Diel vertical migration (DVM) is a common behavior among marine organisms to balance the trade-off between surface feeding opportunities and predation-related mortality risk. Body size is a master trait that impacts predation risk to both visual and nonvisual predators. Acoustic measurements from the autonomous Zooglider revealed size-dependent DVM behaviors in the San Diego Trough. Dual frequency (200 and 1000 kHz) backscatter, in conjunction with physical properties of the ambient water and optical imaging of zooplankton, were recorded during 12 Zooglider missions over 2 yr. Acoustic size-categories were identified based on the theoretical scattering properties of dominant taxonomic groups identified optically by the Zoocam. Acoustic modeling suggests that the measured acoustic backscatter in this region is largely dominated by copepods, with appreciable contributions from other taxa. We found that larger organisms migrated deeper (245–227 m) and faster (> 20 m h⁻¹) compared to smaller organisms (156 m, > 15 m h⁻¹). Larger organisms entered the upper layer of the water column later in the evening (0.2–1.5 h later) and descended into deeper water earlier in the morning (0.4–3.7 h earlier) than smaller-bodied organisms, consistent with body size-dependent visual predation risk. The variability in daytime depths occupied by small, intermediate, and large-bodied backscatterers was related to the depth of the euphotic zone, again consistent with light-dependent risk of predation.

中文翻译：

---

在圣地亚哥海槽中，中型浮游生物的体型和季节依赖性垂直迁移在声学上得到解决

Diel 垂直迁移 (DVM) 是海洋生物之间的一种常见行为，用于平衡地表摄食机会和与捕食相关的死亡风险之间的权衡。体型是影响视觉和非视觉捕食者捕食风险的主要特征。自主Zooglider的声学测量揭示了圣地亚哥海槽中依赖于尺寸的 DVM 行为。在 12 Zooglider期间记录了双频（200 和 1000 kHz）反向散射，以及环境水的物理特性和浮游动物的光学成像超过 2 年的任务。根据 Zoocam 光学识别的主要分类群的理论散射特性确定声学尺寸类别。声学模型表明，在该区域测量的声学反向散射主要由桡足类动物主导，其他类群也有明显贡献。我们发现，与较小的生物（156 m，> 15 m h ^-1）相比，较大的生物迁移得更深（245-227 m）和更快（> 20 m h ^-1）。与体型较小的生物相比，较大的生物在晚上晚些时候（0.2-1.5 小时后）进入水柱的上层，并在早上更早（0.4-3.7 小时）下降到更深的水中，这与依赖体型的视觉一致掠夺风险。小型、中型和大型后向散射体占据的白天深度的变化与透光区的深度有关，这再次与光依赖的捕食风险一致。