Marc Mangel

Ecosystem-Based Fishery Management

Ecosystem-based fishery management (EBFM) is a new direction for fishery management, essentially reversing the order of management priorities so that management starts with the ecosystem rather than a target species. EBFM aims to sustain healthy marine ecosystems and the fisheries they support. Pikitch et al . describe the potential benefits of implementation of EBFM that, in their view, far outweigh the difficulties of making the transition from a management system based on maximizing individual species.

The evolutionary advantages of group foraging

Abstract The relationship between the evolutionary fitness of individual foragers and the size of foraging groups is investigated by means of a series of simple mathematical models. Two alternative formulations of the contribution of foraging to fitness are considered, namely average feeding rate and probability of survival. The competitive aspects of group interaction are also considered, as are questions pertaining to the use of information. The latter leads to the concept of Behaviorally Robust Strategies.

IMPLEMENTING THE PRECAUTIONARY PRINCIPLE IN FISHERIES MANAGEMENT THROUGH MARINE RESERVES

Overexploitation of marine fisheries remains a serious problem worldwide, even for many fisheries that have been intensively managed by coastal nations. Many factors have contributed to these system failures. Here we discuss the implications of persistent, irreducible scientific uncertainty pertaining to marine ecosystems. When combined with typical levels of uncontrollability of catches and incidental mortality, this uncertainty probably implies that traditional approaches to fisheries management will be persistently unsuccessful. We propose the use of large-scale protected areas (marine reserves) as major components of future management programs. Protected areas can serve as a hedge against inevitable management limitations, thus greatly enhancing the long-term sustainable exploitation of fishery resources. Marine reserves would also provide an escape from the need of ever more detailed and expensive stock assessments and would be invaluable in the rehabilitation of depleted stocks.

Towards a Unifield Foraging Theory

In the broadest sense, foraging adaptations can include problems of finding food, avoid- ing predation while looking for food, and reproducing. In this paper, a theory that treats these three behaviors in a consistent, unified manner, with one common currency, is presented. The theory is called unified foraging theory, although it actually pertains to a wider class of behavioral problems. The theory is based on models using Markovian decision processes and leads to quantitatively testable predictions about behavioral strategies.

Modelling the proximate basis of salmonid life-history variation, with application to Atlantic salmon, Salmo salar L.

Summary The great diversity of life-history patterns in the salmonids has stimulated many theoretical studies. However, virtually all studies are based on ultimate considerations, in which predictions are made by comparing the expected reproductive success of diAerent developmental or life-history pathways and choosing the one (or ones) with the highest fitness. Such models are post hoc because they attribute fitness to individuals at the completion of the particular phase of the life cycle and do not attempt to characterize the mechanisms that animals use to achieve the life-history pattern. We describe a model, based on proximate considerations, for salmonid life histories, focused on Atlantic salmon Salmo salar L. The model involves identification of the times at which developmental conversions are initiated or inhibited and the connection between physiological states and the thresholds for such conversions. Developmental paths are based on the comparison of the current physiological status of the fish (and its change of state) with a genetic threshold. The state of the fish and rate of change of state are determined by environmental opportunity, but the threshold is genetic. This approach therefore immediately generates a genotype‐environment interaction. We use expected reproductive success to determine the fitness of individuals with diAerent genetically determined thresholds. Instead of finding an optimal life history, our theory generates fitness surfaces for diAerent life histories, so that variation is inherent in this approach. We describe and explain the structure of the model and present evidence on which this structure is based, thus providing a framework within which one can understand how ecology relates to the physiological mechanisms leading to the developmental changes of smolt metamorphosis and maturation.

Fugitive Salmon: Assessing the Risks of Escaped Fish from Net-Pen Aquaculture

Abstract The farming of salmon and other marine finfish in open net pens continues to increase along the worlds coastlines as the aquaculture industry expands to meet human demand. Farm fish are known to escape from pens in all salmon aquaculture areas. Their escape into the wild can result in interbreeding and competition with wild salmon and can facilitate the spread of pathogens, thereby placing more pressure on already dwindling wild populations. Here we assess the ecological, genetic, and socioeconomic impacts of farm salmon escapes, using a risk-assessment framework. We show that risks of damage to wild salmon populations, ecosystems, and society are large when salmon are farmed in their native range, when large numbers of salmon are farmed relative to the size of wild populations, and when exotic pathogens are introduced. We then evaluate the policy and management options for reducing risks and discuss the implications for farming other types of marine finfish.

Principles for the Conservation of Wild Living Resources

We describe broadly applicable principles for the conservation of wild living resources and mechanisms for their implementation. These principles were engendered from three starting points. First, a set of principles for the conservation of wild living resources (Holt and Talbot 1978) required reexamination and updating. Second, those principles lacked mechanisms for implementation and consequently were not as effective as they might have been. Third, all conservation problems have scientific, economic, and social aspects, and although the mix may vary from problem to problem, all three aspects must be included in problem solving. We illustrate the derivation of, and amplify the meaning of, the principles, and discuss mechanisms for their implementation. The principles are: Principle I. Maintenance of healthy populations of wild living resources in perpetuity is inconsistent with unlimited growth of human consumption of and demand for those resources. Principle II. The goal of conservation should be to secure present and future options by maintaining biological diversity at genetic, species, population, and ecosystem levels; as a general rule neither the resource nor other components of the ecosystem should be perturbed beyond natural boundaries of variation. Principle III. Assessment of the possible ecological and sociological effects of resource use should precede both proposed use and proposed restriction or expansion of ongoing use of a resource. Principle IV. Regulation of the use of living resources must be based on understanding the structure and dynamics of the ecosystem of which the resource is a part and must take into account the ecological and sociological influences that directly and indirectly affect resource use. Principle V. The full range of knowledge and skills from the natural and social sciences must be brought to bear on conservation problems. Principle VI. Effective conservation requires understanding and taking account of the motives, interests, and values of all users and stakeholders, but not by simply averaging their positions. Principle VII. Effective conservation requires communication that is interactive, reciprocal, and continuous. Mechanisms for implementation of the principles are discussed.

Opposition site selection and clutch size in insects

Oviposition site selection and clutch size in parasitic insects can be viewed as problems in foraging theory. In this paper, a number of models for site selection and clutch size are developed, based on a dynamic state variable approach to optimal oviposition strategies. The models lead to predictions that are consistent with existing experimental data and suggest future experiments. Using these models shows the importance of constraints and state variables in the analysis of behavioral problems.

Ecology, Conservation, and Public Policy

▪ Abstract A new sense of urgency about environmental problems has changed the relationship between ecology, other disciplines, and public policy. Issues of uncertainty and scientific inference now influence public debate and public policy. Considerations that formerly may have appeared to be mere technicalities now may have decisive influence. It is time to re-examine our methods to ensure that they are adequate for these new requirements. When science is used in support of policy-making, it cannot be separated from issues of values and equity. In such a context, the role of specialists diminishes, because nobody can be an expert in all the aspects of complicated environmental, social, ethical, and economic issues. The disciplinary boundaries that have served science so well in the past are not very helpful in coping with the complex problems that face us today, and ecology now finds itself in intense interaction with a host of other disciplines. The next generation of ecologists must be prepared to inte...

No-take Reserve Networks: Sustaining Fishery Populations and Marine Ecosystems

Abstract Improved management approaches are needed to reduce the rate at which humans are depleting exploited marine populations and degrading marine ecosystems. Networks of no-take marine reserves are promising management tools because of their potential to (1) protect coastal ecosystem structure and functioning, (2) benefit exploited populations and fisheries, (3) improve scientific understanding of marine ecosystems, and (4) provide enriched opportunities for non-extractive human activities. By protecting marine ecosystems and their populations, no-take reserve networks can reduce risk by providing important insurance for fishery managers against overexploitation of individual populations. Replicated reserves also foster strong scientific testing of fishery and conservation management strategies. Reserve networks will require social acceptance, adequate enforcement, and effective scientific evaluation to be successful. Processes for reserve establishment should accommodate adaptive management so bounda...