Department of Wildlife, Fish, and Conservation Biology, University of California, One Shields Avenue, Davis, California 95616, USA.
Ecol Appl. 2010 Sep;20(6):1523-41. doi: 10.1890/09-0962.1.
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 often-overlooked 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 decision-analysis 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.
海洋保护区（MPA）作为一种保护工具越来越受欢迎，人们越来越呼吁增加更多的 MPA。荟萃分析表明，大多数 MPA 成功地达到了增加 MPA 内生物量的最低目标，而有些 MPA 则没有，这就提出了一个重要的问题，即是什么使 MPA 成功。这个问题的一个经常被忽视的方面是，MPA 边界外渔业管理的成功（即，一个种群是否过度捕捞）会影响 MPA 如何既能达到保护目标（例如，增加生物量），又能达到经济目标（例如，对渔业产量的负面影响最小）。我们使用一个具有均匀生境和定期间隔的 MPA 的简单系统示例，表明随着 MPA 面积的增加，（1）保护价值（生物量）最初可能为零，意味着没有收益，然后在某个点单调增加；（2）渔业产量可能为零，然后单调增加到一个最大值，超过这个最大值，进一步增加 MPA 面积会导致产量下降。重要的是，这些斜率变化的点在不同的物种之间是不同的，并且取决于 MPA 之外的管理。考虑潜在 MPA 系统对多种物种影响的决策者面临着许多这样的成本效益曲线，通常不可能为所有物种实现效益最大化和成本最小化。此外，由于每个物种的渔业状况存在不确定性，每个曲线的精确形状是未知的。在这里，我们描述了一种决策分析方法，该方法利用渔业资源状况的现有信息，为决策者提供 MPA 实施的可能结果范围。为了总结不确定过度捕捞状态的许多物种的结果，我们的决策分析方法涉及对过度捕捞不确定性和物种的加权平均值。在美国加利福尼亚州的一个 MPA 决策过程的示例中，对未来渔业管理成功的乐观预测导致建议设立更少和更小的 MPA，而不是根据对未来管理成功的更悲观预测得出的建议。这个例子说明了如何在决策分析框架中利用渔业状况信息来预测 MPA 实施的潜在结果，并强调了需要更好的种群信息。
