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| Registros recuperados: 96 | |
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| Mesnil, Benoit; Rochet, Marie-joelle. |
| With political commitment to restore stocks to levels where they can produce maximum sustainable yield (MSY), fisheries managers request evaluations of management plans that include options for an FMSY policy. The procedure to estimate FMSY with dynamic-pool, stock assessment models is well established for common stock-recruitment relationships (S-RR). In this paper, we extend this capacity to another S-RR, a piecewise function known as the hockey stick, which is frequently assumed when the data do not support more elaborate functions. However, the hockey stick is not continuous, which makes it problematic for this application, where differentiable functions are required. The bent-hyperbola model proves to be an adequate continuous equivalent to the hockey... |
| Tipo: Text |
Palavras-chave: Bent hyperbola; F-MSY; Hockey stick; MSY; Stock-recruitment. |
| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00016/12735/9667.pdf |
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| Rochet, Marie-joelle; Rice, Jake. |
| An evaluation framework developed to help select an appropriate suite of indicators to support an ecosystem approach to fisheries management was tested experimentally by asking independent experts to weight the selection criteria provided and to score indicators against those criteria in several ecological settings. The steps in selecting indicators proved to be prone to subjectivity and value judgement, and differences in scores between experts were the main factor contributing to variability in evaluation results. Having to justify scores in a written document did not improve consistency among the experts. The framework, however, did enhance transparency by explicitly stating each issue to be addressed in the selection process, and by giving experts or... |
| Tipo: Text |
Palavras-chave: Selection criteria; Indicators; Fisheries management; Ecosystems; Criteria weights. |
| Ano: 2005 |
URL: http://archimer.ifremer.fr/doc/2005/publication-483.pdf |
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| De Lara, Michel; Doyen, Luc; Guilbaud, Therese; Rochet, Marie-joelle. |
| This paper deals with the control of nonlinear systems in the presence of state and control constraints for discrete-time dynamics in finite-dimensional spaces. The viability kernel is known to play a basic role for the analysis of such problems and the design of viable control feedbacks. Unfortunately, this kernel may display very nonregular geometry and its computation is not an easy task in general. In the present paper, we show how monotonicity properties of both dynamics and constraints allow for relevant analytical upper and lower approximations of the viability kernel through weakly and strongly invariant sets. An example on fish harvesting management illustrates some of the assertions. |
| Tipo: Text |
Palavras-chave: Monotonicity; Invariance; Viability; State constraints; Control. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2405.pdf |
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| Trenkel, Verena; Rochet, Marie-joelle; Sari, Tewfik. |
| There exists an urgent need in fisheries science for simple models for assessing the impact of fishing on the dynamics of fish communities. We present a new class of predator prey models that describe the relationship between predators and their prey by piecewise-linear differential equations. Interactions are governed by threshold values for population abundances. The simplest model has four distinct cases with different asymptotic stable states. The model allows for fishing mortality on both predator and prey. If fishing mortality on either the predator, the prey or both are varied, the system might move to new stable states. The threshold values act as reference points for fishing exploitation, as they indicate a structural change in the predator-prey... |
| Tipo: Text |
Palavras-chave: Predator-prey model; Reference points; Differential equations. |
| Ano: 2004 |
URL: http://archimer.ifremer.fr/doc/00453/56511/58207.pdf |
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| Blanchard, Julia L.; Jennings, Simon; Law, Richard; Castle, Matthew D.; Mccloghrie, Paul; Rochet, Marie-joelle; Benoit, Eric. |
| Widely observed macro-ecological patterns in log abundance vs. log body mass of organisms can be explained by simple scaling theory based on food (energy) availability across a spectrum of body sizes. The theory predicts that when food availability falls with body size (as in most aquatic food webs where larger predators eat smaller prey), the scaling between log N vs. log m is steeper than when organisms of different sizes compete for a shared unstructured resource (e.g. autotrophs, herbivores and detritivores; hereafter dubbed 'detritivores'). In real communities, the mix of feeding characteristics gives rise to complex food webs. Such complexities make empirical tests of scaling predictions prone to error if: (i) the data are not disaggregated in... |
| Tipo: Text |
Palavras-chave: Size spectrum; North Sea; Macroecology; Ecosystem effects of fishing; Community ecology; Benthic pelagic coupling; Allometric scaling. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2009/publication-7318.pdf |
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| Cornou, Anne-sophie; Rochet, Marie-joelle. |
| Ce document est le tableau de bord des rejets dans le golfe de Gascogne élaboré dans le cadre du projet REDRESSE - REDuction des REjets et Amélioration de la SElectivité dans le Golfe de Gascogne. Il présente une synthèse sur les quantités rejetées et la composition des captures et rejets des principaux métiers du golfe de Gascogne, ainsi que leurs variations annuelles de 2003 à 2014. Il a été élaboré sur la base des informations collectées de 2003 à 2014 à bord des navires de pêche professionnelle dans le cadre de l'action ObsMer. Cette action vise à observer in situ l'activité de pêche et l'ensemble de la capture, particulièrement la partie non retenue, en identifiant les espèces capturées, les tonnages par espèce et en prenant des mesures de tailles. |
| Tipo: Text |
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| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00379/48991/49428.pdf |
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| Cornou, Anne-sophie; Dimeet, Joel; Tetard, Alain; Gaudou, Olivier; Dube, Benoit; Fauconnet, Laurence; Rochet, Marie-joelle. |
| Ce document est une synthèse des informations collectées en 2012 à bord des navires de pêche professionnelle dans le cadre de l'action ObsMer. Cette action vise à observer in situ l'activité de pêche et l'ensemble de la capture, particulièrement la partie non retenue, en identifiant les espèces capturées, les tonnages par espèce et en prenant des mesures de tailles. |
| Tipo: Text |
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| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00167/27787/25978.pdf |
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| Dimeet, Joel; Rochet, Marie-joelle; Badts, Vincent; Dintheer, Christian; Dube, Benoit; Fauconnet, Laurence; Gaudou, Olivier; Messannot, Cecile; Morizur, Yvon; Tetard, Alain. |
| En 2011 le programme d’observation a continué à mobiliser des ressources substantielles, et à perfectionner ses outils et produits : évolution et suivi du plan d’échantillonnage, numérisation des bordereaux de terrain, analyse des refus d’embarquements par les professionnels, et édition d’un document de restitution des observations à l’intention des professionnels. L’équipe a également poursuivi ses efforts d’accompagnement du développement de la base de données halieutique et des logiciels qui l’environnent. Il est regrettable que ces efforts ne soient pas terminés et que de nouvelles difficultés viennent toujours compliquer et retarder la livraison d’une base de données enfin opérationnelle. Les progrès dans l’utilisation des données d’observation à la... |
| Tipo: Text |
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| Ano: 2012 |
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| Garcia, Serge; Kolding, Jeppe; Rice, Jake; Rochet, Marie-joelle; Zhou, Shijie; Arimoto, Takafumi; Borges, Lisa; Bundy, Alida; Dunn, Daniel; Graham, Norman; Hall, Martin; Heino, Mikko; Law, Richard; Makino, Mitsutaku; Rijnsdorp, Adriaan D.; Simard, François; Smith, Anthony D.m.; Symons, Despina. |
| The conventional selectivity paradigm is briefly reviewed and its performance examined from an ecosystem perspective. It is stressed that the overall (cumulative) selectivity of the harvest process in an ecosystem is the result of nested selection by fishers and fisheries of: (i) habitats; (ii) species assemblages; (iii) populations and (iv) individuals. A range of ecosystem models predict a strong impact of concentrated fishing (selective fishing) on the ecosystem structure stability, resilience and productivity. There seem to be advantages (in both yield and maintenance of ecosystem structure and functioning) to distribute fishing pressure broadly across available species and ecosystem compartments. Balanced harvesting was therefore defined by the... |
| Tipo: Text |
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| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00026/13697/10775.pdf |
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| Rochet, Marie-joelle; Collie, Jeremy S.; Jennings, Simon; Hall, Stephen J.. |
| This study challenges the widely held view that improved fisheries selectivity would always help to maintain marine biodiversity. Using a length-based multi-species model, we investigate the effects of selective versus nonselective fishing on fish communities. Both size and species selectivity are examined, and fishing effects on biodiversity are measured with three indices: (i) evenness, (ii) the number of collapsed species, and (iii) an index of size diversity. The model is parameterized for the Georges Bank and North Sea fish communities. The results suggest that there is no "optimal" size selectivity to maintain biodiversity: the effects of each exploitation pattern depend on the selectivity of the gear (i. e., the shape of the selection curve)... |
| Tipo: Text |
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| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00031/14263/11607.pdf |
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| Rochet, Marie-joelle; Trenkel, Verena; Carpentier, Andre; Coppin, Franck; Gil De Sola, Luis; Leaute, Jean-pierre; Mahe, Jean-claude; Maiorano, Porzia; Mannini, Alessandro; Murenu, Matteo; Piet, Gerjan; Politou, Chrissi-yianna; Reale, Bruno; Spedicato, Maria-teresa; Tserpes, George; Bertrand, Jacques. |
| P>1. The development of ecosystem approaches to environmental management implies the need to account for multiple pressures on ecosystems. Trends in multiple metrics that respond differently to changes in major environmental pressures need to be combined to evaluate the impacts of fishing and environmental changes on fish communities. 2. An exploited fish community is viewed as a three-level food chain in which the two upper levels, or functional groups, are targeted by fishing fleets, while the lowest level is subject to environmental variation. Qualitative modelling is used to predict changes at the two upper levels, that is, top-down vs. bottom-up perturbations. Abundance and length metrics are calculated from survey data for 14 Mediterranean and... |
| Tipo: Text |
Palavras-chave: Bottom-up control; Community metrics; Compensation; Ecosystem approach to fisheries; Ecosystem assessment; Functional groups; Groundfish community; Mediterranean; North Atlantic; Top-down control. |
| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00008/11925/8637.pdf |
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| Rice, Jake; Rochet, Marie-joelle. |
| We develop a framework for the objective selection of a suite of indicators for use in fisheries management. The framework encompasses eight steps, and provides guidance on pitfalls to be avoided at each step. Step I identifies user groups and their needs, featuring the setting of operational objectives, and Step 2 identifies a corresponding list of candidate indicators. Step 3 assigns weights to nine screening criteria for the candidate indicators: concreteness, theoretical basis, public awareness, cost, measurement, historic data, sensitivity, responsiveness, and specificity. Step 4 scores the indicators against the criteria, and Step 5 summarizes the results. Steps 3-5 offer technical aspects on which guidance is provided, including scoring standards... |
| Tipo: Text |
Palavras-chave: Scoring; Objectives; Indicators; Guidelines; Framework; Ecosystem; Criteria. |
| Ano: 2005 |
URL: http://archimer.ifremer.fr/doc/2005/publication-484.pdf |
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| Bertrand, Jacques; Cochard, Marie-laure; Coppin, Franck; Le Pape, Olivier; Mahe, Jean-claude; Morin, Jocelyne; Poulard, Jean-charles; Rochet, Marie-joelle; Schlaich, Ivan; Souplet, Arnauld; Trenkel, Verena; Verin, Yves. |
| The scientist community, the fishing organisations and all involved parties show a growing interest in an integrated project management of the sea space exploited by fishing communities. A key to reach such a target is to make available reliable and precise scientist data on the different components of the fishing systems. For about twenty years, and in its mission to support the development of an integrated management for a sustainable use of marine resources, Ifremer has been organising monitoring campaigns of fishery resources along the shores of France. These campaigns aim at providing abundance indicator on species of interest. They consequently provide an essential knowledge base to characterize and trace the status of exploited fish and... |
| Tipo: Text |
Palavras-chave: Ecosystem; Indicating; Oceanographical campaign; Scientific research; Fishing halieutic; Fishing; English Channel; Bay of Biscay; France; Invertebrate; Pisces; Ecosystème; Indicateur; Campagne océanographique; Recherche scientifique; Pêche halieutique; Pêche; Mer du nord; Golfe de gascogne; Manche; France; Invertebrate; Pisces. |
| Ano: 2005 |
URL: http://archimer.ifremer.fr/doc/2005/rapport-1091.pdf |
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| Registros recuperados: 96 | |
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