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| Registros recuperados: 47 | |
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| Reecht, Yves; Gasche, Loïc; Lehuta, Sigrid; Vaz, Sandrine; Smith, Robert J; Mahevas, Stephanie; Marchal, Paul. |
| In the past decade, systematic conservation planning tools have been increasingly and successfully used to set spatial conservation plans that meet quantitative protection targets while minimizing enforcement and socioeconomic costs. However, when applied to fisheries, systematic conservation planning fails to account for (1) changes in fleet dynamics induced by new conservation constraints and their associated feedbacks on conservation costs or (2) their influence on fish population dynamics and distributions, which may in turn alter the achievement of conservation targets. Such a static approach may therefore lead to short- or medium-term misestimates in forecasted costs and target achievements. In order to circumvent such limitations of systematic... |
| Tipo: Text |
Palavras-chave: MPAs; Systematic conservation planning; Mixed fisheries dynamics; Model coupling; Eastern English Channel; Marxan with Zones; ISIS-Fish. |
| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00293/40421/39077.pdf |
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| Marchal, Paul; Bartelings, Heleen; Bastardie, François; Batsleer, Jurgen; Delaney, Alyne; Girardin, Raphael; Gloaguen, Pierre; Hamon, Katell; Hoefnagel, Ellen; Jouanneau, Charlène; Mahevas, Stephanie; Nielsen, Rasmus; Piwowarczyk, Joanna; Poos, Jan-jaap; Schulze, Torsten; Rivot, Etienne; Simons, Sarah; Tidd, Alex; Vermard, Youen; Woillez, Mathieu. |
| The scope of this report is to present the science developed within the VECTORS project to improve the understanding of the key processes driving the behaviour of human agents utilising a variety of EU maritime domains. While particular attention has been paid to the spatial interactions between fishing activities and other human uses (e.g., maritime traffic, offshore wind parks, aggregate extractions), the behaviour of non-fishing sectors of activity has also been considered. Various quantitative and semi-qualitative approaches have been pursued to gain better insight into behavioural drivers based on past data, and also forecast how human agents would react if access was constrained by either management (e.g. Marine Protected Areas – MPA), or the... |
| Tipo: Text |
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| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00223/33377/31802.pdf |
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| Lehuta, Sigrid; Petitgas, Pierre; Mahevas, Stephanie; Huret, Martin; Vermard, Youen; Uriarte, Andres; Record, Nicholas R.. |
| Assessing the validity of a model is essential for its credibility especially when the model is used as decision making tool. Complex dynamic fishery models are recommended to investigate the functioning of fisheries and to assess the impact of management strategies, particularly spatial fishing regulations. However, their use is limited due to the difficulty and computational cost of parameterizing and gaining confidence, particularly for parameter rich models. These difficulties are compounded by uncertainty regarding parameter values, many of which are often taken from literature or estimated indirectly. Here we propose a methodology to improve confidence and understanding in the model, easily transferable to any complex model. The approach combines... |
| Tipo: Text |
Palavras-chave: Bay of Biscay anchovy; Dynamic fishery model; Model selection; Uncertainty; Validation. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00148/25965/24150.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; 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; Rivot, Etienne; Mahevas, Stephanie; Marchal, Paul; Gascuel, Didier. |
| Recent advances in technologies have lead to a vast influx of data on movements, based on discrete recorded position of animals or fishing boats, opening new horizons for future analyses. However, most of the potential interest of tracking data depends on the ability to develop suitable modelling strategies to analyze trajectories from discrete recorded positions. A serious modelling challenge is to infer the evolution of the true position and the associated spatio-temporal distribution of behavioural states using discrete, error-prone and incomplete observations. In this paper, a Bayesian Hierarchical Model (HBM) using Hidden Markov Process (HMP) is proposed as a template for analyzing fishing boats trajectories based on data available from... |
| Tipo: Text |
Palavras-chave: Bayesian Hierarchical Models; Hidden Markov Model; State-space model; VMS; Fleet behaviour; Fishing effort. |
| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00009/11993/9342.pdf |
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| Trenkel, Verena; Rochet, Marie-joelle; Mahevas, Stephanie. |
| Norway lobster, Nephrops norvegicus (L.) was found to show diel activity patterns with more individuals outside their burrows at dawn and dusk in the Bay of Biscay in August 2004 and catchabilities were higher at these times. Using data from an onboard observer programme of Nephrops trawlers in 2002-2005, we investigated whether the expected variability in catchability was visible in commercial catches. Catch numbers per haul varied spatially and between months but no signal for diel variations was found. Fishing strategies developed by the Nephrops trawlers had several components. On a seasonal level they started around sunrise. On a haul level, haul duration decreased from haul to haul, with the longest hauls taking place at the time of highest... |
| Tipo: Text |
Palavras-chave: Time of day; Fishing strategy; Diel activity patterns; Catchability. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2618.pdf |
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| Biseau, Alain; Mahevas, Stephanie; Perodou, Jean-bernard; Berthou, Patrick. |
| Three fleets of the French fishery are investigated : the dredge fleet of the Western part of the Channel, the bottom-trawl fishery of South-Britanny harbours, and the Mediterranean trawl fishery. Landing and effort data by species, vessel and trip lead to yields (catch per unit of effort) which are analysed by a multicplicative model with two or three factors. Individual fishing powers are then quantified for some given years, together with variation in relative abundance of the stock within area and/or period strata. Attempts to explain these fishing powers by vessels characteristics are made. After the study of the Mediterranean trawl-fleet, which takes Year into account in the model, two multi-annual series are analysed, and some conclusions on fishing... |
| Tipo: Text |
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| Ano: 1999 |
URL: http://archimer.ifremer.fr/doc/00327/43785/43343.pdf |
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| Marchal, Paul; Gasche, Loic; Girardin, Raphael; Le Pape, Olivier; Huret, Martin; Mahevas, Stephanie; Travers-trolet, Morgane; Vaz, Sandrine. |
| Considerable research has been conducted in the past 15 years around the Eastern English Channel ecosystem. Data collected since the 1970s on the biotic and abiotic compartments have been collated and mapped out in the mid-2000. This spatially explicit information formed a sound basis to improve knowledge on, and model, the functioning and dynamics of key ecosystem compartments, with a focus on flatfish species and fisheries and their interactions with other sectors of activity (aggregate extractions, maritime traffic). The more recent ongoing works are dedicated to the integration of those processes into several complementary end-to-end ecosystem models. |
| Tipo: Text |
Palavras-chave: Eastern English Channel; Flatfish; Spatial analyses; Ecosystem modelling. |
| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00293/40420/38946.pdf |
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| Marchal, Paul; Andersen, B; Bromley, D; Iriondo, A; Mahevas, Stephanie; Quirijns, F; Rackham, B; Santurtun, M; Tien, N; Ulrich, Clara. |
| The scope of this paper is to quantify, for a wide selection of European fisheries, fishing tactics and strategies and to evaluate the benefits of adjusting the definition of. fishing effort using these elements. Fishing tactics and strategies were identified by metiers choices and a series of indices. These indices have been derived to reflect shifts in tactics (within a fishing trip) and in strategies (within a year). The Shannon-Wiener spatial diversity indices of fishing tactics (FT_SW) and strategies (YE_SW) had the greatest impact on catch rates. In particular, FT_SW was always negatively correlated to catch rates. One may anticipate that during a fishing trip, vessels with high FT_SW have been searching fish aggregations for a long time, while... |
| Tipo: Text |
Palavras-chave: Fishing effort; Fishing mortality; Catch rates; GLM modeling; Skipper effect. |
| Ano: 2006 |
URL: https://archimer.ifremer.fr/doc/2006/publication-1339.pdf |
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| 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 |
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| Deporte, Nicolas; Ulrich, Clara; Mahevas, Stephanie; Demaneche, Sebastien; Bastardie, Francois. |
| The European Common Fisheries Policy recognizes the importance of accounting for heterogeneity in fishing practices, and metier-based sampling is now at the core of the EU Data Collection Framework. The implementation of such an approach would require Member States to agree on the standard regional metier definitions and on practical rules to categorize logbook records into metiers. Several alternative approaches have been used in the past to categorize landings profiles, but no consensus has yet emerged. A generic open-source workflow is developed to test and compare a selection of methods, including principal components analysis (PCA), hierarchical agglomerative clustering (HAC), K-means, and Clustering LARge Applications (CLARA), and to provide simple... |
| Tipo: Text |
Palavras-chave: Cluster; Data Collection Framework (DCF); Logbooks; Mtier; Mixed fisheries; Multivariate analysis; North Sea. |
| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00071/18225/15841.pdf |
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| Tissiere, Laurie; Michel, Charlotte; Mahevas, Stephanie; Trouillet, Brice. |
| Prospective studies considered that the future is not determined. Time is then a lever to enhance debates. More recently, << geoprospective >> has integrated space in discussions about possible futures. That questions directly the functions of the spatial and the temporal dimensions, especially the capacity of space and time to play as intermediaries for participation. We applied this question on the case of a fishery in the Bay of Biscay. On the one hand, we demonstrated that the participative method, combining qualitative and quantitative approaches, as well as simple and complex tools, allowed to describe the stakes of the case study and to imagine spatially-explicit possible changes. On the other hand, we also pointed that space and time... |
| Tipo: Text |
Palavras-chave: Géoprospective; Participations; Méthodes spatio-temporelles; Représentations; Pêches maritimes; Geoprospective; Participations; Spatial and temporal methods; Representations; Fisheries. |
| Ano: 2018 |
URL: http://archimer.ifremer.fr/doc/00449/56039/57557.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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| Doray, Mathieu; Petitgas, Pierre; Nelson, Laetitia; Mahevas, Stephanie; Josse, E; Reynal, Lionel. |
| Fish-aggregating devices (FADs) are increasingly used worldwide to enhance tuna catches. Meanwhile, ecosystem-based management of this fishery is constrained by a paucity of information regarding the interaction of FAD-associated tuna aggregations with their local environment. This paper reports the results of a nine-month study around a FAD moored near Martinique Island, aimed at assessing the effects of the local environment on the variability of monthly estimates of proximate tuna biomass. Dual-frequency, active acoustics provided highresolution quantitative data on the pelagic community around the FAD, from fish to micronekton forage. Geostatistics were used to compute biomass estimates of the tuna aggregation comprising most of the FADassociated fish... |
| Tipo: Text |
Palavras-chave: Lesser Antilles; Tuna; Environment; Geostatistics; Biomass estimation; Fish aggregating device. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2008/publication-6162.pdf |
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| Registros recuperados: 47 | |
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