The lack of any abundant recruiting year class of Norwegian spring-spawning (NSS) herring between 2005 and 2015 contributed to an approximate reduction of 40% in the spawning-stock biomass since 2009, i.e. from 7 to 4 million tonnes. Warming of the North Atlantic is suggested to contribute to this reduction in recruitment. In the past, a warm phase induced by a positive Atlantic Multidecadal Oscillation (AMO) in the North Atlantic was positively correlated to the NSS herring stock size. Recent unprecedented ocean warming in the Norwegian Sea ecosystem, besides elevated temperatures due to a positive AMO, seems to be outside optimal environmental conditions for early life history stages of NSS herring. We analysed 28 years of survey data using generalized additive models to reconstruct environmental conditions for drifting yolksac and preflexion stage larvae. Our results indicate that strong recruitment years were more likely when the larvae occurred simultaneously with a negative AMO during positive temperature anomalies. The transition from yolksac stages towards preflexion stages occurred while there was a slow increase in water temperature during the larval drift. Weak recruitment years generally occurred when larvae experienced elevated temperatures during the life stage transition under a positive AMO. These results augment evidence that the historical positive relationship between AMO and stock dynamics is reversed between 1988 and 2015. Albeit not implying any specific mechanistic biological interactions, we can assume that the unprecedented warming has modified the ecosystem drivers that negatively affect drifting larvae. Since 2016, the North Atlantic is shifting into a negative AMO phase, possibly resulting in the 10-year recruitment suppression of NSS herring ending soon.

中文翻译：

---

环境对挪威春季产卵鲱鱼 ( Clupea harengus L.) 幼虫的影响揭示了近期招募成功的限制

2005 年至 2015 年间缺乏任何丰富的挪威春季产卵 (NSS) 鲱鱼招募年份类别，导致自 2009 年以来产卵种群生物量减少了约 40%，即从 7 至 400 万吨。北大西洋变暖被认为有助于减少招募。过去，北大西洋正大西洋多年代际振荡 (AMO) 引起的暖期与 NSS 鲱鱼种群规模呈正相关。挪威海生态系统最近前所未有的海洋变暖，除了正 AMO 导致的温度升高外，似乎超出了 NSS 鲱鱼早期生活史阶段的最佳环境条件。我们使用广义加性模型分析了 28 年的调查数据，以重建漂流卵黄囊和前屈阶段幼虫的环境条件。我们的结果表明，在正温度异常期间，当幼虫与负 AMO 同时发生时，更有可能出现强募集年份。从卵黄囊阶段到前屈阶段的转变发生在幼虫漂流过程中水温缓慢升高的时候。当幼虫在正 AMO 下的生命阶段过渡期间经历高温时，通常会出现弱募集年。这些结果进一步证明，AMO 与股票动态之间的历史正相关关系在 1988 年至 2015 年之间发生了逆转。 尽管并不意味着任何特定的机械生物相互作用，我们可以假设前所未有的变暖改变了对漂流幼虫产生负面影响的生态系统驱动因素。自 2016 年以来，北大西洋正在转变为负 AMO 阶段，可能导致 NSS 鲱鱼的 10 年招募抑制即将结束。