Habitat Use and Behavior of Multiple Species of Marine Turtles at a Foraging Area in the Northeastern Gulf of Mexico

Multi-species conservation strategies can be useful to maximize allocation of resources. To effectively plan for multi-species management practices, it is important to have a robust understanding of the variability in the spatial and behavioral ecology of sympatric species. To address this in the context of marine turtles, this study explored fine-scale habitat use by three sympatric species [juvenile green turtles (Chelonia mydas), Kemp’s ridley turtles (Lepidochelys kempii) and loggerhead turtles (Caretta caretta)] in a foraging area near Crystal River, Florida, United States. By combining sighting surveys and satellite tracking methods, we found that the distribution of the three species of marine turtles in this region overlapped both in space and time. We also observed differences in the fine-scale location of hotspots and in-water behavior among species, with some degree of apparent habitat partitioning. Habitat partitioning was particularly evident when assessing the diving and surfacing behavior of tracked turtles, with some degree of differentiation in diel diving patterns, particularly depths utilized during daytime/nighttime and the dive/surface duration. Our study provides ecological baseline data on the spatial overlap, habitat use and behavior of three sympatric marine turtle species, which can inform future management strategies at nearshore marine habitats in the Northeastern Gulf of Mexico

Records of Olive Ridley Marine Turtles (Lepidochelys olivacea Eschscholtz 1829) in Venezuelan Waters: A Review of Historical Data Sets and Threats

We assess all the records of olive ridley turtles (Lepidochelys olivacea) in an exhaustive review of multiple data sources between 1977 and 2018 in Venezuela. We compiled 35 records of olive ridleys in the country. Our findings confirm the almost year-round presence of this species in Venezuelan waters

Informing research priorities for immature sea turtles through expert elicitation

Although sea turtles have received substantial focus worldwide, research on the immature life stages is still relatively limited. The latter is of particular importance, given that a large proportion of sea turtle populations comprises immature individuals. We set out to identify knowledge gaps and identify the main barriers hindering research in this field. We analyzed the perceptions of sea turtle experts through an online survey which gathered their opinions on the current state of affairs on immature sea turtle research, including species and regions in need of further study, priority research questions, and barriers that have interfered with the advancement of research. Our gap analysis indicates that studies on immature leatherback Dermochelys coriacea and hawksbill Eretmochelys imbricata turtles are lacking, as are studies on all species based in the Indian, South Pacific, and South Atlantic Oceans. Experts also perceived that studies in population ecology, namely on survivorship and demography, and habitat use/behavior, are needed to advance the state of knowledge on immature sea turtles. Our survey findings indicate the need for more inter-disciplinary research, collaborative efforts (eg data-sharing, joint field activities), and improved communication among researchers, funding bodies, stakeholders, and decision-makers

Translating Marine Animal Tracking Data into Conservation Policy and Management

There have been efforts around the globe to track individuals of many marine species and assess their movements and distribution with the putative goal of supporting their conservation and management. Determining whether, and how, tracking data have been successfully applied to address real-world conservation issues is however difficult. Here, we compile a broad range of case studies from diverse marine taxa to show how tracking data have helped inform conservation policy and management, including reductions in fisheries bycatch and vessel strikes, and the design and administration of marine protected areas and important habitats. Using these examples, we highlight pathways through which the past and future investment in collecting animal tracking data might be better used to achieve tangible conservation benefits

Network analysis of sea turtle movements and connectivity: A tool for conservation prioritization

Aim: Understanding the spatial ecology of animal movements is a critical element in conserving long-lived, highly mobile marine species. Analyzing networks developed from movements of six sea turtle species reveals marine connectivity and can help prioritize conservation efforts. Location: Global. Methods: We collated telemetry data from 1235 individuals and reviewed the literature to determine our dataset's representativeness. We used the telemetry data to develop spatial networks at different scales to examine areas, connections, and their geographic arrangement. We used graph theory metrics to compare networks across regions and species and to identify the role of important areas and connections. Results: Relevant literature and citations for data used in this study had very little overlap. Network analysis showed that sampling effort influenced network structure, and the arrangement of areas and connections for most networks was complex. However, important areas and connections identified by graph theory metrics can be different than areas of high data density. For the global network, marine regions in the Mediterranean had high closeness, while links with high betweenness among marine regions in the South Atlantic were critical for maintaining connectivity. Comparisons among species-specific networks showed that functional connectivity was related to movement ecology, resulting in networks composed of different areas and links. Main conclusions: Network analysis identified the structure and functional connectivity of the sea turtles in our sample at multiple scales. These network characteristics could help guide the coordination of management strategies for wide-ranging animals throughout their geographic extent. Most networks had complex structures that can contribute to greater robustness but may be more difficult to manage changes when compared to simpler forms. Area-based conservation measures would benefit sea turtle populations when directed toward areas with high closeness dominating network function. Promoting seascape connectivity of links with high betweenness would decrease network vulnerability.Fil: Kot, Connie Y.. University of Duke; Estados UnidosFil: Åkesson, Susanne. Lund University; SueciaFil: Alfaro Shigueto, Joanna. Universidad Cientifica del Sur; Perú. University of Exeter; Reino Unido. Pro Delphinus; PerúFil: Amorocho Llanos, Diego Fernando. Research Center for Environmental Management and Development; ColombiaFil: Antonopoulou, Marina. Emirates Wildlife Society-world Wide Fund For Nature; Emiratos Arabes UnidosFil: Balazs, George H.. Noaa Fisheries Service; Estados UnidosFil: Baverstock, Warren R.. The Aquarium and Dubai Turtle Rehabilitation Project; Emiratos Arabes UnidosFil: Blumenthal, Janice M.. Cayman Islands Government; Islas CaimánFil: Broderick, Annette C.. University of Exeter; Reino UnidoFil: Bruno, Ignacio. Instituto Nacional de Investigaciones y Desarrollo Pesquero; ArgentinaFil: Canbolat, Ali Fuat. Hacettepe Üniversitesi; Turquía. Ecological Research Society; TurquíaFil: Casale, Paolo. Università degli Studi di Pisa; ItaliaFil: Cejudo, Daniel. Universidad de Las Palmas de Gran Canaria; EspañaFil: Coyne, Michael S.. Seaturtle.org; Estados UnidosFil: Curtice, Corrie. University of Duke; Estados UnidosFil: DeLand, Sarah. University of Duke; Estados UnidosFil: DiMatteo, Andrew. CheloniData; Estados UnidosFil: Dodge, Kara. New England Aquarium; Estados UnidosFil: Dunn, Daniel C.. University of Queensland; Australia. The University of Queensland; Australia. University of Duke; Estados UnidosFil: Esteban, Nicole. Swansea University; Reino UnidoFil: Formia, Angela. Wildlife Conservation Society; Estados UnidosFil: Fuentes, Mariana M. P. B.. Florida State University; Estados UnidosFil: Fujioka, Ei. University of Duke; Estados UnidosFil: Garnier, Julie. The Zoological Society of London; Reino UnidoFil: Godfrey, Matthew H.. North Carolina Wildlife Resources Commission; Estados UnidosFil: Godley, Brendan J.. University of Exeter; Reino UnidoFil: González Carman, Victoria. Instituto National de Investigación y Desarrollo Pesquero; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Harrison, Autumn Lynn. Smithsonian Institution; Estados UnidosFil: Hart, Catherine E.. Grupo Tortuguero de las Californias A.C; México. Investigacion, Capacitacion y Soluciones Ambientales y Sociales A.C; MéxicoFil: Hawkes, Lucy A.. University of Exeter; Reino UnidoFil: Hays, Graeme C.. Deakin University; AustraliaFil: Hill, Nicholas. The Zoological Society of London; Reino UnidoFil: Hochscheid, Sandra. Stazione Zoologica Anton Dohrn; ItaliaFil: Kaska, Yakup. Dekamer—Sea Turtle Rescue Center; Turquía. Pamukkale Üniversitesi; TurquíaFil: Levy, Yaniv. University Of Haifa; Israel. Israel Nature And Parks Authority; IsraelFil: Ley Quiñónez, César P.. Instituto Politécnico Nacional; MéxicoFil: Lockhart, Gwen G.. Virginia Aquarium Marine Science Foundation; Estados Unidos. Naval Facilities Engineering Command; Estados UnidosFil: López-Mendilaharsu, Milagros. Projeto TAMAR; BrasilFil: Luschi, Paolo. Università degli Studi di Pisa; ItaliaFil: Mangel, Jeffrey C.. University of Exeter; Reino Unido. Pro Delphinus; PerúFil: Margaritoulis, Dimitris. Archelon; GreciaFil: Maxwell, Sara M.. University of Washington; Estados UnidosFil: McClellan, Catherine M.. University of Duke; Estados UnidosFil: Metcalfe, Kristian. University of Exeter; Reino UnidoFil: Mingozzi, Antonio. Università Della Calabria; ItaliaFil: Moncada, Felix G.. Centro de Investigaciones Pesqueras; CubaFil: Nichols, Wallace J.. California Academy Of Sciences; Estados Unidos. Center For The Blue Economy And International Environmental Policy Program; Estados UnidosFil: Parker, Denise M.. Noaa Fisheries Service; Estados UnidosFil: Patel, Samir H.. Coonamessett Farm Foundation; Estados Unidos. Drexel University; Estados UnidosFil: Pilcher, Nicolas J.. Marine Research Foundation; MalasiaFil: Poulin, Sarah. University of Duke; Estados UnidosFil: Read, Andrew J.. Duke University Marine Laboratory; Estados UnidosFil: Rees, ALan F.. University of Exeter; Reino Unido. Archelon; GreciaFil: Robinson, David P.. The Aquarium and Dubai Turtle Rehabilitation Project; Emiratos Arabes UnidosFil: Robinson, Nathan J.. Fundación Oceanogràfic; EspañaFil: Sandoval-Lugo, Alejandra G.. Instituto Politécnico Nacional; MéxicoFil: Schofield, Gail. Queen Mary University of London; Reino UnidoFil: Seminoff, Jeffrey A.. Noaa National Marine Fisheries Service Southwest Regional Office; Estados UnidosFil: Seney, Erin E.. University Of Central Florida; Estados UnidosFil: Snape, Robin T. E.. University of Exeter; Reino UnidoFil: Sözbilen, Dogan. Dekamer—sea Turtle Rescue Center; Turquía. Pamukkale University; TurquíaFil: Tomás, Jesús. Institut Cavanilles de Biodiversitat I Biologia Evolutiva; EspañaFil: Varo Cruz, Nuria. Universidad de Las Palmas de Gran Canaria; España. Ads Biodiversidad; España. Instituto Canario de Ciencias Marinas; EspañaFil: Wallace, Bryan P.. University of Duke; Estados Unidos. Ecolibrium, Inc.; Estados UnidosFil: Wildermann, Natalie E.. Texas A&M University; Estados UnidosFil: Witt, Matthew J.. University of Exeter; Reino UnidoFil: Zavala Norzagaray, Alan A.. Instituto politecnico nacional; MéxicoFil: Halpin, Patrick N.. University of Duke; Estados Unido

Flatbacks at sea: understanding ecology in foraging populations

To assess the current conservation status of a species, we first need to have a good understanding of how the individuals are distributed in time and space. The latter is the focus of fields such as biogeography and conservation biogeography when applied to inform conservation decision-making. The distribution of a species will be influenced by innumerable factors, from large-scale processes such as dispersal and migration, to the local variability in environmental parameters, inter- and intra-specific interactions and ultimately the effect and intensity of natural and human-induced changes. In the marine realm, currents and wind promote connectivity among sometimes far-spread habitats. While large physical barriers are limited, the distribution of marine species is often influenced by physic-chemical barriers (i.e. thermoclines, photic zone). As a result, marine habitats tend to be highly dynamic in time and space, which in turn influences the diversity and distribution of marine species. In tropical environments and in particular in the tropical shallow waters of the Indo-West Pacific region, habitats are characterised by very high diversity of species with relatively broad geographic ranges. This is particularly true for migratory marine megafauna, such as whales and marine turtles, which can distribute across 100 to 1000s of km. Such large-scale movements pose a great challenge to monitor their movements and identify habitats used by the populations. However, the advancement of tracking technologies (i.e. acoustic and satellite tracking), animal borne-videos, accelerometers and molecular techniques such as stable isotope analysis, have enabled great advances in the understanding of marine megafauna biogeography. The general biogeography of marine turtles has been extensively studied worldwide. The distribution of nesting grounds of all marine turtle species is very well described, and while less is known on their foraging distribution and ecology, there is still an extensive body of work in this field. As migratory species, marine turtles make use of a great variety of coastal and oceanic habitats throughout their life, which vary between and among species and populations. Ontogenic, seasonal and reproductive changes in habitat use have been widely described, and are a common feature in all species. In general, biogeography of marine turtles is influenced by local and oceanic currents, distribution and abundance of prey, presence of predators, availability of shelters and seasonal shifts in water parameters (i.e. temperature). Nevertheless, improving the knowledge on biogeography of local populations, especially on the distribution of non-reproductive turtles, is still one of the global research priorities for marine turtles. In Australia, the foraging distribution and ecology of green, loggerhead and hawksbill turtles has been well described, because these species inhabit shallow coastal habitats, typically with clear water and relatively easy access for research. In contrast, knowledge on the foraging ecology of leatherback, olive ridley and flatback turtles in Australia is limited. Some aspects of the foraging ecology of leatherback and olive ridley turtles can be inferred from studies on other populations in the world, and recent advances have been published on the migration and foraging distribution for flatback turtles in Western Australia. In my thesis, I provide new and novel information on the distribution of non-reproductive flatback turtles in eastern Australia. In particular, the aim of my thesis was to improve our understanding of the biogeography and ecology of flatback turtle across different life-stages, with the intention to generate scientific information to improve the state of knowledge of the species and provide relevant outputs to inform management actions for conservation. First, in Chapter 2, I assessed a key process in understanding the biogeography of marine turtles: the early dispersal of post-hatchlings. In particular, I examined the potential mechanisms that underpins the neritic dispersal of post-hatchlings flatback turtles. Long-term records of post-hatchling flatback turtles are evidence of the neritic dispersal of the species, and studies on hatchling swimming behaviour and particle simulation have provided insights on the evolutionary adaptations of this species to turbid coastal waters. To explain the lack of oceanic dispersal of this species, I employed a hydrodynamic advection-diffusion model (called SLIM) to simulate the dispersal of virtual post-hatchlings under different scenarios of passive drift and active swimming behaviour. The results of my simulations suggest that, under the conditions I tested, the retention of flatback turtles in neritic waters of the Great Barrier Reef (GBR) depends on three main factors: (a) the location of the nesting beaches: flatback turtles nest in inshore islands and mainland of eastern Queensland; (b) the local currents, wind-driven waves and the tidal phase when post-hatchlings were released; and (c) swimming behaviour of post-hatchlings, with higher swimming effort dispersing turtles into neritic habitats of the GBR. In this chapter, I also provide future directions for research in the area of early dispersal of marine turtles, and potential approaches to test the cues that induce directional swimming in marine turtles. Next, in chapters 3 and 4, I examined two other key biogeographical processes: migration and habitat use of foraging adult turtles. Chapter 3 focused on describing the spatial distribution of 44 flatback turtles tracked with high accuracy GPS-linked satellite tags, from eight different nesting beaches to their respective foraging grounds. Home ranges of flatback turtles in eastern Australia were relatively larger than other coastal marine turtle species in the region. I also describe common patterns in the migratory and foraging strategies displayed by the tracked turtles. In this sense, flatback turtles in eastern Australia displayed direct and multi-stop migrations, and flexible and dynamic foraging behaviour (i.e. using more than one foraging ground). To supplement the understanding of the spatial ecology of foraging turtles, in Chapter 4 I further examined the distribution of the tracked turtles in relation to the environmental parameters of the seabed habitats which they inhabit. Such studies are not common in marine environments, given the challenge that represents comprehensively surveying the habitat used by individuals. However, data on the biotic (prey) and abiotic characteristics of the seabed habitats used by flatback turtles in the Great Barrier Reef were available and accessible through the GBR Seabed Biodiversity Project. Employing a Random Forest analysis, I was able to assess how the tracked turtles respond to abiotic parameters in the environment, as well as to the distribution and abundance of potential prey groups. The results confirm that flatback turtles inhabit inshore subtidal habitats, with a preference for mud-rich inshore environments. In addition, the tracked flatback turtles were associated with distribution of soft-bodied invertebrates such as sea pens and soft corals; however, flatback turtles might as well be associated with a wider variety of benthic prey than previously reported. The flexibility observed in foraging behaviour, combined with the large size of home ranges and the association of the tracked turtles to multiple habitat types and prey items suggest that flatback turtles in eastern Australia are generalist and opportunistic feeders. Nevertheless, some turtles displayed high affinity for just one of the three habitat types, which might suggest some degree of individual specialisation within the population, a hypothesis that warrants further research. Finally, in chapter 5 focused on quantifying the exposure of flatback turtles to different threats and the level of protection in their foraging habitats within the Great Barrier Reef Marine Park (GBRMP). To achieve this, I performed a spatial analysis overlapping the foraging area identified for the tracked flatback turtles (Chapter 3) with the distribution of marine protected areas, as well as with two potential threats known to occur in the GBRMP, shipping and trawling. I also considered the cumulative exposure of flatback turtles to the combined threats. The results indicate that half (52.2%) of the foraging area of the tracked turtles is within a marine protected area, 47.3% was located in "General Use" areas, and 0.5% were located within ports. In addition, the overall exposure of the tracked turtles to the individual and cumulative effect of shipping and trawling was low, with some foraging locations in the northern section of the GBRMP displaying medium exposure to the threats. I strongly suggest that future research should aim to include the synergistic effect of threats, and include other human-related stressors, such as water quality and marine debris. Overall, my thesis provides detailed and novel information which improves the knowledge base on the spatial distribution of flatback turtles in eastern Australia, including aspects on their dispersal, migratory and foraging behaviour and ecology. My thesis is relevant to several priority action areas required to maintain/recover the eastern Australia flatback stock. In this sense, I have already been able to provide copies of my data, shapefiles and written work to the GBR Marine Park Authority and the Australian Government and my data has informed the revised Marine Turtle Recovery Plan 2017. In conclusion, my study provides a comprehensive baseline on the spatial and movement ecology of flatback turtles at sea, and will hopefully provide the guidelines to address further gaps that need to be addressed to gain a better understanding of the status, vulnerability and adaptive capacity of flatbacks of the eAus stock

Informing Research Priorities For Immature Sea Turtles Through Expert Elicitation

Although sea turtles have received substantial focus worldwide, research on the immature life stages is still relatively limited. The latter is of particular importance, given that a large proportion of sea turtle populations comprises immature individuals. We set out to identify knowledge gaps and identify the main barriers hindering research in this field. We analyzed the perceptions of sea turtle experts through an online survey which gathered their opinions on the current state of affairs on immature sea turtle research, including species and regions in need of further study, priority research questions, and barriers that have interfered with the advancement of research. Our gap analysis indicates that studies on immature leatherback Dermochelys coriacea and hawksbill Eretmochelys imbricata turtles are lacking, as are studies on all species based in the Indian, South Pacific, and South Atlantic Oceans. Experts also perceived that studies in population ecology, namely on survivorship and demography, and habitat use/behavior, are needed to advance the state of knowledge on immature sea turtles. Our survey findings indicate the need for more interdisciplinary research, collaborative efforts (e.g. data-sharing, joint field activities), and improved communication among researchers, funding bodies, stakeholders, and decision-makers

Tortugas cardón (Dermochelys coriacea) en el Golfo de Venezuela: una actualizacion sobre las evaluaciones de los varamientos 2001-2014

Leatherback turtle (Dermochelys coriacea) is highly impacted by fisheries’ bycatch worldwide. This study updates and estimates the leatherback turtle stranding records from 2001 to 2014 in the Gulf of Venezuela. Eighty-seven stranded leatherback turtles were documented in the coast of the Gulf of Venezuela. Immature leatherback turtles were the most affected (85.5%) and the highest number of strandings were recorded during the dry season (56.3%). Our findings represent the minimum estimate of stranding events for the Gulf of Venezuela, especially considering the current lack of fisheries regulations. This is the latest update for the leatherback turtle strandings in the Gulf of Venezuela and could help to create new management solutions in the area aiming to minimize the impact on leatherback turtle populations in the Caribbean.La tortuga cardón (Dermochelys coriacea) está altamente impactada por las capturas incidentales a nivel global. Este estudio actualiza y calcula los registros de varamientos de la tortuga cardón desde 2001 hasta 2014 en el Golfo de Venezuela. Se contabilizaron 87 animales varados en la costa del Golfo de Venezuela. El segmento poblacional más afectado fueron los individuos inmaduros (85,5%) y el mayor número de registro de varamientos ocurrió en época de sequía (56,3%). Nuestros resultados representan el mínimo estimado de muertes por varamientos para el Golfo de Venezuela, especialmente dadas las condiciones actuales de ausencia total de regulaciones formales a las pesquerías. El presente trabajo representa la más reciente evaluación de los varamientos para esta especie en el Golfo de Venezuela, la cual podría ayudar a crear nuevas y mejores medidas de manejo en el área de trabajo, disminuyendo el impacto que afectan a las poblaciones de tortuga cardón en el Caribe

Optimising sample sizes for animal distribution analysis using tracking data

Knowledge of the spatial distribution of populations is fundamental to management plans for any species. When tracking data are used to describe distributions, it is sometimes assumed that the reported locations of individuals delineate the spatial extent of areas used by the target population. Here we examine existing approaches to validate this assumption, highlight caveats, and propose a new method for a more informative assessment of the number of tracked animals (i.e. sample size) necessary to identify distribution patterns. We show how this assessment can be achieved by considering the heterogeneous use of habitats by a target species using the probabilistic property of a utilisation distribution. Our methods are compiled in the r package SDLfilter. We illustrate and compare the protocols underlying existing and new methods using conceptual models and demonstrate an application of our approach using a large satellite tracking dataset of flatback turtles Natator depressus tagged with accurate Fastloc‐GPS tags (n = 69). Our approach has applicability for the post hoc validation of sample sizes required for the robust estimation of distribution patterns across a wide range of taxa, populations and life‐history stages of animals