Éditeur(s) : Wiley-blackwell
Résumé : 1. Approximately 300 pelagic fish species naturally aggregate around floating objects (FOBs) at the surface of the oceans. Currently, more than 50% of the world catch of tropical tuna comes from the industrial tuna fisheries around drifting FOBs. Greater understanding of the complex decision-making processes leading to this aggregation pattern and the impact of the massive release of artificial FOBs by fishermen on the spatial distribution and management of tuna is needed. 2. We analyse how the interplay between social (relationships between individuals) and non-social (responses to the environment) behaviours may affect the spatial distribution of a population in a multi-FOB environment. Taking the example of tropical tunas associating with FOBs and using differential equations and stochastic simulations, we examine how, when increasing the number of FOBs, fish aggregation dynamics and the distribution of the population among patches are affected by the population size, level of sociality and the natural retentive and/or attractive forces of FOBs on individual tuna. 3. Our model predicts that, depending on the species' level of sociality, fish will be scattered among FOBs or aggregated around a single FOB based on the number of FOBs deployed in a homogeneous oceanic region. 4. For social species, we demonstrated that the total fish catch is reduced with increasing FOBs number. Indeed, for each size of population, there are a number of FOBs minimizing the total population of fish associated with FOBs and another number of FOBs maximizing the total population of associated fish. 5. Synthesis and applications. In terms of fisheries management, the total catch volume is directly linked to the total number of floating objects (FOBs) for non-social species, and any limit on the number of sets would then result in a limit on the total catch. For social species (e.g. tuna), however, increasing the number of FOBs does not necessarily lead to an increase in the total catch, which is a non-intuitive result. Indeed, our model shows that, for specific values of the parameters, deploying a greater number of FOBs in the water (all other parameters being constant) does not necessarily help fishermen to catch more tuna, but does increase the level of fishing effort and bycatch.
Journal Of Applied Ecology (0021-8901) (Wiley-blackwell), 2013-10 , Vol. 50 , N. 5 , P. 1081-1092

Droits : 2013 The Authors. Journal of Applied Ecology, 2013 British Ecological Society
http://archimer.ifremer.fr/doc/00151/26275/24439.pdf
DOI:10.1111/1365-2664.12140
http://archimer.ifremer.fr/doc/00151/26275/

Résumé : By looking at the common thread between 4 programs* in which the IFREMER Palavas (34, Languedoc-Roussillon region in France) station took part, this report show the evolution over 20 years in the perception of the pathology of farmed fish, and of the sea bass in particular (Dicentrarchus labrax). During the 1990’s farming techniques became sufficiently reliable to enable to distinguish between problems of a zootechnical nature and those with a pathological origin. In anticipation of future illnesses, the necessary tools and monitoring were implemented in order to study the immune system of the sea bass. These methods arose from the recent creation of anti-immunoglobin monoclonal probes in the sea bass. These techniques, together with others, served to search for a solution to the nodavirus epidemic which struck in1996. In the absence of a cure for this virus, the research focused on knowledge of the virus, its epidemiology and vaccine development. Despite interesting scientific results, the solution withheld to curb the Nodavirus epidemic was zootechnical. This pragmatic outcome catalysed reflections on the role of pathology, leading to notions of health, animal well-being and image. Management choices in the health of farmed fish stocks became a parameter, amongst others, included in a global commercial and farming policy. * Définition des critères d’évaluation de l’immunocompétente chez le loup et le turbot. UMR1 Université Montpellier II IFREMER ; Nodavirus disease of cultured marine fish in Europe. FAIR PL98 4036 EU; Recherche de moyens de dépistage et prévention de la nodavirose du bar. ANVAR 9804041J ; Welfare and Health in Sustainable Aquaculture WEALTH. E.U N°501984.
En prenant comme fil conducteur les travaux de 4 programmes* auxquels a participé la station IFREMER de Palavas (34), ce rapport montre l’évolution sur 20 ans de la perception de la pathologie des poissons d’élevages et du loup en particulier (Dicentrarchus labrax). Dans les années 1990 les techniques d’élevages devinrent suffisamment fiables pour permettre de distinguer les problèmes d’origines zootechniques de ceux d’origines pathologiques. En prévision des futures maladies potentielles, les outils d’étude et de suivi du système immunitaire spécifique du loup furent mis en place. Ils découlaient de la création récente de sondes monoclonales anti-immunoglobulines de loup. Ces techniques, couplées à d’autres, servirent à chercher une solution à l’épidémie de nodavirose des années 1996. En l’absence de traitement pour un virus l’accent fut mis sur la connaissance du virus, de son épidémiologie et de la vaccination. Bien que les résultats scientifiques furent très satisfaisants la solution trouvée pour juguler l’épidémie de Nodavirose fut zootechnique. Cette issue pragmatique catalysa une réflexion sur le rôle de la pathologie qui maturait depuis plusieurs années et qui déboucha sur la notion de santé, de bien être des animaux et d’image. Les choix de gestion de la santé des cheptels devinrent un paramètre, parmi d’autres, s’incluant dans d’une politique globale d’élevage et commerciale * Définition des critères d’évaluation de l’immunocompétente chez le loup et le turbot. UMR1 Université Montpellier II IFREMER ; Nodavirus disease of cultured marine fish in Europe. FAIR PL98 4036 EU; Recherche de moyens de dépistage et prévention de la nodavirose du bar. ANVAR 9804041J ; Welfare and Health in Sustainable Aquaculture WEALTH. E.U N°501984.

Droits : 2013 Ifremer
http://archimer.ifremer.fr/doc/00167/27866/26103.pdf
http://archimer.ifremer.fr/doc/00167/27866/26105.pdf
http://archimer.ifremer.fr/doc/00167/27866/26106.pdf
http://archimer.ifremer.fr/doc/00167/27866/

Éditeur(s) : John Libbey Eurotext ltd
Résumé : How may fish domestication participate in sustainable development of aquaculture? The development of fish farming currently compensates for the stagnation of fishery catches while the market demand continues to increase. The development of fish farming relies on an active diversification of farmed fish species. A diversification based on the farming of native species could reduce the environmental impact of fish culture and could better fit to needs of local markets. Such development could also favour a more integrated local economy. In this context, the building of a generic approach for multi-species domestication is required to optimise the use of the technical and financial means available for fish culture diversification.
Cahiers Agricultures (1166-7699) (John Libbey Eurotext ltd), 2009-04 , Vol. 18 , N. 2 , P. 119-124

Droits : 2009 John Libbey Eurotext ltd
http://archimer.ifremer.fr/doc/2009/publication-6557.pdf
DOI:10.1684/agr.2009.0293
http://archimer.ifremer.fr/doc/00000/6557/

Éditeur(s) : Academic Press Ltd- Elsevier Science Ltd
Résumé : Ensuring the sustainability of fish resources necessitates understanding their interaction with coastal habitats, which is becoming ever more challenging in the context of ever increasing anthropogenic pressures. The ability of coastal lagoons, exposed to major sources of disturbance, to provide resources and suitable habitats for growth and survival of juvenile fish is especially important. We analysed three lagoons with different ecological statuses and habitat quality on the basis of their eutrophication and ecotoxicity (Trix test) levels. Fish abundances were sampled using fishing and horizontal beaming acoustic surveys with the same protocols in the same year. The relative abundance of Anguilla anguilla, Dicentrarchus labrax or the Mugilidae group was not an indicator of habitat quality, whereas Atherina boyeri and Sparus aurata appeared to be more sensitive to habitat quality. Fish abundance was higher in the two lagoons with high eutrophication and ecotoxicity levels than in the less impacted lagoon, while fish sizes were significantly higher in the two most severely impacted lagoons. This leads us to suggest low habitat quality may increase fish growth rate (by the mean of a cascading effect), but may reduce lagoon juvenile abundance by increasing larval mortality. Such a hypothesis needs to be further validated using greater investigations which take into account more influences on fish growth and recruitment in such variable environments under complex multi-stressor conditions.
Estuarine Coastal And Shelf Science (0272-7714) (Academic Press Ltd- Elsevier Science Ltd), 2013-07 , Vol. 126 , P. 1-6

Droits : 2013 Elsevier Ltd. All rights reserved
http://archimer.ifremer.fr/doc/00148/25963/24083.pdf
DOI:10.1016/j.ecss.2013.03.011
http://archimer.ifremer.fr/doc/00148/25963/

Éditeur(s) : Ecole Nationale Supérieure Agronomique de Rennes
Résumé : Long-line fishing has been growing on the island of La Réunion since the beginning of the 1990s. The target species is the swordfish (Xiphias gladius), fished mainly in the tropical waters surrounding the island between longitudes 45 degree E and 60 degree E, and latitudes 17 degree S and 27 degree S. From 1998 to 2000, a finalised research programme enabled the collection of precise data concerning the lines' positions and the parameters of the fishing efforts: 3,602 nettings were thus informed by the catches (in numbers of individuals caught) and 12 descriptive variables of the effort. In parallel with this collection effort, satellite maps that described the ocean's landscape of this region of the Indian Ocean exploited by La Réunion's fisheries were made available to sailors and scientists. Extractions from these environmental variables were made at the fishing lines' positions, which allowed us to propose 20 variables describing the environmental conditions of swordfish catches applied to the nettings. In an early part of this study, after a descriptive analysis and a first selection of the variables, we used several GAM (Generalised Additive Models) to model the respective effects of effort and environmental variables on the variability of swordfish catches. We thus highlighted the predominance of factors linked to fishermen (fishing effort) on oceanographic factors in the explanation of this variability. Following these results, a summary on the biology and ecology of the swordfish was proposed in order to draw up hypotheses on the characteristics of this species' population in the Indian Ocean. The aspects linked to the individual behaviour and movements of the population were particularly highlighted. In a latter part of this study and in order to complete the empirical approach by an exploratory constructivist approach, we proposed a modelling tool in order to simulate the possible movements of individuals within the oceanic landscape described by the available satellite maps. After reading in the literature about the various forms of modelling the movements of the large pelagics, we developed an original computer modelling architecture of the multi-agent type that made it possible to manipulate in a dynamic way the satellite maps (and derived products), the individual movements of "animats" whose behaviours were based on this environmental information, and agents that clarify the process of long-line fishing in a geographical way. The computer model that was implemented (MUFINS, for MUlti-Fish INdian ocean Simulator) was next used by calibrating the behaviour of the animats on the real data originally from the analysis of commercial catches proposed in the first part, using robust techniques based on fuzzy logic. The results of the simulations were compared, on the one hand, with the large-scale hypotheses of movement proposed in the first part, and, on the other hand, to swordfish catches both real and corrected for the effect of the fishing effort modelled by the GAM models. Even if the results of these simulations in this study do not allow for proposing convincing interpretations of the underlying processes, the MUFINS tool showed its ability to address questions associated with the swordfish's behaviour in the tropical oceanic landscape and to the effects of scale transfers between the individual level and the collective level. We now envisage its use in a more operational framework, as an interface for dialogue between fishermen and scientists with a goal of sustainable management of the resource.
La peche palangriere s'est developpee a l'ile de La Reunion depuis le debut des annees 1990. L'espece cible est l'espadon (Xiphias gladius), principalement exploite dans les eaux tropicales autour de l'ile entre les longitudes 45 degree E et 60 degree E, et les latitudes 17 degree S et 27 degree S. De 1998 a 2000, un programme de recherche finalisee a permis de collecter des informations precises concernant les positions des lignes et les parametres de l'effort de peche : 3602 filages sont ainsi renseignes par les captures (en nombre d'individus captures) et 12 variables descriptives de l'effort. En parallele de cet effort de collecte, des cartes satellitales ont pu etre mises a la disposition des marins et des scientifiques, decrivant le paysage oceanique de cette region de l'ocean Indien exploitee par la pecherie reunionnaise. Des extractions de ces variables environnementales ont ete effectuees aux positions des lignes de peche, nous permettant de proposer 20 variables descriptives des conditions environnementales de captures d'espadon appliquees aux filages. Dans une premiere partie de ce travail, apres une analyse descriptive et une premiere selection des variables, on a modelise par plusieurs modeles GAM (Generalized Additive Models) les effets respectifs des variables d'effort et des variables environnementales sur la variabilite des captures d'espadon. On a ainsi mis en evidence la predominance des facteurs lies aux pecheurs (effort de peche) sur les facteurs oceanographiques dans le caractere explicatif de cette variabilite. A la suite de ces resultats, une synthese sur la biologie et l'ecologie de l'espadon a ete proposee afin de degager des hypotheses sur les caracteristiques de la population de cette espece dans l'ocean Indien. Les aspects lies au comportement individuel et aux deplacements de la population ont ete particulierement mis en evidence. Dans une deuxieme partie de ce travail et afin de completer l'approche empirique par une approche constructiviste exploratoire, nous avons propose un outil de modelisation afin de simuler les deplacements possibles d'individus au sein du paysage oceanique decrit par les cartes satellitales disponibles. Apres avoir passe en revue dans la litterature les differentes formes de modelisation des deplacements des grands, pelagiques, nous avons developpe une architecture originale de modelisation informatique de type multi-agents permettant de manipuler de maniere dynamique les cartes satellitales (et les produits derives), les mouvements individuels < d'animats >, dont les comportements sont bases sur cette information environnementale, et des agents qui explicitent le processus de capture palangriere de maniere geographique. Le modele informatique ainsi implemente (MUFINS, pour MUlti-Fish INdian ocean Simulator) a ensuite ete utilise en calibrant les comportements des animats sur les donnees reelles issues de l'analyse des captures commerciales proposee en premiere partie, a partir de techniques robustes basee sur la logique floue. Les resultats des simulations ont ete confrontes d'une part aux hypotheses de deplacement a grande echelle proposees en premiere partie, et d'autre part aux captures d'espadon reelles et corrigees de l'effet de l'effort de peche modelise par les modeles GAM. Meme si les resultats de simulations presentes dans ce travail ne permettent pas de proposer d'interpretations convaincantes des processus sous-jacents, l'outil MUFINS a demontre son aptitude a aborder les questions liees au comportement de l'espadon dans le paysage oceanique tropical et aux effets des transferts d'echelle entre le niveau individuel et le niveau collectif. On envisage desormais son utilisation dans un cadre plus operationnel, comme interface de dialogue entre les pecheurs et les scientifiques a des fins de gestion durable de la ressource.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2005/these-2592.pdf
http://archimer.ifremer.fr/doc/00000/2592/

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : L’algue est une ressource marine peu étudiée par la géographie ; elle offre pourtant des potentialités de développement économique. Les macro-algues cultivées à des fins alimentaires sont une alternative à la pêche. Les micro-algues constituent une biomasse valorisable : molécule pharmaceutique, Oméga 3 et biocarburants. De ces différents usages naît la question suivante : les algues sont-elles une ressource marine à exploiter pour développer durablement les territoires de la zone intertropicale ? Nous présenterons tout d’abord l’algoculture à l’échelle mondiale en soulignant le faible poids de cette activité dans le bassin caribéen. Puis nous montrerons que l’algoculture s’inscrit dans un processus de développement durable en assurant un revenu à des communautés rurales (Petites Antilles). Enfin, dans une approche comparative (États-Unis), nous verrons que l’espace caribéen est une région de projets et d’aménagements durables qui a des atouts pour développer l’algoculture : exposition solaire, hautes températures, proximité de la recherche américaine.
Algae as sea resource have not been largely explored in Geography, yet it offers the potential for economic development. Macro-algae are cultivated for food purposes and they can substitute for fishing. Micro-algae can be valued as biomass: “nutraceutics”, Omega 3, biofuel. These various utilizations raise a question: are algae a key to a sustainable development in intertropical islands? We shall present Algaculture on a global scale, while emphasizing its low importance in the Caribbean. Then we shall show how algaculture can be part of a process of sustainable development by providing revenue to rural communities (Lesser Antilles). Finally, in a comparative approach (with the US), we shall see that the Caribbean Region has a number of assets for algaculture that make it suitable for sustainable projects and infrastructures: solar exposure, high temperatures, close to the US research centers.
États-Unis
Caraïbes

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.4389
http://journals.openedition.org/etudescaribeennes/4389

Éditeur(s) : HAL CCSD EDP Sciences
Résumé : International audience
In order to ensure a sustainable management of reef fisheries, data need to be collected regularly on the effect of these fisheries on both fish resources and the ecosystems that sustain them. Habitat and resources monitoring programs can provide such information, but are difficult to implement as they involve a range of technical, financial and human resources. Regarding these problems, the involvement of the local population in monitoring programs, called participatory monitoring, seems to offer solutions. Indeed, participatory monitoring has the potential of increasing the number of data collected at low cost, while taking advantage of the traditional ecological knowledge available locally. Some questions need clarifying, however: which methods can bring relevant information for the monitoring of reef fisheries while being appropriate to the motivations and skills of the local population? Is the degree of participation of the local population sufficient to make the monitoring program work, particularly over the long term? To answer these questions, participatory monitoring methods commonly used for coral reef ecosystems have been implemented to assess reef fisheries at three different sites: Moorea island and Tikehau atoll in French Polynesia, and the Bay of Tulear in Madagascar. While highlighting the relevance of some participatory monitoring programs for snapshot and large-scale surveys, the results of this study also show their lesser interest for regular data gathering on long-time scales. In any case, strong coordination and supervision by scientists are considered essential.
La gestion durable des écosystèmes coralliens nécessite de disposer d’informations régulières concernant l’impact des pêcheries sur les ressources récifales et sur les écosystèmes dont elles dépendent. Les suivis intégrés des ressources, des habitats et des espèces associées qui visent à fournir ce type d’informations sont difficiles à mettre en œuvre, car ils impliquent de nombreuses ressources humaines, techniques et financières. Face à ces problèmes, la participation de la société civile dans les programmes de suivi semble en mesure d’apporter des solutions. Dans le but de tester cette hypothèse, des méthodes de suivi participatif ont été mises en œuvre afin de caractériser des pêcheries récifales sur trois socio-écosystèmes contrastés : l’île de Moorea et l’atoll de Tikehau en Polynésie française, et le littoral de Tuléar à Madagascar. Les résultats de cette étude soulignent la pertinence de certains suivis participatifs pour fournir une vision écosystémique dans le cas de collecte de données ponctuelles et de large envergure, et leur intérêt moindre pour la collecte continue de données sur de longues échelles de temps. Dans tous les cas, une structure de coordination et l’implication de scientifiques s’avèrent primordiales pour assurer pérennité et fiabilité au système de suivi.
ISSN: 1240-1307

hal-01302983
https://hal-univ-perp.archives-ouvertes.fr/hal-01302983
DOI : 10.1051/nss/2013109

Éditeur(s) : Elsevier Science Bv
Résumé : Small-scale fisheries have traditionally received less research effort than large-scale fisheries and are generally under-studied in Europe. In spite of their comparatively low volume of catches and economic importance, small-scale fisheries are socially important and an integral part of the European coastal zone. Considering the high heterogeneity of situations and the paucity of quantitative data, we used an analytical methodology based on the comparative method. We carried out an analysis of small-scale fisheries (SSFs) in Europe based on a selection of nine case studies. Our objective was to obtain a comprehensive description of small-scale fleets covering different areas/fisheries/species, encompassing the diversity and specific conditions under which SSFs operate, in order to demonstrate the ecological and social sustainability of this often overlooked fisheries segment. A common approach formulated so that the case studies could be compared with the case histories of other competing users, required that for each set of criteria – technical, biological, socio-economic, and institutional – a set of relevant items and indicators was established. An analysis of characteristics common to the selected case studies is conducted and an attempt made to extend our comparisons to the whole of the European Union. Our results show that (as compared with large-scale fleets, their main competitor) small-scale fleets: (i) are composed of smaller vessels and, consequently, travel lower distances to fishing grounds, and are more reliant on coastal areas; (ii) have smaller crews (although the global employment figure is similar to that of large-scale fleets in Europe); (iii) use mostly, but not exclusively, passive gears; (iv) use multi-purpose fishing approaches, and can change the fish species they target during the year; (v) have lower extraction rates; (vi) have lower total capital investments (including fishing rights), turnover and costs; and (vii) have lower fuel consumption, making them less sensitive to changing oil prices. Dependence on subsidies is lower (viii). Involvement in fisheries management is variable, conservation and access regulation measures are largely local in origin. For the selected case studies, the most significant competitors are large-scale fleets, and recreational fisheries, but other sources of interaction (water quality, invasive species, etc.) cannot be ignored.
Fisheries Research (0165-7836) (Elsevier Science Bv), 2013-02 , Vol. 140 , P. 1-13

Droits : 2012 Elsevier B.V. All rights reserved
http://archimer.ifremer.fr/doc/00118/22934/20757.pdf
DOI:10.1016/j.fishres.2012.11.008
http://archimer.ifremer.fr/doc/00118/22934/

Éditeur(s) : Université du Littoral Côte d'Opale (Dunkerque)
Résumé : In the Bay of Biscay and Celtic Sea waters, hake is considered as genetically homogeneous and form a unique stock with identical meristic characteristics. The vertebral mean vary from 50,68 (vertebrae) during the first year of life to 51,11 (vertebrae) for adults. 0-group Merluccius display a rapid growth with significant interannual variability (0.71 mm.day-1 in 2001 versus 0.74 mm.day-1 in 2002). The spawning period occurs in April and the average length on the firth January following the hatching is of 17.3 cm (first seasonal check / increment on the sagittal otolith is located about 0.143 cm from the nucleus). At the end of the first year of life the average length is about 24 cm. The longevity of the species is important and growth parameters (L = 138,24 cm ; K = 0,132) explain natural mortality coefficient of M = 0.21. No difference for growth between male and female has been observed for this stock. The ratio total weight / eviscerated weight is equal to Fc = 1,086. Both male and female have same spatial and bathymetric distribution. Juveniles are found in deep waters (< 17 cm length) and move to coastal waters where they display an average length of (33 cm length). Longer individuals are found in nursery areas where they feed and grow then move to deeper areas to spawn. Nursery areas are numerous and located in the Celtic Sea and in the bay of Biscay. In the bay of Biscay, disturbances resulted from hydrondynamics affect the settlement on the nursery grounds particularly in the southern part of the bay. Diet composition varies with age. Juveniles feed mainly on crustaceans (Euphausia kroni). At the length of 23 cm, individuals feed strictly on fishes. Sizes of preys are proportional with sizes of predators and preys are composed mainly of species that feed and reproduce close to the bottom. Cannibalism has been observed for this specie, and increases with age notably in the northern part of the bay of Biscay and in the Celtic Sea. Main preys are 0-group juveniles. This specie is assumed to be a passive predator catching its preys when they come to feed in the bottom. Although they are punctual, these results have been obtained after studies on the evolution of sizes during the first year of life (daily increments measurements) and on the spawning period parameters (back-calculating). Average length on the firth January following hatching and the position of the first seasonal check on the otolith are based on observations of the sizes on the firth January following hatching (obtained with growth rates and spawning period parameters). The results are similar to those described in previous studies, nevertheless they have to be confirmed with growth and diet composition analyses. A long term study appear essential to determine biological and ecological parameters of this species for sustainable management of the stock.
Les alertes quant à la surexploitation du stock de merlu européen sont nombreuses et récurrentes. Seulement l'estimation du niveau réel de l'état du stock a toujours posé des problèmes du fait de certaines lacunes dans la connaissance de la biologie et de l'écologie de cette espèce. Dans les eaux du golfe de Gascogne et de la mer Celtique, le merlu européen fait partie de la même population génétique et possède les mêmes caractéristiques meristiques. Sa moyenne vertébrale est de 50,68 durant sa première année de vie et évolue pour se stabiliser à 51,11 chez l'adulte. La croissance du merlu durant sa première année de vie et très rapide mais présente une variabilité interannuelle significative (0,71 mm .J-1 en 2001 et 0,74 mm .J-1 en 2002). Sa période de ponte maximale se déroule au mois d'avril et sa longueur au premier janvier suivant sa naissance est de 17,3 cm (la première marque hivernale est positionnée à 0,143 cm du nucléus de la sagittae). Au terme de sa première année de vie le merlu atteint une longueur de 24 cm. Sa longévité est assez longue (23 ans environ) et ses paramètres de croissance (L = 138,24 cm ; K = 0,132) permettent d'estimer son coefficient de mortalité naturelle à M = 0,21. Il n'a pas été établi de croissance différentielle entre sexe chez le merlu dans ces eaux. Le rapport poids total / poids éviscéré a été estimé à Fc = 1,086. Mâles ou femelles, les merlus ont une même répartition spatiale et bathymétrique. En général, ils sont très profonds à leurs stades juvéniles (< 17 cm) et ils se dirigent vers les eaux côtières pour les atteindre à 33 cm de longueur environ. Au-delà de cette taille, les merlus se concentrent au niveau des zones de nourricerie pour s'y alimenter avant de rejoindre les eaux plus profondes pour y pondre. Les zones de nourricerie du merlu sont très nombreuses et sont localisées en mer Celtique et dans le golfe de Gascogne aussi bien dans sa partie sud que dans sa partie nord. Les perturbations importantes dans l'hydrodynamisme du golfe de Gascogne (upwelling) semble influencer les niveaux de colonisation des zones de nourricerie notamment celles situées dans la partie sud du golfe. Le régime alimentaire du merlu évolue avec l'âge. Juvénile, il se nourrit principalement de crustacés (Euphausia krohni) et devient ichtyophage exclusif dès 23 cm de longueur. Le cannibalisme est une réalité chez le merlu et les merlus-proies sont les juvéniles du groupe d'âge G-0. Il s'intensifie avec l'âge notamment dans la partie nord du golfe de Gascogne et en mer Celtique ; Il est très faible dans le sud du golfe de Gascogne. La taille des proies évolue avec la taille du merlu et les poissons proies sont en général des espèces qui vont se nourrir ou se reproduire sur le fond. Ce comportement alimentaire fait que le merlu est un prédateur peu actif et qui attaque ses proies lorsqu'elles viennent sur le fond. Ces résultats, bien qu'ils ne soient que ponctuels, ont été obtenus après avoir déterminé le schéma d'évolution de la longueur du merlu durant sa première année de vie (dénombrement des accroissement journaliers) et des paramètres de sa période de ponte (rétro-calcul).La taille au premier hiver et la position de la première marque hivernale ont été déterminées en relativisant nos observations à l'estimation de la longueur du merlu au premier janvier suivant sa naissance : celle-ci étant obtenue en utilisant le taux de croissance et les paramètres de la période de ponte. Bien que l'ensemble des résultats obtenus, en ce qui concerne la répartition spatiale et les données sur la période de ponte, soient généralement conformes à ceux décrits dans la littérature, il est nécessaire de confirmer ceux concernant la croissance et le régime alimentaire. Pour cela, une étude à plus long terme semble indispensable pour parvenir à bien maîtriser l'ensemble des paramètres de biologie et d'écologie du merlu permettant ainsi une meilleure gestion de son stock.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2004/these-1247.pdf
http://archimer.ifremer.fr/doc/00000/1247/

Éditeur(s) : Ecole nationale supérieure agronomique de Rennes
Résumé : Describe and gain understanding on fluctuations in animal population over time and space is a central goal of population ecology. This is also crucial to ensure the sustainable management of exploited resources, particularly those with complex population dynamics such as the bluefin tuna. The goal of this work is to collect bluefin tuna catches from the ancestral Mediterranean and Atlantic trap fisheries to (i) characterise long-term fluctuations in bluefin tuna population migrating in the Mediterranean, (ii) analyse their causes et (iii) assess their implications for fisheries management. The bluefin tuna main biological and ecological characteristics are first detailed. Then, the first part presents the trap fishery, and the process of collect and validation of the historical catches. This leads to develop a data base of 54 time-series more than 20 years long, the longest ones spanning about four centuries. Mean historical catches were around 15 000 tons/year ([7 000;25 000]). Time-series are analysed in a second part. Temporal variability of trap catches may be decomposed in three components: 100-year-long periodic fluctuations, 20-year cycles and inter-annual variations. These medium- to long-term fluctuations, representing more than 50% of the variability in the time-series, were synchronous all around the western Mediterranean and adjacent North Atlantic. In contrast, short-term variability was synchronous at a local scale only. It is argued that long-term fluctuations in trap catches could be considered as a proxy for those in abundance, and a synthetic time-series is computed to depict them. Biological and ecological processes that could cause such long-term fluctuations are discussed in a third part. We tested whether long-term fluctuations in Atlantic bluefin tuna might be related to large-scale environmental changes, using long time-series of the North Atlantic Oscillation (NAO), the Length of the Day index (LOD, a proxy of the atmospheric circulation index ACI) and the temperature. Spectral analyses of trap catches, LOD and temperature displayed similar spectra with peak at low frequency, whereas those of the NAO exhibited a broad band spectrum. Regression analyses and tests of correlation did not reveal any clear relationship between trap catches on the one hand and NAO and LOD on the other hand. In contrast, long-term fluctuations in trap catches appear to be negatively and significantly related to long-term trends in temperature. Underlying processes that could explain such a relationship are discussed, with special focus on changes in migration patterns. Finally, implications of such fluctuations in term of fisheries management are discussed in a fourth part. A simulation framework, in which a simulated population dynamics model is coupled with a VPA, is built to test the pertinence of the diagnostic of stock assessment according to different scenarios on fluctuations origins and population status. In the hypothesis of fluctuations linked to variations in the recruitment, VPA appears able to reconstruct the fluctuations but the predictions may be biased if natural fluctuations are not taking into account. In the hypothesis of fluctuations linked to changes in migration pattern, VPA is not able to reconstruct the population dynamics. In a precautionary approach, quotas which follow may be unsuitable in the best case, at worst dangerous if they are defined in comparison with a reference point. The concept of cible reference points, fixe and unique over time, appears not relevant for bluefin tuna; estimate trajectory reference pertinent may prove to be more pertinent.
Décrire et comprendre les fluctuations spatio-temporelles des espèces animales constituent les enjeux majeurs de l'écologie. La question est également cruciale pour réussir la gestion durable des ressources exploitées, en particulier celle du thon rouge, grand pélagique migrateur à la dynamique complexe. L'objectif de ce travail est de collecter les captures historiques de thon rouge par les madragues méditerranéennes et proche atlantiques pour (i) caractériser les fluctuations à long terme de la population migrante en Méditerranée, (ii) étudier leur déterminisme et (iii) évaluer leurs implications en terme de gestion des pêcheries. Après avoir décrit les principales caractéristiques biologiques et écologiques du thon rouge, la première partie présente la pêcherie à la madrague, puis le processus de collecte et de validation des données historiques de captures. Ce dernier conduit à la mise en place d'une base de données de 54 séries de plus de 20 ans, dont les plus longues s'étendent sur près de 4 siècles. Les productions historiques sont estimées à environ 15 000 tonnes/an ([7 000;25 000]). Les séries historiques de captures sont analysées dans la seconde partie. Leur variabilité temporelle peut être décomposée en trois composantes : de larges cycles pseudo-séculaires, des variations périodiques d'une vingtaine d'années et des fluctuations inter-annuelles. Les fluctuations à moyen et long terme, expliquant plus de la moitié de la variance des séries, sont synchrones à l'échelle du bassin méditerranéen occidental et du proche Atlantique. La variabilité inter-annuelle, en revanche, n'est synchrone qu'à une échelle locale. On montre finalement que les fluctuations à long terme des captures peuvent être considérées comme de bons indices des tendances des abondances de la population de thons rouges migrants en Méditerranée. Une série synthétique est construite pour les décrire. Les processus biologiques et écologiques susceptibles d'être à l'origine de ces fluctuations sont discutés dans la troisième partie. L'hypothèse d'un forçage environnemental à grande échelle est testée en utilisant des indices à long terme de l'Oscillation Nord Atlantique (NAO), de la longueur du jour (LOD, un indicateur de l'indice de circulation atmosphérique ACI) et de la température. Les analyses spectrales sur les séries de captures, du LOD et des températures révèlent des spectres similaires, avec un pic sur les basses fréquences, alors que celles sur le NAO conduisent à une large bande spectrale. Les régressions et les tests de corrélations ne montrent aucune relation significative entre les captures par les madragues et le NAO et le LOD. En revanche, les fluctuations à long terme des captures apparaissent significativement et négativement corrélées avec les fluctuations à long terme des températures. Les processus sous-jacents susceptibles d'expliquer une telle relation, en particulier des changements migratoires, sont discutés. Finalement, les implications des fluctuations pour la gestion de la pêcherie sont discutées dans une quatrième partie. Un cadre de simulation, couplant un modèle de dynamique de population à une VPA, est élaboré pour tester la pertinence des diagnostics d'évaluation de stock selon différents scénarios d'origine des fluctuations et d'état de la population. Dans l'hypothèse de fluctuations liées à des variations du recrutement, la VPA apparaît capable de reconstruire les fluctuations mais les prédictions sont biaisées lorsqu'il n'est pas tenu compte des fluctuations naturelles du stock. Dans l'hypothèse de fluctuations liées à des changements migratoires, la VPA est alors incapable de reproduire la dynamique de la population. Dans une approche de précaution, les quotas qui en découlent peuvent se révéler au mieux inappropriés, au pire dangereux s'ils sont définis par rapport à un point de référence. Ce concept de point cible, fixe et unique dans le temps, apparaît inapproprié pour le thon rouge ; estimer des "trajectoires de référence" serait sans doute plus pertinent.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2003/these-65.pdf
http://archimer.ifremer.fr/doc/00000/65/

Éditeur(s) : Ecole Nationale Supérieure Agronomique de Rennes (ENSAR)
Résumé : Artificial Fish Aggregating Devices (FADs) are known to concentrate tropical tunas. This aggregative behaviour drastically increases the vulnerability of these species to fishing. Alternatively, FADs can be used as oceanic observatories to study the aggregative behaviour of large pelagic fish. We conducted sea surveys in Martinique (Lesser Antilles) to i) establish a typology of the pelagic fish aggregations found around moored FADs ii) study their relations with their biotic and abiotic environment and the local fishery. The mean biomass of large pelagic fish aggregations was also estimated to provide scientific inputs to achieve a sustainable management of the moored FAD fishery. The first part presents the background of the study. We introduce the regional pelagic ecosystem, the aggregative behaviour of pelagic fish around FADs and the Martinican moored FAD fishery. The second part begins with a presentation of the conceptual framework of the study: the hierarchy theory. Observation scales and survey methodology are therefore described. Repeated echosounder surveys run in a star pattern were conducted around 2 moored FADs, in combination with underwater video observations, classical fishing experiments and CTD profiles. In the third part, the elements of the [moored FAD ¿ pelagic fish - environment - fishing] system and their interactions are numerically characterised in the vertical plane. The main type of pelagic fish aggregation was a large aggregation distributed in sub-surface (40-100 m) within a radius of 400 m of the FAD. This aggregation was mostly made of 60 cm FL blackfin tunas (Thunnus atlanticus). It appeared at sunrise and mostly spread away in the late afternoon. It was observed during all daytime surveys. The average density and the vertical structure of the micronektonic sound scattering layers (SSLs) were assessed locally around a FAD for 48h cycles. These SSLs descriptors showed positive correlation with the size and the abundance of the sub-surface tuna aggregation. Whereas this aggregation accounted for about 95% of the total biomass aggregated around a moored FAD, it was nearly unexploited by the local commercial fishermen. The fourth part focuses on the sub-surface tuna aggregation. A high variability of the spatial distribution of the aggregation was evidenced in the horizontal plane at daily, day to day and monthly temporal scales. These variations were related to fluctuations of the global abundance of the aggregation. The daytime average density of sub-surface tuna was modelled as a function of the distance to FAD, within an advection-diffusion framework. Based on these results, a universal kriging model was designed to assess the mean maximum daily biomass of the sub-surface tuna aggregation. This mean biomass estimate yielded 11 tons with an estimation error of 26%. To conclude, we present a hierarchical organization in space and time of a sub-surface tuna population distributed within a network of moored FADs, from micro to meso-scale. We suggest that the spatial distribution of tunas can be explained from fine to coarse-scales by behavioural processes (self-organization, feeding, aggregative behaviour) whereas their spatial distribution is mainly forced by environmental processes at broader scales.
L'utilisation de Dispositifs de Concentration de Poissons permet de provoquer la formation de larges agrégations de thonidés autour de dispositifs artificiels, ce qui augmente considérablement la vulnérabilité de ces ressources vis-à-vis de l'exploitation halieutique. Les DCP peuvent également être utilisés en tant qu'observatoires océaniques, afin d'étudier le comportement agrégatif du macronecton pélagique. Nous avons ainsi réalisé des observations autour de DCP ancrés en Martinique, afin de définir une typologie des agrégations de macronecton et de étudier leurs relations avec leur environnement biotique, abiotique et l'exploitation halieutique locale. Nous avons ensuite estimé la biomasse moyenne de macronecton agrégé autour d'un DCP ancré, afin de fournir des éléments scientifiques nécessaires à une gestion durable de ces ressources. La première partie présente le contexte de l'étude i.e. l'écosystème pélagique régional, le phénomène d'agrégation du macronecton autour des DCP et la pêche associée aux DCP ancrés en Martinique. La deuxième partie introduit la théorie de la hiérarchie qui a fourni le cadre conceptuel de l'étude et présente les échelles et méthodes d'observation. Le principal outil d'observation est un échosondeur scientifique, mis en oeuvre le long de parcours en étoile autour du DCP. Les prospections acoustiques ont été combinées à des observations vidéo sous marines, des pêches expérimentales et un suivi in-situ de l'environnement abiotique. La troisième partie présente une typologie des éléments constituant le système [DCP ancré - macronecton - environnement - pêche] dans le plan vertical et précise leurs interactions. Le type d'agrégation de macronecton dominant est une grande agrégation composée d'une majorité de thons noirs (Thunnus atlanticus) de taille moyenne (60 cm) distribuée en sub-surface (40-100 m), dans un rayon de 300 m autour de la tête des DCP. Cette agrégation se forme au lever du soleil et se disperse presque totalement dans l'après midi. Elle a été observée de jour lors de toutes les campagnes. Une corrélation positive entre la densité et la structure moyenne des couches micronectoniques diurnes évaluée localement autour du DCP au cours de 48 h et les dimensions et l'énergie acoustique de l'agrégation de thons de subs-surface a été mise en évidence. Malgré le fait que cette agrégation représente en moyenne 95 % de l'énergie acoustique du macronecton autour des DCP, elle est presque inexploitée par les pêcheurs artisans locaux. La quatrième partie met en évidence les fortes variations conjointes de la distribution spatiale dans le plan horizontal de la densité de l'agrégation de thons de sub-surface et de son abondance globale. Ces variations ont été observées au cours du cycle nycthéméral et aux échelles inter-journalières et mensuelles. La distribution spatiale moyenne de la densité diurne de l'agrégation en fonction de la distance au centre de gravité de l'agrégation est cependant très stable et peut être modélisée au moyen d'une équation d'advection-diffusion. Un modèle de krigeage universel, utilisant les résultats du modèle d'advection-diffusion, a permis d'évaluer la biomasse maximale journalière moyenne de l'agrégation de thons de sub-surface à une dizaine de tonnes, avec un coefficient de variation d'estimation de 26%. Nous proposons une représentation hiérarchique synthétique de la distribution spatiale d'une sous-population de thons dans un réseau de DCP ancrés de la micro à la méso-échelle. Nous suggérons que la distribution spatiale des thons est déterminée principalement à l'échelle fine (100m-1km) et à l'échelle grossière (1-10 km) par des processus comportementaux (auto-organisation, agrégation, nutrition) et par des processus environnementaux à échelle plus large.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2006/these-1735.pdf
http://archimer.ifremer.fr/doc/2006/sup-1735.pdf
http://archimer.ifremer.fr/doc/00000/1735/

Éditeur(s) : Elsevier
Résumé : 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 kinds of vessels with specific technical characteristics. Exploitation costs and revenues are considered at several levels: the fishing trip, the fishing unit (vessel and crew), and the vessel owner. The model is generic and can be used for different types of fisheries. A database is attached to the software for the storage and updating of information for each fishery. This includes the specification of model dimensions and of the parameters describing populations and exploitation. Several model assumptions regarding either population or exploitation may be adapted to suit a specific fishery. Both policies and corresponding fishers' response may be interactively specified through JAVA (TM) scripts. This version of ISIS-Fish allows for the calculation of biological and economic consequences of a range of policies, including conventional ones like catch and effort controls, and alternative policies such as marine protected areas. To facilitate policy-screening in a high-dimension parameter space, the software includes features, like interfaces for sensitivity analysis and simulation queues. (C) 2009 Elsevier B.V. All rights reserved.
Ecological Modelling (0304-3800) (Elsevier), 2009-04 , Vol. 220 , N. 7 , P. 1013-1033

Droits : 2009 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/2009/publication-6782.pdf
DOI:10.1016/j.ecolmodel.2009.01.007
http://archimer.ifremer.fr/doc/00000/6782/

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : L’organisation et la gestion des espaces publics en milieu urbain sont au centre des préoccupations de la puissance publique. Cet intérêt est lié dans les pays en développement aux nombreux dysfonctionnements recensés dans la ville. Ces difficultés sont entretenues par la démographie galopante, l’urbanisation informelle et à l’accroissement des activités industrielles, commerciales entre autres. À Dakar, la question de la mobilité urbaine est exacerbée par les puissants mouvements pendulaires entre la ville centrale et la périphérie amplifiés par les stationnements anarchiques et par l’inorganisation des modes de transports urbains.Le type d’espace public choisi pour cet article est une gare routière située au cœur du Plateau de Dakar : Petersen. Elle apparaît comme l’une des plus importantes gares routières du pays, surtout en matière de fréquentation avec plus de 50 000 personnes par jour. Le mode de gestion appliqué ici est la concession, une convention par laquelle la puissance publique confie la gestion de l’équipement à la SAGES une structure privée prenant en charge les intérêts parfois très contradictoires des différents acteurs.
The organization and management of public spaces in urban areas is a central concern of public authorities. This interest is linked in developing countries with numerous shortcomings identified in the city. These difficulties sustained by massive population growth, urbanization informal, and increased industrial activities, commercial and others. In Dakar, the question of urban mobility is exacerbated by the significant commuting between the city center and the periphery that are amplified by the chaotic parking lots and the disorganization of urban transport modes.The type of public space chosen for this article is a bus station in the heart of the Plateau de Dakar: Petersen. It appears as one of the largest bus stations in the country, especially in terms of attendance with over 50,000 people per day.The management method applied here is the concession, an agreement by which the public entrusts the management of equipment at the SAGES, a private organization that supports some very conflicting interests of different actors.
Sénégal
Dakar

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.7858
http://journals.openedition.org/etudescaribeennes/7858

Éditeur(s) : John Libbey Eurotext ltd
Résumé : The new sustainable development data repository requires new analysis grids, in particular for factors accounted for in productive system typologies. This paper, based on the aquaculture example, analyses the diversity in aquaculture systems with respect to sustainable development. Various typologies are obtained by evaluating structural and functional approaches integrating variables related to production and regulation systems and to the territorial insertion of fish farms. Categories have been defined on a scale based on a set of five sites, which are representative of a wider range of aquaculture systems. Use of these categories goes beyond the local typologies and prepares a generic meta-typology classification for the systems. This generic classification is then compared to the views of sustainable development held by the fish farmers working on the various types of farms.
Cahiers Agricultures (1166-7699) (John Libbey Eurotext ltd), 2009-04 , Vol. 18 , N. 2 , P. 199-210

Droits : 2009 John Libbey Eurotext ltd
http://archimer.ifremer.fr/doc/2009/publication-6560.pdf
DOI:10.1684/agr.2009.0297
http://archimer.ifremer.fr/doc/00000/6560/

Éditeur(s) : Wiley-blackwell
Résumé : Managing fisheries resources to maintain healthy ecosystems is one of the main goals of the ecosystem approach to fisheries (EAF). While a number of international treaties call for the implementation of EAF, there are still gaps in the underlying methodology. One aspect that has received substantial scientific attention recently is fisheries-induced evolution (FIE). Increasing evidence indicates that intensive fishing has the potential to exert strong directional selection on life-history traits, behaviour, physiology, and morphology of exploited fish. Of particular concern is that reversing evolutionary responses to fishing can be much more difficult than reversing demographic or phenotypically plastic responses. Furthermore, like climate change, multiple agents cause FIE, with effects accumulating over time. Consequently, FIE may alter the utility derived from fish stocks, which in turn can modify the monetary value living aquatic resources provide to society. Quantifying and predicting the evolutionary effects of fishing is therefore important for both ecological and economic reasons. An important reason this is not happening is the lack of an appropriate assessment framework. We therefore describe the evolutionary impact assessment (EvoIA) as a structured approach for assessing the evolutionary consequences of fishing and evaluating the predicted evolutionary outcomes of alternative management options. EvoIA can contribute to EAF by clarifying how evolution may alter stock properties and ecological relations, support the precautionary approach to fisheries management by addressing a previously overlooked source of uncertainty and risk, and thus contribute to sustainable fisheries.
Fish And Fisheries (1467-2960) (Wiley-blackwell), 2014-03 , Vol. 15 , N. 1 , P. 65-96

Droits : 2012 John Wiley & Sons Ltd
http://archimer.ifremer.fr/doc/00124/23522/21409.pdf
DOI:10.1111/faf.12007
http://archimer.ifremer.fr/doc/00124/23522/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The replenishment and persistence of marine species is contingent on dispersing larvae locating suitable habitatand surviving to a reproductive stage. Pelagic larvae rely on environmental cues to make behavioural decisionswith chemical information being important for habitat selection at settlement. We explored the sensory worldof crustaceans and fishes focusing on the impact anthropogenic alterations (ocean acidification, red soil, pesti-cide) have on conspecific chemical signals used by larvae for habitat selection. Crustacean (Stenopus hispidus)and fish (Chromis viridis) larvae recognized their conspecifics via chemical signals under control conditions. Inthe presence of acidified water, red soil or pesticide, the ability of larvae to chemically recognize conspecificcues was altered. Our study highlights that recruitment potential on coral reefs may decrease due to anthropo-genic stressors. If so, populations of fishes and crustaceans will continue their rapid decline; larval recruitmentwill not replace and sustain the adult populations on degraded reefs
ISSN: 0025-326X

hal-01491052
https://hal-univ-perp.archives-ouvertes.fr/hal-01491052
DOI : 10.1016/j.marpolbul.2016.08.083

Éditeur(s) : Copernicus Gesellschaft Mbh
Résumé : The Mediterranean Sea is one of the most oligotrophic marine areas on earth where nitrogen fixation has formally believed to play an important role in carbon and nitrogen fluxes. Although this view is under debate, the diazotrophs responsible for this activity have still not been investigated in the open sea. In this study, we characterised the surface distribution and species richness of unicellular and filamentous diazotrophs across the Mediterranean Sea by combining microscopic counts with size fractionated in situ hybridization (TSA-FISH), and 16S rDNA and nifH genes phylogenies. These genetic analyses were possible owing to the development of a new PCR protocol adapted to scarce microorganisms that can detect as few as 1 cell ml(-1) in cultures. Low concentrations of diazotrophic cyanobacteria were detected and this community was dominated at 99.9% by picoplankton hybridized to the Nitro821 probe, specific for unicellular diazotrophic cyanobacteria (UCYN). Among filamentous cyanobacteria only 0.02 filament ml(-1) of Richelia were detected in the eastern basin, while small (0.7-1.5 mu m) and large (2.5-3.2 mu m) Nitro821-targeted cells were recovered at all stations with a mean concentration of 3.5 cell ml(-1). The affiliation of the small Nitro821-targeted cells to UCYN-A was confirmed by 16S and nifH phylogenies in the western Mediterranean Sea. In the central and the eastern Mediterranean Sea no 16S rDNA and nifH sequence from UCYN was obtained as cells concentration were close to, or below PCR detection limit. Bradyrhizobium sequences dominated nifH clone libraries from picoplanktonic size fractions. A few sequences of gamma-proteobacteria were also detected in the central Mediterranean Sea. While low phosphate and iron concentrations could explain the absence of Trichodesmium sp., the factors that prevent the development of UCYN-B and C remain unknown. We also propose that the dominating picoplankters probably developed specific strategies, such as associations with protists or particles, and/or photosynthetic activity, to acquire carbon for sustaining diazotrophy.
Biogeosciences (1726-4170) (Copernicus Gesellschaft Mbh), 2011 , Vol. 8 , N. 3 , P. 827-840

Droits : Author(s) 2011. CC Attribution 3.0 License.
http://archimer.ifremer.fr/doc/00133/24392/22416.pdf
DOI:10.5194/bg-8-827-2011
http://archimer.ifremer.fr/doc/00133/24392/

Éditeur(s) : Pêche thonière et dispositifs de concentration de poissons, Caribbean-Martinique, 15-19 Oct 1999
Résumé : The original baitboat fishing technique using a permanent association between the fishing boat and the tuna school has been developed by the baitboat fleet of Dakar, Senegal and is also in use in the Canary Islands. This new fishing technique, the result of 20 years of improvements still on, has induced a dramatic increase of the catch yields which, in turn, has sustained the survival and even a recent development of the fleet. This technique is based on the aggregating behaviour of tropical tunas. However, it contains a dynamic component which is not found in tuna fishing on drifting or anchored fads. The specifications of the method, its refinement over the years and its main consequences for the fishery are described together with the school exchanges between baitboats over months even from one year to the next. Based on the analysis of 1228 recoveries from 5500 tagged fish, tuna movements among associated schools, between associated schools and free schools fished by purse seiners and movements in and out of the baitboat fishing grounds help to better understand the dynamics of tunas and schools of this peculiar tuna association. These data show a very high recovery rate, a remarkable tuna fidelity to the original school for all species, a small number of recoveries within the purse seine catch as well as the rare tuna movements outside the baitboat area. The study highlights the complexity and the numerous consequences of tuna and school behaviour.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00042/15304/12637.pdf
http://archimer.ifremer.fr/doc/00042/15304/

Éditeur(s) : Cambridge Univ Press
Résumé : This paper offers a theoritical and empirical model of ecosystem-based fishery management. A multi-species and multi-fleet integrating Lotka-Volterra trophic dynamics as well as production and profit assessments is developed and applied to the coastal fishery of French Guiana. This small-scale fishery constitutes a challenging example with high fish biodiversity, several non-selective fleets and a potentially increasing local food demand due to demographic growth. The dynamic model is calibrated with 13 species and four fleets using monthly catch and effort data from 2006 to 2009. Several contrasted fishing scenarios including status quo, total closure, economic and viable strategies are then simulated. They are compared from the viewpoints of both biodiversity preservation and socioeconomic performance, assuming fixed landing prices and fixed costs. We show that fishing outputs, including food supply and fleet profitability, can be sustained on average but a loss of species cannot be avoided.
Environment And Development Economics (1355-770X) (Cambridge Univ Press), 2013-06 , Vol. 18 , P. 245-269

Droits : Cambridge University Press 2013
http://archimer.ifremer.fr/doc/00124/23483/21311.pdf
http://archimer.ifremer.fr/doc/00124/23483/21375.pdf
DOI:10.1017/S1355770X13000065
http://archimer.ifremer.fr/doc/00124/23483/

Éditeur(s) : Pêche thonière et dispositifs de concentration de poissons, Caribbean-Martinique, 15-19 Oct 1999
Résumé : This paper develops a comparative overview of the development of Fish Aggregating Devices (or fads) by the tropical purse seine fisheries in various ocean areas (Atlantic, Indian, Western and Eastern Pacific Oceans). First, a comparative review of fishery statistics is developed. Recent catches on fads by purse seiners can be estimated at a level of one million tons yearly. This comparison allows to describe the fishing zones and catch trends over time, the species composition and size taken in the various fad fisheries. Skipjack tuna is the dominant species in most fad fisheries, but significant amounts of yellowfin and bigeye are also frequently taken under fads. The paper also presents an overview of various observer data concerning the by-catches of the various fisheries using fads. This comparison allows to estimate the total worldwide yearly by-catches at about 100,000 t, and their species composition in each ocean. The fad technology used in the various oceans by purse seiners is described. The recent use of fads by purse seiners has introduced major uncertainties in most stock assessments, because analyses are hampered by changes in the fishing effort in a fad fishery, by changes in fishing zones and in sizes caught. As a last point, the management of fads presently done or in view by the various tuna bodies are introduced. It appears that the present massive use of fads worldwide is perhaps an unsafe fishing mode, which could produce serious overfishing of many stocks. There is then a consensus that the use of fads needs to be controlled and limited to sustainable biological levels.

Droits : Ifremer
http://archimer.ifremer.fr/doc/00042/15278/12664.pdf
http://archimer.ifremer.fr/doc/00042/15278/