Strandings of marine megafauna can provide valuable information on cause of death at sea. However, as stranding probabilities are usually very low and highly variable in space and time, interpreting ...the results can be challenging. We evaluated the magnitude and distribution of at-sea mortality of marine turtles along the Pacific coast of Baja California Sur, México during 2010-11, using a combination of counting stranded animals and drifter experiments. A total of 594 carcasses were found during the study period, with loggerhead (62%) and green turtles (31%) being the most common species. 87% of the strandings occurred in the southern Gulf of Ulloa, a known hotspot of loggerhead distribution in the Eastern Pacific. While only 1.8% of the deaths could be definitively attributed to bycatch (net marks, hooks), seasonal variation in stranding frequencies closely corresponded to the main fishing seasons. Estimated stranding probabilities from drifter experiments varied among sites and trials (0.05-0.8), implying that only a fraction of dead sea turtles can be observed at beaches. Total mortality estimates for 15-day periods around the floater trials were highest for PSL, a beach in the southern Gulf of Ulloa, ranging between 11 sea turtles in October 2011 to 107 in August 2010. Loggerhead turtles were the most numerous, followed by green and olive ridley turtles. Our study showed that drifter trials combined with beach monitoring can provide estimates for death at sea to measure the impact of small-scale fisheries that are notoriously difficult to monitor for by-catch. We also provided recommendations to improve the precision of the mortality estimates for future studies and highlight the importance of estimating impacts of small-scale fisheries on marine megafauna.
The expansion of cocoa farming has been linked to deforestation and biodiversity loss in West Africa. Agroforestry systems could potentially increase the sustainability of cocoa production. However, ...despite the long history of cocoa cultivation in agroforestry systems, the exact mechanism or the combination of factors that drive cocoa growth and yield in these agroecosystems, especially at the cocoa establishment stage, is unclear.
The present study aims to analyse how resource availability, stand characteristics and cocoa tree morphology interact to determine the performance of cocoa during the establishment phase among different cocoa cultivation systems.
We studied seven different agroforestry systems and one monoculture system in 53 plots located in a 12-ha cocoa agroforestry trial recently established in Côte d'Ivoire. We characterized each system with 16 variables that described five system components: 1) cocoa yield (number of pods, pods weight, number of productive trees) and cocoa growth (basal diameter), 2) cocoa tree morphology (crown depth, diameter, area, and volume), 3) stand characteristics (number and size of shade trees), 4) light (leaf area index) and 5) water (soil volumetric water content). We used a Structural Equation Modelling (SEM) approach to understand and quantify interactions between the five components.
The models were able to largely explain cocoa early yield and juvenile growth variability (respective determination coefficients: 0.45 and 0.92). We observed improved cocoa establishment in certain designs of agroforestry systems compared with monoculture. However, SEM revealed that stand characteristics (i.e. increase in the number and height of shade trees) had a negative effect on cocoa yield and growth via changes in cocoa tree morphology, having path coefficients of −0.48 and − 0.72, respectively. Conversely, we found a positive relationship between the cocoa tree morphology and cocoa early yield, for which the path coefficient was 0.74, the strongest relation. Cocoa tree morphology was more important than stand characteristics, leaf area index, and soil volumetric water content in controlling cocoa yield and growth. Taken together, our results suggest a competition for space between shade trees and cocoa plants. Finding the optimal design of agroforestry systems can help enhance cocoa establishment in the first years, improving the long-term performance of the system.
This finding suggests that the competition effect depends on spatial planting pattern and species composition, offering an opportunity to meet the goals of a sustainable intensification of cocoa plantations through the design and management of optimal agroforestry systems.
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•Cocoa yield and growth in the establishment phase are the result of interactions between the stand characteristics and cocoa crown development.•The competition for space in dense systems make the benefits of shade trees relatively unimportant.•Adequate agroforests design and management can enhance cocoa early yield and growth via an enhancement of crown development.
Sea turtles can bioaccumulate high concentrations of potentially toxic contaminants. To better understand trace element effects on sea turtles' health, we established reference intervals for ...hematological and plasma biochemical analytes in 40 in-water, foraging immature and adult Eastern Pacific green turtles (Chelonia mydas) from two coastal lagoons in Baja California Sur, quantified whole blood concentrations of eight trace elements, and assessed their correlations. Rank-order trace element concentrations in both immature and adult turtles was zinc > selenium > nickel > arsenic > copper > cadmium > lead > manganese. Immature turtles had significantly higher copper and lower nickel and zinc concentrations. Additionally, a number of relationships between trace elements and blood analytes were identified. These data provide baseline information useful for future investigations into this population, or in other geographic regions and various life-stage classes.
•Blood analytes and trace elements were quantified in Eastern Pacific green turtles.•Reference intervals for blood analytes were established for each life-stage class.•Life-stage classes analyte differences were attributed to diet and somatic growth.•Immature turtles presented higher copper and lower nickel and zinc concentrations.•A number of relationships between trace elements and blood analytes were identified.
Estimating population abundance of marine turtles on their feeding grounds is needed to implement effective conservation strategies, but is logistically challenging. In-water monitoring surveys on ...feeding grounds are costly, time-consuming, stressful to the animals (when capture is required), and typically requires complex analytical skills. Here, we compare two sampling methods to estimate abundance of green turtles on one of their major feeding grounds in the Egyptian Red Sea: a) snorkelling strip transect counts, a rarely used method on marine turtles; and b) capture–mark–recapture (CMR) using photo-identification. The main goals of this research were to: 1) identify the most cost-effective method to estimate in-water marine turtle abundance; and 2) provide the first abundance estimates for green turtles on their feeding grounds in the Red Sea. Both methods produced an average monthly abundance of approximately 30 turtles, with no significant difference between the two methodologies. The strip-transect method presented major logistical advantages, including easy field implementation, simple equipment, and only basic analytical skills. Furthermore, this method provided density estimates that can be used as index for population trends. However, limitations of this method included intensive field effort and potentially altered turtle behaviour due to the presence of the observers. By contrast, photo-identification and CMR models provided valuable information of population demography but required advanced analytical skills, did not provide a measure of density, and could prove challenging in areas where turtles are not acclimated to human presence. Our results suggest that the ease data collection and associated analysis of the strip transect method should be considered when implementing a monitoring program of wildlife to be used for management and conservation purposes.
•We compare two sampling methods to estimate in-water abundance of green turtles.•This is the first abundance estimate of green turtles in the Egyptian Red Sea.•Photo-identification is fitted into complex models and provides information on population structure.•Snorkelling transects are a simple but reliable monitoring technique.
Abstract Fibropapillomatosis (FP) - tumour-associated chelonid alphaherpesvirus 5 (ChHV5; Scutavirus chelonidalpha5) - is a disease that affect marine turtles around the world, and characterized by ...the formation of cutaneous tumours that can appear anywhere on the body. We carried out a thorough literature search (from 1990 to 2024) in the feeding sites of North-western Mexico, a region that hosts important habitats for feeding, development, and reproduction for five of the seven existing sea turtle species. We found 18 reports recording a total of 32 cases of FP and/or ChHV5/Scutavirus chelonidalpha5 in coastal and insular areas of North-western Mexico. Baja California Sur resulted with the highest number of cases (75%). While the first case of ChHV5/Scutavirus chelonidalpha5 infection was reported in 2004, the presence of FP tumours was reported in 2014 and became more frequent between 2019 and 2024. The affected species were black, Chelonia mydas (50%), olive ridley, Lepidochelys olivacea (46.8%) and loggerhead turtles, Caretta caretta (3.2%). Tumours occurred mainly in anterior flippers (46.1%) and neck (22.5%), and most had a nodular and verrucous appearance with a rough surface. In the study region, there is a potential sign of the emergence of the ChHV5/Scutavirus chelonidalpha5 infections and FP disease during the last 20 years, with a rapid increase during the last 10 years. As long as infections by ChHV5/Scutavirus chelonidalpha5 and the prevalence of the FP disease may be potentially influenced by anthropogenic activities, a One Health approach is needed to understand and improve sea turtles’ health.
Conventional maize-after-maize in the UK is frequently associated with soil compaction, runoff and soil erosion, due to a late autumn harvest and a post-harvest management that leaves minimal soil ...protection. Consequently, maize cultivation leads to on-site soil degradation and off-site environmental pollution. Soil conservation practices such as cover cropping could improve the sustainability of maize. Two field experiments were established within commercially grown maize (Herefordshire) in two consecutive years to investigate the role of different species of cover crops in reducing runoff, preventing soil erosion and enhancing soil microbial community. Experiment 1 compared common non-cover crop post-harvest managements with Lolium multiflorum and Secale cereale. Experiment 2 compared Lolium multiflorum and the mixtures Lolium multiflorum & Vicia villosa and Lolium multiflorum & Trifolium alexandrinum with the traditional method of post-harvest wintered maize stubbles without cover crops. Runoff and soil loss were monitored using enclosed erosion plots periodically sampled. Soil was tested for chemical parameters such as organic matter, organic carbon, total nitrogen, available phosphorus, and biological parameters such as microbial and fungal biomass, phospholipid fatty acid analysis and multiple substrates induced respiration. Additionally, during Experiment 2 easily available glomalin related soil proteins and aggregate stability were measured. Results showed a trend in the reduction of runoff and soil erosion. However, no significant differences were recorded. Overall, the impact of cover crops on soil microbiology was limited. Cover crops had a priming effect during Experiment 1 that led to a reduction of organic matter and organic carbon due to microbial activity. In Experiment 2 the relative abundance of fungi increased in the cover crop treatments. This was possibly due to the decrease of easily available nutrients and the increase of plant root debris, which are more available to fungi rather than bacteria. Cover crops seemed a practical option to improve the sustainability of maize production due to lack of an adverse impact on maize yield and the encouraging results on runoff, soil erosion and soil fungi. However, the effects were limited and further investigation is needed to prove the impact of cover crops in the long-term.
We examined sea turtle consumption and illegal trade in Baja California Sur (BCS) using data from (1) bimonthly surveys at beaches, fishing camps and dumpsites and (2) semi-structured interviews with ...fishermen. From March 2006 to February 2008, we found the carcasses of 1014 sea turtles; the meat of 461 of these turtles (45.5%) had been consumed. The East Pacific green turtle Chelonia mydas was the most sought-after species (77% of total consumed turtles). Consumption is still the main cause of mortality for sea turtles and the greatest threat to them in BCS, affecting mostly juvenile-sized specimens. Sea turtle consumption occurred all year round with a lower number recorded from November to February and an increase thereafter. From 151 interviews we identified 3 areas where turtle meat is consumed but not sold, 4 areas with a local black market and 3 areas providing for a regional and/or international black market. Prices vary from 2-5 USD kg super(-1) (entire turtle sold on the beach) to 4-20 USD kg super(-1) (meat only). Consumption of sea turtle meat is partly related to cultural factors, as it is consumed more frequently during the Christian fasting period of Lent. While trade and consumption have decreased in recent years, there are still several places that supply sea turtle meat to local, regional, and sometimes even international markets. Authority involvement in sea turtle traffic and the lack of law enforcement need to be addressed to improve sea turtle conservation in the region. The use of both qualitative and quantitative data in the present study has helped to gain a better understanding of sea turtle consumption in BCS.
Sea turtles are an iconic group of marine megafauna that have been exposed to multiple anthropogenic threats across their different life stages, especially in the past decades. This has resulted in ...population declines, and consequently many sea turtle populations are now classified as threatened or endangered globally. Although some populations of sea turtles worldwide are showing early signs of recovery, many still face fundamental threats. This is problematic since sea turtles have important ecological roles. To encourage informed conservation planning and direct future research, we surveyed experts to identify the key contemporary threats (climate change, direct take, fisheries, pollution, disease, predation, and coastal and marine development) faced by sea turtles. Using the survey results and current literature, we also outline knowledge gaps in our understanding of the impact of these threats and how targeted future research, often involving emerging technologies, could close those gaps.
The hawksbill sea turtle Eretmochelys imbricata is categorized as Critically Endangered on the IUCN Red List and its population has declined by over 80% in the last century. The Eastern Pacific ...population is one of the most threatened hawksbill populations globally. Western Mexico is the northern distribution limit for hawksbill sea turtles in the Eastern Pacific and recent research indicates that the Mexican Pacific portion of the population is a separate management unit because of the restricted movements of these turtles. Here we use the most complete database of sighting records in the north-west Pacific of Mexico to identify sites where hawksbill turtles are present. We also develop a conservation index to determine the conservation status of hawksbill turtle sites. Our results demonstrate the importance of this region for juveniles and the relevance of rocky reefs and mangrove estuaries as habitats for hawksbill turtles. We identified 52 sites with records of hawksbill turtles. Most of these sites (71%) are not protected; however, sites with high conservation value included islands and coastal sites along the Baja California peninsula that are established as marine protected areas. Reefs and mangrove estuaries relevant for hawksbill turtles are probably also significant fish nursery areas that are important for local fishing communities, creating opportunities for conservation strategies that combine science, local engagement and policy to benefit both local fishing communities and hawksbill sea turtle conservation.
Despite complete legal protection, improvements in infrastructure, and market conditions that provide easier access to other protein sources, illegal poaching of sea turtles for consumption in Baja ...California Sur (BCS), Mexico remains a major threat to their recovery. Few studies have focused on understanding the economic and social drivers behind this activity, which is fundamental to determining best practices for discouraging it. From June 2007 to April 2008 we conducted eight in-depth, semi-structured interviews with sea turtle poachers at five coastal communities in BCS to determine the drivers influencing them. The most prevalent reasons for illegal poaching were direct economic benefits, lack of law enforcement and ease of escape from or bribery of authorities, and strong family tradition. Our results suggest that to reduce illegal poaching it will be necessary to better enforce existing environmental laws, reduce social acceptance of sea turtle hunting throughout the region, educate fishers on the ecological importance of sea turtles, and show fishers direct economic benefits from non-consumptive use of sea turtles, such as ecotourism.
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