Data from: Balancing yield with resilience and conservation objectives in harvested predator-prey communities

The global overexploitation of fish stocks is endangering many marine food webs. Scientists and managers now call for an ecosystem-based fisheries management, able to take into account the complexity of marine ecosystems and the multiple ecosystem services they provide. By contrast, many fishery management plans only focus on maximizing the productivity of harvested stocks. Such practices are suggested to affect other ecosystem services, altering the integrity and resilience of natural communities. Here we show that while yield-maximizing policies can allow for coexistence and resilience in predator-prey communities, they are not optimal in a multi-objective context. We find that although total prey and predator maximum yields are higher with a prey-oriented harvest, focusing on the predator improves species coexistence. Also, moderate harvesting of the predator can enhance resilience. Furthermore, increasing maximum yields by changing catchabilities improves resilience in predator-oriented systems, but reduces it in prey-oriented systems. In a multi-objective context, optimal harvesting strategies involve a general trade-off between yield and resilience. Resilience-maximizing strategies are however compatible with quite high yields, and should often be favored. Our results further suggest that balancing harvest between trophic levels is often best at maintaining simultaneously species coexistence, resilience and yield.

全球范围内对鱼类种群的过度捕捞，正威胁着众多海洋食物网的存续。当前，科学家与渔业管理者呼吁推行基于生态系统的渔业管理（Ecosystem-based Fisheries Management），该框架需充分考量海洋生态系统的复杂性及其所提供的多项生态系统服务功能。与之形成鲜明对比的是，多数现行渔业管理方案仅聚焦于最大化捕捞种群的生产力。此类捕捞模式或会对其他生态系统服务造成干扰，进而破坏自然群落的结构完整性与恢复力（Resilience）。本研究表明，尽管以产量最大化为目标的捕捞政策可维持捕食者-猎物群落（Predator-Prey Communities）的物种共存与恢复力，但在多目标情境下，此类政策并非最优选择。研究发现，尽管以猎物为核心的捕捞模式可获得更高的猎物与捕食者总最大产量，但聚焦捕食者的捕捞策略更利于物种共存。此外，对捕食者实施适度捕捞，还可提升群落恢复力。此外，通过调整可捕性（Catchabilities）来提升最大产量的做法，在以捕食者为核心的捕捞系统中可提升恢复力，但在以猎物为核心的系统中则会降低恢复力。在多目标情境下，最优捕捞策略通常需要在产量与恢复力之间进行权衡。然而，以恢复力最大化为目标的捕捞策略，可与较高产量兼容，因此通常更值得推广采用。本研究结果进一步表明，在不同营养级（Trophic Levels）之间均衡分配捕捞强度，往往是同时维持物种共存、群落恢复力与捕捞产量的最优方案。