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Changes in marine ecosystems from human stressors, and concerns over how species will respond to these changes have emphasized the importance of understanding and monitoring crucial demographic parameters for population models. Long-lived, migratory, marine vertebrates such as sea turtles are particularly vulnerable to changes. Life-history parameters like growth-in-body size can be largely influenced by environmental processes which can impact population growth. We analyzed a 40-year (1981-2021) capture-mark-recapture dataset from the protected UNESCO World Heritage Site, Aldabra Atoll, Seychelles, to estimate key population parameters, including body growth, for immature green turtles (Chelonia mydas) and hawksbill turtles (Eretmochelys imbricata). Curved carapace length (CCL) range was 34.3-110.9 cm (mean ± SD: 51.0 ± 11.4 cm, n = 1191) for green turtles and 28.7-89.4 cm (47.7 ± 14.4 cm, n = 538) for hawksbill turtles. Recapture events, with an 11-month minimum period, revealed a mean annual growth rate of 3.2 ± 1.5 cm year.sup.-1 for green turtles (n = 75) and 2.8 ± 1.4 cm year.sup.-1 for hawksbill turtles (n = 110). Hawksbill turtles exhibited a non-monotonic growth rate while no significant growth-size relationship was detected for green turtles. Green turtle mean annual growth per 10-cm size class was highest in the larger size classes (50â69.9 cm). Hawksbill turtle growth rate was highest in the larger size classes (50â69.9 cm) then declined in the largest size class (70â79.9 cm). Green turtles and hawksbill turtles may spend > 8 and 18 years, respectively, using Aldabra, Seychelles, as a foraging ground., Author(s): Cheryl L. Sanchez [sup.1] [sup.2] , Nancy Bunbury [sup.2] [sup.3] , Jeanne A. Mortimer [sup.2] [sup.4] , Luke A'Bear [sup.2] , Michael Betts [sup.2] , Rainer von Brandis [sup.2] [...]

Understanding natural movement patterns and ecological roles of marine megafauna is a research priority best studied in areas with minimal human impact. The spatial distribution patterns specifically for immature turtles at foraging grounds have been highlighted as a research gap for effective management and conservation strategies for sea turtle populations. Capture–mark–recapture (CMR) records (n = 2287) of 1672 immature green (Chelonia mydas) (n = 1158) and hawksbill turtles (Eretmochelys imbricata) (n = 514) from a long-term (1981–2021) in-water CMR program at Aldabra Atoll, Seychelles, were analyzed for 10 sites (0.35–25 km apart). Site fidelity was not correlated with either season or turtle size. Green turtles had lower site fidelity than hawksbill turtles. Green turtles showed avoidance (i.e., opposite of fidelity) of three sites, while hawksbill turtles displayed high fidelity to two sites. Sites displaying non-random behavior (avoidance and/or fidelity) did not share the same benthic habitat types. Results indicate that fidelity can be detected at a fine scale with CMR, but that further exploration into the habitat characteristics of the sites and the ecological roles of both species at the atoll is needed. [ABSTRACT FROM AUTHOR]

The conservation and management of endangered species, including sea turtles, require consistent long-term monitoring of productivity (e.g., number of hatchlings emerged per nest, per female, per nesting site, per population). In sea turtle species, some of the relevant data are obtained by estimating the number of hatched eggs from fragments found in the nest after hatching. Yet, no formal assessment of the associated error has been published. Here we provide an estimation of the error associated with the most widespread method used to determine sea turtle productivity (count of shell fragments > 50% of the egg size) using a large dataset (n = 8539) of actual and estimated clutch sizes of four sea turtle species (Caretta caretta, Chelonia mydas, Dermochelys coriacea, Eretmochelys imbricata). The data are analyzed through linear mixed models with several explanatory variables. Results show that the error can be large in certain cases and, when the associated error rate is not adequately considered, may represent a serious problem in studies on reproductive parameters such as clutch size. Some significant explanatory variables suggest that some sources of error are linked to species-specific biological traits (e.g., clutch size, egg size, nest depth), and others imply human error. Other biotic and abiotic factors may also be involved. We recommend that-whenever possible-errors be assessed and adequately reported by studies that estimate clutch size, hatching and emergence success, or hatchling production., Author(s): Simona A. Ceriani [sup.1] , Beth Brost [sup.1] , Anne B. Meylan [sup.1] [sup.2] , Peter A. Meylan [sup.2] [sup.3] , Paolo Casale [sup.4] Author Affiliations: (1) grid.427218.a, 0000 [...]

Bycatch is one of the key threats to juvenile marine turtles in the Mediterranean Sea. As fishing methods are regional or habitat specific, the susceptibility of marine turtles may differ according to inter- and intra-population variations in foraging ecology. An understanding of these variations is necessary to assess bycatch susceptibility and to implement region-specific management. To determine if foraging ecology differs with region, sex, and size of juvenile loggerhead turtles (Caretta caretta), stable isotope analysis of carbon and nitrogen was performed on 171 juveniles from a range of foraging regions across the central and eastern Mediterranean Sea. Isotope ratios differed with geographical region, likely due to baseline variations in [delta].sup.13C and [delta].sup.15N values. The absence of sex-specific differences suggests that within an area, all comparably sized animals likely exploit similar foraging strategies, and therefore, their susceptibility to fisheries threats will likely be similar. The isotope ratios of juveniles occupying the North East Adriatic and North Levantine basin increased with size, potentially due to increased consumption of more prey items at higher trophic levels from a more neritic source. Isotope ratios of juveniles with access to both neritic and oceanic habitats did not differ with size which is consistent with them consuming prey items from both habitats interchangeably. With foraging habitats exploited differently among size classes in a population, the susceptibility to fisheries interactions will likely differ with size; therefore, region-specific management approaches will be needed., Author(s): Julia C. Haywood [sup.1] [sup.2], Paolo Casale [sup.3], Daniela Freggi [sup.4], Wayne J. Fuller [sup.5], Brendan J. Godley [sup.1] [sup.6], Bojan Lazar [sup.7] [sup.8], Dimitris Margaritoulis [sup.9], ALan F. [...]

Range of occurrence and abundance is a fundamental information that describes an animal population and is particularly important for species of conservation concern such as sea turtles. Although sea turtles lay clutches on land, which helps identifying breeding aggregations, the current knowledge on the distribution of these animals is far from being complete. Traditional ground surveys and more recent aerial surveys bear limitations due to logistic constraints, cost and safety concerns. We tested a novel approach based on high-resolution satellite imagery on a 12-km tract along the Atlantic coast of Florida (USA) by comparing counts from a satellite image with counts from traditional ground surveys. Daily track counts were underestimated in zones with higher human presence, probably due to tracks deleted or confounded by human activity, and overestimated in zones with lower human presence, probably due to persistence of old tracks. Results show that satellite surveys can provide the order of magnitude of nesting level in relatively undeveloped or low-frequented coastal tracts, which represent the main objective of any preliminary survey on sea turtle occurrence. Satellite imagery represents a new complementary tool available to conservationists for filling gaps about sea turtle occurrence, especially in remote or unsafe areas., Author(s): Paolo Casale [sup.1] , Simona A. Ceriani [sup.2] [sup.3] Author Affiliations: (Aff1) 0000 0004 1757 3729, grid.5395.a, Department of Biology, University of Pisa, , Via A. Volta 6, 56126, [...]

Migration is one of several marine vertebrate traits increasingly affected by human encroachment. The Adriatic Sea is an important foraging and wintering site for loggerhead turtles (Caretta caretta), and one of the Mediterranean regions where they are most heavily impacted, particularly by fisheries bycatch. Conservation measures concern foraging and wintering areas and nesting grounds, and must, therefore, be informed by the natal origin of individuals in these mixed aggregates. Genetic diversity was investigated among 488 loggerheads found stranded or incidentally captured in fishing gear across the Adriatic and the origin of individuals was assessed through mixed-stock analysis based on comparison of 755 bp of mitochondrial DNA control region sequence. In addition, we highlight the importance of the Gulf of Manfredonia (Apulia, Italy), and of the northeastern Adriatic-a previously genetically undescribed foraging ground. No significant genetic divergence was recorded among sampling areas, between turtles sampled in cold and warm months or between adults and juveniles. The distribution of turtles across the Adriatic Sea appeared not to depend on individual origin. Rookeries in western Greece and Crete provided the most important contributions to the Adriatic mixed stock. In particular, the Greek populations were the most abundant locally in the Gulf of Manfredonia, so they are likely to experience an even greater impact than previously thought because of the severe fishery bycatch levels in this area. This study also provides an example of how substantial increases in sample sizes permit a relatively comprehensive testing of genetic structure across groupings in foraging aggregations., Author(s): Livia Tolve [sup.1] , Paolo Casale [sup.2] , Angela Formia [sup.1] [sup.3] , Luisa Garofalo [sup.4] , Bojan Lazar [sup.5] [sup.6] , Chiara Natali [sup.1] , Andrea Novelletto [sup.7] [...]

Ten adult male loggerhead sea turtles, captured by trawlers or dip nets, were satellite-tracked from a neritic foraging ground in the Mediterranean in order to investigate adult spatio-temporal distribution and breeding migration. Five individuals migrated to potential breeding sites in Libya and one to Greece. The results complement previous studies and show that: (1) the Tunisian shelf may be more important for turtles from Libyan rookeries than previously thought; (2) male tracks corroborate a conservation hotspot previously identified for juveniles; (3) the north African coast represents a preferred migratory corridor, unless open sea routes are more direct; (4) adult males may exhibit high fidelity to relatively small areas, without evident seasonal differences; (5) adults home ranges were smaller and more neritic than juveniles frequenting the same area; (6) males may frequent multiple courtship areas; (7) the average remigration interval of males frequenting this region is longer than 1 year., Introduction The Mediterranean is a geo-morphologically unique basin, with both extensive neritic and oceanic habitats within short distances. It is considered as a hotspot for marine biodiversity, with about 17,000 [...]

Knowledge about migratory routes and highly frequented areas is a priority for sea turtle conservation, but the movement patterns of juveniles frequenting the Adriatic have not been investigated yet, although juveniles represent the bulk of populations. We tracked by satellite six juvenile and one adult female loggerhead from the north Adriatic. The results indicated that loggerhead juveniles (1) can either show a residential behaviour remaining in the Adriatic throughout the year or perform seasonal migrations to other areas, (2) can remain even in the coldest, northernmost area during winter, (3) can frequent relatively small foraging areas, (4) mostly frequent the eastern part of the Adriatic, and (5) follow preferred migratory routes along the western and eastern Adriatic coasts. The movements of the adult turtle also revealed (6) a behavioural polymorphism in Mediterranean adults, which included a lack of area fidelity and connection between distant neritic foraging grounds., Introduction During their lives, loggerhead sea turtles (Caretta caretta) can frequent disparate areas, feeding on epipelagic or benthic prey in oceanic and neritic zones (Bjorndal 1997; Nichols et al. 2000; [...]