Variabilité temporelle des grands poissons pélagiques exploités dans les écosystèmes marins tropicaux

Le développement de la pêche thonière industrielle dans l océan mondial depuis le début des années 1950 et le suivi des statistiques de pêche par les différentes commissions thonières régionales nous ont permis de construire des séries temporelles de captures et de taux de captures (CPUE) sur les principales espèces commercialement exploitées. Les océans ont été divisés en grandes provinces biogéographiques définies par Longhurst. Les statistiques spatialisées de pêche ont été agrégées par province biogéographique, par pays pêcheur et par espèce. Les composantes périodiques de chaque série temporelle ont été mises en évidence à partir de la méthode des ondelettes. Pour comparer les spectres d ondelettes, nous avons appliqué une méthode multivariée basée sur la covariance entre chaque paire de spectres. Chaque spectre est identifié par une modalité de chacun des facteurs (espèce, province, flottille, ou océan). A partir d une matrice de distances entre toutes les paires de spectres, nous avons classé les séries temporelles et identifié les facteurs les plus influant. Ensuite, nous avons étudié les relations entre les séries de capture et de CPUE et les indices climatiques globaux à partir des analyses d ondelettes croisées. Les résultats montrent que le facteur province géographique structure plus les patterns de variations que les facteurs espèce et océan . L impact de la variabilité climatique sur les séries de captures de thons est modulé par la province géographique aussi. Les fluctuations des séries temporelles traduisent donc des interactions complexes entre les processus biologiques, les stratégies de pêche et la variabilité environnementale.PARIS-BIUSJ-Sci.Terre recherche (751052114) / SudocSudocFranceF

Une nouvelle dimension à l’analyse palynologique. Le potentiel des pollen washes pour une meilleure compréhension de l’utilisation des plantes

International audienceFood, pharmacopoeia, funerary rituals... The interdependent relationships developed over the millennia between societies and plants have been preoccupying specialists in the analysis of pollen grains and plant spores since the 1960s (Roux 1967). Leaving aside palaeo-environmental reconstructions - often the prerogative of investigations into natural peat or lacustrine sequences - palynologists here aim to analyse the use of wild and domestic plants and what this means in terms of the practices of ancient communities and even the behaviour of people in the past. From the 1970s onwards, American palynologists began to tackle this methodological and conceptual obstacle by focusing their attention not just on the stratigraphic unit or the archaeological structure, but by incorporating into their study models the artefact produced by the hand of man himself (Hill, Hevly 1968). This was the birth of the 'Pollen Washes' technique

Patterns of variations in large pelagic fish : a comparative approach between the Indian and the Atlantic Oceans

Catch data of large pelagic fish such as tuna, swordfish and billfish are highly variable ranging from short to long term. Based on fisheries data, these time series are noisy and reflect mixed information on exploitation (targeting, strategy, fishing power), population dynamics (recruitment, growth, mortality, migration, etc.), and environmental forcing (local conditions or dominant climate patterns). In this work, we investigated patterns of variation of large pelagic fish (i.e. yellowfin tuna, bigeye tuna, swordfish and blue marlin) in Japanese longliners catch data from 1960 to 2004. We performed wavelet analyses on the yearly time series of each fish species in each biogeographic province of the tropical Indian and Atlantic Oceans. In addition, we carried out cross-wavelet analyses between these biological time series and a large-scale climatic index, i.e. the Southern Oscillation Index (Sol). Results showed that the biogeographic province was the most important factor structuring the patterns of variability of Japanese catch time series. Relationships between the SOI and the fish catches in the Indian and Atlantic Oceans also pointed out the role of climatic variability for structuring patterns of variation of catch time series. This work finally confirmed that Japanese longline CPUE data poorly reflect the underlying population dynamics of tunas

Time series analysis of tuna and swordfish catches and climate variability in the Indian Ocean (1968-2003)

We analysed the patterns of variation that characterize 33 catch time series of large pelagic fishes exploited by the Japanese and Taiwanese longline fisheries in the Indian Ocean from 1968 to 2003. We selected four species, the yellowfin (Thunnus albacares), the bigeye (T. obesus), the albacore (T. alalunga), and the swordfish (Xiphias gladius) and aggregated data into five biogeographic provinces of Longhurst (2001). We carried out wavelet analyses, an efficient method to study non-stationary time series, in order to get the time-scale patterns of each signals. We then compared and grouped the different wavelet spectra using a multivariate analysis to identify the factors (species, province or fleet) that may influence their clustering. We also investigated the associations between catch time series and a large-scale climatic index, the Dipole Mode Index (DMI), using cross wavelet analyses. Our results evidenced that the geographical province is more important than the species level when analyzing the 33 catch time series in the tropical Indian Ocean. The DMI further impacted the variability of tuna and swordfish catch time series at several periodic bands and at different temporal locations, and we demonstrated that the geographic locations modulated its impact. We discussed the consistency of time series fluctuations that reflect embedded information and complex interactions between biological processes, fishing strategies and environmental variability at different scales

Principes, méthodes et résultats préliminaires de la technique des “pollen washes” appliquée sur des objets archéologiques

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Artefact pollen washes: recovering pollen imprints of plant usage in archaeological objects

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Advancing the analysis of past human/plant relationships: methodological improvements of artefact pollen washes

International audienceThe 'pollen washes' technique, based on the analysis of the pollen embedded in the porous surface of archaeological artefacts, is developed for investigating past plant usage and consumption and to characterize the functionality of artefacts related to plant processing, gathering and storage. The research presented results in relevant methodological improvements of this technique, which has never previously been applied on materials from European contexts. The improvements allow: (1) faster analysis of a broad series of artefacts or those with large use-surface areas likely to retain more pollen; and (2) a more thorough, deeper and precise cleaning method, allowing the study of smoother artefacts. Finally, the recovery of Trifolium-group pollen from a macro-lithic tool from Xicotó rock shelter (Montsec ranges, Spain) demonstrates that the pollen washes technique can reveal new insights into both the use and consumption of wild and domestic plants by prehistoric societies, and the functionality of archaeological objects whose interpretation is still problematic