Marine Protected Areas - New Document

Decision analysis for designing marine protected areas
for multiple species with uncertain fishery status

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J. WILSON WHITE,1,3 LOUIS W. BOTSFORD,1 ELIZABETH A. MOFFITT,1
AND DOUGLAS T. FISCHER
1,2
1Department of Wildlife, Fish, and Conservation Biology, University of California, One Shields Avenue, Davis, California 95616 USA
2Geography Department, California State University, 18111 Nordhoff Street, Northridge, California 91330-8249 USA

Abstract. Marine protected areas (MPAs) are growing in popularity as a conservation
tool, and there are increasing calls for additional MPAs. Meta-analyses indicate that most
MPAs successfully meet the minimal goal of increasing biomass inside the MPA, while some
do not, leaving open the important question of what makes MPAs successful. An oftenoverlooked aspect of this problem is that the success of fishery management outside MPA
boundaries (i.e., whether a population is overfished) affects how well MPAs meet both
conservation goals (e.g., increased biomass) and economic goals (e.g., minimal negative effects
on fishery yield). Using a simple example of a system with homogeneous habitat and
periodically spaced MPAs, we show that, as area in MPAs increases, (1) conservation value
(biomass) may initially be zero, implying no benefit, then at some point increases
monotonically; and (2) fishery yield may be zero, then increases monotonically to a maximum
beyond which further increase in MPA area causes yield to decline. Importantly, the points at
which these changes in slope occur vary among species and depend on management outside
MPAs. Decision makers considering the effects of a potential system of MPAs on multiple
species are confronted by a number of such cost–benefit curves, and it is usually impossible to
maximize benefits and minimize costs for all species. Moreover, the precise shape of each curve
is unknown due to uncertainty regarding the fishery status of each species. Here we describe a
decision-analytic approach that incorporates existing information on fishery stock status to
present decision makers with the range of likely outcomes of MPA implementation. To
summarize results from many species whose overfishing status is uncertain, our decisionanalysis
approach involves weighted averages over both overfishing uncertainty and species. In
an example from an MPA decision process in California, USA, an optimistic projection of
future fishery management success led to recommendation of fewer and smaller MPAs than
that derived from a more pessimistic projection of future management success. This example
illustrates how information on fishery status can be used to project potential outcomes of
MPA implementation within a decision analysis framework and highlights the need for better
population information.
Key words: California, USA; decision analysis; decision support; fishery stock status; fishery yield;
marine protected area (MPA); metapopulation persistence; overfishing; spatially explicit population model.

Ecological Applications, 20(6), 2010, pp. 1523–1541
 2010 by the Ecological Society of America

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