Pre-closure fishing pressure predicts effects of marine protected areas

1. Marine Protected Areas (MPAs) can be effective tools for marine resource management. However, despite evidence of the positive effects of MPAs, such as increases in body sizes of organisms targeted by fisheries, there is often heterogeneity in biological outcomes among them. 2. Because fishing can drastically impact fish populations, the goal of this study was to determine if the levels of exploitation prior to protection could predict variation in the magnitude of MPA effects. 3. Using a diver operated stereo-video camera system, we compared sizes of fishes targeted by anglers within seven MPAs spanning the Southern California Bight to nearby comparison areas (non-MPAs). We used fine-scale data on pre-closure fishing pressure to test responses of fishes to protection along a gradient of exploitation. 4. Fish size responded to protection in proportion to pre-closure fishing pressure, with MPAs in areas with high pre-closure fishing having greater responses in average lengths and size distributions than those in areas with low fishing pressure. 5. This response was evident in species heavily targeted by recreational fishing, but not in species that were not targeted in fisheries. 6. Synthesis and applications: Pre-closure fishing pressure of an area can impact the efficacy of MPAs, and, when available, should be considered when predicting and evaluating MPA performance. Prioritizing heavily exploited areas for protection when implementing spatial management tools could maximize ecological outcomes.1. 海洋保护区（Marine Protected Areas, MPAs）是开展海洋资源管理的有效工具。尽管已有研究证实海洋保护区可带来积极效应，例如渔业目标物种的个体体型增大，但不同保护区间的生物学响应往往存在异质性。 2. 由于捕捞活动会对鱼类种群造成剧烈影响，本研究旨在探究保护前的捕捞压力水平是否能够预测海洋保护区效应强度的差异。 3. 本研究采用潜水员操控式立体摄像系统，对横跨南加州湾的7个海洋保护区内及邻近对照区域（非海洋保护区）中休闲垂钓目标鱼类的体型进行了对比分析。我们利用闭护前的精细尺度捕捞压力数据，检验了鱼类在不同捕捞压力梯度下对保护措施的响应。 4. 鱼类体型对保护措施的响应强度与闭护前的捕捞压力呈正相关：相较于低捕捞压力区域的海洋保护区，高捕捞压力区域的海洋保护区在鱼类平均体长及体型分布上的响应更为显著。 5. 该响应在休闲垂钓重点目标物种中表现显著，但在非渔业目标物种中未观察到类似效应。 6. 综合与应用：区域闭护前的捕捞压力会影响海洋保护区的实施效能，在可获取相关数据的前提下，预测与评估海洋保护区运行成效时应将其纳入考量。在推行空间管理措施时，优先将受高强度捕捞的区域纳入保护范围，可最大化生态效益。