The list of potential benefits from closing ocean areas to extractive uses include the conservation of biodiversity within these reserves and the improvement of conditions for fisheries outside of them - the latter owing to the export of larvae and spillover of adults from the protected areas. Some marine reserves have been designated with both conservation and increased fisheries yields as goals, seeking a win-win situation for biodiversity and fishermen.
But the ability of reserves to achieve both goals simultaneously remains easier to conceptualize than to document, due partly to the challenges of following rigorous scientific protocols in the ocean environment (see the MPA Perspective pieces, this issue, for more coverage of the dilemma). As a result, practitioners looking for guidance on balancing conservation and fisheries yields are left to adapt often-complex population and economics models to their protected areas - no easy task. This month, in an attempt to distill a set of lessons and recommendations from the theoretical study of marine reserves, MPA News discusses with scientists how practitioners can tackle the challenge.
Using decision-support tools
Trevor Ward, former program manager for environmental research in the Division of Fisheries at Australia's Commonwealth Scientific and Industrial Research Organization (CSIRO), says achieving the win-win situation - what he calls the "double payoff" - is possible. In fact, as he points out, Australia's government and the Australian Northern Prawn Fishery (NPF) are working right now to design reserves capable of delivering the double payoff.
Ward recently co-authored a report with Eddie Hegerl of Marine Ecosystem Policy Advisors (an Australian consultancy) on the use of MPAs in ecosystem-based management of fisheries (MPA News 5:5). They state that for MPAs to meet conservation and fisheries goals, there must be strong cooperation between conservation and fisheries agencies, and effective partnerships with stakeholders, as with the prawn fishery example. They caution that designs for the double payoff may require parameters and criteria that are fairly complex to account for the impact of multiple reserve scenarios on fish populations, habitats, and fisheries economics.
"Conservation and fishery objectives can sometimes be in opposition to each other and involve large uncertainties," says Ward. "So achieving good double-payoff reserve designs will require decision-support tools that can optimize across multiple competing objectives, and can admit multiple competing costs and measures of uncertainty." To manage this complexity, computers and special software are usually necessary. Ward says one of the most promising tools - particularly for larger, multi-habitat, multi-species reserve situations - is MARXAN, which was used to develop the re-zoning scheme for the Great Barrier Reef Marine Park (MPA News 4:11). Information on MARXAN is available online at http://www.ecology.uq.edu.au/marxan.htm.
In some parts of the world, however, reserve planners may not have easy access to sophisticated decision-support tools, nor the expertise to operate them. Ward says it is still possible to achieve a win-win situation in these cases, at least for smaller, simpler reserve scenarios. "The most important aspect of double-payoff reserve design is the problem formulation and logical framework that underpins the approach to reserve selection, and particularly accepting the equivalence of the two different sets of objectives," says Ward. His advice to reserve planners without access to advanced decision-support systems is to ensure that:
- Objectives are clearly established in conjunction with a broad range of stakeholders;
- A fully systematic approach to reserve design is used, including measurement and mapping of biodiversity;
- The best available technical data and support are used;
- The reserve is well-integrated to the fishery management system;
- All assumptions and interim decisions in the reserve selection process are clearly articulated and documented for public review; and
- There is an effective monitoring system that relates to each objective, as a basis for future improvements in reserve design.
Ward says it is important to recognize that double-payoff reserves will not necessarily be the only type of protected area used to protect biodiversity in a particular region. "Since areas important to fisheries will not always cover the full spectrum of ecosystem and habitat types, or migratory species, other measures may be needed to ensure conservation of the full complement of biodiversity of a region," he says. Double-payoff reserves can be designed within an integrated region-wide planning process, in which different reserve types are developed concurrently to provide for marine resource management and biodiversity conservation. "I see double-payoff reserves as complementing and enhancing other MPA initiatives, not replacing them," he says.
Different designs for different goals
Reserves to achieve win-win situations for fish conservation and fisheries yields will be designed differently from those designed only for conservation, says Loo Botsford, a biologist at the University of California at Davis who has compared reserve-design models for the different goals. In short, he says, areas designed for conservation are best configured with a single large no-take zone, ensuring that most fish and larvae remain inside the reserve. Closures to aid fisheries, however, require networks of small reserves to maximize edge effects (larvae dispersing to fished areas), in turn maximizing yield. Incidentally, notes Botsford, the optimal fisheries reserve design could close a larger fraction of the coastline than the optimal conservation design.
Although this comparison suggests a basic conflict between the goals, he says a reconciliation may be possible. In a modelling study he conducted with Alan Hastings (see box at end of this article), Botsford noted that both conservation and fisheries needs could be served by the optimal fisheries reserve. Although conservation benefits would not be optimized by this design (in other words, fish would be captured), the benefits would still be significant, owing partly to the fact that the fisheries-reserve design closes a greater fraction of the coast. Whether the implementation of marine reserves actually increased catch in the fishery would depend on several factors:
- How hard the population had been fished. For species with sedentary adults, reserves can increase catch only if recruitment has been substantially diminished.
- The response of fishermen. If the same number of fishermen continued fishing between the reserves, an increase in catch would be less likely.
- Movement of adults. When adult movement is considered, making reserves smaller generally leads to greater losses from the reserves. There need to be some losses because that is the catch, but if losses are too great, the population will not be sustainable.
"For species with sedentary adults, a reserve with a specific linear dimension will sustain species with an average larval dispersal distance up to and including that dimension," says Botsford. "However, a system of small reserves will sustain species with any arbitrary average dispersal distance, as long as that system of reserves covers a certain minimum fraction of the coastline." Provided the fraction of coastline is large enough to sustain the species of interest, the network of smaller reserves should aid fisheries and conservation.
Botsford says there are several uncertainties to keep in mind when considering these results. One is the fraction of coastline that needs to be in reserves to sustain species dispersing all distances (i.e., the fraction of lifetime reproduction needed for sustainability), which is also one of the dominant uncertainties in conventional fisheries management. Another is that the results depend on larval dispersal patterns, about which there is little knowledge for most fish species (MPA News 4:9).
Closing marginally productive areas
Jim Sanchirico is an economist with Resources for the Future, a research institution studying environmental and resource policy, located in Washington, DC (USA). In studying the economics of marine reserves, he has shown that to achieve win-win situations for conservation and fisheries, the optimal site for closure may not always be the most biologically productive one.
"The best option for fishery enhancement may lie in closing a marginally productive site, which will still yield biological benefits," says Sanchirico. Assuming that entry to the fishery is limited through a licensing system, closing the most productive site theoretically increases costs for fishermen, thereby decreasing the value of their licenses. Increased costs for fishermen also raise the likelihood of strong opposition to reserve plans from the fishing industry. If planners are determined to close a productive site for biodiversity reasons, says Sanchirico, they could consider compensating the fishermen for the resulting lost profits. Compensation is controversial, he says, but it is consistent with the goal of aiding fisheries.
Site selection is not as easy as just picking out sites based on their biological and economic characteristics, he says. Planners must consider such factors as the condition of remaining fishable habitat, particularly in patches that are connected to the reserve. The value of a site as a reserve - as measured by bioeconomic habitat characteristics, dispersal processes of species, and oceanographic features of the system - is affected by the characteristics of these surrounding areas.
Again, there are a number of sources of uncertainty there. Nonetheless, Sanchirico notes, managers and policymakers make decisions in the face of uncertainty all the time: their decisions are based largely on the amount of risk they are willing to take with the results of their decisions. Preferably, Sanchirico would like to see managers invest in long-term, proactive, interdisciplinary research on bioregional ocean systems, including studies of the biology, ecology, oceanographic, and socioeconomic components of these systems. "So when the question arises, 'Which area do we set aside?', we will be better prepared to answer it," he says.
For more information:
Trevor Ward, Greenward Consulting, Perth, Western Australia, Australia. Tel: +61 8 9387 2866; E-mail: tjward [at] bigpond.net.au
Louis Botsford, Wildlife, Fish & Conservation Biology, University of California, Davis, CA 95616, USA. Web: wfcb.ucdavis.edu
James Sanchirico, Resources for the Future, 1616 P Street NW, Washington, DC 20036, USA. Tel: +1 202 328 5095; E-mail: sanchirico [at] rff.org
BOX: Links to related studies
Trevor Ward and Eddie Hegerl. 2003. Marine Protected Areas in Ecosystem-Based Management of Fisheries (Department of the Environment and Heritage, Australia). http://www.deh.gov.au/coasts/mpa/wpc/fisheries.html
Alan Hastings and Louis W. Botsford. 2003. Comparing designs of marine reserves for fisheries and for biodiversity. Ecological Applications 13(1) Supplement, pp.S65-S70. http://www.esapubs.org/esapubs/journals/applications_main.htm (Click your way through to Volume 13 (2003) of Ecological Applications, then click "Issue 1, Supplement".)
Jim Sanchirico's work on the economics of marine reserves is available at http://www.rff.org/Sanchirico.cfm