Turtle Aggregations Research Articles

Origin and Structure of a Large Aggregation of Suwannee Cooters (Pseudemys concinna suwanniensis) in a Florida Spring

Abstract Animals aggregate to reduce predation risk, facilitate mating, and access resources with patchy distributions. During a long-term study of turtle populations in the Santa Fe River (SFR) ecosystem in northern Florida, we observed a large aggregation of turtles at Gilchrist Blue Springs Park (GBSP) in August–October 2013 and again in March–May 2014. On 8 September 2013, we hand-captured 496 turtles of 5 species in GBSP. The Suwannee cooter (Pseudemys concinna suwanniensis) was the most abundant species in the sample, with 477 individuals representing all demographic groups. Density of this species was 530 turtles/ha and biomass was 2242 kg/ha. We hypothesize that hydrological changes in the SFR basin contributed to the temporary turtle aggregations at GBSP. The 113-km SFR originates as a tannin-stained blackwater stream, but receives input of clear water from ≥ 45 artesian springs in its lower 37 km. Heavy rainfall in the upper SFR basin from Tropical Storm Debby in June 2012 resulted in a large in...

A preliminary investigation into the early embryo death syndrome (EEDS) at the world's largest green turtle rookery.

Raine Island hosts the largest nesting aggregation of green turtles in the world, but nest emergence success and hence recruitment of hatchlings off the beach appear to have significantly declined since the 1990s. Nests destroyed by subsequent nesting turtles, and nest failure due to flooding account for most of the nest failure, but many nests still have poor hatch success even when undisturbed and flood-free. In undisturbed, flood-free nests that experience high mortality, embryos typically die at a very early stage of development, a phenomenon we term early embryo death syndrome (EEDS). Previous research indicates that EEDS is correlated with the number of females nesting at Raine Island during a nesting season. Here, we monitor nest temperature and oxygen (PO2) and carbon dioxide (PCO2) partial pressures during the first week after nest construction to discover if they are associated with EEDS. Our investigation found that the proportion of early embryo death was greatest in two nests that experienced the highest nest temperature, lowest PO2 and highest PCO2 during the first week of incubation suggesting that these variables either by themselves or in combination may be the underlying cause of EEDS. These two nests were located adjacent to maturing nests, so the high temperature and more extreme PO2s and PCO2s are most likely to be caused by the combined metabolism of embryos in the mature nests. Although this conclusion is based on just two nests and needs to be substantiated in future studies, it would appear that the laying of new nests in the close location to mature nests could be a significant cause of hatch failure at high density nesting sea turtle rookeries around the world.

Regional Conservation Implications of Green Turtle (Chelonia mydas) Genetic Stock Composition in China

Abstract Sea turtles are globally endangered and face anthropogenic threats, such as direct harvest, bycatch, and habitat degradation. Genetic studies help identify connectivity between nesting and foraging grounds for conservation and management. However, information on genetic stock composition of green turtles (Chelonia mydas) in the South China Region (including Hong Kong, Guangdong Province, and Taiwan) is severely limited. In this study, mixed stock analysis based on the 760-bp mitochondrial DNA (mtDNA) control region of green turtles (n = 110) revealed that the primary source rookeries in the Pacific contributing to foraging green turtle aggregations in the South China Region were Peninsular Malaysia, Yap in the Federated States of Micronesia, Aru of Indonesia, Sulu Sea, northeastern Borneo, Republic of Marshall Islands, Wan-an of Taiwan, and the central Ryukyu and Yaeyama of Japan. This study is the first to investigate and report the source nesting populations of a relatively large number of fora...

Ecology, health and genetic characterization of the southernmost green turtle (Chelonia mydas) aggregation in the Eastern Pacific: implications for local conservation strategies

Bahia Salado, located in northern Chile (27°41’S, 70°59’W), is the southernmost foraging ground for the endangered green turtle (Chelonia mydas) in the Eastern Pacific Ocean (EPO). To date, almost no information exists on its current status, nor on its connectivity with nesting rookeries in the EPO. This study aims to inform on the genetic characterization, health and ecology of Bahia Salado’s green turtle aggregation in order to provide baseline information for local conservation strategies. We describe population structure and residency times using mark-recapture method. We also examine health parameters (body condition index, blood profile and blood copper-Cu and lead-Pb concentrations) and regional connectivity through genetic analyses. Our results indicate that this aggregation is composed exclusively of juveniles, with residency times varying between five to sixteen months. Turtles exhibited a very good body condition; however they showed the highest blood concentrations of Cu and Pb described for C. mydas and for almost all sea turtle species. Some biochemistry parameters (albumin, calcium, phosphorus, AST, triglycerides and creatinine) are also the highest ever reported for this species in the region. Analysis of the 770 bp (base pairs) control region of the mitochondrial DNA revealed four haplotypes, suggesting a strong genetic connectivity to the Galapagos rookery. Our study indicates that Bahia Salado’s aggregation represents a developmental foraging ground, where juvenile green turtles thrive. Although Bahia Salado’s ecosystem seems to be a very suitable habitat for the species, the high levels of Cu and Pb, together with elevated AST, demand further research on the negative impacts of heavy metals on this aggregation. Our results highlight the importance to protect this bay from anthropological activities, evaluate pollution sources and other local threats to this particular coastal ecosystem. We recommend year-round monitoring of the green turtle aggregation and other components of this ecosystem, incorporating participation of local seaweed collectors and the fishing community.

Survival on the rocks: high bycatch in lobster gillnet fisheries threatens hawksbill turtles on rocky reefs along the Eastern Pacific coast of Central America

Small-scale coastal fisheries can cause detrimental impacts to non-target megafauna through bycatch. This can be particularly true when high-use areas for such species overlap with fishing grounds, as is the case with hawksbill turtle (Eretmochelys imbricata) aggregations at lobster gillnet fishing sites in El Salvador and Nicaragua. We quantified hawksbill bycatch by partnering with local fishers to record data for 690 gillnet sets on rocky reefs at Los Cobanos Reef Marine Protected Area (2008-2009) and Punta Amapala (2012-2014) in El Salvador, and La Salvia (2012-2014) in Nicaragua. Based on 31 observed hawksbill captures, the mean bycatch-per-unit-effort (0.0022; individuals per set = 0.0450) and mortality (0.74) are among the highest reported for the species across fishing gear types and oceanic regions worldwide, and we conservatively estimate that at least 227 juvenile hawksbill captures occurred in lobster gillnet fishing fleets at our sites during the study. Estimated mortality for the 227 hawksbills -which could approach the 74% observed mortality of total captures- from interactions with lobster gillnet fisheries at these sites during the study period may constitute the greatest single source of human-induced in-water mortality for juvenile, sub-adult, and adult hawksbills in the eastern Pacific, and is of grave concern to the population. Based on our findings, we discuss neritic habitat use by hawksbills during their ‘lost years’ and offer recommendations for bycatch reduction strategies, including community-based efforts to enhance sustainable self-governance via the establishment of locally crafted conservationist norms and marine protected areas at important developmental habitat.

Demography of Marine Turtles in the Nearshore Environments of the Northern Mariana Islands

In the western Pacific, green ( Chelonia mydas ) and hawksbill ( Eretmochelys imbricata ) sea turtles are listed as Endangered under the U.S. Endangered Species Act (ESA). Population data are limited for both species throughout the entire region and particularly in the Philippine Sea. This study characterizes size class distribution, growth rates, habitat use, behavior, diet, and site fidelity of foraging aggregations of green and hawksbill turtles in nearshore habitats of Saipan, Tinian, and Rota in the Commonwealth of the Northern Mariana Islands (CNMI). Between August 2006 and February 2014, we captured 642 turtles (493 green and 36 hawksbill turtles). Straight carapace length (SCL) ranged from 32.5 to 91.6 cm, with juveniles composing the majority of captures (mean SCL = 50.7 cm). Four of the green turtles were adults (SCL ≥ 81 cm), with SCLs of 84.2 to 91.6 cm. All 36 hawksbill turtles were juveniles (SCL Amansia sp., Gelidiella sp., Hypnea sp., and Ceramium sp. Green turtle growth rates ranged from 0.3 to 7.8 cm yr-1. Estimated mean residency time was 17 yr. This is the first study within the CNMI to report on morphometric data and diet composition of marine turtles. These results provide an assessment of green and hawksbill turtle population demographics and habitat use in the CNMI.

<b>Genetic diversity of the Green Turtle (Testudines: Cheloniidae: <I>Chelonia mydas</I> (Linnaeus, 1758)) population nesting at Kosgoda Rookery, Sri Lanka</b>

We determined the genetic diversity of the Green Turtle Chelonia mydas (Linneaus, 1758) nesting at Kosgoda rookery, the second largest sea turtle aggregation on the southwestern coast of Sri Lanka. Skin tissue samples were collected from 68 nesting females and genetic diversity was estimated using six microsatellite loci. High genetic diversity was observed within the population as all loci analyzed were highly polymorphic with a total of 149 alleles observed. The mean number of alleles per locus was 24.7 and the mean observed and expected heterozygosity across all loci were 0.75 and 0.93, respectively. It appears that five out of six loci were not in Hardy-Weinberg equilibrium, while micro-checker analysis suggested that the Kosgoda Green Turtle population was possibly in equilibrium. The viability of a population is unlikely to be reduced if high genetic diversity is maintained within it. Although the Green Turtle population nesting at Kosgoda is small compared to other nesting rookeries in the world, the high genetic diversity observed suggests that the population may not be undergoing a bottleneck.

A New Approach to Mixed Stock Analysis that Informs on the Management and Conservation of Hawksbill in the Wider Caribbean: the Case of the Legal Fishery in Jardines del Rey, Cuba

Researchers have used mixed stock analysis (MSA) to infer the relevance of rookeries in sea turtle aggregations for conservation/management purposes. However, their approaches and assumptions are not always homogeneous or realistic. We assayed new MSAs using the annual haplotype frequencies of aggregations and rookeries of Eretmochelys imbricata in the Wider Caribbean (WC), and the population size was selected according to the sampler year most relevant on the maturity of the aggregation. The MSA results obtained using this approach were compared with MSAs executed with grouped haplotype frequency data as has been the most common practice in the literature. The relationship of Jardines del Rey (JR) legal fishing aggregation (Cuba) to other aggregations and rookeries in the region was analyzed with data collected in 2004 to 2006 and during the 1990s. The JR non-adult fishing ground presented high genetic diversity and Mexican rookery was identified as the primary contributor using haplotypes at the 384 bp length and each MSA approach that was used, congruent with the demographic growth reported for this rookery. Using haplotypes at the 740 bp length, the primary contributor to non-adult turtles at JR differed according to the MSA approach used, alternating between Mona Island and the Mexican rookery. Jardines del Rey is a route usually taken by non-adult hawksbills of diverse origin, reflecting the need to strengthen the sampling and conservation efforts on the WC rookeries with rare or orphan haplotypes, and to warn about the impact of the fishery occurring in similar areas. Likewise, adult turtles from JR were highly diverse and from multiple origins, with this area serving as a migratory corridor for first breeders (females) to many WC breeding grounds. Caution should be employed in any MSA approach due to the influence effect of sequence length, selection of the rookery size and haplotype frequencies, as well as other assumptions that may affect the estimated contributions.

Coastal leatherback turtles reveal conservation hotspot.

Previous studies have shown that the world’s largest reptile – the leatherback turtle Dermochelys coriacea – conducts flexible foraging migrations that can cover thousands of kilometres between nesting sites and distant foraging areas. The vast distances that may be travelled by migrating leatherback turtles have greatly complicated conservation efforts for this species worldwide. However, we demonstrate, using a combination of satellite telemetry and stable isotope analysis, that approximately half of the nesting leatherbacks from an important rookery in South Africa do not migrate to distant foraging areas, but rather, forage in the coastal waters of the nearby Mozambique Channel. Moreover, this coastal cohort appears to remain resident year-round in shallow waters (<50 m depth) in a relatively fixed area. Stable isotope analyses further indicate that the Mozambique Channel also hosts large numbers of loggerhead turtles Caretta caretta. The rare presence of a resident coastal aggregation of leatherback turtles not only presents a unique opportunity for conservation, but alongside the presence of loggerhead turtles and other endangered marine megafauna in the Mozambique Channel, highlights the importance of this area as a marine biodiversity hotspot.

Using minimally invasive techniques to determine green sea turtle Chelonia mydas life-history parameters

Determining the life history and population parameters of sea turtles typically involves the live capture of animals. Photo-identification (photo-ID) of free-ranging individuals is a cost-effective alternative to conventional tagging for mark-recapture studies that also minimises the risk of injury or stress to the animals. Paired laser-photogrammetry (photogrammetry) is a minimally invasive technique to size animals and has been proven effective in a range of different taxa. Photo-ID and photogrammetry were combined as minimally invasive techniques to determine life-history parameters of free-ranging green sea turtles Chelonia mydas at a site in Oslob, Cebu, Philippines. The pattern-recognition software I3S Pattern was used to validate results and confirm visual matching. A total of 38 individuals were identified at the site through photo-ID. Facial scutes remained unchanged for a min. of 3.6years. Photogrammetry was employed to measure straight carapace lengths (SCLs) of a sample of 17 individuals, with a mean straight carapace length of 52.5±SD 1.1cm. Modified maximum likelihood methods were used to model mean residency of 873d at the site, with c. 12 individuals present at any one time. Based on photogrammetry measurements, individuals at the site were found to be of immature age class. This, along with the extended residency times, indicates that the site could be an important developmental habitat. Photo-ID is a valid minimally invasive technique for identifying individual C. mydas for mark-recapture analyses. The use of paired laser photogrammetry for categorising the life-history stage of an aggregation of sea turtles is demonstrated for the first time. Identification of such developmental habitats through the employment of these minimally invasive techniques is useful for conservation of the species.

The Black Sea Turtle (Chelonia mydas agassizii) at Lobos de Tierra Island, Northern Peru: High Densities in Small Areas

Abstract. Preliminary findings regarding black turtle (Chelonia mydas agassizii) occurrence in Lobos de Tierra Island, Northern Peru showed that 95% and 5% of turtles were juveniles and sub-adults, respectively, with an overall mean curved carapace length of 57.5 ± 7 cm (26.0–74.4 cm, n = 199). A total mean density of 180.4 turtles/km2 was found with highest densities found in bays and inlets located in the southeast. Inshore densities in shallow waters (< 1.5 m) were almost one order of magnitude greater than offshore at ∼ 1.5 km. In addition, based on structured qualitative interviews with fishermen, sea turtle capture and consumption still exists in the island, though occasional and sporadic. Jellyfish (Chrysaora plocamia) and green algae (Ulva sp.) consumption plays an important role in black turtle aggregations in the island, where densities are quite high compared to other feeding grounds elsewhere. We conclude that Lobos de Tierra constitutes an important Peruvian feeding ground, with high black tu...

Demography and foraging ecology of Chelonia mydas on tropical shallow reefs in Bahia, Brazil

Long-term tagging studies, particularly those that target life stages away from nesting beaches can provide important insights in key life history traits, which are essential for the effective management of endangered species. The coast of Bahia hosts important green turtle foraging areas, but information on demography, spatial use and foraging ecology in this region is lacking. Here, we (1) examined the size-class structure of green turtles in Bahia, (2) compared the size distribution from Bahia to other foraging aggregations in Brazil, and (3) studied the somatic growth dynamics. Additionally, we investigated the (4) diet, (5) habitat use and (6) activity patterns of green turtles along shallow reefs in Bahia. From 2009 to 2013, 322 green turtles were captured and 44 were recaptured between 7 and 1218 days after initial tagging. Curved carapace length varied from 32.9 to 122.5 cm. Mean annual growth rate was 3.03 ± 1.18 cm year−1. The diet of the turtles was mainly composed of red algae of the family Gelidiaceae, Gelidiellaceae and Cystocloniaceae. There was a positive relationship between the abundance of red algae and the number of turtle sightings, with a significant increase in foraging activity during late afternoon. This study highlights the importance of this area as a mixed foraging aggregation of juvenile and adult green turtles, and reveals that foraging grounds for this species in Brazil exhibit southern immature-dominated assemblages and northern mixed aggregations. Areas with high aggregation of green turtles comprising individuals from different life stages must be targeted for conservation management.

Fish spawning aggregations: where well‐placed management actions can yield big benefits for fisheries and conservation

AbstractMarine ecosystem management has traditionally been divided between fisheries management and biodiversity conservation approaches, and the merging of these disparate agendas has proven difficult. Here, we offer a pathway that can unite fishers, scientists, resource managers and conservationists towards a single vision for some areas of the ocean where small investments in management can offer disproportionately large benefits to fisheries and biodiversity conservation. Specifically, we provide a series of evidenced‐based arguments that support an urgent need to recognize fish spawning aggregations (FSAs) as a focal point for fisheries management and conservation on a global scale, with a particular emphasis placed on the protection of multispecies FSA sites. We illustrate that these sites serve as productivity hotspots – small areas of the ocean that are dictated by the interactions between physical forces and geomorphology, attract multiple species to reproduce in large numbers and support food web dynamics, ecosystem health and robust fisheries. FSAs are comparable in vulnerability, importance and magnificence to breeding aggregations of seabirds, sea turtles and whales yet they receive insufficient attention and are declining worldwide. Numerous case‐studies confirm that protected aggregations do recover to benefit fisheries through increases in fish biomass, catch rates and larval recruitment at fished sites. The small size and spatio‐temporal predictability of FSAs allow monitoring, assessment and enforcement to be scaled down while benefits of protection scale up to entire populations. Fishers intuitively understand the linkages between protecting FSAs and healthy fisheries and thus tend to support their protection.

Body size distribution demonstrates flexible habitat shift of green turtle (Chelonia mydas)

Green turtles (Chelonia mydas), listed as Endangered on the IUCN redlist, have a broad migration area and undergo a habitat shift from the pelagic (hatchling) to neritic (growth) zones. We studied habitat utilisation of the coastal feeding grounds around Okinawajima Island, Japan, in 103 green turtles. The western and eastern turtle aggregations off Okinawa had homogeneous genetic compositions, but different body size distributions. The western coastal feeding ground supported larger individuals than the eastern coastal feeding ground. Thus, green turtles appear to prefer different feeding grounds during their growth, and have a flexible habitat shift including a secondary habitat shift from east to west around Okinawajima Island after they are recruited to the coastal habitats. This study suggests maintaining coastal habitat diversity is important for green turtle conservation.

Juvenile green turtles on the northern edge of their range: mtDNA evidence of long-distance westward dispersals in the northern Pacific Ocean

Understanding the dispersal pathway and connectivity of an endangered species plays an essential role in the development of strategies for its effective conservation and management. By using mtDNA control region sequences, we identified the genetic composition and estimated the origin of the northernmost feeding aggregation of green turtles Chelonia mydas around the Sanriku coast of Japan. Significant differences in haplotype frequencies between Sanriku and southern Japanese feeding aggregations, a significant correlation between genetic distance and geographical distance in Japanese feeding aggregations, and estimated contribution to the Sanriku, mainly from the Japanese rookery of Ogasawara, indicate compositional changes from the south to the north along the Japanese Archipelago and suggest that the northern feeding aggregations were occupied by turtles born mainly in Japanese rookeries. However, haplotypes specific or similar to Hawaiian and eastern Pacific rookeries were detected, and substantial contributions from Hawaii or the eastern Pacific to the Sanriku feeding aggregation were estimated. Combined with the observation of specimens with phenotypic features of the subspecies ‘black turtle’ nesting in the eastern Pacific, the results indicate the long-distance dispersal of hatchlings born in Hawaii or the eastern Pacific to Japanese coastal waters, possibly through the North Equatorial Current. Although the level of contribution may be small, this study genetically supports the occurrence of the westward long-distance dispersal of green turtles in the Pacific.

Water mass characteristics and solar illumination influence leatherback turtle dive patterns at high latitudes

Eastern Canada hosts one of the largest seasonal aggregations of leatherback turtles (Dermochelys coriacea) in the Atlantic Ocean, and is considered critical foraging habitat. Explaining distributional variation of leatherbacks in this three‐dimensional habitat is relevant to the recovery strategy for this endangered species as human activities are a leading cause of mortality. We identify high‐resolution spatial and temporal patterns in leatherback movements, and associated environmental variables shaping leatherback habitat use in Atlantic Canadian foraging waters. Data loggers were deployed on three female leatherbacks off Halifax, Nova Scotia, and were recovered during subsequent nesting in South and Central America. Time (0.5 Hz), depth (±1 m), water temperature (±0.1°C), and location data were recorded and analyzed for the period when the turtles were resident in their Canadian foraging domain. We demonstrate that leatherback dives are primarily restricted to the main thermocline, suggesting a food‐related water mass association. We also identified low‐ and high‐frequency periodicities in turtle depth‐at‐time, reflecting a diel pattern triggered by nautical twilight and dive periods of 8–10 minutes. We further demonstrate that dive frequency is a function of seasonal change in daylight. Our findings illustrate that solar illumination influences leatherback diving in north temperate waters, consistent with turtles using visual cues for foraging.

Sea turtle population structure and connections between oceanic and neritic foraging areas in the Atlantic revealed through trace elements

Assessing population structure and connectivity of species that have cryptic life stages, such as sea turtles, is a challenge in conservation biology. The early oceanic stage of sea turtles, also known as the 'lost years', is poorly known. Green turtle Chelonia mydas hatchlings emerge from their nests, enter the sea, and inhabit oceanic (open ocean) habitats where they are rarely seen until they recruit to coastal (neritic) foraging grounds several years later. Therefore, the location of and population structure in oceanic foraging grounds, as well as the connections between oceanic and neritic foraging grounds, are difficult to determine. Given that long-term tracking devices are not available for sea turtle hatchlings, the use of other markers, such as trace elements and stable isotopes, is necessary to study the oceanic stages of sea turtles. We analyzed the elemental composition and ratios of stable isotopes of carbon and nitrogen of scute tissue that was deposited when turtles were in the oceanic habitat to characterize 6 oceanic foraging areas used by green turtles in the Atlantic Ocean. We determined that there is significant structuring among oceanic green turtle aggregations and multiple links between oceanic and neritic foraging areas. We discuss the conservation implications of structured oceanic aggregations with multiple links, as well as the use of trace elements (particularly titanium, chromium, zirconium and barium) in the characterization of oceanic regions.

Greener pastures? High‐density feeding aggregations of green turtles precipitate species shifts in seagrass meadows

Summary Historical declines of marine megaherbivores have led to a view of seagrass communities structured largely by abiotic disturbance and plant competition. There is, however, growing recognition of the significance of top‐down control through herbivory, on seagrass ecosystem processes, raising the question of how meadows functioned under historically high populations of megaherbivores. We assess the impacts of such intense herbivory on seagrass meadow composition in the Lakshadweep islands (India), where high‐density feeding aggregations of green turtles have persisted for over a decade. We use a series of complementary approaches: (i) natural herbivory exclosures (ii) published data on seagrass composition before and after turtles established (at one atoll: Agatti) and (iii) present species composition along a turtle herbivory gradient over multiple atolls. Long‐term natural exclosures in Agatti indicated that sustained turtle grazing caused clear shifts in species dominance from the long‐lived, higher‐successional Thalassia hemprichii to the relatively short‐lived, pioneering species Cymodocea rotundata (dominant in grazed areas). T. hemprichii was the dominant species c. 20 years ago but is now restricted to areas within exclosures in Agatti, and to the least grazed meadows (&lt;5%) in other atolls. We conducted field experiments to identify possible mechanisms by which herbivory mediated direct or apparent competitive interactions between seagrass species. To verify if grazing reduced growth rates of T. hemprichii in comparison with C. rotundata, we conducted clipping experiments in 1m2 plots, simulating turtle herbivory on equal shoot proportions of both species. After 4 months, T. hemprichii shoot density showed major declines in clipped vs. control plots, but C. rotundata shoot density remained relatively unaffected. To test whether selective grazing on T. hemprichii facilitated C. rotundata, we established paired seagrass preference experiments. Turtles had clear preferences for T. hemprichii (64%), but also grazed on C. rotundata. Synthesis. Taken together, our results show that high‐impact turtle herbivory changes seagrass composition, precipitating dominance shifts in grazed meadows by mediating direct and apparent competition. Given the crucial role of megaherbivores in seagrass meadow functioning, our results suggest that past meadows may have had natural functional limits to megaherbivore densities that they could sustainably support.

Composition of green turtle feeding aggregations along the Japanese archipelago: implications for changes in composition with current flow

In order to develop effective conservation strategies for endangered migratory species, the link between feeding and breeding grounds needs to be clarified. In this study, the genetic compositions of consecutive Japanese feeding aggregations of green turtles (Chelonia mydas) along the Kuroshio Current were examined by mixed-stock analyses of mitochondrial DNA control-region sequences. The results indicated that the southern feeding aggregation around Yaeyama (24.3°N, 124.0°E) was sourced from various Pacific rookeries in the Yaeyama, Ogasawara, Western Pacific, and Indian Oceans and Southeast Asia. Among northern feeding aggregations, the Ginoza (26.5°N, 128.0°E) aggregation was also sourced from the Western Pacific Ocean, but the Nomaike (31.4°N, 130.1°E), Muroto (33.2°N, 134.2°E), and Kanto (35.6°N, 140.5°E) aggregations were contributed mostly by the closer Ogasawara rookeries. The reduced contribution from tropical Pacific rookeries to northern feeding aggregations and the significant correlation between genetic differentiation and geographical distance matrices of feeding aggregations indicated that most hatchlings from these regions transported by the Kuroshio Current settle in upstream feeding grounds along the Japanese archipelago, implying that current flow influences the composition of feeding aggregations. Differences in the composition of relatively close neritic feeding aggregations have important conservation implications, for which both regional and multinational conservation strategies are needed.

High survivorship of an annually decreasing aggregation of hawksbill turtles, Eretmochelys imbricata, found foraging in the northern Great Barrier Reef

An 8-year study of the foraging abundance of an Eretmochelys imbricata aggregation, found on 13 reefs (Howick Group) within the northern section of the Great Barrier Reef Marine Park was undertaken. A CormackJollySeber method within program MARK was used to: (1) compare survival and recapture probabilities among age and sex classes of turtles; and (2) estimate survival and recapture rates for male and female adults and sub-adults from 665 capturemarkrecapture profiles of E. imbricata. Mean annual population density estimates were consistently greater for adult female E. imbricata (n=333.7; SD=135.6; R=221-581) than for adult males (n=32.4; SD=33.4; R=8-98), with both adult males and females displaying high survivorship rates (71.1%; 92.2%, respectively). This was also apparent in immature age-classes, with male and female turtles showing similarly high survivorship likelihoods (78.0%; 93.0%, respectively). Both sexes exhibited a similar overall trend with a peak population density being displayed in the first two years of the study, followed by a general decline in the female stock and stable male population. These are the only reliable long-term abundance time-series data for a population that includes all age-classes of E. imbricata in the western Pacific and provide good baseline data for the detection of possible climate change induced trends.