The marine ecosystem off British Columbia (BC), Canada, has experienced various changes in the last two decades, including reduced lipid-rich zooplankton biomass, increased marine mammals, and deteriorated commercial fisheries, particularly those targeting pelagic species such as Pacific Herring (Clupea pallasii). Understanding how stressors interactively and cumulatively affect commercially important fish species is key to moving toward ecosystem-based fisheries management. Because it is challenging to assess the cumulative effects of multiple stressors by using empirical data alone, a dynamic, individual-based spatially explicit ecosystem modeling platform such as Object-oriented Simulator of Marine Ecosystems (OSMOSE) represents a valuable tool to simulate ecological processes and comprehensively evaluate how stressors cumulatively impact modeled species. In this study, we employed OSMOSE to investigate the cumulative effects of fishing, plankton biomass change, and marine mammal consumption on the dynamics of some fish species and the BC marine ecosystem as a whole. We specifically simulated ecosystem dynamics during the last 20 years under two sets of scenarios: (1) unfavorable conditions from the perspective of commercial fish species (i.e., doubling fishing mortality rates, halving plankton biomass, and doubling marine mammal biomass, acting individually or collectively); and (2) favorable conditions with the three factors having opposite changes (i.e., halving fishing mortality rates, doubling plankton biomass, and halving marine mammal biomass, acting individually or collectively). Our results indicate that, under unfavorable conditions, the degree to which species biomass was reduced varied among species, and that negative synergistic and negative dampened effects were dominant under historical and doubled fishing mortality rates, respectively. Under favorable conditions, species biomasses did not increase as much as expected due to the existence of complex predator-prey interactions among fish species, and positive synergistic and positive dampened effects were prevailing under historical and halved fishing mortality rates, respectively. The ecosystem total biomass and the biomass to fisheries yield ratio were found to be good ecological indicators to represent ecosystem changes and track the impacts from the multiple drivers of change. Our research provides insights on how fisheries management should adapt to prepare for potential future impacts of climate change.

中文翻译：

---

海洋生态系统中捕鱼、浮游生物生产力和海洋哺乳动物消费的累积效应

加拿大不列颠哥伦比亚省 (BC) 附近的海洋生态系统在过去 20 年中经历了各种变化，包括富含脂质的浮游动物生物量减少、海洋哺乳动物增加和商业渔业恶化，尤其是那些以太平洋鲱鱼 (Clupea帕拉西）。了解压力源如何相互作用和累积地影响具有重要商业价值的鱼类物种是转向基于生态系统的渔业管理的关键。因为单独使用经验数据来评估多个压力源的累积影响是具有挑战性的，所以动态的、基于个体的空间显性生态系统建模平台，例如面向对象的海洋生态系统模拟器 (OSMOSE) 是模拟生态过程和综合评估压力源如何累积影响模型物种的宝贵工具。在这项研究中，我们使用 OSMOSE 来研究捕鱼、浮游生物生物量变化和海洋哺乳动物消费对某些鱼类和整个 BC 海洋生态系统动态的累积影响。我们在两组情景下专门模拟了过去 20 年的生态系统动态：（1）从商业鱼类的角度来看不利条件（即捕捞死亡率加倍，浮游生物生物量减半，海洋哺乳动物生物量加倍，单独或集体行动); (2) 三个因素有相反变化的有利条件（即捕捞死亡率减半、浮游生物生物量加倍、海洋哺乳动物生物量减半，单独或共同作用）。我们的结果表明，在不利条件下，物种生物量减少的程度因物种而异，负协同效应和负抑制效应分别在历史捕捞死亡率和翻倍的捕捞死亡率下占主导地位。在有利条件下，由于鱼类之间存在复杂的捕食者 - 猎物相互作用，物种生物量没有像预期的那样增加，并且在历史和减半的捕捞死亡率下分别存在积极的协同和积极的抑制效应。发现生态系统总生物量和生物量与渔业产量之比是很好的生态指标，可以代表生态系统变化并跟踪变化的多重驱动因素的影响。我们的研究提供了有关渔业管理应如何适应以应对未来气候变化的潜在影响的见解。