Biological sound scattering in an ocean eddy

Abstract

Acoustic volume-backscattering measurements and midwater net-trawls were conducted in the vicinity of an eddy in the Tasman Sea in 1979 and 1980. At acoustic frequencies greater than about 8 kHz, there is generally good agreement between the measured acoustic backscattering strengths and the predictions based on the results of the trawls. The main difference is that, although the trawls did not catch any fish heavier than 3 g, the acoustic results indicated that many heavier fish were present within the trawling regions. The acoustic scattering inside the eddy was several decibels higher than the scattering in the frontal region or outside the eddy during two of the three cruises that were conducted. For the remaining cruise, there was no significant difference.