Larger and older fish contribute disproportionately to spawning and play an important role in the replenishment of exploited stocks. Fishing often removes specific size- and age-classes, with direct impacts on stock productivity and population resilience. Despite this, fisheries advice is commonly based on estimates of spawning stock biomass (SSB) and fishing mortality (F) and makes little reference to the importance of size and/or age structure. Consequently, there is a need for indicators of size and/or age structure to better inform fisheries management and help assess global sustainability goals. Here, we introduce a new age-based indicator ABI_MSY that monitors age structure relative to the equilibrium age structure at F_MSY. We apply this new indicator to 72 commercially important stocks in the Northeast Atlantic, covering 26 species, which collectively contributed 86% of all commercial catches in the region in 2019. We estimate that 62% (45 stocks) currently have proportionally fewer older fish relative to F_MSY conditions, whereas 38% (27 stocks) have proportionally more older fish; we also note patterns with respect to geographic area and taxonomic family. Simulation testing demonstrated that ABI_MSY is responsive to overfishing and generally tracks (with high sensitivity and specificity) a common measure of stock depletion, SSB relative to B_MSY. Throughout, we show that ABI_MSY provides information on the age structure of exploited stocks that is complementary to conventional reference points for SSB and F. Further, the framework used to estimate ABI_MSY make it well placed for integration into current advisory frameworks on fisheries management.

中文翻译：

---

将较老的鱼类纳入渔业管理：针对开发鱼类资源的新的基于年龄的指标和参考点

较大和较老的鱼类对产卵的贡献不成比例，并在补充被开发的种群方面发挥着重要作用。捕捞往往会消除特定体型和年龄级别的动物，对种群生产力和种群恢复力产生直接影响。尽管如此，渔业建议通常基于产卵种群生物量（SSB）和捕捞死亡率（F）的估计，很少提及大小和/或年龄结构的重要性。因此，需要制定规模和/或年龄结构指标，以便更好地为渔业管理提供信息并帮助评估全球可持续性目标。在这里，我们引入了一个新的基于年龄的指标 ABI _MSY，该指标监控相对于F _MSY的均衡年龄结构的年龄结构。我们将这一新指标应用于东北大西洋的 72 个具有重要商业价值的种群，涵盖 26 个物种，这些种群合计占该地区 2019 年所有商业渔获量的 86%。我们估计，目前 62%（45 个种群）的老鱼相对较少至F _MSY条件，而 38%（27 个鱼群）的年龄较大的鱼比例较高；我们还注意到地理区域和分类科的模式。模拟测试表明，ABI _MSY对过度捕捞有反应，并且通常跟踪（具有高灵敏度和特异性）种群枯竭的常见衡量标准，即相对于B _MSY的 SSB 。在整个过程中，我们表明 ABI _MSY提供了有关已开发种群的年龄结构的信息，该信息是对 SSB 和F的传统参考点的补充。_{此外，用于估算 ABI MSY 的}框架使其能够很好地融入当前的渔业管理咨询框架。