Mediterranean Loggerhead Turtles Research Articles

Quantifying Abundance and Mapping Distribution of Loggerhead Turtles in the Mediterranean Sea Using Aerial Surveys: Implications for Conservation

In the Mediterranean, incidental captures in fishing gear contribute to the high mortality of loggerhead turtles (Caretta caretta). Understanding the effects of bycatch is complex and requires robust knowledge of baseline population parameters such as abundance and density, as well as an understanding of animals’ distribution in relation to commercial fishing efforts. Based on data collected during multi-species line transect aerial surveys conducted between 2009 and 2017, we present density and abundance estimates, corrected for availability bias, for a large sector of the central Mediterranean, discuss temporal and spatial patterns and provide Potential Biological Removal (PBR) values for the monitored areas. Sightings data were also used to evaluate the spatial and temporal usage areas. Strong latitudinal and longitudinal gradients in density, abundance and area usage emerged from the analysis, with turtles occurring in higher numbers in the deeper pelagic waters of the Tunisian Plateau, the Ionian Sea and the Gulf of Taranto, irrespective of the season. PBR values derived from this study are likely unsustainable. This paper investigates the implications of commercial fisheries for Mediterranean loggerhead turtles across an area rarely included in sea turtle monitoring and has the potential to be relevant towards informed management and conservation of this species and highlights the necessity of international collaborative efforts in the region.

The simultaneous stable isotope analysis of skin and blood gives insights on habitats shifts in Mediterranean loggerhead turtles (Caretta caretta, Linneus 1758)

Marine turtles are key indicator species of ecosystem function and environmental health, however, many of their life-history features remain cryptic. Particularly, the understanding of their year-round feeding habits is critical to establish the effect of contaminants exposure through the marine food web and their adverse health consequences. Here, 24 Mediterranean loggerhead turtles (Caretta caretta) with problems related to plastic ingestion were wild-caught alive in the Tyrrhenian Sea (Central Mediterranean), their bloods and epidermis were sampled, and their carbon and nitrogen isotope ratios analyzed. Generally, δ13C values did not correlate between tissues, while δ15N values showed a linear relationship, suggesting more variability in feeding habitats than in trophic levels among turtles. For all animals, the calculated stable isotope niche was wider for skin than for blood, which support a temporal difference in feeding locations. Blood probably indicated the consumption of recent pelagic food, and skin of older more neritic prey. Bayesian mixing models were implemented for turtles sampled in Sicilian waters and results suggested that, generally, prey at low trophic levels were preferred to those at higher trophic positions. Our results support the utility of sampling blood and epidermis from alive and wild animals to investigate simultaneously newer and older ecological features of sea turtles. Further studies should aim on investigating animals in both good health and with detectable disease issues, to understand how much different threats and healthy status can influence Mediterranean loggerhead turtles’ feeding ecology.

Phthalate metabolites in loggerhead marine turtles (Caretta caretta) from the Mediterranean Sea (East Spain region)

The exposure of marine reptiles to phthalates has received considerable attention due to the ubiquitous occurrence of these contaminants in the marine environment. The occurrence of phthalate metabolites is established in human populations and marine mammals, but data is scarce for marine reptiles. In this study, concentrations of 18 phthalate metabolites were determined in liver samples from 79 loggerhead marine turtle (Caretta caretta) samples collected between 2016 and 2021 in the limits of the Valencian Community (East Spain). For this purpose, the phthalate metabolites were purified from the livers by solid phase extraction and were quantified by UPLC-MS/MS. Fifteen phthalate metabolites were detected in the samples. Monoethyl phthalate (mEP), monomethyl phthalate (mMP), mono-n-butyl phthalate (mBP), phthalic acid (PA) and mono-n-hexyl phthalate (mHxP) were the most abundant metabolites, accounting for detection rates >85%. The highest median concentrations were found for PA (24.2 ng/g dry weight, d.w.) and mHxP (20.3 ng/g d.w.) followed by mMP (12.0 ng/g d.w.), mEP (5.76 ng/g d.w.) and mBP (4.26 ng/g d.w.). The sum of the medians of these five phthalate metabolites (Σ5PhMet) indicated that concentrations were higher for turtles during year 2020, while a negative association was found between [Σ5PhMet] and the turtle size. To our knowledge, this is the first study on the biomonitoring of 18 phthalate metabolites in loggerhead marine turtles, and results show that western Mediterranean loggerhead turtles are usually exposed to these contaminants.

Environmental changes in the Mediterranean Sea could facilitate the western expansion of loggerhead turtles

Climate change may affect life on Earth in multiple ways. Whereas some populations may encounter detrimental conditions that cause extirpations, those occupying cooler thermal limits of a range may benefit by expanding. For sea turtles, egg maturation in the female oviduct and nest incubation are temperature-dependent and vulnerable to climate change. Mediterranean loggerhead turtles Caretta caretta nest in the eastern basin although sporadic nesting occurs on the western side. To assess the likelihood of a climate-related expansion, we compared historical air and sea surface (SST) temperatures between locations near established eastern nesting areas and western areas where sporadic nesting is increasing (Palinuro, Italy) or just started (Balearic Islands, Spain). Our results suggest that summer air and water temperatures in western sites were suitable for nesting over the last 40-50 yr, at least in July-August, having (1) SSTs above suboptimal threshold temperature (22°C) and (2) similar air temperatures to those of Greece, but among the lowest in the Mediterranean. There was a decreasing east-to-west gradient in SST. However, SSTs were similar around beaches of Zakynthos (Greece), Palinuro and Ibiza (Balearic Islands), where SST was above 22°C for at least 60 d, potentially allowing turtles to lay multiple clutches. A warming trend was detected in air temperature and SST since the 1970s-1980s. Although conditions in the western Mediterranean currently seem suitable for nesting, lower air temperatures in May-June and higher precipitation in September could shrink the nesting window. If warming continues, conditions in the western basin could progressively become more favorable for nesting.

Levels of non-dioxin-like PCBs (NDL-PCBs) in liver of loggerhead turtles (Caretta caretta) from the Tyrrhenian Sea (Southern Italy)

The levels of six non-dioxin-like polychlorinated biphenyls (PCBs 28, 52, 101, 138, 153, and 180) were determined in the liver of 84 loggerhead turtles (Caretta caretta) stranded along the coasts of the Tyrrhenian Sea in Campania Region (Southern Italy), from 2017 to 2021. The average value of the sum (∑6PCBIND) was 28.0 ± 52.2 ng/g (w.w.). The hexachlorobiphenyls PCB 153 and PCB 138 and the heptachlorobiphenyl PCB 180 were the main contributors to the ∑6PCBIND. A weak positive correlation was found between CCL and highly chlorinated PCBs, with adult females having lower PCB concentrations than juvenile females and adult males.This study provides more comprehensive information on the levels of NDL-PCB in Mediterranean loggerhead turtles and sets the basis for assessing anthropogenic impacts on this species.

Phthalate esters (PAEs) concentration pattern reflects dietary habitats (δ13C) in blood of Mediterranean loggerhead turtles (Caretta caretta)

Phthalic acid esters (PAEs) are classified as endocrine disruptors, but it remains unclear if they can enter the marine food-web and result in severe health effects for organisms. Loggerhead turtles (Caretta caretta) can be chronically exposed to PAEs by ingesting plastic debris, but no information is available about PAEs levels in blood, and how these concentrations are related to diet during different life stages. This paper investigated, for the first time, six PAEs in blood of 18 wild-caught Mediterranean loggerhead turtles throughout solid-phase extraction coupled with gas chromatography-ion trap/mass spectrometry. Stable isotope analyses of carbon and nitrogen were also performed to assess the resource use pattern of loggerhead turtles. DEHP (12–63 ng mL-1) and DBP (6–57 ng mL-1) were the most frequently represented PAEs, followed by DiBP, DMP, DEP and DOP. The total PAEs concentration was highest in three turtles (124–260 ng mL-1) whereas three other turtles had concentrations below the detection limit. PAEs were clustered in three groups according to concentration in all samples: DEHP in the first group, DBP, DEP, and DiBP in the second group, and DOP and DMP in the third group. The total phthalates concentration did not differ between large-sized (96.3 ± 86.0 ng mL-1) and small-sized (67.1 ± 34.2 ng mL-1) turtles (p < 0.001). However, DMP and DEP were found only in large-sized turtles and DiBP and DBP had higher concentrations in large-sized turtles. On the other hand, DEHP and DOP were found in both small- and large-sized turtles with similar concentrations, i.e. ~ 21.0/32.0 ng mL-1 and ~ 7.1/9.9 ng mL-1, respectively. Winsored robust models indicated that δ13C is a good predictor for DBP and DiBP concentrations (significant Akaike Information criterion weight, AICwt). Our results indicate that blood is a good matrix to evaluate acute exposure to PAEs in marine turtles. Moreover, this approach is here suggested as a useful tool to explain the internal dose of PAEs in term of dietary habits (δ13C), suggesting that all marine species at high trophic levels may be particularly exposed to PAEs, despite their different dietary habitats and levels of exposure.

The Mediterranean Mussel (Mytilus galloprovincialis) as Intermediate Host for the Anisakid Sulcascaris sulcata (Nematoda), a Pathogen Parasite of the Mediterranean Loggerhead Turtle (Caretta caretta).

Sulcascaris sulcata (Anisakidae), a pathogenic nematode of sea turtles, may cause ulcerous gastritis with different degrees of severity. Previous studies demonstrated a high prevalence of infection in the Mediterranean loggerhead turtle (Caretta caretta), although no data on the potential intermediate hosts of this nematode has been published thus far from the Mediterranean basin. Here, using molecular analyses, we demonstrated that the cross sections of nematode larvae observed histologically in Mediterranean mussels (Mytilus galloprovincialis) collected from a farm along the Tyrrhenian coast of southern Italy belong to S. sulcata. The BLAST analysis of sequences at the ITS2 region of rDNA and mtDNA cox2 gene loci here obtained from samples of two Mediterranean mussels containing nematode larvae showed 100% homology with those at the same gene loci from the adults of S. sulcata collected from the Mediterranean Sea and deposited in GenBank. To our knowledge, this study is the first to present data on a potential intermediate host of S. sulcata in the Mediterranean basin and to report a nematode parasite from the Mediterranean mussel.

Bycatch of Loggerhead Turtle (Caretta caretta) in the Italian Adriatic Midwater Pair Trawl Fishery

Despite the fact that Mediterranean loggerhead turtles are listed as ‘Least Concern’ by the IUCN, they are among the most threatened long-lived marine species worldwide, because of fishery-related incidental captures. The northern central Adriatic Sea is one of the most overfished basins of the Mediterranean Sea and it supports a very valuable marine biodiversity, including sea turtles. This study assesses the spatial and seasonal impact of the northern central Adriatic pelagic/mid-water pair trawl fishery on loggerhead turtle (Caretta caretta) by examining incidental catches recorded between 2006 and 2018 and environmental variables. The model predicted seasonal variation of loggerhead distribution. According to previous studies, data analysis indicates that most bycatch events of loggerhead turtle occurred in the northern Adriatic Sea. The present data confirm that the northern Adriatic may be an important foraging area for loggerhead turtle. They also highlight the urgent need for a better understanding of the interactions between sea turtles and fisheries to develop and apply suitable, ad hoc management measures in critical habitats.

Assessing resource use patterns of Mediterranean loggerhead sea turtles Caretta caretta (Linnaeus, 1758) through stable isotope analysis

Stable isotope analysis is a useful tool for studying the ecology of marine consumers, as carbon (δ13C) and nitrogen (δ15N) isotope ratios may reflect individuals’ patterns of diet and habitat use. Knowledge of foraging strategies has significant implications for the conservation of endangered loggerhead turtles Caretta caretta (Linnaeus, 1758). In this study, δ13C and δ15N isotope data were used to assess resource use patterns of the Mediterranean loggerhead turtles (Aeolian Archipelago, Southern Italy). δ13C and δ15N values from carapace scutes of 54 loggerheads of different curved carapace length (CCL) and health status were compared with those of eight potential prey items (benthic, pelagic and fishery discards). MixSIAR results suggested that pelagic prey (from goose barnacles to planktivorous fish) comprised most of loggerheads’ diet, with small variations (i.e. benthic prey or fishery discards) depending on size (δ13C and δ15N) and health (δ15N) of individuals. δ13C variations with turtles’ size might reflect changes in dietary habitats during life stages. However, the loggerhead turtles and their main source of prey (pelagic prey) had a higher variation in values of δ15N compared to δ13C. This suggested that smaller-sized turtles might preferentially feed on pelagic prey in oceanic habitats and then, as they reach a larger size, gradually enter neritic waters, including in their diet prey sources with higher δ13C and δ15N. Some turtles foraging on longline baits/debris also displayed a marked increase in δ15N. These δ15N variations might be explained by differences in diet (trophic differences) and somatic growth rates among individuals, or dietary dilution.

Living between widely separated areas: Long-term monitoring of Mediterranean loggerhead turtles sheds light on cryptic aspects of females spatial ecology

Over the last decades, satellite tracking techniques have substantially advanced our understanding of sea turtle spatial behaviour, especially for the post-nesting migrations of females. Substantial gaps remains in our knowledge of the turtle behaviour during the remaining inter-reproductive period, that spans over 2–3years. We report the results of a prolonged tracking experiment on loggerhead turtles nesting along the Ionian Calabria, the main breeding ground in Italy. Argos satellite transmitters were deployed on eight females, a sample representing a substantial fraction of the overall population (20–25 nesting females). All turtles but one were tracked for >300days (range: 313–1523days), revealing their spatial behaviour during a complete reproductive cycle and providing novel information on a number of poorly-known aspects of loggerhead spatial ecology: i) the post-nesting migratory strategy resulted in accordance with that of most adult loggerheads tracked so far, as the nine routes of six turtles were directed towards specific sites all located in the Tunisian continental shelf, a main foraging area for Mediterranean turtles; ii) the pre-breeding migratory routes were rather variable, likely deriving from different navigational strategies adopted by migrating turtles, and their temporal pattern indicates that mating occurred away from the nesting area; iii) the 10 inter-nesting movements of four turtles revealed unusual long-distance loops mostly in oceanic waters (median of maximum distance from nesting location: 145.5km); iv) while at the foraging grounds, four turtles occupied distinct areas during summer and winter, making directed movements between the two sites, seasonal core areas were separated and their size was larger in winter than in summer (median: 498km2 vs. 258km2); v) individual females displayed an high fidelity to both sites in successive years. These findings further highlight the plasticity in loggerhead spatial behaviour and the importance of the Central Mediterranean and of the Tunisian shelf for loggerhead conservation.

Distribution patterns and foraging ground productivity determine clutch size in Mediterranean loggerhead turtles

Distribution patterns and foraging ground productivity determine clutch size in Mediterranean loggerhead turtles

Fine-scale distribution of juvenile Atlantic and Mediterranean loggerhead turtles (Caretta caretta) in the Mediterranean 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.

Long-Term Tracking of Adult Loggerhead Turtles (Caretta caretta)in the Mediterranean Sea

Three adult-sized Loggerhead Turtles (Caretta caretta), captured incidentally by bottom trawlers, were tracked by satellite in the Mediterranean Sea for a substantial part of their annual cycle, including the period preceding nesting. The three turtles performed long-distance movements that were variable between individuals but shared common features such as seasonal migration. Very prolonged dives (up to over 300 min) were associated with temperature drops to below 18°C , likely an overwintering strategy. Our findings integrate recent tracking data on the postnesting migrations of Mediterranean Loggerhead Turtles, documenting the movement patterns made during the poorly known nonreproductive phase.

Satellite tracking large numbers of individuals to infer population level dispersal and core areas for the protection of an endangered species

AbstractAimTracking the dispersal patterns and habitat use of migratory species is necessary to delineate optimal areas for protection, with large sample sizes being more representative of the population. Here, we examine the dispersal patterns of a key Mediterranean loggerhead turtle (Caretta caretta) breeding population to identify priority foraging sites for protection.LocationZakynthos Island, Greece and the wider Mediterranean.MethodWe examined the dispersal patterns and foraging sites of 75 adult loggerheads (n = 38 males and 37 females) tracked from the breeding area of Zakynthos Island (Greece) from 2004 to 2011. We then combined our data with published sea turtle literature to identify key foraging sites for protection.ResultsWhile both males and females exhibited similar dispersal patterns, about 25% males remained &lt; 100 km of Zakynthos, whereas all females (except one) migrated &gt; 200 km. Integration of our data with the wider literature isolated 10 core sites in proximity to existing protected areas, which could potentially protect 64% of the Zakynthos population, while five sites support individuals from at least 10 other loggerhead breeding populations.Main conclusionsDue to the widespread availability of neritic foraging grounds across the Mediterranean, sea turtles from Zakynthos exhibit disparate dispersal patterns. However, protecting only a few objectively defined important sites can encompass a large proportion of the foraging areas used and hence have considerable conservation benefit.

Loggerhead turtles nesting in Libya: an important management unit for the Mediterranean stock

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 450:207-218 (2012) - DOI: https://doi.org/10.3354/meps09548 Loggerhead turtles nesting in Libya: an important management unit for the Mediterranean stock Almokhtar Saied1, Fulvio Maffucci2,*, Sandra Hochscheid2, Salih Dryag1, Bashir Swayeb1, Marco Borra2, Atef Ouerghi3, Gabriele Procaccini2, Flegra Bentivegna2 1Libyan Sea Turtle Program-Environment General Authority, PO Box 13793, Tripoli, Libya 2Stazione Zoologica Anton Dohrn, 80121 Naples, Italy 3UNEP-MAP-RAC/SPA, Tunis, Tunisia *Corresponding author. Email: maffucci@szn.it ABSTRACT: Libya is one of the most important loggerhead turtle Caretta caretta nesting grounds in the Mediterranean Sea, but data on its genetic diversity and demographic connection to adjacent Mediterranean nesting sites are scarce. Here we investigated mitochondrial diversity in adult females from 2 nesting locations along the Libyan coasts, Misurata and Sirte, by analysing both the commonly used 380 bp mtDNA fragment and a longer 800 bp fragment that completely encompass the shorter region. No genetic differentiation was detected between the Libyan sites using the shorter sequences (Φst = −0.005, p = 0.54, Exact p = 0.67). However, significant population structuring was found among sites in Libya and other Mediterranean nesting areas (Φst = 0.242, p < 0.01). The analysis of the longer sequence revealed more haplotypes than the shorter fragment and uncovered genetic differentiation between Misurata and Sirte (Φst = 0.13, p = 0.02, Exact p = 0.01), suggesting fine-scale homing behaviour of loggerhead nesting females along the Libyan coast. Because only a few Atlantic and Mediterranean loggerhead turtle rookeries have been genetically surveyed using the longer sequence, we used information from the short mtDNA fragment to investigate dispersal patterns of Libyan loggerhead turtles. Mixed stock analysis estimates suggested that during the oceanic developmental phase, Libyan juveniles remain preferentially in the eastern Mediterranean while after the transition to the neritic phase, they favour the south Tunisian coastal areas while avoiding the north-central Adriatic Sea. This study highlights the unique nature of the Libyan nesting population, making it an important management unit. The protection of this nesting stock is fundamental to managing the Mediterranean loggerhead turtle assemblage. KEY WORDS: Loggerhead turtle · mtDNA · Population structure · Conservation · Dispersal pattern · Homing Full text in pdf format Supplementary material PreviousNextCite this article as: Saied A, Maffucci F, Hochscheid S, Dryag S and others (2012) Loggerhead turtles nesting in Libya: an important management unit for the Mediterranean stock. Mar Ecol Prog Ser 450:207-218. https://doi.org/10.3354/meps09548 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 450. Online publication date: March 29, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

Age and growth determination by skeletochronology in loggerhead sea turtles (&lt;i&gt;Caretta caretta&lt;/i&gt;) from the Mediterranean Sea

Skeletochronology was applied to humerus bones to assess the age and growth rates of loggerhead sea turtles ( Caretta caretta ) in the Mediterranean Sea. Fifty-five dead turtles with curved carapace lengths (CCL) ranging from 24 to 86.5 cm were collected from the central Mediterranean. Sections of humeri were histologically processed to analyze annual growth marks. Two approaches were used to estimate the somatic growth in the form of a von Bertalanffy growth function. The first approach was based on calculating the total number of growth marks, which corresponds to the age of turtles at death. The second approach estimates the carapace length at old growth marks in order to provide the growth rate of each turtle. The observed individual growth rates ranged from 1.4 to 6.2 cm yr –1 , and showed both elevated inter- and intra-individual variability possibly related to the environmental variability experienced by turtles during their lifetime. Both approaches gave similar results and suggest that Mediterranean loggerhead turtles take 14.9 to 28.5 years to reach a CCL of 66.5 to 84.7 cm. This size corresponds to the average size of nesting females found in the most important Mediterranean nesting sites and can be considered the approximate size at maturity.

Genetic characterization of loggerhead turtle (Caretta caretta) individuals stranded and caught as bycatch from the North-Central Adriatic Sea

AbstractThe North Adriatic Sea is considered a critical feeding and developmental area for Mediterranean loggerhead turtles. In this study, a comparative analysis of mitochondrial DNA control region sequences was carried out on sixty-five loggerhead individuals stranded and caught as bycatch in the Adriatic Sea from 1999 to 2002. We demonstrated the existence of genetic relationships between the North-Central Adriatic (NCA) aggregate and the Central-Eastern Mediterranean rookeries. Short-range and long-range migrations towards the Adriatic Sea were hypothesized by the finding of individuals bearing haplotypes endemic to the nesting populations of Greece and Turkey. The occurrence of individuals belonging to dimensional classes from juveniles to mature adults strongly support both the feeding and developmental role of the NCA.

Do long-term changes in sea surface temperature at the breeding areas affect the breeding dates and reproduction performance of Mediterranean loggerhead turtles? Implications for climate change

Global climate change is likely to have an important influence on the phenology, behaviour and population dynamics of many species. We investigate climatic related changes in the breeding phenology of Mediterranean loggerhead marine turtles Caretta caretta over a 19 year period and the potential relationship between these changes and reproductive success and performance. We found that the studied population has experienced fluctuating sea surface temperatures (SST) with an increasing trend during the last century. With increasing spring SST there is a trend towards earlier nesting. However, there is no significant relationship between SST and nesting season, defined as the duration between the first recorded emergence and the last nest laid. Our analyses indicate that marine turtles display phenological changes, and thus maintain favorable thermal conditions at the nesting sites. Furthermore, increasing spring SST was correlated with decreasing clutch size and increasing hatching success that resulted in an apparent lack of correlation between SST and hatchling production. This apparent independence might be misleading since it only holds for a limited range of SST values. Thus, if we estimate the effect of climate change on loggerhead population growth as neutral, based on the apparent independence between SST and total number of hatchlings, we will be underestimating the population extinction risk.

Polychlorinated biphenyls and other chlorinated organic contaminants in the tissues of Mediterranean loggerhead turtle Caretta caretta

Polychlorinated biphenyls including coplanar congeners and DDT compounds were measured in different organs and tissues (liver, kidney, lung and muscle tissue) of loggerhead turtles Caretta caretta from the eastern Mediterranean Sea. The highest levels of these compounds were found in liver (PCBs: 52.32 ng/g; DDTs: 18.27 ng/g), followed by kidney (PCBs: 19.05 ng/g; DDTs: 5.70 ng/g), lung (PCBs: 12.75 ng/g; DDTs: 3.76 ng/g ) and muscle tissue (PCBs: 4.65 ng/g; DDTs: 1.45 ng/g). PCBs revealed a profile dominated by hexa-, penta- and hepta-chlorinated congeners, while among DDTs, the compound in the greatest concentration was p,p'-DDE, (liver: 85.2%, kidney: 93.6%, lung: 86.4%, muscle tissue: 93.2%). The estimated toxic equivalents (pg TEQs/g wet wt) of non- and mono-ortho PCBs were in the range of 1.54-5.86 pg TEQs/g wet wt. Non-ortho coplanar PCB 77 accounted for more than 90% of the total TEQs leaving to mono-ortho only 2.6-6.2%.

Natal origin of loggerhead turtles, Caretta caretta, in the neritic habitat off the Italian coasts, Central Mediterranean

Shallow (neritic) waters close to the Italian coasts (Central Mediterranean Sea) are frequently visited by foraging loggerhead turtles, but the nesting populations which rely on this area have not been determined. To estimate the rookery origins of this feeding cohort, mitochondrial DNA control region sequences were analysed from 106 juvenile loggerhead turtles and compared to those published for key nesting populations in the Atlantic and Mediterranean regions using a Bayesian based stock analysis program. Six distinct haplotypes were detected, of which two have previously been reported from both Mediterranean and Atlantic nesting beaches and one only from Atlantic nesting populations. The remaining three haplotypes could not be assigned to a rookery of origin. Mixed stock analysis indicated that the waters along the Southern Italian coasts are utilised primarily by Mediterranean nesting populations, with approximately 68% of the individuals provided by the genetically homogeneous Greece/South eastern Mediterranean nesting aggregate and 23% by the Turkish management unit. 7% of the loggerhead turtles were assigned to Atlantic stock. Our results suggest that only a small proportion of the Atlantic juveniles which enter the Mediterranean to forage in its pelagic waters utilise also the neritic areas along the Italian coasts. This is consistent with theory of juvenile homing, according to which oceanic stage juveniles preferentially recruit to neritic developmental habitats within their natal region, and implies that the elevated human-induced mortality occurring in this area impacts almost exclusively the smaller and demographically more vulnerable Mediterranean loggerhead turtle stock.