Vincennes, France
Vincennes, France
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Colas F.,Ecolab | Baudoin J.-M.,IRSTEA | Gob F.,Paris-Sorbonne University | Tamisier V.,Paris-Sorbonne University | And 4 more authors.
Water Research | Year: 2017

Physical habitat degradation is prevalent in river ecosystems. Although still little is known about the ecological consequences of altered hydromorphology, understanding the factors at play can contribute to sustainable environmental management. In this study we aimed to identify the hydromorphological features controlling a key ecosystem function and the spatial scales where such linkages operate. As hydromorphological and chemical pressures often occur in parallel, we examined the relative importance of hydromorphological and chemical factors as determinants of leaf breakdown. Leaf breakdown assays were investigated at 82 sites of rivers throughout the French territory. Leaf breakdown data were then crossed with data on water quality and with a multi-scale hydromorphological assessment (i.e. upstream catchment, river segment, reach and habitat) when quantitative data were available. Microbial and total leaf breakdown rates exhibited differential responses to both hydromorphological and chemical alterations. Relationships between the chemical quality of the water and leaf breakdown were weak, while hydromorphological integrity explained independently up to 84.2% of leaf breakdown. Hydrological and morphological parameters were the main predictors of microbial leaf breakdown, whereas hydrological parameters had a major effect on total leaf breakdown, particularly at large scales, while morphological parameters were important at smaller scales. Microbial leaf breakdown were best predicted by hydromorphological features defined at the upstream catchment level whereas total leaf breakdown were best predicted by reach and habitat level geomorphic variables. This study demonstrates the use of leaf breakdown in a biomonitoring context and the importance of hydromorphological integrity for the functioning of running water. It provides new insights for environmental decision-makers to identify the management and restoration actions that have to be undertaken including the hydromorphogical features that should be kept in minimal maintenance to support leaf breakdown. © 2017 Elsevier Ltd

Dauphin G.J.R.,French National Institute for Agricultural Research | Dauphin G.J.R.,University of New Brunswick | Brugel C.,ONEMA | Legrand M.,Logrami | Prevost E.,French National Institute for Agricultural Research
Canadian Journal of Fisheries and Aquatic Sciences | Year: 2017

Salmonid juvenile stocking programs are often poorly monitored due to the lack of identification between stocked and wild fish. In this study, a hierarchical Bayesian model is developed to take advantage of spatiotemporal variations of stocking and wild recruitment for estimating these two components despite the absence of identification data. It is first tested by means of simulated data and then applied to the 37 year abundance data set of the Atlantic salmon (Salmo salar) population of the Allier catchment (France). Despite the absence of identification data, juvenile densities could be estimated and split into wild and stocked components. We found that the stocked juveniles contributed significantly to the total juvenile production, while the wild reproduction continued to provide an important contribution. This approach is encouraging and promising from a management advice perspective. It is flexible enough to accommodate for case study specificities and shows that long-term monitoring abundances can be useful to assess the impact of stocking programs even in the absence of direct means of identifying stocked versus wild fish. © 2017 Canadian Science Publishing. All rights reserved.

Dekker W.,Swedish University of Agricultural Sciences | Beaulaton L.,ONEMA | Beaulaton L.,French National Institute for Agricultural Research
ICES Journal of Marine Science | Year: 2015

Few fish stocks are as influenced by (intentional and inadvertent) human impacts as the European eel, all across the continent. The dynamics of this stock, however, are poorly understood - neither the causes of the historically low abundance, nor minimal protection levels, are beyond discussion. Rather than analysing contemporary processes, this article turns back in time - two centuries or more - unravelling historical abundances and distribution patterns; reviewing historical actions and objectives; and discussing technical developments and scientific advice - picturing the slippery slope the eel stock has come down from. The first claim, that the continental stock was in decline, dates from the early 1800s; stock-enhancement actions were initiated shortly after. Diffuse objectives, technical innovations, eternal optimism, and - above all - no quantification impede the exact evaluation of historical reports. After 1950, when quantification improved, a slow but consistent decline was observed, but it is only two decades after the crash in glass eel recruitment (in 1980), that protection plans addressed the bad status of the stock. A slippery slope, full of pitfalls - yet, we now observe several years of increasing recruitment. © 2015 International Council for the Exploration of the Sea 2015. All rights reserved.

Daverat F.,IRSTEA | Beaulaton L.,ONEMA | Poole R.,Marine Institute of Ireland | Lambert P.,IRSTEA | And 7 more authors.
Ecology of Freshwater Fish | Year: 2012

A cooperative effort gathered a large European length-at-age data set (N=45,759, Lat. 36S-61N Long. 10W-27E) for Anguilla anguilla, covering one century. To assess the effect of global warming during the last century and habitat effects on growth, a model was fitted on the data representing the conditions met at the distribution area scale. Two GLMs were designed to predict eel log(GR): one model was fitted to the whole data and the other was fitted to the female data subset. A model selection procedure was applied to select the best predictors among sex, age class, five temperature parameters and six habitat parameters (depth, salinity and four variables related to the position in the catchment). The yearly sum of temperatures above 13°C (TempSUP13), the relative distance within the catchment, sex, age class, salinity class and depth class were finally selected. The best model predicted eel log(GR) with a 64.46% accuracy for the whole data and 66.91% for the female eel data. Growth rate (GR) was greater in habitats close to the sea and in deep habitats. TempSUP13 variable had one of the greatest predictive powers in the model, showing that global warming had affected eel growth during the last century. © 2012 John Wiley & Sons A/S.

PubMed | CNRS Training and Research Center on Mediterranean Environments, French National Institute for Agricultural Research and Onema
Type: | Journal: Scientific reports | Year: 2016

Environmental sex determination (ESD) has been detected in a range of vertebrate reptile and fish species. Eels are characterized by an ESD that occurs relatively late, since sex cannot be histologically determined before individuals reach 28cm. Because several eel species are at risk of extinction, assessing sex at the earliest stage is a crucial management issue. Based on preliminary results of RNA sequencing, we targeted genes susceptible to be differentially expressed between ovaries and testis at different stages of development. Using qPCR, we detected testis-specific expressions of dmrt1, amh, gsdf and pre-miR202 and ovary-specific expressions were obtained for zar1, zp3 and foxn5. We showed that gene expressions in the gonad of intersexual eels were quite similar to those of males, supporting the idea that intersexual eels represent a transitional stage towards testicular differentiation. To assess whether these genes would be effective early molecular markers, we sampled juvenile eels in two locations with highly skewed sex ratios. The combined expression of six of these genes allowed the discrimination of groups according to their potential future sex and thus this appears to be a useful tool to estimate sex ratios of undifferentiated juvenile eels.

Blanchet S.,French National Center for Scientific Research | Blanchet S.,CNRS Biological Evolution and Diversity Laboratory | Reyjol Y.,ONEMA | April J.,Laval University | And 4 more authors.
Global Ecology and Biogeography | Year: 2013

Aim: We investigated the relationship between geographic range size (GRS), longitude and latitude (Rapoport's rule) in Canadian freshwater fishes. We tested hypotheses regarding the phenotypic and phylogenetic determinants of GRS to unravel processes driving the spatial patterns of GRS in Canada. Because GRS is negatively correlated with extinction risk, we also aimed at identifying biological proxies that may be used to predict extinction risks. Location: North-America, Canadian Shield. Methods: We built a database combining range area, seven ecological traits, and a molecular phylogeny for native Canadian freshwater fishes. We tested latitudinal and longitudinal patterns in GRS by the mean of Pearson correlations. We combined phylogenetic generalized least squares (PGLS) models and a model selection procedure to tease apart hypotheses (and hence ecological traits) that best explained GRS in our dataset. PGLSs were also used to explore relationships between ecological traits, phylogeny, and species mid-range latitude and longitude. Partial regressions were used to determine direct and indirect relationships driving spatial patterns of GRS in Canadian freshwater fishes. Results: There was a significant and positive correlation between GRS, latitude and longitude. According to PGLSs, three ecological traits, related to the habitat use, migratory and thermal tolerance hypotheses, were significantly correlated with GRS, mid-range longitude and mid-range latitude. Two traits related to locomotion were further related to GRS. There was no phylogenetic effect on GRS (i.e. no phylogenetic conservatism). Partial regressions revealed complex direct and indirect relationships between ecological traits, mid-range latitude, mid-range longitude and GRS. Main conclusions: Our results show that traits related to the ability to use dispersal corridors, as well as traits directly related to mobility, are useful in understanding biodiversity patterns such as Rapoport's rule. However, because of a weak explanatory power, we conclude that using biological proxies of GRS to predict species at risk of extinction would be premature. © 2013 John Wiley & Sons Ltd.

Loot G.,CNRS Biological Evolution and Diversity Laboratory | Poulet N.,ONEMA | Brosse S.,CNRS Biological Evolution and Diversity Laboratory | Tudesque L.,CNRS Biological Evolution and Diversity Laboratory | And 3 more authors.
Parasitology | Year: 2011

Objective. Unravelling the determinants of parasite life-history traits in natural settings is complex. Here, we deciphered the relationships between biotic, abiotic factors and the variation in 4 life-history traits (body size, egg presence, egg number and egg size) in the fish ectoparasite Tracheliastes polycolpus. We then determined the factors affecting the strength of the trade-off between egg number and egg size. Methods. To do so, we used 4-level (parasite, microhabitat, host and environment) hierarchical models coupled to a field database. Results. Variation in life-history traits was mostly due to individual characteristics measured at the parasite level. At the microhabitat level (fins of fish hosts), parasite number was positively related to body size, egg presence and egg number. Higher parasite number on fins was positively associated with individual parasite fitness. At the host level, host body size was positively related to the individual fitness of the parasite; parasites were bigger and more fecund on bigger hosts. In contrast, factors measured at the environmental level had a weak influence on life-history traits. Finally, a site-dependent trade-off between egg number and egg size existed in this population. Conclusion. Our study illustrates the importance of considering parasite life-history traits in a hierarchical framework to decipher complex links between biotic, abiotic factors and parasite life-history traits. © Cambridge University Press 2011.

Balaresque P.,University Paul Sabatier | Balaresque P.,University of Leicester | Poulet N.,Onema | Cussat-Blanc S.,French National Center for Scientific Research | And 4 more authors.
European Journal of Human Genetics | Year: 2015

High-frequency microsatellite haplotypes of the male-specific Y-chromosome can signal past episodes of high reproductive success of particular men and their patrilineal descendants. Previously, two examples of such successful Y-lineages have been described in Asia, both associated with Altaic-speaking pastoral nomadic societies, and putatively linked to dynasties descending, respectively, from Genghis Khan and Giocangga. Here we surveyed a total of 5321 Y-chromosomes from 127 Asian populations, including novel Y-SNP and microsatellite data on 461 Central Asian males, to ask whether additional lineage expansions could be identified. Based on the most frequent eight-microsatellite haplotypes, we objectively defined 11 descent clusters (DCs), each within a specific haplogroup, that represent likely past instances of high male reproductive success, including the two previously identified cases. Analysis of the geographical patterns and ages of these DCs and their associated cultural characteristics showed that the most successful lineages are found both among sedentary agriculturalists and pastoral nomads, and expanded between 2100 BCE and 1100 CE. However, those with recent origins in the historical period are almost exclusively found in Altaic-speaking pastoral nomadic populations, which may reflect a shift in political organisation in pastoralist economies and a greater ease of transmission of Y-chromosomes through time and space facilitated by the use of horses. © 2015 Macmillan Publishers Limited. All rights reserved.

Tomanova S.,Delegation Interregionale Center | Tedesco P.A.,French Natural History Museum | Roset N.,ONEMA | Berrebi dit Thomas R.,ONEMA | Belliard J.,IRSTEA
Fisheries Management and Ecology | Year: 2013

Compared with small rivers and streams, the study of fish communities in large rivers remains challenging as spatial and temporal data variability can be greatly influenced by sampling strategy and operator choice. In an attempt to limit this variability, a new sampling protocol for fish communities in medium- to large-sized rivers was developed, based on point sampling by electric fishing and using standardised procedures and effort. Here, change in data quality (assemblage abundance, richness, structure and biotic index) with increasing sampling effort (from 1 to 100 sampling points) was evaluated. A total of 75 sampling points are proposed as the standard number of samples per site. Broadly, the results show that the application of 75 sampling points provides a reproducible representation of fish community structure in medium and large rivers, with little additional information provided by further sampling except under certain conditions, when 100 points are recommended to maintain data quality. © 2013 John Wiley & Sons Ltd.

Rejiba F.,CNRS Transfers and Interactions in Hydrosystems and Soils | Bobee C.,CEA Saclay Nuclear Research Center | Maugis P.,ONEMA | Camerlynck C.,CNRS Transfers and Interactions in Hydrosystems and Soils
Journal of Applied Geophysics | Year: 2012

Local agriculture in Senegal is dependent on truck farming, which is concentrated in the narrow interdunal zone of peat deposits, called "niayes". The viability of the niayes significantly depends on the sand dune aquifer, as a consequence of recent over-pumping. In the present paper, we discuss the ability of GPR to locate the water table, in a highly vegetated interdunal area which includes peat fields, as well as internal dips, which were shown to be complex. Three profiles determined in the interdunal zone have been associated with several boreholes. Analysis of the radargrams clearly shows that 1) the presence of dense vegetation is not a penalising factor; 2) phase inversion in the measured signal could be useful in distinguishing between the presence of a significant water contrast, and that of a strong stratigraphic reflector; 3) in sand dunes, the electromagnetic contrast resulting from a wetting front is likely to be of the same order as that of the water table. The outcome of this study may provide clues to the characterisation and management of water resources in niayes area. © 2011 Elsevier B.V..

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