Center for Earth System Research and Sustainability (CEN), Institute of Marine Ecosystem and Fisheries Science (IMF), University of Hamburg, 22767, Hamburg, Germany.
Department of Biology, University of Padova, Via Bassi, 35100, Padova, Italy.
Sci Rep. 2023 Jan 6;13(1):289. doi: 10.1038/s41598-022-27104-y.
Recovery of depleted fish stocks is an important goal for fisheries management and crucial to sustain important ecosystem functions as well as global food security. Successful recovery requires adjusting fishing mortality to stock productivity but can be prevented or inhibited by additional anthropogenic impacts such as climate change. Despite management measures to recover fish stocks being in place in legislations such as the European Union´s Common Fisheries Policy (CFP), recovery can be hindered by the occurrence of regime shift dynamics. Such non-linear discontinuous dynamics imply tipping points and bear the characteristics of abrupt change, hysteresis and non-stationary functional relationships. We here used the recent reform of the CFP as a natural experiment to investigate the existence of regime shift dynamics and its potential effects on the recovery potential on six strongly fished or even depleted commercial fish stocks in the North Sea. Using a set of statistical approaches we show that regime shift dynamics exist in all six fish stocks as a response to changes in fishing pressure and temperature. Our results furthermore demonstrate the context-dependence of such dynamics and hence the ability of management measures to rebuild depleted fish stocks, leading to either failed recovery or positive tipping.
恢复枯竭的鱼类种群是渔业管理的一个重要目标，对维持重要的生态系统功能和全球粮食安全至关重要。成功的恢复需要将捕捞死亡率调整到种群生产力，但气候变化等额外的人为影响可能会阻止或抑制这种恢复。尽管在欧盟共同渔业政策（CFP）等法规中已经采取了管理措施来恢复鱼类种群，但由于出现了制度转变动态，恢复可能会受到阻碍。这种非线性不连续的动态意味着存在临界点，并具有突然变化、滞后和非稳态功能关系的特征。我们在这里利用 CFP 的最近改革作为自然实验，调查了制度转变动态的存在及其对北海六个过度捕捞甚至枯竭的商业鱼类种群的恢复潜力的潜在影响。我们使用了一组统计方法，结果表明，所有六个鱼类种群都存在制度转变动态，这是对捕捞压力和温度变化的反应。我们的研究结果还表明，这种动态存在着情境依赖性，因此管理措施有能力重建枯竭的鱼类种群，从而导致恢复失败或出现积极的临界点。
