Application of dolphin's sonar abilities to echo sounders
2009
Imaizumi, T.(National Research Inst. of Fisheries Engineering, Kamisu, Ibaraki (Japan))
Conservation and management are necessary for sustainable use of fisheries resources. For this purpose, acoustic surveys of fisheries resources using scientific echo sounders are conducted worldwide. Although these surveys are powerful methods of estimating fish stock biomass directly over wide areas, the acoustic survey method has several drawbacks. One is the lack of a definitive method for classifying fish species using echo data and another is that in situ target strength (TS) measurement methods can only be applied to resolvable fish at short range or in sparse fish schools. In contrast, dolphins detect, pursue, and prey on fish using their excellent sonar capability known as 'echolocation.' Dolphins can recognize not only the target size, but also its material and shape. As fish are the main target of dolphins, this sonar capability is applicable to the improvement of artificial sounders used in acoustic surveys and selective fishing. The present study was performed to investigate the application of a dolphin's sonar abilities to echo sounders. In addition, this study focused on the characteristics of broadband frequency and short duration of dolphin sonar sound and measurement of target strength (TS) spectra of fish using this type of sonar. The broadband frequency characteristics of the TS spectra of fish are believed to be key factors in target discrimination and behavior observation.
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