ABSTRACT: Changing environmental conditions are influencing the seasonal timing in life history events of organisms. Such shifts in phenology are often linked to increasing temperatures that stimulate faster developments or earlier arrivals. This phenomenon has been demonstrated in terrestrial and aquatic realms, but data and knowledge are limited on how early life stages of fish are affected over long-term and broad environmental scales. Here, we analyze 2 decades (1974-1996) of size class-specific Baltic herring Clupea harengus membras L. larval data along the whole coast of Finland to expose shifts in phenology linked to changes in environmental covariates. We use a novel Bayesian hierarchical spatio-temporal hurdle model that describes larval occurrence and abundance with separate processes. Abundances are modeled with the Ricker population growth model that enables us to predict size-specific larvae groups in relation to the environment while accounting for population density dependence. We quantify shifts in phenology at multiple life stages, based on first appearances of smallest larvae (<10 mm) and by detection of higher proportions of larger larvae (>15 mm) appearing earlier than they have done historically. Our results show a strong signal in shifting phenology of the larvae toward an earlier development of 7.7 d per decade. Increasing temperature had a positive effect on the earlier development of larger larvae. Additionally, we highlight that the survival of larvae becomes more density dependent as their size increases. Our modeling framework can reveal phenological shifts of early life stages in relation to environmental change for survey data that do not necessarily cover the onset of reproduction.

中文翻译：

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通过模拟气候对生命早期变化的影响，揭示鱼类幼虫的物候变化

摘要：不断变化的环境条件正在影响生物的生命史事件中的季节时机。物候学的这种变化通常与温度升高有关，从而刺激了更快的发育或更早的到来。这种现象已在陆地和水生领域得到证明，但有关鱼类的早期生命阶段如何在长期和广泛的环境范围内受到影响的数据和知识有限。在这里，我们分析了大小等级特定的波罗的海鲱Clupea harengus膜的2个十年（1974-1996年）芬兰整个沿海地区的L. larval幼虫数据揭示了与环境协变量变化相关的物候变化。我们使用一种新颖的贝叶斯分层时空跨栏模型，该模型描述了幼虫的出现和丰度，并具有独立的过程。使用里克（Ricker）种群增长模型对丰度进行建模，该模型使我们能够在考虑种群密度依赖性的同时，预测与环境相关的特定大小的幼体组。我们根据幼虫（<10毫米）的首次出现并检测出比历史上更早出现的更大比例的较大幼虫（> 15毫米）来量化在多个生命阶段的物候变化。我们的结果显示了一个强有力的信号，表明幼虫的物候向每十年7.7 d的早期发育转变。温度升高对较大幼体的早期发育有积极影响。此外，我们着重指出，随着幼体大小的增加，其存活率与密度的关系也越来越大。我们的建模框架可以揭示与数据变化（不一定涵盖繁殖开始）有关的环境变化相关的早期生命周期的物候变化。