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Otolith Sr/Ca ratio complements Sr isotopes to reveal fish migration in large basins with heterogeneous geochemical landscapes
No full textThe potential use of Sr/Ca and Ba/Ca ratios in fish otolith, as a complement to Sr-87/Sr-86 to study movements of Prochilodus lineatus, was evaluated in the La Plata Basin (South America). Water ratios were obtained from samples collected during the high and low water seasons at 42 sites across the La Plata Basin. Elemental and isotopic ratios in water were measured by MC-ICP-MS, ICP-MS and ion chromatography, and obtained from available literature. Fish were caught from six different sites with different physiochemical features. Otolith core-to-edge Sr/Ca and Ba/Ca profiles were determined by LA-ICP-MS, while the otolith Sr-87/Sr-86 data set was taken from literature. The predictive classification by rivers according to water Sr/Ca, Ba/Ca and Sr-87/Sr-86 ratios (92.5%) was higher than that based solely on Sr-87/Sr-86 (58%), with classification that reached 100% for several rivers. Unlike Ba/Ca, a significant relationship (R-2 = 0.94, p < 0.05) was found between otolith edge and water Sr/Ca, suggesting that this could be an efficient movement indicator for P. lineatus. The Sr/Ca ratio complemented the information provided by Sr isotopes and it was particularly useful in the northwest basin, where the isotopes alone do not allow differentiating between large rivers
Machine learning to detect bycatch risk : novel application to echosounder buoys data in tuna purse seine fisheries
No full textThe advent of big data and machine learning offers great promise for addressing conservation and management questions in the oceans. Yet, few applications of machine learning exist to mitigate the overexploitation of marine resources. Tropical tuna purse seine fisheries (TTPSF) are distributed worldwide and account for two thirds of the global tuna catch. In these fisheries, the use of Drifting Fish Aggregating Devices (DFADs)? n-made floating objects massively deployed by fishers to increase their tuna catches?results in the incidental catch of non-target species, termed bycatch. We explored the possibility of applying machine learning on echosounder buoys attached to DFADs, representing an unprecedented source of big data, for identifying high bycatch risk at DFADs. We trained random forests algorithms to differentiate between high and low bycatch occurrence based on matched echosounder and onboard observer data for the same DFADs (representing sample sizes of 838 and 2144 in the Atlantic and the Indian Ocean, respectively). Algorithms showed a better performance in the Atlantic Ocean (accuracy of 0.66 versus 0.58 in the Indian Ocean) and were best at detecting the ?high bycatch? occurrence class. These results unravel the potential of machine learning applied to fishers? buoys data for bycatch reduction and improved selectivity in one of the largest fisheries worldwide
Perception de la COVID-19 et comportement des ménages en Argentine
No full textCet article explore les perceptions et attitudes des argentins face à l'épidémie de COVID-19 à partir d'une enquête téléphonique menée auprès d'un échantillon représentatif de 1000 répondants. L'analyse montre que les argentins ont massivement approuvé la politique sanitaire et économique suivie par leur gouvernement, et, en conséquence, modifié leur comportement. Parmi les nombreux facteurs qui ont influencé les perceptions et attitudes des argentins, la confiance dans les institutions (président, gouverneur, maire) et, dans une moindre mesure, dans la communauté médicale et scientifique ressort comme un déterminant majeur de l'adhésion des argentins à l'ensemble de la politique menée ainsi que du respect des mesures de distanciation sociale et des gestes barrière. Parmi les émotions, la peur s'avère également un puissant moteur du respect des consignes sanitaires. Les résultats soulignent enfin l'importance des mesures d'accompagnement du choc social, qui permettent de réduire les coûts associés aux comportements de précaution. Ces conclusions sont robustes à l'inclusion d'un vaste ensemble de variables de contrôle sociodémographiques telles que l'âge, le genre, le niveau d'éducation, le lieu de résidence, et le statut économique des individu
Face au changement climatique, les agricultures africaines au défi de la sécurité alimentaire
No full textPredicting the presence of leptospires in rodents from environmental indicators opens up opportunities for environmental monitoring of human leptospirosis
No full textLeptospirosis, an environmental infectious disease of bacterial origin, is the infectious disease with the highest associated mortality in Seychelles. In small island territories, the occurrence of the disease is spatially heterogeneous and a better understanding of the environmental factors that contribute to the presence of the bacteria would help implement targeted control. The present study aimed at identifying the main environmental parameters correlated with animal reservoirs distribution and Leptospira infection in order to delineate habitats with highest prevalence. We used a previously published dataset produced from a large collection of rodents trapped during the dry and wet seasons in most habitats of Mahe, the main island of Seychelles. A land use/land cover analysis was realized in order to describe the various environments using SPOT-5 images by remote sensing (object-based image analysis). At each sampling site, landscape indices were calculated and combined with other geographical parameters together with rainfall records to be used in a multivariate statistical analysis. Several environmental factors were found to be associated with the carriage of leptospires in Rattus rattus and Rattus norvegicus, namely low elevations, fragmented landscapes, the proximity of urbanized areas, an increased distance from forests and, above all, increased precipitation in the three months preceding trapping. The analysis indicated that Leptospira renal carriage could be predicted using the species identification and a description of landscape fragmentation and rainfall, with infection prevalence being positively correlated with these two environmental variables. This model may help decision makers in implementing policies affecting urban landscapes and/or in balancing conservation efforts when designing pest control strategies that should also aim at reducing human contact with Leptospira-laden rats while limiting their impact on the autochthonous fauna
Pleistocene climatic fluctuations promoted alternative evolutionary histories in Phytelephas aequatorialis, an endemic palm from western Ecuador
No full textAim: Pleistocene (2.58 Ma-11.7 ka) climatic fluctuations have shaped intraspecific genetic patterns worldwide; however, their impact on species in many regions remains unknown. In order to determine the impact of Pleistocene climatic fluctuations on the tropical rain forests of western Ecuador, we explored the evolutionary history of the endemic palm Phytelephas aequatorialis. Location: Western Ecuador, north-western South America. Taxon: Phytelephas aequatorialis (Arecaceae). Methods: One hundred and seventy-six nuclear genes were sequenced in 91 individuals for phylogenomic and population structure analyses. The time of divergence between identified genetic lineages was estimated using a coalescent phylogenomic analysis. Palaeoecological niche modelling analyses were performed to determine areas of historical climatic suitability since the Last Glacial Maximum (LGM; 22 ka) that potentially acted as forest refugia during the Pleistocene. A Wilcoxon test and Pearson correlations were used to explore how current levels of genetic diversity, in terms of expected heterozygosity (Hs), have been shaped by several palaeoclimatic and geographic factors. Results: Phylogenomic and population structure analyses revealed two main genetic lineages with a north-south distribution, which diverged 1.14 Ma during the Pleistocene. Two potential Pleistocene refugia were identified, one along the Pacific coast of Ecuador and one in the Andean foothills of south-western Ecuador. The location of these refugia agrees with the spatial location of the two genetic lineages. Within the Andean foothills, Hs was lower for the southern lineage than for the northern lineage. Hs significantly increased with decreasing latitude across the species as a whole. Main conclusions: Pleistocene climatic fluctuations promoted intraspecific divergence in P. aequatorialis within the rain forests of western Ecuador. The Andean foothills of south-western Ecuador could be an important area for rain forest evolution because they potentially remained climatically suitable throughout the Pleistocene. Lower genetic diversity in the southern lineage, which apparently remained isolated in the Andean foothills during glacial cycles, adds evidence to the presence of a forest refugium in south-western Ecuador. The geographic pattern in genetic diversity suggests that P. aequatorialis colonized western Ecuador from the north. This study supports the role of Pleistocene climatic fluctuations in promoting intraspecific divergence, and for the first time, we show their impact west of the Andes
Thiamine fortification strategies in low- and middle-income settings : a review
No full textThiamine (vitamin B-1) is an essential micronutrient in energy metabolism and cognitive and neurological health. Thiamine deficiency disorders (TDDs) have a range of clinical presentations that result in various morbidities and can be fatal if not promptly recognized and treated, especially in infants. To intervene, thiamine intakes by breastfeeding mothers and others at risk of thiamine deficiency should be increased to ensure adequate thiamine intake. Although thiamine fortification programs have a long history in high-income countries, there are few mandatory fortification programs to address TDDs in low- and middle-income countries (LMICs), particularly in the regions of greatest concern, South and Southeast Asia. This review highlights essential aspects for consideration in the development of a mandatory fortification program in LMICs, including an overview of the data required to model fortification dosing schemes, available thiamine fortificants, and potential fortification vehicles, as well as identifies current knowledge gaps
Temporal mosaicking approaches of Sentinel-2 images for extending topsoil organic carbon content mapping in croplands
No full textThe spatial assessment of soil organic carbon (SOC) is a major environmental challenge, notably for evaluating soil carbon stocks. Recent works have shown the capability of Sentinel-2 to predict SOC content over temperate agroecosystems characterized with annual crops. However, because spectral models are only applicable on bare soils, the mapping of SOC is often obtained on limited areas. A possible improvement for increasing the number of pixels on which SOC can be retrieved by inverting bare soil reflectance spectra, consists of using optical images acquired at several dates. This study compares different approaches of Sentinel-2 images temporal mosaicking to produce a composite multi-date bare soil image for predicting SOC content over agricultural topsoils. A first approach for temporal mosaicking was based on a per-pixel selection and was driven by soil surface characteristics: bare soil or dry bare soil with/without removing dry vegetation. A second approach for creating composite images was based on a per-date selection and driven either by the models performance from single date, or by average soil surface indicators of bare soil or dry bare soil. To characterize soil surface, Sentinel-1 (S1)-derived soil moisture and/or spectral indices such as normalized difference vegetation index (NDVI), Normalized Burn Ratio 2 (NBR2), bare soil index (BSI) and a soil surface moisture index (S2WI) were used either separately or in combination. This study highlighted the following results: i) none of the temporal mosaic images improved model performance for SOC prediction compared to the best single-date image; ii) of the per-pixel approaches, temporal mosaics driven by the S1-derived moisture content, and to a lesser extent, by NBR2 index, outperformed the mosaic driven by the BSI index but they did not increase the bare soil area predicted; iii) of the per-date approaches, the best trade-off between predicted area and model performance was achieved from the temporal mosaic driven by the S1-derived moisture content (R-2 similar to 0.5, RPD similar to 1.4, RMSE similar to 3.7 g.kg(-1)) which enabled to more than double (*2.44) the predicted area. This study suggests that a number of bare soil mosaics based on several indicators (moisture, bare soil, roughness...), preferably in combination, might maintain acceptable accuracies for SOC prediction whilst extending over larger areas than single-date images
Adherence to child feeding practices and child growth : a retrospective cohort analysis in Cambodia
No full textAppropriate feeding in the first 1000 days of a child's life is critical for their health and growth. We determined associations between adherence to age-appropriate feeding practices and child growth in Cambodia. Children (n = 1079) were included in the first follow-up (FU) data analyses and followed for 30 months (six FUs). Data were analyzed by generalized linear mixed-effect models. Children who adhered to feeding practices on at least three FUs, with an adequate minimal dietary diversity (MDD), a minimal acceptable diet (MAD), and age-appropriate daily feeding (ADF) were less stunted (14.8%, 12.3%, and 6.4%, respectively) than children who never adhered to these indicators (25.2%, 30.1%, and 24.8%, respectively). A higher adherence to MDD and ADF was associated with a higher height-for-age Z-score (HAZ) (beta: 0.13, 95% CI: 0.01-0.25 and beta: 0.36, 95% CI: 0.22-0.50), while a higher adherence to the MDD and MAD was associated with a higher weight-for-height Z-score (WHZ) (beta: 0.19, 95% CI: 0.08-0.30; and beta: 0.16, 95% CI: 0.05-0.27). A higher adherence to a minimum meal frequency (MMF) was associated with a lower HAZ (beta: -0.99, 95% CI: -1.28--0.70). Our findings showed that to reduce wasting and stunting in Cambodia, interventions should focus on improving both the quality and quantity of food intake of children under two while targeting the whole complementary feeding period
Consistent seismic event location and subsurface parameters inversion through slope tomography : a variable-projection approach
No full textWe revisit the hypocentre-velocity problem, which is of interest in different fields as for example microseismics and seismology. We develop a formulation based on kinematic migration of two picked kinematic attributes in the 2-D case, the traveltime and the slope (horizontal component of the slowness vector), from which we are able to retrieve the location and subsequently the origin time correction and the subsurface parameters mainly velocity. We show how, through a variable projection, the optimization problem boils down to a physically consistent and parsimonious form where the location estimation is projected into the subsurface parameter problem. We present in this study a proof of concept validated by a toy test in two dimensions and a synthetic case study on the Marmousi model. The method presented in this study is extendible to three dimensions by incorporating the crossline slope or the backazimuth as a supplementary attribute