Programs to control predatory fishes have successfully increased the survival of imperiled prey fishes in some cases, but efficacy depends on the population dynamics and ecological interactions between the predators, prey, and the rest of the community. In California's Sacramento–San Joaquin Delta, extremely low survival of downstream‐migrating juvenile salmonids has been ascribed in part to predation by abundant nonnative fishes that have become naturalized in the system. This study aimed to determine the effectiveness of removing some of these predatory fish to increase the survival of juvenile salmonids in the San Joaquin River. In 2014 and 2015, we used predation event recorders (PERs) to estimate predation rates before and after localized, experimental predatory fish removals and additions. We also estimated survival of juvenile Chinook Salmon Oncorhynchus tshawytscha before and after predator manipulations in 2014 using acoustic tags. We found no statistically significant evidence for an effect of predator removals or additions on survival rates of Chinook Salmon (as measured by acoustic tags) or on predation rates (as measured by PERs), despite a one‐time reduction of approximately 40–70% of all predators from “removal” sites and relocation to “addition” sites. We review examples of successful predator control programs elsewhere, highlighting key differences between those programs and our study in the Sacramento–San Joaquin Delta.

中文翻译：

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主动清除管理捕食性鱼类种群的局限性

在某些情况下，控制掠食性鱼类的计划已成功提高了受威胁的猎物鱼类的存活率，但其效果取决于捕食者，猎物和社区其他成员之间的种群动态和生态相互作用。在加利福尼亚的萨克拉曼多-圣华金三角洲，下游迁移的幼鲑鱼的存活率极低，部分原因是该系统中已归化的大量非本地鱼类捕食。这项研究旨在确定去除其中一些捕食性鱼类以增加圣华金河幼鲑鱼的存活的有效性。在2014年和2015年，我们使用捕食事件记录器（PER）估算了本地化，实验性捕食性鱼类清除和添加前后的捕食率。2014年使用声学标签在捕食者操纵之前和之后的Oncorhynchus tshawytscha。尽管一次减少约40–70％，但我们发现没有捕食者去除或添加捕食者对奇努克鲑鱼存活率（通过声学标签测量）或捕食率（通过PERs测量）的影响的统计学上显着证据。从“转移”地点和迁移到“附加”地点的所有捕食者。我们回顾了其他地方成功的捕食者控制计划的示例，重点介绍了这些计划与我们在萨克拉曼多-圣华金河三角洲的研究之间的主要差异。