Proportionality between spawning stock biomass (SSB) and annual total egg production (TEP) has been an inherent assumption in spawner–recruitment models for fisheries management and studies on recruitment mechanisms in fish. However, recent evidence of density dependence in egg production has led to a need to reconsider the validity of recruitment per spawning stock biomass (RPS), which is a SSB-based survival index from hatching to recruitment, in recruitment studies. Here we revisit sardine recruitment hypotheses based on recruitment per egg production (RPE), which is a TEP-based survival index, by reanalyzing published data for the Pacific stock of Japanese sardine (Sardinops melanostictus) in the Kuroshio Current system at a multidecadal scale. By adopting RPE, we detected statistically significant relationships of the survival from hatching to recruitment to large-scale ocean climate anomaly, ambient temperature in the nursery grounds and growth rate during the early life stages. None of these relationships were detected by RPS. We propose the adoption of TEP-based survival indices rather than SSB-based ones in future studies on recruitment mechanisms of fish in relation to environmental and biological factors. Developing egg-production-based survival indices has the potential to improve understanding of recruitment mechanisms of fish under climate variability.

中文翻译：

---

重新审视沙丁鱼补充假设：基于产蛋的生存指数提高了对气候变化下鱼类补充机制的理解

产卵种群生物量 (SSB) 和年总产蛋量 (TEP) 之间的比例一直是渔业管理的产卵 - 招募模型和鱼类补充机制研究的固有假设。然而，最近关于产蛋量密度依赖性的证据导致需要重新考虑每个产卵种群生物量 (RPS) 的补充有效性，RPS 是补充研究中从孵化到补充的基于 SSB 的生存指数。在这里，我们通过重新分析日本沙丁鱼太平洋种群（Sardinops melanostictus) 在几十年尺度的黑潮系统中。通过采用 RPE，我们检测到从孵化到招募的存活率与大规模海洋气候异常、育苗场环境温度和早期生命阶段的生长速度之间的统计显着关系。RPS 没有检测到这些关系。我们建议在未来研究鱼类与环境和生物因素相关的招募机制时，采用基于 TEP 的生存指数而不是基于 SSB 的生存指数。开发基于产蛋的生存指数有可能提高对气候变化下鱼类补充机制的理解。