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International audience; Climate change by altering spatio-temporal distributions of suitable habitats leads to modifications in a multitude of species ranges. In recent years, the ability of species to physically adjust to the changing climatic conditions is of growing concern. We developed a generic trait-based method to assess the ability of species to explore new suitable habitats under climate change. Anadromous fish populations of the northern Atlantic were chosen as a suitable application case due to their high variability in terms of migratory behavior and degree of philopatry. The calculation of an Exploratory Potential Index (EPI) relies on a formal framework and a participatory procedure adapted from the Analytical Hierarchy Process (AHP) theory. It combines independent relevant life-history traits and ecological attributes into a single numeric value and permit to gather expert opinion by decomposing a complex issue into a hierarchy of more easily comprehended sub-problems through pairwise comparison matrices. Straying, earliness of first maturity, body size at first maturity, Distance covered to access feeding grounds and the reproduction strategies were identified by the expert. Results allow to identify different dispersal strategies an support strong differences in the ability to explore potential suitable habitat among anadromous fish. Even though they have contrasted life cycles, Morone saxatalis, Acipenser oxyrinchus and Alosa mediocris outperformed most of the species, while other species as Acipenser brevirostrum demonstrated had the lowest scores. Broader applications of the EPI would help to identify regions acting as potential sources of migrants and thus of priority for conservation biologists and resources.

International audience; The European sturgeon is critically endangered and the French ex-situ conservation approach involves developing a captive stock to produce offspring for release to boost natural populations. The purpose of our study was to assess the effects of rearing environment before stocking on the survival, growth, and behavior of three-month-old sturgeons from two different crossings. Enriched rearing was designed to mimic the variability of the natural environment using river water, natural photoperiod, substrate, variable water current and depths. Traditional rearing was carried out with bare tanks, underground water, dark conditions, without current and at constant depth. Fish survival was determined monthly and growth was estimated weekly. Behavior was assessed with exploration and novel prey tests in solitary using video tracking. Results demonstrated that enriched condition resulted in bigger fish from the first month. Growth curve analysis revealed that enriched environment made both fish crossings grow in a similar manner. In contrast, crossings growth differed in traditional rearing which may reflect a genotype-environment interaction. Behavioral data highlighted that enriched-reared fish were slower to explore a new environment but more individuals engaged on doing so than traditional-reared fish. Results also showed that survival was high (> 80 %) during all the trial. However, survival was lower during the second month in enriched environment. Our findings advocate for the integration of enriched rearing practices within the juvenile production for release in order to boost the performance linked to fitness. Stocking practices and life history research must work together to favor adaptive aquaculture approaches, which support species conservation.

International audience; Species can respond to climate change by tracking appropriate environmental conditions in space, resulting in a range shift. Species Distribution Models (SDMs) can help forecast such range shift responses. For few species, both correlative and mechanistic SDMs were built, but allis shad (Alosa alosa), an endangered anadromous fish species, is one of them. The main purpose of this study was to provide a framework for joint analyses of correlative and mechanistic SDMs projections in order to strengthen conservation measures for species of conservation concern. Guidelines for joint representation and subsequent interpretation of models outputs were defined and applied. The present joint analysis was based on the novel mechanistic model GR3D (Global Repositioning Dynamics of Diadromous fish Distribution) which was parameterized on allis shad and then used to predict its future distribution along the European Atlantic coast under different climate change scenarios (RCP 4.5 and RCP 8.5). We then used a correlative SDM for this species to forecast its distribution across the same geographic area and under the same climate change scenarios. First, projections from correlative and mechanistic models provided congruent trends in probability of habitat suitability and population dynamics. This agreement was preferentially interpreted as referring to the species vulnerability to climate change. Climate change could not be accordingly listed as a major threat for allis shad. The congruence in predicted range limits between SDMs projections was the next point of interest. The difference, when noticed, required to deepen our understanding of the niche modelled by each approach. In this respect, the relative position of the northern range limit between the two methods strongly suggested here that a key biological process related to intraspecific variability was potentially lacking in the mechanistic SDM. Based on our knowledge, we hypothesized that local adaptations to cold temperatures deserved more attention in terms of modelling, but further in conservation planning as well.

National audience

National audience

SturTOP is a multidisciplinary project launched in 2013 to investigate effects of chemical, thermal or hypoxic stress conditions on the health, the physiology, the behaviour and the adaptability of the first life stages of the European sturgeon. Experiments will be performed to evaluate responses of embryos and larvae exposed: i) in controlled conditions to environmental ranges of temperatures, oxygen and pollutant mixture, ii) to sediments collected from spawning grounds, iii) in situ. Studied effects will concern the individual fitness i.e. survival, ontogeny and behaviour as well as DNA damage, epigenetic modifications, gene expression and protein expression profiles. The same effects will be studied for 3 month-old farmed sturgeon (age of stocking) exposed in experimental systems which mimic the environmental conditions. In the wild, environmental exposure to pollutants will be evaluated thanks to individual dosimeters and to chemical analysis of stomach content. In a final step, a model will be built to simulate the future for a cohort subjected to multiple stresses. Expected results will give insights into the ability of this species to grow and to reproduce in the Gironde estuary and to adapt to changing environmental conditions. It could help decision-making by managers in charge of restoration plans.

Poissons migrateurs et restauration du milieu : quelles convergences de vue entre usagers et scientifiques en Seine?. 3. Journées de la biodiversité. Biodiversité : Sciences et Gouvernance en Région.

Approche éco-anthropologique visant à identifier un poisson migrateur qui pourrait matérialiser la reconquête de la qualité du bassin Seine. Séminaire de restitution des travaux Seine aval

An original eco-anthropological approach to dentif a diadromous species that could materialise the recovery of the water and habitat quality within the Seine basin. DiadFish : les poissons migrateurs amphihalins d'Europe

The Gironde estuary, in the southwest of France, is the last Western European estuary where all diadromous fish still migrate. In addition, the Gironde-Garonne-Dordogne basin is the last system known where the reproduction of the Atlantic sturgeon takes place. The Gironde estuary is an essential habitat for the completion of the life history of this diadromous species. A European recovery plan launched in 1994 has shown the significance of the estuary for feeding and acclimatization of juveniles before their first journey to the sea. The Atlantic sturgeon has been threatened in the last 50 years, mostly by gravel extraction in spawning grounds and unadapted fishing regulations that have led to overfishing. Since the end of the 19th century, several measures connected to navigation (dykes, rockfill, groynes) have been carried out in the Gironde estuary. This estuary, although only industrialised to a slight extent, has suffered from dredging since the creation of the navigation channel in 1875. Although gravel extraction is commonly recognised as causing serious damage to fish habitats, new gravel extraction projects in the Gironde estuary are under consideration. A qualitative risk factor analysis, based on the latest knowledge on the biology and ecology of the Atlantic sturgeon, shows that these projects lead to maximum risk for the survival of this species. Taking into account the present fragility of the sturgeon population, protective measures must be taken as a precaution. These would rule out any further gravel extraction. El estuario del Gironda, en el sudoeste de Francia, es el último estuario de Europa occidental donde todavía migran todos los peces diadromos. Además, la cuenca Gironda-Garona-Dordoña es el último sistema conocido donde tiene lugar la reproducción del esturión atlántico. El estuario del Gironda es un hábitat esencial para la realización del ciclo vital de esta especie diadroma. Un plan de recuperación europeo iniciado en 1994 ha mostrado la importancia del estuario para la alimentación y aclimatación de los juveniles antes de su primer viaje al mar. El esturión atlántico ha sido amenazado en los últimos 50 años, principalmente por la extracción de grava en los frezaderos y por los obsoletos reglamentos que han provocado su sobrepesca. Desde finales del siglo XIX, diversas medidas relativas a la navegación (diques, relleno con piedras, espigón) se han llevado a cabo en el estuario del Gironda. Este estuario, industrializado, aunque sólo de forma ligera, ha sufrido dragados desde la creación de un canal de navegación en 1875. Si bien la extracción de grava se reconoce comúnmente como causante de graves daños en los hábitats de peces, se están considerando nuevos proyectos de extracción de grava en el estuario del Gironda. Un análisis de los factores de riesgo cualitativos, basado en los últimos conocimientos de la biología y ecología del esturión atlántico, muestra que estos proyectos conllevan el máximo riesgo para la supervivencia de esta especie. Teniendo en cuenta la fragilidad actual de la población de esturión, deben tomarse medidas protectoras como precaución. éstas deberían excluir cualquier extracción adicional de grava. Instituto Español de Oceanografía

International audience; Lactotransferrin (Lf), an iron-binding glycoprotein present as a major component in the specific granules of human neutrophilic granulocytes is released in the blood during the acute phase of infection and participates in the regulation of the host-defence mechanisms. Our previous observations (Mazurier et al., 1989) showing i) that the activation by PHA of T-lymphocytes induces the appearance at the cell surface of Lf-receptors which are absent from the membrane of resting lymphocytes and ii) that Lf becomes a growth factor for the activated lymphocytes, led us to undertake a series of researches on the presence of Lf receptors at the surface of different blood cells. Characterization of Lf receptors was performed by flow cytofluorimetry using either Lf labelled on its glycan moiety with fluorescein or purified anti-lymphocyte Lf receptor antibodies. High affinity receptors for Lf were characterized only at the surface of human activated lymphocytes and of non-activated platelets. These two receptors possess common physicochemical properties and antigenic epitopes. Low affinity receptors for Lf were characterized on monocytes, eosinophils and neutrophils. These receptors are immunologically different from those found on activated lymphocytes and on non-activated platelets. Cell-lines of human lymphocyte T and megakaryocyte possess lactotransferrin receptors whose properties are similar to those found on peripheral blood cells. The soluble form of the receptor identified in the lymphocytes T culture medium possesses a molecular mass close to that of the membrane receptor suggesting that the cytoplasmic tail of the receptor should be very short.