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DocumentOther documentDoes social behavior influence the dynamics of aggregations formed by tropical tunas around floating objects? An experimental approach 2013
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No results found.Tropical tus associate with objects floating at the surface of the ocean, a behavior widely exploited by fish- ers. However, the respective roles played by environmental variables and behavioral processes (e.g., social behavior) in the formation of these aggregations remain elusive. To investigate the role of social behavior in the dymics of such aggregations, we used the biry choice approach. The experimental design com- prised two close and identical anchored fish aggregating devices (FADs) eq uipped with an echo sounder buoy to monitor the aggregated biomass of tu under each device. Alysis of the results entailed character- izing whether the aggregated biomass is distributed asymmetrically (indicative of social behavior playing a role in the dymics) or symmetrically between the two close and identical FADs, and comparing the results with theoretical distributions based on different definitions of basic units (individual fish or small schools). The results suggest that social interact ions underlie aggregation processes, which represents a major advance in our understanding of these aggregations, a priority for science-based fishery magement. While recogniz- ing the logistical and technical constraints, we encourage the development of experimental studies (e.g., in which animals are presented with controlled situations) to enhance our understanding of the behavior of large pelagic fish. -
MeetingMeeting documentStudy of alternative models of artificial floating objects for tuna fishery (experimental purse-seine campaign in the Indian Ocean) 2005
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MeetingMeeting documentHow much do fish aggregating devices (FADs) modify the floating object environment in the ocean? 2013
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No results found.Natural floating objects (e.g., logs) have always been a component of the habitat of tropical tus. However, the introduction of fish aggregating devices (FADs) modifies this environment. To assess the changes due to the deployment of FADs, we compared the spatial distribution of tural and artificial floating objects (FADs), using data from observers onboard tu purse seine vessels in the Indian Ocean from December 2006 to December 2008. Although tural objects occur more commonly in waters south o f 7°S and FADs are more common in waters north of 7°S, all types of floating objects can be found everywhere. Using different spatial scales (quadrats of size 1° 9 1°, 2° 9 2°, 5° 9 5°, and 10° 9 10°), we computed the proportion of FADs observed in quadrats without t- ural objects. The scale of 2° 9 2° quadrats represented a threshold: distributions of the two types of objects were different at scales smaller than this threshold. The strongest change that has occurred since the introduction of F ADs (besides the increased catches) has been the dramatic increase in the total number of floating objects. Since the introduction of FADs, the number of objects has at least doubled everywhere (except in the Mozambique Channel and Chagos) and in some areas (e.g., Somalia area) the multiplication factor has reached as high as 20 or 40. Our study sets the ranges of values of key parameters of the floating object environment, which are crucial in the design of future experimental studies aimed at investigating the impacts of FADs on the ecology of tus.
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Book (series)FlagshipThe State of the World's Land and Water Resources for Food and Agriculture (SOLAW)
Managing systems at risk
2011This edition of The State of the World’s Land and Water Resources for Food and Agriculture presents objective and comprehensive information and analyses on the current state, trends and challenges facing two of the most important agricultural production factors: land and water. Land and water resources are central to agriculture and rural development, and are intrinsically linked to global challenges of food insecurity and poverty, climate change adaptation and mitigation, as well as d egradation and depletion of natural resources that affect the livelihoods of millions of rural people across the world. Current projections indicate that world population will increase from 6.9 billion people today to 9.1 billion in 2050. In addition, economic progress, notably in the emerging countries, translates into increased demand for food and diversified diets. World food demand will surge as a result, and it is projected that food production will increase by 70 percent in t he world and by 100 percent in the developing countries. Yet both land and water resources, the basis of our food production, are finite and already under heavy stress, and future agricultural production will need to be more productive and more sustainable at the same time. -
Book (series)GuidelineDéveloppement de l’aquaculture. 4. Une approche écosystémique de l’aquaculture. 2011Les dimensions sociales et biophysiques des écosystèmes sont inextricablement liées de telle manière qu’un changement dans une seule dimension est très susceptible de générer un changement dans une autre. Bien que le changement est une conséquence naturelle des interactions complexes, il doit être surveillé et même géré si le taux et la direction du changement risquent de compromettre la résilience du système. “Une approche écosystémique de l’aquaculture (AEA) est une stratégie pou r l’intégration de l’activité dans l’écosystème élargi de telle sorte qu’elle favorise le développement durable, l’équité et la résilience de l’interconnexion des systèmes socio-écologiques.” Etant une stratégie, l’approche écosystémique de l’aquaculture (AEA) n’est pas ce qu’on a fait, mais plutôt comment on l’a fait. La participation des parties intéressées est à la base de la stratégie. L’AEA exige un cadre politique approprié dans lequel la stratégie se développe en plusieurs é tapes: (i) la portée et la définition des limites des écosystèmes et l’identification de la partie intéressée; (ii) l’identification des problèmes principaux; (iii) la hiérarchisation des problèmes; (iv) la définition des objectifs opérationnels; (v) l’élaboration d’un plan de mise en oeuvre; (vi) le processus de mise en oeuvre correspondant qui comprend le renforcement, le suivi et l’évaluation, et (vii) un critique des politiques à long terme. Toutes ces étapes sont informées par les meilleures connaissances disponibles. La mise en oeuvre de l’AEA exigera le renforcement des institutions et des systèmes de gestion associés de sorte qu’une approche intégrée du développement de l’aquaculture peut être mise en oeuvre et compte entièrement des besoins et des impacts d’autres secteurs. La clé sera de développer des institutions capables d’intégration, notamment en fonction des objectifs et des normes convenus. L’adoption généralisée d’une AEA exigera un couplag e plus étroit de la science, la politique et la gestion. Elle exige aussi que les gouvernements incluent l’AEA dans leurs politiques de développement de l’aquaculture, stratégies et plans de développement.
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Book (series)Technical studyFishing with beach seines 2011
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No results found.This document provides a global overview of beach seine fisheries and identifies key issues relevant for the responsible use of beach seines and the sustainable livelihoods of beach seine fishers. It also gives guidelines for fisheries managers and other stakeholders on how best to address the issues of management processes and measures, which have the mutually beneficial goals of restoring and conserving the health of fishery resources and their habitats and safeguarding the livelihoo ds of fishers and their communities. The document draws on the findings of case studies coordinated and funded by the Food and Agriculture Organization of the United Nations (FAO) Fisheries and Aquaculture Department in the Gambia, India, Kenya, Mozambique, Peru and Sri Lanka, and by the FAO/United Kingdom Department for International Development (DFID) Sustainable Fisheries Livelihoods Programme (SFLP) in Benin, Ghana and Togo. In addition to the findings of the case studies, other studies and publications on beach seines were reviewed and used for the preparation of this document.