School of Mathematics and Statistics, University of Canterbury, Christchurch 8140, New Zealand; Te Pūnaha Matatini, a New Zealand Centre of Research Excellence, Auckland, New Zealand.
School of Mathematics and Statistics, University of Canterbury, Christchurch 8140, New Zealand; Te Pūnaha Matatini, a New Zealand Centre of Research Excellence, Auckland, New Zealand.
Math Biosci. 2019 Oct;316:108245. doi: 10.1016/j.mbs.2019.108245. Epub 2019 Aug 30.
Fisheries management strategies in which large fish are selectively targeted and younger, smaller fish are protected can lead to disruption of stocks, truncation of the population size spectrum, and impaired recruitment. Balanced harvesting is an alternative approach, which distributes fishing mortality across a wide range of species and sizes in proportion to their natural productivity. Here, we investigate outcomes from an agent-based model of fishing, coupled with an ecological model for the dynamics of a single fish species in a small-scale fishery. In the model, individual fishing agents make decisions about whether to enter or exit the fishery, and what size fish to target, based on economic calculations about short-term profitability of alternative actions. Fishing mortality, aggregated across agents, affects the biomass and size structure of the stock, which in turn affects individual agents' yields, creating a feedback loop. We show that the autonomous fishing agents self-organise to produce a Nash equilibrium, in which yields are equalised across agents. The aggregate fishing mortality that emerges in this equilibrium state is closely aligned with the distribution of productivity across body size. We conclude that balanced harvesting is an emergent outcome of the model. This occurs despite the absence of any externally imposed regulations on total fishing effort, catch or target sizes. However, controls on overall harvesting pressure are required to avoid overfishing.
渔业管理策略中，大鱼被有选择性地捕捞，而小鱼则受到保护，这可能导致种群的破坏、种群规模谱的截断以及繁殖能力受损。平衡捕捞是一种替代方法，它根据物种的自然生产力，将捕捞死亡率分配到广泛的物种和大小范围。在这里，我们研究了一个基于代理的捕捞模型与一个小规模渔业中单一鱼类动态的生态模型相结合的结果。在模型中，个体捕捞者根据替代行动的短期盈利能力进行经济计算，决定是否进入或退出渔业以及捕捞何种大小的鱼类。捕捞死亡率在代理之间聚合，影响种群的生物量和大小结构，进而影响个体代理的产量，形成反馈循环。我们表明，自主捕捞代理自组织形成纳什均衡，其中各代理的产量均等化。在这个均衡状态下出现的总捕捞死亡率与身体大小的生产力分布密切一致。我们得出的结论是，平衡捕捞是模型的一个突现结果。尽管没有对总捕捞努力、捕捞量或目标大小施加任何外部规定，但这种情况仍然存在。然而，需要控制整体捕捞压力，以避免过度捕捞。
