Consulta: subjectFacets:"Sensibilité"
Registros recuperados: 8
Data/hora: 06/06/2024 13:48:06

Intégrité des habitats benthiques du plateau continental face aux perturbations physiques naturelles et aux arts trainants : quelles méthodes d'observations ? Comment suivre le retour vers un bon état écologique ?
Provedor de dados: 5
Autores: Jac, Cyrielle.
In 2008, the European Union drew up the Marine Strategy Framework Directive (MSFD) with the aim of achieving Good Environmental Status of marine waters. By linking the changes observed to the pressures experienced, this directive is defined as a tool designed to better control environmental degradation factors and to assess their implications. Several descriptors are defined within the framework of MSFD, in particular descriptors 1 relating to the biological diversity of the seabed and 6 relating to the integrity of the seabed (i.e. the quality of its structures and functions). As dragging (trawling and dredging) is the main source of disturbance of continental shelf seabed, it is essential to study its impact. However, its effects depend on several...
Tipo: Text
Palavras-chave: Mégafaune benthique; Méthode d'échantillonnage; Impact de la pêche; Sensibilité; Facteurs environnementaux; Bon état écologique; Benthic megafauna; Sampling methods; Fishing impact; Sensitivity; Natural drivers; Good environmental status.
Ano: 2020
URL: https://archimer.ifremer.fr/doc/00679/79149/81655.pdf

Sensitivity and variance estimators for virtual population analysis and the equilibrium yield per recruit model
Provedor de dados: 5
Autores: Pelletier, Dominique.
Fish stock assessment makes Widespread use of Virtual Population Analysis (VPA) and long-term equilibrium prediction models. Although there have been some statistical investigations about the properties of VPA results, apparently there are no complete analyse about predictions statistical and numerical behaviour. However, management decisions generally rely upon production forecasts. This paper compares stability properties of VPA and the yield per recruit model with regard to various errors concerning all the input parameters. Robustness fis assessed by means of first-ordo sensitivities whereas variances are inferred from delta-method estimators. Sensitivity of yield per recruit appears to be mainly due to terminal mortality rate and age-specific weights,...
Tipo: Text
Palavras-chave: Analyse de population virtuelle; Rendement par recrue; Sensibilité; Estimation de la variance; Méthode Delta; Virtual Population Analysis; Yield per recruit; Sensitivity; Variance estimation; Delta-method.
Ano: 1990
URL: http://archimer.ifremer.fr/doc/00189/30068/28556.pdf

Differences in performance among four indices used to evaluate diversity in planktonic ecosystems
Provedor de dados: 5
Autores: Beaugrand, G; Edwards, M.
The performance of four common estimators of diversity are investigated using calanoid copepod data from the Continuous Plankton Recorder (CPR) survey. The region of the North Atlantic and the North Sea was divided into squares of 400 nautical miles for each 2-month period. For each 144 possible cases, Pielou's pooled quadrat method was performed with the aims of determining asymptotic diversity and investigating the CPR sample-size dependence of diversity estimators. It is shown that the performance of diversity indices may greatly vary in space and time (at a seasonal scale). This dependence is more pronounced in higher diverse environments and when the sample size is small. Despite results showing that all estimators underestimate the 'actual'...
Tipo: Text
Palavras-chave: Programme continuous plankton recorder; Copépodes; Indices de diversité; Taille de l’échantillonnage; Sensibilité; Continuous Plankton Recorder survey; Copepods; Diversity indices; Sample size; Sensitivity.
Ano: 2001
URL: http://archimer.ifremer.fr/doc/00322/43343/42884.pdf

Les méthodes delta en halieutique. Evaluation des sensibilites, approximation des biais et variances à l'aide de developpements limites
Provedor de dados: 5
Autores: Laurec, Alain.
This report presents an introduction to so called "delta methods", associated to the use of Taylor's expansions, as a tool for sensitivity analyses. It starts with a mathematical and statistical summary about Taylor's expansion and moments of random variâtes. Special attention is paid to multivariate problems. The application of order 1 and 2 expansions to estimate variances and biases is exposed in great details. This report dedicated to fisheries scientists, is finally illustraded by an example associated to yield per recruit calculations, based upon JONE'S length cohort analysis.
Tipo: Text
Palavras-chave: Analyse des cohortes; Rendement par recrue; Méthode delta; Sensibilité; Length cohort analysis; Yield per recruit; Delta method; Sensitivity.
Ano: 1987
URL: https://archimer.ifremer.fr/doc/1987/rapport-1565.pdf

Simulation de la dynamique de pêcherie : modélisation, complexité et incertitude
Provedor de dados: 5
Autores: Mahevas, Stephanie.
Fisheries are defined by a set of fishermen and of marine populations impacting each other in a spatial-limited marine ecosystem. Within the over-exploitation context and according to ratified sustainable management objectives, my research has been focused on the development and a caution use of a mechanistic model describing fisheries dynamics. This model allows for integrating existing knowledge of fisheries. It aims at improving the understanding of fisheries functioning and at investigating the impact of fishing regulations on fisheries dynamics. This modelling exercise has supported many methodological developments for its parametrisation and its use in uncertainty context. Concerned with promoting a correct use of a complex model (that ambiguity link...
Tipo: Text
Palavras-chave: Statistics; Spatial; Management; Optimal complexity; Sensitivity; ISIS Fish; Statistiques; Spatial; Gestion; Complexité optimale; Sensibilité; ISIS Fish.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/2009/these-7302.pdf

Etude des interactions hôte/virus chez l’huître creuse Crassostrea gigas et son virus Ostreid herpesvirus 1
Provedor de dados: 5
Autores: Segarra, Amelie.
Ostreid herpesvirus type 1 (OsHV-1) can be considered one of the major infectious agents in Pacific oysters, Crassostrea gigas, in France and all around the world. Differences in terms of mortality among infected animals were reported suggesting a genetic basis of the susceptibility to the OsHV-1 infection. In this context, the main objective of this thesis was to understand the interactions between Pacific oysters and OsHV-1, in particular, the molecular basis of the viral cycle. Results showed that the virus is able to replicate in the host regardless of its stage of development or its susceptibility. However, multiplication kinetics is faster in the most susceptible individuals compared to less susceptible ones. After an active replication phase, it...
Tipo: Text
Palavras-chave: Bivalves; Huître creuse; Crassostrea gigas; Mortalités; OsHV-1; Gènes viruax; Interaction hôte-virus; Transcriptome; Sensibilité; PCR en temps réel; Bivalve; Pacific oyster; Crassostrea ggias; Mortality; OsHV-1; Viral gene; Interaction host-virus; Transcriptome; Susceptibility; Real-time PCR.
Ano: 2014
URL: http://archimer.ifremer.fr/doc/00252/36297/34826.pdf

Exploitation, biologie et dynamique du stock de langouste rouge de Corse, Palinurus elephas Fabricius
Provedor de dados: 5
Autores: Marin, Jean.
The European red spiny lobster (Palinurus elephas) is the main target species of the small-scale fishery in Corsica. This fishery was described, its trends from 1981 to 1964 were analysed, and the exploitation conditions of the spiny lobster stock (fishing grounds, strategy and gear ; fishing regulations) were explained. Furthermore, the fishing effort and the yields were estimated through an indirect survey, in 1983 and 1984 . The growth was studied through tagging experiments. Growth increment per moult, Von BERTALANFFY's equation parameters, and moulting frequency were estimated for both sexes. Bias risks associated to tag loss at moulting were also analysed. In addition, estimates of K and L&amp;#8734; variances were provided through "Jack-knife"...
Tipo: Text
Palavras-chave: Palinurus elephas; Fishery biology; Population dynamics; Fecundity; Recruitment; Sexual maturity; Growth; Stock assessment; Sensibilité; Fécondité par recrue; Rendement par recrue; Analyse des cohortes; Maturité sexuelle; Croissance; Pêcherie; Langouste.
Ano: 1987
URL: http://archimer.ifremer.fr/doc/1987/these-1036.pdf

La conception de structures navales en sandwich: Un probleme inverse
Provedor de dados: 5
Autores: Holm, D; Esping, B; Romell, O; Campion, F.
An integrated approach is introduced for the solution of the inverse problem: which are the lamina orientation, laminate constitution, core quality and thickness combination ensuring specified objective(s) to be reached? The optimal solution is obtained using mathematically stringent optimization methods (the Method of Moving Asymptotes, MMA) coupled with finite element analysis, interactive graphic pre- and post-processing and parametric modelling, as implemented in OASIS-ALADDIN. This approach has been applied to the optimal design of the hull structure of a Surface Effect Ship made of GRP-sandwich. The objective was to minimize the weight of the ship by determining the optimum skin and core thicknesses of structural members of the hull as well as web...
Tipo: Text
Palavras-chave: Finite element method; Glass reinforced plastics; Ship hulls; Safety devices; Ship technology; Ship design; Composite materials; Sandwich; Composite; Problème inverse; Sensibilité; Optimisation.
Ano: 1992
URL: http://archimer.ifremer.fr/doc/1992/acte-1054.pdf