Coastal Oregon Marine Experiment Station, Oregon State University, Newport, Oregon, USA.
Department of Fisheries, Wildlife, and Conservation Sciences, Oregon State University, Newport, Oregon, USA.
Ecol Appl. 2024 Oct;34(7):e3027. doi: 10.1002/eap.3027. Epub 2024 Sep 10.
Adaptively managing marine protected areas (MPAs) requires accurately assessing whether established MPAs are achieving their goals of protecting and conserving biomass, especially for harvested populations. Ecological MPA assessments commonly compare inside of the MPA to a reference point outside of and/or before implementation (i.e., calculating "response ratios"). Yet, MPAs are not simple ecological experiments; by design, protected populations interact with those outside, and population dynamic responses can be nonlinear. This complicates assessment interpretations. Here, we used a two-patch population model to explore how MPA response ratios (outside-inside, before-after, and before-after-control-impact [BACI]) for fished populations behave under different conditions, like whether the population is receiving a sustainable larval supply or if it is declining despite protection from harvest. We then conducted a Bayesian evaluation of MPA effects on fish and invertebrate populations based on data collected from 82 published studies on 264 no-take MPAs worldwide, using the results of an earlier global meta-analysis as priors. We considered the effects of calculating different summary metrics on these results, drawing on the theoretical insights from our population model as a comparative framework. We demonstrate that not all response ratio comparison types provide the same information: For example, outside-inside and BACI comparisons can fail to detect population decline within MPAs, whereas before-after comparisons likely detect that pattern. Considering these limitations, we nonetheless found that MPAs globally are producing positive outcomes, with on average greater biomass, density, and organism size within their boundaries than reference sites. However, only a small portion of studies (18 of 82) provided the temporal data necessary to determine that protection, on average, has led to increased abundance of populations within MPAs over time. These findings demonstrate the importance of considering the underlying system dynamics when assessing MPA effects. Assuming that large outside-inside or BACI response ratios always reflect large and net positive conservation effects may lead to misleading conclusions, we recommend that: (1) when assessing specific MPA effects, empirical findings be considered alongside theoretical knowledge relevant to that MPA system, and (2) management should respond to the local conditions and outcomes, rather than a blanket expectation for positive MPA effects.
适应性地管理海洋保护区 (MPA) 需要准确评估既定的 MPA 是否实现了其保护和养护生物量的目标，特别是对于已收获的种群。生态 MPA 评估通常将 MPA 内的情况与外部参考点或实施前的情况进行比较（即计算“响应比”）。然而，MPA 并不是简单的生态实验；受保护的种群与外部种群相互作用，种群动态响应可能是非线性的。这使得评估解释变得复杂。在这里，我们使用两斑块种群模型来探索受捕捞种群的 MPA 响应比（内外、前后和前后对照影响[BACI]）在不同条件下的表现，例如种群是否正在接收可持续的幼虫供应，或者尽管受到捕捞的保护，种群是否仍在下降。然后，我们根据从全球范围内 82 项关于 264 个禁渔 MPA 的已发表研究中收集的数据，利用先前全球荟萃分析的结果作为先验知识，对 MPA 对鱼类和无脊椎动物种群的影响进行了贝叶斯评估。我们考虑了计算不同汇总指标对这些结果的影响，以我们的种群模型的理论见解为比较框架。我们证明，并非所有的响应比比较类型都提供相同的信息：例如，内外和 BACI 比较可能无法检测到 MPA 内的种群下降，而前后比较可能会检测到这种模式。考虑到这些限制，我们仍然发现，全球范围内的 MPA 正在产生积极的结果，其边界内的生物量、密度和生物体大小平均高于参考地点。然而，只有一小部分研究（82 项研究中的 18 项）提供了确定保护在时间上导致 MPA 内种群数量增加所需的时间数据。这些发现表明，在评估 MPA 影响时，考虑到底层系统动态非常重要。假设大的内外或 BACI 响应比总是反映出大的、净积极的保护效果，可能会导致误导性的结论，我们建议：（1）在评估特定的 MPA 效果时，应将经验发现与与该 MPA 系统相关的理论知识一并考虑；（2）管理应根据当地条件和结果做出响应，而不是一概期望 MPA 产生积极效果。
