ABSTRACT: Adult and juvenile myctophids feed at night in the epipelagic zone (<200 m) and are more dispersed in the mesopelagic zone (200-1000 m) during the daylight hours. In contrast, larvae inhabit the upper 200 m throughout a 24 h period and have daylight feeding patterns. Transforming stages occur both at the surface and in the mesopelagic zone and show less-defined feeding patterns. In this study, we analysed the trophic ecology of transforming and juvenile stages of 4 myctophids that occupy the neustonic layers (first 0-20 cm of the water column) during their nightly vertical migrations: Dasyscopelus asper, Gonichthys cocco, Myctophum affine, and M. nitidulum. Day and night neuston samples were collected across the equatorial and tropical Atlantic in April 2015. Transforming and juvenile stages occurred at night in the neuston, where they fed, but were absent from this layer during the day. The highest prey ingestion was observed between 01:00 and 04:00 h (UTC). Feeding incidence and the number of prey ingested increased from transformation stages to juvenile stages. Although the maximum prey size increased with fish body length, there was no significant increasing trend in mean prey sizes, but a great variability in the sizes of consumed prey. Diets of the 4 species mainly comprised a variety of copepod genera, usually dominated by Oncaea species. There was no evidence of resource partitioning among the 4 myctophid species. Estimates of daily feeding rations, based on the relationship between carbon content per gut and carbon content of fish body, throughout the night feeding period, showed that these species in these early stages ingested between 0.43 and 5.78% of their body carbon weight daily. We suggest that the occurrence and feeding of these early stages in the neuston may contribute to reducing trophic competition between migrating myctophids by space segregation.

中文翻译：

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迁移到新层的转化和幼小Myctophids的进食模式

摘要：成年和幼年的Myctophicids晚上在上层带（<200 m）觅食，白天白天则更多地分布在中弹性带（200-1000 m）中。相反，幼虫在整个24小时内栖息在上部200 m处，并具有日光喂养模式。转化阶段既发生在地表，也发生在近中生带，并显示出不太明确的进食模式。在这项研究中，我们分析了在夜间垂直迁移过程中占据中子层（水柱的第一个0-20厘米）的中子层的4个菌丝的转化和幼年期的营养生态：Dasyscopelus asper，Gonichthys cocco，Myctophum affine和M Nitidulum。2015年4月，白天和夜晚的神经元样本在赤道和热带大西洋上采集。晚上，在神经元进食并进入该阶段，但白天却不在此阶段。在01:00和04:00 h（UTC）之间观察到最高的猎物摄入量。从转化期到幼年期，摄食率和摄食猎物的数量增加。尽管最大猎物的大小随鱼体长度的增加而增加，但平均猎物的大小并没有明显的增加趋势，但是所消耗猎物的大小却有很大的变化。这4个物种的饮食主要包括多种of足类，通常以Oncaea为主种类。没有证据表明这4个食丝菌物种之间存在资源分配。根据整个夜间摄食期间每只肠的碳含量与鱼体碳含量之间的关系，对每日摄食配给量的估算表明，这些物种在这些早期阶段的日摄食量为它们体重的0.43％至5.78％。我们建议在神经元的这些早期阶段的发生和进食可能有助于减少通过空间隔离而迁移的Myctophids之间的营养竞争。