Natural resources often exhibit large interannual fluctuations in productivity driven by shifting environmental conditions, and this translates to high variability in the revenue resource users earn. However, users can dampen this variability by harvesting a portfolio of resources. In the context of fisheries, this means targeting multiple populations, though the ability to actually build diverse fishing portfolios is often constrained by the costs and availability of fishing permits. These constraints are generally intended to prevent overcapitalization of the fleet and ensure populations are fished sustainably. As linked human-natural systems, both ecological and fishing dynamics influence the specific advantages and disadvantages of increasing the diversity of fishing portfolios. Specifically, a portfolio of synchronous populations with similar responses to environmental drivers should reduce revenue variability less than a portfolio of asynchronous populations with opposite responses. We built a bioeconomic model based on the Dungeness crab (Metacarcinus magister), Chinook salmon (Oncorhynchus tshawytscha), and groundfish fisheries in the California Current, and used it to explore the influence of population synchrony and permit access on income patterns. As expected, synchronous populations reduced revenue variability less than asynchronous populations, but only for portfolios including crab and salmon. Synchrony with the longer-lived groundfish population was not important because environmentally driven changes in groundfish recruitment were mediated by growth and natural mortality over the full population age structure, and overall biomass was relatively stable across years. Thus, building a portfolio of diverse life histories can buffer against the impacts of poor environmental conditions over short time scales. Increasing access to all permits generally led to increased revenue stability and decreased inequality of the fleet, but also resulted in less revenue earned by an individual from a given portfolio because more vessels shared the available biomass. This means managers are faced with a trade-off between the average revenue individuals earn and the risk those individuals accept. These results illustrate the importance of considering connections between social and ecological dynamics when evaluating management options that constrain or facilitate fishers’ ability to diversify their fishing.

中文翻译：

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人口同步性、生活史和获取限制对渔业投资组合收益的影响

由于环境条件的变化，自然资源通常表现出较大的年际生产力波动，这转化为用户赚取的收入资源的高度可变性。但是，用户可以通过收集资源组合来抑制这种可变性。在渔业的背景下，这意味着针对多个种群，尽管实际建立多样化捕捞组合的能力通常受到捕捞许可证的成本和可用性的限制。这些限制通常旨在防止船队资本过剩并确保可持续捕捞种群。作为相互关联的人类-自然系统，生态和捕捞动态都会影响增加捕捞组合多样性的具体优势和劣势。具体来说，对环境驱动因素具有相似反应的同步种群组合应该比具有相反反应的异步种群组合减少收入变异性。我们建立了一个基于 Dungeness 蟹的生物经济模型（Metacarcinus magister ), 奇努克鲑鱼 ( Oncorhynchus tshawytscha) 和加利福尼亚洋流中的底层鱼类渔业，并用它来探索人口同步和许可获取对收入模式的影响。正如预期的那样，同步种群减少的收入变异性低于非同步种群，但仅适用于包括螃蟹和鲑鱼在内的投资组合。与寿命较长的底层鱼类种群的同步并不重要，因为在整个种群年龄结构中，由环境驱动的底层鱼类补充变化是由生长和自然死亡率介导的，并且总体生物量在各年间相对稳定。因此，构建多样化生活史的组合可以在短时间内缓冲恶劣环境条件的影响。增加获得所有许可证的机会通常会增加收入稳定性并减少车队的不平等，但也导致个人从给定投资组合中获得的收入减少，因为更多的船只共享可用的生物质。这意味着管理者面临着个人赚取的平均收入和个人接受的风险之间的权衡。这些结果说明了在评估限制或促进渔民多样化捕捞能力的管理方案时考虑社会和生态动态之间的联系的重要性。