Marine ecosystems are being perturbed by fishing and other human activities. Many marine fisheries are in decline, and the effects of fishing on other ecosystem goods and services1 are beginning to be understood and recognized. In recent years, global marine catches appear to have reached a plateau of about 84 million metric tons2 per year, although total fish production, which includes aquaculture, has continued to increase. In some cases, fisheries have been entirely closed, and in many others it takes increasing effort to maintain catch rates. Fishing is also an economically important international industry, with first-sale revenues of approximately $U.S. 100 billion per year for all fishery products. (Farm-raised and freshwater fisheries account for approximately 25 percent by weight of all fishery products.) Globally, fishery products directly provided approximately 14 kg of food per person in 1996; approximately 28 percent of global fishery products was used for animal feed and other products that do not contribute directly to human food. Although in recent years total fish production has increased faster than the human population, the total from marine-capture fisheries has increased little if at all.
To evaluate whether current marine-capture fisheries are sustainable, to determine to what degree marine ecosystems are affected by fishing, and to assess whether an ecosystem approach to fishery management can help achieve
sustainability, the National Research Council's Ocean Studies Board established the Committee on Ecosystem Management for Sustainable Marine Fisheries. The committee was directed to ''assess the current state of fisheries resources; the basis for success and failure in marine fisheries management (including the role of science); and the implications of fishery activities to ecosystem structure and function. Each activity [was to] be considered relative to sustaining populations of fish and other marine resources" (Statement of Task). This report is the product of the committee's study.
Sustainability and Ecosystem-Based Management
The sea was long viewed as an inexhaustible supply of protein for human use. But recently, as the potential and actual adverse effects of human activities have become apparent, our views of marine ecosystems have changed. It has become increasingly clear that the ocean's resources are not inexhaustible. And, in addition to direct societal benefits from fishing, ecosystem goods and services have become recognized as valuable and irreplaceable natural resources. These insights have led to a concern regarding sustainability and an interest in the potential of ecosystem-based approaches to fishery management—two major themes of this report.
In its simplest sense, sustainable use of a resource means that the resource can be used indefinitely. But even a depleted resource can be used indefinitely at an undesirably low level, and perhaps with undesirable consequences. Therefore, by sustainable fishing, the committee means fishing activities that do not cause or lead to undesirable changes in biological and economic productivity, biological diversity, or ecosystem structure and functioning from one human generation to the next. Fishing is sustainable when it can be conducted over the long term at an acceptable level of biological and economic productivity3 without leading to ecological changes that foreclose options for future generations. The desired levels of biological and economic productivity are in part societal decisions, but it is clear that both could be greater than they are today. In many cases, of course, sustainable fishing implies a need to rebuild populations of exploited species and to promote recovery of ecosystems from effects of overexploitation. Ecosystem-based management is an approach that takes major ecosystem components and services—both structural and functional—into account in managing fisheries. It values habitat, embraces a multispecies perspective, and is committed to understanding ecosystem processes. Its goal is to achieve sustainability by appropriate fishery management.
Humans are components of the ecosystems they inhabit and use. Their actions on land and in the oceans measurably affect ecosystems, and changes in
ecosystems affect humans. Thus, sustainability of fisheries at an acceptable level of productivity and of the ecosystems they depend on requires a much broader understanding of appropriate and effective management than has been encompassed by traditional, single-species fishery management.
The Status of Marine Fisheries
Marine-capture fisheries include commercial, recreational, subsistence, and various small-scale fisheries, with total landings dominated by the commercial sector. In addition to recent reported annual landings of about 84 million t of marine animals (including fish, molluscs, crustaceans, and some other species), marine plants (seaweeds) also are used for food, as well as some marine mammals and turtles. Fishing as a source of food and revenue in less-industrialized countries, traditionally important, has become even more important recently and accounted for 65 percent of the world's catch in 1993.
In addition to fish and invertebrates that were caught and landed, approximately 27 million t of nontarget animals (bycatch) were discarded each year in the early 1990s (discards were probably less in the late 1990s). Furthermore, fishing causes mortality that is never observed because of illegal fishing, animals that die after escaping from fishing gear, or animals that are killed by abandoned fishing gear. Thus, the biomass of fish and invertebrates killed by ocean fishing (not including aquaculture) probably exceeds 110 million t per year.
Various estimates have been made of the total productivity of ocean ecosystems and the maximum long-term potential catch of marine animals. Many of the latter estimates are near 100 million t per year, suggesting that the current annual landings of 84 million t plus unreported mortality are near the maximum sustainable. However, considering species interactions, variations in the ability of individual species to withstand fishing mortality, global overfishing, and ecosystem degradation, it is possible that, under present management and fishery practices, the current catch cannot be exceeded or perhaps even continued on a sustainable basis. Considering individual stocks, about 30 percent globally are overfished,4 depleted, or recovering, and 44 percent are being fished at or near the maximum long-term potential catch rate.
In the United States, commercial marine fishery landings in 1996 were 4.5 million t, worth $3.5 billion (exvessel value, the value of first sales from a vessel). The total economic contribution of recreational and commercial fishing were each approximately $20 billion per year. However, approximately 33 percent of stocks that commercial and recreational fishers depend on were overfished
By overfishing the committee means fishing at an intensity great enough to reduce fish populations below the size at which they could provide the maximum long-term potential (sustainable) yield (see Chapter 2), or at an intensity great enough to prevent their recovery to that size. As described in this report, it follows that overfishing is a function of population size.
or depleted in 1994, while 49 percent were fished at or near the level where they could yield the maximum long-term potential catch. In 1994, only about 2 percent by weight of total marine landings were from recreational fishing, but for several species recreational landings exceeded commercial landings.
Fishing and Marine Ecosystems
Fishing and ecosystems interact, and both are affected by environmental changes and other human activities. Fishing obviously has direct effects on fished stocks. It can alter abundance, age and size structure, sex ratio, genetic structure of fished populations, and species composition of marine communities. Many important commercial species are at high trophic levels (they eat other fishes), and their removal can have especially large effects on ecosystems, perhaps out of proportion to their abundance or biomass. Fishing can also affect habitats, most notably by destroying and disturbing bottom topography and the associated benthic communities. Large-scale mariculture activities (farming of fish, shrimp, and other marine organisms)—especially if they are poorly managed—also can affect marine ecosystems through damage to coastal wetlands and nearshore ecosystems associated with the construction of shore-based or nearshore facilities; through contamination of the water with food, antibiotics, and waste; and through the introduction of diseases and exotic genotypes.
Fishing has had significant effects on many marine ecosystems, including changes in productivity, biological diversity, and provision of ecosystem goods and services. For example, fishing has contributed to large changes in coral-reef ecosystems in the Caribbean, including the death of corals, and it has resulted in significant changes in community structure in the Bering, Barents, and Baltic seas, on Georges Bank, and elsewhere. In combination with environmental changes and other human activities that have led to the degradation of habitats, pollution, and the introduction of exotic species, fishing has had major effects in the Laurentian Great Lakes, San Francisco Bay, and Chesapeake Bay. It seems likely that, unless fishing and other activities are managed better, human effects on marine ecosystems will increase.
Long- and short-term environmental fluctuations have major effects on the abundances of marine organisms. Some well-known environmental fluctuations are those precipitated by El Niño events, which change the patterns of Pacific Ocean currents and affect global weather every few years. El Niños lead to the intrusion of warm water into high latitudes and major changes in the distribution and abundance of many species. Other environmental fluctuations affect marine areas at varying spatial scales and periods ranging from a few weeks to decades and perhaps centuries. Environmental changes can produce effects similar to those of fishing, and it is often difficult to distinguish them from the effects of fishing. Although they cannot be controlled directly, environmental fluctuations exert a fundamental influence on the behavior of marine ecosystems and must be
taken into account by managers. To be sustainable, fishing and fishery management must be flexible and responsive to environmental changes as well as conservative of ecosystem components. Uncertainties about effects of environmental variability should not be used to excuse continued overfishing.
Conclusions and Recommendations
Many populations and some species of marine organisms have been severely overfished. There are widespread problems of overcapacity: there is much more fishing power than needed to fish sustainably. Fishing affects other parts of the ecosystem in addition to the targeted species, and those effects are only now beginning to be understood and appreciated. Other human activities, such as coastal development, have adverse effects on marine ecosystems as well. The effects of these human activities, combined with ecosystem effects of fishing, may well be more serious in the long term than the direct effects of fishing on targeted species. Although societies have been concerned about the effects of fishing on particular populations and species for centuries, recent recognition of the ecosystem effects of fishing has resulted in part from research on ecosystem approaches and has led to calls for the adoption of ecosystem approaches to fishery management to achieve sustainability at a high level of productivity of fish and of ecosystem goods and services.
The committee concludes that a significant overall reduction in fishing mortality is the most comprehensive and immediate ecosystem-based approach to rebuilding and sustaining fisheries and marine ecosystems. The committee's specific recommendations, if implemented, would contribute to an overall reduction in fishing mortality in addition to providing other protective measures.
The committee recommends the adoption of an ecosystem-based approach for fishery management whose goal is to rebuild and sustain populations, species, biological communities, and marine ecosystems at high levels of productivity and biological diversity, so as not to jeopardize a wide range of goods and services from marine ecosystems, while providing food, revenue, and recreation for humans. An ecosystem-based approach that addresses overall fishing mortality will reinforce other approaches to substantially reduce overall fishing intensity. It will help produce the will to manage conservatively, which is required to rebuild depleted populations, reduce bycatch and discards, and reduce known and as-yet-unknown ecosystem effects. Although this approach will cause some economic and social pain at first, it need not result in reduced yields in the long term because rebuilding fish populations should offset a reduction in fishing intensity and increase the potential sustainable yields. Reducing fishing effort in the short term is necessary to achieve sustainable fishing. The options lie in deciding how and when to reduce effort so as to reduce economic and social disruption. The
options, however, can be exercised only if decisions are made before the resources are depleted.
Adopting a successful ecosystem-based approach to managing fisheries is not easy, especially at a global or even continental scale. That is why the committee recommends incremental changes in various aspects of fishery management. The elements of this approach, many of which have been applied in single-species management, are outlined below. They include assignment of fishing rights or privileges to provide conservation incentives and reduce overcapacity, adoption of risk-averse precautionary approaches in the face of uncertainty, establishment of marine protected areas, and research.
When overfishing (including bycatch) has been effectively eliminated, other human activities will be the major threat to fisheries and marine ecosystems. Although those effects are not a major focus of this report, they cannot be totally separated from fishing, and mechanisms involving cross-sectoral institutional arrangements will be needed to protect fisheries and marine ecosystems.
The following are recommendations to achieve the broad goals and approach outlined above. Appropriate actions need careful consideration for each fishery and each ecosystem.
Conservative Single-Species Management
Managing single-species fisheries with an explicitly conservative, risk-averse approach should be a first step toward achieving sustainable marine fisheries. The precautionary approach should apply. A moderate level of exploitation might be a better goal for fisheries than full exploitation, because fishing at levels believed to provide the maximum long-term yield tends to lead to overexploitation. Many species are overfished and their productive potential is impaired, even without considering the ecosystem effects of fishing for them. Expanding fisheries to include previously unfished or lightly fished species, such as deep-sea species, is unlikely to lead to large, sustainable increases in marine capture fisheries. Therefore, the committee recommends that management agencies adopt regulations and policies that strongly favor conservative and precautionary management and that penalize overfishing, as called for in the Magnuson-Stevens Fishery Conservation and Management Act of 1976 and the 1996 amendments to that act, often referred to as the Sustainable Fisheries Act of 1996.
As described in Chapter 5, the committee's recommendation for more conservative and precautionary management requires that the concept of maximum sustainable yield be interpreted in a broader ecosystem context to take account of species interactions, environmental changes, an array of ecosystem goods and
services, and scientific uncertainty. This step, although important, will not by itself sustain marine fisheries and ecosystems at high levels of productivity.
Incorporating Ecosystem Considerations Into Management
Fishery management should take account of known and probable goods and services of marine ecosystems that are potentially jeopardized by fishing. The aim is to sustain the capacity of ecosystems to produce goods and services at local to global scales and to provide equitable consideration of the rights and needs of all beneficiaries and users of ecosystem goods and services.
Dealing with Uncertainty
Fisheries are managed in an arena of uncertainty that includes an incomplete understanding of and ability to predict fish population dynamics, interactions among species, effects of environmental factors on fish populations, and effects of human actions. Therefore, successful fishery management must incorporate and deal with uncertainties and errors. The committee recommends the adoption of a precautionary approach in cases of uncertainty. Management should be risk-averse. Although research and better information can reduce uncertainty to a degree, they can never eliminate it.
Many of the problems that fishery managers face are issues concerning long-term versus short-term goals and benefits. Uncertainty in stock assessments and in future allocations of those stocks has led to an emphasis on short-term benefits at the expense of long-term solutions. Uncertainties over shares when allocations allow open competition can compel individuals to adopt a short-term horizon for decisions related to fishing effort and investment. Management incentives and institutional structures must counteract these responses to uncertainty that jeopardize sustainability. This is especially true when stock assessments are uncertain, which makes it harder for managers to hold the line on conservation.
Reducing Excess Fishing Capacity and Assignment of Rights
Excess fishing capacity (fishing capacity is the ability to catch fish or fishing power) and overcapitalization (capitalization, related to capacity, is the amount of capital invested in fishing vessels and gear) reduce the economic efficiency of fisheries and usually are associated with overfishing. Substantial global reductions in fishing capacity are of the highest priority to help to reduce overfishing and to deal with uncertainty and unexpected events in fisheries. Overcapacity is difficult to manage directly, and usually evolves in management regimes that encourage unrestricted competition for limited fishery resources. Consequently, managers and policy makers should focus on developing or encouraging socio-economic and other management incentives that discourage overcapacity and
that reward conservative and efficient use of marine resources and their ecosystems.
At the core of today's overcapacity problem is the lack of, or ineffective, definition and assignment of rights in most fisheries. In addition, subsidies that circumvent market forces have contributed significantly to the overcapacity problem in many fisheries. Therefore, the committee recommends for many fisheries a management approach that includes the development and use of methods of allocation of exclusive shares of the fish resource or privileges and responsibilities (as opposed to open competition) and the elimination of subsidies that encourage overcapacity. A flexible and adaptive approach is essential, and careful attention must be given to equity issues associated with such approaches. The committee recommends experimental approaches to community-based fishery management, including the development of virtual communities. This would include research into the establishment of management groups in which participation is based on shared interests in a fishery and its associated ecosystem, with diminished emphasis on where participants live or their direct financial interests.
Marine Protected Areas
Where they have been used, marine protected areas—where fishing is prohibited—have often been effective in protecting and rebuilding ecosystems and populations of many (but not all) marine species. They often also lead to increases in the numbers of fish and other species in nearby waters. Importantly, they can provide a buffer against uncertainty, including management errors. Permanent marine protected areas should be established in appropriate locations adjacent to all the U.S. coasts. It will be important to include highly productive areas—that is, areas in which fishing is good or once was—if this management approach is to produce the greatest benefits.
Protected areas will make the most effective contribution to the management of species and ecosystems when they are integrated into management plans that cover the full life cycles and geographic ranges of the species involved. Smaller, fixed protected areas will be most effective for species with life stages that are spent in close association with fixed topography, such as reefs, banks, or canyons. For other species, the degree of effectiveness of protected areas will be related to the importance of fixed topography in various stages of their lives. Wholly or largely pelagic species move according to ocean currents or other factors that are not necessarily related to fixed topographic structures and are thus likely to benefit less from small protected areas.
The design and implementation of marine protected areas should involve fishers to ensure that they believe the resulting systems will protect their long-term interests and to improve operational integrity. Because attempts to develop marine protected areas in the United States have been strongly opposed by some fishers, the broad involvement of users is a key strategy. Current theory and
experience make clear that marine protected areas must be established over a significant portion of the fishing grounds to have significant benefits. Recent calls for protecting 20 percent of potential fishing areas provide a worthwhile reference point for future consideration, and emphasize the importance of greatly expanding the areas currently protected.
Marine protected areas are not alternatives to other techniques of fishery management and to the other recommendations in this report. They should be considered as only one of a suite of important ecosystem approaches to achieve sustainable fisheries and protect marine ecosystems. For marine protected areas to be most successful as fishery-management tools, their intended purposes must be clearly defined.
Bycatch and Discards
Bycatch and discards add to fishing mortality and should be considered as part of fishing activities rather than only as side effects. Estimates of bycatch should be incorporated into fishery-management plans and should be taken into account in setting fishing quotas and in understanding and managing fishing to protect ecosystems and nonfished ecosystem components. Reducing fishing intensity on target species can reduce bycatch, often with no long-term reduction in sustainable yield. In some cases, technological developments and careful selection of fishing gear (e.g., bycatch-reduction devices) can be effective in reducing bycatch, and those options should be encouraged, developed, and required where appropriate. More information is needed on discards and on bycatch and their fate (i.e., whether bycatch is retained or discarded and whether discards survive or die).
Effective fishery management requires structures that incorporate diverse views without being compromised by endless negotiations or conflicts of interest. The committee recommends developing institutional structures that promote
- effective and equitable reduction of excess capacity,
- sustainable catches of targeted species,
- expansion of the focus of fishery management to include all sources of environmental degradation that affect fisheries,
- consideration of the effects of fishing on ecosystems,
- development and implementation of effective monitoring and enforcement, and
- the collection and exchange of vital data.
To achieve these goals, the spatial and temporal scales at which the institutional
structures operate should better match those of important processes that affect fisheries. Participation in management should be extended to all parties with significant interests in marine ecosystems that contain exploited marine organisms. Institutions should allocate shares in or rights to fisheries, rather than allowing openly competitive allocations. The clear explication of management goals and objectives is a prerequisite to achieving effective and equitable management.
Better understanding is needed of the structure and functioning of marine ecosystems, including the role of habitat and the factors affecting stability and resilience. This includes attempting to understand mechanisms at lower levels of organization (i.e., populations and communities), long-term research and monitoring programs, development of models that incorporate unobserved fishing mortality and environmental variability (e.g., El Niño events) into fishery models, multispecies models, and trophic models. More research is also needed on the biological effects of fishing, such as the alteration of gene pools and population structures as a consequence of fishing. More research is needed on the conditions under which marine protected areas are most effective, and marine protected areas themselves should be used as research tools as well as for conservation.
More information is needed on the effects and effectiveness of various forms of rights-based management approaches and other management regimes, on the way people behave in response to different economic and social incentives, and on barriers to cooperation and sharing of information. The committee recommends research into the roles of communities in fisheries management, including the use of community-based quotas and other assignments of rights to communities, and explorations into the feasibility of granting management responsibilities to those engaged in a particular fishery, regardless of their geographical community ("virtual communities").
The need for more information should not be used as an excuse for inaction; that excuse has contributed significantly to current problems. Enough is known to begin taking action now.