Bryan P. Wallace

Global Conservation Priorities for Marine Turtles

Where conservation resources are limited and conservation targets are diverse, robust yet flexible priority-setting frameworks are vital. Priority-setting is especially important for geographically widespread species with distinct populations subject to multiple threats that operate on different spatial and temporal scales. Marine turtles are widely distributed and exhibit intra-specific variations in population sizes and trends, as well as reproduction and morphology. However, current global extinction risk assessment frameworks do not assess conservation status of spatially and biologically distinct marine turtle Regional Management Units (RMUs), and thus do not capture variations in population trends, impacts of threats, or necessary conservation actions across individual populations. To address this issue, we developed a new assessment framework that allowed us to evaluate, compare and organize marine turtle RMUs according to status and threats criteria. Because conservation priorities can vary widely (i.e. from avoiding imminent extinction to maintaining long-term monitoring efforts) we developed a “conservation priorities portfolio” system using categories of paired risk and threats scores for all RMUs (n = 58). We performed these assessments and rankings globally, by species, by ocean basin, and by recognized geopolitical bodies to identify patterns in risk, threats, and data gaps at different scales. This process resulted in characterization of risk and threats to all marine turtle RMUs, including identification of the worlds 11 most endangered marine turtle RMUs based on highest risk and threats scores. This system also highlighted important gaps in available information that is crucial for accurate conservation assessments. Overall, this priority-setting framework can provide guidance for research and conservation priorities at multiple relevant scales, and should serve as a model for conservation status assessments and priority-setting for widespread, long-lived taxa.

Regional Management Units for Marine Turtles: A Novel Framework for Prioritizing Conservation and Research across Multiple Scales

Background Resolving threats to widely distributed marine megafauna requires definition of the geographic distributions of both the threats as well as the population unit(s) of interest. In turn, because individual threats can operate on varying spatial scales, their impacts can affect different segments of a population of the same species. Therefore, integration of multiple tools and techniques — including site-based monitoring, genetic analyses, mark-recapture studies and telemetry — can facilitate robust definitions of population segments at multiple biological and spatial scales to address different management and research challenges. Methodology/Principal Findings To address these issues for marine turtles, we collated all available studies on marine turtle biogeography, including nesting sites, population abundances and trends, population genetics, and satellite telemetry. We georeferenced this information to generate separate layers for nesting sites, genetic stocks, and core distributions of population segments of all marine turtle species. We then spatially integrated this information from fine- to coarse-spatial scales to develop nested envelope models, or Regional Management Units (RMUs), for marine turtles globally. Conclusions/Significance The RMU framework is a solution to the challenge of how to organize marine turtles into units of protection above the level of nesting populations, but below the level of species, within regional entities that might be on independent evolutionary trajectories. Among many potential applications, RMUs provide a framework for identifying data gaps, assessing high diversity areas for multiple species and genetic stocks, and evaluating conservation status of marine turtles. Furthermore, RMUs allow for identification of geographic barriers to gene flow, and can provide valuable guidance to marine spatial planning initiatives that integrate spatial distributions of protected species and human activities. In addition, the RMU framework — including maps and supporting metadata — will be an iterative, user-driven tool made publicly available in an online application for comments, improvements, download and analysis.

Global patterns of marine mammal, seabird, and sea turtle bycatch reveal taxa-specific and cumulative megafauna hotspots

Significance Loss of megafauna, termed trophic downgrading, has been found to affect biotic interactions, disturbance regimes, species invasions, and nutrient cycling. One recognized cause in air-breathing marine megafauna is incidental capture or bycatch by fisheries. Characterizing megafauna bycatch patterns across large ocean regions is limited by data availability but essential to direct conservation and management resources. We use empirical data to identify the global distribution and magnitude of seabird, marine mammal, and sea turtle bycatch in three widely used fishing gears. We identify taxa-specific hotspots and find evidence of cumulative impacts. This analysis provides an unprecedented global assessment of the distribution and magnitude of air-breathing megafauna bycatch, highlighting its cumulative nature and the urgent need to build on existing mitigation successes. Recent research on ocean health has found large predator abundance to be a key element of ocean condition. Fisheries can impact large predator abundance directly through targeted capture and indirectly through incidental capture of nontarget species or bycatch. However, measures of the global nature of bycatch are lacking for air-breathing megafauna. We fill this knowledge gap and present a synoptic global assessment of the distribution and intensity of bycatch of seabirds, marine mammals, and sea turtles based on empirical data from the three most commonly used types of fishing gears worldwide. We identify taxa-specific hotspots of bycatch intensity and find evidence of cumulative impacts across fishing fleets and gears. This global map of bycatch illustrates where data are particularly scarce—in coastal and small-scale fisheries and ocean regions that support developed industrial fisheries and millions of small-scale fishers—and identifies fishing areas where, given the evidence of cumulative hotspots across gear and taxa, traditional species or gear-specific bycatch management and mitigation efforts may be necessary but not sufficient. Given the global distribution of bycatch and the mitigation success achieved by some fleets, the reduction of air-breathing megafauna bycatch is both an urgent and achievable conservation priority.

Impacts of fisheries bycatch on marine turtle populations worldwide: toward conservation and research priorities

Fisheries bycatch is considered the most serious threat globally to long-lived marine megafauna (e.g., mammals, birds, turtles, elasmobranchs). However, bycatch assessments to date have not evaluated population-level bycatch impacts across fishing gears. Here, we provide the first global, multi-gear evaluation of population-level fisheries bycatch impacts for marine turtles. To compare bycatch impacts of multiple gears within and among marine turtle populations (or regional management units, RMUs), we compiled more than 1,800 records from over 230 sources of reported marine turtle bycatch in longline, net, and trawl fisheries worldwide that were published between 1990–2011. The highest bycatch rates and levels of observed effort for each gear category occurred in the East Pacific, Northwest and Southwest Atlantic, and Mediterranean regions, which were also the regions of highest data availability. Overall, available data were dominated by longline records (nearly 60% of all records), and were non-uniforml...

Bioenergetics and diving activity of internesting leatherback turtles Dermochelys coriacea at Parque Nacional Marino Las Baulas, Costa Rica.

SUMMARY Physiology, environment and life history demands interact to influence marine turtle bioenergetics and activity. However, metabolism and diving behavior of free-swimming marine turtles have not been measured simultaneously. Using doubly labeled water, we obtained the first field metabolic rates (FMRs; 0.20–0.74 W kg–1) and water fluxes (16–30% TBW day–1, where TBW=total body water) for free-ranging marine turtles and combined these data with dive information from electronic archival tags to investigate the bioenergetics and diving activity of reproductive adult female leatherback turtles Dermochelys coriacea. Mean dive durations (7.8±2.4 min (±1 s.d.), bottom times (2.7±0.8 min), and percentage of time spent in water temperatures (Tw) ≤24°C (9.5±5.7%) increased with increasing mean maximum dive depths (22.6±7.1 m; all P≤0.001). The FMRs increased with longer mean dive durations, bottom times and surface intervals and increased time spent in Tw≤24°C (all r2≥0.99). This suggests that low FMRs and activity levels, combined with shuttling between different water temperatures, could allow leatherbacks to avoid overheating while in warm tropical waters. Additionally, internesting leatherback dive durations were consistently shorter than aerobic dive limits calculated from our FMRs (11.7–44.3 min). Our results indicate that internesting female leatherbacks maintained low FMRs and activity levels, thereby spending relatively little energy while active at sea. Future studies should incorporate data on metabolic rate, dive patterns, water temperatures, and body temperatures to develop further the relationship between physiological and life history demands and marine turtle bioenergetics and activity.

Biotic and Abiotic Factors Affect the Nest Environment of Embryonic Leatherback Turtles, Dermochelys coriacea

Clutches of leatherback turtles, Dermochelys coriacea, have lower hatching success than those of other sea turtles, but causes of high embryonic mortality are unknown. We measured characteristics of clutches along with spatial and temporal changes in PO2 and temperature during incubation to determine the extent to which they affected the developmental environment of leatherback embryos. Minimum PO2 in nests decreased as both the total number and mass of metabolizing embryos increased. Increases in both the number and mass of metabolizing embryos caused an increase in maximum nest temperature. However, neither PO2 nor temperature was correlated with hatching success. Our measurements of relatively high nest PO2 (lowest 17.1 kPa or 16.9% O2) indicate that hypoxia apparently does not cause the low hatching success of leatherback clutches. Oxygen partial pressure increased and temperature decreased from the center toward the periphery of leatherback nests. We inferred from these measurements that positions of eggs within nests vary in quality and potentially affect overall developmental success of entire clutches. The large metabolic mass of leatherback clutches and limits to gas flux imposed by the sand create a situation in which leatherback embryos collectively affect their own environment.

Global priorities for marine biodiversity conservation.

In recent decades, many marine populations have experienced major declines in abundance, but we still know little about where management interventions may help protect the highest levels of marine biodiversity. We used modeled spatial distribution data for nearly 12,500 species to quantify global patterns of species richness and two measures of endemism. By combining these data with spatial information on cumulative human impacts, we identified priority areas where marine biodiversity is most and least impacted by human activities, both within Exclusive Economic Zones (EEZs) and Areas Beyond National Jurisdiction (ABNJ). Our analyses highlighted places that are both accepted priorities for marine conservation like the Coral Triangle, as well as less well-known locations in the southwest Indian Ocean, western Pacific Ocean, Arctic and Antarctic Oceans, and within semi-enclosed seas like the Mediterranean and Baltic Seas. Within highly impacted priority areas, climate and fishing were the biggest stressors. Although new priorities may arise as we continue to improve marine species range datasets, results from this work are an essential first step in guiding limited resources to regions where investment could best sustain marine biodiversity.

Signs of hope in the eastern Pacific: international collaboration reveals encouraging status for a severely depleted population of hawksbill turtles Eretmochelys imbricata.

While little is known about hawksbill turtles Eretmochelys imbricata in the eastern Pacific Ocean, available information suggests that the population has declined substantially in recent decades and could be near extirpation in the region. To evaluate the current status of the population more effectively and to determine the feasibility of recovery efforts, a workshop of regional marine turtle specialists was held in June 2008 in Los Cobanos, El Salvador. An international working group, Iniciativa Carey del Pacifico Oriental (ICAPO; Eastern Pacific Hawksbill Initiative in English), was established to consolidate information, promote conservation projects and raise awareness about the species. We present information derived from the workshop and compiled by the ICAPO working group since that time. Considering only records from 1 January 2007 to 31 May 2009 it appears that El Salvador hosts the majority of known hawksbill turtle nesting activity in the eastern Pacific, with 79.6% (n = 430) of all nesting observation records, and Mexico hosts the majority of records of hawksbill turtles at sea, with 60.3% (n = 44) of all in-water observation records. Although current abundance is very low, the pervasiveness of the species in the region suggests potential for conservation and recovery. Despite a historical paucity of research focusing on this population, the relatively large and steadily increasing number of records as a result of concerted efforts demonstrates the viability of the ICAPO network as an instrument to promote conservation of this species in the eastern Pacific.

Shifting the life-history paradigm: discovery of novel habitat use by hawksbill turtles

Adult hawksbill turtles (Eretmochelys imbricata) are typically described as open-coast, coral reef and hard substrate dwellers. Here, we report new satellite tracking data on female hawksbills from several countries in the eastern Pacific that revealed previously undocumented behaviour for adults of the species. In contrast to patterns of habitat use exhibited by their Caribbean and Indo-Pacific counterparts, eastern Pacific hawksbills generally occupied inshore estuaries, wherein they had strong associations with mangrove saltwater forests. The use of inshore habitats and affinities with mangrove saltwater forests presents a previously unknown life-history paradigm for adult hawksbill turtles and suggests a potentially unique evolutionary trajectory for the species. Our findings highlight the variability in life-history strategies that marine turtles and other wide-ranging marine wildlife may exhibit among ocean regions, and the importance of understanding such disparities from an ecological and management perspective.

Effect of Egg Location and Respiratory Gas Concentrations on Developmental Success in Nests of the Leatherback Turtle, Dermochelys coriacea

Hatching success of leatherback turtles, Dermochelys coriacea, is typically ~50%, but the reasons for embryonic death are unknown. We investigated the distribution of egg failure within 16 developing nests to determine whether spatial position or respiratory environment was associated with embryonic death. We measured oxygen and carbon dioxide partial pressures during incubation to investigate whether any spatial variation in developmental success was associated with regions of hypoxia or hypercapnia. Eggs in the centre of nests had a significantly lower mean hatching success (42.1 ± 7.6%) than eggs in the intermediate (66.1 ± 5.3%) and peripheral (69.8 ± 3.5%) regions. Of those eggs that died, there were no significant differences in the timing of early- and late-stage embryonic death in central (77.6 ± 7.2% early death, 17.3 ± 8.2% late death) and peripheral (80.8 ± 10.1% early death, 14.7 ± 5.8% late death) regions. Oxygen tension in all regions of nests was significantly lower and carbon dioxide tension was significantly higher than in control nests by Day 35 of incubation. Although spatial variation in respiratory gases was detected, it did not appear to explain spatially variable developmental success because late-stage embryonic death did not increase in the central region where oxygen tension was lowest and carbon dioxide tension was highest.