Resident areas and migrations of female green turtles nesting at Buck Island Reef National Monument, St. Croix, US Virgin Islands (original) (raw)
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Animal Biotelemetry
Background A better understanding of sea turtle spatial ecology is critical for the continued conservation of imperiled sea turtles and their habitats. For resource managers to develop the most effective conservation strategies, it is especially important to examine how turtles use and select for habitats within their developmental foraging grounds. Here, we examine the space use and relative habitat selection of immature green turtles (Chelonia mydas) using acoustic telemetry within the marine protected area, Buck Island Reef National Monument (BIRNM), St. Croix, United States Virgin Islands. Results Space use by turtles was concentrated on the southern side of Buck Island, but also extended to the northeast and northwest areas of the island, as indicated by minimum convex polygons (MCPs) and 99%, 95%, and 50% kernel density estimations (KDEs). On average space use for all categories was
Marine Ecology Progress Series, 2016
Home range analysis is a powerful tool for identifying priority areas for conservation, but estimating the home range for many species is still challenging. In particular, highly mobile species may use different areas at different times (e.g. summer or winter), so temporally biased location data may only partially represent their home range. We investigated the temporal patterns in habitat use of green turtles Chelonia mydas (n = 52) and loggerhead turtles Caretta caretta (n = 20) at longer (>1 yr) and shorter (<1 yr) scales. The study was conducted in subtropical and tropical foraging habitats along the Queensland coast of Australia between 1991 and 2015. Each turtle was tracked by a satellite-linked tag for the effective life of the device; 3 turtles were tracked twice. Mark−recapture studies were also conducted intermittently. Single satellite-tag deployments confirmed site fidelity to a foraging habitat for up to 2.5 yr in green turtles and 2.7 yr in loggerhead turtles. Further, combining satellite telemetry and mark−recapture records indicated much longer periods of foraging residency, up to 17 yr for green turtles and 23 yr for loggerhead turtles. No tracked turtles made substantial changes in their foraging range between years. Within the long-term home range, subtropical turtles tended to shift their foraging areas seasonally. Consequently, for many turtles, the existing conservation legislation provided protection in some seasons but not others. Our results emphasise the importance of protecting areas according to the turtles' use of space, with careful consideration given to identify temporal trends in their habitat selection.
In México, nest relocation is the most commonly accepted methodology of sea turtle conservation. However, due to the heightened level of manipulation, lack of proper training for volunteer monitoring groups, and limited regulation, the shift is for more in-situ nest monitoring. Especially is the case for olive Ridley species (Lepidochelys olivacea) which is the least endangered of all marine turtle species. Yet in-situ nest monitoring is complicated by (1) poaching, (2) dynamic Pacific coastline, (3) extreme seasonal erosion from tropical storms, (4) an onslaught of unregulated coastal developments and (5) high-impact beach activities such as ATV tours.
Abundance and Distribution of Sea Turtles at Buck Island Reef National Monument, St. Croix
Abundance and Distribution of Sea Turtles at Buck Island Reef National Monument, St. Croix, USVI Sea turtles, such as green (Chelonia mydas) and hawksbill (Eretmochelys imbricata) turtle are critically endangered due to a variety of anthropogenic impacts. Monitoring the abundance and distribution of sea turtles within the marine environment greatly enhances population assessments and a network of established in-water monitoring sites can provide critical data for conservation management on a regional scale. In this study we conduct in-water surveys to generate baseline, effort corrected estimates of sea turtle abundance at Buck Island Reef National Monument and also relate those estimates to the distribution of major benthic components at our study site. We divided the study site into 18 survey blocks each approximately 0.16 km 2 (range: 0.14 to 0.21 km2, for a total of 2.85 km 2) and determined the average percent cover for a variety of benthic components within each survey block. Sea turtle surveys were then conducted by 2-5 snorkelers in May-June 2012 and data on the species, size class and GPS location of each sea turtle sighting were recorded. Afterwards we calculated the number of sightings per survey effort or "catch per unit effort" (CPUE) and compared those values between the different survey blocks. Using the spearman's rank coefficient we correlated sea turtle CPUE with the average percent cover per survey block for each benthic variable. During a total of 37.8 survey hours (113.8 observer hrs) there were 132 sea turtle sightings including 100 green and 32 hawksbill turtles. Most of the sightings occurred in survey blocks located along the southern forereef and the majority of sightings were of juvenile and sub-adult turtles. For adult green turtles CPUE was positively correlated to seagrass cover (Spearman p = 0.6918; Prob > I p I = 0.0015) and negatively correlated with algae, cyanobacteria, other invertebrates, and rugosity (Spearman p = -0.5876; Prob > I p1 = 0.0103), (Spearman p = -0.5515; Prob > I p1 = 0.0177), (Spearman p = -0.5016; Prob > I p I = 0.0339), (Spearman p = -0.484; Prob > I p I = 0.0418). Juvenile green turtle CPUE was not correlated with any of the benthic variables investigated. Hawksbill turtle CPUE (for all size classes) was not correlated with any of the benthic variables investigated. This study establishes site specific estimates of relative abundance and distribution at Buck Island Reef National Monument and provides survey design and analyses techniques that can be utilized by other conservation managers.
Conservation hotspots for marine turtle nesting in the United States based on coastal development
Coastal areas provide nesting habitat for marine turtles that is critical for the persistence of their populations. However, many coastal areas are highly affected by coastal development, which affects the reproductive success of marine turtles. Knowing the extent to which nesting areas are exposed to these threats is essential to guide management initiatives. This information is particularly important for coastal areas with both high nesting density and dense human development, a combination that is common in the United States. We assessed the extent to which nesting areas of the loggerhead (Caretta caretta), the green (Chelonia mydas), the Kemp's ridley (Lepidochelys kempii), and leatherback turtles (Dermochelys coria-cea) in the continental United States are exposed to coastal development and identified conservation hotspots that currently have high reproductive importance and either face high exposure to coastal development (needing intervention), or have low exposure to coastal development, and are good candidates for continued and future protection. Night-time light, housing, and population density were used as proxies for coastal development and human disturbance. About 81.6% of nesting areas were exposed to housing and human population, and 97.8% were exposed to light pollution. Further, most (>65%) of the very high-and high-density nesting areas for each species/subpopulation, except for the Kemp's ridley, were exposed to coastal development. Forty-nine nesting sites were selected as conservation hotspots; of those high-density nesting sites, 49% were sites with no/low exposure to coastal development and the other 51% were exposed to high-density coastal development. Conservation strategies need to account for ~66.8% of all marine turtle nesting areas being on private land and for nesting sites being exposed to large numbers of seasonal residents.
Sea Turtle Nesting Habitat Assessment: A Rapid, Integrated, Technological Approach
Rock Eagle (GA; USA) Proceedings (Electronic), 1999
A rapid assessment technique for assigning quantative values to loggerhead sea turtle nesting habitat on the Georgia coast has been developed using experience gained on St. Catherines Island. Habitat photographs are presented leading to recognition of erosional and depositional habitats. Habitat parameters are scored on a beach grid on a scale of 1-5 generating a quantatative assessment of the habitat allowing temporal comparison of each area and comparision of areas. Technology allows rapid development of ideas and procedures. Computer-based graphics, including digital images, are used to illustrate word processed text as the concepts are developed eventaully leading to a completed paper-based document suitable for distribution to colleagues as a publication. The learning cycle is extended for colleagues by paper-based publication and by uploading edited copy onto the web for rapid and timely distribution. Note: Habitats utilized by nesting loggerhead sea turtles on St. Catherines Island are described. Electronic Copy
Frontiers in Marine Science, 2020
Marine turtles are of conservation concern throughout their range, with past population declines largely due to exploitation through both legal and illegal take, and incidental capture in fisheries. Whilst much research effort has been focused on nesting beaches and elaborating migratory corridors, these species spend the vast majority of their lifecycle in foraging grounds, which are, in some species, quite discrete. To understand and manage these populations, empirical data are needed on distribution, space-use, and habitats to best inform design of protective measures. Here we describe space-use, occupancy, and wide-ranging movements derived from conventional flipper tagging and satellite tracking of sub-adult green turtles (Chelonia mydas) within the coastal waters of the Turks and Caicos Islands (TCI; 2011-2017). 623 turtles were fitted with flipper tags, with 69 subsequently recaptured, five of which in international waters. Sixteen individual turtles of between 63 and 81 cm curved carapace length were satellite tracked for a mean 226 days (range: 38-496). Data revealed extended periods of occupancy in the shallow coastal waters within a RAMSAR protected area. Satellite tracking and flipper tagging showed wide-ranging movements, with flipper tag recaptures occurring in waters off Nicaragua (n = 4), and Venezuela (n = 1). Also, four of 16 satellite tracked turtles exhibiting directed movements away (displaced >450 km) from TCI waters traveling through nine geo-political zones within the Caribbean-Atlantic basin, as well as on the High Seas. One turtle traveled to the Central American coast before settling on inshore habitat in Colombia's waters for 162 days before transmission ceased, indicating ontogenetic dispersal to a distant foraging habitat. These data highlight connectivity throughout the region, displaying key linkages between countries that have previously only been linked by genetic evidence. This study also provides evidence of the importance of the Turks and Caicos Islands marine protected area network and importance of effective management of the sea turtle fishery for regional green turtle populations.
Background: Resolving threats to widely distributed marine megafauna requires definition of the geographic distributions of both the threats as well as the population unit(s) of interest. In turn, because individual threats can operate on varying spatial scales, their impacts can affect different segments of a population of the same species. Therefore, integration of multiple tools and techniques — including site-based monitoring, genetic analyses, mark-recapture studies and telemetry — can facilitate robust definitions of population segments at multiple biological and spatial scales to address different management and research challenges. Methodology/Principal Findings: To address these issues for marine turtles, we collated all available studies on marine turtle biogeography, including nesting sites, population abundances and trends, population genetics, and satellite telemetry. We georeferenced this information to generate separate layers for nesting sites, genetic stocks, and co...