Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, Devon, United Kingdom.
British Antarctic Survey, High Cross, Cambridge, United Kingdom.
PLoS One. 2019 Jul 24;14(7):e0219325. doi: 10.1371/journal.pone.0219325. eCollection 2019.
Antarctic krill, Euphausia superba, have a circumpolar distribution but are concentrated within the south-west Atlantic sector, where they support a unique food web and a commercial fishery. Within this sector, our first goal was to produce quantitative distribution maps of all six ontogenetic life stages of krill (eggs, nauplii plus metanauplii, calyptopes, furcilia, juveniles, and adults), based on a compilation of all available post 1970s data. Using these maps, we then examined firstly whether "hotspots" of egg production and early stage nursery occurred, and secondly whether the available habitat was partitioned between the successive life stages during the austral summer and autumn, when krill densities can be high. To address these questions, we compiled larval krill density records and extracted data spanning 41 years (1976-2016) from the existing KRILLBASE-abundance and KRILLBASE-length-frequency databases. Although adult males and females of spawning age were widely distributed, the distribution of eggs, nauplii and metanauplii indicates that spawning is most intense over the shelf and shelf slope. This contrasts with the distributions of calyptope and furcilia larvae, which were concentrated further offshore, mainly in the Southern Scotia Sea. Juveniles, however, were strongly concentrated over shelves along the Scotia Arc. Simple environmental analyses based on water depth and mean water temperature suggest that krill associate with different habitats over the course of their life cycle. From the early to late part of the austral season, juvenile distribution moves from ocean to shelf, opposite in direction to that for adults. Such habitat partitioning may reduce intraspecific competition for food, which has been suggested to occur when densities are exceptionally high during years of strong recruitment. It also prevents any potential cannibalism by adults on younger stages. Understanding the location of krill spawning and juvenile development in relation to potentially overlapping fishing activities is needed to protect the health of the south-west Atlantic sector ecosystem.
南极磷虾，Euphausia superba，具有环极分布，但集中在西南大西洋扇区，在那里它们支持独特的食物网和商业渔业。在这个扇区，我们的第一个目标是根据所有 20 世纪 70 年代后的数据编制南极磷虾所有六个生活史阶段（卵、无节幼体加溞状幼体、幼体、刚毛、幼虾和成虾）的定量分布图。使用这些地图，我们首先检查了卵产量和早期育幼地“热点”是否存在，其次检查了在南极夏季和秋季（磷虾密度可能很高）期间，连续的生活阶段之间是否存在可用栖息地的划分。为了解决这些问题，我们编制了幼虾密度记录，并从现有的 KRILLBASE 丰度和 KRILLBASE 长度频率数据库中提取了跨越 41 年（1976-2016 年）的数据。虽然有生殖能力的成年雄性和雌性分布广泛，但卵、无节幼体和溞状幼体的分布表明，在陆架和陆架坡上的繁殖最为强烈。这与 calyptope 和刚毛幼体的分布形成对比，后者集中在更偏远的外海，主要在南斯科舍海。然而，幼虾主要集中在斯科舍弧形大陆架上的大陆架上。基于水深和平均水温的简单环境分析表明，磷虾在其生命周期中与不同的栖息地相关联。在南极季节的早期到后期，幼虾的分布从海洋向大陆架移动，与成年虾的方向相反。这种栖息地的划分可能减少了食物竞争，在强繁殖年份密度异常高时，这种竞争可能会发生。它还可以防止成年虾对年轻阶段的任何潜在捕食。为了保护西南大西洋扇区生态系统的健康，需要了解磷虾产卵和幼虾发育与潜在重叠捕捞活动的关系。
