Establishing the foundations for a sustainable use of deep-sea resources relies on increasing knowledge on this inaccessible ecosystem, which is challenging with traditional methods. The analysis of environmental DNA (eDNA) emerges as an alternative, but it has been scarcely applied to deep-sea fish. Here, we have analyzed the fish eDNA contained in oceanic vertical profile samples (up to 2000 m depth) collected throughout the continental slope of the Bay of Biscay. We detected 52 different fish species, of which 25 were classified as deep-sea fish. We found an increase of deep-sea fish richness and abundance with depth, and that eDNA reflects day–night community patterns and species-specific vertical distributions that are consistent with the known diel migratory behavior of many mesopelagic fishes. These findings highlight the potential of eDNA to improve knowledge on the fish species inhabiting the dark ocean before this still pristine ecosystem is further exploited.

中文翻译：

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公海环境 DNA 的垂直分层捕捉深海鱼类的生态模式和行为

为可持续利用深海资源奠定基础依赖于对这个难以接近的生态系统的更多了解，这对传统方法来说是一项挑战。环境 DNA (eDNA) 分析作为一种替代方法出现，但它几乎没有应用于深海鱼类。在这里，我们分析了在比斯开湾大陆坡收集的海洋垂直剖面样本（深度达 2000 米）中包含的鱼类 eDNA。我们检测到 52 种不同的鱼类，其中 25 种被归类为深海鱼。我们发现深海鱼类的丰富度和丰度随着深度的增加而增加，并且 eDNA 反映了昼夜群落模式和特定物种的垂直分布，这与许多中层鱼类已知的昼夜洄游行为一致。