Estimation of fish school volume using onmidirectional multi-beam sonar: Scanning modes and algorithms

Previous studies have resulted in a quantitative omnidirectional sonar (FSV30 research version, Furuno) using 64 multi-beams and a 24 kHz center operating frequency. The practical applications of this sonar are currently being studied with regard to fisheries resource assessment. This paper presents one part of this research, i.e., methods for estimating fish school volume using different sonar scanning modes. To determine its suitability for various purposes, we conducted a simulation to measure scatter aggregation; the simulation was validates by measuring the volume of a balloon filled with seawater. A practical survey was also simulated for spherical scatter aggregation with a 20 m, diameter, and its volume was examined using different scanning modes. Our results indicate that a semicircular cruise mode is more suitable than a circular mode for measuring fish school volume, and that using an anchored instrument scanning mode provides greater accuracy than a cruising scanning mode.