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| Registros recuperados: 47 | |
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| Drouineau, Hilaire; Lobry, Jeremy; Delpech, C.; Bouchoucha, Marc; Mahevas, Stephanie; Courrat, A.; Pasquaud, S.; Lepage, M.. |
| In the context of the European Water Framework Directive (WFD), monitoring programs and related indicators have been developed to assess anthropogenic impacts on various components of aquatic ecosystems. While great precautions are usually taken when selecting and calculating relevant core metrics, little attention is generally paid to the generation of the multimetric indicator, i.e. the combination of the different core metrics. Indeed, most multimetric indicators are generated by simply averaging or summing metrics, without taking into account their sensitivity and their variability. Moreover, few indicators provide a rigorous estimate of the uncertainty of the assessments, while this estimation is essential for managers. In this context, we developed a... |
| Tipo: Text |
Palavras-chave: Multimetric fish-based indicator; Bayesian method; Pressure-impact models; Water Framework Directive; Anthropogenic pressure; Monitoring program; Transitional waters. |
| Ano: 2012 |
URL: http://archimer.ifremer.fr/doc/00049/16037/13572.pdf |
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| Vermard, Youen; Marchal, Paul; Mahevas, Stephanie; Thebaud, Olivier. |
| The scope of this paper is to describe, evaluate, and forecast fishing trip choices of the Bay of Biscay pelagic fleet using random utility modeling (RUM). First, alternative fishing trip choices of this fleet were identified using multivariate statistical methods based on species landings weighted by value and defined as distinct fishing activity or fisheries (termed metiers). A RUM was specified, which included trip components as attributes during the period 20012004 ( a lagged percentage of the value per unit of effort of the main species caught, total value per unit of effort, and inertia in terms of changes from one metier to another). For the main metiers, the proportion of correct effort allocation is 90% during the calibration period of 2001-2004.... |
| Tipo: Text |
Palavras-chave: Management; Métier; Fishing effort; Fisher's behavior; RUM. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-6096.pdf |
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| Gascuel, D.; Bez, Nicolas; Forest, Andre; Guillotreau, P.; Laloe, F.; Lobry, Jeremy; Mahevas, Stephanie; Mesnil, Benoit; Rivot, Etienne; Rochette, S.; Trenkel, Verena. |
| We, members of the Association Francaise d'Halieumetrie, share the conviction that European fisheries have a future. It is time to get off the wrong track. Radical change is required to embark on the path of sustainable development and truly implement the ecosystem approach to fisheries. Today, high fishing pressure is deployed to catch a rare resource, which in return is responsible for the rarity. We must reverse the situation: an abundant resource that affords high catches applying moderate fishing pressure. All management tools and especially all actors must be mobilized. The transition is not simple, and European solidarity must accompany the changes. It is well worth the effort. By reducing fishing pressure, it will be possible in the medium term to... |
| Tipo: Text |
Palavras-chave: Access regulation; Ecosystem approach to fisheries; European Common Fishery Policy; ITQ; MPA; MSY; Management plan; Overcapacity; Subsidies. |
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00035/14598/11947.pdf |
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| Drouineau, Hilaire; Mahevas, Stephanie; Bertignac, Michel; Duplisea, Daniel. |
| Drouineau, H., Mahevas, S., Bertignac, M., and Duplisea, D. 2010. A length-structured spatially explicit model for estimating hake growth and migration rates. - ICES Journal of Marine Science, 67: 1697-1709. |
| Tipo: Text |
Palavras-chave: Growth; Length-structured model; Merluccius merluccius; Migration; Spatial model. |
| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00016/12714/9767.pdf |
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| Kraus, Gerd; Pelletier, Dominique; Dubreuil, Julien; Moellmann, Christian; Hinrichsen, Hans-harald; Bastardie, Francois; Vermard, Youen; Mahevas, Stephanie. |
| The eastern Baltic cod stock collapsed as a consequence of climate-driven adverse hydrographic conditions and over fishing and has remained at historically low levels. Spatio-temporal fishing closures [Marine Protected Areas (MPAs)] have been implemented since 1995, to protect and restore the spawning stock. However, no signs of recovery have been observed yet, either suggesting that MPAs are an inappropriate management measure or pointing towards suboptimal closure design. We used the spatially explicit fishery simulation model ISIS-Fish to evaluate proposed and implemented fishery closures, combining an age-structured population module with a multifleet exploitation module and a management module in a single model environment. The model is parameterized... |
| Tipo: Text |
Palavras-chave: Stock recovery; Model; Marine Protected Areas; Fishery management; Baltic cod. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2009/publication-6094.pdf |
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| Vigneau, Joel; Mahevas, Stephanie. |
| Measuring fish on a market or on board a vessel is the most common action taken by biologists all around the world to gather data for stock assessment. The samples coming from this kind of survey are of vector type and are not straightforward to analyse and compare. This paper proposes a generic tool that enables to investigate in any multinomial like sampling scheme. The use of this tool will be discussed based on examples from two different sampling designs. One is a sampling of commercial market categories and the other is a métier based sampling. The research of outliers, misallocated samples or potential bias, the stratification and the analysis of within and between strata variance will be discussed with the objective of constructing the best... |
| Tipo: Text |
Palavras-chave: Stratification; Sampling design; Length structure; Market sampling. |
| Ano: 2005 |
URL: http://archimer.ifremer.fr/doc/2005/acte-2698.pdf |
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| Lehuta, Sigrid; Mahevas, Stephanie; Le Floc'H, Pascal; Petitgas, Pierre. |
| Indicators are widely promoted as means to monitor ecosystem status or to evaluate fisheries management performance. "Which indicators are most relevant as decision-support tools in fisheries management?" still remains a topical question. Indicators should be metrics related to fish populations and fleets and should be sensitive to management strategies. However, given the complexity of the processes involved, it is often difficult to unequivocally interpret variations in metrics. A simulation approach was used to study metric properties and to identify robust and relevant fishery indicators. By applying sensitivity analysis methods, simulation designs were built that cross a variety of management scenarios and uncertainty hypotheses. Bio-economic outputs... |
| Tipo: Text |
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| Ano: 2013 |
URL: https://archimer.ifremer.fr/doc/00170/28093/26627.pdf |
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| Gloaguen, Pierre; Mahevas, Stephanie; Rivot, Etienne; Woillez, Mathieu; Guitton, Jerome; Vermard, Youen; Etienne, Marie-pierre. |
| The understanding of the dynamics of fishing vessels is of great interest to characterize the spatial distribution of the fishing effort and to define sustainable fishing strategies. It is also a prerequisite for anticipating changes in fishermen's activity in reaction to management rules, economic context, or evolution of exploited resources. Analyzing the trajectories of individual vessels offers promising perspectives to describe the activity during fishing trips. A hidden Markov model with two behavioral states (steaming and fishing) is developed to infer the sequence of non-observed fishing vessel behavior along the vessel trajectory based on Global Positioning System (GPS) records. Conditionally to the behavior, vessel velocity is modeled with an... |
| Tipo: Text |
Palavras-chave: Hidden Markov model; Vessels dynamics; RECOPESCA; Autoregressive process; Baum-Welch algorithm. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00179/29049/27485.pdf |
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| Mahevas, Stephanie; Vermard, Youen; Hutton, Trevor; Iriondo, Ane; Jadaud, Angelique; Maravelias, Christos D.; Punzon, Antonio; Sacchi, Jacques; Tidd, Alex; Tsitsika, Efthymia; Marchal, Paul; Goascoz, Nicolas; Mortreux, Serge; Roos, David. |
| The impact of the fishing effort exerted by a vessel on a population depends on catchability, which depends on population accessibility and fishing power. The work investigated whether the variation in fishing power could be the result of the technical characteristics of a vessel and/or its gear or whether it is a reflection of inter-vessel differences not accounted for by the technical attributes. These inter-vessel differences could be indicative of a skipper/crew experience effect. To improve understanding of the relationships, landings per unit effort (lpue) from logbooks and technical information on vessels and gears (collected during interviews) were used to identify variables that explained variations in fishing power. The analysis was undertaken by... |
| Tipo: Text |
Palavras-chave: Catchability; Fishing power; GAM; GLM; Skipper skill; Technical characteristics. |
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00049/16043/15172.pdf |
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| Drouineau, Hilaire; Mahevas, Stephanie; Pelletier, Dominique; Beliaeff, Benoit. |
| In this paper, we present an approach to compare the impact of different management options oil the dynamics of a mixed fishery. We used ISIS-Fish, a simulation tool aimed at evaluating the impact of spatial and seasonal management measures on the dynamics of mixed fisheries. The French Nephrops norvegicus (Norway lobster) Merluccius merluccius (hake) mixed fishery of the Bay of Biscay was chosen as a Study case. First, we parameterised the Population and exploitation models. We then selected several management measures, including marine protected fishermen's reaction to each measure. Then, a sensitivity analysis (MPAs) and total allowable catches (TAC), and parameterised fish sensitivity analysis was performed according to a fractional factorial... |
| Tipo: Text |
Palavras-chave: Simulation design; Sensitivity analysis; Management measures; Spatial model; Fisheries dynamics. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-1340.pdf |
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| Drouineau, Hilaire; Mahevas, Stephanie; Bertignac, Michel; Fertin, A. |
| Most of the traditional assessment models are age-structured. However, many biological and exploitation processes are more length-dependent than age-dependent, and the required length-age conversion of available data is often not reliable. Consequently, length-structured or age-length structured models have undergone considerable development in recent years. The growth transition matrix used to model the mean growth and growth variability of the population, is of primary importance in a length-structured matrix model. Building this growth transition matrix is not trivial and it is necessary to assess the impact that various assumptions may have to identify robust model structures. In this study, we assess the effects of (1) time and length discretisation,... |
| Tipo: Text |
Palavras-chave: Sensitivity analysis; Discrete model; Growth; Length structured model. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-4301.pdf |
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| Marchal, Paul; Francis, Chris; Lallemand, Philippe; Lehuta, Sigrid; Mahevas, Stephanie; Stokes, Kevin; Vermard, Youen. |
| Managing adequately the exploitation of commercial species subject to technical interactions is a key step towards the ecosystem approach to fisheries. We evaluate here, using a bio-economic modelling approach building on the ISIS-Fish simulation platform, the relative impact of total allowable commercial catches (TACC) and of taxes applicable to over-quota landings (deemed value) on the sustainability of a selection of species exploited by the New Zealand hoki (Macruronus novaezelandiae) fishery. We investigate some aspects of the hoki mixed fisheries, consisting of four fleets and nineteen metiers, by considering the technical interactions between hoki and Southern hake (Merluccius australis). The dynamics of effort allocation were modelled using gravity... |
| Tipo: Text |
Palavras-chave: Fleet dynamics; New Zealand hoki fishery; Deemed value; Fisheries management. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/00000/11168/7521.pdf |
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| Vermard, Youen; Lehuta, Sigrid; Mahevas, Stephanie; Thebaud, Olivier; Marchal, Paul; Gascuel, Didier. |
| It is increasingly recognized that fisher‟s behavior should be taken into account to understand and predict fishery dynamics, in particular in response to management. ISIS-Fish is a spatially and seasonally explicit modeling framework especially designed to couple populations and fleets dynamics and explore the impact of various management measures on mixed fisheries. It has already been set up using a static fishing effort allocation (corresponding to an average historical pattern) between the various métiers to simulate the pelagic fishery in the Bay of Biscay. We present here the integration of a fleet dynamics model. This model is derived from a Random Utility Model simulating métiers choice using as explanatory variables the past value per unit... |
| Tipo: Text |
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| Ano: 2012 |
URL: http://archimer.ifremer.fr/doc/00107/21858/19449.pdf |
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| Pardo, Sophie; Hess, Philipp; Simon, Elodie; Barille, Laurent; Geslin, Emmanuelle; Cognie, Bruno; Martin-jezequel, Véronique; Sechet, Véronique; Herrenknecht, Christine; Baron, Regis; Bourseau, Patrick; Amzil, Zouher; Masse, Anthony; Vandanjon, Laurent; Dumay, Justine; Lebeau, Thierry; Turpin, Vincent; Mondeguer, Florence; Petitgas, Pierre; Trouillet, Brice; Mercier, Denis; Guillotreau, Patrice; Guineberteau, Thierry; Mahevas, Stephanie; Schoefs, Franck; Sophie Pardo; Philipp Hess; Pauline Borgniet; Laurent Barillé; Emmanuelle Geslin; Bruno Cognie; Véronique Martin-Jezequel; Véronique Sechet; Christine Herrenknecht; Régis Baron; Patrick Bourseau; Zouher Amzil; Anthony Massé; Laurent Vandanjon; Justine Dumay; Thierry Lebeau; Vincent Turpin; Florence Mondeguer; Pierre Petitgas; Brice Trouillet. |
| COSELMAR, a 4-year project financed by the Région des Pays de la Loire at 2.1 M€, officially started on the 7th January 2013. The project is coordinated by Philipp Hess (IFREMER) and Sophie Pardo (Université de Nantes-LEMNA) and falls under the Federation for Research Institut Universitaire Mer et Littoral (IUML, FR CNRS 3473)*. COSELMAR has also been approved by the Scientific Council of the MSH Ange Guépin. COSELMAR is a research project uniting 5 research units of IFREMER and 11 laboratories of the Université de Nantes, along with academic partners, and national and international industries. The aim is to achieve a better understanding of the marine and coastal ecosystems and the associated resources. The project will also provide insights into risk... |
| Tipo: Text |
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| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00406/51793/52550.pdf |
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| Vigneau, Joel; Mahevas, Stephanie. |
| Measuring fish on board fishing vessels or at fish markets to collect data for stock assessment purposes is one of the most straightforward actions carried out by fisheries scientists worldwide. However, such samples are not straightforward to handle and analyse because of their vector-type structure. A generic tool that allows investigation in any multinomial-like sampling scheme is provided, as long as the scheme is built on a ratio estimator, which is the case for most length sampling in the fisheries sector. The use of this tool is discussed using data obtained from two different sampling designs, one consisting of commercial market samples by category and the other on fishing activity or metier. The identification of outliers, misallocated samples, or... |
| Tipo: Text |
Palavras-chave: Stratification; Sampling design; Market sampling; Length structure. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2731.pdf |
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| Doray, Mathieu; Mahevas, Stephanie; Trenkel, Verena. |
| Few analyses have been performed to estimate the efficiency of trawls targeting demersal fish using the ratio of catches and acoustic densities. In summer 2006, acoustic and fishing data were collected simultaneously over 3 d by three fishing vessels equipped with identical pelagic trawls in the Bay of Biscay. Variography identified moderate spatial autocorrelation in the acoustic backscatter at a mean scale of 3 km, a scale slightly smaller than the mean haul length (3.5 km), indicating that fish horizontal availability did not influence trawl efficiency. Acoustic backscattering densities expressed as nautical area scattering coefficients (NASCs) recorded in the trawled layer were compared with equivalent NASC (ENASC) values calculated from the species... |
| Tipo: Text |
Palavras-chave: Availability; Bay of Biscay; Catchability; Generalized linear model; Geostatistics; Hake; Vulnerability. |
| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00002/11372/7980.pdf |
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| Pelletier, Dominique; Mahevas, Stephanie; Drouineau, Hilaire; Vermard, Youen; Thebaud, Olivier; Guyader, Olivier; Poussind, Benjamin. |
| In order to provide reliable scientific advice and support for fisheries management, it is necessary to evaluate the biological and economic sustainability of complex fisheries, such as multi-species multi-fleet fisheries. Existing policy-screening modelling tools are not fully suitable in this purpose due to either an over-simplified description of population dynamics, or due to the lack of consideration of economic aspects. In this paper, we present a package that enables quantitative bioeconomic assessment of management scenarios. Population dynamics is described through spatially- and seasonally-explicit models. Exploitation dynamics is characterized by several fishing activities with specific spatial and seasonal features, and practiced by several... |
| Tipo: Text |
Palavras-chave: Policy screening; Natural resource management; Fisheries dynamics; Bioeconomic model; Population dynamics; Complex systems; Simulation tool. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2009/publication-6782.pdf |
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| Registros recuperados: 47 | |
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