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Page 126 7 Monitoring, Research, and Modeling ~ enlarge ~ Research and monitoring conducted in and around marine reserves and protected areas have three primary and interrelated benefits: (1) better understanding of reserves—how they should be designed and what their benefits and costs are in ecological and socioeconomic terms; (2) deeper knowledge of complex marine ecosystems and the ways that human activities affect these systems; and (3) development and application of marine management methods that are costeffective in achieving specific goals. Attempts to develop zoning plans for marine protected areas (MPAs) with marine reserves have revealed significant gaps in our understanding of marine ecosystems. Establishment of reserves will provide scientists with opportunities to close these gaps and develop more effective tools for marine conservation. MONITORING PROGRAMS Monitoring is an integral component of marine area management; it provides the data required to evaluate changes in marine ecosystems as a result of the implementation of MPAs, especially areas zoned as ecological or fishery reserves. These evaluations are essential for determining effectiveness, improving design, and providing progress reports to stakeholders. Monitoring refers to the periodic evaluation of specific attributes of the ecosystem(s) and socioeconomic conditions represented in or relevant to MPAs. Attributes to be included in a monitoring program will depend on the goals established for the MPA and
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Page 127the main stresses experienced by the ecosystem. Some of the questions that should be addressed through monitoring include the following: Does the MPA system meet its goals and why or why not? Are there unanticipated consequences? Are the size and location of reserves within the MPA optimal? Monitoring programs provide managers with crucial information for evaluating the current status of protected areas and the efficacy of conservation measures. For researchers, monitoring programs provide valuable data that are needed to identify trends in the health of living resources, trends that reveal fundamental features of how ecosystems function and help scientists distinguish between changes that are the result of human influences and those that are natural environmental fluctuations. Four categories of information may be included in a monitoring program: (1) structure of marine communities (abundance, age structure, species diversity, and spatial distribution); (2) habitat maintenance or recovery; (3) indicators of water quality or environmental degradation (e.g., pollutants, nutrient levels, siltation); and (4) socioeconomic attributes and impacts. For each category it is important that monitoring programs survey sites representative of the MPA, include replicated and comparable sites with different levels of protection, and employ standardized sampling techniques. General Considerations Temporal and Spatial Controls for Evaluating Marine Reserves There are two approaches to analyzing the impacts of marine reserves on living resources. In the first approach, changes within the reserve are evaluated temporally such that conditions are documented before the implementation of protections and then compared to conditions following implementation. A limitation of this approach is that environmental variation in the years before and after the establishment of the reserve may obscure trends resulting from protection. For instance, variable recruitment in a fishery due to a change in oceanic conditions may affect, either positively or negatively, the apparent recovery of a stock after closure of an area. In Kenyan reefs, a twofold increase in fish abundance was observed in surveys of both unprotected and protected sites (McClanahan, 1995); hence, the change was independent of the reserve. In the second approach, changes in the marine reserve are evaluated spatially such that conditions inside the reserve are compared to conditions in a similar area outside. The limitation of this approach is that reserves often encompass unique habitats; hence, there are few situations in which comparison areas accurately represent the features found within the reserve. For example, in the Polunin and Roberts (1993) study of marine reserves in the Caribbean, differences between fished and unfished areas could have been due to differences in habitat. The site chosen for the reserve might have had higher overall fish abundances even before fishing was halted.
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Page 128 Hence, to test conclusively whether reserves have a particular ecological effect relative to their original goals, it is necessary to establish monitoring regimes at multiple localities that include surveys before and after reserve establishment. Ideally, species survey methods should be rigorous enough to detect a 10-25% change in biomass, density, or species numbers. In many cases, however, such quantitative rigor is difficult to achieve. For example, in surveys of economically important snails on Kenyan reefs, McClanahan (1995) found that the population increases observed in reserves for seven of nine species of snail were statistically nonsignificant because of the overall low density of snails and high variation among sites. The Need for Systematics Monitoring species diversity requires knowledge of the systematics of marine species. Taxonomic expertise is necessary to identify the early life stages of various species to assess changes in recruitment success due to reserves. Although the taxonomy of most fish is well known, there are currently few scientists capable of identifying a large number of invertebrate and algal taxa in marine ecosystems. There are well-illustrated atlases for the larval forms of many temperate fish. However, similar resources are not available for the identification of fish larvae in other regions, specifically at low latitudes, or for the identification of fish eggs. Molecular tools to augment and perhaps automate the identification of species are being developed, but even these depend on a firm taxonomic foundation and require input from specialists. A matter of concern in this regard is the decline in the number of trained taxonomists, due to decreased institutional emphasis on systematics, as noted in a prior report (NRC, 1995). Structure of Marine Communities Many reserves in the United States and around the world have focused on enhancing or preserving commercially valuable species. Consequently, these populations have been the major or exclusive focus of monitoring (e.g., Davis, 1977; Russ and Alcala, 1989; Smith and Berkes, 1991; Keough et al. 1993; Attwood et al., 1997; Jennings and Polunin, 1997). In reserves designed to enhance biodiversity or stabilize populations of exploited or nonexploited species, monitoring programs have generally emphasized the distribution and abundance of species throughout a wide taxonomic range (e.g., Castilla and Durán, 1985; McClanahan, 1989; Cole et al., 1990; Castilla and Varas, 1998). Monitoring trophic status (e.g., mean trophic level) of aggregated macrofaunal biomass in the community can provide information on the state of community maturity and potential stability. Such ecosystem-wide monitoring has been instrumental in deciphering the dynamics of marine community interactions, with the result that critical linkages among trophic levels have been revealed.
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Page 129For example, studies on Kenyan reserves have shown that predatory fish control burrowing sea urchin abundance to such an extent that overfishing has led to an urchin explosion that threatens the physical integrity of reefs (McClanahan and Shafir, 1990). In New Zealand, such trophic interactions impacted even more of the food chain. Because fish are the major predators regulating the population of sea urchins, closing areas to fishing converted them from urchin-dominated algal “barrens” to kelp forest (Babcock et al., 1999). In the Las Cruces Reserve in Chile, protection of a strip of shore from collection of the predatory snail Concholepas not only increased the abundance of Concholepas, but also caused major changes in the community fauna and flora (Castilla and Durán, 1985). Similarly, strong ecological shifts may be occurring in other marine reserves, especially when the protected species contribute to or support biological habitat complexity associated with kelp, reef corals, or a variety of benthic invertebrates. However, understanding or even recognizing these changes requires broad monitoring of biological communities. Monitoring programs can detect changes in ecological processes that occur within reserves, in addition to differences in species compositions. Such monitoring may reveal a great deal about community structure and function. Studies in the Leigh Marine Reserve in New Zealand indicated that target fish species can act as keystone predators whose removal causes strong shifts from sea urchin barrens to kelp-dominated ecosystems (Babcock et al., 1999). More recently, the Florida Keys National Marine Sanctuary (FKNMS) has been the site of two studies of ecological processes inside and outside reserves. The first is a set of experiments monitoring the level of herbivory by reef fish where remarkable increases in herbivore pressure have been observed shortly after reserve establishment. The second study monitors recruitment of juvenile corals inside and outside reserves to understand the impact of ecological shifts on the potential of reefs to rebuild (FKNMS, 1999). These ecological studies—focused on important processes, not just species diversity—are crucial parts of a full understanding of reserve function. In the United States, most monitoring tracks economically important species, especially fish, with the result that ecological information about marine communities is sometimes scarce (Table 7-1). For example, an increase in biomass of fish in reserves may increase predation on invertebrates if they represent the main food source. An increase in predation on small species with quick generation times, such as epibenthic amphipods, may provide an early indicator of ecological effects in newly created reserves. However, such species are rarely monitored, so little is known about changes in abundance of taxa at lower trophic levels. However, it will be impractical to acquire full species lists and abundances for every marine reserve and protected area, especially because so many marine species are still undescribed (Grassle and Grassle, 1976; Grassle and Maciolek, 1992; Knowlton, 1993). Instead, it will be necessary to emphasize functional
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Page 130 TABLE 7-1 Monitoring Studies in Selected Marine Protected Areas Region Taxa Monitored Reference South Africa Fish Bennett and Attwood, 1991 Fiji Fish Jennings and Polunin, 1997 Spanish Mediterranean Fish Bayle-Sempere et al., 1994 Northwest Mediterranean Fish Bell, 1983 Philippines Fish Russ and Alcala, 1989 Northwest Mediterranean Fish Garcia-Rubies and Zabala, 1990 Florida Keys Fish Ault et al., 1998 New Zealand Fish, urchins, lobsters Cole et al., 1990 New Zealand Fish algae, urchins, lobsters Babcock et al., 1999 Kenyan Reefs Fish, urchins, algae, corals, snails McClanahan and Shafir, 1990 St. Lucia Urchins Smith and Berkes, 1991 Dry Tortugas Lobsters Davis, 1977 Lac Cruces, Chile Sessile invertebrates, algae, mobile invertebrates, plankton Castilla and Durán, 1985 Saba Fish, corals, gorgonians, sponges, habitat complexity Roberts, 1996 Belize Fish and habitat complexity Polunin and Roberts, 1993 Australian Intertidal Beaches Snails Keough et al., 1993 Florida Keys Corals, algae, lobster, fish, recruitment herbivory Florida Keys National Marine Sanctuary, 1999 Mafia Island, Tanzania Corals, fish, algae, environmental quality, habitat, human activities Agardy, 1997 groups of invertebrates and fish to gain wider coverage of the ecologically important components of ecosystems. For example, fish biodiversity tends to increase with greater habitat complexity. Consequently, monitoring in marine reserves should include documenting changes in structure-forming sessile organisms such as forest-forming algae; reef-forming colonial invertebrates; or bed-forming mussels, oysters, and clams (Roberts, 1995). Since many species vary in their habitatbuilding potential, such taxa should be cataloged at the species level. Primary Features of Fishery Monitoring Fishery reserves are planned and designed to improve management of particular species of fish. The intensity and temporal-spatial scales of the monitoring effort will be dictated by many factors, including the particular objective of the reserve, as well as logistical constraints imposed by reserve size, location, and availability of funds to support monitoring. A well-designed monitoring
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Page 131effort will help to ensure that the status of fisheries and associated resources is known and that the contribution of the fishery reserve is properly assessed (Carr and Raimondi, 1998). Ideally, fish stocks, habitat, key prey species, and the socioeconomic elements of a fishery will be assessed or monitored prior to reserve implementation to provide a proper baseline for comparison after the reserve is established. Thereafter, regular assessments and determination of stock status for fished species and possibly other key species must be conducted at least annually to determine status and trends within the boundaries of the reserve, but also at its edges and in regions adjacent to it. Many of the fishery-related variables will be the same as those used in conventional stock assessments (Pope, 1988; Shepherd, 1988) and can be used to monitor the status and trends of fish stocks (Fabrizio and Richards, 1996; NRC, 1998a) within reserves. It is essential to categorize adequately the species complex, abundance, size (used to determine biomass), and age structure of the fished components (fish and invertebrates) as part of the monitoring effort. To provide comparable statistics, fishery-independent data must be collected both within and adjacent to the reserve. Potentially, additional information on location, abundance, and age structure of fished stocks can be obtained from catch-per-unit-effort (CPUE) statistics. In addition to fished species, it is desirable to monitor their key prey and predators with respect to distribution, numbers, and size within the reserve and in adjoining regions. Proper design of the monitoring program is critical to ensure that trends in abundance are detectable. It may be sufficient to monitor relative abundances at age (or size), rather than actual abundances, although each program will have to judge its particular need. Estimating actual abundances and biomasses may be too expensive and, hence, unrealistic for many long-term, fishery-independent monitoring programs. A determination of spatial and temporal patterns in the distributions of target species is essential. For demersal species, associations with habitat features should be monitored, including shifts in utilization dependent on size and maturation. Propensities for shifts in habitat utilization or spatial distributions (e.g., depth zones occupied) at different life stages are important to evaluate. Monitoring programs that are temporally and spatially intensive may be required to measure emigration from reserves to surrounding regions or to determine if the reserve is acting as a source of recruits for fished areas. An important component of reserve monitoring programs should be the development of recruitment indices, a measure of reproductive success, for target species. Growth and mortality rates of species that are targeted by fisheries within and outside reserves should be monitored to assess the effects of the reserve on productivity and provide estimates of natural mortality for use in stock assessment models. Egg production, or potential egg production, should be monitored because fecundity of fish populations in reserves should improve if the age and size structure increase.
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Page 132 Fishery Data Derived from Reserves Established reserves provide a unique opportunity to determine fishery parameters needed to enhance the reliability of fishery management outside reserves. Through targeted monitoring of particular features of populations inside and outside reserves, important information on how fishing impacts the population can be obtained. Recovery Rates Immediately upon establishment of a reserve, the trajectory of ecosystem change can provide key information about the rest of the ecosystem that is difficult to obtain in any other way. Larval recruitment into a new reserve indicates the level of potential recovery of species from overexploited population sizes. For instance, failure of reserves along the north coast of Jamaica to rebound in fish population sizes, despite rebounds elsewhere in the Caribbean, suggests a regional collapse of larval availability due to long-term overfishing in Jamaica. Likewise, rapid recovery of certain fish and lobsters in the Florida Keys National Marine Sanctuary shows that aspects of the keys ecosystem can recover from current ecological stresses. Whether corals will return to abundance faster in areas of low human impact is a key question that only the reserves in the FKNMS can provide. It is possible that prior to reserve implementation, environmental degradation had been so severe that recovery is unlikely. Because we do not understand the nature of all of these “points of no return,” it is critical to carefully evaluate recovery rates relative to condition of the site at the time it was protected. Similarly, monitoring of the cod stocks on Georges Bank since the implementation of Closed Areas I and II will provide valuable information on cod population dynamics. Recovery of the stocks may be different within closures that are opened to scallop dredging versus those that remain closed. Understanding this process is crucial to the ability to implement and manage future cod closures or to understand the relationship between cod populations and populations of other important benthic and pelagic species. Monitoring Export A key feature of reserves for fishery management or biodiversity enhancement is the ability to export adults, juveniles, larvae, or eggs from within the reserve to the surrounding ecosystem. Understanding the nature and magnitude of this export function will require more extensive research and will require monitoring of reserves and surrounding areas for evidence of such transport. Bennett and Attwood (1993) showed that fish from reserves moved outside with rates that were specific to different species, but they did not observe net
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Page 133export in these South African systems. McClanahan and Kaunda-Arara (1996) addressed the export issue indirectly by examining fishing records outside a Kenyan reef reserve. They noted an increase in CPUE at the reserve boundary, suggesting a strong export function. However, there was a decrease in CPUE farther away from the reserve and placements of fish traps suggested that local fishers had moved traps to the periphery of the reserve and were apparently catching most of the exported fish. Likewise, Russ and Alcala (1996) saw an overall increase in fish capture in communities surrounding reserves in the Philippines. Studies of recruitment inside and outside reserves will be needed to derive estimates of export distance that are more direct. Hockey and Branch (1994) showed an exponential decline in recruitment of an intertidal limpet at increasing distances from a reserve in the Canary Islands. Castilla and Varas (1998) showed that spores of the short-distance dispersing kelp Durvillia are more common inside the reserve than outside. Stoner and Ray (1996) found that larvae of the queen conch were more common within the boundaries of a reserve in Bermuda, but they did not determine the pattern of drop-off of larval abundances beyond the reserve boundary. Theoretical predictions of long-distance export on the basis of oceanic current patterns and larval life histories (Roberts, 1997b) suggest that some reserves are likely to be sources for larvae that may recruit far downstream, whereas others may serve as sinks, with no suitable downstream areas for settlement of juveniles. These potential patterns should be tested against observed measurements of average larval dispersal from existing reserves, but such measurements are not yet available. Data on coral reef fish recruitment (Jones et al., 1999; Swearer et al., 1999), and the genetic differences among populations relative to current patterns (Shulman and Bermingham, 1995; Palumbi, 1997; Barber et al., 2000; Cowen et al., 2000) suggest that, in many cases, larval dispersal may be far lower than predicted by oceanographic models of passive particle flow. Hence, direct measurements of larval retention within reserves and the dispersal of larvae outside reserve boundaries will be needed to assess the capacity of reserves to self-replenish and function as sources of new recruits to surrounding areas (Kramer and Chapman, 1999). Habitat Maintenance and Recovery In reserves, MPAs, and surrounding open areas, habitat features and status should be monitored to evaluate the potential to sustain diverse and productive communities or fishery landings. For example, the extent and condition of substrates, seagrasses, corals, and live-bottom reef habitats, as well as water quality, should be monitored regularly to determine trends in the condition of MPA habitats. Many other biological and environmental variables can be included in
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Page 134the suite of monitored features or processes (e.g., weather, freshwater inputs, circulation variables, primary production, zooplankton, benthic communities). Indicators of Environmental Degradation Many previous reports have described the requirements for effective marine environmental monitoring (NRC, 1990, 2000a, b; Jameson et al., 1998) in more detail than can be offered here. Indicators particularly relevant to MPAs may include dissolved oxygen and nutrients for assessing eutrophication, contaminant loads for specific toxic chemical pollutants, salinity and turbidity for landbased runoff, and chlorophyll for primary productivity. The specific needs will depend on the location of the MPA; for example, in the Florida Keys it would be appropriate to monitor the percentage of live coral cover and water temperature to evaluate the condition of the reefs. In other areas, there may be specific species that could be used as sentinels for a change in environmental quality. Social and Economic Indicators Many MPAs are as concerned with tourism as with fishing. Therefore it is important to include monitoring of public perception and use of MPAs to help managers respond to community concerns and adapt regulations to improve their effectiveness. To quote from the Joint Group of Experts on the Scientific Aspects of Marine Pollution (GESAMP, 1996) publication: Baselines and monitoring that document public perceptions and governance procedures should be in place from the beginning, so that the social sciences can be applied to overcoming social problems and the effectiveness of governance can be assessed and appropriate actions taken. For fisheries, the institution of either fishery or ecological reserves will precipitate changes at local and regional scales. It is important to monitor changes in the human dimensions of the fishery so that the cultural and bioeconomic consequences of the reserve can be evaluated. The involvement, effort, and behavior of fishers must be monitored to judge how the reserve has impacted the fishery. The number of fishers, number of vessels, and distribution of the fishing effort in time and space should be monitored at least seasonally. Ideally, this information would be available, or could be obtained, before implementing the reserve to determine how much reserves affect human activities. Monitoring levels and values of catch, amounts of effort directed at key species, and costs of fishing in the vicinity of the reserve will provide the knowledge necessary to determine the social and economic benefits and costs of instituting the reserve. In cases where there are recreational and commercial sectors in a fishery, both
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Page 135must be monitored at local and regional scales, especially if a marine reserve changes the allocation of access to fishery resources among sectors. The economic indicators derived from monitoring will provide information to judge how the value of the fishery has been affected by a reserve or over what time frame the reserve might be beneficial if ecosystem properties were enhanced and fishery productivity improved both locally and regionally. In a cultural and social sense, issues of satisfaction also can be addressed through monitoring efforts, especially through surveys of participants in sectors of the fisheries. The results of monitoring (ecological and socioeconomic) should be made available on a regular basis to ensure that fishers are fully informed about the performance of reserves. RESEARCH NEEDS Attempts to design MPAs and reserves have identified major gaps in our understanding of marine ecosystems, gaps that will have to be filled to optimize the use of reserves in marine management. How will new knowledge improve the design and monitoring of MPAs and marine reserves? MPAs and reserves present opportunities for conducting ecological experiments on spatial and temporal scales that have only infrequently characterized studies in marine ecology. Furthermore, basic research in marine ecology and research involving the study of reserves are mutually beneficial. Whereas theories of marine ecology are essential for formulating hypotheses on the optimal design of reserves, reserves provide unparalleled opportunities for testing hypotheses in marine ecology, especially those involving predictions about effects occurring over wide spatial and temporal scales and effects of human impacts on marine ecosystems. Preceding sections of this report have highlighted gaps in our understanding of marine ecosystems. Here, some of these issues are reexamined to emphasize where research efforts are most needed. Connectivity Many important shortfalls in our understanding of marine ecosystems, as well as of MPA and reserve design, are related to “connectivity” (see Chapter 6). This concept applies to several phenomena that lie at the very core of marine ecosystem analysis. Life-History Requirements for Connectivity What types of habitats do species need during stages of their life histories, and how can the design of MPAs and reserves help ensure that individuals will have access to these habitats? How close together must these habitats be? Research focusing on these questions will contribute to decisions regarding the
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Page 136protection of spawning grounds, benthic nurseries, and pelagic habitats required to support life histories of target species. Because the proximity of different habitats influences the probability of successful transition of organisms through different stages of their life cycles, it is necessary to determine the dispersal potential of each stage (Kramer and Chapman, 1999). Roles of Oceanography, Physiology, and Behavior in Dispersal The dispersal ranges of marine organisms may be the most important factor to consider in designing marine reserves (see Chapter 6). Dispersal of young may determine levels of recruitment inside and outside the boundaries of a reserve. To predict regional effects of reserves in particular, we must understand the dispersal of each stage in the life histories of key organisms. Research is needed on several issues that affect dispersal. The first is measurement of average larval dispersal distances. New approaches to evaluate dispersal include (1) detection of environmental signatures in fish otoliths (Swearer et al., 1999) and crustacean exoskeletons (DiBacco and Levin, 2000); (2) mark-and-release studies using a fluorescent compound to mark larval otoliths (Jones et al., 1999); and (3) determination of patterns of genetic isolation by distance to infer single-generation dispersal distances (Palumbi, 2000). Cowen et al. (2000) noted that simple advection models might overestimate larval dispersal distances, indicating the need to understand larval retention mechanisms and their role in promoting local recruitment. Critical factors determining larval dispersal potential include (1) current regimes that may determine where a larva or juvenile is transported; (2) behavioral capacities of the organism, which may help to determine whether it is passively carried by currents or able to govern, at least in part, where it settles to become an adult; and (3) physiological abilities, including metabolic rates and level of energy stores, which may determine the potential duration of the larval or juvenile stage (Marsh and Manahan, 1999; Marsh et al., 1999). To understand dispersal, a multidisciplinary research and modeling program is required that blends ecology, genetics, oceanography, behavioral biology, and physiology. Genetic Connectivity The high dispersal potential of many marine species has implications for the geographic distribution and genetic connectivity among marine populations. In theory, even low levels of migration among populations will suffice to maintain genetic homogeneity (an indication of connectivity), dependent on the level of selection pressure operating on any given population. Therefore, the genetic connectivity of widely separated populations may be tested by measuring the degree of divergence in their genomes. A high level of divergence indicates that genetic connectivity is low, suggesting limited dispersal. Conversely, low diver-
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Page 137gence (genetic homogeneity) is less informative because even modest levels of dispersal (in the range of a single migrant per generation) are sufficient to maintain homogeneity. Genome divergence can thus be used to test predictions about the dispersal potential of various species. For example, do species with long-lived pelagic larval or juvenile stages have greater genetic homogeneity across their full biogeographic range than species with brief larval or juvenile stages? Is there enough dispersal to provide sufficient gene flow to prevent the divergence of genomes in widely separated populations? Are species with lower dispersal capabilities characterized by finer-scaled adaptations (i.e., are they relatively specialized for a habitat characteristic at a particular locale—for instance, temperature)? A high degree of specification for a particular habitat may translate into less successful larval or juvenile colonization in widely separated marine reserves. Shulman and Bermingham (1995) described divergence in mitochondrial DNA of coral reef fish populations in the Caribbean, showing that some populations were significantly differentiated, but others were not. Surprisingly, fish with the lowest dispersal capability did not have the greatest structure, and significant gene flow corridors were not necessarily predictable based on oceanic currents. Likewise, Barber et al. (in press) recently showed strong genetic endemism in Indonesia reef shrimp species, discovering that strong ocean currents do not homogenize genetic structure even over short distances. The history of marine populations since sea-level rise may play an important, though sometimes hidden, role in their ecological exchange from locality to locality. With the development of molecular techniques for genetic analysis, including very small larval stages, it will be possible to resolve many questions about genetic connectivity among populations. Recent studies indicating that dispersal may be more limited than previously assumed (Palumbi, 2000), confirm that genetic homogeneity is not a reliable indicator of dispersal at the level necessary to sustain reserves in an ecological time frame (Palumbi, in review). Local Versus Regional Analyses One reason we know so little about the diverse issues grouped under the heading of “connectivity” is that most research has focused on local effects, not regional influences of reserves. The absence of data documenting regional effects of reserves may, of course, be a sign that these effects are in fact minimal. This could occur where exploitation near a reserve's boundaries eliminates any potentially important regional influences (McClanahan and Kaunda-Arara, 1996). However, the major reason for lack of understanding of regional effects is the absence of research on the influences of the relatively small area within a reserve on the vast area outside. The shortfall in our understanding of regional effects of reserves reflects a general gap in knowledge of how local habitats are coupled to the regional ecosystem. Studies of dispersal of all life stages, including the
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Page 138movement of adults of economically important species in and out of reserves, are required to evaluate the efficacy of MPAs with respect to regional enhancement of stocks. Studies of Unexploited Species Because many reserves have been established in response to the collapse of stocks of one or more important exploited species, the focus of research and monitoring within marine reserves has customarily been on a small number of species of economic significance (see Table 7-1). Economic significance and ecological significance do not always coincide. Many organisms necessary for the restoration of natural ecosystem functioning may be ignored when the focus is exclusively on the few fished species. Hence, it is essential that increased attention be given to nonfished species that play important roles in marine ecosystems. Biodiversity The effects of reserves on biodiversity at a regional scale are even more poorly understood than the regional effects of reserves designed for fishery enhancement. Even though reserves have usually been created to conserve biodiversity within the protected area, the broader, regional effects of these reserves merit closer study. Trends in Biodiversity Biodiversity can be examined at all organizational levels, from the large-scale diversity of ecosystems to the minutiae of genetic diversity within a particular population. In most cases, studies on biodiversity focus on species diversity as the primary indicator of changes at either higher or lower levels of organization. Species diversity may be divided into four components: 1. species richness—the number of species present; 2. species evenness—the relative abundances of different species; 3. species composition—the nature of the species present (i.e., species list); and 4. species interactions—the effects of a species on the composition of the community and its temporal and spatial variation (Chapin et al., 2000). Reserves established in regions that have experienced minimal exploitation by humans, and thus remain relatively pristine, offer a unique opportunity to study changes in ecosystems and species diversity due to factors other than anthropogenic influences. Long-term research in reserves may allow the effects
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Page 139of natural variation—for instance, in climate—to be clearly delineated from the effects of human activities. An example of the benefits of this type of long-term study of biodiversity is given by research conducted in the biological reserve at Stanford University's Hopkins Marine Station in Pacific Grove, California, which was designated an ecological reserve (except for scientific collecting) in 1931. Surveys conducted at the time the reserve was established provided key baseline data on species composition and abundance. Studies of biodiversity in the mid-1990s documented large-scale changes in species composition and relative abundances that were conjectured to be caused by the warming trend that occurred during this approximately 65-year interval (Barry et al., 1995; Sagarin et al., 1999). Research at the Hopkins site indicates how important a role reserves can play in elucidating natural, that is, nonanthropogenic, changes in biodiversity. Parallel examination of biodiversity in pristine sites and in similar sites that have experienced extractive activities may allow the effects of human impacts on biodiversity to be more clearly delineated. Studies of Exploited Species Dispersal of Adults: Tagging Studies Tagging studies have been used in fishery research to track the movements of fish. These methods can be used to track adults from reserves into outlying unprotected waters to provide a number of types of important fishery data. First, the efficacy of a reserve as a resource for replenishing stocks of commercially exploited species can be established by recording the numbers of marked adults that are captured (or otherwise observed) outside the boundaries of a reserve. Tagging thus allows testing of hypotheses about the “spillover” effects of reserves. The reserve's contribution to stocks in unprotected waters may be evaluated, to a first approximation based on the dispersal distances and number of marked adults recaptured outside the reserve. Mark-recapture studies may also provide insights into temporal changes within a reserve. If an intensively exploited area is placed under protection, the quality of habitat is likely to vary with time. The fraction of individuals resident within a reserve may change over time, in concert with regeneration of the physical and biological features of the habitat. Properly designed mark-recapture studies conducted within reserves could reveal whether individuals from regions outside the reserve enter and remain. The use of tagging studies in research and monitoring efforts in reserves will provide more information on dispersal patterns as technologies improve. Although standard tagging techniques will probably continue to be the primary approach, electronic tagging employing microprocessors has increasing potential (Metcalfe and Arnold, 1997; Block et al., 1998b; Cote et al., 1998). The most sophisticated of these electronic tags communicate with satellites, providing data
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Page 140on geoposition in addition to data on vertical movements and thermal history. Because these tags are relatively large, they have been used primarily to track movements of large pelagic fish such as tuna (Block et al., 1998a, b). However, development of smaller versions will encourage wider use. Acoustic telemetry tags also show great promise. They allow relatively precise tracking of fish, as shown by studies of daily and seasonal movements of juvenile Atlantic cod (Gadus morhua) (Cote et al., 1998). These tags may not be well suited for tracking dispersal over long periods, however, because the fish must be followed continuously from close proximity. Chemical marking is another method used to track the movements of fish and identify sites of origin and nursery habitats of a stock. The trace-element composition of teleost otoliths (earstones) contains a distinct “signature” from the chemistry of the local water mass in which a particular layer of the otolith was deposited (Campana, 1999; Swearer et al., 1999; Campana et al., 2000). Larvae developing in coastal waters have different trace-element levels in their otoliths from larvae developing in the open ocean. These chemical signatures will persist throughout the lifetime of a fish, allowing determination of the sites of origin of stocks (Campana et al., 1995) and nursery grounds used during development (Gillanders and Kingsford, 1996). Chemical labeling of otoliths in embryos and newly hatched larvae with tetracycline or other chemical markers yields a distinct, permanent mark that has proven useful to track larvae (Secor et al., 1995; Reinert et al., 1998; Jones et al., 1999) and is applicable to following movements or identifying origins of adults as well. Density-Dependent Effects on Recruitment and Growth It is seldom possible to separate effects of fishing on stocks from effects of environmental variability. Networks of fishery reserves could provide a mosaic of fish densities with which to compare how density affects processes such as growth and local recruitment. It is important to determine the life stages most sensitive to density-dependent effects in order to judge whether a reserve might increase recruitment potential locally or through dispersal of prerecruits to adjacent areas that are open to fishing. Fishery scientists generally attempt to link recruitment to adult stock density without consideration of how adults are distributed in space. Research on such processes in reserves will allow efficient, spatially explicit strategies to be developed that will advance understanding of population dynamics over a range of spatial scales. Models of population growth and regulation frequently include parameters that express impacts of changing densities on egg production, recruitment, individual growth, and survival, but information about effects of density is frequently difficult to obtain. Populations of exploited species inside reserves are in general 30-100% larger than populations outside (Halpern, in review), and such differences in overall density may provide a natural laboratory to evaluate the
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Page 141density dependence of growth and mortality rates. Likewise, the impact of exploited species on other ecosystem components (e.g., prey species and trophic cascades) may be evaluated by comparing across populations at different density. Such studies need to be conducted with proper concern for design and replication, but the mosaic of population densities in a network of reserves and exploited sites may be a powerful tool to elucidate mechanisms of density dependence in marine population dynamics. Natural Mortality Natural mortality rate is a key parameter in fish population modeling and stock assessments, but it is notoriously difficult to estimate (Clark, 1999). Specifically, it is hard to separate the total mortality of a fish stock into its fishing and natural mortality components. Reserves could provide areas where fishing mortality rates are essentially zero, greatly facilitating estimation of the natural mortality rate, provided migration is low or can be estimated by tagging studies. What Types of Research Should Be Allowable in Marine Reserves and Protected Areas? If we accept the argument presented above that reserves afford unique opportunities for research, it is critical to define the kinds of experimentation that are to be allowed in reserves of different types. A fundamental requirement in all categories of MPAs is that no research should be allowed that might defeat the objectives. It is important, therefore, to tailor the types of research allowed within the MPA to the level of protection intended for each zone. Here, it may be most appropriate to examine allowable research activities in the context of the categories of MPAs delineated by the International Union for the Conservation of Nature and Natural Resources (IUCN, now the World Conservation Union). At one extreme in this categorization are “wilderness” MPAs (IUCN Category I) in which human effects from extractive activities and other forms of perturbation have been minimal. Such wilderness MPAs are inappropriate sites for conducting studies that, either by intent or by accident, could damage the existing natural ecosystem. For instance, evaluation of the effects of trawling or other extractive techniques should not be carried out in MPAs of this class, but completely non-destructive observational studies would be permitted. At the other extreme, MPAs that fit the IUCN's Category IV definition, “Habitat/Species Management Area,” may be suitable for resource exploitation. The definition of each category of MPA then carries with it limits to the amount of perturbation allowed. Ecological research usually involves a certain amount of environmental perturbation. For example, any sample of soft-bottom habitats must be taken with cores that have small impacts, and most studies rely on the retrieval of samples
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Page 142for taxonomic and voucher purposes. Such samples are extremely important because they preserve material for future researchers to evaluate genetic change as well as changes in species composition and abundance. Also, much ecological research depends on experimental manipulations. The same sorts of data are important to fishery scientists who also need to collect samples for life-history, growth, and fecundity measurements. To prohibit such research denies some of the principal value of MPAs. On the other hand, excessive destructive sampling violates the purpose of MPAs. In any type of MPA in which research is allowed, conflicts may arise between groups of scientists who have different research objectives and experimental approaches. For instance, conflicts seem likely to arise if one research program wishes merely to observe the biota in a reserve, perhaps in order to establish a time series of naturally occurring changes, whereas another group wishes to do manipulative research involving protocols, such as transplantation or clearing of sites to study recruitment. Even if both “observational” and “manipulative” research activities are legally permissible in an MPA, mechanisms for resolving conflicts between researchers with divergent interests will be needed. These considerations argue strongly for the establishment of MPA research oversight committees that would evaluate proposed research with review processes that not only evaluate the merit of the science per se, but also analyze the potential impact of the research on the MPA. Some of the national marine sanctuaries have committees for this purpose (e.g., see information on the Research Activities Panel of the Monterey Bay National Marine Sanctuary at http://www.mbnms.nos.noaa.gov), and the general adoption of such review panels seems warranted in any reserve in which research, beyond monitoring, is to take place. Research on the Costs and Benefits of Marine Reserves One of the most critical areas for future research is comparative cost-benefit analysis of conventional fishery management relative to marine reserves alone or with marine reserves as a supplementary tool. Reserves may provide socially important benefits in addition to fisheries that conventional management does not provide. These benefits could include preservation of biodiversity, research and education, nonconsumptive values, recreation, and tourism. However, there have been few studies on either the magnitude of these benefits or the criteria for measuring them. Thus, research on existing and newly created reserves will be required before we will know how reserves compare in a cost-benefit framework against conventional methods. Several types of research will be needed: (1) valuation of nonfishery benefits; (2) development of calibrated simulation models, incorporating spatial information, that forecast biological responses and reflect behavior and values of fishers and other user groups affected by reserves; and (3) empirical studies of reserves used as demonstration projects to involve
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Page 143stakeholders in tests of the value of reserves relative to conventional management approaches. MODELING Mathematical Modeling of Reserve Processes Although there is a well-developed theory of terrestrial reserves (Higgs and Usher, 1980; Gilpin and Soule, 1986; Pressey et al., 1993), a corresponding theory for marine systems has yet to be fully developed (Simberloff, 2000). Marine and terrestrial reserve theories need to be substantially different because the taxa involved have such different life-history traits and because marine systems are usually expected to yield commercial quantities of food from fishing. Terrestrial models often reference island biogeography theory (Simberloff, 1988) and tend to focus on preserving species or habitat richness in reserves, with little or no emphasis on repopulating adjacent areas to support hunting. In contrast, marine reserve models typically focus on single species, with an emphasis on population dynamics under conditions of human exploitation. Gerber et al. (in review) categorize existing marine reserve models primarily by (1) whether the model is for single or multiple species, (2) what the key life-cycle elements and larval redistribution mode are, (3) what the density-dependent recruitment mode is, and (4) whether adult migration, stochasticity, and rotating spatial harvest are included in the model. They summarize several key results that appear to be general to virtually all types of models. In particular, at a constant level of effort that would otherwise result in overfishing, models indicate that reserves would increase the yield of the fishery relative to conventional management. A primary value of reserves in these circumstances is the higher reproductive capacity of adults protected from fishing. Models suggest that larger reserves would be required for species with high rates of juvenile and adult movement. A second condition for high efficiency of reserves that has emerged from various models is that the target species should have moderate rates of juvenile and adult movement (DeMartini, 1993). These modeling results appear to apply generally to fishery reserves, but they are based on a very limited set of environmental assumptions. For example, most models assume that all larvae come from a larval pool distributed equally to potential juvenile habitats. In addition, most models do not allow for a number of reserves, and none allow reserves to be of different sizes or embedded in realistic current regimes. Thus, these conclusions from the first simple models are not realistic enough to be used predictively in specific reserve situations. Currently, the most common form of reserve modeling is to assume that a habitat is divided into a reserve portion where fishing is limited and a portion in which fishing continues. Eggs produced throughout the habitat develop into a
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Page 144common pool of larvae, distributed proportionately into reserve and nonreserve areas. The value of the reserve depends on the redistribution of fishing effort into the nonreserve area and the level of fishing pressure. Multispecies and Trophic Models A great majority of marine reserve models focus on the population dynamics of single species. Even though they are complex in their treatment of fishing mortality rates and population subdivision, in most cases, the population size of only one species is considered. Recently, trophic simulations based on the Eco-Path model have begun to incorporate fishery reserves (Walters et al., 1997). Such models try to estimate the impact of reserves on biomass at all trophic levels in an ecosystem, by estimating the flow of biomass from one trophic level to the next with and without fishing pressure. So far, these models do not allow a complex mosaic of fishing efforts and do not include terms to describe the connectivity among different marine populations. They also focus on biomass rather than number of individuals or individual size, so the relationship between these results and typical fishery theories is not yet well known. However, it is clear that single-species models, no matter how complex they are in habitat structure and dispersal capacity, will not capture the community-wide effects of reduced fishing pressure and that efforts to develop multispecies models are one of the next frontiers in modeling the biological properties of marine reserves.
Representative terms from entire chapter: