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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options 3 Considering the Management Implications From a policy perspective, the ecosystem-level effects of fishing are of concern for two reasons: (1) the risk to overall long-term productivity of important commodities (i.e., harvested species) that can be obtained from the system, and (2) the need to maintain other ecosystem services in addition to these commodities. Maintaining productivity of commercially valuable species is linked to maintaining a functioning ecosystem that provides a range of additional services. These include climate regulating services and disease control, supporting services such as primary and secondary production, and cultural or aesthetic services (Millennium Assessment 2003). As the principal fisheries statute in the United States, the Sustainable Fisheries Act (P.L. 104-297) (adopted by Congress in 1996 as an amendment to the Magnuson-Stevens Fisheries Conservation and Management Act [MSFCMA] [P.L. 94-265]) includes a mandate to “protect the marine ecosystem,” acknowledging the importance of ecosystem components and services beyond just fishery yields. To move beyond managing for individual fishery yields, policies must be developed to fit within a framework of ecosystem-based management—considering the fishing effects of food-web interactions, bycatch, and habitat. Because all organisms are linked within a system, management strategies will have to make explicit tradeoffs among fished stocks, whether it is setting harvest rates, rebuilding strategies, or promoting other uses. A few examples of the management implications of trophic interactions and food-web effects, possible genetic changes, and physically induced regime shifts are provided here. The importance of developing multi-species harvesting strategies is considered, as well as some of the management structures that could be used to implement techniques to account for
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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options the ecosystem effects discussed in Chapter 2. This chapter focuses primarily on tradeoffs within and between fisheries; however, a larger suite of issues must be examined when considering tradeoffs in an ecosystem context. These issues are addressed in Chapter 4. FISHERIES MANAGEMENT IMPLICATIONS OF ECOSYSTEM INTERACTIONS The consideration of multi-species interactions requires making decisions that involve explicit allocation tradeoffs both between food-web components and between user groups. In choosing harvest strategies in a multi-species system, it is impossible to avoid making de facto distribution decisions. Making these kinds of tradeoffs goes well beyond just deciding allowable catches for target species; bycatch must also be considered in most fisheries. Tradeoffs must also be made among fisheries, other commercial uses, and nonconsumptive uses of marine resources. These decisions are not scientific but instead decide the allocation of resources, although science still has an important role to play in informing such decisions (discussed further in Chapter 4). Harvest strategies used in the United States involve the specification of biological reference points to determine target harvest rates as well as limits of fishing mortality and biomass that ought to be avoided. In this context, a natural first step is to determine how these harvest-rate targets and limits will be determined to account for species interactions. Should lower harvest targets be used for forage fish to protect the productivity of top predators? Should rebuilding targets be set taking into account that reestablishing depleted predator populations may impact fisheries that harvest their prey? Biological reference points depend upon life-history parameters, perhaps most significantly predation mortality (Collie and Gislason 2001). The effects of interactions can only be ignored if buffering mechanisms (e.g., predators switch between alternative food sources and prey have limited vulnerability to their predators) keep natural mortality rates from varying in response to changes in trophic structure. This chapter presents examples of different fisheries scenarios and associated management implications that come into play when accounting for the food-web effects of fishing in marine ecosystems. These examples are simplified. They are intended only to highlight considerations that managers will begin to face as ecosystem interactions are incorporated into fisheries management and tradeoffs are explicitly made among species and users. Fishing a Single Trophic Level The management implications of accounting for ecosystem effects of fishing vary depending upon the nature of the fisheries in question. The simplest setting (uncommon in practice) would be one in which fisheries only target the top
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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options trophic level. The major management concern would be to prevent the overexploitation of the top predator, accounting for any detrimental consequences of cascading effects to lower trophic levels. To achieve this, a modified single-species approach could be applied. In theory, an initial harvest rate would be selected that would sustain the population and prevent overfishing. This harvest rate would then need to be adjusted to account for the targeted species’ role as a predator in the system. A harvest reduction may be necessary to diminish cascading effects via alternating increases and decreases of abundance for species down the food web. The magnitude of these adjustments would rely on knowledge of predator-prey interactions through the food web, the strength of these interactions, and appropriate food-web models to represent the dynamics. Another single-species scenario (again uncommon in practice) occurs when a fishery targets a single intermediate trophic level. Similar concerns would exist for managers, but cascading effects would have to be evaluated both to lower and higher trophic levels. Setting a harvest target for these fisheries would have to incorporate information about the target’s predators and prey, but in a bidirectional structure. If the population of the target species is reduced, then its predators would either consume less or would switch to preying on other species. These changes might be difficult to predict and hence generate unexpected results. For example, when great whales were hunted to low abundance in the North Pacific, it is hypothesized that orcas (the top predator in the system) switched from feeding on the whales to other marine mammals (Estes et al. 1998). As discussed in Box 2.2, orca predator switching may be the cause of a new trophic cascade that had effects on the entire ecosystem. Setting the harvesting strategy for such a connected system would require the total allowable harvest to be divided between humans and the predators of the target species with total takes low enough that the population of the target species does not collapse. While these principles are straightforward in the abstract, in practice setting “single-species” harvest targets that take these ecosystem effects into account will be complex. As species abundances change, their interactions and the strength of these interactions will change as well. By necessity, the management process will need to be a flexible one that includes a monitoring scheme to provide feedback about the system status and an implementation strategy capable of responding to this feedback (Sainsbury et al. 2000). An iterative process would allow for the continuous monitoring and assessment of conditions and the incorporation of new knowledge about complex food-web interactions. Fishing Predator and Prey A more common management scenario is one in which managers must set harvest regulations for multiple species that are harvested by different groups and that have direct predator-prey relationships. In this scenario, setting harvest targets
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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options for the species or complex caught by one group of fishermen will affect the potential yield of species targeted by other fishermen. Thus, managing for ecosystem effects will inevitably be more politically controversial because adjustments made to account for these effects will have allocation consequences to users. As an example, consider the strong predator-prey relationship between cod and capelin where each species is caught by different groups. Here, the desire to incorporate ecological interactions in decisions would need to involve explicitly acknowledged tradeoffs between user groups. For example, allowing more cod biomass for cod stock safety would require a reduction in allowable harvest for capelin over and above the reductions needed for capelin stock safety. Or, from the other perspective, constituents for the cod fishery would lobby for strong stock safety margins for capelin stocks, because that would allow greater sustainable harvests of cod. Capelin constituents would argue the opposite position, desiring higher catches of capelin. Similarly, recognizing species interactions for rebuilding plans introduces an extra layer of explicit tradeoffs. If a cod collapse has allowed increases of another species, then a cod recovery plan will be seen as imposing costs on constituents targeting the newly abundant species. For example, accounting for interaction between cod and lobster in the East Coast system inevitably means that lobster constituents will see losses associated with cod rebuilding, namely the long-term reduction in lobster. In a single-species world, the main tasks of reaching consensus revolve around convincing a specific fishery to take actions that are in its long-term interest, perhaps with short-term costs. But in a multi-species world, tradeoffs will have to be made, giving more yield to one fishery at the expense of another as a consequence of accounting for species interconnections. Fishing Multiple Trophic Levels Managing fisheries that target multiple levels of the food web presents a more complex challenge than fishing one pair of predator and prey species. Adding lower trophic levels to the catch means that both predators and groups of prey are targeted. For example, in the Pacific Ocean, longline fishing reduced the abundance of the very largest predators; purse seines were then added to the fishery and caught a wider range of sizes, some of them juveniles of the apex predators and some the prey of the apex predators. In the multiple-trophic-level scenario, the reduction in the largest predators would reduce predation pressure, and therefore mortality rates, on the smaller fish. This would result in increased abundance of the smaller species or higher survival of juveniles, such that greater catches may be sustained than if the apex predators were not being fished. Fishing both groups could allow sustainable catches of apex predators while lower trophic levels are added to the catches. At the same time, negative effects on system
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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options biodiversity might be reduced because the fisheries are not merely cropping off the top predators through serial depletion. Overall, determining sustainable exploitation rates becomes a complex exercise in weighing tradeoffs in the catches from different trophic levels. As discussed previously, exploitation of lower trophic levels creates competition between humans and apex predators for a common prey, but one in which the reduction in apex predators may allow greater catches of the prey species by the fishery than if only the prey species were harvested. But, reductions in fishing pressure on some of the larger predators would increase predation on the lower trophic levels and would require a reduction in fishing effort on these components of the food web. Again, a complex of policy conflicts and tradeoffs would arise from simultaneously harvesting apex predators and their forage base. Management approaches for fishing several interacting trophic levels at the same time would need to be designed to account for impacts of fishing on the interacting system. The fishery literature has made explorations into fishing both predator and prey (Cox et al. 2002a, 2002b; Essington 2004; Essington and Hansson 2004; Hinke et al. 2004), but management protocols for dealing with this level of complexity are not in place. MANAGEMENT IMPLICATIONS ASIDE FROM TROPHIC INTERACTIONS AND TRADEOFFS Some of the impacts to marine ecosystems discussed in Chapter 2 are not directly related to predator-prey interactions as presented in the previous examples. However, these impacts are equally important. They affect stock and ecosystem productivity and may ultimately result in lower or higher yields and must be managed accordingly. Preventing Genetic Changes Recent evidence suggests that size-selective fisheries can alter life histories of marine fishes both phenotypically (Berkeley et al. 2004) and genetically (Conover and Munch 2002, Heino et al. 2002, Law and Stokes 2005). Even nonselective fisheries can reduce the reproductive lifespan of fishes that spawn over a number of years, thereby reducing their evolved buffer against uncertainty in larval survival (Heppell et al. 2005). Fisheries based on a given species that target the largest fishes will tend to take the most rapidly growing fishes, resulting in selective pressure against fast growth. This may affect the genetic capacity for growth and ultimately production. In addition, recent studies with long-lived Pacific rockfishes have demonstrated that older females, in better physiological condition, produce larvae that are far more likely to survive than those produced by younger females (Berkeley et al.
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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options 2004). If the larvae of older females are important to producing robust year-classes, it may be especially important to maintain the older age groups in the population. One approach to maintaining age structure would be to target the intermediate-sized fishes and not the largest fishes as is done currently. This could be accomplished using a slot limit where small fish are avoided or released to prevent growth overfishing and large fish are avoided or released to protect the most fecund spawners. However, slot limits can only work where gear or fishing methods are able to catch different sizes of fish (e.g., with hook size regulations) and where discard mortality is insignificant. But solely changing the sizes targeted would not be enough to increase abundances of older age groups; a reduction in mortality is still needed. In the case of Pacific rockfishes (Sebastes spp.) and other deep reef fishes (Coleman et al. 1999), slot limits seem unlikely to work. Another possibility is to protect whole communities by implementing marine reserves. For species with demonstrated maternal effects where maintenance of an unexploited age structure is critical, marine reserves may be the most reasonable alternative. Even for species that are moving in and out of the reserve area, protection of areas where the catchability of large fish is high will be beneficial. Further, in the case of highly migratory marine animals including fishes, it may be possible to provide protection using marine protected areas with moving boundaries (Hyrenbach et al. 2000, Norse et al. 2005). If fish, seabirds, marine mammals, or sea turtles, for example, migrate along specific pathways, it might be possible to reduce overall mortality by protecting them when they are passing through or aggregating in a particular area. Satellite telemetry coupled with new techniques in marine spatial analysis can provide models for these movements that link to oceanographic variables. Fish such as Atlantic cod have also displayed much greater complexity in spatial success of reproduction than the continuous stock assumption would predict (Hutchings 2000, Hutchings and Reynolds 2004). This suggests that the location of fishing effort needs to be managed in conjunction with the total amount of effort to reduce genetic impacts. Spatially distributed fish stocks may be genetically distinct; in this situation, serial depletion of stocks not only reduces overall stock size, but also reduces the genetic diversity of the overall population by potentially eliminating locally adapted subpopulations. This process is well documented for Pacific salmon (NRC 1996b). Subpopulations have suites of adaptations that increase their fitness for the particular spawning location to which they home. When the fishery captures fishes from low productivity and high productivity subpopulations that mix on the fishing grounds, substantial depletion and extinction of the so-called “weak” stocks are probable. This is a serious problem with migratory anadromous fishes like Pacific salmon.
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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options Responding to Regime Shifts Two different forces can induce a shift in the marine ecosystem. The first is by fishing pressure alone. A fisheries-induced regime shift drives the system into an alternative state with different relative abundances and a different structure than the previous system. The degree to which the ecosystem services provided under the new state will be inferior to the old one is largely uncertain. However, the shift may be irreversible and therefore a precautionary approach would prescribe taking measures to avoid fishing at high harvest rates capable of inducing a regime shift. The second cause of regime shifts are large-scale climatic drivers such as the Pacific Decadal Oscillation or the North Atlantic Oscillation, which cannot be avoided. Fishery management implications arise because fishing may amplify the effects of climate changes. How should managers anticipate and adjust fishing pressure during a climatically driven shift, especially a shift from high to low productivity? In periods of high productivity, the fishery would be expected to expand, and it should do so if managers choose to take advantage of the high production. During a shift to a period of low productivity, fishing effort would need to be reduced so that fished populations and communities were not depressed to unsustainable levels or to levels that would prevent or impede recovery when the climatic shift returned to more favorable conditions. But scientists and managers can only reasonably predict some climatic shifts, such as the Pacific Decadal Oscillation. Thus, unavoidable lags in fishery management responses for unforeseen shifts will potentially exacerbate ecosystem-level effects and thereby make the ecosystem even less productive. Such lags would be especially problematic if the ecological responses to physical changes are nonlinear and rapid as suggested in the analyses by Hsieh et al. (2005). Polovina (2005) provides a summary of studies that have examined the issue of what constitutes optimum management strategies for fisheries that undergo regime shifts. Most of these studies use models to simulate low-frequency variation in survival and carrying capacity to represent climate-induced regime shifts (Walters and Parma 1996, Spencer 1997, DiNardo and Wetherall 1999, Peterman et al. 2000, MacCall 2002). Two different strategies emerge from these simulations. The first, which performed well under some circumstances, employs constant harvest rates set irrespective of environmental regimes (Parma 1990, Walters and Parma 1996, DiNardo and Wetherall 1999). In other simulations representing different types of systems, results favor a regime-specific harvest rate strategy over a constant harvest rate strategy (Spencer 1997, Peterman et al. 2000, MacCall 2002). To a large extent, adjusting harvest rates in response to changing environmental conditions will depend on the frequency of regime shifts relative to the life span of the target species. The benefits of regime-specific strategies will increase when the magnitude of potential change in productivity is large and when climate regimes persist for longer time periods.
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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options DEVELOPING MULTIPLE STOCK HARVEST STRATEGIES In principle, the maximum sustainable yield (MSY) concept1 and related management targets and strategies can be extended to multiple stocks as a basis for policy, although setting multiple species harvest targets is an inherently more complicated task, as indicated in the previous examples. The important conceptual point is that if species are linked through trophic, food-web, and habitat interactions, accounting for those linkages inevitably means considering harvesting strategies for all species simultaneously, in a manner that recognizes the interconnections. This in turn means that multi-species harvest strategies for any species cannot be determined independently of those for other linked species. This presents important scientific questions as well as questions relating to what the systemwide objectives should be. Multi-species harvest targets can be established only if the goals for the systems are specified. One possible management option is to use the multi-species analogue of the single-species MSY concept. Under this objective, harvest targets or reference points that achieve the system-wide sum of sustainable physical yield could be computed (at least in principle). The suite of harvest targets that maximize the sum of systemwide yield would differ from their single-species analogues in ways that depended upon trophic interactions (e.g., Beddington and May 1977, May et al. 1979). Another possible management objective might be to maximize the systemwide value-weighted sum of sustainable yields. Again, both trophic interactions and relative economic values of each species would interact in ways that determine the suite of multi-species reference points. Christensen and Walters (2004) show that maximizing value-weighted sustainable yield generally implies larger systemwide biomass levels than maximizing unweighted yields. They also show that the ecosystem configuration that maximizes a systemwide objective is not necessarily similar to what would emerge by maximizing independent species-specific target yields. A comprehensively conducted multi-species analysis of harvest targets and reference limits could also, in principle, account for nonconsumptive uses. This could be done, for example, by incorporating information on the manner in which nonconsumptive services depend upon biomass size and characteristics. Species with high values for nonconsumptive services would compete with consumptive values in a comprehensive analysis, in some cases implying maintenance of high biomass levels and low (or zero) harvests. At present, these kinds of simulations are difficult to do because while a great deal is known about economic values associated with consumptive uses like fishing, comparatively little is known 1 The maximum sustainable yield (MSY) concept is the concept that there is a maximum average catch or yield that can continuously be harvested from a stock under existing environmental conditions without affecting significantly the reproduction process of that stock. See Appendix D for a glossary.
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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options about nonconsumptive values. Methods that can account for all these tradeoffs—consumptive uses, nonconsumptive uses, and ecosystem services—are available, but are in their infancy. The Role of MSY in Multi-Species Management The policy guidelines available for managing single stocks of fish are quite well specified. The MSFCMA (P.L. 94-265) states that Congress finds, “Fisheries resources are finite but renewable. If placed under sound management before overfishing has caused irreversible effects, the fisheries can be conserved and maintained so as to provide optimum yields on a continuing basis.” Furthermore, Congress stated, the term “optimum,” with respect to the optimum yield from a fishery, means the amount of fish which: will provide the greatest overall benefit to the Nation, particularly with respect to food production and recreational opportunities, and taking into account the protection of marine ecosystems; is prescribed as such on the basis of the maximum sustainable yield (MSY) from the fishery, as reduced by any relevant economic, social and ecological factor; and in the case of an overfished fishery, provides for rebuilding to a level consistent with producing the maximum sustainable yield in such fishery. The concept of sustainable yield results from the intrinsic ability of biological populations to compensate for increasing fishing pressure by increasing their productivity. Density-dependent compensation results in some surplus production that can be harvested on a continuing or sustainable basis. As a conceptual framework this is a straightforward proposition. However, managing by species-focused MSY on targeted stocks does not take into account the food-web interactions discussed previously. So even if only a single stock is being managed, the harvest level must be set with these considerations in mind. In addition, in multi-species fisheries with bycatch of noncommercial stocks, ignoring bycatch might result in unacceptable depletion of species that are important for ecosystem health. Single-species-focused MSY management also neglects possible habitat damage. Yet it is important to note that current management measures have begun to incorporate these larger effects and have succeeded in reducing bycatch and protecting habitat. Nonfishery concerns must be addressed as well. The opportunity cost associated with other ecosystem services increases with higher levels of biomass and other characteristics closer to pristine states. Additionally, when cascading effects are caused by the fisheries, even maintaining harvest rates at the single-species MSY level could mean that developing other uses is precluded. For example, if the abundance of a forage fish species is important to maintaining other eco-
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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options system components, maximizing fishery yield neglects consideration of the role of that forage species in sustaining the dependent species and the ecosystem. These types of considerations are explored in the literature from both theoretical (e.g., Beddington and May 1977, May et al. 1979, Clark 1985) and applied perspectives (e.g., Collie et al. 2003, Walters et al. 2005). Indications are that single-species MSY policies may set harvest rates too high when ecosystem interactions occur, especially when the target species are prey to other species whose productivity is to be preserved. For example, Walters et al. (2005) examine the performance of single-species harvest rate policies for 11 model ecosystems representing a wide range of different systems. They demonstrate that widespread application of single-species MSY fishing mortality rates (FMSY) would in general cause severe deterioration in ecosystem structure, in particular the loss of top predator species. However, in their study FMSY was applied to all species in the ecosystem, including forage fish that have been only lightly fished in the past and that would provide alternative food sources to top predators when some of their prey are fished. For most of the ecosystem models, they conclude that “(1) yields under a many-species FMSY policy can diverge grossly from single-species predictions, and (2) the direction of divergence is not consistently related to trophic level” (Walters et al. 2005, p. 566). Better performance overall occurred when they simulated a more precautionary harvest rate policy in which the fishing mortality rate was set to 70 percent of the single-species FMSY. However, this is only one example and clearly more such studies are needed to advise management regarding what deviations from single-species MSY would be necessary to maintain ecosystem integrity. The following section lays out a framework for evaluating fisheries management strategies in an ecosystem context, but, in the short-term and for systems where this framework cannot be implemented, a precautionary approach (e.g., Restrepo et al. 1999; FAO 1996) should be applied, choosing some percentage of the MSY as the target harvest rate, as in the Walters et al. (2005) study. Considering that historically many fisheries have substantially and repeatedly exceeded the harvest rate that would ostensibly produce MSY, a margin of safety for application of MSY estimates is appropriate. At the very least, when MSY-based rules are applied in systems without accounting for species interactions, using FMSY as a limit reference point instead of as a target could be an essential step in guarding against future overfishing (Mace 2001). Such an approach is called for in the United Nations Treaty on Highly Migratory and Straddling Fish Stocks (United Nations [UN] 1995). But, it is essential to note that regions with harvesting strategies that were designed using model-based scenario analysis (as described in Chapter 4) would tend not to support using a fixed percentage of FMSY for all species as the preferred management action. In some cases, it may be deemed necessary to exceed FMSY to achieve larger, ecosystemwide goals. But such approaches will require sufficient data about the system to reasonably evaluate potential outcomes.
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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options MECHANISMS FOR IMPLEMENTING MULTI-SPECIES HARVESTING STRATEGIES The model-based scenario approach discussed in Chapter 4 is the essential step for evaluating alternative fishing strategies that can address ecosystem concerns. However, it is first necessary to discuss some of the regulatory schemes that can be used to manage fisheries since these differing approaches will need to be tested in model simulations and weighed as potential options when deciding tradeoffs, both between competing fisheries and between fisheries and other uses. Ecosystem and food-web considerations might be accounted for in fishery management by various mechanisms. Fisheries are primarily managed by direct or indirect controls on either inputs (e.g., effort, gear type and configuration, and time and area closures or openings) or outputs (e.g., catch in weight or numbers, limitations on landing certain sizes or species of fish, and limitations on bycatch amounts). Direct controls regulate the input explicitly; for example, a limited-entry program fixes the number of vessels, or season-length restrictions close the fishery upon attaining targeted catch or landings. Indirect controls are intended to limit inputs or outputs by constraining other features of the fishery, such as gear restrictions that affect the efficiency of fishing or area closures that prohibit fishing (Box 3.1). For all of these management tactics, ecosystem considerations could, in principle, be included in the determination of harvest strategies that address a broader set of impacts and conserve ecosystem structure and function. Most fisheries management in the United States and internationally relies on output controls with catch quotas as a primary regulatory objective, accomplished by some input controls on gear, areas, and seasons. From an ecosystem perspective, addressing the manner in which input controls are chosen and used may be more important than the choice of output controls. This is because ecosystem effects often result from the specifics of how fishing effort is exerted, rather than the absolute level of removal of target species. Habitat impacts and bycatch, for example, result from the level and type of fishing effort, regardless of how much is landed. In effect, this means that fine-tuning fishing effort configurations is a critical mechanism for managing ecosystem effects. Output goals are some measure of the performance of input controls in this sense. If the fishing capacity, fishing time, gear, and areas allowed are properly set, then the output control, such as the amount landed, should serve only as a backstop against overfishing rather than as the primary control mechanism. In the next section, two conceptual alternatives are discussed for managing inputs and outputs in fisheries, namely top-down and bottom-up structures. Institutional Structures and the Regulation of Fishing Effort Fishing effort can be managed for either single- or multiple-species objectives with two different institutional structures. By far the most common method
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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options BOX 3.1 The Use of Marine Protected Areas One possible approach to address ecosystem concerns is the use of protected or reserved areas (NRC 1999a, 2001). The major benefit of “no-take” areas is the ability to protect both target stocks and bycatch species from harvest in cases where species have low mobility relative to the size of the reserve. The habitat needed for commensurate species is also protected, presuming the requisite enforcement occurs. Well-designed closed areas or marine protected areas can be important buffers against uncertainty in controlling fishery harvest rates (Stefansson and Rosenberg 2005). They can also protect against genetic changes in intense size-selective fisheries and in long-lived species with demonstrated maternal effects (Heino et al. 2002, Berkeley et al. 2004). Their benefits, however, will depend on sound management outside of the reserves to maintain fishing effort within ecologically sustainable limits (Hilborn et al. 2004), thereby preventing the simple redirection of fishing effort from one area to another. The use of reserves and protected areas, or of networks of reserves, is not a panacea, but it is one consideration—within a suite of management options—for mitigating ecosystem-level impacts of fishing, especially in areas that have been severely degraded. On an experimental level, strict “no-take” areas would be the only way to eliminate fishing pressure, if only for a set amount of time, to observe whether stock and ecosystem recovery is possible. If set aside for a long enough time, a marine reserve of the correct size could assist in resolving issues with shifting baselines, allowing scientists and managers to quantify how much the surrounding area has changed due to fishing. utilized in both the United States and internationally is what is known as top-down control, meaning centralized determination and enforcement of total output via input controls, and an absence of secure individual-access privileges. Under top-down control systems, harvest target goals or limit points are set, and then input controls are chosen and implemented by some management body to achieve these goals. In U.S. fisheries, these output and input control decisions are vested mostly in the Regional Fishery Management Councils. A commonly used procedure is to set harvest targets or limits within a backdrop of MSY concepts, and then use seasonal closures once accumulated harvest reaches the target. Additional measures are also commonly added onto basic total effort controls on commercial fishermen to address a range of noncommercial fishery goals, including protecting species from excessive bycatch, incorporating mammal and bird protection regulations, and allowing other user services in addition to commercial fishing. For example, bycatch may be regulated by gear restrictions (e.g., requiring turtle excluder devices) or by closing the season for a target if a bycatch limit is reached.
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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options In principle, existing top-down regulatory procedures can be adapted to account for ecosystem effects in a more explicit and less ad hoc fashion. This would involve two steps. The first would require the specification of a new set of systemwide harvest targets that account for trophic interactions as well as rules that limit ecosystem impacts such as habitat loss and loss of biodiversity. The second step would be to determine a new suite of regulatory actions to limit effort according to the modified harvest rules. With top-down regulations, Councils set harvest objectives and targets and then determine constraints on individual fishermen’s decisions to attain the objectives. All fishermen and other user groups can play an indirect role in setting harvest rules by lobbying the Councils, but ultimately the final decisions are left to the top-most layers in the system, namely the Council membership and the Secretary of Commerce. Therefore the tradeoffs between fishing groups are made overtly by managers or by a process determined by the political system. Top-down approaches have been effective in reducing or preventing overfishing in many fisheries, although in other cases they have failed to effectively constrain effort and avoid overexploitation. The most important drawback of top-down governance institutions is that they maintain an adversarial relationship between regulators and regulatees. That is, fishermen are seen by regulators as needing control and restraint, and hence their access to the resource is left tenuous and uncertain, and tightly controlled by regulations. By leaving resource access insecure, this system generates perverse individual incentives to increase fishing capacity, which must, in turn, be met by further imposition of controls by regulators. Top-down systems with insecure access privileges thus generate a “race to fish” which, if it does not actually subvert the intended control over the resource, nevertheless generates continual increases in capacity and economic waste. In most fisheries, the race to fish continues as long as growing markets keep increasing prices, leading to shorter and shorter seasons, unevenly applied effort, poor quality product, and wasteful investment in distorted fishing gear and capital, all wrapped up in an adversarial process between regulators and fishermen. From an ecosystem perspective, recreational and commercial fishermen have little incentive in a top-down system to limit their ecosystem-level impacts other than through altruism. Because the race is on, ecosystem impacts take a back seat to the fundamental uncertainty in the process, which is securing a share of the harvest target before one’s competitors do. In the race-to-fish setting, a spiral is then set into motion, with managers tasked to create ever more complex regulations to try to reduce the fishing effort. An alternative to the top-down approach is to implement so called bottom-up management systems with secure access privileges. Bottom-up approaches still require that harvest rules be set in some fashion, but they eliminate the need to micromanage the details of effort and input decisions with regulations. The key to this alternative system is the creation and allocation of harvest-access privileges that eliminate the race-to-fish incentives that exist under top-down management.
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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options In decentralized, bottom-up regulation, fishermen have secure access privileges to a fraction of the total allowable catch for each species. These may be individually denominated privileges, as with individual transferable quotas (ITQs, see NRC 1999b), or they may be group allocated privileges, such as to a harvester cooperative or a community. A few such systems exist in the United States in Alaska, and both domestic and international examples have resulted in important changes to fishermen’s behaviors. Perhaps the most important lesson from the adoption of these systems is that, with secure access privileges, the incentives generated for individuals are radically different from those under top-down command and control with insecure access. With secure access privileges, whether granted to an individual or group, fishermen no longer need to race to fish because their allocation guarantees them access. In this environment, behavior switches dramatically from catch maximizing to value maximizing. Fishing is slower, fishing capital is (generally) downsized, redundant inputs are eliminated, and new innovations in the market are stimulated to increase value of harvest. On the cost side, these systems may require more enforcement and monitoring to prevent dumping (e.g., discarding of a portion of the catch to stay within allocations), information fouling (e.g., falsifying records such that the allocation is undermined), and cheating (e.g., landings outside of the allocation, illegal transfers to other allocation holders), and they always involve contentious initial allocation decisions regarding who is granted privileges and how much allocation is granted. In bottom-up systems with secure access privileges, the tactical decisions are left to the fishermen about how to conduct their fishing operations to maximize the value of their allocations. While these systems have generated important positive impacts on commercially targeted species, they do not address all important ecosystem impacts of fishing. However, it is possible to modify the basic structure of the systems where access privileges are predicated on ensuring that impacts to other ecosystem components are minimized. Bottom-up governance systems may also promote the development of fishing methods that more efficiently reduce ecosystem level effects. For example, if limiting noncommercially valuable bycatch is deemed necessary, allocation privileges for the target species can be extended so that fishermen also have allocations of bycatch determined using multi-species approaches to set reference points. In other words, managers could set limits on acceptable levels of noncommercial bycatch, allocate these as bycatch harvest privileges to individual fishermen (or groups), and allow fishermen to best choose methods to avoid using their allocations. While enforcement and accurate reporting remain an issue and are generally more costly under access privilege systems, there are important advantages to this system compared with conventional top-down systems. For example, a multi-species fishery might be closed by regulators when some reference level for bycatch is reached. Under a bottom-up system with bycatch allocations, fishermen “use up” their bycatch allocations as the level of bycatch deemed acceptable for ecosystem services is approached. Furthermore, if a bycatch allo-
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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options cation can be traded among fishermen, they take on their own market value during the season. Fishermen can then either use or sell their allocations in a tradable system; every ton of bycatch avoided presents an opportunity to sell a ton. This creates an automatic and continuing incentive to adjust fishing behavior to avoid bycatch. The same notion of trading and accumulating harvest privileges could be used to account for nonconsumptive services associated either with components of a system or even particular areas of marine ecosystems. But sustaining these decentralized incentive effects is not easy; enforcement and monitoring are important components of maintaining such a system since the incentives to cheat and underreport bycatch are similar to those in a system with directed-catch allocations. An additional important effect of designating harvest-access privileges is that the privileges become securities, in the same sense that holding a share of stock promises access to a flow of future dividends. The importance of securing access privileges is that they generate a stewardship ethic that motivates concern about the long-term health and productivity of the system, and the privilege can and should be coupled with responsibilities for stewardship in order to maintain that access. Individual transferable quotas and membership values for co-ops thus take on values that are similar to farmers’ land values. And with embedded values, owners are compelled to become stewards with long-term interests that preserve the values as well as the access if the privilege is tied to specific management needs (e.g., bycatch reduction, accurate reporting). Because of this embedded value, there is an additional incentive to make decisions that increase long-term values. This presents both opportunities and challenges for dealing with multi-species interactions in decentralized systems. Furthermore, fishermen may be compelled to seek out quota rearrangements with other fishermen to optimize the value of their holdings. And “other fishermen” may include those with whom a particular group of rights holders interact via the interrelated nature of their target species. For example, in the earlier cod–capelin example, cod fishermen might find it desirable to purchase harvest access privileges held by capelin fishermen to account for the predator-prey ecosystem effects of having a larger biomass of capelin to support the cod. Thus the difficult political decisions that we described as being required to manage multi-species systems might be allowed to occur spontaneously under some circumstances. The implications of bottom-up, access privilege-based systems are only just beginning to be understood as new examples are implemented in the United States and around the world. Hundreds of species are managed with these kinds of systems, which range from individual transferable (and nontransferable) systems to harvester cooperatives, regional-area-based cooperatives, and territorial-use right systems. The pros and cons of these have been debated for the past three decades; numerous summaries exist (see NRC 1999b). We will likely see more and not fewer of these institutions being adopted in the future. But, at this point, these discussions are simply illustrative of the possible consequences of using
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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options bottom-up approaches to achieve multi-species ecosystem objectives. Much more needs to be discussed and more research conducted on these issues. The questions that arise relate to whether decentralized and voluntary reallocations ought to be allowed or encouraged to achieve ecosystem-based fisheries management and, if so, what rules and institutions might facilitate them. OVERCOMING REGULATORY CONSTRAINTS TO SETTING MULTI-SPECIES REFERENCE POINTS An overarching framework does not exist within the current U.S. management system that explicitly addresses ecosystem management of marine systems across the various sectors of human activity. Institutionally, management is organized largely with respect to sectors of human activity: fishing, coastal development, water quality, and so forth. Even with area-based authorities such as the National Marine Sanctuaries, most of the regulation of specific activities, such as fishing, is left to specialized agencies. This system is not conducive to determining goals and tradeoffs between sectors and between users. Within multifunctional agencies such as the National Oceanic and Atmospheric Administration (NOAA) or the Environmental Protection Agency (EPA), little coordination exists between programs that manage activities affecting marine ecosystems (U.S. Commission on Ocean Policy 2004). In part, this lack of coordination stems from the statutory mandates currently in place. Individual agencies have mandated responsibilities that do not necessarily allow them to develop management actions that are more broadly based and coordinated across sectors of human activity. With respect to fisheries, while the MSFCMA calls for conservation of ecosystems on which fisheries depend, the national standards for management plans do not clearly call for coordination with other management actions outside the fishery sector. Nor is there a clear mandate in the national standards for managing the ecosystem effects of fishing, other than through consideration of fisheries habitat. Other existing laws, which require that management actions focus on certain single species, confound the issues. The Marine Mammal Protection Act (MMPA) and the Endangered Species Act (ESA) generally regulate activities on a species-by-species basis for species already in crisis. However laudable these efforts may be, they too tend to ignore the interaction and interdependence of marine ecosystems in favor of regulation on a species-specific basis. Such narrowly focused regulation can have unintended effects when cross-linked with fisheries and can make management decisions more difficult. Consider the potential conflict between restoring Pacific Northwest salmon populations and the predation on salmon by sea lions protected under the MMPA (NOAA 2002). Resolution may be even more difficult when both partners in a predator-prey interaction have some degree of federal protection. Sea otters are in precipitous decline in Alaskan waters, most likely due to increased predation by killer whales
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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options (Estes et al. 1998, 2005). Both are protected under the MMPA. In California, sea otters can control populations of commercially and recreationally valuable invertebrates (e.g., clams, sea urchins, and abalone) but also are a plausible threat to the severely endangered white abalone. Both otters and abalone are ESA listed. Slight attention has been paid to these regulatory dilemmas, which are certain to increase as management’s perspective embraces an increasing variety of linked species. As described in this chapter, consideration of ecosystem effects requires explicit consideration of tradeoffs in ecosystem services under different management actions. In effect, the current statutory structure precludes certain tradeoffs unless some overarching authority for ecosystem-based management is created. MAJOR FINDINGS AND CONCLUSIONS FOR CHAPTER 3 Managing fisheries within an ecosystem context will require accounting for food-web interactions and trophic effects and making tradeoffs between species or among fisheries and other uses. It is essential that tradeoffs be made among fisheries, other commercial uses, and nonconsumptive uses of marine resources since value and/or yield are unlikely to be maximized for all species. In an ecosystem context, the potential productivity or value of each resource depends on the management decisions made about other linked species. Accounting for species linkages will mean designing and implementing harvest strategies that recognize these interconnections. Single-species MSY policies are unlikely to be sufficient for future management because these measures do not take into account species interactions and food-web effects nor do they consider nonconsumptive ecosystem services. Preliminary evidence indicates that FMSY policies can set harvest rates too high when food-web interactions occur. However, whether single-species MSY harvest policies lead to harvest rates that are too high or too low will depend on the particular species, its trophic interactions, and, ultimately, on management goals, in particular how tradeoffs between competing uses are resolved. If the impacts of alternative harvest rates have not been examined using interaction models, implementing harvest rates at some fraction of single-species FMSY is likely the best protection against immediate overfishing. At the very least, FMSY should be implemented as a limit reference point and not a target. A variety of new regulatory mechanisms and institutions ought to be considered to help implement ecosystem-based management approaches. Successful accounting for ecosystem effects will require, at the first level, accounting for multi-species interactions. But it will also require mechanisms to deal with new and politically contentious allocation decisions within fisheries, and between fisheries and other nonconsumptive uses. Furthermore, there is a continuing need to consider governance structures that align fishermen’s incentives with long-
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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options term stewardship. Bottom-up, access privilege-based systems may hold enhanced promise to address some of the new issues raised by ecosystem considerations. Existing laws and agency structures will need to be examined against a wider mandate to implement an ecosystem approach to management. Several regulatory mandates and agency programs have been created specifically to protect certain species, and they are especially important for species in danger of extinction. However, such single-species-focused mandates and programs may result in conflicting goals in a multi-species or ecosystem approach to management. Dissolution of these single-species protections is not the answer; rather, management institutions must recognize that one protection may preclude the other. An overarching mandate that allows explicit consideration of tradeoffs is needed to resolve the difficulties of reconciling the existing mandates.
Representative terms from entire chapter: