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Abstract

The U.S. Office of Naval Research has sponsored research in the area of marine organism acoustics for many years. The research program has included development of theoretical physics-based acoustic scattering models of single animals, high-resolution laboratory measurements of scattering by individual animals, and at-sea field experiments. The program has been focused on the backscattered signal, but has also included investigation of the forward-scattered signal. Downward-looking acoustic surveys using ship borne echosounders rely on the backscattered signal and provide non-invasive, non-destructive, rapid, high-resolution, large area survey capability compared to traditional net tows. Horizontally-oriented acoustic surveys provide the opportunity to investigate both the backscattered and forward-scattered signals from marine organisms and their impact on long-range acoustic propagation characteristics in the shallow water environment. Both cases require an understanding of the scattering characteristics of each type of organism and aggregation in the acoustic path as a function of acoustic frequency and orientation relative to the acoustic source and receiver. This overview of the fish-related acoustics research program includes representative examples which demonstrate the fundamental physical principles which have shaped the program.

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