Volume backscattering in the Tasman Sea, the Coral Sea, and the Indian Ocean Available to Purchase

Acoustic volume reverberation was measured at frequencies from 2.5 to 16 kHz at a number of stations in the Tasman Sea, the Coral Sea, and the north‐eastern region of the Indian Ocean. The dependence of volume backscattering strength on time of day, acoustic frequency, and depth beneath the sea surface were investigated. In the Coral Sea and the Indian Ocean, the average diurnal variation increased with decreasing frequency; but in the Tasman Sea the diurnal variation was almost independent of frequency. The volume backscattering strengths generally increase with frequency, but nighttime spectra are usually flatter than daytime spectra. Deep‐scattering layers were detected in the three areas at 40% of the daytime stations. Each of these DSL's had a single resonance frequency, 70% of them at 5 or 6 kHz. Most of the DSL's were at depths between 400 and 600 m. The results suggest that the volume reveration was due to backscattering by the swimbladders of mesopelogic fish.