Assessment of total egg production as a proxy for reproductive potential is critical for understanding the mechanisms of recruitment variability and implementing appropriate stock management. This study determined whether the temporal variation in the estimated egg production index (EPI) of spawning western sand lance (Ammodytes japonicus) collected in the Bisan Strait in the central Seto Inland Sea in Japan explains its recruitment variability from 2009 to 2019. Although the maturation rates of individuals aged 1 year varied among sampling years, they were positively correlated with mean standard length at aestivation onset in summer. The negative relationship between the mean standard length and density of aestivating young-of-the-year fish at aestivation onset suggests that growth was dependent on density during the spring foraging period. All specimens aged 2 and 3 years were mature, and relative fecundity was significantly higher than that in specimens aged 1 year. The EPI of spawning individuals was markedly reduced in recent years and was associated with the decreased density of fish aged 2 and 3 years. In addition, the number of recruit fish was significantly associated with the EPI of spawning fish. However, the density of spawning fish in winter did not adequately explain the variation in recruitment. Thus, our findings suggest that sand lance aged 1 year have reduced reproductive potential, and that the causes of the recent decline in sand lance stocks might be partly attributable to a decline in the abundance of older fish.

评估总卵产量作为繁殖潜力的代名词，对于理解募集变异性的机制和实施适当的种群管理至关重要。这项研究确定产卵的西部沙枪（Ammodytes japonicus）产卵量估计指数（EPI）的时间变化是否）收集于日本濑户内海中部的比桑海峡，说明了2009年至2019年的募集变异性。尽管1岁年龄段的个体的成熟率在采样年之间有所不同，但它们与夏季成年开始时的平均标准长度呈正相关。平均标准长度与开始吸水的年幼鱼密度之间的负相关关系表明，春季觅食期间的生长取决于密度。所有年龄为2和3岁的标本均已成熟，相对生育力明显高于年龄为1岁的标本。产卵个体的EPI近年来显着降低，并且与2岁和3岁鱼的密度降低有关。此外，新生鱼的数量与产卵鱼的EPI显着相关。但是，冬季产卵鱼的密度不足以解释补充量的变化。因此，我们的发现表明，一年龄的沙矛鱼繁殖潜力降低，而近期沙矛鱼种群下降的原因可能部分归因于老鱼数量的减少。