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Castanet-Tolosan, France

Roussiez V.,French National Center for Scientific Research | Ludwig W.,French National Center for Scientific Research | Radakovitch O.,Aix - Marseille University | Probst J.-L.,INP ENSAT | And 3 more authors.
Estuarine, Coastal and Shelf Science | Year: 2011

The dynamics of sediment-bound metals (Cs, Cu, Ni, Pb, Ti and Zn) were studied off the Têt River (western Gulf of Lion), a typical Mediterranean coastal river punctuated by short and violent flash-floods. Spatial and temporal sampling strategies were combined to elucidate the fate of these elements in response to both the riverine sediment input and the offshore transport of these sediments through hydrodynamics. Our results show the temporal entrapment of riverborne particles and associated metals, consecutively to a major flood event, in the nearshore sedimentary unit called prodelta. Here, deposition and resuspension mechanisms define a sedimentological cycle that could be followed completely in this study. In terms of speciation between reactive (labile) and residual fractions along the fluvio-deltaic continuum, our results show that Cu, Pb and Zn are the most labile (potentially mobile) metals in the river, in accordance with their contributions from anthropogenic sources. But in the marine surficial sediments, two main behaviours can be discriminated when compared to the riverine suspended particulate matter. While Pb and Zn depict rather a constant labile fraction, Cu is characterized by decreasing levels (up to 50% difference). In terms of environmental impact, these contrasting trends have direct repercussions for the contaminant dispersal in the coastal area. Whereas Pb and Zn conserve their enhanced levels because of their stronger affinity with fine sediments, Cu is marked by the entire loss of its anthropogenic component that is progressively transferred to the dissolved phase, likely mediated by organic ligands. We ascribe these behaviours to different post-depositional partition mechanisms with respect to oxidation of the particulate organic phase at the bottom sediment/water interface. Also, analysis of one sediment core from the prodelta indicates that these early diagenetic processes govern the chemical forms of land-derived contaminants sequestrated in the nearshore sedimentary archives. © 2011 Elsevier Ltd. Source


Lederoun D.,University of Liege | Lederoun D.,University Abomey Calavi | Vandewalle P.,University of Liege | Brahim A.A.,University Abomey Calavi | And 2 more authors.
African Journal of Aquatic Science | Year: 2016

Growth, mortality, recruitment and relative yield per recruit of Sarotherodon galilaeus galilaeus from Lakes Doukon and Togbadji were studied. Data on total length, total weight and sex were recorded on a monthly basis between January and December 2013 for S. g. galilaeus captured by local fishers. The estimated asymptotic lengths L∞ were 26.2 and 23.6 cm for Lakes Doukon and Togbadji, respectively, while the growth rate K was 0.73 in Lake Doukon and 0.87 in Lake Togbadji. Estimates of fishing mortality, 0.27 and 0.47 y−1 for Doukon and Togbadji, respectively, were low relative to natural mortality, 1.51 and 1.74 y−1, respectively. Sizes at first sexual maturity were 12.8 and 13.2 cm for females and males, respectively, in Lake Doukon, and 11.5 and 12.4 cm for females and males, respectively, in Lake Togbadji. The size at first capture was estimated at 13.3 and 12.7 cm for Lakes Doukon and Togbadji, respectively, which, in the light of the size at maturity estimates, indicates that fish spawn at least once before capture. The current exploitation rates of 0.15 for Lake Doukon and 0.21 for Lake Togbadji suggest that their stocks of S. g. galilaeus are not overexploited in either lake. © 2016 NISC (Pty) Ltd. Source


Niyonkuru C.,University of Burundi | Laleye P.A.,University Abomey Calavi | Moreau J.,INP ENSAT
Knowledge and Management of Aquatic Ecosystems | Year: 2010

In Lake Nokoué fishermen have developed the acadjas system which operates as an extensive aquaculture practice. Little is known about the population dynamics of fish fauna which colonizes those acadjas. Therefore, population parameters of two cichlids of Lake Nokoué, Sarotherodon melanotheron and Hemichromis fasciatus, sampled in areas within and without acadjas were investigated using length-frequency data collected between June 2003 and December 2004. For the two species, asymptotic length, L ∞ was higher within than without acadjas (26.8 cm and 24.1 cm respectively for S. melanotheron; 18.5 cm and 16.5 cm respectively for H. faciatus). K and Φ′ values recorded outside acadjas were higher than inside acadjas for H. fasciatus whereas the same values were very slightly different without and within acadjas for S. melanotheron. H. fasciatus is a fish predator and branches or woody debris of acadjas are not favourable for its hunting activities.The total and natural mortality rates for the two species were higher outside than inside acadjas showing so the role of protection insured by acadjas systems. Acadjas have more impact on H. fasciatus than on S. melanotheron. A possibility of management is to reorganize the distribution of acadjas over Lake Nokoué in order to keep some areas in which no acadjas would be allowed for fish species that growth is better without acadjas. © 2010 ONEMA. Source


Haddadi P.,French National Institute for Agricultural Research | Haddadi P.,University of Tehran | Yazdi-Samadi B.,University of Tehran | Langlade N.B.,French National Institute for Agricultural Research | And 7 more authors.
African Journal of Biotechnology | Year: 2010

The purpose of the present study was to map quantitative trait locus (QTLs) associated with percentage of seed protein, oil and fatty acids content under different conditions in a population of recombinant inbred lines (RILs) of sunflower. Three independent field experiments were conducted with well-, partial-irrigated and late-sowing conditions in randomized complete block design with three replications. High significant variation among genotypes is observed for the studied traits in all conditions. Several specific and non-specific QTLs for the aforementioned traits were detected. Under late-sowing condition, a specific QTL of palmitic acid content on linkage group 6 (PAC-LS.6) is located between ORS1233 and SSL66_1 markers. Common chromosomic regions are observed for percentage of seed oil and stearic acid content on linkage group 10 (PSO-PI.10 and SAC-WI.10) and 15 (PSO-PI.15 and SAC-LS.15). Overlapping occurs for QTLs of oleic and linoleic acids content on linkage groups 10, 11 and 16. Seven QTLs associated with palmitic, stearic, oleic and linoleic acids content are identified on linkage group 14. These common QTLs are linked to HPPD homologue, HuCL04260C001. Coincidence of the position for some detected QTLs and candidate genes involved in enzymatic and non-enzymatic antioxidants would be useful for the function of the respective genes in fatty acid stability. ©2010 Academic Journals. Source


Tsafack N.,CIRAD - Agricultural Research for Development | Tsafack N.,French National Institute for Agricultural Research | Menozzi P.,CIRAD - Agricultural Research for Development | Brevault T.,CIRAD - Agricultural Research for Development | And 3 more authors.
International Journal of Pest Management | Year: 2013

Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) is a polyphagous pest of global importance, threatening several key crops, including cotton. This study analysed the influence of landscape composition and agricultural practices on (i) the abundance of H. armigera larvae, and (ii) the proportion of infested plants (infestation) in cotton fields in northern Benin. In 2011 and 2012, the abundance of H. armigera was monitored during the rainy period, with weekly observations of 50 cotton plants in 20 fields selected each year. We selected cotton fields based upon the composition of the surrounding landscape (cotton, tomato and maize fields, and areas of natural vegetation) within 500 metres radius buffers. We also recorded agricultural practices, included sowing date, crop rotation, and frequencies of weeding and of treatment with insecticides. In testing for a relationship between the pest problem and landscape and management, we fitted logistic multiple regression models and compared all the possible models using an information-theoretic approach. Cotton fields surrounded by cotton crops were found to have significantly higher infestation rates. Natural vegetation was positively correlated with the level of infestation. This study highlights the importance of considering both landscape variables and agricultural practices to improve strategies management of H. armigera. © 2013 Taylor & Francis. Source

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