Search

International audience; Climate change, land use intensification, and waterabstraction magnify the frequency and severity of droughts but also result in totally unnatural hydrological patterns. Longer and more severe droughts slow down organic matter decomposition, whereas the effect of drying history, i.e. the specific sequence of different conditions to which organic matter is exposed, has seldom been addressed. Drying history could have important consequences for microbial communities colonizing and decomposing leaf litter in streams given the rapid fluctuations in microbial composition and processes. We studied whether the effects of drought-related impacts (stagnation, drying and both) on microbial activity and leaf litter decomposition are affected by the timing when peak stress (stagnation or drying) occurs, and whether the effect of the drying history is consistent among the three different stress types. In laboratory microcosms, we recreated areas with flowing water (aerated water), isolated pools with stagnant water (non-aerated water) and dry beds (dry microcosms). Combining these conditions and their sequence, we created nine treatments (ten with the control) differing in stress type (stagnation, drying, both) and timing of peak stress (early, middle, late), and measured fungal biomass, sporulation, microbial respiration, and microbial decomposition of alder leaf disks. The effects of drought-related stress conditions were not consistent among response vari- ables. However, disturbances were systematically more detrimental to decomposition in early stages, resulting in a lower fungal biomass and activity, and reduced microbial litter decomposition. These results suggest that the effects of stress on decomposition-associated variables depend not only on the intensity of the stress, but also on its timing, with early stress and its legacy effects having greatest impact on leaf litter decomposition.

International audience; The Biological Resource Centre for the Environment BRC4Env is a network of Biological Resource Centres (BRCs) and collections whose leading objectives are to improve the visibility of genetic and biological resources maintained by its BRCs and collections and to facilitate their use by a large research community, from agriculture research to life sciences and environmental sciences. Its added value relies on sharing skills, harmonizing practices, triggering projects in comparative biology, and ultimately proposing a single-entry portal to facilitate access to documented samples, taking into account the partnership policies of research institutions as well as the legal frame which varies with the biological nature of resources. BRC4Env currently includes three BRCs: the Centre for Soil Genetic Resources of the platform GenoSol, in partnership with the European Conservatory of Soil Samples; the Egg Parasitoids Collection (EP-Coll); and the collection of ichthyological samples, Colisa. BRC4Env is also associated to several biological collections: microbial consortia (entomopathogenic bacteria, freshwater microalgae…), terrestrial arthropods, nematodes (plant parasitic, entomopathogenic, animal parasitic...), and small mammals. The BRCs and collections of BRC4Env are involved in partnership with academic scientists, as well as private companies, in the fields of medicinal mining, biocontrol, sustainable agriculture, and additional sectors. Moreover, the staff of the BRCs is involved in many training courses for students from French licence degree to Ph.D, engineers, as well as ongoing training.

10 pages; International audience; Mate preference for conspecifics does not necessarily lead to assortative mating in cases where mating outcomes also depend on preferences based on mate quality and on individual competitiveness. We tested how such traits affected mate choice among genetically divergent lineages (called molecular operational taxonomic units; MOTU) of the amphipod Gammarus fossarum. We presented males with two females, including one from its own MOTU. Females also potentially differed in body size, and therefore fecundity, and in time before reproduction, two traits previously recognized as important in male mate choice. Males generally preferred females from their own MOTU when females originated from highly divergent MOTUs (17 % genetic divergence), but not when they were more closely related (3.5 % genetic divergence). Contrary to expectations, they did not prefer larger females, but they consistently paired with the female closest to reproduction. A second experiment involving duos of males of different MOTUs in competition for a female also revealed that males consistently won the competition over pairing with females of their own MOTU. Overall, these results reveal a strong influence of genetic divergence on mate recognition and reproductive isolation between sympatric MOTUs. However, male preference for females that are close to being available for reproduction also potentially results in hybridization among closely related MOTUs. We examine these results in the light of field mating patterns observed in a previous study of G. fossarum and discuss the importance of considering competitiveness and preferences for mate quality signals when studying evolutionary consequences of secondary contact between divergent lineages.

The blue shark Prionace glauca is a top predator with one of the widest geographic distributions of any shark species, yet classified as critically endangered in the Mediterranean Sea, and Near Threatened globally. Previous genetic studies did not reject the null hypothesis of a single global population across the worldwide species range. Blue shark situation was proposed as a possible archetype of the ‘grey zone of population differentiation’, coined to designate cases where population structure may be too recent or too faint to be detected using a limited set of markers. Here, blue shark samples collected throughout its global range were sequenced using a specific ddRAD method (DArTseq; Georges et al. 2018), which recovered 37,655 genome-wide single nucleotide polymorphisms (SNPs). Two main groups emerged, with Mediterranean Sea and Northern Atlantic samples significantly differentiated from the Indo-west Pacific samples. Significant pairwise FST values indicated further genetic differentiation within the Atlantic Ocean, and between the Atlantic Ocean and the Mediterranean Sea. Reconstruction of recent demographic history suggested the divergence between northern and southern oceanic populations emerged about 500 generations ago and revealed a drastic reduction in effective population size from a large ancestral population. Our results illustrate the power of high-density genome scans to detect population structure and reconstruct demographic history in highly migratory marine species. As the management of the blue shark fishery, either as target or as bycatch, does not account for this delineation, we strongly recommend that the results presented here be considered in future stock assessment and management plans.

International audience; Within-population variation in individual tree growth and response to climate has an impact on forest dynamics, resilience and adaptation to environmental change.Combining dendrochronological analyses with a process-based ecophysiological model simulating drought stress at the stand scale, we studied the phenotypic variation of two growth-related traits within 22 pure stands of five contrasted tree species sampled in the RENECOFOR network over a wide range of ecological conditions. First, we computed the annual stress level from soil, climate and stand inventory data. Second, we computed individual sensitivity as the quantitative growth response to drought stress level and individual vigor as the capacity to grow in favorable years relative to an average stand-level growth model. We analyzed within-population variation and covariation of individual vigor and sensitivity, their temporal changes during stand development, as well as the effect of environmental conditions on population-level means, variances and correlation.Our results show that within-population variances in sensitivity and vigor exceed the between-population variances for all species. The populations located in more stressful environments, i.e., low summer precipitation and extractable soil water, showed lower mean and variance of sensitivity, suggesting possible multiscale adaptation at the population level and within populations. None of the environmental factors considered had an effect on the average population vigor or on the within-population variance of vigor. We found a general positive correlation between individual growth sensitivity and vigor in 17 out of 22 populations, potentially revealing a growth performance trade-off. The correlation was more pronounced in low extractable soil water environments, which may be related to a need for stressful conditions to reveal the trade-off or be the consequence of adaptive processes, i.e., acclimation and selection.If high within-population stand phenotypic variation in growth traits contributes to the resilience and adaptive capacity of forests to climate change, a trade-off could represent a constraint on selection. We provide genetic and environmental arguments supporting the hypothesis of a trade-off, then we highlight the importance of integrating it into the management process, especially during selective thinning, to avoid indirectly increasing population sensitivity by selecting the most vigorous trees.

International audience; Boldness, defined as the behavioural response of individuals when facing a risky situation, is a majorpersonality trait and often phenotypically correlates with other behavioural traits, in particular aggressiveness,exploration behaviour and neophobia. Yet, whether such links result from among-individualcorrelations, i.e. form behavioural syndromes sensu stricto, is often ignored and whether such syndromesmay yield individual fitness benefits, and thus be selected for, remains poorly explored. Wemeasured boldness as the nest defence behaviour against a dummy nest predator in a natural populationof a small passerine bird, the collared flycatcher, Ficedula albicollis, and investigated the existence of abehavioural syndrome between boldness and two other behavioural traits, aggressiveness (measured asthe agonistic response to competitors) and neophobia (measured as the behavioural response to a novelobject in a known environment). Then we assessed the links between this potential syndrome andreproductive success, measured as fledging and recruitment success. Boldness score differed between thesexes and depended on whether the partner was present during the test. Nevertheless, it was repeatable,showing that boldness can be considered as a personality trait in our population. We found a positiveamong-individual correlation between boldness and aggressiveness, showing the existence of a behaviouralsyndrome between both personality traits. This syndrome was related to reproductive success: thenumber of fledged young (but not recruitment probability) increased with one integrative value of theboldnesseaggressiveness syndrome. Conversely, boldness score was not correlated with neophobia. Ourresults thus clearly reveal a behavioural syndrome between boldness and aggressiveness with possibleconsequences for reproductive success in the study population, and therefore raise the question of theevolutionary implications of such a behavioural syndrome

19 Pág., Microgeographical adaptation occurs when the effects of directional selection persist despite gene flow. Traits and genetic loci under selection can then show adaptive divergence, against the backdrop of little differentiation at other traits or loci. How common such events are and how strong the selection is that underlies them remain open questions. Here, we discovered and analysed microgeographical patterns of genomic divergence in four European and Mediterranean conifers with widely differing life-history traits and ecological requirements (Abies alba MIll., Cedrus atlantica [Endl.] Manetti, Pinus halepensis Mill. and Pinus pinaster Aiton) by screening pairs from geographically close forest stands sampled along steep ecological gradients. We inferred patterns of genomic divergence by applying a combination of divergence outlier detection methods, demographic modelling, Approximate Bayesian Computation inferences and genomic annotation to genomic data. Surprisingly for such small geographical scales, we showed that selection is strong in all species but generally affects different loci in each. A clear signature of selection was systematically detected on a fraction of the genome, of the order of 0.1%-1% of the loci depending on the species. The novel modelling method we designed for estimating selection coefficients showed that the microgeographical selection coefficient scaled by population size (Ns) was 2-30. Our results convincingly suggest that selection maintains within-population diversity at microgeographical scales in spatially heterogeneous environments. Such genetic diversity is likely to be a major reservoir of adaptive potential, helping populations to adapt under fluctuating environmental conditions., Agence Nationale de la Recherche, Grant/ Award Number: FLAG project (ANR-12- ADAP-0007-01); European Commission, Grant/Award Number: TOPWOOD project (MSCA-RISE-2014-645654- TOPWOOD) and grant agreement No. 676876 (GenTree); Ministère de l'Écologie, du Développement Durable et de l'Énergie, Grant/Award Number: GRAAL project (10-MCGOT-GICC-8-CVS-139)

Corrigendum on: Volume 16, Issue 1, Evolutionary Applications, pages: 189-189, First Published online: January 18, 2023.; International audience; The study of eco-evolutionary dynamics, that is of the intertwinning between ecologi- cal and evolutionary processes when they occur at comparable time scales, is of grow- ing interest in the current context of global change. However, many eco-evolutionary studies overlook the role of interindividual interactions, which are hard to predict and yet central to selective values. Here, we aimed at putting forward models that simulate interindividual interactions in an eco-evolutionary framework: the demo- genetic agent-based models (DG-ABMs). Being demo-genetic, DG-ABMs consider the feedback loop between ecological and evolutionary processes. Being agent-based, DG-ABMs follow populations of interacting individuals with sets of traits that vary among the individuals. We argue that the ability of DG-ABMs to take into account the genetic heterogeneity—that affects individual decisions/traits related to local and instantaneous conditions—differentiates them from analytical models, another type of model largely used by evolutionary biologists to investigate eco-evolutionary feed- back loops. Based on the review of studies employing DG-ABMs and explicitly or implicitly accounting for competitive, cooperative or reproductive interactions, we illustrate that DG-ABMs are particularly relevant for the exploration of fundamental, yet pressing, questions in evolutionary ecology across various levels of organization. By jointly modelling the effects of management practices and other eco-evolutionary processes on interindividual interactions and population dynamics, DG-ABMs are also effective prospective and decision support tools to evaluate the short- and long-term evolutionary costs and benefits of management strategies and to assess potential trade-offs. Finally, we provide a list of the recent practical advances of the ABM com- munity that should facilitate the development of DG-ABMs.

High genetic variation and extensive gene flow may help forest trees with adapting to ongoing climate change, yet the genetic bases underlying their adaptive potential remain largely unknown. We investigated range-wide patterns of potentially adaptive genetic variation in 64 populations of European beech (Fagus sylvatica L.) using 270 SNPs from 139 candidate genes involved either in phenology or in stress responses. We inferred neutral genetic structure and processes (drift and gene flow) and performed differentiation outlier analyses and gene-environment association (GEA) analyses to detect signatures of divergent selection.Beech range-wide genetic structure was consistent with the species’ previously identified postglacial expansion scenario and recolonization routes. Populations showed high diversity and low differentiation along the major expansion routes. A total of 52 loci were found to be putatively under selection and 15 of them turned up in multiple GEA analyses. Temperature and precipitation related variables were equally represented in significant genotype-climate associations. Signatures of divergent selection were detected in the same proportion for stress response and phenology-related genes. The range-wide adaptive genetic structure of beech appears highly integrated, suggesting a balanced contribution of phenology and stress-related genes to local adaptation, and of temperature and precipitation regimes to genetic clines. Our results imply a best-case scenario for the maintenance of high genetic diversity during range shifts in beech (and putatively other forest trees) with a combination of gene flow maintaining within-population neutral diversity and selection maintaining between-population adaptive differentiation.

International audience; Species that have sex determined by environmental conditions during development (i.e., environmental sex determination [ESD]) are especially vulnerable to environmental change, including altered stress levels, habitat loss, and species translocations. These factors can produce multigenerational trends in population size and eco-evolutionary dynamics not captured by existing theory based on lifetime reproductive success (R0). Here, we extend ESD theory to use per capita growth rate r as a more appropriate measure of evolutionary success (fitness), and we demonstrate the importance of this change when males and females can differ in maturation times and when maturation times vary with local conditions (plasticity). In these cases, we show that primary and secondary sex ratios may be strongly biased; that optimal maturation times, when locally plastic, depend on the balance between mortality and growth effects; and that plasticity of maturation times can ameliorate fitness costs of increasing environmental stress

International audience; The ecology of the young stages of allis shad Alosa alosa is poorly documented, although they can be exposed to many pressures during their freshwater phase and their downstream migration. When passing through systems such as the Gironde-Garonne-Dordogne watershed (GGD, SW France), they can be subjected to high temperatures and low levels of oxygen (hypoxia). The aim of this work is to assess the tolerance of young Alosa alosa at four ages (c. 10, 30, 60 and 85 days old) by challenging them to different temperatures (18, 22, 26 and 28C) together with decreasing oxygen saturation levels (from 100% to 30%). Survival of the 10-day-old individuals was not influenced by oxy-thermic conditions, but high stress levels were detected and perhaps this age class was too fragile regarding the constraint of the experimental design. Survival at 30 and at 60 days old was negatively influenced by the highest temperatures tested alone (from 26C and from 28C, respectively) but no effect was detected at 85 days old up to 28C. A combined effect of temperature and oxygen level was highlighted, with heat accelerating survival decrease when associated with oxygen level depletion: essentially, survival was critical (

This study focused on tree mortality in spruce-dominated stands managed using the single-tree selection method in southern Finland. Together with regeneration and tree growth, mortality is one of the basic elements of the stand structure and dynamics in selection stands. The study was based on data acquired from a set of 20 permanent experimental plots monitored with repeated measurements for 20 years. The average mortality in the number of stems (N) was 4.45 trees ha−1a−1, in basal area (G) 0.07 m2 ha−1a−1, and in stemwood volume (V) 0.56 m3 ha−1a−1. In relative terms it was 0.50% of N, 0.30% of G and 0.27% of V, respectively. Wind and snow were the most common causes of mortality, while deaths by biotic causes (mammals, insects, pathogens) were extremely rare. Some 6–10% of the total loss in the number of stems and volume was attributable to the loss or removal of trees that sustained serious damage in harvesting. Most of the mortality occurred in the smallest diameter classes of up to 20 cm. Such a high mortality among small trees can have an adverse influence on the sustainability of selection structures if not successfully checked in harvesting and management.

International audience; As part of the PALEOFISH project, a total of 163 fish bones supposed Anguillidae (65) andSalmonidae (98), mainly vertebrae, from paleolithic to the late medieval period were converted into Illumina next-generation sequencing libraries following a dedicated ancient DNA extraction protocol from about 30 mg of bone material on average. We then developed a workflow in Genotoul's Galaxy to automate the data pre-processing (sequence clean-up and qualification pre/post clean-up), and alignment with reference genomes (FastQC, Fastp, BWA). We mapped all our individual sequence libraries against available Salmonidae and Anguillidae whole genomes from NCBI database, as well as other reference sequences for species of fish, bacteria, and vertebrates.In these results, the average read length after filtering was between 40 and 70 pb, with GCcontent around 50%. Most samples provided several millions of curated sequences reads:ranging from 2 to 19 million (with an average of 3.64 million for all samples; 3.3 million forSalmonidae and 4.5 million for Anguillidae). This study revealed both a high success rates in positive DNA sequencing from these archaeological samples and our ability to address their genetic identification of to the species level in Anguillidae (56 samples correctly mapped on 65) and Salmonidae (85 samples correctly mapped on 98 to Salmo sp.), i.e. 86% and 87%, success respectively. The mean percentage of endogenous DNA was high for both species. Endogenous DNA ranges from 1.49 to 76.8%, with an arithmetic mean of 38.3% for Anguillidae, and from 0.6 to 87.7%, with an arithmetic mean of 27.8%, for Salmonidae. These first steps of “genetic quality” estimates were a key to identify the potential in the use of calcified archaeological pieces in fish.; Dans le cadre du projet PALEOFISH, nous avons analysé un total de 163 pièces calcifiées de poisson, principalement des vertèbres, ayant été identifiées par les archéo-ichtyologues comme des Anguillidae (65) ou des Salmonidae (98), et datées du paléolithique à la fin de la période médiévale. L’extraction des ADNs anciens a été réalisée à partir d’une moyenne d'environ 30 mg de matière osseuse, selon un protocole dédié. Ces échantillons ont ensuite été convertis en banques Illumina et séquencés à faible profondeur. Pour automatiser le pré-traitement des données de séquençage (nettoyage des séquences et qualification pré/post nettoyage) et l'alignement avec les génomes de référence (FastQC, Fastp, BWA), nous avons développé un workflow sous Galaxy (Genotoul). Nous avons ainsi pu aligner toutes les séquences par rapport aux génomes de référence disponibles dans la base de données NCBI, chez l’ensemble des Salmonidae et Anguillidae, ainsi que sur d'autres génomes de référence de poissons, de bactéries et de vertébrés.Les résultats montrent une longueur moyenne des séquences après nettoyage comprise entre 40 et 70 pb, avec une teneur en GC d'environ 50 %. Les échantillons ont fourni de 2 à 19 millions de séquences (avec une moyenne arithmétique de 3,64 millions pour tous les échantillons ; 3,3 millions pour les Salmonidae et 4,5 millions pour les Anguillidae).Cette étude permet de révéler à la fois un taux de réussite élevé dans la production de séquences à l’échelle du génome de ces échantillons archéologiques et la capacité à aborder leur identification génétique au niveau spécifique chez les Anguillidae (56 échantillons correctement identifiés sur 65 totaux) et les Salmonidae (85 échantillons correctement identifiés sur 98 totaux à Salmo sp.), ce qui représente des taux de succès importants (86 % et 87 % respectivement). Le pourcentage moyen d'ADN endogène était également élevé pour les deux taxons : il varie de 1,5 à 76,8 %, avec une moyenne arithmétique de 38,3 % pour les Anguillidae, et de 0,6 à 87,7 %, avec une moyenne arithmétique de 27,8 %, pour les Salmonidae. Ces premières étapes d’évaluation quantitative (rendement total) et qualitative (taux d’ADN endogène) révèlent le potentiel d’utilisation des pièces archéologiques calcifiées chez les poissons.

International audience; Besides egg fertilization, females of many taxa obtain direct fitness benefits from male mates, such as food, protection or paternal care. But males often increase their own fitness by mating with several females, among which they distribute sperm along with the above-mentioned benefits, reducing the benefits to individual females. These diverging interests lead to a conflict in which each female may try to ensure male fidelity and get exclusive access to male-provided benefits. Here, we use a theoretical model to show how a female of an externally fertilizing species may achieve mate fidelity by soliciting copulations at such a rate that the male has insufficient sperm left to increase his fitness with additional females. We show that three alternative condition-dependent evolutionarily stable mating relationships emerge in this scenario, based on whether one mate’s preference for mating rate dominates, or the conflict is resolved by what amounts to negotiation. We demonstrate how these outcomes depend on some features of physiology, ecology, and behavior. In particular, a greater reproductive benefit to a female from exclusive access to a male partner—or the occasional tendency of females to withhold eggs during mating—can increase male fidelity; and continuous sperm regeneration rather than an initially-set stock of sperm allows for multiple within-pair mating across all three mating pattern

International audience; Despite growing evidence of spatial dispersal and gene flow between salmonid populations, the implications of connectivity for adaptation, conservation, and management are still poorly appreciated. Here, we explore the influence of a gradient of dispersal rates on portfolio strength and eco-evolutionary dynamics in a simulated population network of Atlantic salmon (Salmo salar) by extending a demo-genetic agent-based model to a spatially explicit framework. Our model results highlight a non-linear relationship between dispersal rates and the stability of the metapopulation, resulting in an optimal portfolio effect for dispersal rates around 20%. At local population scale, we also demonstrate phenotypic changes induced by density-dependent effects modulated by dispersal, and a dispersal-induced increase in genetic diversity. We conclude that it is critical to account for complex interactions between dispersal and ecoevolutionary processes and discuss future avenues of research that could be addressed by such modeling approaches to more fully appreciate responses of Atlantic salmon to environmental changes and investigate management actions accordingly.; Malgré des preuves de plus en plus abondantes de dispersion spatiale et de flux génétique entre populations de salmonidés, les conséquences de la connectivité en ce qui concerne l’adaptation, la conservation et la gestion demeurent mal comprises. Nous explorons l’influence d’un gradient de taux de dispersion sur la force du portefeuille et les dynamiques éco-évolutives d’un réseau de populations simulé de saumon atlantique (Salmo salar) en élargissant un modèle démo-génétique basé sur les agents à un cadre spatialement explicite. Les résultats du modèle font ressortir une relation non linéaire entre les taux de dispersion et la stabilité de la métapopulation, qui se traduit par un effet de portefeuille optimal pour des taux de dispersion d’environ 20 %. Nous démontrons aussi la présence de changements phénotypiques à l’échelle de la population locale induits par des effets dépendants de la densité modulés par la dispersion, ainsi qu’une augmentation de la diversité génétique induite par la dispersion. Nous concluons qu’il est d’importance capitale de tenir compte des interactions complexes entre la dispersion et les processus éco-évolutifs et abordons des avenues de recherche future pouvant être explorées à l’aide de telles approches de modélisation pour mieux comprendre les réponses du saumon atlantique aux changements environnementaux et examiner différentes mesures de gestion.

In 1954, brown trout were introduced to the Kerguelen archipelago (49°S, 70°E), a pristine, sub-Antarctic environment previously devoid of native freshwater fishes. Trout began spreading rapidly via coastal waters to colonize adjacent watersheds, however, recent and unexpectedly the spread has slowed. To better understand the ecology of the brown trout here, and why their expansion has slowed, we documented the marine habitat use, foraging ecology, and environmental conditions experienced over one year by 50 acoustically tagged individuals at the colonization front. Trout mainly utilized the marine habitat proximate to their tagging site, ranging no further than 7 km and not entering any uncolonized watersheds. Nutritional indicators showed that trout were in good condition at the time of tagging. Stomach contents and isotope signatures in muscle of additional trout revealed a diet of amphipods (68%), fish (23%), isopods (6%), and zooplankton (6%). The small migration distances observed, presence of suitable habitat, and rich local foraging opportunities suggest that trout can achieve their resource needs close to their home rivers. This may explain why the expansion of brown trout at Kerguelen has slowed.

International audience; Small populations establishing on colonization fronts have to adapt to novel environments with limited genetic variation. The pace at which they can adapt, and the influence of genetic variation on their success, are key questions for understanding intraspecific diversity. To investigate these topics, we performed a reciprocal transplant experiment between two recently founded populations of brown trout in the sub-Antarctic Kerguelen Islands. Using individual tagging and genetic assignment methods, we tracked the fitness of local and foreign individuals, as well as the fitness of their offspring over two generations. In both populations, although not to the same extent, gene flow occurred between local and foreign gene pools. In both cases, however, we failed to detect obvious footprints of local adaptation (which should limit gene flow) and only weak support for genetic rescue (which should enhance gene flow). In the population where gene flow from foreign individuals was low, no clear differences were observed between the fitness of local, foreign, and F1 hybrid individuals. In the population where gene flow was high, foreign individuals were successful due to high mating success rather than high survival, and F1 hybrids had the same fitness as pure local offspring. These results suggest the importance of considering sexual selection, rather than just local adaptation and genetic rescue, when evaluating the determinants of success in small and recently founded populations.

International audience; Allopatric gene pools can evolve in different directions through adaptive and nonadaptive processes and are therefore a source of intraspecific diversity. The connection of these previously isolated gene pools through human intervention can lead to intraspecific diversity loss, through extirpation of native populations or hybridization. However, the mechanisms leading to these situations are not always explicitly documented and are thus rarely used to manage intraspecific diversity. In particular, genotype-by-environment (GxE) interactions can drive postzygotic reproductive isolation mechanisms that may result in a mosaic of diversity patterns, depending on the local environment. We test this hypothesis using a salmonid species (Salmo trutta) in the Mediterranean (MED) area, where intensive stocking from non-native Atlantic (ATL) origins has led to various outcomes of hybridization with the native MED lineage, going from MED resilience to total extirpation via full hybridization. We investigate patterns of offspring survival at egg stage in natural environments, based on parental genotypes in interaction with river temperature, to detect potential GxE interactions. Our results show a strong influence of maternal GxE interaction on embryonic survival, mediated by maternal effect through egg size, and a weak influence of paternal GxE interaction. In particular, when egg size is large and temperature is cold, the survival rate of offspring originating from MED females is three times higher than that of ATL females’ offspring. Because river temperatures show contrast at small scale, this cold adaptation for MED females’ offspring constitutes a potent postzygotic mechanism to explain small-scale spatial heterogeneity in diversity observed in MED areas where ATL fish have been stocked. It also indicates that management efforts could be specifically targeted at the environments that actively favor native intraspecific diversity through eco-evolutionary processes such as postzygotic selection

International audience; Change in body size can be driven by social (density) and non-social (environmental and spatial variation) factors. In expanding metapopulations, spatial sorting by means of dispersal on the expansion front can further drive the evolution of body size. However, human intervention can dramatically affect these founder effects. Using long-term monitoring of the colonization of the remote Kerguelen islands by brown trout, a facultative anadromous salmonid, we analyse body size variation in 32 naturally founded and 10 human-introduced populations over 57 years. In naturally founded populations, we find that spatial sorting promotes slow positive changes in body size on the expansion front, then that body size decreases as populations get older and local density increases. This pattern is, however, completely different in human-introduced populations, where body size remains constant or even increases as populations get older. The present findings confirm that changes in body size can be affected by metapopulation expansion, but that human influence, even in very remote environments, can fully alter this process.

International audience

International audience; Invertebrate drift is an important ecological process but factors affecting the downstream transport of invertebrates are difficult to assess. The influence of water velocity on drift entry rates is still unclear and has rarely been quantified. In this study, conducted in spring and autumn, we investigated the drift propensity for different sizes of Baetis, Simulium and Chironomus larvae which, over a 24-h period, were subjected to low, moderate or high water velocities (14, 30 and 40 cm s-1, respectively) in either fine or coarse gravel beds. Interspecific differences were detected: Baetis drifted the most, Chironomus showed intermediate values and Simulium drifted the least. Chironomus was the only taxon that responded to water velocity. Baetis and Simulium were only slightly constrained to drift by the experimental conditions, while, in contrast, Chironomus larvae were very sensitive to flow increase. Substrate size (fine/coarse gravel bed) had no effect on any taxa. Small Simulium and Chironomus drifted more than larger ones. A seasonal effect was also detected, with Baetis drifting more in fall and Simulium drifting more in spring. Results suggest that community structure may be as or more important than hydraulics as a determinant of drift rates.

The aim of this study was to test whether the ichthyological diversity of one natural reserve in Reunion Island (Réserve de l'Etang de Saint-Paul) could be established with a molecular tool, environmental DNA (eDNA). We hence filtrated the water (2L) at 10 different areas around the reserve. For each sampling area, 12 PCR replicas were performed and the identification of fish species was carried out by metabarcoding through a primer over a mitochondrial region (12S). This study showed the importance of reference sequencing databases as well as improvements through phylogenetic analyses. This first fish study by eDNA in La Réunion also revealed the coherence of the distribution of species and their habitat. See the Poster in Suppl. material 1. Collection : 1st DNAQUA International Conference - poster session.

International audience

It is an ongoing issue to better understand colonization process, adaptation potential to new environments, and invasiveness of a species. The sub Antarctic Kerguelen Islands are a perfect model to model population dynamics in an invasion context, because it represents a simplified case of invasion by brown trout (Salmo trutta L.), a facultative anadromous fish. Introduced in the 1950s, and thanks to its dispersive and adaptive capacities, the brown trout provides a unique study model for understanding the causes and mechanisms underlying biological invasions. Understanding dispersal mechanisms, through the study of life history traits related to migration (e.g. growth, age at migration) and their temporal evolution in shifting expansion range population, is the core of this thesis work. Through the study of scales collected in this unique framework, the life histories of nearly 5000 fish have been rebuilt. This work demonstrates the importance of the methodology to determine accurate estimates of individual life history traits. Modelling the evolution of freshwater growth, body size at age and age at first migration demonstrates that evolutionary processes are at work according to the time since colonization. In particular, the decrease in growth rate over time and the decrease in body size at age over time and space suggest that the dispersal capacity is decreasing in populations located at the margins. The evolution of the threshold size at first migration confirms this results, and illustrates the importance of phenotypic plasticity and local adaptation in the choice of migratory tactics. However, the approach taken in this manuscript focuses on the evolution of migration, and would benefit from the study of the joint evolution of traits involved in fitness (costs-benefits balance), such as reproduction, or growth at sea.; Grâce à ses capacités dispersives et adaptatives, la truite commune (Salmo trutta L.), poisson anadrome facultatif, est un bon candidat à la colonisation de nouveaux milieux. L'introduction de l'espèce dans les années 1950 dans les îles subantarctiques de Kerguelen fournit un modèle d'étude unique pour comprendre les causes et les mécanismes de la dispersion, grâce à l'étude des traits d'histoire de vie en lien avec la migration (e.g. croissance, âge à la migration). L'étude de leur évolution temporelle le long d'un front de colonisation est le cœur de ce travail de thèse. A travers l’étude des écailles recueillies dans le cadre de ce programme à long terme, les histoires de vie de près de 5000 poissons ont été reconstruites. Ce travail démontre l’importance de la méthodologie utilisée afin de reconstruire les traits de vie individuel. La modélisation de l’évolution de la croissance en eau douce, de la taille à l’âge et de l’âge à la première migration démontre que des processus évolutifs sont en œuvre dans les populations en expansion. Notamment, le ralentissement de la croissance avec le temps ainsi que la diminution de la taille à l’âge le long du front de colonisation laissent à penser que la capacité de dispersion diminue à mesure que les populations sont en marges de la zone d’expansion. L’évolution de la valeur seuil à la première migration confirme ce résultat, et illustre l’importance de la plasticité phénotypique et de l’adaptation locale dans le choix de la tactique migratoire. Toutefois, l’approche menée dans ce manuscrit se concentre sur l’évolution de la migration, et bénéficierait de l’étude de l’évolution conjointe des traits impliqués dans la valeur sélective (balance coûts-bénéfices), tels que la reproduction, ou la croissance en mer.

International audience; The European eel Anguilla anguilla is listed as critically endangered by the IUCN. Among many threats, the introduced parasitic nematode Anguillicola crassus is suspected to alter the eels’ swim bladder and jeopardize their reproductive oceanic migration. To date, gaining knowledge about the distribution and prevalence of A. crassus requires individual sacrifice (over 50,000 eels were sacrificed for epidemiology studies since 2010). This paper describes a non-lethal molecular protocol for identifying prevalence of A. crassus in A. anguilla, based on searching for A. crassus DNA in the feces of eels. Tests using three DNA microsatellite markers specific to the nematode showed that molecular detection provided similar results to visual examination of the swim bladder in up to 80% of the cases, and allowed for comparison of prevalence among sites. Easy to implement, this non-lethal protocol for detecting A. crassus could be valuable for management plans of this endangered species.

During the reproductive season, animals have to manage both their energetic budget and gamete stock. In particular, for semelparous capital breeders with determinate fecundity and no parental care other than gametic investment, the depletion of energetic stock must match the depletion of gametic stock, so that individuals get exhausted just after their last egg is laid and fertilized. Although these budgets are managed continuously, monitoring the dynamics of mating acts and energy expenditure at a fine temporal scale in the wild is challenging.This study aimed to quantify the individual dynamics of spawning acts and the concomitant energy expenditure of female Allis shad (Alosa alosa) throughout their mating season.Using eight individual-borne accelerometers for one month, we collected tri-axial acceleration, temperature, and pressure data that we analysed to i) detect the timing of spawning acts, ii) estimate energy expenditure from tail beat frequency and water temperature, and iii) monitor changes in body roundness from the position of the dorsally-mounted tag relative to the vertical plane.Female shad had a higher probability to spawn during warmer nights, and their spawning acts were synchronized (both individually and inter-individually) within each active night. They experienced warmer temperature, remained deeper, swan more slowly and spent less energy during daytime than night time. Over one month of spawning, they performed on average 15.75 spawning acts, spent on average 6 277 kJ and died with a significant portion of residual oocytes. The acceleration-based indicator of body roundness was correlated to condition coefficient measured at capture, and globally decreased through the spawning season, although the indicator was noisy and was not correlated to changes in estimated energy expenditure.Despite significant individual variability, our results indicate that female shad exhausted their energetic stock faster than their egg stock. Water warming will increase the rate of energy expenditure, which might increase the risk that shad die with a large stock of unspent eggs. Although perfectible, the three complementary analyses of acceleration data are promising for in situ monitoring of energy expenditure related to specific behaviour.

International audience; L’URFM stocke plus de 40 000 échantillons végétaux soit à -20°C soit à température ambiante après déshydratation. Le projet présenté dans cet article a eu pour but d’évaluer la quantité et la qualité de l’ADN obtenu à partir d’échantillons de quatre espèces d’arbres méditerranéens. Pour mesurer la qualité de l’ADN, nous avons effectué des analyses de génotypage et de séquençage couramment utilisées au laboratoire. Nos résultats montrent une variation entre les quatre espèces étudiées en fonction du mode et de la durée de conservation sur la quantité et la qualité de l’ADN. De plus, nous avons montré que les échantillons conservés sur la plus longue période ou avec la méthode la plus basique (à sec) ne sont pas ceux qui présentent la moins bonne qualité d’ADN.

Estimation of abundance with wide spatiotemporal coverage is essential to the assessment and management of wild populations. But, in many cases, data available to estimate abundance time series have diverse forms, variable quality over space and time and they stem from multiple data collection procedures. We developed a hierarchical Bayesian modelling (HBM) approach that take full advantage of the diverse assemblage of data at hand to estimate homogeneous time series of abundances irrespective of the data collection procedure. We apply our approach to the estimation of adult abundances of 18 Atlantic salmon (Salmo salar) populations of Brittany (France) from 1987 to 2017 using catch statistics, environmental covariates, and fishing effort. Additional data of total or partial abundance collected in four closely monitored populations are also integrated into the analysis. The HBM framework allows the transfer of information from the closely monitored populations to the others. Our results reveal no clear trend in the abundance of adult returns in Brittany over the period studied. lations d'animaux sauvages. Dans de nombreux cas, toutefois, les donnees disponibles pour l'estimation de series chronologidifferentes procedures. Nous avons elabore une approche de modelisation bayesienne hierarchique (MBH) pour tirer pleinement parti de l'assemblage varie de donnees disponibles pour estimer des series chronologiques homogenes d'abondance, quelle que soit la procedure de collecte de donnees. Nous appliquons l'approche a l'estimation de l'abondance d'adultes dans 18 populations de saumon atlantique (Salmo salar) de Bretagne (France) de 1987 a 2017, en utilisant des statistiques sur les prises, des covariables faisant l'objet d'une surveillance etroite sont aussi integrees a l'analyse. Le cadre de MBH permet le transfert d'information l'abondance des adultes de retour en Bretagne au cours de la periode etudiee. [Traduit par la Redaction], L’estimation de l’abondance à vaste couverture spatiotemporelle est nécessaire pour l’évaluation et la gestion de populations d’animaux sauvages. Dans de nombreux cas, toutefois, les données disponibles pour l’estimation de séries chronologiques d’abondance prennent différentes formes, sont de qualité variable dans le temps et l’espace et ont été obtenues par différentes procédures. Nous avons élaboré une approche de modélisation bayésienne hiérarchique (MBH) pour tirer pleinement parti de l’assemblage varié de données disponibles pour estimer des séries chronologiques homogènes d’abondance, quelle que soit la procédure de collecte de données. Nous appliquons l’approche à l’estimation de l’abondance d’adultes dans 18 populations de saumon atlantique (Salmo salar) de Bretagne (France) de 1987 à 2017, en utilisant des statistiques sur les prises, des covariables environnementales et l’effort de pêche. D’autres données sur l’abondance totale ou partielle obtenues pour quatre populations faisant l’objet d’une surveillance étroite sont aussi intégrées à l’analyse. Le cadre de MBH permet le transfert d’information sur des populations étroitement surveillées aux autres populations. Nos résultats ne font ressortir aucune tendance nette de l’abondance des adultes de retour en Bretagne au cours de la période étudiée. [Traduit par la Rédaction]

International audience

International audience; Although freshwater fish stocking is widely used by managers, quantitative assessments of stocking practices are lacking in many countries. The general objective of the present study was to determine the quantity and characteristics of fish stocking in metropolitan France. Using a survey‐based approach, stocking practices for 2013 by recreational angling clubs in France were quantified, which represented the bulk of fish stocking undertaken in that year. Stocking was found to be practiced by 88.6% of angling clubs in France, representing, on average, 65% of their annual budget. Overall, 22 species were stocked, including 13 native and nine non‐native species, with strong variations among species in terms of life stages and body sizes used for stocking. Using Bayesian modelling, a total biomass of 2.029 t, representing approximately 90 million fishes, was estimated to be stocked in France in 2013. In terms of biomass, the most widely stocked species were rainbow trout Oncorhynchus mykiss (Walbaum), brown trout Salmo trutta L., roach Rutilus rutilus (L.), common carp Cyprinus carpio L. and northern pike Esox lucius L. A stocking volume of approximately 60 fishes or 1.5 kg of fish biomass per angler per year seems commonplace in industrialised countries for which data are available

Use of fast-growing domesticated and/or genetically-modified strains of fish is becoming increasingly common in aquaculture, increasing the likelihood of deliberate or accidental introductions into the wild. To date, their ecological impacts on ecosystems remain to be quantified. Here, using a controlled phenotype manipulation by implanting growth hormone in juvenile Atlantic salmon (Salmo salar), we found that growth-enhanced fish display changes in several phenotypic traits known to be important for ecosystem functioning such as habitat use, morphology and excretion rate. Further, these phenotypic changes were associated with significant impacts on the invertebrate community and key stream ecosystem functions such as primary production and leaf-litter decomposition. These findings provide novel evidence that introductions of growth-enhanced fish into the wild can affect the functioning of natural ecosystems and represent a form of intraspecific invasion. Consequently, environmental impact assessments of growth-enhanced organisms need to explicitly consider ecosystem-level effects. This article is protected by copyright. All rights reserved.

Water warming induced by human activities can impact fish larvae survival, notably because it influences larval development and prey abundances. Amphidromous gobies of the subfamily Sicydiinae are particularly sensitive to this threat as the newly hatched free embryos are poorly developed and the first feeding opportunity only occurs after they reach the ocean. Here, we studied how water temperature (21, 23, 25, 29 and 31 degrees C) impacts early development stages of Sicyopterus lagocephalus in both freshwater and marine aquaria (salinity 35). We monitored survival time, larval condition and the occurrence of critical developmental events such as mouth opening, yolk sac and oil globule resorption. In freshwater, the survival exceeded 150 hours at 21 degrees C, while it dropped below 50 hours at 31 degrees C. In seawater, the larval development of unfed larvae was significantly affected by temperature, survival time being greatly reduced in warmer waters. Accounting for the observed duration between mouth opening and the resorption of the oil globule, we estimated that larvae need to find suitable prey in seawater within a short time: around 30 hours during the peak of reproduction in summer. Otherwise, their endogenous reserves become depleted and their condition degrades. This study emphasises the sensitivity of free embryos to stream flow alterations, which contributes to the increase in water temperature and to the slowing down of larvae drift to the ocean. We conclude that once in seawater the temperature and feeding conditions experienced by amphidromous larvae are critical for survival.

The evolution of choosiness has a strong effect on sexual selection, as it promotes variance in mating success among individuals. The context in which choosiness is expressed, and therefore the associated gain and cost, is highly variable. An overlooked mechanism by current models is the rapid fluctuations in the availability and quality of partners, which generates a dynamic mating market to which each individual must optimally respond. We argue that the rapid fluctuations of the mating market are central to the evolution of optimal choosiness. Using a dynamic game approach, we investigate this hypothesis for various mating systems (characterized by different adult sex ratio and latency period combinations), allowing feedback between the choosiness and partner availability throughout a breeding season while taking into account the fine variation in individual quality. Our results indicate that quality-dependent and flexible choosiness usually evolve in both sexes for various mating systems and that a significant amount of variance in choosiness is observed, especially in males, even when courtship is costly. Accounting for the fluctuating dynamics of the mating market therefore allows envisioning a much wider range of choosiness variation in natural populations and may explain a number of recent empirical results regarding choosiness in the less common sex or its variance within sexes; L’évolution de la sélectivité lors du choix du partenaire augmente la variance de succès reproducteur entre les individus, ce qui affecte la sélection sexuelle. Le contexte dans lequel s’exprime le choix est très variable, ce qui modifie le bénéfice et le coût qui y sont associés. Les modèles actuels négligent souvent l’existence de fluctuations rapides dans la disponibilité et la qualité des partenaires, ce qui génère un « marché biologique » pour l’accouplement auquel chaque individu doit répondre de manière optimale. Ces fluctuations rapides du marché nous paraissent essentielles à prendre en compte pour prédire l’évolution de la sélectivité dans le choix. En utilisant une approche de théorie des jeux, nous testons cette hypothèse pour différents systèmes reproducteurs (caractérisés par des combinaisons différentes de sex-ratio et de temps de latence suivant une reproduction). Cette approche permet de tenir compte de l’effet du choix des individus sur la disponibilité des partenaires tout au long d’une saison de reproduction, tout en représentant finement la variation de qualité des individus. Nos résultats indiquent que la sélectivité du choix dépend de la qualité des individus et est flexible, et elle évolue dans les deux sexes pour les différents systèmes reproducteurs explorés. En outre, une grande variance inter-individuelle de sélectivité est observée, en particulier chez les mâles, même lorsque l’accès au partenaire sexuel engendre un coût direct. Cette prise en compte de l’existence de fluctuations rapides dans la qualité et la quantité des partenaires sexuels génère une forte variance dans la sélectivité en fonction du sexe, du temps et de la qualité, supérieure à ce qui était précédemment prédit. Ces prédictions pourraient expliquer certains résultats empiriques récents concernant le choix chez le sexe rare ou la variance inter-individuelle du choix

Nest building relates to reproductive effort, sexual selection, intersexual conflict and cooperation and may be linked to individual phenotype and interindividual interactions. In particular, larger individuals having more energy reserves are expected to build more, larger nests, without having to trade intrasexual competition for cooperative nest building. Capture-mark-recapture and nest survey of sea lamprey (Petromyzon marinus L. 1758) were combined to assess the relationship between individuals and nesting activity on a spawning ground, throughout a breeding season, during which 202 nests were observed and 114 individuals were captured. On average, males and females stayed 8.33 ± 1.02 and 3.57 ± 1.04 days on the spawning ground, visited 2.26 ± 1.72 and 1.67 ± 1.17 nests and encountered 2.33 ± 2.13 mates for males and 2.29 ± 1.32 mates for females, respectively, and the number of mates encountered increased with the number of nests visited. Body size had no effect on the duration of presence on spawning ground, number of nests visited, number of individuals per nest and sex ratio on nest or nest volume. Bigger nests were found at the end of the season and were not necessarily built by more individuals. This work brings insights on the mating system and cooperative nest building in sea lamprey and may inform managers who want to estimate sea lamprey populations via nest surveys.

International audience; Dramatic increases in global mercury pollution require a deeper understanding of specific toxicity mechanisms for mercury compounds in organisms. Despite numerous studies addressing mercury toxicity, the detailed mechanisms underlying its transport and accumulation in fish remain unclear. The aim of this study was to unravel differential uptake pathways for mercury compounds, metabolisation, and sequestration mechanisms in glass eels using techniques able to localize at the tissue and organ levels. A multi isotope image mapping procedure was developed to simultaneously study the uptake and distribution of both mercury compounds MeHg and Hg(II) within the organs of the whole organism. The use of isotopically labelled Hg species (methylmercury Me201Hg and inorganic mercury 199Hg(II) and image based on isotope ratio instead of elemental signals allowed to visualize spatially and with time the differential Hg species uptake, transport, and sequestration routes. The results showed a preferential uptake of the MeHg counterpart and a dynamic transport of MeHg within different organs. The gills were the main target organs for MeHg uptake, whereas the skeletal muscle was the final MeHg storage tissue. Hg(II) was found to mainly transit by the gills and the olfactory bulbs with a very low transfer and storage in the other organs and a rapid depuration. No significant internal demethylation and methylation was observed during this experimentation.

A preprint peer-reviewed and recommended by Peer Community In Evolutionary Biologyhttps://evolbiol.peercommunityin.org/; Sexual selection has long been known to favor the evolution of mating behaviors such as mate preference and competitiveness, and to affect their genetic architecture, for instance by favoring genetic correlation between some traits. Reciprocally, genetic architecture can affect the expression and the evolvability of traits and mating behaviors. But sexual selection is highly context-dependent, making interactions between individuals a central process in evolution, governing the transmission of genotypes to the next generation. This loop between the genetic structure conditioning the expression and evolution of traits and behaviour, and the feedback of this phenotypic evolution on the architecture of the genome in the dynamic context of sexual selection, has yet to be thoroughly investigated. We argue that demogenetic agent-based models (DG-ABM) are especially suited to tackle such a challenge because they allow explicit modelling of both the genetic architecture of traits and the behavioural interactions in a dynamic population context. We here present a DG-ABM able to simultaneously track individual variation in traits (such as gametic investment, preference, competitiveness), fitness and genetic architecture throughout evolution. Using two simulation experiments, we compare various mating systems and show that behavioral interactions during mating triggered some complex feedback in our model, between fitness, population demography, and genetic architecture, placing interactions between individuals at the core of evolution through sexual selection. DG-ABMs can, therefore, relate to theoretical patterns expected at the population level from simpler analytical models in evolutionary biology, and at the same time provide a more comprehensive framework regarding individual trait and behaviour variation, that is usually envisioned separately from genome architecture in behavioural ecology

International audience

International audience; Electrofishing in streams of low water conductivity has technical limitations leading to the widespread use of poison fishing. In theory, provided a high enough voltage gradient can be created in water, electrofishing should be possible in all but the lowest of conductivities (

The fast-start escape response is the main locomotor behaviour observed in fish to evade predatory attacks and thereby increase their probability of survival. Thus far, this high-speed sensory motor control has been extensively studied in relation to extrinsic factors. In contrast, there has been surprisingly little consideration of intrinsic individual factors that can mediate sensorial perception, such as inter-individual variability in mechanosensory systems. The inner ear of teleost fishes is composed of otoliths that play an important role in hearing and balance functions. While sagittal otoliths are normally composed of aragonite in many fish species, the inclusion of vaterite (an abnormal crystalline structure) has been reported in a number of individuals from different environments. There is currently strong theoretical and empirical evidence that vaterite deposition has a negative impact on auditory sensitivity in fishes. While the functional/behavioural implications of this defect on otolith-related hearing function has been hypothesised, it has remained largely untested experimentally. Here, using juvenile (0+ years) Salmo trutta originating from the wild in experimental conditions, we report for the first time that the deposition of calcium carbonate in its crystalline vateritic polymorph has significant pervasive effects on the escape kinematics of fish. The presence of an alternative crystalline structure in otoliths is likely to alter fish behaviour in ways that decrease survival. We also report that altered behaviour in individuals with vateritic otoliths is partially compensated for by the presence of a functional lateral line. Such functional compensation suggests more slight consequences, if any, in the wild.

International audience

Le présent rapport fait un point d’avancement à 24 mois du projet RENOSAUM qui vise à refondre la stratégie de gestion des populations de saumon en Bretagne. Il répertorie factuellement les actions et travaux entrepris au cours des 12 derniers mois, en les situant par rapport au plan prévisionnel initial. Il fournit également en annexe les trois livrables prévus avant la fin de l’année 2019.

La lamproie marine présente des enjeux de conservation divers, de la préservation de sonhabitat dans les régions du monde où elle est protégée, à son extermination dans cellesoù elle est invasive, en passant par la gestion des prélèvements là où elle est exploitée.Dans toutes ces situations, une estimation fiable de l’effectif de géniteurs permet d’adapterla gestion. Le dénombrement des nids sur les frayères est un indicateur relativement aiséà obtenir, mais il est considéré comme peu fiable car la relation entre le nombre de nids etle nombre de géniteurs sur un cours d’eau n’est pas clairement établie. Dans ce rapport,nous présentons une étude réalisée en mai et juin 2019 sur une frayère de la Nive, unaffluent de l’Adour (64), visant à mieux comprendre la relation entre les nids de lamproiemarine et le nombre de géniteurs qui les construisent.Un suivi des nids et un modèle de capture-marquage-recapture ajusté à l’histoire decapture de 114 individus indique que 155 [146-164] lamproies étaient présentes et avaientcreusé 202 nids. Une recherche bibliographique nous a fourni neuf autres mesuresconjointes d’effectif et de nids, nous permettant de mettre en évidence une relationpuissance entre les deux variables, mais l’intervalle de prédiction de la relation est troplarge pour fournir une estimation précise de l’effectif de géniteurs à partir dudénombrement des nids. La combinaison du marquage des lamproies et du suivi des nidsa permis de montrer que les mâles visitaient entre un et dix nids (moyenne = 2,25) et lesfemelles entre un et sept (moyenne = 1,67), bien que ces chiffres soient certainementsous-estimés. Le nombre d’individus par nid suivait la distribution habituelle, la majoritédes nids étant occupés par un mâle et une femelle, et pouvant atteindre sept individus(quatre mâles et trois femelles ou deux mâles et cinq femelles). Parmi les nombreusesmesures prises sur 74 nids, seul le diamètre augmentait avec le nombre de femelles surle nids, et également avec le délai depuis le début de la saison. Le diamètre des nidspourrait alors apporter de l’information dans une méthode d’estimation du nombred’individus à partir de l’observation des nids.Les résultats sont prometteurs dans l’optique de construire un modèle d’estimation del’effectif de géniteurs à partir de l’observation des nids. Cependant, des observations plusdenses sur le nombre de nids fréquentés par chaque individu et sur le nombre d’individuscontribuant vraiment à la construction d’un nid seront certainement nécessaires pourconstruire un modèle simulant correctement le comportement de construction des nids, àpartir duquel on inférera le nombre de géniteurs.

International audience; A major challenge in understanding the response of populations to climate change is to separate the effects of local drivers acting independently on specific populations, from the effects of global drivers that impact multiple populations simultaneously and thereby synchronize their dynamics. We investigated the environmental drivers and the demographic mechanisms of the widespread decline in marine survival rates of Atlantic salmon (Salmo salar) over the last four decades. We developed a hierarchical Bayesian life cycle model to quantify the spatial synchrony in the marine survival of 13 large groups of populations (called stock units, SU) from two continental stock-groupings (CSG) in North America (NA) and Southern Europe (SE) over the period 1971-2014. We found strong coherence in the temporal variation in post-smolt marine survival among the 13 SU of NA and SE. A common North Atlantic trend explains 37% of the temporal variability of the survivals for the 13 SU and declines by a factor 1.8 over the 1971-2014 time series. Synchrony in survival trends is stronger between SU within each CSG. The common trends at the scale of NA and SE capture 60% and 42% of the total variance of temporal variations, respectively. Temporal variations of the post-smolt survival are best explained by the temporal variations of sea surface temperature (SST, negative correlation) and net primary production indices (PP, positive correlation) encountered by salmon in common domains during their marine migration. Specifically, in the Labrador Sea/Grand Banks for NA populations 26% and 24% of variance is captured by SST and PP, respectively and in the Norwegian Sea for SE populations 21% and 12% of variance is captured by SST and PP, respectively. The findings support the hypothesis of a response of salmon populations to large climate induced changes in the North Atlantic simultaneously impacting populations from distant continental habitats.

International audience; We assessed the effects of sexual maturity on space use in Atlantic salmon (Salmo salar) parr as facultative early maturation enables us to work on individuals belonging to the same cohort. We monitored the space use of 40 1-year-old males in natura throughout a breeding season. First, mature individuals covered longer distances (absolute and upstream) and located within broader home ranges than immature parr. Second, sexual maturity also generated a higher interindividual variability in space use. Finally, mature individuals exhibited a higher probability of association with likely breeding sites on average. However, some mature individuals experienced a lower probability than immature individuals, suggesting that the space use of some mature individuals may not be optimal. Moreover, mature parr exploiting a broader home range or covering longer upstream distances had a higher probability of association with likely breeding sites. Covering longer upstream distances may therefore increase the reproductive success of mature parr, while involving higher energetic costs and a greater risk of predation

International audience; Marine predators feeding on fisheries catches directly on the fishing gear, a behaviour termed “depredation”, has emerged as a major human-wildlife conflict globally, often resulting in substantial socio-economic and ecological impacts. This study investigated the extent of this conflict in commercial Patagonian toothfish (Dissostichus eleginoides) fisheries across subantarctic waters where both killer whales (Orcinus orca) and sperm whales (Physeter macrocephalus) feed on toothfish caught on longline hooks. Using long-term datasets from six major fishing areas, from southern Chile to the Indian Ocean sector of the Southern Ocean, statistical models were developed to quantify the catch removals due to whale depredation interactions. The results indicated that these removals were large, totalling more than 6600 t of toothfish between 2009 and 2016 with an annual mean of 837 t [95% CI 480–1195 t], comprised of 317 t [232–403 t] and 518 t [247–790 t] removed by killer whales and sperm whales, respectively. Catch removals greatly varied between areas, with the largest estimates found at Crozet, where on average 279 t [179–379 t] of toothfish per year, equivalent to 30% [21–37%] of the total catches. Together, these findings provide metrics to assess the impacts of depredation interactions on the fishing industry, whale populations, fish stocks and associated ecosystems. With an estimated $15 M USD worth of fish depredated every year, this study highlights the large geographic scale and economic significance of the depredation issue and its potential to compromise the viability of some toothfish fisheries which are the primary socio-economic activity in subantarctic regions.

International audience; The effect of methylmercury (MeHg) was investigated in glass eel migration behavior and metabolism. To migrate up estuary, glass eels synchronize their swimming activity to the flood tide and remain on or in the substratum during ebb tide. Following seven days of exposure to MeHg (100 ng L-1), glass eels migration behavior was expressed by their swimming synchronization to the water current reversal every 6.2 h (mimicking the alternation of flood and ebb tides) and their swimming activity level. In relation to their behavior, we then analyzed the energy-related gene expression levels in individual head, viscera and muscle. Results showed that MeHg decreased the number of glass eels synchronized to the change in water current direction and their swimming activity level. This last effect was more pronounced in non-synchronized fish than in synchronized ones, supporting the idea that nonsynchronized glass eels could be more vulnerable to stress. As regard the expression of energy-related genes, no significant difference was observed between control and MeHg-exposed fish. In contrast,when the swimming activity levels were plotted against transcriptional responses, positive correlations were evidenced in viscera and especially in the head of exposed glass eels but not in control. Finally, it is noteworthy that non-synchronized glass eels displayed lower expression level of metabolism genes than their synchronized counterpart, but only in the head. Altogether, these results support the interest of focusing on the head to investigate the facultative migration behavior in glass eels and the effect of environmental stressors on this rhythmic behavior

International audience; Subsequent to their introduction in the 1950s, Arctic charr Salvelinus alpinus have been able to establish a self‐sustaining population that has adapted to the unique conditions of the sub‐Antarctic Kerguelen Islands. Here, 48 individuals (198–415 mm) were caught with gillnets and their basic biology and feeding ecology were examined using stable isotope analysis. The Lac des Fougères population split use of littoral and pelagic resources evenly, although larger fish relied more heavily on littoral production and appear to follow the size‐dependent life history habitat template seen in many Scandinavian lakes where smaller sized individuals occupy the pelagic zone and larger individuals dominate the littoral habitat. In Kerguelen, Arctic charr mature at the same ages (5.6 years) as Arctic charr in both sub‐Arctic and Arctic lakes. Although mortality was average in comparison to comparator sub‐Arctic lakes, it was high in comparison to Arctic lakes. Maximal age (>7+) was at the lower end of the range typically seen in sub‐Arctic lakes. Although they inhabit a resource‐poor environment, Kerguelen Arctic charr showed no evidence of cannibalism. Thus, while Arctic charr can survive and reproduce in the relatively unproductive Kerguelen lake environments, survival and growth nevertheless appear to be traded off against survival and longevity. The uniqueness of the population location and the recency of its introduction suggest that further monitoring of the population has the potential to yield valuable insights into both the adaptability of the species and its likely responses to ongoing large‐scale environmental change as represented by climate change

Dans la perspective de mieux comprendre le rôle de la dispersion dans la conservation des populations de saumon Atlantique face aux pressions environnementales et anthropiques qu’ils subissent, il est vital de quantifier la part relativedes migrants des populations. Pour répondre à cet enjeu, ce projet a eu pour objectif d’évaluer le potentiel de la microchimie des écailles comme outil non-léthal permettant de déterminer l’origine spatiale (rivière natale) des individus. Une telle avancée doit permettre un retour historique sur les larges banques de données scalimétriques existantes alors que les banques d'otolithes sont beaucoup plus restreintes, tant spatialement que temporellement.Durant ce projet, nous avons évalué le potentiel de l’analyse microchimique élémentaire (Sr, Ba, Mn, Mg, Zn, …) des écailles de saumon Atlantique (Salmo salar) pour déterminer l’origine spatiale des individus. Pour ce faire, nous effectuerons une analysecomparative des éléments microchimiques entre otolithes (méthode de référence) et écailles dans le but d’évaluer 1) l’importance des effets de l’altération des signatures géochimiques contenues dans les écailles lors du séjour en mer (contrairement à l’otolithe dans lequel les signatures sont inertes, celles des écailles pourraient subir des modifications dans le temps), et 2) la pertinence de l’écaille pour déterminer l’origine spatiale des individus. À partir de saumon prélevés sur deux zones géographiques en France (bassin Adour-Nivelle et rivières Finistère Sud) et pour lesquels nous disposions à la fois des otolithes (dont la plupart ont été déjà analysés avec attribution d’une origine natale précise pour chaque individu) et des écailles, nous pouvons conclure que la microchimie des écailles provenant d'individus anadrome possède de très faibles performances, sans comparaison possible avec celles obtenues à l'aide des otolithes.Cette différence de performance repose principalement sur l’altération des signatures chimiques de l’écaille lors du passage en mer, se traduisant par un très forte atténuation des signatures natales