterranean.
Data on strandings of dead loggerhead (Caretta caretta) and green (Chelonia mydas) turtles were collected from the eastern Mediterranean coast of Turkey during the nesting seasons between 2002 and 2009. A total of 276 strandings were recorded (142 C. caretta and 128 C. mydas). The curved carapace length (CCL) of C. caretta ranged from 12.6-85 cm (mean 63.50±1.06 cm). The CCL of C. mydas ranged from 20-93 cm with a mean of 40.97±1.41 cm. 2.4% and 31.7% of the loggerheads were oceanic stage small juveniles (≤30 cm CCL) and adults (≥70 cm CCL), respectively. Of the green turtles, 33.3% (≤31.5 cm CCL) and 4.6% (≥85 cm CCL) were small juveniles and adults, respectively. The source populations of these turtles could become identified with genetic mixed stock analysis.
Herpetological Journal, 2013
Correspondence: Oğuz Türkozan (turkozan@adu.edu.tr) Data on strandings of dead loggerhead (Caretta caretta) and green (Chelonia mydas) turtles were collected from the eastern Mediterranean coast of Turkey during the nesting seasons between 2002 and 2009. A total of 276 strandings were recorded (142 C. caretta and 128 C. mydas). The curved carapace length (CCL) of C. caretta ranged from 12.6–85 cm (mean 63.50±1.06 cm). The CCL of C. mydas ranged from 20–93 cm with a mean of 40.97±1.41 cm. 2.4% and 31.7% of the loggerheads were oceanic stage small juveniles (≤30 cm CCL) and adults (≥70 cm CCL), respectively. Of the green turtles, 33.3% (≤31.5 cm CCL) and 4.6% (≥85 cm CCL) were small juveniles and adults, respectively. The source populations of these turtles could become identified with genetic mixed stock analysis.
The nesting biology of green and loggerhead sea turtles (Chelonia mydas and Caretta caretta) on Akyatan, Ağyatan, Tuzla and Yumurtalık Nature Reserve beaches along the eastern Mediterranean coast of Turkey was investigated during six consecutive nesting seasons (2006–2011). A total of 2198 C. mydas and 104 C. caretta nests were recorded, with an annual mean of 366 and 17 nests, respectively. Akyatan was the main breeding site for both species. We recorded a total of 5879 C. mydas emergences, with 2171 (37%) resulting in nests (mean of 362 nests per year); the mean nesting density was 16 nests km-1. A total of 1335 (61%) C. mydas nests from Akyatan beach were excavated. We recorded 151,758 eggs, 116,309 of which (77%) hatched, producing 88,673 hatchlings which were able to reach the sea. The annual number of nests ranged from 170 (2007) to 562 (2006), with a statistically non-significant decrease throughout the study period (Spearman r=-0.20, p>0.05). The main threats were predation of eggs and hatchlings by jackals, plastic pollution and vehicle ruts that hindered the hatchlings progress to the sea.
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.