Target strength model inputs including morphometry, material properties, lipid composition, and in situ orientations were measured for sub-Arctic krill (Euphausia pacifica, Thysanoessa spinifera, T. inermis, and T. raschii) in the eastern Bering Sea (EBS, 2016) and Gulf of Alaska (GOA, 2017). Inter-species and -regional animal lengths were significantly different (F1,680 = 114.10, p < 0.01), while animal shape was consistent for all species measured. The polar lipid phosphatidycholine was the dominant lipid, comprising 86 ± 16% (mean ± SD) and 56 ± 22% of total lipid mass in GOA and EBS krill, respectively. Krill density contrasts varied by species and region rather than with morphometry, lipid composition, or local chla fluorescence. Mean in situ krill orientation was 1 ± 31°, with 25% of observed krill within ±5° of broadside incidence. Modelled target strength sensitivity was frequency independent for variations in material properties but was primarily sensitive to morphometry and orientation at lower (38 kHz) and higher (200 kHz) frequencies, respectively. Measured variability in material properties corresponded to an order of magnitude difference in acoustic estimates of biomass at 120 kHz. These results provide important inputs and constraints for acoustic scattering models of ecologically important sub-Arctic krill species.

中文翻译：

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亚北极磷虾材料特性、脂质成分和其他散射模型输入的个体差异会影响对其种群的声学估计

测量了白令海东部亚北极磷虾（Euphausia pacifica、Thysanoessa spinifera、T. inermis 和 T. raschii）的目标强度模型输入，包括形态测量、材料特性、脂质成分和原位方向（EBS，2016 年）和阿拉斯加湾 (GOA, 2017)。物种间和区域动物长度显着不同（F1,680 = 114.10，p < 0.01），而所有测量物种的动物形状一致。极性脂质磷脂酰胆碱是主要脂质，分别占 GOA 和 EBS 磷虾中总脂质质量的 86 ± 16%（平均值 ± SD）和 56 ± 22%。磷虾密度对比因物种和地区而异，而不是随形态测量、脂质组成或局部叶绿素荧光而变化。平均原位磷虾方向为 1 ± 31°，25% 的观察到的磷虾在舷侧入射的 ±5° 内。建模的目标强度灵敏度与材料特性变化的频率无关，但主要对较低 (38 kHz) 和较高 (200 kHz) 频率下的形态测量和方向敏感。材料特性的测量变异性对应于 120 kHz 生物量声学估计的数量级差异。这些结果为生态重要的亚北极磷虾物种的声散射模型提供了重要的输入和约束。材料特性的测量变异性对应于 120 kHz 生物量声学估计的数量级差异。这些结果为生态重要的亚北极磷虾物种的声散射模型提供了重要的输入和约束。材料特性的测量变异性对应于 120 kHz 生物量声学估计的数量级差异。这些结果为生态重要的亚北极磷虾物种的声散射模型提供了重要的输入和约束。