Historical patterns of the Eastern Baltic cod stock recruitment show a shift from a regime with high reproductive potential before the early 1980s to a regime with low reproductive potential since then. This shift can be attributed to increasingly unfavorable environmental conditions for cod reproduction at that time: critical salinity and oxygen levels, needed for successful egg and larval development, deteriorated. Yet, significant inflows of salt- and oxygen-rich water from the North Sea or improved eutrophication management might trigger a shift back to a more productive regime. Coupling a statistical recruitment model to a state-of-the-art, age-structured bio-economic model of the Eastern Baltic cod fishery, we study how optimal management depends on the uncertainty about the future productivity regime. We extend the predominantly theoretical literature on optimal management of a natural resource with a potential regime shift by analyzing an empirical model of age-structured population dynamics and by allowing for the possibility of a back-shift from a “bad” into a “good” regime. We find that with a higher probability of a shift back to the more productive regime the optimal management of the fishery becomes more conservative in the short run. We conclude that these benefits for the fishery warrant strong action reducing eutrophication to increase the probability of a regime shift back to high reproductive potential of the Eastern Baltic cod fishery.

中文翻译：

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渔业管理和临界点：在未来生产力机制不确定的情况下寻求波罗的海东部鳕鱼的最佳管理

波罗的海东部鳕鱼种群招募的历史模式显示，从 1980 年代初之前具有高繁殖潜力的制度转变为此后的低繁殖潜力制度。这种转变可归因于当时鳕鱼繁殖日益不利的环境条件：成功卵和幼虫发育所需的临界盐度和氧气水平恶化。然而，来自北海的大量富含盐分和富氧水的流入或改善的富营养化管理可能会引发向更具生产力的制度转变。将统计招募模型与波罗的海东部鳕鱼渔业的最先进的、年龄结构的生物经济模型相结合，我们研究了最佳管理如何取决于未来生产力制度的不确定性。我们通过分析年龄结构人口动态的经验模型并考虑从“坏”到“好”的反向转变的可能性，扩展了关于具有潜在政权转变的自然资源优化管理的主要理论文献政权。我们发现，随着回到生产力更高的制度的可能性更高，渔业的最佳管理在短期内变得更加保守。我们得出的结论是，渔业的这些好处需要采取强有力的行动来减少富营养化，以增加政权转向波罗的海东部鳕鱼渔业高繁殖潜力的可能性。