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Although the hawksbill turtle (Eretmochelys imbricata) nesting colony in Hawaiʻi may constitute one of the smallest hawksbill nesting populations in the world, it is also the largest in the U.S. Pacific Islands and the Central North Pacific Ocean. The isolated nature of the Hawaiian Archipelago has raised interest in the genetic characterization of the population, yet research remains lacking. In this study we use mitochondrial DNA (mtDNA) to provide the first genetic characterization of nesting (n = 108) and foraging (n = 29) hawksbills in the Hawaiian Islands. We combine our data with sequences previously published from the West and East Pacific to evaluate the genetic distinctiveness of the nesting assemblage in Hawaiʻi, and to gain insights into the origin of hawksbills found at foraging grounds around the archipelago. We found strong differentiation (FST > 0.238, P-value

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.

Assessments of fisheries by‐catch on marine megafauna are important for developing effective management strategies. For sea turtles, impacts may be evident in nesting population trends, but generally only after a lag, as turtles are slow to mature. We examined 850 loggerhead turtle (Caretta caretta) by‐catch samples collected over 14 years throughout the western North Atlantic to identify source nesting populations. We identified proportions of turtles from 19 distinct management units (MUs), using mitochondrial DNA and mixed stock analysis, considering population size. We found a significant split in the distribution of small versus large loggerheads to the north and south of Cape Hatteras, North Carolina (latitude 35°N). North of Cape Hatteras, large turtles came from south‐east Florida (SEFL; 44% ± 15%) and the northern United States (33% ± 16%) MUs, while south of Cape Hatteras, the major contributors were Central East Florida (52% ± 20%) and south‐east Florida (SEFL; 41% ± 20%). Small turtles in the north came from Central East Florida (64% ± 14%), and in the south, south‐east Florida had the highest representation (56% ± 25%). There was little contribution from Mediterranean and Cape Verde populations, indicating low risk from western North Atlantic by‐catch to MUs in the Mediterranean. Understanding where threats may impact source populations is important, particularly for larger size turtles, as these individuals have the highest reproductive value. These findings allow more informed threat assessments to be conducted for loggerhead turtles considering spatial and demographic structure.

Pacific leatherback turtles (Dermochelys coriacea) are critically endangered, and declines have been documented at multiple nesting sites throughout the Pacific. The western Pacific leatherback forages in temperate and tropical waters of the Indo-Pacific region, and about 38–57% of summer-nesting females from the largest remaining nesting population in Papua Barat (Indonesia) migrate to distant foraging grounds off the U.S. West Coast, including neritic waters off central California. In this study, we examined the trend in leatherback abundance off central California from 28 years of aerial survey data from coast-wide and adaptive fine-scale surveys. We used a Bayesian hierarchical analysis framework, including a process model of leatherback population density and an observation model relating leatherback observations to distance sampling methods. We also used time-depth data from biologgers deployed on 21 foraging leatherback turtles in the study area to account for detection biases associated with diving animals. Our results indicate that leatherback abundance has declined at an annual rate of −5.6% (95% credible interval −9.8% to −1.5%), without any marked changes in ocean conditions or prey availability. These results are similar to the nesting population trends of −5.9% and −6.1% per year estimated at Indonesian index beaches, which comprise 75% of western Pacific nesting activity. Combined, the declining trends underscore the need for coordinated international conservation efforts and long-term population monitoring to avoid extirpation of western Pacific leatherback turtles.

Understanding population structure and migration patterns is critical for conservation of marine species that undertake seasonal migrations, often spanning entire oceans, between breeding grounds and distant feeding areas. To examine the stock origin of the green turtle foraging aggregation in San Diego Bay, California, USA (32.6°N, 117.1°W) and evaluate current life history hypotheses, 770 bp sequences of the mitochondrial DNA control region from 121 green turtles captured in San Diego Bay were compared to potential source (nesting) populations across the Pacific. Mixed stock analysis indicated that the San Diego Bay foraging population originates from eastern Pacific nesting sites, primarily the Revillagigedo Archipelago and the coast of Michoacan, Mexico. To further understand migratory pathways and breeding destinations, three mature female turtles were satellite tracked from the San Diego Bay foraging ground (FG), including one turtle tracked for 364 days that nested at Socorro Island in Revillagigedo and returned to San Diego Bay (total distance approx. 3200 km), one of the first continuous satellite tracks of a sea turtle from a FG to its nesting site and back. Tracks from another turtle indicated possible nesting at Tres Marias Islands, approximately 100 km off the Mexican mainland coast. All three turtles have subsequently been recaptured in San Diego Bay, indicating a high degree of FG philopatry. These results rule out previous speculation that Hawaiian green turtles were also using San Diego Bay, provide insights into the distribution of the Revillagigedo Islands and Michoacan breeding populations and draw attention to the Tres Marias Islands as a potential source of green turtles in the temperate North Pacific.

Summary Climate change affects species and ecosystems around the globe [1]. The impacts of rising temperature are particularly pertinent in species with temperature-dependent sex determination (TSD), where the sex of an individual is determined by incubation temperature during embryonic development [2]. In sea turtles, the proportion of female hatchlings increases with the incubation temperature. With average global temperature predicted to increase 2.6°C by 2100 [3], many sea turtle populations are in danger of high egg mortality and female-only offspring production. Unfortunately, determining the sex ratios of hatchlings at nesting beaches carries both logistical and ethical complications. However, sex ratio data obtained at foraging grounds provides information on the amalgamation of immature and adult turtles hatched from different nesting beaches over many years. Here, for the first time, we use genetic markers and a mixed-stock analysis (MSA), combined with sex determination through laparoscopy and endocrinology, to link male and female green turtles foraging in the Great Barrier Reef (GBR) to the nesting beach from which they hatched. Our results show a moderate female sex bias (65%–69% female) in turtles originating from the cooler southern GBR nesting beaches, while turtles originating from warmer northern GBR nesting beaches were extremely female-biased (99.1% of juvenile, 99.8% of subadult, and 86.8% of adult-sized turtles). Combining our results with temperature data show that the northern GBR green turtle rookeries have been producing primarily females for more than two decades and that the complete feminization of this population is possible in the near future.

Climate, behavior, ecology, and oceanography shape patterns of biodiversity in marine faunas in the absence of obvious geographic barriers. Marine turtles are an example of highly migratory creatures with deep evolutionary lineages and complex life histories that span both terrestrial and marine environments. Previous studies have focused on the deep isolation of evolutionary lineages (>3 mya) through vicariance; however, little attention has been given to the pathways of colonization of the eastern Pacific and the processes that have shaped diversity within the most recent evolutionary time. We sequenced 770 bp of the mtDNA control region to examine the stock structure and phylogeography of 545 green turtles from eight different rookeries in the central and eastern Pacific. We found significant differentiation between the geographically separated nesting populations and identified five distinct stocks (F ST = 0.08-0.44, P < 0.005). Central and eastern Pacific Chelonia mydas form a monophyletic group containing 3 subclades, with Hawaii more closely related to the eastern Pacific than western Pacific populations. The split between sampled central/eastern and western Pacific haplotypes was estimated at around 0.34 mya, suggesting that the Pacific region west of Hawaii has been a more formidable barrier to gene flow in C. mydas than the East Pacific Barrier. Our results suggest that the eastern Pacific was colonized from the western Pacific via the Central North Pacific and that the Revillagigedos Islands provided a stepping-stone for radiation of green turtles from the Hawaiian Archipelago to the eastern Pacific. Our results fit with a broader paradigm that has been described for marine biodiversity, where oceanic islands, such as Hawaii and Revillagigedo, rather than being peripheral evolutionary "graveyards", serve as sources and recipients of diversity and provide a mechanism for further radiation.

This study presents a comprehensive genetic analysis of stock structure for leatherback turtles (Dermochelys coriacea), combining 17 microsatellite loci and 763 bp of the mtDNA control region. Recently discovered eastern Atlantic nesting populations of this critically endangered species were absent in a previous survey that found little ocean-wide mtDNA variation. We added rookeries in West Africa and Brazil and generated longer sequences for previously analyzed samples. A total of 1,417 individuals were sampled from nine nesting sites in the Atlantic and SW Indian Ocean. We detected additional mtDNA variation with the longer sequences, identifying ten polymorphic sites that resolved a total of ten haplotypes, including three new variants of haplotypes previously described by shorter sequences. Population differentiation was substantial between all but two adjacent rookery pairs, and F ST values ranged from 0.034 to 0.676 and 0.004 to 0.205 for mtDNA and microsatellite data respectively, suggesting that male-mediated gene flow is not as widespread as previously assumed. We detected weak (F ST = 0.008 and 0.006) but significant differentiation with microsatellites between the two population pairs that were indistinguishable with mtDNA data. POWSIM analysis showed that our mtDNA marker had very low statistical power to detect weak structure (F ST

Fisheries that operate at large spatial scales and with high intensity have the potential to impact highly migratory species, and it is important to characterize threats to specific breeding populations of these species. We used many‐to‐many mixed‐stock analysis (MSA) (n = 408) and microsatellite assignment testing (n = 397) to determine source populations for leatherback turtles (Dermochelys coriacea) caught as bycatch in the U.S. pelagic longline fishery from 2002 to 2012 in the western North Atlantic. Within the United States, we had bycatch samples from the majority of statistical fishing areas: Gulf of Mexico (GOM), Northeast Distant (NED), Caribbean (CAR), Florida East Coast (FEC), Mid Atlantic Bight (MAB), Northeast Coastal (NEC), South Atlantic Bight (SAB) and Sargasso (SAR). We determined the proportions of turtles from each of nine nesting stocks in the Atlantic in each of the sampled areas. These nesting stocks included Brazil, Costa Rica, Florida, Trinidad, French Guiana, St. Croix, Ghana, Gabon, and South Africa. The MSA revealed that the NED had a lower relative proportion of turtles from Costa Rica than other areas and that the GOM had the highest relative proportion of turtles from Costa Rica. No turtles were assigned to the African rookeries, lending further evidence that turtles from that region forage elsewhere and therefore may not be affected by western North Atlantic fisheries. This work contributes to the ongoing assessment of threats to leatherback turtles in the Regional Management Unit (RMU) of the western North Atlantic, and draws attention to the disproportionate number of turtles from Costa Rica being caught in the Gulf of Mexico; Costa Rica is one of the only populations in the northern Atlantic that is not experiencing significant increases in nest numbers. This approach should be useful in determining population‐specific threats to other highly migratory protected species that may depend on segregated foraging areas either within or among species.

The southeastern USA hosts the largest nesting concentration of loggerhead turtles Caretta caretta in the Atlantic. Regionally significant nesting also occurs along the Caribbean coast of Mexico, in Cuba, and in the Bahamas. Previous studies of North Atlantic loggerhead turtle rookeries based on a 380 bp fragment of the mitochondrial control region supported recognition of 8 demographically independent nesting populations (management units) in the Northwest Atlantic in addition to Cape Verde in the eastern Atlantic. Recent analysis of expanded mitochon- drial control region sequences revealed additional genetic diversity and increased population structure between western and eastern Atlantic loggerhead turtle rookeries. We se quenced an 817 bp mitochondrial DNA fragment in 2427 samples from nesting beaches in the southeastern USA, Cay Sal Bank, Bahamas, and Quintana Roo, Mexico. Pairwise FST comparisons, pairwise exact tests of population differentiation, and analysis of molecular variance support previously proposed management unit designations and additionally indicate that southeastern and south- western Florida rookeries should be recognized as distinct management units. Therefore, North- west Atlantic loggerhead turtle rookeries can be subdivided into 10 management units, corre- sponding to the beaches from (1) Virginia through northeastern Florida, (2) central eastern Florida, (3) southeastern Florida, (4) Dry Tortugas, Florida, (5) Cay Sal, Bahamas, (6) southwestern Cuba, (7) Quintana Roo, Mexico, (8) southwestern Florida, (9) central western Florida, and (10) northwestern Florida. We confirmed increased resolution of stock structure between many North- west Atlantic management units and the Cape Verde rookery with the expanded control region haplotypes.

Buccal and cloacal swabs have been used for genetic sampling for a variety of reptiles but not for marine turtles to date. We evaluated whether this method offers a simple and quick way to sample cells from live marine turtles in the wild when it is not feasible to obtain blood or skin. Good-quality DNA was obtained for genetic analyses from both buccal and cloacal swabs. Although we recommend blood and skin sampling whenever possible to collect the highest quality DNA, buccal and cloacal swabs do represent a useful alternative for genetic sampling when these preferred methods are not feasible.

Interactions between sea turtles and sea scallop dredges are an important conservation issue. In this paper, we present information which can be used to inform bycatch mitigation strategies. We collected samples and data from turtles observed in the U.S. commercial scallop dredge fishery and examined interactions and injuries, genetic samples, and turtle size. Observers documented injuries in about two-thirds (52 of 74) of the live and fresh dead turtles. When the location of the turtle in the gear was described, it was most frequently reported in the dredge ( n = 19), in the bag ( n = 9), or on top of the catch ( n = 7). Although several different injury and interaction scenarios were described by observers, the most common was an injured turtle, caught in the dredge, and brought aboard the fishing vessel. The timing of injuries was often unknown, but when observer comments provided information about timing, most injuries likely occurred before the turtle was brought aboard the vessel. The majority of turtles observed in the scallop dredge fishery were juvenile loggerheads. Mixed stock analysis using genetic data, suggested that most loggerheads captured in the scallop fisheries are from the south Florida nesting population, however there was a high level of uncertainty in these estimates.

Juvenile loggerhead turtles (Caretta caretta) from West Atlantic nesting beaches occupy oceanic (pelagic) habitats in the eastern Atlantic and Mediterranean, whereas larger juvenile turtles occupy shallow (neritic) habitats along the continental coastline of North America. Hence the switch from oceanic to neritic stage can involve a trans-oceanic migration. Several researchers have suggested that at the end of the oceanic phase, juveniles are homing to feeding habitats in the vicinity of their natal rookery. To test the hypothesis of juvenile homing behaviour, we surveyed 10 juvenile feeding zones across the eastern USA with mitochondrial DNA control region sequences (N = 1437) and compared these samples to potential source (nesting) populations in the Atlantic Ocean and Mediterranean Sea (N = 465). The results indicated a shallow, but significant, population structure of neritic juveniles (ΦST = 0.0088, P = 0.016), and haplotype frequency differences were significantly correlated between coastal feeding populations and adjacent nesting populations (Mantel test R2 = 0.52, P = 0.001). Mixed stock analyses (using a Bayesian algorithm) indicated that juveniles occurred at elevated frequency in the vicinity of their natal rookery. Hence, all lines of evidence supported the hypothesis of juvenile homing in loggerhead turtles. While not as precise as the homing of breeding adults, this behaviour nonetheless places juvenile turtles in the vicinity of their natal nesting colonies. Some of the coastal hazards that affect declining nesting populations may also affect the next generation of turtles feeding in nearby habitats.

During five cruises in a 1.5-yr period between February 1999 and November 2000, we studied the abundance, vertical distribution, and population structure of the calanoid copepod Metridia gerlachei (Giesbrecht) at Port Foster, a 160 m deep embayment of Deception Island, Antarctica. M. gerlachei was found at Port Foster year round with abundance peaking in early winter 2000, averaging about 200 copepods m−3 over the entire water column, and up to 800 copepods m−3 at mid-water depths. Diel vertical migration of the M. gerlachei population was observed during some parts of the year, while there was no evidence for seasonal vertical migration. Based on analysis of developmental stage-frequency analysis and abundance data, we speculate that M. gerlachei had three generations per year, began to spawn early in the spring, and had the strongest reproductive effort late in the fall. Using daily carbon ration estimates, M. gerlachei accounted for

More than two decades have passed since the first studies documenting genetic population structure of green turtles (Chelonia mydas) were published. Since then many more have followed and characterization of the genetic structure of green turtle rookeries now covers most of the global distribution of the species, benefitting conservation of this threatened species worldwide. However, important data gaps still exist across a large part of the western and central Pacific Ocean (WCPO). This large area is made up of hundreds of scattered islands and atolls of Micronesia, Melanesia, and Polynesia, most of which are remote and difficult to access. In this study, we assessed stock structure of green turtles throughout the WCPO using mitochondrial (mt) DNA from 805 turtles sampled across 25 nesting locations. We examined whether sequencing longer fragments (770 bp) of the control region increases resolution of stock structure and used genetic analysis to evaluate level of demographic connectivity among ...

Sea turtle populations disperse widely across oceans and migrate between terrestrial nesting habitat and distant feeding and developmental habitats. Understanding population stock structure is important for accurately assessing threats such as mortality from fishery bycatch and for defining specific demographic units of conservation concern. We compared 775 bp mtDNA control region haplotypes from 389 juvenile loggerhead turtles sampled as bycatch in the US pelagic longline fishery in the western North Atlantic Northeast Distant (NED) region to haplo- type frequencies observed in 23 genetically distinct nesting stocks representing the 4 distinct pop- ulation segments (DPSs) that have been identified throughout the Atlantic Ocean and Mediterran- ean Sea. We used Bayesian mixed-stock analysis to produce stock composition estimates for juvenile loggerhead turtles that use pelagic habitat in the central North Atlantic. We found that nearly all of the loggerheads caught in NED waters belonged to the Northwest Atlantic DPS (mean = 99.2%), with the majority coming from the large eastern Florida rookeries (mean = 84.0%). We also detected contributions from the western Florida rookeries (mean = 11.7%) and Mexico (mean = 3.5%) but found little evidence of contributions from the rookeries of the South Atlantic, Northeast Atlantic, or Mediterranean DPSs. These results will help improve specific threat assessments and are relevant to ongoing development of conservation plans that are aligned to the recent DPS listings for loggerheads.

Environmental DNA (eDNA) analysis is a rapid, non-invasive method for species detection and distribution assessment using DNA released into the surrounding environment by an organism. eDNA analysis is recognised as a powerful tool for detecting endangered or rare species in a range of ecosystems. Although the number of studies using eDNA analysis in marine systems is continually increasing, there appears to be no published studies investigating the use of eDNA analysis to detect sea turtles in natural conditions. We tested the efficacy of two primer pairs known to amplify DNA fragments of differing lengths (488 and 253 bp) from Chelonia mydas tissues for detecting C. mydas eDNA in water samples. The capture, extraction, and amplification of C. mydas eDNA from aquaria (Sea World, San Diego, CA, United States) and natural water (San Diego Bay, CA, United States) were successful using either primer set. The primer pair providing the shorter amplicon, LCMint2/H950g, demonstrated the ability to distinguish cross-reactive species by melt curve analysis and provided superior amplification metrics compared to the other primer set (LTCM2/HDCM2); although primer dimer was observed, warranting future design refinement. Results indicated that water samples taken from deeper depths might improve detection frequency, consistent with C. mydas behaviour. Overall, this pilot study suggests that with refinement of sampling methodology and further assay optimisation, eDNA analysis represents a promising tool to monitor C. mydas. Potential applications include rapid assessment across broad geographical areas to pinpoint promising locations for further evaluation with traditional methods.