The conservation status of the long-lived Greenland shark (Somniosus microcephalus) is unknown, and methods for non-invasively estimating local or regional abundances are wanted. Using a multifrequency split beam echosounder during long line fishery for Greenland sharks, we demonstrate how individual sharks can be identified and separated with high accuracy from the acoustic backscattering at three frequencies. From a slowly drifting vessel, hooked and free-swimming targets with similar target characteristics were identified on echograms along the bottom and in the water column over a depth of ∼ 400 m. A discriminate analysis using target frequency response, target strength and echo pulse stretching was used to identify shark targets from the only possible competitor, with respect to target strength, being large Atlantic cod (Gadus morhua). Isolation and tracking of single targets allowed us to calculate the swimming speeds ranging between 0.16 and 0.84 m s⁻¹ (mean ± SD, 0.47 ± 0.18 m s⁻¹) from 15 free-swimming sharks over distances from 11 and 50 m in time periods of 28 to 122 s per track. Our findings demonstrate the first acoustic detection of Greenland sharks, and thus provide a new non-invasive monitoring method applicable in otherwise difficult-to-access arctic and deep-sea waters.

长寿格陵兰鲨（Somniosus microcephalus ）的保护现状) 是未知的，需要非侵入性估计局部或区域丰度的方法。在格陵兰鲨鱼的长线捕捞过程中使用多频分束回声测深仪，我们展示了如何从三个频率的声学反向散射中高精度地识别和分离个体鲨鱼。从一艘缓慢漂流的船只上，沿着底部和水柱深度约 400 m 的回波图中识别出具有相似目标特征的钩状和自由游动目标。使用目标频率响应、目标强度和回波脉冲展宽的判别分析被用来从唯一可能的竞争者中识别鲨鱼目标，就目标强度而言，大大西洋鳕鱼 ( Gadus morhua )）。单个目标的隔离和跟踪使我们能够计算15 条自由游泳鲨鱼在 11 和 50 m 的时间段内的游泳速度范围在 0.16 和 0.84 m s ^-1之间（平均值 ± SD，0.47 ± 0.18 m s ^-1 ）。每轨 28 到 122 秒。我们的研究结果证明了格陵兰鲨鱼的首次声学检测，从而提供了一种新的非侵入性监测方法，适用于其他难以进入的北极和深海水域。