FISH ACOUSTICS: PHYSICS-BASED MODELING AND MEASUREMENT

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.