Bioacoustic absorption spectroscopy: An acoustical oceanography method for the study of marine ecosystems

Abstract

Recent experiments have demonstrated the potential of the Bioacoustic Absorption Spectroscopy (BAS) method for measuring number densities vs. fish length and species when combined with concurrent trawling data, and studying vertical migrations and schooling behavior of fish at mesoscale dimensions.. Measurements of transmission loss between moving or stationary broadband source(s) and vertical array(s) of hydrophones separated by several (up to ~10) km permits inference of absorption coefficients versus frequency and depth, and association of absorption lines with the resonance frequencies of fish swim bladders. BAS is environmentally friendly, as it can be implemented with source levels < 170 dB, is sensitive to fish throughout the water column, including near boundaries, and is not affected by avoidance. The most significant results of BAS experiments will be reviewed, and possible approaches for use of the BAS method for routine scientific study and fisheries surveys of marine ecosystems will be consid...