Green Stephanie J, Dulvy Nicholas K, Brooks Annabelle M L, Akins John L, Cooper Andrew B, Miller Skylar, Côté Isabelle M
Ecol Appl. 2014;24(6):1311-22. doi: 10.1890/13-0979.1.
Species invasions have a range of negative effects on recipient ecosystems, and many occur at a scale and magnitude that preclude complete eradication. When complete extirpation is unlikely with available management resources, an effective strategy may be to suppress invasive populations below levels predicted to cause undesirable ecological change. We illustrated this approach by developing and testing targets for the control of invasive Indo-Pacific lionfish (Pterois volitans and P. miles) on Western Atlantic coral reefs. We first developed a size-structured simulation model of predation by lionfish on native fish communities, which we used to predict threshold densities of lionfish beyond which native fish biomass should decline. We then tested our predictions by experimentally manipulating lionfish densities above or below reef-specific thresholds, and monitoring the consequences for native fish populations on 24 Bahamian patch reefs over 18 months. We found that reducing lionfish below predicted threshold densities effectively protected native fish community biomass from predation-induced declines. Reductions in density of 25–92%, depending on the reef, were required to suppress lionfish below levels predicted to overconsume prey. On reefs where lionfish were kept below threshold densities, native prey fish biomass increased by 50–70%. Gains in small (<6 cm) size classes of native fishes translated into lagged increases in larger size classes over time. The biomass of larger individuals (>15 cm total length), including ecologically important grazers and economically important fisheries species, had increased by 10–65% by the end of the experiment. Crucially, similar gains in prey fish biomass were realized on reefs subjected to partial and full removal of lionfish, but partial removals took 30% less time to implement. By contrast, the biomass of small native fishes declined by >50% on all reefs with lionfish densities exceeding reef-specific thresholds. Large inter-reef variation in the biomass of prey fishes at the outset of the study, which influences the threshold density of lionfish, means that we could not identify a single rule of thumb for guiding control efforts. However, our model provides a method for setting reef-specific targets for population control using local monitoring data. Our work is the first to demonstrate that for ongoing invasions, suppressing invaders below densities that cause environmental harm can have a similar effect, in terms of protecting the native ecosystem on a local scale, to achieving complete eradication.
物种入侵对受纳生态系统有一系列负面影响，而且许多入侵发生的规模和程度使得完全根除不太可能实现。当利用现有的管理资源不太可能完全消灭入侵物种时，一种有效的策略可能是将入侵种群数量控制在预计会导致不良生态变化的水平以下。我们通过制定和测试控制西大西洋珊瑚礁上入侵的印度-太平洋狮子鱼（褐拟鱗魨和黑斑拟鱗魨）的目标，阐述了这种方法。我们首先建立了一个狮子鱼对本地鱼类群落捕食的体型结构模拟模型，并用它来预测狮子鱼的阈值密度，超过这个密度本地鱼类生物量就会下降。然后，我们通过在特定珊瑚礁阈值之上或之下对狮子鱼密度进行实验性操控，并在18个月内监测巴哈马24个斑块珊瑚礁上本地鱼类种群的变化情况，来检验我们的预测。我们发现，将狮子鱼数量减少到预测的阈值密度以下，能有效保护本地鱼类群落生物量，使其免受捕食导致的下降影响。根据珊瑚礁的不同情况，需要将狮子鱼密度降低25%至92%，才能将其数量控制在预计会过度消耗猎物的水平以下。在狮子鱼数量保持在阈值密度以下的珊瑚礁上，本地猎物鱼的生物量增加了50%至70%。随着时间推移，小型（<6厘米）本地鱼类数量的增加导致大型鱼类数量的滞后增加。到实验结束时，包括具有重要生态意义的食草鱼类和具有重要经济意义的渔业物种在内的大型个体（全长>15厘米）的生物量增加了10%至65%。至关重要的是，在部分和全部清除狮子鱼的珊瑚礁上，猎物鱼生物量都有类似的增加，但部分清除所需的时间少30%。相比之下，在所有狮子鱼密度超过特定珊瑚礁阈值的珊瑚礁上，小型本地鱼类的生物量下降超过50%。研究开始时猎物鱼生物量在不同珊瑚礁之间存在很大差异，这影响了狮子鱼的阈值密度，这意味着我们无法确定一个通用的经验法则来指导控制工作。然而，我们的模型提供了一种利用当地监测数据为种群控制设定特定珊瑚礁目标的方法。我们的工作首次证明，对于正在进行的入侵，将入侵者数量控制在会造成环境危害的密度以下，在保护当地原生生态系统方面，可能会产生与完全根除类似的效果。
