Immature Green Turtles Research Articles

Atlantic connectivity of a major green sea turtle Chelonia mydas foraging aggregation at the Banc d’Arguin, Mauritania

Understanding population connectivity is paramount for effective conservation. While genetic tools have elucidated sea turtle migration patterns, notable data gaps limit our understanding of ocean-wide connectivity, especially regarding east Atlantic green turtles. We characterized the genetic composition of a globally important green turtle foraging aggregation at the Banc d’Arguin, Mauritania, incorporating data from 323 individuals captured between 2018 and 2021. Using extended mitochondrial DNA D-loop (738 base pairs [bp]) and mitochondrial short tandem repeat (mtSTR; ~200 bp) markers, we assessed the genetic structure of Atlantic green turtle foraging aggregations and estimated the most likely origin of immature green turtles from the Banc d’Arguin using mixed stock analyses (MSAs). We identified 6 D-loop haplotypes, with a clear dominance of CM-A8.1 (91.8%) followed by CM-A5.1 (6.3%) and 4 rare haplotypes: CM-A1.4, CMA6.1, CM24.1 and CM36.1. We found 13 mtSTR haplotypes, with ‘7-12-4-4’ being dominant (89.0%). The genetic composition at the Banc d’Arguin differed significantly from the only foraging aggregation studied in West Africa to date—in the archipelago of Cabo Verde (located ca. 750 km from the Banc d’Arguin)—dominated by haplotype CM-A5. The MSA combining both genetic markers indicated that 87.6% of immature green turtles at the Banc d’Arguin originate from the major East Atlantic rookery at Poilão (Guinea-Bissau), but 11.6% come from more distant rookeries in South America (8.1%) and potentially Ascension Island (3.4%). We suggest that green turtle transatlantic movements may be more common than previously thought and highlight the importance of the Banc d’Arguin as a regional foraging hub for this species.

Fine-scale foraging ecology and habitat use of sympatric green and hawksbill turtles in the Western Indian ocean

Using stable isotope analysis of carbon and nitrogen of turtle tissues and putative prey items, we investigated the diet of immature green turtles and hawksbill turtles foraging in the lagoon of Aldabra Atoll, a relatively undisturbed atoll in the southern Seychelles. Aldabra offers a unique environment for understanding sea turtle ecology. Green turtles mostly consumed seagrass and brown algae while hawksbill turtles mainly consumed mangroves and invertebrates. Green turtles showed a dietary shift with size (a proxy for age). There was minimal niche overlap between species and evidence of small-scale foraging site fidelity with turtle tissue reflecting site-specific prey. This highlights the ecological importance of seagrass and mangrove habitats and suggests that turtles play a role in controlling algal biomass at Aldabra. This study is the first to closely examine the foraging ecology of these sympatric turtle species in the Western Indian Ocean, a globally important region for both species.

Daily, seasonal, and long-distance movements inferred from Fastloc-GPS telemetry of immature green turtles (Chelonia mydas) at a high-latitude, mid-ocean developmental site.

To characterize the movements and habitat use of juvenile green turtles (Chelonia mydas) in benthic developmental habitat, we deployed Fastloc-GPS-enabled satellite transmitters on 16 individuals captured as part of a multi-decade study of green turtles on the Bermuda Platform. We characterized residence areas, distinct use areas within them, and seasonal movements based on an average of 562 Fastloc-GPS positions and 284 tracking days per turtle. We estimated residence area sizes using traditional home range methods, e.g., 90% utilization distribution (UD) (mean 2.29 ±2.71 km2) and 50% UD (mean 0.54 ±0.69 km2). Total residence area size increased significantly over the 8-year study, from <1 km2 before 2013 to ≥3 km2 in 2018 (R2 = 0.51, F1,14 = 14.55, p = 0.0019), corresponding to a period of decline in seagrass habitat and suggesting increased foraging effort. We identified three types of distinct use areas within residence areas where tracked turtles typically exhibited behavioral fidelity: foraging, resting, and cool weather refugia. These distinct use areas were smaller than high-use areas from previous studies; e.g., seagrass meadow foraging areas averaged 0.05 km2. Most turtles made daily transits between foraging and resting sites; for some individuals, these involved crossing frequently used vessel navigation channels. Seasonal variation in behavior suggested that the overwintering strategy for green turtles on the Bermuda Platform involves "optional dormancy," during which turtles spent less time on seagrass meadows and made brief excursions to distinct deeper habitats. Four individuals made directed (mean path straightness = 0.93 ±0.02 SD) developmental migrations away from Bermuda toward known adult foraging range. Results of our study further knowledge of the green turtle life cycle at a high-latitude site; they demonstrate that green turtles show fidelity to distinct use areas within developmental habitats over many years and exhibit seasonal movements.

Feminization of a mixed-stock foraging aggregation of immature green turtles (Chelonia mydas), 1975–2018

Marine turtles exhibit temperature-dependent sex determination (TSD), and there is widespread concern that global warming is raising nest incubation temperatures, resulting in increasingly female-skewed sex ratios in “feminized” populations. We assessed the sex ratio of a mixed-stock aggregation of immature green turtles (Chelonia mydas) at a midocean developmental foraging ground in the Northwest Atlantic from 1975 to 2018. We used plasma testosterone concentrations, measured by radioimmunoassay (RIA) and calibrated by laparoscopy, to determine the sex of 2,724 green turtles captured 3,940 times in Bermuda (32°18′ N, 64°46′ W) waters. A logistic regression model correctly predicted the sex of 99.5% of turtles (189/190) with associated testosterone concentrations whose sex had been verified via laparoscopy. Empirical evaluation of the trend in sex ratio using four related data sets showed a significant increase (2.8–4.0% yr−1) in the sex ratio (F/M) over the course of the study. Using growth rates to predict the year of arrival of turtles in Bermuda, we estimated the sex ratio of recruiting cohorts over 4 decades. Mixed-stock analysis of mtDNA sequences of 602 turtles that recruited to Bermuda between 1970 and 2018 suggested that multiple, geographically dispersed rookeries contributed to the Bermuda aggregation making it regionally representative. Changes in rookery contributions and strong population increases at certain rookeries may partly explain the increasing trend in the sex ratio. But the steady rate of increase over decades and the increasing female percentage of arriving cohorts are consistent with impacts of global warming at source rookeries.

Growth rate and projected age at sexual maturity for immature hawksbill turtles and green turtles foraging in the remote marine protected area of Aldabra Atoll, Seychelles

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−1 for green turtles (n = 75) and 2.8 ± 1.4 cm year−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 (50‒69.9 cm). Hawksbill turtle growth rate was highest in the larger size classes (50‒69.9 cm) then declined in the largest size class (70‒79.9 cm). Green turtles and hawksbill turtles may spend > 8 and 18 years, respectively, using Aldabra, Seychelles, as a foraging ground.

Food selection and habitat use patterns of immature green turtles (Chelonia mydas) on Caribbean seagrass beds dominated by the alien species Halophila stipulacea

Marine herbivores face rapid changes in the coastal ecosystems where they forage. In the Caribbean, the recent and fast expansion of the invasive phanerogam species Halophila stipulacea is threatening native seagrass ecosystems. So far, H. stipulacea is escaping most Caribbean herbivores, certainly because of its recent introduction or lower nutritional value. We investigated the impact of H. stipulacea invasion on fine-scale foraging habitat selection and food resource selection of immature green turtles at critical foraging sites in Les Anses d′Arlet, Martinique. The analysis of seagrass distribution and nutritional content, together with turtle behaviour and resource selection, showed that H. stipulacea may be of contrasting interest to green turtles. Compositional analysis confirmed the lower nutritional value of H. stipulacea compared to the native species, but the invasive species showed higher digestibility than native ones, which calls into question the energetic advantage of consuming the native plants over the exotic plant. Thus, although green turtles mostly selected the native seagrass Thalassia testudinum in multispecies seagrass beds, some individuals fed on H. stipulacea . Accordingly, in bays entirely invaded by H. stipulacea , one possibility for resident green turtles is to increase foraging on this species, but, if so, the consequences on their growth and survival still remain to be determined. As the expansion of H. stipulacea may have been facilitated by factors such as shipping, anchor scarring and fishing activities, protection of native seagrass beds and immature green turtles from human disturbances is urgently required to ensure the long-term adaptation of green turtles to this new foraging environment. • High variability of diet composition in immature green turtles in Martinique. • Turtles preferentially selected T. testudinum in multi-species seagrass beds. • H. stipulacea may represent 0–100% of the diet whatever native plants availability. • H. stipulacea has lower nutritional value but higher digestibility than native plants. • Human activities promote H. stipulacea development to the detriment of native species.

Fibropapillomatosis Prevalence and Distribution in Immature Green Turtles (Chelonia mydas) in Martinique Island (Lesser Antilles).

Fibropapillomatosis (FP) threatens the survival of green turtle (Chelonia mydas) populations at a global scale, and human activities are regularly pointed as causes of high FP prevalence. However, the association of ecological factors with the disease's severity in complex coastal systems has not been well established and requires further studies. Based on a set of 405 individuals caught over ten years, this preliminary study provides the first insight of FP in Martinique Island, which is a critical development area for immature green turtles. Our main results are: (i) 12.8% of the individuals were affected by FP, (ii) FP has different prevalence and temporal evolution between very close sites, (iii) green turtles are more frequently affected on the upper body part such as eyes (41.4%), fore flippers (21.9%), and the neck (9.4%), and (iv) high densities of individuals are observed on restricted areas. We hypothesise that turtle's aggregation enhances horizontal transmission of the disease. FP could represent a risk for immature green turtles' survival in the French West Indies, a critical development area, which replenishes the entire Atlantic population. Continuing scientific monitoring is required to identify which factors are implicated in this panzootic disease and ensure the conservation of the green turtle at an international scale.

A half-century of demographic changes in a green turtle (Chelonia mydas) foraging aggregation during an era of seagrass decline

To understand the demographic responses of green turtles to seagrass decline, we examined a data set from study of a mixed-stock foraging aggregation of immature green turtles, Chelonia mydas, collected in Bermuda (32o18’N, − 64o46’W) over five decades. Average turtle size (SCLmin) and mass declined by 22.3% and 58.2%, respectively. Aggregation size structure shifted to smaller sizes and now consists of more small turtles and fewer large turtles. Density (turtles ha−1) increased significantly but biomass (kg ha−1) remained unchanged and low compared to C. mydas biomass observed elsewhere. Green turtles exhibited reduced site fidelity during two portions of the study period, suggesting increased foraging effort. Reduction in turtle body condition index and seagrass coverage occurred from offshore to inshore. Changes in aggregation composition and behavior were consistent with expectations given a documented decline in seagrass availability, combined with increased output from source rookeries. Apparent response to resource decline is traced back to 1976, well before seagrass loss was first documented. Green turtles and their primary food source (Thalassia testudinum) are at the northern limit of their range in Bermuda, where seagrasses would be expected to have a reduced tolerance for natural grazing pressure and increased susceptibility to synergistic stressors, especially temperature, bioturbation and phosphorus limitation. Our results suggest that synergistic stressors, and not green turtles alone, have produced the observed reduction in seagrasses on the Bermuda Platform. Given that seagrass declines have been reported worldwide, our findings may suggest how green turtles will respond elsewhere.

Fibropapilomatosis en juveniles de Tortuga Verde (Chelonia mydas) del Golfo de Venezuela

Fibropapillomatosis (FP) is affecting multiple marine turtle (MT) species worldwide. In Venezuela, the understanding about this neoplastic condition is still in early stage. Hence, this paper aims to assess the occurrence and frequency of FP in green turtles (GT) in the Gulf of Venezuela (GV). Herein, it was compiled and analyzed the reports in the database of the NGO ‘Grupo de Trabajo en Tortugas Marinas del Golfo de Venezuela’, which includes all records of stranded MT in the GV from 2000 to 2011. Between 2000 and 2006, in the GV only 2 cases of FP in MT had been reported (1.71 % of total records). Subsequently, between 2008 and 2011, encounters of FP were more frequent; resulting in a total of 7 immature GT (2.93 % of the records) documented showing large masses or skin tumors in various parts of the body. The most affected area of the MT’s body was neck and venous sinus (37.50 %), followed by the anterior flippers (18.75 %), plastron (18.75 %), posterior region (cloaca 18.75 %) and lastly, the eyes (6.25 %). All individuals presented two or more body areas with FP. Although a correlation between the presence of FP and environmental factors observed in the study area was not assessed, the turtles evaluated came from coastal waters with high levels of eutrophication, habitat degradation, and pollution. It is necessary to monitor the occurrence of this disease and the environmental factors that may negatively affect the survival of MT populations in the GV.

Fully Convolutional Neural Network: A solution to infer animal behaviours from multi-sensor data

Animal-attached accelerometers have been widely used to monitor species that are difficult to observe, alongside the use of machine learning to identify behaviours from the obtained sequences. Artificial neural networks are powerful supervised learning algorithms that are based on deep learning and have been poorly exploited in movement ecology. Recently, the availability of sophisticated algorithmic architectures via open source libraries facilitates their use. In this study, we adapt a fully convolutional neural network that was originally developed for biomedical 3D image segmentation: the V-net. We test it on a labelled dataset collected from animal-borne video recorders combined with multi-sensors (accelerometers, gyroscopes and depth recorders) deployed on free-ranging immature green turtles (Chelonia mydas). The proposed model, fitted for 1D data, is able to predict six behavioural categories for green turtles with an AUC score of 88%. It shows a high ability to detect rare behaviours with low discriminative signals such as Feeding and Scratching. With a precision down to one centisecond, the V-net circumvents the segmentation process. We also show that the gyroscope is more informative than the accelerometer in identifying sea turtle behaviours and that the V-net is not able to discriminate Feeding from the raw data of accelerometer alone. However, human expertise can help to correct it with precise and adapted pre-processing. Thus, diverted from its initial purpose and tested on sea turtle, the V-net is a very efficient method of behavioural identification that should be easily generalized to a wide range of species. It could lead to considerable progress in remote accelerometric monitoring and help to understand the ecology of the species that are difficult to observe. Furthermore, as the model is light, there is also a huge potential to implement a trained V-net in satellite-relay data tag to remotely predict the expressed behaviours almost instantly.

Foraging Habits of Green Sea Turtles (Chelonia mydas) in the Northwestern Gulf of Mexico

Knowledge of green turtle (Chelonia mydas) foraging ecology in the northwestern Gulf of Mexico (GOM) is critical as populations begin to recover from heavy harvesting in prior centuries. We present a comprehensive long-term assessment of green turtle diets from carcasses salvaged from 1987 to 2014 along the Texas coast. Digestive tract contents were examined from 420 green turtles, ranging in size from 7.3 to 86.0 cm in straight carapace length (SCLmax). Green turtles as small as 16.2 cm SCLmaxrecruit from the oceanic environment to nearshore foraging habitat in the northwestern GOM and consume macroalgae principally. A successive shift in diet and habitat to inshore seagrasses was evident by the seagrass-dominated diet of turtles larger than 30 cm SCLmax. Animal matter remained a frequently ingested diet item suggesting these immature green turtles are better classified as omnivores. The overall evidence indicates that Texas’ recovering green turtle assemblage is exhibiting foraging plasticity within seagrass meadows changing species composition and density.

Pharmacokinetics of ponazuril after administration of a single oral dose to green turtles (Chelonia mydas)

The coccidian protozoan, Caryospora cheloniae, has been associated with severe enteritis and encephalitis in immature farm-raised green turtles (Chelonia mydas) in the Cayman Islands, immature green turtles off the coast of Florida, and immature stranded sea turtles in Australia. An effective anti-coccidial drug that is both orally absorbed and well-distributed throughout the body is needed for treatment of turtles diagnosed with coccidiosis in rehabilitation facilities. Ponazuril is a triazine antiprotozoal drug that is approved in the USA for the treatment of another Apicomplexan, Sarcocystis neurona, and has also been successfully used in the therapy of other coccidian parasites. The objective of this study was to perform an oral dose-ranging pilot study (10–100 mg/kg of body weight ponazuril) in green turtles (N = 9), followed by oral administration of ponazuril at 100 mg/kg body weight (N = 8) to assess its disposition. Another goal of this study was to optimize the method of oral drug administration to green turtles. Plasma ponazuril concentrations were quantified using high performance liquid chromatography (HPLC). Standard compartmental models were fit to the data. Ponazuril was absorbed after oral administration at 100 mg/kg BW, with a maximum plasma concentration of 3.3 µg/ml. Dose-dependent pharmacokinetic parameters only weakly correlated with the dose rate, apparently due to considerable pharmacokinetic variability observed between turtles. Administration of ponazuril in gelatin capsules using a balling gun was deemed the least variable and most successful method of drug administration. Further studies are needed to evaluate the safety and efficacy of ponazuril in sea turtles with coccidiosis.

High fidelity of sea turtles to their foraging grounds revealed by satellite tracking and capture-mark-recapture: New insights for the establishment of key marine conservation areas

Movement ecology studies are essential to protect highly mobile threatened species such as the green turtle (Chelonia mydas), classified as an endangered species by the IUCN. In 2019, the South Atlantic subpopulation has been downlisted to ‘Least Concern’, but the maintenance of this status strongly relies on the pursuit of research and conservation, especially on immatures, which contribute to the demographic renewal of this subpopulation. Identifying marine areas used by immatures is therefore crucial to implement efficient measures for the conservation of sea turtles in the Caribbean. We analysed data of capture-mark-recapture of 107 (out of 299) immatures recaptured at least once in Martinique, and satellite tracked 24 immatures to investigate their site fidelity and habitat use. Our results revealed a strong fidelity to foraging grounds, with mean residence times higher than 2 years, and with a high degree of affinity for specific areas within the coastal marine vegetation strip. Home ranges (95% kernel contour) and core areas (50% kernel contour) varied from 0.17 to 235.13 km2 (mean ± SD = 30.73 ± 54.34 km2) and from 0.03 to 22.66 km2 (mean ± SD = 2.95 ± 5.06 km2), respectively. Our findings shed light on a critical developmental area for immature green turtles in the French West Indies, and should help to refine Regional Management Units and reinforce the cooperative network aiming at ensuring conservation of the species at international scale.

Marine turtle mortality in a southern Caribbean artisanal fishery: A threat for immature green turtles

The impact of artisanal fisheries on marine turtle populations is still understudied in the southern Caribbean. In the Venezuelan Guajira Peninsula, artisanal fishing of marine turtles by the indigenous Wayuú people has occurred for generations. Nevertheless, understanding the issues regarding turtle take is challenging. Surveys and semi-structured interviews were carried out at eight landing sites located in three different zones in Kazuzain village, Middle Guajira. Carapaces or plastrons were recorded to estimate take level, and measured to determine life stage. Minimum take was 167 marine turtles over 53 weeks, or 3.15 turtles/week on average (estimated 163.8/yr). Most records encountered were from green turtles (n=154; 92.2%), and the majority of these were immature (n=76; 89.4%). Key-informants reported that marine turtles were not the target catch. However, most interviewees affirmed that take of marine turtles in Kazuzain is not only for traditional purposes, but also to meet economic shortfalls. They also stated that trade of marine turtles has increased over the last ten years due to the Venezuelan economic crisis. This is the first assessment of marine turtle take in this village and fills an information gap that can aid resource managers to mitigate the impacts of take, and develop potential conservation solutions for marine turtle aggregations and the people that depend on them.

Space use and relative habitat selection for immature green turtles within a Caribbean marine protected area

BackgroundA better understanding of sea turtle spatial ecology is critical for the continued conservation of imperiled sea turtles and their habitats. For resource managers to develop the most effective conservation strategies, it is especially important to examine how turtles use and select for habitats within their developmental foraging grounds. Here, we examine the space use and relative habitat selection of immature green turtles (Chelonia mydas) using acoustic telemetry within the marine protected area, Buck Island Reef National Monument (BIRNM), St. Croix, United States Virgin Islands.ResultsSpace use by turtles was concentrated on the southern side of Buck Island, but also extended to the northeast and northwest areas of the island, as indicated by minimum convex polygons (MCPs) and 99%, 95%, and 50% kernel density estimations (KDEs). On average space use for all categories was < 3 km2 with mean KDE area overlap ranging from 41.9 to 67.7%. Cumulative monthly MCPs and their proportions to full MCPs began to stabilize 3 to 6 detection months after release, respectively. Resource selection functions (RSFs) were implemented using a generalized linear mixed effects model with turtle ID as the random effect. After model selection, the accuracy of the top model was 77.3% and showed relative habitat selection values were highest at shallow depths, for areas in close proximity to seagrass, and in reef zones for both day and night, and within lagoon zones at night. The top model was also extended to predict across BIRNM at both day and night.ConclusionMore traditional acoustic telemetry analyses in combination with RSFs provide novel insights into animal space use and relative resource selection. Here, we demonstrated immature green turtles within the BIRNM have small, specific home ranges and core use areas with temporally varying relative selection strengths across habitat types. We conclude the BIRNM marine protected area is providing sufficient protection for immature green turtles, however, habitat protection could be focused in both areas of high space use and in locations where high relative selection values were determined. Ultimately, the methodologies and results presented here may help to design strategies to expand habitat protection for immature green turtles across their greater distribution.

Exploring plastic-induced satiety in foraging green turtles

In the last decade many studies have described the ingestion of plastic in marine animals. While most studies were dedicated to understanding the pre-ingestion processes involving decision-making foraging choices based on visual and olfactory cues of animals, our knowledge in the post-ingestion consequences remains limited. Here we proposed a theoretical complementary view of post-ingestion consequences, attempting to connect plastic ingestion with plastic-induced satiety. We analyzed data of plastic ingestion and dietary information of 223 immature green turtles (Chelonia mydas) from tropical Brazilian reefs in order to understand the impacts of plastic ingestion on foraging behavior. Generalized linear mixing models and permutational analysis of variance suggested that plastic accumulations in esophagus, stomach and intestine differed in their impact on green turtle’s food intake. At the initial stages of plastic ingestion, where the plastic still in the stomach, an increase in food intake was observed. The accumulation of plastic in the gastrointestinal tract can reduce food intake likely leading to plastic-induced satiety. Our results also suggest that higher amounts of plastics in the gastrointestinal tract may led to underweight and emaciated turtles. We hope that adopting and refining our proposed framework will help to clarify the post-ingestion consequences of plastic ingestion in wildlife.

Movements, connectivity, and space use of immature green turtles within coastal habitats of the Culebra Archipelago, Puerto Rico: implications for conservation

Movements, connectivity, and space use of immature green turtles within coastal habitats of the Culebra Archipelago, Puerto Rico: implications for conservation

Using Programming Languages and Geographic Information System to Determine Spatial and Temporal Variability in a Green Turtle Foraging Population on Liuchiu Island, Taiwan.

Facial photo identification (ID) has proven to be a non-invasive method for identifying individual wild animals, and in recent years it has been effective on megafauna such as sea turtles. However, when processing hundreds of photos over a long period of time, variation in facial scale patterns makes identifying individuals complicated. This means that there is a high possibility that the individual is misidentified, which results in incorrectly determining population sizes. This study used the programming languages Python and SQL to determine green turtle foraging population size in the nearshore waters of a coral island, Liuchiu Island, from 2011 to 2017. The programs determined that the foraging population was 432 turtles, approximately 90% of which resided there one year or less and selected only one foraging site. Those that stayed for more than two years selected two foraging sites. Less than 3% stayed throughout the 7 years. The core residence area was from Beauty Cave to Vase Rock. This study found that the nearshore waters of Liuchiu Island are a temporary development/foraging site for immature green turtles. This is the first study to use Python analysis to determine a foraging sea turtle population in the field.

Mixed stock analysis of juvenile green turtles aggregating at two foraging grounds in Fiji reveals major contribution from the American Samoa Management Unit

In this study we assessed the breeding population, or Management Unit (MU), origin of green turtles (Chelonia mydas) present at Yadua Island and Makogai Island foraging grounds in Fiji, central South Pacific. Based on analysis of mitochondrial (mt) DNA sequences from 150 immature green turtles caught during surveys carried out in 2015–2016, we identified a total of 18 haplotypes, the most common being CmP22.1 (44%) which is a primary haplotype characterizing the American Samoa breeding population. Results of a Bayesian mixed-stock analysis reveals that the two foraging grounds are used by green turtles from the American Samoa MU (72%, Credible Interval (CI): 56–87%), New Caledonia MU (17%, CI: 6–26%) and French Polynesia MU (7%, CI: 0–23%). The prominence of the contribution we found from the American Samoa MU compared to that of French Polynesia, both which have historic telemetry and tagging data showing connectivity with Fijian foraging areas, may reflect the current relative abundance of these two nesting populations and draws attention to a need to update population surveys and identify any significant nesting in Fiji that may have been overlooked.

Assessing Karenia brevis red tide as a mortality factor of sea turtles in Florida, USA.

Data on Karenia brevis red tides (≥105 cells l-1) and on dead or debilitated (i.e. stranded) Kemp's ridleys Lepidochelys kempii, loggerheads Caretta caretta, green turtles Chelonia mydas, hawksbills Eretmochelys imbricata, and leatherbacks Dermochelys coriacea documented in Florida during 1986-2013 were evaluated to assess red tides as a sea turtle mortality factor. Unusually large numbers of stranded sea turtles were found coincident with red tides primarily along Florida's Gulf coast but also along a portion of Florida's Atlantic coast. These strandings were mainly adult and large immature loggerheads and Kemp's ridleys, and small immature green turtles and hawksbills. Unusually large numbers of stranded leatherbacks never coincided with red tide. For the 3 most common species, results of stranding data modeling, and of investigations that included determining brevetoxin concentrations in samples collected from stranded turtles, all indicated that red tides were associated with greater and more frequent increases in the numbers of stranded loggerheads and Kemp's ridleys than in the number of stranded green turtles. The mean annual number of stranded sea turtles attributed to K. brevis red tide was 80 (SE = 21.6, range = 2-338). Considering typical stranding probabilities, the overall mortality was probably 5-10 times greater. Red tide accounted for a substantial portion of all stranded loggerheads (7.1%) and Kemp's ridleys (17.7%), and a smaller portion of all stranded green turtles (1.6%). Even though K. brevis red tides occur naturally, the mortality they cause needs to be considered when managing these threatened and endangered species.