Spatial distribution and residency of green and loggerhead sea turtles using coastal reef habitats in southern Mozambique

Sea turtles spend the majority of their immature and adult lives in foraging grounds, yet few studies have examined their abundance and condition in these areas when compared to more accessible nesting beach habitats. Here, a 5-year dive log, photo-identification (photo-ID) and surface encounter datasets were used to investigate the abundance, individual movements and distribution of sea turtles along 40 km of coastal reefs in southern Mozambique. A generalized linear model (GLM) was constructed with turtle sightings as the response variable. Habitat type, year and day of the year, as well as underwater visibility, were significant predictors of turtle sightings. However, only 8% of the total variance was explained by the model, indicating that other variables have a significant influence on turtle movement and distribution. Photo-ID differentiated 22 individual green turtles Chelonia mydas and 42 loggerhead turtles Caretta caretta from 323 photo-ID encounters. A majority (64%) of the photos could be used to identify the individual. Although residency times of up to 1152 days were calculated for juvenile green turtles, a low overall resighting rate indicates that individual turtles either had large home ranges or were transient to the area. Surface encounter data revealed a preference for nearshore shallow waters and an increased abundance close to reef systems. Sea turtles' preferences for shallow, nearshore habitats are likely to increase the encounter risk with opportunistic and targeted artisanal fishers who catch sea turtles

Editorial: Advances in the Biology and Conservation of Marine Turtles

(First Paragraph) Marine turtles have been the subject of research over many decades, inspired by their unique life history and necessitated by their declining populations from a suite of human impacts including direct harvest, bycatch in marine fisheries, pollution, and climate change. Despite this, much about marine turtle biology has remained a mystery (Godley et al., 2008; Rees et al., 2016; Wildermann et al., 2018), but the rate of scientific discovery is increasing rapidly. As research techniques and conservation practices expand, the marine turtle research community has kept abreast of these developments and their application to marine turtles. In this special Research Topic, researchers submitted articles related to cutting-edge work in biology and conservation. The resulting 10 articles bring new insights across marine turtle movement, conservation, and methodological and analytical techniques, as well as other understudied areas and issues

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

Marine debris at nesting grounds used by the Northern Gulf of Mexico loggerhead recovery unit

Anthropogenic marine debris (AMD) can cause obstructions for nesting marine turtles and hatchlings, increase their exposure to toxicants, and potentially alter the incubating environment of clutches. Given the potential impacts of AMD on marine turtles, this study provides baseline information on the abundance and distribution of AMD at the ten highest density nesting beaches in Florida used by the Northern Gulf of Mexico Loggerhead Recovery Unit. Monitoring for AMD at nesting beaches was conducted in 2017 following protocols from the International Coastal Cleanup. AMD was present at all the nesting beaches, with the majority of AMD observed at the westernmost sites beginning with St. Joseph Peninsula State Park (363 AMD/km) with a gradual decrease of abundance to the easternmost site, Alligator Point (16 AMD/km). Plastic and foam items accounted for 92% (n = 13,566) of all AMD found

Marine reptiles

Few additional observations have been made of impacts from changes in climatic variables on marine reptiles since the first report card in 2009. However, there are a growing number of studies that have started to explore potential impacts of climate change on marine reptiles. Still, most evidence for climate change impacts on sea turtles comes from studies on loggerhead and green turtles in eastern Queensland. There is still low knowledge about vulnerability of crocodiles to climate change. However, there is more confidence that warmer water temperatures will influence behavior and possibly the distribution of the estuarine crocodile. There still is very limited knowledge of how the effects of climate change will impact sea snakes and there are no studies directly investigating this issue. What is clear, however, is that sea snakes at Ashmore Reef have undergone unprecedented local extinctions over the past ten to fifteen years and dedicated research is urgently needed into the basic biology, ecology and physiology of sea snakes to understand the causes of these declines and the extent to which the effects of climate change are driving the disappearance of sea snakes on some coral reefs

Microplastic at nesting grounds used by the northern Gulf of Mexico loggerhead recovery unit

Microplastics can impact key habitats used by endangered species, such as marine turtles. They impact the environment by transporting toxicants and altering sediment properties affecting temperature and sediment permeability. Our study determined the exposure of the ten most important nesting sites for the Northern Gulf of Mexico Loggerhead Recovery Unit to microplastic. Sand samples were obtained at each nesting site during the 2017 nesting season and analyzed for abundance and characteristics of microplastic. Microplastic was found at all sites, with an average abundance of 61.08 ± 34.61 pieces/m2, and 59.9% located at the dunes, where turtles primarily nest. A gradual decrease in microplastics abundance was observed from the most western nesting ground to the east. The results from this study indicate that microplastic accumulation on nesting sites for the Northern Gulf of Mexico may be of great concern, and could negatively affect the incubating environment for marine turtles

Exploring social resilience in Madagascar’s marine protected areas

We examined and compared aspects of local-level resilience in 13 coastal communities within and adjacent to all of Madagascar’s national marine protected areas. Our examination of social resilience focused on indicators of the flexibility of household livelihood portfolios and both formal and informal governance institutions, the capacity of communities to organize, their capacity to learn, and\ud access to household assets and community infrastructure. In general, we found high levels of flexibility in formal institutions and livelihood portfolios and high levels of participation in decision-making and community groups. Together, these indicators suggest some latent capacity to adaptively manage resources, but this capacity may be offset by poor levels of trust between communities and resource managers, a poor understanding of the ways in which humans affect marine resources, inadequate feedback of ecological\ud monitoring to communities, inflexibility in informal governance institutions, and a lack of assets to draw upon. We suggest that building desirable resilience in Madagascar’s marine protected areas will require the following: investments in community-level infrastructure, projects to generate household income, and enhanced agricultural production to improve the well-being of communities; improvements in the capacity to learn through investments in formal and informal education; enhanced trust between park staff and local communities; empowerment of communities to govern and enforce natural resources; the increased accountability of leaders and transparency of governance processes; adequate cross-scale interaction with\ud local, provincial, and national institutions; and the pursuit of these activities in ways that capitalize on\ud community-specific strengths, such as high flexibility and the presence of sociocultural institutions such as taboos that regulate resource use

Justifying the need for collaborative management of fisheries bycatch: a lesson from marine turtles in Australia

Bycatch of non-target species in commercial fisheries is a major source of anthropogenic injury and mortality for marine megafauna, including marine turtles. Their long life histories and large-scale habitat use increase the risk of interaction with multiple fleets and gear types, with consequences for population decline or collapse. However, assessment of bycatch species rarely extends beyond a single-fishery management approach, without considering the impacts of additional bycatch incurred in other fisheries. To demonstrate the need for cross-jurisdictional assessment of turtle bycatch, we evaluate the cumulative patterns of turtle bycatch in Australian commercial fisheries. We sourced logbook bycatch records from multiple fisheries in three separate management jurisdictions over the period 2000–2013. The highest bycatch per unit effort values were reported in pelagic gillnets, otter trawls and pelagic longlines. Spatial analysis revealed a bycatch 'hotspot' in the Gulf of Carpentaria, where commercial fisheries impact multiple turtle species and genetic stocks. Our results illustrate the need to set cumulative bycatch quotas for marine turtles, and to evaluate turtle bycatch at the population level instead of separately within individual fisheries. We stress the need for timely collaboration between management agencies in order to implement effective, biologically relevant management strategies for marine turtles and other vulnerable taxa

Influences Of The Local Climate On Loggerhead Hatchling Production In North Florida: Implications From Climate Change

The environment and climate in which sea turtle eggs incubate affects how successful and viable hatchlings are. Therefore, it is crucial to understand how local climate impacts sea turtle hatchling production as well as how potential changes in climate may impact future hatchling production. In this study, we investigated the effects of five climate variables at different temporal scales on loggerhead sea turtle (Caretta caretta) hatchling production from North Florida, USA. Humidity, air temperature, and accumulated precipitation were the main climatic drivers of hatchling production, while sea surface temperature and wind speed did not demonstrate to have strong effects. Climate projections show air temperatures increasing at the nesting beaches throughout the 21st century, while precipitation and humidity projections vary between sites and projection scenarios. Due to the temperate nature of these nesting beaches, increases in hatching success for nests that incubate undisturbed (not affected by depredation and storm-related impacts) are projected for this region by 2100. This study demonstrates how different climate variables and their interactions can have a determining effect on an important marine species