Scattering and reverberation from fish schools in the 500–1500 Hertz band

We report here on the preliminary results from an experiment off Cape Hatteras, North Carolina, to look at acoustic scattering and reverberation from fish schools in the 500–1500 Hz band. The experiment, which was performed during the period May 12–29, 2012, was a joint acoustics, biology and physical oceanography effort, with distinct, but coordinated, goals in each area. Acoustically, our goal was to examine the scattering of sound from fish schools over a full range of azimuthal angles. To do this, we employed a source mounted on an autonomous vehicle and a moored, four element hydrophone array receiver. The source traveled around the fish school and the receiver, giving the desired angular diversity. Biologically, we were interested in mapping and imaging/classifying the fish (both individually and as schools) with the sidescan sonars on the vehicles, and contrasting/verifying this information with video images from high definition cameras attached to the vehicles. Oceanographically, the correlation between the ocean temperature field and the fish species encountered was of first order interest. Results from all three areas will be presented, including some interesting video images, and directions for analysis and further research will be discussed. [ Work sponsored by the Office of Naval Research.]