Designing marine reserve networks for both conservation and fisheries management

Abstract

Marine protected areas (MPAs) that exclude fishing have been shown repeatedly to enhance the abundance, size, and diversity of species. These benefits, however, mean little to most marine species, because individual protected areas typically are small. To meet the larger-scale conservation challenges facing ocean ecosystems, several nations are expanding the benefits of individual protected areas by building networks of protected areas. Doing so successfully requires a detailed understanding of the ecological and physical characteristics of ocean ecosystems and the responses of humans to spatial closures. There has been enormous scientific interest in these topics, and frameworks for the design of MPA networks for meeting conservation and fishery management goals are emerging. Persistent in the literature is the perception of an inherent tradeoff between achieving conservation and fishery goals. Through a synthetic analysis across these conservation and bioeconomic studies, we construct guidelines for MPA network design that reduce or eliminate this tradeoff. We present size, spacing, location, and configuration guidelines for designing networks that simultaneously can enhance biological conservation and reduce fishery costs or even increase fishery yields and profits. Indeed, in some settings, a well-designed MPA network is critical to the optimal harvest strategy. When reserves benefit fisheries, the optimal area in reserves is moderately large (mode ≈30%). Assessing network design principals is limited currently by the absence of empirical data from large-scale networks. Emerging networks will soon rectify this constraint.

Fig. 1.

Population connectivity among reserve and fished patches along a coast. (A) Larval export from a reserve (bold arrows) may benefit the fishery but may make a population in a single reserve non–self-sustainable. Sustainable reserves can be achieved through larval input from fished areas (thin arrows). For small reserves, this larval input dominates the population biology of the reserves. When populations outside the reserve decline, populations inside the reserve also decline unless they can receive larval input from other reserves (dashed arrow). As a result, unless there is significant input from nonfished areas, the demography of the reserve and the demography of fished areas will be tightly coupled, and the success of the reserve ultimately will be determined by the success of fisheries regulations outside the reserve. (B) If a second reserve with a large enough population is sufficiently close, its connections with the original reserve can help stabilize its populations (dashed, two-way arrows).

Fig. 2.

Synthesis of 33 peer-reviewed scientific publications representing 57 case studies that explicitly examined how much area should be protected from fishing to maximize long-term fishery yield and/or profit. (Papers were obtained via an ISI Web of Science search on July 14, 2009 using keywords “marine reserve(s)” OR “marine protected area(s)” AND “yield” OR “profit.” We recovered 131 papers and considered all appropriate ones.) (A) Number of studies concluding that fishery yields/profits were maximized via management without versus with the use of marine reserves. (B) Frequency distribution of the percentage of fishing grounds recommended to be included in marine reserves in the studies that found reserves to be a part of yield/profit-maximizing management. Literature included in the survey is available on request from the authors.