Sources of acoustic backscattering at 87.5 kHz

Publisher Website
Google Scholar
Abstract
Sources of acoustic backscattered energy at 87.5 kHz were identified using 3 independent approaches. The 1st approach combined the Johnson fluid sphere scattering model with a hypothesized distribution of scatters. From these models the percentage of total scattering due to organisms of a particular size range was determined. The 2nd approach inferred scatterer abundance from probability distributions of acoustic scattering strength for insonified volumes of different sizes. The 3rd approach consisted of comparing levels and patterns of scattering strength observed with a sonar to biological samples taken in the same area at the same time. All 3 approaches indicated that the sources of backscattered acoustic energy came from large zooplankton and small nekton. The 1st approach underestimated the importance of large scatterers at night. Day scattering was dominated by large copepods and small euphausiids. When small fish were present, they dominated the scattering. Night samples were dominated by mesopelagic fish, squid and euphausiids. The fish and squid usually dominated the scattering early in the evening while euphausiids tended to dominate the scattering later at night.

This publication has 5 references indexed in Scilit: