Multi-agent simulations and ecosystem management: a review

Modeling human decisions in coupled human and natural systems: Review of agent-based models

http://www.oomvanlieshout.net/sander/work/docs/Birch2007EcolModel206_347.pdf

Rectangular and hexagonal grids used for observation, experiment and simulation in ecology

Pelagic fisheries Habitat selection and migration Schooling behaviour Avoidance Attraction and association Learning Effects of behaviour on fisheries and stock assessment by population dynamic models Effects of behaviour on stock assessment by acoustic surveys Other methods of stock assessment and fish behaviour.

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Dynamics of pelagic fish distribution and behaviour : effects on fisheries and stock assessment

Small pelagic fish contribute up to 50% of the total landing of marine species. They are most abundant in upwelling areas and contribute to food security. Exploited stocks of these species are prone to large interannual and interdecadal variation of abundance as well as to collapse. We discuss why small pelagic fish and fisheries are so “special” with regard to their biology, ecology, and behavior. Two adjectives can sum up the characteristics of pelagic species: variability and instability. Analyses of the relationships between small pelagic fish and their physical environment at different time-scales illustrate the complexity of the interplay between exploitation and environmental impacts. How small pelagic fish species are positioned and related within the trophic web suggests that these species play a central role in the functioning and dynamics of upwelling ecosystems. Finally, we discuss the sustainable exploitation of small pelagic fisheries through appropriate management, focusing on the resilience to exploitation, a comparison of different management options and regulatory mechanisms. We recommend that statistical, socio-economical, and political merits of a proposed two-level (shortand long-term) management strategy be undertaken. Despite constant progress in understanding the complex processes involved in the variability of pelagic stock abundance, especially at short and medium time scales, our ability to predict abundance and catches is limited, which in turn limits our capacity to properly manage the fisheries and ensure sustainable exploitation. Substantial progress can be expected from an integrated modeling approach of spatialized models coupling hydrodynamics, biogeochemical, and ecological processes. Although there are many definitions of “small pelagic fish,” this expression most commonly refers to shoaling epipelagic fish characterized by high horizontal and vertical mobility in coastal areas and which, as adults, are usually 10–30 cm in length. The upper limit is often the most debated, since some authors use the term “medium-sized pelagic fish” to designate larger fish ranging from about 20–60 cm (Bas et al., 1995). This distinction between the two size groups simultaneously allows distinctions to be made with regard to the position of the species within the food web: the conventional “small pelagic fish” includes typical forage species like sardine and anchovy preying on phytoplankton and/or micro-mesozooplankton, while the group of “medium-sized pelagic fish” includes mostly species from intermediate trophic levels like horse-mackerel, mackerels, and coastal tunas. When adult, the latter species prey mainly on macro-zooplankton, ichthyoplankton, and small fish or mollusks. In this work, we will focus mainly on the conventional “small pelagic fish,” but will also often refer to, or contrast findings with, medium-sized pelagic fish. When referring to both small and medium-sized pelagic fish, we will use the terms “pelagic fish” or “coastal pelagic fish” to separate them from the large oceanic tunas, although not all medium-sized pelagic fish remain on the continental shelf for the duration of their whole life cycle. BULLETIN OF MARINE SCIENCE, VOL. 76, NO. 2, 2005 386 Small pelagic fish are abundant in all oceans and seas except the Antarctic, where large euphausids (a schooling species of zooplankton) constituting the krill occupy a similar trophic level. According to FAO data (FAO, 2002; Fig. 1), small pelagic fish contributed up to 39 million t or 50% of the total landing of marine species. The ratio of pelagic/demersal catches varied from 1.0–2.1 over the last 51 yrs, with a positive trend at least partly related to overexploitation of the higher trophic levels (Pauly et al., 1998). Although these official landing statistics are likely to be inaccurate for some countries (Watson and Pauly, 2001), the relative values given here provide consistent trends during the last decades. Despite their usually low commercial value, small pelagic fish provide a substantial source of income for many developing countries due to their abundance, especially in the four major upwelling regions located on the eastern border of the Pacific and Atlantic Oceans. In these regions, a few species of small pelagic fish represent a large amount of the total fish biomass. This is typically the case for Peru (Peruvian anchoveta and sardine) and Chile (anchoveta, sardine and also horse-mackerel, a mediumsized pelagic species) in the Humboldt Current ecosystem, Mauritania and Senegal (sardine and sardinella) in the Canary Current ecosystem, Namibia and South Africa (sardine, anchovy and horse-mackerel) in the Benguela Current ecosystem and, to a lesser extent, Mexico (sardine and anchovy) in the California Current ecosystem. In this work we will often refer to these productive areas and others, such as the Kurushio-Oyashio Extension (Japanese sardine), the North Sea and the Norwegian Sea (the latter two being inhabited by several herring stocks) or the Gulf of Guinea (sardinellas). In some of these regions, coastal pelagic fish contribute substantially to food security, either directly (human consumption of fresh, smoked, or frozen fish) or indirectly (income for a component of society). Many examples of small pelagic fishery collapses occurred during the second half of the 20th century (Figs. 2A,B) and, in most cases, these collapses were clearly associated with an abrupt decline in the corresponding fish stock biomass with delayed reFigure 1. World pelagic and demersal marine fish catch from 1950–1999 (data source FAO, FishStat, www.fao.org). FREÓN ET AL.: SUSTAINABLE EXPLOITATION OF SMALL PELAGIC FISH STOCKS 387 covery, if any (Troadec et al., 1980; Beverton, 1990; Hutchings, 2000). Whether these biomass variations were mainly driven by natural variability (due to environmental changes and/or species interactions), exploitation, or both has been, and is still, debated at length (Lluch-Belda et al., 1989; 1992a; Schwartzlose et al., 1999). In this work we will try to shed more light on this issue and propose management strategies aimed at minimizing the risk of stock and fishery collapse. This introduction is followed by four sections and a final section of general conclusions and recommendations. In the first section we explain why small pelagic fish and fisheries are “unique” in terms of their biology, ecology, behavior, and commercial aspects. The second section gives details on the relationships between small pelagic fish and their physical environment at different time-scales. The third section indicates how small pelagic fish are related within the trophic web and presents some modeling approaches in this regard. Finally, the fourth section deals with the sustainable exploitation of small pelagic fisheries through appropriate management, focusing on the resilience to exploitation, different management options, and regulatory mechanisms. Figure 2. Catches of (A) sardine and (B) anchovy in the Pacific Ocean [source: Scientific Committee on Oceanic Researh Working Group (SCOR WP) 101]. BULLETIN OF MARINE SCIENCE, VOL. 76, NO. 2, 2005 388 WHY PELAGIC FISH AND FISHERIES ARE “UNIQUE” HABITAT By definition, pelagic fish live in the pelagic domain, that is, they move freely in the water-column where they spend most of their time. Most of the small pelagic fish species are epipelagic, that is, they live in the uppermost layer of the ocean, usually at depths of 0–200 m, although the limit of the deeper boundary varies according to the species and region. For instance, Sardinella aurita Valenciennes in Cuvier and Valenciennes, 1847 off the Gulf of Guinea migrate in deeper waters (>200 m) out of the upwelling season (Longhurst and Pauly, 1987). Many medium-sized pelagic fish are found in a wider range of depths, typically from the surface to 500 m. The view that pelagic fish are remote from the sea floor is largely incorrect. Firstly, a minority of pelagic species, such as herrings and capelins, are demersal spawners, laying adhesive eggs on the bottom (Blaxter and Hunter, 1982). Secondly, many pelagic species, especially medium-sized ones, are frequently found close to the bottom during daytime and are therefore vulnerable to semi-pelagic fishing gear and even to bottom trawls. Some of these species (e.g., horse-mackerel and mackerel) feed on or near the bottom, but for others, like the gilt sardine S. aurita, only the sediment found in their stomachs testifies to their bottom activity and suggests that they might make use of the bacterial film (Nieland, 1982). Therefore, the reason for large “pole shaped schools” (Petitgas and Levenez, 1996) several tens of meters high and of which only the base is in contact with the bottom for prolonged periods of time remains unclear. MORPHOLOGY Small pelagic fish are characterized by a streamlined body shape (fusiform and laterally compressed) and forked caudal fin. These characteristics make them good and fast swimmers, despite their small size. Another typical phenotypic trait of coastal pelagic fish is their discrete coloration, ranging from dark gray to silver. The flanks are usually highly reflective and the dorsal surface dark in order to render the fish inconspicuous to predators: light is reflected in such a way that it matches the background light against which the fish is viewed (Blaxter and Hunter, 1982). Pelagic fish are also capable of camouflage by adjusting the state of the melanophores on their dorsal surface. The body of most small pelagic fish species is fragile, comprised of soft tissue and a thin skin. Physical protection is provided by small scales that cover nearly the whole body in most species, and by the mucus produced by their skin. Scales and mucus are easily lost by manipulation or contact with fishing gears, leaving the thin skin exposed to wound infection by bacteria, fungal diseases, or external parasites. Small pelagic species are extremely frail

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Sustainable exploitation of small pelagic fish stocks challenged by environmental and ecosystem changes : a review

Sustainable management of renewable resources is often complicated by diversity and dynamic nature of the ecological and socioeconomic systems involved. As these system dynamics and interactions are highly complex and frequently unpredictable, there is a need to opt for transdisciplinary research addressing adaptive and integrated renewable resource management. Companion Modeling (ComMod) is a multi-agent systems (MAS)-based approach relying on synergistic effects between Role-Playing Games (RPG) and Agent-Based Models (ABM) to facilitate information sharing, collective learning, and exchange of perceptions to support negotiation, facilitate collective decision-making, and to strengthen adaptive resource management capacity. Iterative and adaptive sequences of field work and modeling activities allow inclusive and interactive participation of stakeholders during design, implementation, calibration, and validation steps of the models, as well as joint use to explore possible future scenarios. ComMod was implemented in a study of a conflict between two ethnic communities and a newly proposed national park in Northern Thailand. Deforestation, biodiversity conservation, and livelihoods were key issues discussed during RPG sessions, and subsequently represented in an ABM simulator. Consequently, local stakeholders learned about agro-ecological and socioeconomic dynamics and gained an increased awareness of these key issues. Mutual understanding was improved, and the importance of collaborative discussion, essential to negotiation and decision-making, became obvious. Finally, this Northern Thailand experience has shown that collaborative interactions between researchers and local stakeholders mediated by ComMod tools were supportive of improved communication among the conflicting parties and joint learning for adaptive and integrated sustainable management of renewable resources. (Resume d'auteur)

Companion modeling for integrated renewable resource management: A new collaborative approach to create common values for sustainable development

The influence of nest site selection on population dynamics is explored by considering two reproductive strategies. The first one, described as opportunist, is the most common in ecology. It postulates that an individual tries to select and track the optimal environmental conditions that maximize its total reproductive output. The second one, described as obstinate, comes from a generalization of "natal homing" recently proposed by Cury (1994). It assumes that a newborn individual memorizes early environmental cues that later determine its reproductive environment. We use an individual-based model named SEALAB to track artificial fish in a heterogeneous environment displayed as a lattice of hexagonal patches. The effects of two components of the lattice structure—namely the composition (amount of each patch type) and the configuration (spatial arrangement of patches)—on the success of the searching behavior are examined. For the obstinate strategy, whose searching behavior is characterized by a simple ran...

How spatial heterogeneity influences population dynamics: simulations in SEALAB

Dans de nombreuses applications de recherche, nous sommes confrontes a des systemes complexes, composes de differentes entites en interaction. Ceci est d'autant plus vrai dans les problemes d'environnement, qui combinent des aspects naturels, physiques et biologiques, avec des aspects humains, sociaux et techniques. Le temps et l'espace sont deux dimensions essentielles a prendre en compte, pour comprendre les processus en cours et la facon dont les acteurs peuvent les controler ou les inflechir. Les Systemes Multi-Agents (SMA) offrent un cadre conceptuel adequat pour simuler les dynamiques en interaction et comparer differents scenarios de gestion. Les Systemes d'Information Geographique (SIG) apportent des fonctionnalites d'analyse spatiale et de modelisation de differentes visions de l'espace : espace-support des activites des acteurs, espace-produit par ces activites et les processus naturels, espace-facteur qui conditionne les decisions des acteurs. Cette etude integre ces differentes visions de l'espace dans un environnement multi-agents, en considerant les objets spatiaux comme des agents. Cette demarche et les possibilites d'analyse qu'elle ouvre est illustree par un exemple de maitrise de l'embroussaillement par des pratiques de pâturage, en arriere-pays mediterraneen

Modéliser les configurations et les stratégies spatiales dans un système multi-agents pour la maîtrise de dynamiques d'embroussaillement

https://horizon.documentation.ird.fr/exl-doc/pleins_textes/pleins_textes_7/b_fdi_53-54/010016150.pdf

Modelling fish spatial dynamics and local density-dependence relationships: detection of patterns at a global scale

The purpose of the interdisciplinary Companion Modelling (ComMod) approach in renewable resource management is to facilitate collective learning, negotiation, and institutional innovation about concrete problems faced by rural communities. The objective of this communication is to present and to compare the effects of the ComMod approach on collective water management at three different pilot sites located in upper northern Thailand (two sites) and west-central Bhutan. At these sites, water management is a cross-cutting problem: the processes of agricultural commercialization and increased pressure on the land led to the need for stakeholders to agree on new rules for the management of limited water resources. In the Lingmuteychu watershed of Bhutan, water sharing at rice transplanting has been a perpetual issue, without a way forward, while in montane northern Thailand a looming water scarcity is linked to the increased demand from expanding irrigated horticultural cropping systems. The paper compares the way this approach was flexibly adapted and implemented at the three sites according to the local contexts. The main effects of the ComMod process at the three sites are then presented according to a common framework analysing the processes of collective learning, negotiation, and coordinated action that were stimulated. It emphasizes the following effects: learning about the current situation and awareness of a problem to be solved collectively, understanding each other's perceptions and common agreement on the nature of the problem, exploration of new management rules to solve the problem, and concrete implementation of institutional innovation. The discussion focuses on the factors contributing to, or limiting, the achievement of institutional innovation. The role of the local institutional context and the possibility to establish inter-institutional dialogue among multiple levels of organization is highlighted. Finally, we point out the need for specific monitoring & evaluation procedures adapted to such a highly participatory and adaptive process. (Resume d'auteur)

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Christophe Le Page

Papers

Companion modeling for integrated renewable resource management: A new collaborative approach to create common values for sustainable development

How spatial heterogeneity influences population dynamics: simulations in SEALAB

Modéliser les configurations et les stratégies spatiales dans un système multi-agents pour la maîtrise de dynamiques d'embroussaillement

Modelling fish spatial dynamics and local density-dependence relationships: detection of patterns at a global scale

Companion modelling for collective learning and action in water management: Lessons learnt from three case studies in northern Thailand and Bhutan