Dipartimento di Bioscienze, Università degli Studi di Parma, viale Usberti 11/A, 43100, Parma, Italy.
INRA, UR1115 PSH, 84914, Avignon, France.
Glob Chang Biol. 2015 Sep;21(9):3323-35. doi: 10.1111/gcb.12972. Epub 2015 Jun 27.
The global European eel (Anguilla anguilla) stock is critically endangered according to the IUCN, and the European Commission has urged the development of conservation plans aimed to ensure its viability. However, the complex life cycle of this panmictic species, which reproduces in the open ocean but spends most of its prereproductive life in continental waters (thus embracing a huge geographic range and a variety of habitat types), makes it difficult to assess the long-term effectiveness of conservation measures. The interplay between local and global stressors raises intriguing cross-scale conservation challenges that require a comprehensive modelling approach to be addressed. We developed a full life cycle model of the global European eel stock, encompassing both the oceanic and the continental phases of eel's life, and explicitly allowing for spatial heterogeneity in vital rates, availability of suitable habitat and settlement potential via a metapopulation approach. We calibrated the model against a long-term time series of global European eel catches and used it to hindcast the dynamics of the stock in the past and project it over the 21st century under different management scenarios. Although our analysis relies on a number of inevitable simplifying assumptions and on data that may not embrace the whole range of variation in population dynamics at the small spatiotemporal scale, our hindcast is consistent with the general pattern of decline of the stock over recent decades. The results of our projections suggest that (i) habitat loss played a major role in the European eel decline; (ii) the viability of the global stock is at risk if appropriate protection measures are not implemented; (iii) the recovery of spawner escapement requires that fishing mortality is significantly reduced; and (iv) the recovery of recruitment might not be feasible if reproductive output is not enhanced.
根据世界自然保护联盟（IUCN）的评估，欧洲鳗（Anguilla anguilla）的全球种群已处于极度濒危状态，欧盟委员会已敦促制定保护计划，以确保其生存能力。然而，由于该洄游性物种的生命周期复杂，其在公海繁殖，但大部分幼鱼期生活在大陆水域（因此涵盖了巨大的地理范围和多种生境类型），这使得评估保护措施的长期有效性变得困难。地方和全球压力因素的相互作用带来了有趣的跨尺度保护挑战，需要采用综合建模方法来解决。我们开发了一个全球欧洲鳗种群的全生命周期模型，涵盖了鳗的海洋和大陆阶段，并通过泛种群方法明确允许关键生活率、适宜生境的可用性和定居潜力存在空间异质性。我们根据全球欧洲鳗长期时间序列的捕捞数据对模型进行了校准，并利用该模型回溯过去该种群的动态，并在不同管理情景下预测其在 21 世纪的动态。尽管我们的分析依赖于一些不可避免的简化假设，并且依赖的数据可能不包括在小时空尺度上种群动态的全部变化范围，但我们的回溯结果与该种群在过去几十年中下降的总体模式一致。我们的预测结果表明：（i）生境丧失是欧洲鳗种群减少的主要原因；（ii）如果不采取适当的保护措施，全球种群的生存能力将受到威胁；（iii）如果不显著降低捕捞死亡率，产卵洄游的恢复是不可能的；（iv）如果生殖输出没有提高，那么补充群体的恢复可能不可行。
