Ortega, A. A., Mitchell, N. J., Marn, N., & Shillinger, G. L. (2024). A systematic review protocol for quantifying bycatch of critically endangered leatherback sea turtles within the Pacific Ocean basin. Environmental Evidence, 13(1). https://doi.org/10.1186/s13750-024-00352-3

The Pacific Ocean supports two leatherback sea turtle populations, each of which is Critically Endangered primarily as a result of ongoing incidental bycatch within small-scale and industrial fisheries. Conservation planning has included population viability analysis (PVA), which depends on accurate data on mortality and morbidity (sublethal effects) rates to yield realistic results that can inform management decision-making. Existing leatherback PVAs are based on best available data, however, estimates of mortality and morbidity rates are heavily influenced by estimates of bycatch. These, in turn, are based on unknown levels of observer coverage in many fisheries, estimated to be less than 1% coverage in some artisanal and industrial fleets. Leatherback population recovery depends on bycatch reduction. It is vital to understand the source, scope, and scale of leatherback bycatch wherever and whenever leatherbacks occur. Here, we outline a protocol for a systematic review to aggregate existing estimates of leatherback bycatch within the Pacific Ocean, on a population- and basin-level. These results will generate the first comprehensive estimate of leatherback turtle bycatch for any ocean basin and will be incorporated into future conservation planning for Pacific Ocean populations.

Rousso, S. J., Perezrul, M. D. H., Mancini, A., Zavala-Norzagaray, A. A., & Senko, J. F. (2024). Citizen science enhances understanding of sea turtle distribution in the Gulf of California. PeerJ, 12, e18203. https://doi.org/10.7717/peerj.18203

Citizen science is a valuable tool for addressing spatial distribution gaps in endangered species, especially in data-limited regions. Given the logistical and financial challenges of studying migratory species, this cost-effective approach contributes to strategic conservation planning. The Bay of La Paz, located in Baja California Sur, México, is considered an ecologically important region within the larger Gulf of California. Due to its rich biodiversity and abundant natural resources, the region serves as a hub for ecotourism and fishing, affording diverse opportunities for community-based scientific initiatives. This paper examines the value of citizen science contributions from three diverse community groups (i.e., coastal residents, SCUBA divers, and artisanal fishers) to help scientists obtain information on sea turtle distribution in the Bay of La Paz. Our findings represent the first records of loggerhead turtles (Caretta caretta) in the bay based on ten citizen science reports that include live and dead turtles (either observed swimming, as bycatch, or stranded), providing new information on an endangered pelagic species identified in a coastal bay. Although the sample size is small, our diversity of sources and sighting types highlight the value of collaborative citizen science initiatives in complementing traditional research methods.

Kuschke, S. G., Wyneken, J., & Miller, D. (2024). Baseline skin microbiota of the leatherback sea turtle. MDPI. https://doi.org/10.3390/microorganisms12050925

The integumentary system of the leatherback sea turtle (Dermochelys coriacea) is the most visible and defining difference of the species, with its smooth and waxy carapace and finely scaled skin, distinguishing it from the other six sea turtle species. The skin is the body’s largest organ and serves as a primary defense against the outside world and is thus essential to health. To date, we have begun to understand that the microorganisms located on the skin aid in these functions. However, many host–microbial interactions are not yet fully defined or understood. Prior to uncovering these crucial host–microbial interactions, we must first understand the communities of microorganisms present and how they differ through life-stage classes and across the body. Here, we present a comprehensive bacterial microbial profile on the skin of leatherbacks. Using next-generation sequencing (NGS), we identified the major groups of bacteria on the skin of neonates at emergence, neonates at 3–4 weeks of age (i.e., post-hatchlings), and nesting females. These data show that the predominant bacteria on the skin of the leatherback are different at each life-stage class sampled. This suggests that there is a shift in the microbial communities of the skin associated with life-stage class or even possibly age. We also found that different sample locations on the nesting female (i.e., carapace and front appendages = flipper) have significantly different communities of bacteria present. This is likely due to differences in the microhabitats of these anatomic locations and future studies should explore if this variation also holds true for neonates. These data define baseline skin microbiota on the leatherback and can serve as a foundation for additional work to broaden our understanding of the leatherbacks’ host–microbial interactions, the impacts of environmental changes or stressors over time, and even the pathogenicity of disease processes.

Candela, T., Wyneken, J., Leijen, P., Gaspar, P., Vandeperre, F., Norton, T., Mustin, W., Temple-Boyer, J., Turla, E., Barbour, N., Williamson, S., Guedes, R., Graça, G., Beltran, I., Batalha, J., Herguedas, A., Zailo, D., Baboolal, V., Casella, F., & Shillinger, G. L. (2024). Novel microsatellite tags hold promise for illuminating the lost years in four sea turtle species. MDPI. https://doi.org/10.3390/ani14060903

After hatching, sea turtles leave the nest and disperse into the ocean. Many years later, they return to their natal coastlines. The period between their leaving and their returning to natal areas, known as the “Lost Years”, is poorly understood. Satellite tracking studies aimed at studying the “Lost Years” are challenging due to the small size and prolonged dispersal phases of young individuals. Here, we summarize preliminary findings about the performance of prototype microsatellite tags deployed over a three-year period on 160 neonate to small juvenile sea turtles from four species released in the North Atlantic Ocean. We provide an overview of results analyzing tag performance with metrics to investigate transmission characteristics and causes of tag failure. Our results reveal that, despite certain unfavorable transmission features, overall tag performance was satisfactory. However, most track durations were shorter than those observed on individuals of similar size in other studies and did not allow for detailed analyses of trajectories and turtle behavior. Our study further suggests that tracking durations are correlated with the targeted species, highlighting a lack of robustness against some neritic behaviors. Unprecedented diving data obtained for neonate sea turtles in this study suggest that the vertical behaviors of early juveniles are already too strenuous for these miniaturized tags. Our findings will help to inform the biologging research community, showcasing recent technological advances for the species and life stages within our study.

Kuschke SG, Wyneken J, Cray C, Turla E, Kinsella M and Miller DL (2023) Fusarium spp. an emerging fungal threat to leatherback (Dermochelys coriacea) eggs and neonates. Front. Mar. Sci. 10:1170376. doi: 10.3389/fmars.2023.1170376

Fungal diseases are a rising health problem globally, in humans, nonhuman animals, and plants. Emerging fungal diseases have been associated with mass mortality events. A recent example of fungal disease pathogenicity is sea turtle egg fusariosis (STEF). The pathogenicity of STEF has been linked to fungi within the Fusarium solani species complex (FSSC). This complex is composed of over 45 phylogenetically identifiable species commonly found in the environment. Species within the FSSC lineage have been isolated from the nests of multiple sea turtle species and are linked to decreased hatching success in all 7 of the extant sea turtle species. Fungi within this lineage are also known to cause cutaneous and subcutaneous infections. These fungi are not only a threat to sea turtles but also to other animals, including humans, that use coastal waters and beaches inhabited by Fusarium spp. The presence of Fusarium spp., in the context of sea turtle health, has not been investigated on southeastern Florida beaches which are fundamentally important for at least three sea turtle species that nest there in large numbers.

Williamson, S. A., Hoover, A. L., Evans, R. G., Shillinger, G. L., Bailey, H., Bruno, R. S., Bandimere, A., & Reina, R. D. (2023). Effects of postovipositional hypoxia and hyperoxia on leatherback turtle reproductive success and hatchling performance. Journal of Experimental Zoology Part A: Ecological and Integrative Physiology, 1–12. https://doi.org/10.1002/jez.2743

Leatherback egg clutches typically experience lower hatching success (~50%)than those of other sea turtle species (>70%). The majority of embryonic death(>50%) occurs at early stages of development, possibly because embryos fail to break pre ovipositional embryonic arrest after oviposition. The embryonic arrest is maintained by hypoxia in the oviduct and following oviposition increased availability of oxygen is the trigger that breaks arrest in all turtle species studied to date. We conducted an ex situ incubator experiment and an in situ hatchery experiment to examine the influence of oxygen availability on hatching success and hatchling traits in leatherbacks. After oviposition, eggs (n= 1005) were incubated in either normoxia(21%O2), hyperoxia (32%–42% O2) for 5 days, or hypoxia (1% O2) for 3 or 5 days. As with other turtles, hypoxic incubators maintained embryos in arrest, equivalent to the time spent in hypoxia. However,extending arrest for 5 days resulted in greater early‐stage death and a significant decrease in hatching success (4% 5‐day hypoxia vs. 72% normoxia).Eggs placed in incubators had greater hatching success than those placed into hatchery nests (67% vs. 47%, respectively). We found no impact of hyperoxia on the stage of embryonic death, hatching success, hatchling phenotype, exercise performance, or early dispersal. Our findings indicate that delayed nesting and the subsequent extension of embryonic arrest may negatively impact embryonic development and therefore the reproductive success of leatherbacks. They alsoindicate that incubation under hyperoxic conditions is unlikely to be a useful method to improve hatching success in this species.

Barbour, N., Shillinger, G. L.,Gurarie, E., Hoover, A. L., Gaspar, P., Temple-Boyer, J.,Candela, T., Fagan, W. F., & Bailey, H. (2023). Incorporating multidimensional behavior into a risk management tool for a critically endangered and migratory species.Conservation Biology, e14114. https://doi.org/10.1111/cobi.14114

Conservation of migratory species exhibiting wide-ranging and multidimensional behaviors is challenged by management efforts that only utilize horizontal movements or produce static spatial–temporal products. For the deep-diving, critically endangered eastern Pacific leatherback turtle, tools that predict where turtles have high risks of fisheries interactions are urgently needed to prevent further population decline. We incorporated horizontal–vertical movement model results with spatial–temporal kernel density estimates and threat data (gear-specific fishing) to develop monthly maps of spatial risk. Specifically, we applied multistate hidden Markov models to a biotelemetry data set (n = 28 leatherback tracks, 2004–2007). Tracks with dive information were used to characterize turtle behavior as belonging to 1 of 3 states (transiting, residential with mixed diving, and residential with deep diving). Recent fishing effort data from Global Fishing Watch were integrated with predicted behaviors and monthly space-use estimates to create maps of relative risk of turtle–fisheries interactions. Drifting (pelagic) longline fishing gear had the highest average monthly fishing effort in the study region, and risk indices showed this gear to also have the greatest potential for high-risk interactions with turtles in a residential, deep-diving behavioral state. Monthly relative risk surfaces for all gears and behaviors were added to South Pacific TurtleWatch (SPTW) (https://www.upwell.org/sptw), a dynamic management tool for this leatherback population. These modifications will refine SPTW's capability to provide important predictions of potential high-risk bycatch areas for turtles undertaking specific behaviors. Our results demonstrate how multidimensional movement data, spatial–temporal density estimates, and threat data can be used to create a unique conservation tool. These methods serve as a framework for incorporating behavior into similar tools for other aquatic, aerial, and terrestrial taxa with multidimensional movement behaviors.

Barbour, N., Bailey, H., Fagan, W. F., Mustin, W., Baboolal, V., Casella, F., Candela, T., Gaspar, P., Williamson, S., Turla, E., & Shillinger, G. L. (2023). Satellite Tracking of Head-Started Juvenile Green Turtles (Chelonia mydas) Reveals Release Effects and an Ontogenetic Shift. Animals, 13(7), 1218. https://doi.org/10.3390/ani13071218

Juveniles of marine species, such as sea turtles, are often understudied in movement ecology. To determine dispersal patterns and release effects, we released 40 satellite-tagged juvenile head-started green turtles (Chelonia mydas, 1–4 years) from two separate locations (January and July 2023) off the coast of the Cayman Islands. A statistical model and vector plots were used to determine drivers of turtle directional swimming persistence and the role of ocean current direction. More than half (N = 22) effectively dispersed in 6–22 days from the islands to surrounding areas. The January turtles radiated out (185–1138 km) in distinct directions in contrast to the northward dispersal of the July turtles (27–396 km). Statistical results and vector plots supported that daily swimming persistence increased towards the end of tracks and near coastal regions, with turtles largely swimming in opposition to ocean currents. These results demonstrate that captive-reared juvenile greens have the ability to successfully navigate towards key coastal developmental habitats. Differences in dispersal (January vs. July) further support the importance of release timing and location. Our results inform conservation of the recovering Caymanian green turtles and we advise on how our methods can be improved and modified for future sea turtle and juvenile movement ecology studies.

Barbour, Nicole, Alexander J.. Robillard, George L. Shillinger, Vyacheslav Lyubchich, David H. Secor, William F. Fagan, and Helen Bailey. 2023. Clustering and classification of vertical movement profiles for ecological inference of behavior. Ecosphere 14(1): https://doi.org/10.1002/ecs2.4384

Vertical movements can expose individuals to rapid changes in physical and trophic environments—for aquatic fauna, dive profiles from biotelemetry data can be used to quantify and categorize vertical movements. Inferences on classes of vertical movement profiles typically rely on subjective summaries of parameters or statistical clustering techniques that utilize Euclidean matching of vertical movement profiles with vertical observation points. These approaches are prone to subjectivity, error, and bias. We used machine learning approaches on a large dataset of vertical time series (N = 28,217 dives) for 31 post-nesting leatherback turtles (Dermochelys coriacea). We applied dynamic time warp (DTW) clustering to group vertical movement (dive) time series by their metrics (depth and duration) into an optimal number of clusters. We then identified environmental covariates associated with each cluster using a generalized additive mixed-effects model (GAMM). A convolutional neural network (CNN) model, trained on standard dive shape types from the literature, was used to classify dives within each DTW cluster by their shape. Two clusters were identified with the DTW approach—these varied in their spatial and temporal distributions, with dependence on environmental covariates, sea surface temperature, bathymetry, sea surface height anomaly, and time-lagged surface chlorophyll a concentrations. CNN classification accuracy of the five standard dive profiles was 95%. Subsequent analyses revealed that the two clusters differed in their composition of standard dive shapes, with each cluster dominated by shapes indicative of distinct behaviors (pelagic foraging and exploration, respectively). The use of these two machine learning approaches allowed for discrete behaviors to be identified from vertical time series data, first by clustering vertical movements by their movement metrics (DTW) and second by classifying dive profiles within each cluster by their shapes (CNN). Statistical inference for the identified clusters found distinct relationships with environmental covariates, supporting hypotheses of vertical niche switching and vertically structured foraging behavior. This approach could be similarly applied to the time series of other animals utilizing the vertical dimension in their movements, including aerial, arboreal, and other aquatic species, to efficiently identify different movement behaviors and inform habitat models.

Liang, Dong, Bailey, Helen, Hoover, Aimee L., Eckert, Scott, Zarate, Patricia, Alfaro-Shigueto, Joanna, Mangel, Jeffrey C., et al. 2023. “ Integrating Telemetry and Point Observations to Inform Management and Conservation of Migratory Marine Species.” Ecosphere 14( 1): e4375. https://doi.org/10.1002/ecs2.4375

Species distribution models have been widely used in both terrestrial and marine systems, and applications have included invasive species management, evaluating potential effects of climate change, and conservation. Generally, only a single type of data can be accommodated within the model structures used, which may lead to higher uncertainty in the predictions when the data are sparse. In this case, it can be beneficial to pool data from multiple sources and data types, such as fishery observations and telemetry data. An integrated species distribution model (ISDM) utilizes data integration methods that address the challenges of harnessing multiple data types to estimate species distribution. In this study, an ISDM approach was developed to link turtle locations gathered as part of fishery observations with those derived from satellite telemetry in the East Pacific Ocean to enhance our understanding of a highly migratory and endangered marine species, the leatherback turtle (Dermochelys coriacea). These models were developed to support a dynamic management tool, South Pacific TurtleWatch, to identify high-risk areas of management concern and help inform bycatch reduction efforts for this critically endangered species. This data fusion approach could be applied to other populations and species for which telemetry and other point source data are available.

Gaspar P, Candela T and Shillinger GL (2022) Dispersal of juvenile leatherback turtles from different Caribbean nesting beaches: A model study. Front. Mar. Sci. 9:959366. doi: 10.3389/fmars.2022.959366

The Northwest Atlantic (NWA) leatherback turtle (Dermochelys coriacea) subpopulation was recently classified as endangered. It nests in the Wider Caribbean Region and includes five genetic stocks, all declining, albeit at different rates. The causes of decline are multiple and difficult to identify based on annual nest counts which integrate the effects of multiple stressors over the entire life history. Demographic models, however, show that survival during the juvenile pelagic stage is the main factor modulating population trends, but this life stage remains largely unobserved. This paper presents a suite of numerical simulations where juveniles from the five NWA stocks disperse under the combined effects of ocean currents and habitat-driven swimming movements. Simulations reveal when and where NWA juveniles likely disperse and, thus, the environmental conditions and anthropogenic threats they may encounter. Simulated individuals initially disperse following either the “Caribbean route,” inside the Caribbean Sea and the Gulf of Mexico (GoM), or the “Atlantic route” east of the Antilles Islands Arc. The percentage of individuals following one or the other route varies markedly with the stock of origin. Late dispersal in the eastern Atlantic Ocean and the Mediterranean Sea is similar in all stocks. Juveniles following the Caribbean route are rapidly entrained northwards by the Gulf Stream and incur a high risk of cold-induced mortality. This mostly affects the Florida stock and the Western Caribbean (WCA) stock nesting in Costa Rica, Panama, and Colombia. The Atlantic route is less lethal as individuals progress more slowly toward higher latitudes. Simulations also show that the percentage of WCA juveniles visiting the GoM is larger than for any other stock. The learned migration goal (LMG) hypothesis, which posits that adult sea turtles tend to exploit foraging areas previously identified at the juvenile stage, may thus explain why WCA adults are overrepresented in the GoM. Finally, our results suggest that the recently observed increase in the percentage of WCA adults migrating into the GoM could be linked to bycatch reduction measures implemented in 2003–2004, combined with an increase in the frequency of Loop Current intrusion and eddy-shedding events that started around the year 2000.

Kuschke, S.G. What lives on and in the sea turtle? A literature review of sea turtle bacterial microbiota. anim microbiome 4, 52 (2022). https://doi.org/10.1186/s42523-022-00202-y

Within the United States, all populations of sea turtles are listed as threatened or endangered under the Endangered Species Act. Identifying methods of supporting health, preventing disease, and treating disease is essential for conservation and management strategies for all species. Over the last few decades, advances in technology and high throughput sequencing have allowed a proliferation of research into core microbiota and microbiomes in humans and animals. Such investigations have proven that microbiota on and within a host can influence physiology, immunity, and development. Accordingly, a comprehensive understanding of microbiota is essential for unearthing the complex relationships within a microbiome and how those interactions and relationships can be used to promote health and prevent or treat disease. The goal of this review is to summarize the current microbiota research available across all species of sea turtles and identify any emerging trends. Methodological differences made it challenging to draw conclusions across studies, but it is apparent that each anatomical location investigated has a unique core microbiota with some potential overlap. In the future, unifying methodology across microbiota studies will allow broader conclusions to be drawn across all anatomic locations and species of sea turtles. These conclusions will then allow clinicians and conservationists to apply the research results in the field. Additionally, future efforts should include a wider range of organisms including fungi, viruses, parasites, epibiota, and archaea to unveil essential relationships among and between the organisms and host for maintenance of a healthy microbiome.

Copsey, J., Ábrego, M., Alvarez, C., Bandimere, A., Baron, J., Barragán, A., Benson, S., Cáceres, V.,Davalos, N.,Dueñas, C., Dutton, P., Flanagan, J., Gadea, V., Gray, K., Gunn, A., Hall, M., Harfush, M., Heppell, S., Herrera, D., Jimenez, A., Juarez, A., Kelez, S., Komoroske, L., Lawson, D., Lohmann, K., Mangel, J., Mast, R., Miller, D., Miller, P., Mitchell, N., Mustin, W., Ortega, A., Otterstrom, S., Plotkin, P., Quioñes, J., Ramos, S., Reina, R., Salas, C., Salazar, H., Sarti, L., Seminoff, J., Shaver, D., Steiner, T., Stewart, K., Trejo, C., Vallejo, F., Veelenturf, C., Wallace, B., Williamson, S., Wyneken, J., Zarate, P. & Shillinger, G. (2021). Eastern Pacific Leatherback Turtle: Ex situ Management Recommendation Development Workshop Report. IUCN SSC Conservation Planning Specialist Group, Apple Valley, MN, USA.

In July 2020, the Conservation Planning Specialist Group (CPSG)1 of the International Union for Conservation of Nature (IUCN) Species Survival Commission (SSC) was enlisted by the international non-profit sea turtle conservation organization, Upwell, to design and facilitate a two-step decision making process to inform conservation efforts for the Critically Endangered Eastern Pacific subpopulation of the leatherback turtle Dermochelys coriacea (shortened to EPLB within the report). The focus of the process was to determine the extent to which ex situ management activities (specifically head-starting and egg translocation) should be considered as complements to in situ efforts for the species. The process involved the participatory development of a Population Viability Analysis (PVA) model for the subpopulation, reflecting both its status and trajectory and potential future trajectories based on different conservation management interventions (both in situ and ex situ). This first phase was then followed by a second participatory planning phase, in which a wider group of stakeholders from both within and beyond the region were led through a series of meetings to develop a shared recommendation for future work. This recommendation was restricted to determining the extent to which head-starting and/or egg translocation could be used as complementary actions to augment ongoing efforts to prevent extinction of the sub-population.

The two-step process began in November 2020 and ended in February 2021. The final recommendation developed was that, given current uncertainties concerning the practicability and likely impact of ex situ management activities on EPLB recovery, such actions should not be embarked upon at the current time, though they merited further examination and study. A range of research themes were identified by the group that should be further investigated to help reduce uncertainties surrounding the ex situ management approaches proposed. This would ensure that, should ongoing in situ interventions be unsuccessful in slowing population decline, or an urgent need for ex situ actions be identified, ex situ conservation practitioners will be better equipped with the knowledge and capabilities to maximize the probability of success of additional ex situ measures.

Degenford JH, Liang D,Bailey H, et al. Using fisheries observation data to develop a predictive species distribution model for endangered sea turtles. Conservation Science and Practice. 2021;3:e349. https://doi.org/10.1111/csp2.349

The Eastern Pacific leatherback turtle population (Dermochelys coriacea) has declined precipitously in recent years. One of the major causes is bycatch from coastal and pelagic fisheries. Fisheries observations are often underutilized, despite strong potential for this data to affect policy. In this study, we created a spatiotemporal species distribution model that synthesizes fisheries observations with remotely sensed environmental data. The model will be developed into a dynamic management tool for the Eastern Pacific leatherback population. We obtained leatherback observation data from multiple fisheries that have operated in the Southeast Pacific (2001–2018). A dynamic Poisson point process model was applied to predict leatherback intensity (observation per unit area) as a function of dynamic environmental covariates. This model serves as a tool for application by managers and stakeholders toward the reduction of leatherback turtle bycatch and provides a modeling framework for analyzing fisheries observations from other vulnerable populations and species.

Hoover, A.L., Shillinger, G.L., Williamson, S.A. et al. Nearshore neonate dispersal of Atlantic leatherback turtles (Dermochelys coriacea) from a non-recovering subpopulation. Sci Rep 10, 18748 (2020). https://doi.org/10.1038/s41598-020-75769-0

The cryptic ‘lost years’ of sea turtles challenge conservation efforts due to unknown movements and habitat utilisation of young life stages. Behavioural information strengthens dispersal and habitat utilisation models estimating unidentified movements. In this study, leatherback hatchlings were actively tracked with miniature acoustic tags off the east coast of Costa Rica for 83.15 min (± 9.12 SD) to determine their movements and swimming behaviour. Drifters were deployed throughout the tracking process to obtain surface current data. Hatchling (n = 42) over-ground and in-water swimming speed and bearing were calculated. Mean over-ground distance travelled was 2.03 km (± 0.71 km SD) with an over-ground average swim speed of 0.41 m/s (± 0.15 m/s SD). Mean bearing was 108.08° (± 20.19° SD) compared to the 137.56° (± 44.00° SD) bearing of nearshore ocean currents during tracking. Hatchling mean in-water swimming speed was 0.25 m/s (± 0.09 m/s SD). The lower in-water speed suggests hatchlings were advected by the currents, with overall movement strongly influenced by the current direction. This information can be assimilated into broader spatiotemporal distribution models to interpret the influence of directional swimming on ecosystem utilisation and help to achieve informed management decisions across all life stages of the population.

Ortiz-Alvarez, C., Pajuelo, M., Grados, D., Abrego, M., Barragán-Rocha, A. R., Barrantes, M. C., Sánchez, A., Fonseca, L. F., Espinal, V. G., Mangel, J. C., Rguez-Baron, J. M., Santidrian-Tomillo, P., Sarti, L., Santana-Hernández, H., Shillinger, G. L., Prado, M. O., Wallace, B. P., Williard, A. S., Zavala-Norzagaray, A. A., & Alfaro-Shigueto, J. (2020). Rapid Assessments of Leatherback Small-Scale Fishery Bycatch in Internesting Areas in the Eastern Pacific Ocean. Frontiers in Marine Science, 6. https://doi.org/10.3389/fmars.2019.00813

The East Pacific (EP) leatherback population is listed by the IUCN Red List of Threatened Species as Critically Endangered. Despite conservation efforts, mainly focused on nesting beaches, its population has declined by over 90% since the 1980s. A major current threat is fisheries bycatch, which has been primarily documented in small-scale gillnets and longlines within South American migration and foraging habitats, but scarcely reported in fisheries that operate in areas near nesting beaches (i.e., inter-nesting areas). To assess the impact of small-scale fisheries on EP leatherbacks inhabiting waters north of the equator we conducted rapid bycatch assessments interviews in five countries (Mexico, Nicaragua, Costa Rica, Panama and Colombia), some of which host the main EP leatherback nesting beaches and inter-nesting areas. A total of 1778 interviews were conducted across 79 fishing ports (Mexico = 37, Nicaragua = 6, Costa Rica = 5, Panama = 17 and Colombia = 14). Leatherback bycatch was reported in all countries, and in 54% of ports assessed by 7% (n = 125) of fishers interviewed. Interviews enabled identification of inter-nesting areas where leatherback bycatch was higher and periods during which fisheries interaction events were more frequent. Bycatch events were most frequently reported in gillnets and secondarily in longlines. Data were extrapolated across fishing fleets to estimate that 345 ± 210 (mean ± SD) individual leatherbacks are caught annually in the ports assessed. Our study provides a first evaluation of leatherback bycatch by small-scale fisheries in countries of the eastern Pacific Ocean where leatherbacks nest, and it highlights areas close to index nesting beaches where conservation efforts targeting bycatch reduction and bycatch mortality may be focused.

Barbour, N., Shillinger, G. L., Hoover, A. L., Williamson, S. A., Coles, V. J., Liang, D., Fagan, W. F., & Bailey, H. (2020). Environmental and Biological Factors Influencing Dispersal of Neonate Leatherback Turtles (Dermochelys coriacea) From an Endangered Costa Rican Nesting Population. Frontiers in Marine Science, 7. https://doi.org/10.3389/fmars.2020.582933

Quantifying early life movements is essential to understanding migratory pathways and habitat use that can impact individuals’ success later in life. To gauge how neonatal movements set the stage for later habitat use, we tracked neonate leatherback turtles (n = 94) with acoustic tags from Pacuare, Costa Rica, in 2016 and 2018. We analyzed movements using a first passage time analysis and random walk models, the results of which indicated neonates followed a fixed compass direction as they traveled away from shore and that strong currents in these areas resulted in advection. We combined the tracking data with concurrent environmental variables in a generalized additive mixed model framework. Our results showed the south-east current flow in this area has spatial and temporal structure consistent with large-scale geostrophic currents and not tidal current or local wind speed influences. After accounting for advection by currents, true neonate swimming speed was significantly related to current speed, first passage time, and the year. Neonates had three main response strategies to currents above 0.5 m s–1, with most increasing their swimming speed and the rest maintaining either a constant or decreased swimming speed. Neonates were significantly larger in 2018 than in 2016 but their average swimming speed was not significantly related to body size, indicating that environmental factors were more important contributors to their dispersal. We conclude that abiotic factors, including the strength and direction of the currents, significantly affect the swimming and dispersal strategy of neonate leatherback turtles and these results can help to inform strategies for releases of neonate turtles from hatcheries, future tracking studies, and conservation efforts.

Vierros, M., Harrison, A., Sloat, M. R., Crespo, G., Moore, J. W., Dunn, D. C., Ota, Y., Cisneros-Montemayor, A. M., Shillinger, G. L., Watson, T. K., & Govan, H. (2020). Considering Indigenous Peoples and local communities in governance of the global ocean commons. Marine Policy, 119, 104039. https://doi.org/10.1016/j.marpol.2020.104039

The United Nations are currently negotiating a new international legally-binding instrument to govern the global ocean commons, a vast area beyond national jurisdiction (ABNJ) owned by everyone but not cared for by any single entity. Indigenous Peoples and local communities (IPLCs) have been underrepresented in the debate about governance of ABNJ despite their internationally recognized rights and their role as custodians of many globally-significant migratory species that travel between coasts and high seas. Here we use examples of active transboundary connectivity by migratory species as case studies to highlight the relevance of IPLCs on islands, coasts and beyond to the governance of the global ocean commons, and make a case for their essential and beneficial inclusion in it. Many migratory species are culturally and economically important to IPLCs, who are frequently the first to suffer if these species are overexploited or decline due to inadequate management in ABNJ. Four case studies (Pacific salmon, Marine Turtles, Black-footed and Laysan Albatrosses, Northern fur seal) illustrate knowledge, innovations and practices of IPLCs that have global importance in informing strategies for conservation, sustainable and equitable use of marine species in general. IPLCs can contribute to enriching the diversity of approaches and solutions, and by elaborating on principles directly relevant for governance of ABNJ within the UN process and beyond.

Hoover, A. L., Liang, D., Alfaro-Shigueto, J., Mangel, J. C., Miller, P. I., Morreale, S. J., Bailey, H. D., & Shillinger, G. L. (2019). Predicting residence time using a continuous‐time discrete‐space model of leatherback turtle satellite telemetry data. Ecosphere, 10(3), e02644. https://doi.org/10.1002/ecs2.2644

The utilization and capabilities of biotelemetry are expanding enormously as technology and access rapidly improve. These large, correlated datasets pose statistical challenges requiring advanced statistical techniques to appropriately interpret and model animal movement. We used satellite telemetry data of critically endangered Eastern Pacific leatherback turtles (Dermochelys coriacea) to develop a habitat-based model of their motility (and conversely residence time) using a hierarchical Bayesian framework, which could be broadly applied across species. To account for the spatiotemporally auto-correlated, unbalanced, and presence-only telemetry observations, in combination with dynamic environmental variables, a novel modeling approach was applied. We expanded a Poisson generalized linear model in a continuous-time discrete-space (CTDS) model framework to predict individual leatherback movement based on environmental drivers, such as sea surface temperature. Population-level movement estimates were then obtained with a Bayesian approach and used to create monthly, near real-time predictions of Eastern Pacific leatherback movement in the South Pacific Ocean. This model framework will inform the development of a dynamic ocean management model, “South Pacific TurtleWatch (SPTW),” and could be applied to telemetry data from other populations and species to predict motility and residence times in dynamic environments, while accounting for statistical uncertainties arising at multiple stages of telemetry analysis.

Cruz, L. M., Shillinger, G. L., Robinson, N. J., Tomillo, P. S., & Paladino, F. V. (2018). Effect of light intensity and wavelength on the in-water orientation of olive ridley turtle hatchlings. Journal of Experimental Marine Biology and Ecology, 505, 52–56. https://doi.org/10.1016/j.jembe.2018.05.002

Light pollution, associated with coastal development, poses a growing threat to sea turtles. Hatchlings are particularly affected during their crawl to the ocean since they exhibit phototaxis and may move towards or be disoriented by artificial lights. Although much is known about how hatchlings respond to artificial light while crawling to the ocean, far less is known about their response after reaching the water. Here, we investigate how hatchling olive ridley turtles (Lepidochelys olivacea) held in artificial pools responded to light of different wavelengths (red, 720 nm; yellow, 660 nm and green, 520 nm) and intensities (0.1–3.3 lx, mean 0.87 lx, SD = 0.85, 10.3–45.9 lx, mean 15.75 lx,SD = 7.12; 47.5–84.2 lx; mean 52.02 lx, SD = 9.11; 91.3–140.8 lx, mean 105 lx, SD = 13.24; 150.1–623 lx, mean 172.18 lx, SD = 73.42). When no light or red light below 39 lx was present, hatchlings oriented at a mean angle of 180° from true north and did not orient towards any discernable feature. However, hatchlings swam towards the light at intensities of red light above 39 lx, yellow light above 10 lx and green light above 5 lx. Our findings indicate that sea turtles will swim towards artificial lights even after reaching the water. Thus, we recommend light mitigation efforts should extend beyond nesting beaches and into the associated oceanic habitats.

Harrison, AL., Costa, D.P., Winship, A.J. et al. The political biogeography of migratory marine predators. Nat Ecol Evol 2, 1571–1578 (2018). https://doi.org/10.1038/s41559-018-0646-8

During their migrations, marine predators experience varying levels of protection and face many threats as they travel through multiple countries’ jurisdictions and across ocean basins. Some populations are declining rapidly. Contributing to such declines is a failure of some international agreements to ensure effective cooperation by the stakeholders responsible for managing species throughout their ranges, including in the high seas, a global commons. Here we use biologging data from marine predators to provide quantitative measures with great potential to inform local, national and international management efforts in the Pacific Ocean. We synthesized a large tracking data set to show how the movements and migratory phenology of 1,648 individuals representing 14 species—from leatherback turtles to white sharks—relate to the geopolitical boundaries of the Pacific Ocean throughout species’ annual cycles. Cumulatively, these species visited 86% of Pacific Ocean countries and some spent three-quarters of their annual cycles in the high seas. With our results, we offer answers to questions posed when designing international strategies for managing migratory species.