Despite expanding in-situ observations of marine ecosystems by new-generation sensors, information about intermediate trophic levels remains sparse. Indeed, mid-trophic levels, while encompassing a broad range of zooplankton and micronekton organisms that represent a key component of marine ecosystems and sustain large and diverse communities of marine predators, are challenging to sample and identify. In this study, we examined whether an animal-borne miniature active echosounder can provide information on the distribution and movements of mid-trophic level organisms. If so, such a sonar tag, harnessing the persistent diving behaviour of far-ranging marine mammals, could greatly increase the density of data on this under-studied biome. High-frequency (1.5 MHz) sonar tags were deployed simultaneously with oceanographic tags on two southern elephant seals (Mirounga leonina), at the Kerguelen Islands and Valdés Peninsula (Argentina), and recorded acoustic backscatter while the seals foraged respectively in the Indian and the Atlantic sectors of the Southern Ocean. The backscatter varied widely over time and space, and the seals attempted to capture only a small fraction of the insonified targets. Diel vertical migration patterns were clearly identifiable in the data, reinforcing our confidence in the ability of the sonar tags to detect living mid-trophic organisms along with possibly sinking biological detritus. Moreover, CTD tags attached to the same animals indicated how the abundance, size distribution, and diel migration behaviour of acoustic targets varied with water bodies. These preliminary results demonstrate the potential for animal-borne sonars to provide detailed in-situ information. Further validation effort will make it a valuable tool to refine the estimation of carbon export fluxes as well as for assessing the variation of mid-trophic level biomass according to oceanographic domains and seasons.

尽管新一代传感器扩大了对海洋生态系统的原位观测，但有关中间营养水平的信息仍然很少。事实上，中营养级虽然包含范围广泛的浮游动物和微型浮游生物，它们是海洋生态系统的关键组成部分，并维持着庞大而多样的海洋捕食者群落，但采样和识别具有挑战性。在这项研究中，我们检查了动物携带的微型主动回声测深仪是否可以提供有关中营养级生物的分布和运动的信息。如果是这样，这样一个声纳标签，利用远距离海洋哺乳动物的持续潜水行为，可以大大增加这个研究不足的生物群落的数据密度。高频（1。米龙加莱奥尼娜），在凯尔盖朗群岛和瓦尔德斯半岛（阿根廷），并记录了海豹分别在南大洋的印度和大西洋部分觅食时的声学反向散射。反向散射随时间和空间变化很大，海豹试图仅捕获一小部分被声波化的目标。Diel 垂直迁移模式在数据中清晰可辨，增强了我们对声纳标签检测中营养生物体以及可能下沉的生物碎屑的能力的信心。此外，附着在相同动物上的 CTD 标签表明声学目标的丰度、大小分布和昼夜迁移行为如何随水体变化。这些初步结果证明了动物声纳提供详细原位信息的潜力。