Abstract Growth is an important factor that regulates survival during early life stages, and growth rates and recruitment are often thought to be positively related. However, environmental conditions generally fluctuate over time, which could lead to temporal changes in growth–recruitment relationships. Here, we investigate whether growth–recruitment relationships are time-varying by applying dynamic linear models, which allow coefficients to vary over time, to a 23-yr data set of recruitment and early life-stage growth rate in Japanese sardine Sardinops melanostictus. We found that the impact of growth rate on recruitment (i.e., the slope coefficient) was relatively high during the late 1990s, then gradually weakened, and has remained low in recent years. The baseline recruitment level (i.e., the intercept) also shifted over time, being relatively low in the late 1990s, gradually increasing, and remaining high in recent years. Furthermore, a model with time-varying intercept and slope was more statistically plausible than models with constant coefficients. These results indicate that the growth–recruitment relationship varied dynamically over time. Our findings highlight the need to consider the possibility of time-varying growth–recruitment relationships when investigating such relationships and predicting recruitment.

中文翻译：

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日本沙丁鱼早期生长率与招募的时变关系

摘要 生长是在生命早期阶段调节生存的重要因素，生长速率和招募通常被认为是正相关的。然而，环境条件通常会随着时间的推移而波动，这可能会导致增长 - 招聘关系的时间变化。在这里，我们通过将允许系数随时间变化的动态线性模型应用于日本沙丁鱼沙丁鱼的招募和早期生命阶段增长率的 23 年数据集来研究增长 - 招募关系是否随时间变化。我们发现，增长率对招聘的影响（即斜率系数）在 1990 年代后期相对较高，然后逐渐减弱，近年来一直处于较低水平。基线招募水平（即截距）也随时间变化，在 1990 年代后期相对较低，逐渐增加，并在最近几年保持高位。此外，具有时变截距和斜率的模型比具有恒定系数的模型在统计上更合理。这些结果表明，增长-招聘关系随时间动态变化。我们的发现强调了在调查这种关系和预测招聘时需要考虑随时间变化的增长-招聘关系的可能性。