Department of Electrical and Computer Engineering, Northeastern University, 360 Huntington Avenue, Boston, Massachusetts 02115, USA.
J Acoust Soc Am. 2011 Sep;130(3):1253-71. doi: 10.1121/1.3614542.
An ocean acoustic waveguide remote sensing system can instantaneously image and continuously monitor fish populations distributed over continental shelf-scale regions. Here it is shown theoretically that the areal population density of fish groups can be estimated from their incoherently averaged broadband matched filtered scattered intensities measured using a waveguide remote sensing system with less than 10% error. A numerical Monte-Carlo model is developed to determine the statistical moments of the scattered returns from a fish group. It uses the parabolic equation to simulate acoustic field propagation in a random range-dependent ocean waveguide. The effects of (1) multiple scattering, (2) attenuation due to scattering, and (3) modal dispersion on fish population density imaging are examined. The model is applied to investigate population density imaging of shoaling Atlantic herring during the 2006 Gulf of Maine Experiment. Multiple scattering, attenuation and dispersion are found to be negligible at the imaging frequencies employed and for the herring densities observed. Coherent multiple scattering effects, such as resonance shifts, which can be significant for small highly dense fish groups on the order of the acoustic wavelength, are found to be negligible for the much larger groups typically imaged with a waveguide remote sensing system.
海洋声学波导遥测系统可以实时成像并持续监测分布在大陆架尺度区域的鱼类种群。本文从理论上表明，使用波导遥测系统测量的鱼类群体的非相干平均宽带匹配滤波散射强度可以估计其面积种群密度，误差小于 10%。本文开发了一个数值蒙特卡罗模型来确定从鱼类群体散射回波的统计矩。该模型使用抛物线方程模拟随机、频变海洋波导中的声场传播。研究了多次散射、散射衰减和模态色散对鱼类种群密度成像的影响。该模型应用于 2006 年缅因湾实验中对聚集的大西洋鲱鱼的种群密度成像研究。在使用的成像频率和观察到的鲱鱼密度下，发现多次散射、衰减和色散可以忽略不计。对于数量级与声波波长相当的小型高密度鱼类群体，相干多次散射效应（如共振位移）可能非常显著，但对于通常用波导遥测系统成像的更大鱼类群体，这些效应可以忽略不计。
