REGIONAL ACTION PLAN FOR REVERSING THE DECLINE OF THE EAST PACIFIC LEATHERBACK

Transcription

1 REGIONAL ACTION PLAN FOR REVERSING THE DECLINE OF THE EAST PACIFIC LEATHERBACK

2 Photo credits Cover: Laura Sarti and an assistant measure a nesting leatherback outfitted with a new satellite transmitter in Mexico ( Ana Barragan); Joanna Alfaro- Shigueto scans a leatherback aboard an artisanal fishing vessel in Peru ( ProDelphinus). Above: Participants in the East Pacific leatherback expert workshop, Huatulco, Oaxaca, Mexico ( Jacinto Rodriguez). The National Fish and Wildlife Foundation provided funding for the workshop and development of this Plan of Action, which was an initiative of the IUCN/SSC Marine Turtle Specialist Group.

3 REGIONAL ACTION PLAN FOR REVERSING THE DECLINE OF BACKGROUND The East Pacific (EP) leatherback regional management unit (see map at right) nests along the coast of Mexico, Central, and South America, and its area of occupancy extends from Baja California Sur, Mexico, to central Chile, and westward to 130 W (see map). Primary nesting sites are found in the states of Michoacán, Guerrero, and Oaxaca, in Mexico, and in the province of Guanacaste, Costa Rica. Secondary nesting sites occur throughout México and Costa Rica, but also Nicaragua. Scattered nesting also occurs in Guatemala, El Salvador, Panama, Colombia, and Ecuador. EPO leatherback feeding areas have been documented off Panama, Colombia, Ecuador, Peru, and Chile (Shillinger et al. 2008; 2011; Bailey et al. 2012). THE EAST PACIFIC LEATHERBACK The precipitous decline in the EP leatherback population during the past two decades has been extensively documented (e.g. Santidrián Tomillo et al. 2007; Sarti Martínez et al. 2007), and was recently identified as one of the most endangered sea turtle RMUs in the world (Wallace et al. 2011). Comprehensive reviews of long- term nesting abundance in Mexico (Sarti Martínez et al. 2007) and Costa Rica (Santidrián Tomillo et al. 2007) which together comprise nearly 90% of all EP leatherback nesting concluded that nesting had declined more than 90% since the 1980s (see figure), from thousands of nesting females per year to no more than 1,000 adult females total in the population. Based on estimates of total annual abundance at the regional scale, this population now averages roughly females per year nesting at currently monitored primary and secondary beaches (observed values: females per year). Likewise, the drivers of this decline both anthropogenic (e.g. bycatch, egg harvest) as well as environmental (e.g. resource limitation) have been described in detail (for review see Wallace and Saba 2009). Furthermore, long-

4 term monitoring and conservation programs at the most significant nesting beaches in Mexico and Costa Rica have essentially eliminated threats from human consumption of eggs and nesting females, and ongoing efforts at important sites in Nicaragua are increasing in effectiveness (Urteaga et al., 2012). However, despite these major advances in leatherback conservation, the abundance of this leatherback RMU remains perilously low, and continues to decrease slowly toward regional extirpation (see figure above). For these reasons, the time has come to rethink existing approaches to leatherback conservation in the region, and to implement a new plan of action to save leatherbacks in the EP. This Action Plan outlines the key priority actions identified by a group of regional experts to reverse the decline and to promote long- term recovery of leatherbacks in the East Pacific. DEFINING OUR CONSERVATION GOALS AND OBJECTIVES The EP Leatherback Action Plan provides a 10- year investment strategy to stabilize the population trend in the next 10 years (around females per year by 2023), demonstrate an increasing population trend years from now (significant increase between , or significantly above 200 females per year). To develop this Action Plan, a workshop (with support from National Fish and Wildlife Foundation) was conducted with more than a dozen key leatherback experts from the region, as well as other participants with expertise in sea turtle conservation. Following the workshop, the plan was drafted over several months, incorporating comments and recommendations of numerous experts. The Action Plan establishes ambitious but realistic population goals, defines key activities to address major threats to EP leatherbacks, and outlines specific actions, metrics, timelines and financial needs to ensure success. Thus, the Action Plan provides a roadmap for recovery of the EP leatherback population. The expert working group first decided that the EP leatherback Action Plan should be developed with existing frameworks for Pacific sea turtle conservation in mind. Specifically, the major goals of the EP leatherback Action Plan mirror those of the Bellagio Blueprint for Pacific sea turtle conservation (Bellagio Blueprint 2003). The working group also decided that the population goal should be to prevent further decline that is, stabilize the population trend at an average of females per year (see figure above) in the next 10 years to lay the groundwork for a significant, measureable population increase years from now, i.e. above 200 nesting females

5 per year. It is worth noting that it is unknown whether this population target is sufficient to ensure population viability, but stabilization in any case would be an improvement over recent trends. The figure above shows 1%, 5%, and 10% annual population increases over the next 30 years, which is the monitoring duration that SWOT s Minimum Data Standards for Nesting Beach Monitoring states will enable detection of a 5% trend in a leatherback population. An annual population increase of 1% will not reach the target until 2052, whereas annual increase rates of 5% and 10% will surpass the threshold by 2029 and 2026, respectively. Thus, the target population growth rate should be above 1%. These population trends should be measureable at the major nesting beaches in Mexico and Costa Rica, as well as secondary beaches in Nicaragua and potentially elsewhere in the region. The expert working group established that the most serious threat to EP leatherbacks remains incidental capture in fishing gear i.e., bycatch particularly in South American waters where leatherbacks feed, but including other areas such as those adjacent to nesting beaches where leatherbacks aggregate annually. However, the group also recognized that despite significant achievements in reducing threats from egg and turtle consumption by humans and habitat degradation on nesting beaches, efforts to protect nesting beaches and increase hatchling production must be redoubled as well. Furthermore, the group acknowledged that regional integration and coordination of conservation efforts are necessary to promote exchange of information and techniques necessary to ensure the future recovery of EP leatherbacks. To achieve these population recovery goals, the three overarching strategies of the EP leatherback Action Plan are: 1) Reduce mortality from fisheries bycatch: This includes reducing bycatch in areas already identified as high- bycatch areas, identifying other high- bycatch areas, and identifying and protecting areas that are important for leatherbacks at different life stages. 2) Protect nesting beaches and increase hatchling production: This includes reduction of egg harvest for local and commercial consumption, establishing and/or maintaining monitoring of primary and secondary nesting beaches, preserving important nesting habitats, and maintaining favorable conditions for hatching success. 3) Promote and strengthen implementation of regional actions through existing networks and instruments: This includes efforts to support identification of high- bycatch areas, collection, integration, and analysis of information on leatherback bycatch and population status, reaching agreements with fishing fleets and managers to reduce leatherback bycatch, ensure compliance with existing resolutions to protect leatherbacks, disseminating relevant information about leatherback conservation to policy- makers and decision- makers. Achieving these three goals to promote population recovery can be thought of as a principle- interest model. By reducing bycatch and saving individual turtles, the principle grows, while increasing hatchling production is like interest growing on the principle. Thus, as more individuals are saved and the adult portion of the population grows, so does hatchling production (i.e. the interest), and thus the ability of the total funds to grow. The regional coordination is essentially the sound structure within which the fund is maintained; the healthier the structure, the more secure the fund will be.

6 The projected growth rates in the above figure demonstrate this principle- interest phenomenon clearly. Although the target of 200 nesting females per year is reached at roughly the same time for both the 5% and the 10% annual growth rate scenarios, population abundance of twice the target (i.e., 400 nesting females per year) is reached in 2043 under 5% annual growth, but 10 years earlier under 10% growth. This is because the principle i.e., population abundance capable of future growth is increasing more rapidly under the faster growth scenario (i.e., higher interest rate), which fuels further growth in the population. This Plan is the first- ever, region- wide summary of priority action items directed at EP leatherbacks, developed by an expert working group representing government agencies, non- governmental organizations, international policy instruments, and academic institutions. Although many of the recommended actions described below are currently underway in some place(s) in the region, never before have experts come together assemble a single Plan under a unified regional vision to serve as a guide for collective action to save EP leatherbacks from extirpation. The unique aspects of this Plan, therefore, are found in its regional, short- and long- term targets and activities; a regional monitoring system of nesting beaches, nest temperatures, and hatching success, standardized regional databases for nesting beach and bycatch information, and regional characterizations of leatherback bycatch from different information sources will all be major advances for leatherback conservation in the region. PROPOSED INVESTMENT STRATEGIES At this point, the population targets to be saved by each strategy in the context of what numbers are necessary to ensure population stabilization and eventual recovery should be considered initial estimates. To provide more robust guidance for targets for specific activities and overall strategies, and thus the entire Action Plan, we have included such an assessment as a first step (see Strategy 3). Below, we have provided interim goals and timelines for specific activities, until or unless improved estimates require adjustments in these values. Strategy 1: Reduce mortality from bycatch Bycatch is still considered the major obstacle to population recovery. The latent impacts of high mortality in swordfish driftnets off Chile in the 1990s are likely further hindering recovery, as possibly thousands of adult leatherbacks were killed annually (Frazier and Montero, 1990; Eckert and Sarti, 1997), which eliminated a significant portion of the breeding population and, therefore, their future offspring as well. In addition, ongoing leatherback bycatch in small- scale fisheries in South America continues to impact adults and subadults (Alfaro- Shigueto et al. 2007; 2011; 2012), the two life stages with the largest per- individual impacts on marine turtle population dynamics (Wallace et al. 2008). Leatherback bycatch has not been quantified at the regional scale, thus preventing robust estimation of the level of reduction necessary to stabilize and eventually increase population abundance. However, some information about leatherback bycatch is available for some ports and fishing gears (longline gear and gillnets) in South America. In particular, a recent tri- national project to assess sea turtle bycatch in net fishing gear using port- based surveys in Ecuador, Peru, and Chile provided the only available baseline of leatherback bycatch in the region and highlighted high- bycatch ports. Likewise, several ports in Peru have been identified as having high bycatch in both longlines and nets (see below). Based on existing bycatch assessments mentioned above, between 1,000-2,000 leatherbacks (adult

7 males and females, as well as juveniles) are caught in nets and longlines annually, of which roughly 30%- 50% die as a result of these interactions; therefore, estimated bycatch mortality is between and as many as 1,000 leatherbacks annually. Though some of these are subadults (e.g., Alfaro- Shigueto et al. 2007), those individuals are included as adults for the purposes of this estimate exercise. Assuming that adult sex ratios reflect those of nesting beaches, roughly 75% of the total number of leatherbacks taken as bycatch are adult females, making the annual mortality of adult female leatherbacks approximately 225 to 450 individuals. These estimates are especially troubling, considering that total abundance of nesting females based on beach monitoring in the region is estimated at fewer than 1,000 individuals. This incongruity between adult female abundance based on beach monitoring and estimates of annual bycatches of adult females means that assumptions affecting abundance and/or bycatch estimates require improvements. More importantly, the low certainty in these estimates makes assigning target reductions in bycatch difficult and tenuous. Nonetheless, because targets are needed to shape the regional Plan of Action, the interim goal for this strategy is to reduce annual bycatch mortality by one- third in the next ten years, or by approximately 150 nesting females per year, in Ecuador, Peru, and Chile combined. To achieve this goal, enhanced assessments to better quantify leatherback bycatch and track progress toward reduction goals, as well as capacity- building in fishing communities to reduce bycatch and testing of mitigation measures will be supported at priority ports during the first five years of the Plan. During the same period, assessments will be conducted for other countries in the region, particularly those that host leatherback nesting (e.g. Mexico, Nicaragua, Costa Rica), to further refine quantification of leatherback bycatch, and identify important bycatch areas within these countries, as well as opportunities for mitigation. Significant reductions in bycatch mortality will be critical to stabilizing the EP leatherback population trend because saving subadults and adults translates to direct increases in survivorship of the very life stages we use to quantify population trends Reduce bycatch in areas already identified as high- bycatch Existing assessments have highlighted particular ports as having significant leatherback bycatch that require more in- depth assessments and community- based mitigation efforts. We recommend that actions be taken at ports identified by previous assessments as high- priority ports for leatherback bycatch. These ports include Manta and Santa Rosa, Ecuador, Salaverry, Pisco, San Jose, and Ilo, Peru, and Coquimbo and Lebu, Chile. For many other ports identified as having significant leatherback bycatch (e.g. several ports in Ecuador [Esmereldas, Anconcito, Puerto Bolivar], Peru [Constante, Chimbote, Pucusana, Morro Sama], and Chile [Iquique, Arica, Antofogasta, Caldera]), we recommend that these efforts also be conducted as funds permit Continued assessments of leatherback (and sea turtle) bycatch at ports throughout the three countries using port- based surveys as well as on- board observers (when possible) to establish baselines and follow- up assessments to evaluate progress after mitigation activities Establish three new bases (Santa Rosa, Ecuador; San Jose, Peru; Coquimbo, Chile) for the real- time, sea- to- sea and sea- to- shore radio communication program between conservation groups and fishermen to enhance reporting, safe handling and release of leatherbacks caught in fishing gear, and avoidance of leatherback bycatch when possible. Additional bases may be added in later years of the plan based on the success of this strategy and the identification of other priority bycatch areas.

8 Testing mitigation measures to reduce leatherback bycatch in gillnets and trammel nets in Ecuador and Peru, and in longlines in Peru and Chile Providing training and equipment necessary to ensure safe handling and release of leatherbacks caught in fishing gear (e.g., line cutters, dehookers) to at least 30% of artisanal fishermen in key ports in Ecuador, Peru, and Chile, and to 10% of on- board observers in Chilean longline fleet Workshops to increase awareness, build capacity, and exchange techniques and experiences between conservation groups and local fishing communities (combined with above) Identify other areas as high- bycatch and/or important for leatherback survival Although several ports in South America have been established as having high leatherback bycatch, other areas where leatherback bycatch occurs and could be significant must also be identified. In addition to other high bycatch areas, satellite tracking of adult females from nesting beaches has allowed identification of high- use areas for foraging, but virtually nothing is known about long- term habitat use patterns in the region during the 3-4 year period that females are away from nesting beaches, not to mention the complete lack of data on adult males and subadults. Because fishing activities that occur in feeding areas or near nesting beaches would be of particular concern, countries whose waters host these areas should be assessed. We recommend the following actions throughout the region, but particularly in high- use waters adjacent to nesting beaches and potential feeding areas in the region Expand port- based bycatch assessments of leatherbacks (and other sea turtles) conducted in Ecuador, Peru, and Chile to all countries throughout the region, particularly those known to host leatherback nesting (Mexico, Nicaragua, Costa Rica) and/or feeding areas (Panama, Colombia) targeting at least 3 ports per country and 10% of vessels per port Deploy satellite transmitters on juvenile and adult leatherbacks caught in fishing gear in Peru (and possibly Ecuador and Chile) to elucidate habitat use in feeding areas and to estimate post- release mortality rates, which is a critical piece of information that is essentially unknown for all fishing gears Analysis of distributions of juvenile leatherbacks with respect to oceanographic conditions in the region Analysis of distributions of jellies, leatherbacks, and fisheries activities in the Humboldt Current system Reduce consumption of leatherbacks taken as bycatch In addition to mortality resulting from incidental capture in fishing gear, retention of bycaught leatherbacks for consumption by fishermen is a significant issue in some Peruvian ports, perhaps being the fate for more than 50% of leatherbacks taken as bycatch in some cases. However, as this phenomenon appears to be geographically restricted, we recommend a pilot assessment project to provide insights for future actions to reduce or eliminate this threat Pilot study to assess the magnitude of the impact as well as the motivations for consumption at fishing ports in Peru to inform development of approaches that might reduce this practice Based on results of pilot study, introduce measures to reduce retention in at least two ports, i.e. those where highest incidence of retention found to occur.

9 Strategy 2: Protect nesting beaches (at least 90% of in situ nests) and increase hatchling production (at least 50% hatching success in relocated nests) In contrast to many other sea turtle populations, threats to EP leatherbacks on nesting beaches namely human consumption of eggs and nesting females have been significantly reduced compared to historic trends at major nesting sites in Mexico and Costa Rica. However, egg harvest remains an issue where protection efforts are insufficient or non- existent. Enhanced protection of nesting beaches and increases in hatchling production are efforts that have delayed impacts on population trends because of delayed maturity typical of sea turtles, including leatherbacks, that means years between hatchling and adult stages. Thus, results of increased hatchling production (i.e. investment return ) should not be expected to be observable for at least 15 years, and still depend on survivorship of juvenile and adult life stages. This again puts the highest priority for population recovery on increasing survival of older life stages, i.e. reducing mortality from fisheries bycatch in feeding areas and migratory routes. Nonetheless, without beach protection and increased hatchling production, the reproductive cycle of leatherbacks will be incomplete and would prevent recovery. Therefore, efforts to maintain or enhance protection of nesting turtles, their eggs, and hatchlings must be supported at the same time as bycatch reduction efforts. We recommend actions to enhance or maintain monitoring on nesting beaches, reduce egg harvest, increase resilience of nesting habitats, and maintain nest conditions favorable to hatchling production Establish, increase or maintain presence of monitoring teams on beaches that currently have insufficient or non- existent monitoring and protection We recommend that leatherback nesting sites throughout the region be evaluated for a) relative annual abundance of nesting females, number of clutches, hatching success (and beach conditions), potential hatchling production, and b) degree of monitoring and protection efforts at important nesting beaches. This assessment will allow identification of important beaches that require support for monitoring and protection Assess current status and priorities for monitoring on secondary beaches through workshops and rapid assessments for known secondary beaches Aerial surveys to identify undocumented nesting sites in the region and to provide a current assessment of all nesting beaches in the region Maintain/augment monitoring teams on all index beaches and install teams on at least 8 additional secondary beaches (majority of nesting in region) Reduce egg consumption Promote economic alternatives in local communities in Mexico, Nicaragua, and Costa Rica (and other countries with leatherback nesting) Increase the presence and participation of authorities on nesting beaches in Mexico, Nicaragua, and Costa Rica (and other countries with leatherback nesting) Adopt outreach campaigns (e.g. Yo no como huevos de tortugas in Nicaragua) to reduce egg and turtle consumption in Mexico, Nicaragua, and Costa Rica (and other countries with leatherback nesting) Consolidate and preserve nesting habitats

10 Consolidate and promote greater awareness of protected areas where leatherbacks nest Undertake or implement zoning plans for leatherback nesting areas and minimize the impact of coastal development Maintain favorable environmental conditions for hatching success Relocated nests from unfavorable areas to areas that promote higher hatching success Implement methods to maintain favorable temperatures in relocated nests Implement adaptation and mitigation measures in response to climate change impacts. Strategy 3: Promote and strengthen coordination of activities and implementation of policy action at a regional scale In many cases, sufficient information is available for specific actions to be taken at specific locations. However, to effectively implement the entirety of this Action Plan, we must take a regional approach to coordination of activities to keep sight of priorities and progress at the level of the EP leatherback population. For these reasons, we recommend strengthening regional collaboration and analyses that will provide refined targets for conservation goals (e.g., the number of turtles needed to be saved to promote population recovery, which nesting beaches need further protection, identification of high bycatch areas, vital rates such as age at first reproduction, overall population structure and size), and will harmonize regional efforts (e.g., standardization of data collection and reporting for bycatch assessments and nesting beach monitoring) Strengthen regional coordination of activities to maintain population- level priorities Develop national networks and a regional network to facilitate information exchange and harmonize activities Standardize data collection protocols and develop regional databases with common standards for bycatch and nesting beach assessments Generate a catalog of primary (> 20 nesting females per year) and secondary beaches (> 5 nesting females per year), including annual abundance and degree of protection Create regional monitoring system of hatching success and influential environmental factors (e.g., beach and nest temperatures, beach dynamics, etc.) Construct new demographic model for EP leatherbacks to determine quantified targets for levels of bycatch reduction, nesting beach protection/hatchling production, etc., necessary for population stabilization and recovery under different scenarios Facilitate identification and protection of important areas for leatherbacks and bycatch reduction Conduct and synthesize regional assessments of fisheries that interact with leatherbacks using rapid bycatch assessments and by working through existing regional instruments (e.g. Inter- American Convention for the Protection and Conservation of Sea Turtles, IAC).

11 Identification of important areas for leatherbacks toward which to focus recommendations for regional action through international policy instruments; Enhance protection efforts in existing protected areas Create alliances between international and national fisheries through RFMOs Strengthen agreements between IAC Parties and international fisheries through existing MOU between IATTC and IAC Enhance observer coverage and reporting of leatherback bycatch that is accessible to decision- makers, environment/fisheries ministers, and researchers Identify a focal point person in each country involved with the fisheries sector who can liaise with existing policy instruments Improve compliance with existing resolutions on leatherbacks and bycatch reduction Use the existing leatherback and bycatch resolutions to urge IAC Parties to enhance efforts to protect leatherbacks on nesting beaches and implement practices for safe handling and release of leatherbacks caught in fishing gear Create a working group of the IAC dedicated to evaluating compliance of Parties to existing resolutions Use existing instruments and processes to urge Parties/Signatories to regularly provide information on abundance, trends, bycatch rates, and threats impacts Coordinate an information campaign targeting decision- makers, environment and fisheries ministers at the national and RFMO scales Produce a concept paper describing the current status of leatherbacks, threats, and possible solutions that could be implemented by national and regional authorities Meet with ambassadors and government ministers to discuss the current conservation status of leatherbacks in the region Engage ministers and decision- makers to discuss current conservation status and possible solutions through existing international agreements and instruments. CONCLUSION Although not all of the actions described above will have equal, direct impacts on stabilizing and recovering leatherbacks in the East Pacific Ocean, achieving the Plan in its entirety will not only mean implementation of the highest- priority individual actions, but will also be an investment in a strong network of stakeholders whose commitment to achieving shared goals ensure successful population recovery in the long- term.

12 REFERENCES Alfaro- Shigueto J, Dutton PH, Van Bressem M- F, Mangel J (2007) Interactions between leatherback turtles and Peruvian artisanal fisheries. Chelonian Conservation and Biology 6: Alfaro- Shigueto J, Mangel JC, Bernedo F, Dutton PH, Seminoff JA, Godley BJ (2011) Small- scale fisheries of Peru: a major sink for marine turtles in the Pacific. Journal of Applied Ecology 48: Alfaro- Shigueto J, Mangel JC, Dutton PH, Seminoff JA, Godley BJ (2012) Trading information for conservation: a novel use of radio broadcasting to reduce turtle bycatch. Oryx 46: Bailey H, Benson SR, Shillinger GL, Bograd SJ, Dutton PH, Eckert SA, Morreale SJ, Paladino FV, Eguchi T, Foley DG, Block BA, Piedra R, Hitipeuw C, Tapilatu RF, Spotila JR (2012) Identification of distinct movement patterns in Pacific leatherback turtle populations influenced by ocean conditions. Ecological Applications 22: Bellagio Blueprint (2003) What can be done to restore Pacific turtle populations? The Bellagio Bluepring for Action on Pacific Sea Turtles. WorldFish Center, Malaysia. Pp 20. Santidrián Tomillo et al. (2007) Reassessment of the leatherback turtle (Dermochelys coriacea) nesting population at Parque Nacional Marino Las Baulas, Costa Rica: Effects of conservation efforts. Chelonian Conservation and Biology 6: Sarti Martínez et al. (2007) Conservation and biology of the leatherback turtle in the Mexican Pacific. Chelonian Conservation and Biology 6: Shillinger GL, Palacios DM, Bailey H, Bograd SJ, Swithenbank AM, Gaspar P, Wallace BP, Spotila JR, Paladino FV, Piedra R, Eckert SA, Block BA (2008) Persistent leatherback turtle migrations present opportunities for conservation. PLoS Biology 6(7): e171.doi: /journal.pbio Shillinger GL, Swithenbank AM, Bailey H, Bograd SJ, Castelton MR, Wallace BP, Spotila JR, Paladino FV, Piedra R, Block BA (2011) Characterization of leatherback turtle post- nesting habitats and its application to marine spatial planning. Marine Ecology Progress Series 422: Urteaga J, Torres P, Gaitan O, Rodríguez G, Dávila P (2012) Leatherback, Dermochelys coriacea, nesting beach conservation in the Pacific coast of Nicaragua ( ). In: Jones TT, Wallace BP (compilers). Proceedings of the 31 st Annual Symposium on Sea Turtle Biology and Conservation. San Diego, CA, USA. NOAA Technical Memorandum NMFS- SEFSC- 631, pp348. Wallace BP, Heppell SS, Lewison RL, Kelez S, Crowder, LB (2008) Impacts of fisheries bycatch on loggerhead turtles worldwide inferred from reproductive values analyses. Journal of Applied Ecology 45: Wallace BP, Saba VS (2009) Environmental and anthropogenic impacts on intra- specific variation in leatherback turtles: opportunities for targeted research and conservation. Endangered Species Research 7: Wallace et al. (2011) Global conservation priorities for marine turtles. PLoS ONE 6(9): e doi: /journal.pone