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Comparison of the acoustic and biological sampling of the sonic scattering layers: R.R.S. ‘Discovery’ SOND Cruise, 1965
Published online by Cambridge University Press: 11 May 2009
Abstract
The acoustic measurements made during the SOND cruise are presented in the form of vertical profiles of relative scattering coefficient at day and night and its time dependence over sunrise and sunset for the four echo-sounders used. These profiles are compared with the scattering which is calculated would be returned from the vertical distributions of biological samples reported by other workers, but particularly from the distribution ofswimbladder fish analysed by Badcock. The similarities between the calculated and measured profiles support the assumption that swimbladder fish dominate the scattering due to their high target strengths, particularly at frequencies up to and including 36 kHz. By correlating fish sizes, daytime depth, migration behaviour and acoustic scattering several of the layers may be tentatively attributed to particular species. A calibrated echo-sounder in the frequency range up to 36 kHz is size selective, but can nevertheless be useful for looking at broad distributional features. However, because the numerically more abundant small planktonic animals are inadequately represented by the sounder the records are little more than a guide to net sampling programmes.
- Type
- Research Article
- Information
- Journal of the Marine Biological Association of the United Kingdom , Volume 56 , Issue 1 , February 1976 , pp. 161 - 178
- Copyright
- Copyright © Marine Biological Association of the United Kingdom 1976
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