Overwinter environmental conditions are a major driver of larval survival, recruitment, and reproductive pre-conditioning in Antarctic krill (Euphausia superba). Few winter studies exist from which to infer impacts of changing environmental conditions on the biology of krill. Here demographic and maturity patterns of krill during five winters are examined at an overwintering hotspot in the northern Antarctic Peninsula. Two different recruitment pulses were present over the 5 years of the study. A large recruitment event was evident in winter 2012, followed by cohort growth tracked through winter 2014. A recruitment event also occurred in 2015, despite lower abundance of larvae in 2013 and 2014. The recruitment pulse in 2015 was correlated with the intrusion of high salinity water, characteristic of the Weddell Sea, during a positive El Niño–Southern Oscillation phase, suggesting recruitment was driven by advection of recruits into the northern Antarctic Peninsula. Despite the inter-annual environmental variability, most female krill were in resting reproductive stages in all years. The lack of variability in female reproductive status during winter may impose a developmental constraint to earlier spawning than previously considered; the time necessary to advance from resting stages to reproductive maturity may limit the ability of krill to adapt to trends in the timing and magnitude of the spring bloom. The observed patterns of recruitment and variation in maturity stages highlight the complexity of krill population dynamics and should be considered when projecting population responses of Antarctic krill to climate-driven changes in the Southern Ocean.

中文翻译：

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越冬热点南极磷虾（Euphausia superba）的人口统计和成熟模式

越冬环境条件是南极磷虾 (Euphausia superba) 幼虫存活、募集和繁殖预处理的主要驱动力。很少有冬季研究可以推断环境条件变化对磷虾生物学的影响。这里在南极半岛北部的一个越冬热点检查了五个冬季期间磷虾的人口统计和成熟模式。在 5 年的研究中存在两种不同的募集脉冲。2012 年冬季明显发生了大规模的招募事件，随后是 2014 年冬季的队列增长。2015 年也发生了一次招募事件，尽管 2013 年和 2014 年幼虫的丰度较低。2015 年的招募脉冲与高盐度的入侵相关水，威德尔海的特征，在正厄尔尼诺-南方涛动阶段，表明招募是由新兵进入南极半岛北部的平流驱动的。尽管环境存在年际变化，但大多数雌性磷虾在所有年份都处于休眠繁殖阶段。冬季雌性生殖状态缺乏可变性，这可能会限制比以前认为的更早产卵；从休眠阶段到生殖成熟所需的时间可能会限制磷虾适应春季开花时间和规模趋势的能力。观察到的成熟阶段补充和变化模式突出了磷虾种群动态的复杂性，在预测南极磷虾对南大洋气候驱动变化的种群响应时应予以考虑。