Consulta: creatorFacets:"Mahevas, Stephanie"
Registros recuperados: 47
Data/hora: 05/06/2024 09:16:50

The influence of the environment on the variability of monthly tuna biomass around a moored, fish-aggregating device
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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

Integrated ecological-economic fisheries models-Evaluation, review and challenges for implementation
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Nielsen, J. Rasmus; Thunberg, Eric; Holland, Daniel S.; Schmidt, Jorn O.; Fulton, Elizabeth A.; Bastardie, Francois; Punt, Andre E.; Allen, Icarus; Bartelings, Heleen; Bertignac, Michel; Bethke, Eckhard; Bossier, Sieme; Buckworth, Rik; Carpenter, Griffin; Christensen, Asbjorn; Christensen, Villy; Da-rocha, Jose M.; Deng, Roy; Dichmont, Catherine; Doering, Ralf; Esteban, Aniol; Fernandes, Jose A.; Frost, Hans; Garcia, Dorleta; Gasche, Loic; Gascuel, Didier; Gourguet, Sophie; Groeneveld, Rolf A.; Guillen, Jordi; Guyader, Olivier; Hamon, Katell; Hoff, Ayoe; Horbowy, Jan; Hutton, Trevor; Lehuta, Sigrid; Little, L. Richard; Lleonart, Jordi; Macher, Claire; Mackinson, Steven; Mahevas, Stephanie; Marchal, Paul; Mato-amboage, Rosa; Mapstone, Bruce; Maynou, Francesc; Merzereaud, Mathieu; Palacz, Artur; Pascoe, Sean; Paulrud, Anton; Plaganyi, Eva; Prellezo, Raul; Van Putten, Elizabeth I.; Quaas, Martin; Ravn-jonsen, Lars; Sanchez, Sonia; Simons, Sarah; Thebaud, Olivier; Tomczak, Maciej T.; Ulrich, Clara; Van Dijk, Diana; Vermard, Youen; Voss, Rudi; Waldo, Staffan.
Marine ecosystems evolve under many interconnected and area-specific pressures. To fulfil society's intensifying and diversifying needs while ensuring ecologically sustainable development, more effective marine spatial planning and broader-scope management of marine resources is necessary. Integrated ecological–economic fisheries models (IEEFMs) of marine systems are needed to evaluate impacts and sustainability of potential management actions and understand, and anticipate ecological, economic and social dynamics at a range of scales from local to national and regional. To make these models most effective, it is important to determine how model characteristics and methods of communicating results influence the model implementation, the nature of the...
Tipo: Text
Palavras-chave: Bio-economic models; Comparative model evaluation; Fisheries management advice; Integrated ecological-economic fisheries models; Marine spatial planning and cross-sector management; Performance criteria and scales and risks; Use and acceptance and implementation and communication and flexibility and complexity.
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00391/50269/50898.pdf

Regional metier definition: a comparative investigation of statistical methods using a workflow applied to international otter trawl fisheries in the North Sea
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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

Puissances de pêche et relations avec les caractéristiques techniques des navires. Exemple de flottilles pratiquant les arts traînants en Manche Ouest, Atlantique et Méditerranée.
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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
Ano: 1999
URL: http://archimer.ifremer.fr/doc/00327/43785/43343.pdf

Improving the definition of fishing effort for important European fleets by accounting for the skipper effect
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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

Metrics for describing dyadic movement: a review
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Joo, Rocio; Etienne, Marie-pierre; Bez, Nicolas; Mahevas, Stephanie.
In movement ecology, the few works that have taken collective behaviour into account are data-driven and rely on simplistic theoretical assumptions, relying in metrics that may or may not be measuring what is intended. In the present paper, we focus on pairwise joint-movement behaviour, where individuals move together during at least a segment of their path. We investigate the adequacy of twelve metrics introduced in previous works for assessing joint movement by analysing their theoretical properties and confronting them with contrasting case scenarios. Two criteria are taken into account for review of those metrics: 1) practical use, and 2) dependence on parameters and underlying assumptions. When analysing the similarities between the metrics as...
Tipo: Text
Palavras-chave: Collective behaviour; Dyadic movement; Indices; Movement ecology; Spatio-temporal dynamics; Trajectories.
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00475/58657/61156.pdf

Evaluation of the bioeconomic sustainability of multi-species multi-fleet fisheries under a wide range of policy options using ISIS-Fish
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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

Assessing the impact of different management options using ISIS-Fish*: the French Merluccius merluccius Nephrops norvegicus mixed fishery of the Bay of Biscay
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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

Projecting changes in the distribution and productivity of living marine resources: A critical review of the suite of modeling approaches used in the large European project VECTORS
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Peck, Myron A.; Arvanitidis, Christos; Butenschon, Momme; Canu, Donata Melaku; Chatzinikolaou, Eva; Cucco, Andrea; Domenici, Paolo; Fernandes, Jose A.; Gasche, Loic; Huebert, Klaus B.; Hufnagl, Marc; Jones, Miranda C.; Kempf, Alexander; Keyl, Friedemann; Maar, Marie; Mahevas, Stephanie; Marchal, Paul; Nicolas, Delphine; Pinnegar, John K.; Rivot, Etienne; Rochette, Sebastien; Sell, Anne F.; Sinerchia, Matteo; Solidoro, Cosimo; Somerfield, Paul J.; Teal, Lorna R.; Travers-trolet, Morgane; Van De Wolfshaar, Karen E.
We review and compare four broad categories of spatially-explicit modelling approaches currently used to understand and project changes in the distribution and productivity of living marine resources including: 1) statistical species distribution models, 2) physiology-based, biophysical models of single life stages or the whole life cycle of species, 3) food web models, and 4) end-to-end models. Single pressures are rare and, in the future, models must be able to examine multiple factors affecting living marine resources such as interactions between: i) climate-driven changes in temperature regimes and acidification, ii) reductions in water quality due to eutrophication, iii) the introduction of alien invasive species, and/or iv) (over-)exploitation by...
Tipo: Text
Palavras-chave: Distribution; Modelling; Habitat; Resources; Man-induced effects.
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00337/44845/44436.pdf

What can exploratory modelling tell us about the ecobiology of European sea bass (     Dicentrarchus labrax     ): a comprehensive overview
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Lopez, Romain; De Pontual, Helene; Bertignac, Michel; Mahevas, Stephanie.
European sea bass, Dicentrarchus labrax, is a highly valuable species in Europe, both for aquaculture in the Mediterranean Sea and for commercial and recreational fisheries in the North East Atlantic Ocean. Subjected to increasing fishing pressure, the wild population has recently experienced significant recruitment fluctuation as well as a northward extension of its distribution area in the North Sea. While the nature of the ecological and/or physiological processes involved remains unresolved, ontogenetic habitat shifts and adult site fidelity could increase the species’ vulnerability to climate change and overfishing. As managers look for expert information to propose management scenarios leading to sustainable exploitation, exploratory modelling...
Tipo: Text
Palavras-chave: Population dynamics; Essential habitats; Connectivity; Bioenergetic modeling; Phenotypic plasticity; Life cycle adaptation.
Ano: 2015
URL: http://archimer.ifremer.fr/doc/00341/45258/44699.pdf

A length-structured spatially explicit model for estimating hake growth and migration rates
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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

Is speed through water a better proxy for fishing activities than speed over ground?
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Gloaguen, Pierre; Woillez, Mathieu; Mahevas, Stephanie; Vermard, Youen; Rivot, Etienne.
Understanding fishing vessel dynamics at a fine spatial scale is of great interest for defining appropriate spatial management plans. Different models have been developed to detect fishing activity from Vessel Monitoring System (VMS) data. While mathematical and statistical methods differ, all rely on the idea that vessel speed over ground provides information on fishing vessel activity. However, trawling with constant speed relative to the water mass may as well prove a winning strategy for both technical (to ensure sufficient trawl opening) and biological (to limit escapement of fish) reasons. Therefore, considering speed through water instead of speed over ground might provide insights into fishing activities. We developed a method combining surface...
Tipo: Text
Palavras-chave: Vessel monitoring system surface currents hidden Markov models; MARS 3D; Obsmer.
Ano: 2016
URL: http://archimer.ifremer.fr/doc/00359/47030/46948.pdf

An autoregressive model to describe fishing vessel movement and activity
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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

Raconter l’espace en jouant avec le temps. Exemple d’un exercice participatif de géoprospective des pêches maritimes
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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, &lt;&lt; geoprospective &gt;&gt; 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

Supporting Fisheries Management by Means of Complex Models: Can We Point out Isles of Robustness in a Sea of Uncertainty?
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Gasche, Loic; Mahevas, Stephanie; Marchal, Paul.
Ecosystems are usually complex, nonlinear and strongly influenced by poorly known environmental variables. Among these systems, marine ecosystems have high uncertainties: marine populations in general are known to exhibit large levels of natural variability and the intensity of fishing efforts can change rapidly. These uncertainties are a source of risks that threaten the sustainability of both fish populations and fishing fleets targeting them. Appropriate management measures have to be found in order to reduce these risks and decrease sensitivity to uncertainties. Methods have been developed within decision theory that aim at allowing decision making under severe uncertainty. One of these methods is the information-gap decision theory. The info-gap...
Tipo: Text
Ano: 2013
URL: http://archimer.ifremer.fr/doc/00166/27746/25947.pdf

Cluster analysis of linear model coefficients under contiguity constraints for identifying spatial and temporal fishing effort patterns
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Mahevas, Stephanie; Bellanger, Lise; Trenkel, Verena.
For fisheries management purposes, it is essential to take into account spatial and seasonal characteristics of fishing activities to allow a reliable assessment of fishing impact on resource. This paper presents a novel technique for describing spatial and temporal patterns in fishing effort. The spatial and seasonal fishing activity patterns of the French trawler fleet in the Celtic Sea during the period 1991–1998 were analysed by modelling fishing effort (fishing time) with generalised linear models. The linear model for fishing effort included fixed effects for both spatial (statistical rectangles) and temporal units (months). In addition, spatial correlations in any given month were modelled by an exponentially decreasing function. Temporal...
Tipo: Text
Palavras-chave: Fleet dynamics; Allocation of Fishing effort; Spatial and seasonal pattern; Statistics for spatial data; Cluster analysis under contiguity constraints; Generalised linear model.
Ano: 2008
URL: http://archimer.ifremer.fr/doc/2008/publication-4302.pdf

Rapport du projet PECHALO (Pêche Chalutière Occitanie) : Etude de l’impact de l’adaptation des stratégies de pêche et des navires de la flottille chalutière occitane pour améliorer leur viabilité et la durabilité de l’activité
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Leforestier, Sophie; Lehuta, Sigrid; Mahevas, Stephanie; Jadaud, Angelique; Vaz, Sandrine.
Dans le Golfe du Lion, le mauvais état des stocks de petits pélagiques a entrainé à partir de 2009 un report de l’activité chalutière pélagique vers les pêcheries démersales. Cette augmentation de la pression de pêche sur les espèces démersales ne facilite pas l’amélioration de l’état de la population de merlu dont le niveau d'exploitation est actuellement 12 fois supérieur au niveau estimé comme durable. En 2018, de nouvelles mesures complémentaires ont été proposées (réduction de l’effort de pêche, fermeture de zones) afin d’assurer un retour au Rendement Maximum Durable du merlu d’ici 2020. Cependant à ce jour les conséquences de ces mesures de gestion sur la pêcherie sont difficilement prévisibles. Une approche basée sur un simulateur de dynamique de...
Tipo: Text
Palavras-chave: Pêcherie chalutière; Occitanie; Gestion durable; Viabilité; Merlu; ISISFISH.
Ano: 2020
URL: https://archimer.ifremer.fr/doc/00622/73377/72577.pdf

Estimating gear efficiency in a combined acoustic and trawl survey, with reference to the spatial distribution of demersal fish
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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

A dynamic model of the Bay of Biscay pelagic fleet simulating fishing trip choice: the response to the closure of the European anchovy (Engraulis encrasicolus) fishery in 2005
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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

A Bayesian framework to objectively combine metrics when developing stressor specific multimetric indicator
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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

Toward a Dynamical Approach for Systematic Conservation Planning of Eastern English Channel Fisheries
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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

Towards a spatial integrated stock assessment model for European hake northern stock
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Vigier, Audric; Mahevas, Stephanie; Bertignac, Michel.
European hake (Merluccius merluccius) is a key species in the management of several mixed fisheries in the north-east Atlantic where regional spatial management plans are being set up. The wide spatial distribution of hake and the lack of knowledge of some processes involved in its spatial dynamics could hamper the assessment and management of hake. To help understand the processes, we implemented a spatial version of the Stock Synthesis stock assessment model for northern hake, including available data on this stock and the associated fisheries. For the 1978–2012 time series, the model distinguished the Bay of Biscay, the Celtic Sea and a northern area aggregating the West of Scotland and the North Sea. The model considered an age-structured population...
Tipo: Text
Palavras-chave: Stock Synthesis; Integrated analysis; Spatially explicit model; European northern hake; Merluccius merluccius.
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00417/52869/53871.pdf

ISIS-Fish, a generic and spatially explicit simulation tool for evaluating the impact of management measures on fisheries dynamics
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Mahevas, Stephanie; Pelletier, Dominique.
Assessing the impact of management scenarii on multi-species multi-fleet fisheries requires spatially and seasonally explicit simulation tools. No such tools are currently available in fisheries science. This paper presents a software that evaluates the impact of management measures on the dynamics of a complex fishery. The simulation model is generic in order to be used for different types of fisheries. Existing knowledge about each fishery is stored in a database included in the software, and may be easily modified. This includes the parameters describing each population and each fishing activity. Furthermore, the software allows for flexibility in several model assumptions. Both management measures and behaviour of fishermen in reaction to these...
Tipo: Text
Palavras-chave: Management measures; Fisheries dynamics; Complex systems; Spatial; Integration of knowledge; Simulation tool.
Ano: 2004
URL: http://archimer.ifremer.fr/doc/2004/publication-1133.pdf

Detecting sampling outliers and sampling heterogeneity when catch-at-length is estimated using the ratio estimator
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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

Application of Moran Eigenvector Maps (MEM) to irregular sampling designs
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Brind'Amour, Anik; Mahevas, Stephanie; Legendre, Pierre; Bellanger, Lise.
Moran’s eigenvectors maps (MEM) are attractive mathematical objects as they are fairly simple to calculate and can be used in most studies of spatially-explicit data. There is, however, an aspect of MEM analysis that still requires some investigation: the effect of irregular sampling on their modeling performance. This study investigates empirically the behavior of MEMs under different irregularity schemes. It is focusing on simulated scenarios representing sampling designs frequently encountered in ecology. We advocate that MEMs can be computed and correctly used with data coming from irregularly designed sampling surveys, given some precautions. We suggest that when the sampling sites are equally spaced but do not cover the entire study area, the MEMs...
Tipo: Text
Palavras-chave: Autocorrelation; Irregular sampling; Sampling schemes; Spatial analyses; Statistical methods.
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00444/55594/57224.pdf

Selection and validation of a complex fishery model using an uncertainty hierarchy
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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

A new statistic for sampling design investigation : an application to length-structured landings sampling
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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

From Data to End-to-End Models: 15 Years of Research to Describe the Dynamics of Exploited Marine Ecosystems in the Eastern Channel
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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

Identifying fishing trip behaviour and estimating fishing effort from VMS data using Bayesian Hidden Markov Models
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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

A simulation-based approach to assess sensitivity and robustness of fisheries management indicators for the pelagic fishery in the Bay of Biscay
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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
Ano: 2013
URL: https://archimer.ifremer.fr/doc/00170/28093/26627.pdf

Reconciling complex system models and fisheries advice: Practical examples and leads
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Lehuta, Sigrid; Girardin, Raphael; Mahevas, Stephanie; Travers-trolet, Morgane; Vermard, Youen.
The move toward an ecosystem-based fisheries management (EBFM) requires new operational tools in order to support management decisions. Among them, ecosystem- and fisheries-based models are critical to quantitatively predict the consequences of future scenarios by integrating available knowledge about the ecosystem across different scales. Despite increasing development of these complex system models in the last decades, their operational use is still currently limited in Europe. Many guidelines are already available to help the development of complex system models for advice yet they are often ignored. We identified three main impediments to the use of complex system models for decision support: (1) their very complexity which is a source of uncertainty;...
Tipo: Text
Palavras-chave: Ecosystem-based fisheries management; Complex models; Decision support; Methodological solutions; Participatory modeling; Model sensitivity analysis; Examples.
Ano: 2016
URL: http://archimer.ifremer.fr/doc/00358/46945/46851.pdf

Catch-quota balancing in mixed-fisheries: a bio-economic modelling approach applied to the New Zealand hoki (Macruronus novaezelandiae) fishery
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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

Model of the leaky bucket ATM generic flow control mechanism: a case study on solving large cyclic models
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Carrasco, Ja; Sune, V; Mahevas, Stephanie; Rubino, G.
The authors describe and solve a Markov model of the leaky bucket ATM generic now control mechanism. The model has a space cardinality which grows quickly with its parameters and is challenging to solve. Exploiting the cyclic nature of the model, the authors develop a methodology which allows them to efficiently solve instances of the model with 3 905 134 states and 53 869 532 transitions using 29.8Mbyte of memory and 222Mbyte of disc storage. The CPU utilisation is high (between 70% and 90%). The methodology is new and can be easily extended to any kind of finite cyclic Markov models.
Tipo: Text
Ano: 2001
URL: http://archimer.ifremer.fr/doc/00000/10303/9659.pdf

Spatially explicit fisheries simulation models for policy evaluation
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Pelletier, Dominique; Mahevas, Stephanie.
This paper deals with the design of modelling tools suitable for investigating the consequences of alternative policies on the dynamics of resources and fisheries, such as the evaluation of marine protected areas (MPA). We first review the numerous models that have been developed for this purpose, and compare them from several standpoints: population modelling, exploitation modelling and management measure modelling. We then present a generic fisheries simulation model, Integration of Spatial Information for FISHeries simulation (ISIS-Fish). This spatially explicit model allows quantitative policy screening for fisheries with mixed-species harvests. It may be used to investigate the effects of combined management scenarios including a variety of policies:...
Tipo: Text
Palavras-chave: Spatially and seasonally explicit model; Simulation tool; Mixed fishery; Marine protected areas; Management measures; Fisheries dynamics; Fisher' s behaviour.
Ano: 2005
URL: http://archimer.ifremer.fr/doc/2005/publication-1031.pdf

An investigation of human vs. technology-induced variation in catchability for a selection of European fishing fleets
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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

Mechanisms of change in human behaviour
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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
Ano: 2014
URL: http://archimer.ifremer.fr/doc/00223/33377/31802.pdf

A model-based evaluation of Marine Protected Areas: the example of eastern Baltic cod (Gadus morhua callarias L.)
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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

COSELMAR. Compréhension des socio-écosystèmes littoraux et marins pour la prévention et la gestion des risques. Bilan scientifique 2013-2017
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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
Ano: 2017
URL: https://archimer.ifremer.fr/doc/00406/51793/52550.pdf

Simulation de la dynamique de pêcherie : modélisation, complexité et incertitude
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
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

Assessing the impact of discretisation assumptions in a length-structured population growth model
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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

Interactions between fishing strategies of nephrops trawlers in the Bay of Biscay and Norway lobster diel activity patterns
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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

Modelling Fishing Vessels Movement and Activity
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Gloaguen, Pierre; Mahevas, Stephanie; Rivot, Etienne; Woillez, Mathieu; Guitton, Jérome; Vermard, Youen; Etienne, Marie-pierre.
Tipo: Text
Ano: 2013
URL: http://archimer.ifremer.fr/doc/00371/48181/48296.pdf

Projet Bargip. Action Données professionnelles. Rapport final
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Drogou, Mickael; Laurec, Alain; Bissery, Claire; Mahevas, Stephanie; Demaneche, Sebastien; Begot, Eric; Weiss, Jerome; De Pontual, Helene; Le Goff, Ronan.
La décroissance des rendements de capture professionnelle de bar européen Dicentrarchus labrax à partir des années 2010-2011 a amené la DPMA à demander à l’Ifremer de proposer un programme de recherche visant à mieux connaitre la biologie de l’espèce et à acquérir des données et connaissances permettant d’envisager sa gestion. Parmi les actions de recherche identifiées comme prioritaires, l’action « Données professionnelles » a compris deux grands volets :  - utilisation des données de captures professionnelles françaises afin de produire des indices annuels d’abondance en bars adultes,  - acquisition de données biologiques (maturité sexuelle principalement et courbe de croissance) sur le bar dans le golfe de Gascogne
Tipo: Text
Ano: 2018
URL: http://archimer.ifremer.fr/doc/00429/54044/55428.pdf

Combining sensitivity and uncertainty analysis to evaluate the impact of management measures with ISIS-Fish: marine protected areas for the Bay of Biscay anchovy (Engraulis encrasicolus) fishery
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Lehuta, Sigrid; Mahevas, Stephanie; Petitgas, Pierre; Pelletier, Dominique.
Spatio-seasonal explicit simulation models can predict the impact of spatial management measures on marine fish populations and fishing activities. As fisheries are complex systems, fisheries simulation models are often complex, with many uncertain parameters. Here, the methodology is provided to deliver fishery diagnostics within an uncertainty context using a complex simulation tool. A sensitivity analysis of the model is performed on model outputs using partial least-squares to identify the most sensitive parameters. The impact of several management measures is then simulated using a statistical simulation design taking into account the uncertainty of the selected sensitive parameters. This approach was applied to the Bay of Biscay anchovy stock using...
Tipo: Text
Palavras-chave: Bay of Biscay anchovy; Marine protected area; Sensitivity analysis; Simulation; Uncertainty analysis.
Ano: 2010
URL: http://archimer.ifremer.fr/doc/00011/12234/9281.pdf

Hake catchability by the French trawler fleet in the Bay of Biscay: estimating technical and biological components
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Mahevas, Stephanie; Trenkel, Verena; Doray, Mathieu; Peyronnet, Arnaud.
Several factors affect trawl catchability: (i) gear and vessel technical characteristics, (ii) anthropogenic factors, and (iii) biological factors. The objectives of this study were to assess the relative contribution of each factor to variations in hake (Merluccius merluccius) landings by the French trawler fleet operating on the shelf of the northern Bay of Biscay (ICES Subdivision VIIIa). Using generalized linear models, the impact of technical and anthropogenic factors was evaluated using landings per unit effort (lpue) obtained from logbooks. Variations in hake lpue were explained primarily by anthropogenic factors. For studying the biological components of catchability, the results of a scientific trawl survey in July 2006 involving three similar...
Tipo: Text
Palavras-chave: Accessibility; Beam trawl; Catchability; Fishing power; GLMM; Spatial distribution.
Ano: 2011
URL: http://archimer.ifremer.fr/doc/00021/13244/10287.pdf

Combining fleet dynamics and population dynamics for a volatile fishery: the example of the anchovy fishery of the Bay of Biscay
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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
Ano: 2012
URL: http://archimer.ifremer.fr/doc/00107/21858/19449.pdf

A future for marine fisheries in Europe (Manifesto of the Association Francaise d'Halieumetrie)
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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