Ex situ echo sounder target strengths of ice krill Euphausia crystallorophias

• Published in: Chinese journal of oceanology and limnology 2015-05, Vol.33 (3), p.802-808
• Main Authors: La, Hyoung Sul, Lee, Hyungbeen, Kang, Donhyug, Lee, SangHoon, Shin, Hyoung Chul
• Format: Article
• Language: English
• Subjects: Approximation; Aquatic life; Body length; Body measurements; Body size; Born approximation; Comparative analysis; Comparative studies; Earth and Environmental Science; Earth Sciences; Echo sounding; Echoes; Ecosystems; Euphausia; Euphausia crystallorophias; Euphausiacea; Freshwater; Ice; Inland water environment; Keystone species; Krill; Marine crustaceans; Marine ecosystems; Oceanography; Physics; Regression models; Sonar detection; Sound detecting and ranging; Stochasticity; Stocks; Target strength; Wet weight; 优势; 冰; 南极磷虾; 扭曲波玻恩近似; 生态系统; 目标强度; 线性回归模型; 车身尺寸
• ISSN: 0254-4059; 2096-5508; 1993-5005; 2523-3521
• DOI: 10.1007/s00343-015-4064-3

Ice krill is the keystone species in the neritic ecosystem in the Southern Ocean, where it replaces the more oceanic Antarctic krill. It is essential to understand the variation of target strength （TS in dB re l m^2） with the different body size to accurately estimate ice krill stocks. However, there is comparatively little knowledge of the acoustic backscatter of ice krill. The TS of individual, formalin-preserved, tethered ice krill was measured in a freshwater test tank at 38, 120, and 200 kHz with a calibrated split-beam echo sounder system. Mean TS was obtained from 21 individual ice krill with a broad range of body lengths （L： 13-36 iron）. The length （L, mm） to wet weight （W; mg） relationship for ice krill was 11/=0.001 21g~103~L35s （R2=0.96）. The mean TS-to-length relationship were TS38kHz=-177.4＋57log10（L）, （R^2=0.86）; TS120kHz= -129.9＋31.561ogf0（L）, （R2=0.87）; and TS200kHz=-117.6＋24.661ogre（L）, （R2=0.84）. Empirical estimates of the relationship between the TS and body length of ice krill were established at 38, 120, and 200 kHz and compared with predictions obtained from both the linear regression model of Greene et al. （1991） and the Stochastic Distorted Wave Born Approximation （SDWBA） model. This result might be applied to improve acoustic detection and density estimation of ice krill in the Southern Ocean. Further comparative studies are needed with in situ target strength including various body lengths of ice krill.