1
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Ferreira‐Airaud B, Vieira S, Branco M, Pina A, Soares V, Tiwari M, Witt M, Castilho R, Teodósio A, Hawkes LA. Green and Hawksbill Sea turtles of Eastern Atlantic: New insights into a globally important rookery in the Gulf of Guinea. Ecol Evol 2024; 14:e11133. [PMID: 38505183 PMCID: PMC10948591 DOI: 10.1002/ece3.11133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 01/13/2024] [Accepted: 02/27/2024] [Indexed: 03/21/2024] Open
Abstract
Sea turtles are critical components of marine ecosystems, and their conservation is important for Ocean Governance and Global Planet Health. However, there is limited knowledge of their ecology in the Gulf of Guinea. To fill this knowledge gap, this study presents the first integrative assessment of green and hawksbill turtles in the region, combining nesting surveys over 9 years and telemetry data, to offer insights into these population dynamics, and behaviours, including nesting preferences, morphological and reproductive parameters, diving patterns and inter-nesting core-use areas. Both green and hawksbill turtles are likely making a recovery on São Tomé, potentially driven by sustained conservation efforts. There are preliminary indications of recovery, but we interpret this cautiously. Coupled with satellite tracking, this study estimated that 482 to 736 green turtles and 135 to 217 hawksbills nest on the beaches of São Tomé. Their movements overlap significantly with a proposed Marine Protected Area (MPA), which suggests they may be well placed for conservation if managed appropriately. However, the presence of artisanal fisheries and emerging threats, such as sand mining and unregulated tourism, highlight the urgent need for robust management strategies that align global conservation objectives with local socioeconomic realities. This study significantly enhances our understanding of the ecology and conservation needs of the green and hawksbill turtles in the Gulf of Guinea. The insights gleaned here can contribute to the development of tailored conservation strategies that benefit these populations and the ecosystem services upon which they depend.
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Affiliation(s)
- Betânia Ferreira‐Airaud
- Centro de Ciências do Mar (CCMAR)Universidade do AlgarveFaroPortugal
- Hatherly LaboratoriesUniversity of ExeterExeterUK
- Programa TatôSão ToméSão Tomé and Príncipe
| | - Sara Vieira
- Centro de Ciências do Mar (CCMAR)Universidade do AlgarveFaroPortugal
- Programa TatôSão ToméSão Tomé and Príncipe
| | | | | | | | - Manjula Tiwari
- Ocean Ecology NetworkResearch Affiliate of NOAA Southwest Fisheries Science CenterLa JollaCaliforniaUSA
| | - Matthew Witt
- Hatherly LaboratoriesUniversity of ExeterExeterUK
| | - Rita Castilho
- Centro de Ciências do Mar (CCMAR)Universidade do AlgarveFaroPortugal
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2
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Arendt MD, Schwenter JA, Owens DW. Climate-mediated population dynamics for the world's most endangered sea turtle species. Sci Rep 2023; 13:14444. [PMID: 37660203 PMCID: PMC10475092 DOI: 10.1038/s41598-023-41647-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Accepted: 08/29/2023] [Indexed: 09/04/2023] Open
Abstract
Restricted range, and subsequently small population size, render Kemp's ridley sea turtles (Lepidochelys kempii) the most globally endangered sea turtle species. For at least two decades preceding conservation, high egg harvest rates reduced annual cohort recruitment. Despite > 50 years of dedicated conservation, annual nest counts remain well below a landmark 1947 level. Prior studies attribute less robust than anticipated nest count rebound to multiple contemporary concerns; however, analyses herein convey optimistic interpretation. In objective 1, improved analysis of the ratio of hatchlings to nests since 1966 suggested age structure stabilization as a more likely basis for nest count trends after 2005 than density-dependent effects. In objective 2, multiple regression revealed a lagged (≤ 13 years prior) climate influence on nests (adj. r2 = 0.82) and hatchlings per nest (adj. r2 = 0.94) during 2006-2022. In objectives 3 and 4, a simulator modeled population response to changes in a suite of demographic rates including survival. Across 32 models, high survival and dynamic cohort sex ratio, sexual maturity age, and the ratio of clutch frequency to remigration interval best explained nesting trends during 1966-2022. These novel findings provide alternative perspective for evaluating species recovery criteria and in turn refine future nest trend expectations.
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Affiliation(s)
- Michael D Arendt
- South Carolina Department of Natural Resources, Marine Resources Division, 217 Fort Johnson Road, Charleston, SC, 29412, USA.
| | - Jeffrey A Schwenter
- South Carolina Department of Natural Resources, Marine Resources Division, 217 Fort Johnson Road, Charleston, SC, 29412, USA
| | - David W Owens
- College of Charleston, Grice Marine Biology Laboratory (Retired), 205 Fort Johnson Road, Charleston, SC, 29412, USA
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3
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Pereira JA, Martins AS, Seminoff JA, de Azevedo Mazzuco AC. Long-term changes in body size of green turtles nesting on Trindade Island, Brazil: Signs of recovery? MARINE ENVIRONMENTAL RESEARCH 2023; 186:105930. [PMID: 36863078 DOI: 10.1016/j.marenvres.2023.105930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 02/20/2023] [Accepted: 02/22/2023] [Indexed: 06/18/2023]
Abstract
Trindade Island is an important wildlife refuge in the South Atlantic Ocean and hosts the largest nesting population of green turtles (Chelonia mydas) in Brazil, about which temporal ecological dynamics are still not well understood. The present study examines 23 years of nesting for green turtles at this remote island to evaluate annual mean nesting size (MNS) changes and post-maturity somatic growth rates. Our results show a significant decrease in annual MNS over the study; Whereas MNS during the first three consecutively monitored years (1993-1995) was 115.1 ± 5.4 cm, during the last three years (2014-2016) it was 111.2 ± 6.3 cm. There was no significant change in post-maturity somatic growth rate over the course of the study; the mean annual growth rate was 0.25 ± 0.62 cm/year. These findings suggest an increase in the relative proportion of smaller, presumptive neophyte nesters appearing in Trindade during the study period.
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Affiliation(s)
- Josiele Alves Pereira
- Programa de Pós-Graduação em Biodiversidade Animal, Universidade Federal de Goiás, Goiânia, GO, Brazil.
| | - Agnaldo Silva Martins
- Departamento de Oceanografia e Ecologia, Universidade Federal do Espírito Santo, Espírito Santo, Brazil.
| | | | - Ana Carolina de Azevedo Mazzuco
- Grupo de Ecologia Bêntica, Departamento de Oceanografia e Ecologia, Universidade Federal do Espírito Santo, Espírito Santo, Brazil.
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4
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Del Monte-Luna P, Nakamura M, Guzmán-Hernández V, Cuevas E, López-Castro MC, Arreguín-Sánchez F. Multidecadal fluctuations in green turtle hatchling production related to climate variability. Sci Rep 2023; 13:1542. [PMID: 36707700 PMCID: PMC9883438 DOI: 10.1038/s41598-023-28574-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 01/20/2023] [Indexed: 01/28/2023] Open
Abstract
The state of Campeche, Mexico, harbors one of the largest green turtle (Chelonia mydas) rookeries of the Wider Caribbean Region. Since the 1970s, harvesting of this population was common practice, but it has since ceased, and the population is rebounding as a consequence. In this rookery, during the past 37 years (1984-2020), the positive relationship between the annual number of nesting females and the number of hatchlings they produce has revealed a long-term population signal that we postulate could be related to environmental factors. To investigate this relationship more deeply, we adopt a stock-recruitment (SR) approach, which is commonly used in fisheries. Regression analysis methods for the SR relationship, including a dynamic version of the model that incorporates the effect of sea surface temperature, show that the number of recruits produced and the number of hatchlings per unit nester were significantly and inversely correlated with a 26-year cycle of the Atlantic Multidecadal Oscillation (AMO) with a three year lag. A possible explanation for this finding is that environmental conditions during warming periods of the 26-year AMO cycle may negatively affect hatchling production by altering the nest moisture content during the incubation period, and increasing embryonic mortality, while the annual female abundance at nesting beaches may decrease due to trophic effects. The time series of abundance corresponding to other population units of green turtles as well as other species of sea turtles in the Gulf of Mexico present a similar behavior to that evaluated here, suggesting a basin-wide environmental effect.
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Affiliation(s)
- Pablo Del Monte-Luna
- Departamento de Pesquerías y Biología Marina, Instituto Politécnico Nacional, 23096, La Paz, Baja California Sur, Mexico.
| | - Miguel Nakamura
- Departamento de Probabilidad y Estadística, Centro de Investigación en Matemáticas, 36023, Guanajuato, Guanajuato, Mexico.
| | - Vicente Guzmán-Hernández
- Área de Protección de Flora y Fauna Laguna de Términos, Comisión Nacional de Áreas Naturales Protegidas, 24140, Ciudad del Carmen, Campeche, Mexico
| | - Eduardo Cuevas
- Recursos del Mar, CONACYT-Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, 97310, Mérida, Yucatán, Mexico
| | - Melania C López-Castro
- Programa para la Conservación de Tortugas Marinas, Pronatura Península de Yucatán, A.C., 97205, Mérida, Yucatán, Mexico
| | - Francisco Arreguín-Sánchez
- Departamento de Pesquerías y Biología Marina, Instituto Politécnico Nacional, 23096, La Paz, Baja California Sur, Mexico
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5
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López-Castro MC, Cuevas E, Guzmán Hernández V, Raymundo Sánchez Á, Martínez-Portugal RC, Reyes DJL, Chio JÁB. Trends in Reproductive Indicators of Green and Hawksbill Sea Turtles over a 30-Year Monitoring Period in the Southern Gulf of Mexico and Their Conservation Implications. Animals (Basel) 2022; 12:ani12233280. [PMID: 36496800 PMCID: PMC9739169 DOI: 10.3390/ani12233280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2022] [Revised: 11/21/2022] [Accepted: 11/22/2022] [Indexed: 11/27/2022] Open
Abstract
Long-term monitoring programs of species at risk are efficacious tools to assess population changes, evaluate conservation strategies, and improve management practices to ensure populations reach levels at which they can fulfill their ecological roles. For sea turtles, annual nesting beach surveys are the most accessible method to estimating the population abundance and reproductive output, especially when these are done in primary nesting sites. However, little data exist on the long-term assessment of these parameters. Here, we present the trends of the nest abundance, female size, hatching, and emergence success of hawksbill (Eretmochelys imbricata) and green (Chelonia mydas) turtles at key nesting beaches in the southern Gulf of Mexico over 31 years (from 1990 to 2021). The nest abundance showed an increasing trend in both species as a result of the sustained protection and conservation effort, but there was no significant temporal trend in the annual female size, clutch size, hatching, and emergence success. However, these indicators showed decreasing mean values over the last decade and should be closely monitored. We suggest these decreases link to the combined effects of ocean warming and anthropogenic pressures affecting the sea turtle foraging grounds. Aside from protecting key nesting sites, protecting and restoring crucial foraging habitats should be an immediate priority requiring international cooperation.
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Affiliation(s)
- Melania C. López-Castro
- Pronatura Península de Yucatán, A.C., Programa para la Conservación de la Tortuga Marina, Merida 97205, Yucatán, Mexico
- Correspondence:
| | - Eduardo Cuevas
- Departamento de Recursos del Mar, Consejo Nacional de Ciencia y Tecnología—Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional Unidad Mérida, Merida 97310, Yucatán, Mexico
| | - Vicente Guzmán Hernández
- Comisión Nacional de Áreas Naturales Protegidas, Área de Protección de Flora y Fauna Laguna de Términos, Ciudad del Carmen 24129, Campeche, Mexico
| | - Ángeles Raymundo Sánchez
- Département des Sciences du Bois et de la Forêt, Faculté de Foresterie et de Géomatique, Université Laval, Quebec, QC G1V 0A6, Canada
| | - Rosa C. Martínez-Portugal
- Comisión Nacional de Áreas Naturales Protegidas, Parque Nacional Sistema Arrecifal Veracruzano, Veracruz 91919, Veracruz, Mexico
| | - Diana J. Lira Reyes
- Pronatura Península de Yucatán, A.C., Programa para la Conservación de la Tortuga Marina, Merida 97205, Yucatán, Mexico
| | - Jorge Ángel Berzunza Chio
- Secretaría de Medio Ambiente, Biodiversidad, Cambio Climático y Energía de Campeche, Subdirección de Vida Silvestre, San Francisco de Campeche 24095, Campeche, Mexico
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6
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Hays GC, Taxonera A, Renom B, Fairweather K, Lopes A, Cozens J, Laloë JO. Changes in mean body size in an expanding population of a threatened species. Proc Biol Sci 2022; 289:20220696. [PMID: 35673864 PMCID: PMC9174726 DOI: 10.1098/rspb.2022.0696] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
With some taxa, a reduction in the mean size of individuals may reflect over-harvesting and/or trophy hunting. However, we show that in sea turtles, a reduction in the mean size of breeding individuals may be part of the good news story of an expanding population. We describe a 70-fold increase in annual nest numbers on the island of Sal (Cape Verde, North Atlantic) between 2008 and 2020 (from 506 to 35 507 nests), making this now one of the largest loggerhead (Caretta caretta) nesting aggregations in the world. We use 20 128 measurements of the size of nesting turtles to show that their mean annual size has decreased by about 2.4 cm, from 83.2 to 80.8 cm. This decrease in the mean size of nesting turtles was not caused by the removal of larger turtles, for example by selective harvesting. Rather we develop a theoretical model to show than this decrease in mean size can be explained by an influx of first-time nesters, combined with a decrease in the size of those first-time nesters over time. A reduction in mean size of nesting turtles has been reported across the Atlantic, Pacific and Indian Oceans, and may be a common feature of population recoveries in sea turtles.
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Affiliation(s)
- Graeme C. Hays
- School of Life and Environmental Sciences, Deakin University, Geelong, Victoria, Australia
| | | | - Berta Renom
- Project Biodiversity, Santa Maria, Sal, Cape Verde
| | | | - Anice Lopes
- Project Biodiversity, Santa Maria, Sal, Cape Verde
| | | | - Jacques-Olivier Laloë
- School of Life and Environmental Sciences, Deakin University, Geelong, Victoria, Australia
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7
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Benscoter AM, Smith BJ, Hart KM. Loggerhead marine turtles (
Caretta caretta
) nesting at smaller sizes than expected in the Gulf of Mexico: Implications for turtle behavior, population dynamics, and conservation. CONSERVATION SCIENCE AND PRACTICE 2021. [DOI: 10.1111/csp2.581] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Affiliation(s)
- Allison M. Benscoter
- Wetland and Aquatic Research Center U.S. Geological Survey Fort Lauderdale Florida USA
| | - Brian J. Smith
- Department of Wildland Resources and Ecology Center Utah State University Logan Utah USA
| | - Kristen M. Hart
- Wetland and Aquatic Research Center U.S. Geological Survey Fort Lauderdale Florida USA
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8
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O'Connell D, Kehl CE, Taylor BK, Piacenza J, Piacenza S, Faller Ii KJ. A computational framework for studying energetics and resource management in sea turtle migration and autonomous systems. J Theor Biol 2021; 527:110815. [PMID: 34166710 DOI: 10.1016/j.jtbi.2021.110815] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 06/10/2021] [Accepted: 06/15/2021] [Indexed: 11/18/2022]
Abstract
Sea turtles complete migrations across vast distances, covering entire ocean basins. To track these migrations, satellite tracking tags are attached to their shells. The impact of these tags must be considered to ensure that turtles' natural behavior is not artificially and adversely impacted through tag-related drag, and that the data collected by a small sample of sea turtles accurately represents the larger population. Additionally, it can be difficult to study animal energetics in the field over large migration distances. In this work, we modify a computational behavior model to study how satellite tracking tags affect turtle migration behavior. Our agent based model contains synthetic magnetic field environments that are used for navigation cues, an ocean current, resource distributions that represent locations of food, and an agent that attempts to migrate to several different goals. The agent loses energy as it progresses, and searches for the resource distributions to replenish itself. Our novel simulation framework demonstrates the relationship between an agent's available energy capacity, its energy consumption based on mechanical power expended, and its ability to navigate to all migratory goal points. This study can be utilized to (1) probe the impacts of an animal's energy capacity and foraging behavior on its resulting navigation and ecology, (2) guide future satellite tag designs, and (3) develop usage recommendations for a suitable tracking tag based on the type of experiment being conducted. Our model can be expanded beyond sea turtles to study other marine species (e.g., sharks, whales). Additionally, this model could be expanded to other domains within the marine environment. For example, it could be modified to examine design trade-offs in remotely operated vehicles (ROVs), which share many of the same operational constraints as sea turtles and other migratory species.
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Affiliation(s)
- Delaney O'Connell
- Department of Biology, The University of North Carolina, Chapel Hill, United States.
| | - Catherine E Kehl
- Department of Biology, The University of North Carolina, Chapel Hill, United States.
| | - Brian K Taylor
- Department of Biology, The University of North Carolina, Chapel Hill, United States
| | - Joseph Piacenza
- Department of Mechanical Engineering, The University of West Florida, United States.
| | - Susan Piacenza
- Department of Biology, The University of West Florida, United States.
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9
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White JW, Yamane MT, Nickols KJ, Caselle JE. Analysis of fish population size distributions confirms cessation of fishing in marine protected areas. Conserv Lett 2020. [DOI: 10.1111/conl.12775] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Affiliation(s)
- J. Wilson White
- Department of Fisheries and Wildlife, Coastal Oregon Marine Experiment Station Oregon State University Newport Oregon USA
| | - Mark T. Yamane
- Department of Fisheries and Wildlife, Coastal Oregon Marine Experiment Station Oregon State University Newport Oregon USA
- Department of Marine Science Eckerd College St. Petersburg Florida USA
| | - Kerry J. Nickols
- Department of Biology California State University Northridge California USA
| | - Jennifer E. Caselle
- Marine Science Institute University of California Santa Barbara California USA
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10
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Duarte CM, Agusti S, Barbier E, Britten GL, Castilla JC, Gattuso JP, Fulweiler RW, Hughes TP, Knowlton N, Lovelock CE, Lotze HK, Predragovic M, Poloczanska E, Roberts C, Worm B. Rebuilding marine life. Nature 2020; 580:39-51. [DOI: 10.1038/s41586-020-2146-7] [Citation(s) in RCA: 332] [Impact Index Per Article: 83.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Accepted: 02/18/2020] [Indexed: 11/09/2022]
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11
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Casale P, Ceriani SA. Sea turtle populations are overestimated worldwide from remigration intervals: correction for bias. ENDANGER SPECIES RES 2020. [DOI: 10.3354/esr01019] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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12
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Piacenza SE, Richards PM, Heppell SS. Fathoming sea turtles: monitoring strategy evaluation to improve conservation status assessments. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2019; 29:e01942. [PMID: 31267602 PMCID: PMC6851787 DOI: 10.1002/eap.1942] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Revised: 04/18/2019] [Accepted: 04/23/2019] [Indexed: 06/09/2023]
Abstract
Population monitoring must be accurate and reliable to correctly classify population status. For sea turtles, nesting beach surveys are often the only population-level surveys that are accessible. However, process and observation errors, compounded by delayed maturity, obscure the relationship between trends on the nesting beach and the population. We present a simulation-based tool, monitoring strategy evaluation (MoSE), to test the relationships between monitoring data and assessment accuracy, using green sea turtles, Chelonia mydas, as a case study. To explore this first application of MoSE, we apply different treatments of population impacts to virtual true populations, and sample the nests or nesters, with observation error, to test if the observation data can be used to diagnose population status accurately. Based on the observed data, we examine population trend and compare it to the known values from the operating model. We ran a series of scenarios including harvest impacts, cyclical breeding probability, and sampling biases, to see how these factors impact accuracy in estimating population trend. We explored the necessary duration of monitoring for accurate trend estimation and the probability of a false trend diagnosis. Our results suggest that disturbance type and severity can have important and persistent effects on the accuracy of population assessments drawn from monitoring nesting beaches. The underlying population phase, age classes disturbed, and impact severity influenced the accuracy of estimating population trend. At least 10 yr of monitoring data is necessary to estimate population trend accurately, and >20 yr if juvenile age classes were disturbed and the population is recovering. In general, there is a greater probability of making a false positive trend diagnosis than a false negative, but this depends on impact type and severity, population phase, and sampling duration. Improving detection rates to 90% does little to lower probability of a false trend diagnosis with shorter monitoring spans. Altogether, monitoring strategies for specific populations may be tailored based on the impact history, population phase, and environmental drivers. The MoSE is an important framework for analysis through simulation that can comprehensively test population assessments for accuracy and inform policy recommendations regarding the best monitoring strategies.
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Affiliation(s)
- Susan E. Piacenza
- Department of Fisheries and WildlifeOregon State UniversityCorvallisOregon97330USA
- Present address:
Department of BiologyUniversity of West FloridaPensacolaFlorida32514USA
| | - Paul M. Richards
- NOAA NMFS, Southeast Fisheries Science CenterMiamiFlorida33149USA
| | - Selina S. Heppell
- Department of Fisheries and WildlifeOregon State UniversityCorvallisOregon97330USA
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13
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Phylogeny, biogeography and methodology: a meta-analytic perspective on heterogeneity in adult marine turtle survival rates. Sci Rep 2018; 8:5852. [PMID: 29643352 PMCID: PMC5895625 DOI: 10.1038/s41598-018-24262-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Accepted: 03/28/2018] [Indexed: 11/09/2022] Open
Abstract
Comparative syntheses of key demographic parameters are critical not only for identifying data gaps, but also for evaluating sources of heterogeneity among estimates. Because demographic studies frequently exhibit heterogeneity, evaluating sources of heterogeneity among estimates can inform biological patterns and conservation actions more broadly. To better understand adult survival in marine turtles and avoid drawing inaccurate conclusions from current estimates, we conducted a comprehensive meta-analysis to test how heterogeneity among estimates was partitioned among phylogenetic, biogeographic and methodological factors. Fifty-nine studies from five marine turtle species met the minimum selection criteria for inclusion in our meta-analysis. Heterogeneity among survival estimates was first partitioned between differences in ocean basin (Indo-Pacific versus Atlantic), then by differences among family/tribe within the Indo-Pacific (Chelonini versus Carettini and Dermochelidae). However, apparent differences attributed to biogeography (ocean basin effect) and phylogeny (family/tribe effect) were highly correlated with methodological differences in tag type, model type, habitat type and study duration, thereby confounding biological interpretations and complicating efforts to use many current survival estimates in population assessments. Our results highlight the importance of evaluating sources of heterogeneity when interpreting patterns among similar demographic studies and directly inform efforts to identify research priorities for marine turtles globally.
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14
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Sykora-Bodie ST, Bezy V, Johnston DW, Newton E, Lohmann KJ. Quantifying Nearshore Sea Turtle Densities: Applications of Unmanned Aerial Systems for Population Assessments. Sci Rep 2017; 7:17690. [PMID: 29255157 PMCID: PMC5735099 DOI: 10.1038/s41598-017-17719-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 11/29/2017] [Indexed: 11/12/2022] Open
Abstract
Although sea turtles face significant pressure from human activities, some populations are recovering due to conservation programs, bans on the trade of turtle products, and reductions in bycatch. While these trends are encouraging, the status of many populations remains unknown and scientific monitoring is needed to inform conservation and management decisions. To address these gaps, this study presents methods for using unmanned aerial systems (UAS) to conduct population assessments. Using a fixed-wing UAS and a modified strip-transect method, we conducted aerial surveys along a three-kilometer track line at Ostional, Costa Rica during a mass-nesting event of olive ridley turtles (Lepidochelys olivacea). We visually assessed images collected during six transects for sea turtle presence, resulting in 682 certain detections. A cumulative total of 1091 certain and probable turtles were detected in the collected imagery. Using these data, we calculate estimates of sea turtle density (km-2) in nearshore waters. After adjusting for both availability and perception biases, we developed a low-end estimate of 1299 ± 458 and a high-end estimate of 2086 ± 803 turtles per km-2. This pilot study illustrates how UAS can be used to conduct robust, safe, and cost-effective population assessments of sea turtle populations in coastal marine ecosystems.
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Affiliation(s)
- Seth T Sykora-Bodie
- Duke University Marine Laboratory, Nicholas School of the Environment, 135 Duke Marine Lab Road, Beaufort, North Carolina, 28516, USA.
| | - Vanessa Bezy
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599, USA
| | - David W Johnston
- Duke University Marine Laboratory, Nicholas School of the Environment, 135 Duke Marine Lab Road, Beaufort, North Carolina, 28516, USA
| | - Everette Newton
- Duke University Marine Laboratory, Nicholas School of the Environment, 135 Duke Marine Lab Road, Beaufort, North Carolina, 28516, USA
| | - Kenneth J Lohmann
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599, USA
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15
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Warden ML, Haas HL, Richards PM, Rose KA, Hatch JM. Monitoring trends in sea turtle populations: walk or fly? ENDANGER SPECIES RES 2017. [DOI: 10.3354/esr00855] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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16
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Mazaris AD, Schofield G, Gkazinou C, Almpanidou V, Hays GC. Global sea turtle conservation successes. SCIENCE ADVANCES 2017; 3:e1600730. [PMID: 28948215 PMCID: PMC5606703 DOI: 10.1126/sciadv.1600730] [Citation(s) in RCA: 105] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Accepted: 08/24/2017] [Indexed: 05/19/2023]
Abstract
We document a tendency for published estimates of population size in sea turtles to be increasing rather than decreasing across the globe. To examine the population status of the seven species of sea turtle globally, we obtained 299 time series of annual nesting abundance with a total of 4417 annual estimates. The time series ranged in length from 6 to 47 years (mean, 16.2 years). When levels of abundance were summed within regional management units (RMUs) for each species, there were upward trends in 12 RMUs versus downward trends in 5 RMUs. This prevalence of more upward than downward trends was also evident in the individual time series, where we found 95 significant increases in abundance and 35 significant decreases. Adding to this encouraging news for sea turtle conservation, we show that even small sea turtle populations have the capacity to recover, that is, Allee effects appear unimportant. Positive trends in abundance are likely linked to the effective protection of eggs and nesting females, as well as reduced bycatch. However, conservation concerns remain, such as the decline in leatherback turtles in the Eastern and Western Pacific. Furthermore, we also show that, often, time series are too short to identify trends in abundance. Our findings highlight the importance of continued conservation and monitoring efforts that underpin this global conservation success story.
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Affiliation(s)
- Antonios D. Mazaris
- Department of Ecology, School of Biology, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
| | - Gail Schofield
- Department of Ecology, School of Biology, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Geelong, Victoria 3280, Australia
| | - Chrysoula Gkazinou
- Department of Ecology, School of Biology, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
| | - Vasiliki Almpanidou
- Department of Ecology, School of Biology, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
| | - Graeme C. Hays
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Geelong, Victoria 3280, Australia
- Corresponding author.
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Piacenza SE, Richards PM, Heppell SS. An agent-based model to evaluate recovery times and monitoring strategies to increase accuracy of sea turtle population assessments. Ecol Modell 2017. [DOI: 10.1016/j.ecolmodel.2017.05.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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The value of long-term, community-based monitoring of marine turtle nesting: a study in the Lamu archipelago, Kenya. ORYX 2017. [DOI: 10.1017/s0030605317000771] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
AbstractMonitoring of nesting beaches is often the only feasible and low-cost approach for assessing sea turtle populations. We investigated spatio-temporal patterns of sea turtle nesting activity monitored over 17 successive years in the Lamu archipelago, Kenya. Community-based patrols were conducted on 26 stretches of beach clustered in five major locations. A total of 2,021 nests were recorded: 1,971 (97.5%) green turtleChelonia mydasnests, 31 (1.5%) hawksbillEretmochelys imbricatanests, 8 (0.4%) olive ridleyLepidochelys olivaceanests and 11 (0.5%) unidentified nests. Nesting occurred year-round, increasing during March–July, when 74% of nests were recorded. A stable trend in mean annual nesting densities was observed in all locations. Mean clutch sizes were 117.7 ± SE 1 eggs (range 20–189) for green turtles, 103±SE 6 eggs (range 37–150) for hawksbill turtles, and 103±SE 6 eggs (range 80–133) for olive ridley turtles. Curved carapace length for green turtles was 65–125 cm, and mean annual incubation duration was 55.5±SE 0.05 days. The mean incubation duration for green turtle nests differed significantly between months and seasons but not locations. The hatching success (pooled data) was 81.3% (n = 1,841) and was higher for in situ nests (81.0±SE 1.5%) compared to relocated nests (77.8±SE 1.4%). The results highlight the important contribution of community-based monitoring in Kenya to sustaining the sea turtle populations of the Western Indian Ocean region.
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