Dynamic Changes in Marine Ecosystems Fishing, Food Webs, and Future Options (2006) / Chapter Skim
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Summary
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Several scientific papers suggest that populations of high-trophic-level fishes have been severely depleted and that fishing has fundamentally altered the structure of marine ecosystems in many locations. But the conclusions drawn in these scientific papers often have been controversial.
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Direct predator-prey relationships have changed -- either releasing lower trophic levels from predation or reducing the availability of prey for higher-level predators -- and these effects may spread to successive trophic levels up and down the food web. Such cascading effects are often unforeseen and management actions frequently have unexpected results, especially if the target species plays a critical role in the ecosystem.
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In addition, environmental changes, such as climate-driven regime shifts, affect fishery productivity, creating conditions where recovery is even more uncertain. TRADEOFFS IN MANAGING MARINE FISHERIES Management decisions for a particular targeted stock will have impacts on the productivity of other interacting species.
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Other uses and values derived from marine resources should also be considered, because fishing activities directly or indirectly impact other ecosystem components and the goods and services they provide. A modeling framework is necessary to examine ecosystem interactions and to compare the possible outcomes of different fishery management actions.
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The challenge for scientists and managers is to identify and assign probabilities to a range of scenarios that capture existing uncertainties about food-web dynamics and responses of food webs to various fishing strategies. The proposed approach includes the creation of appropriate model scenarios for managed systems, the generation of a number of management strategies to be evaluated, and the determination of performance statistics for measuring policy outcomes that will reflect the interests of all stakeholders.
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Once there is a way to visualize all these different options, then a broad range of stakeholders can discuss which management schemes best achieve their collective goals and what tradeoffs are involved in deciding the management action that should be taken. Monitoring and regular assessments will be needed to feed the management process and to determine how well the previous actions achieve the intended outcome, and data should be collected on how essential ecosystem components changed.
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Models will improve as more is learned and greater levels of complexity are added, requiring an adaptive approach to management. Interdisciplinary working groups should be considered as a mechanism for developing appropriate models for each management area and for generating the series of scenarios needed to test proposed management actions.
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However, a potential benefit of secure access privileges is that they can foster a stewardship ethic among fishermen motivated by concern for the long-term health and productivity of the fishery. These approaches may also promote fishing innovations that reduce impacts to other ecosystem components if access to the fishery is predicated on limiting impacts on non-target species.
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Supporting Research Implementing scenario-based analysis; considering alternative management instruments; and integrating ecological, social, and economic values into fisheries management decisions require enhanced research in a number of areas. Scientific advances will need to incorporate new ideas, analyses, models, and data; perhaps, more importantly, new social and institutional climates will need to be established that catalyze a creative, long-term, comparative, and synthetic science of food webs and communities.
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Landings data, narratives and descriptions, fisheries-independent data, phytoplankton and plankton records, satellite data, archived specimens, empirical knowledge, and many other sources of information should all be considered when conducting these types of analyses. Research is needed to expand relevant social and economic information and to integrate this knowledge into fisheries management actions.
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Integrating this information into combined models would allow for the explicit consideration of all aspects of the management process -- the how and where of biological resource interactions and the how, where, and why of human actions. Finally, research should be conducted on how new governance mechanisms might better align fishing incentives to address more encompassing ecosystem management objectives.
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