Improvement in school-size estimates of pelagic fish using information from sector-scanning sonar

• Published in: Fisheries oceanography 2002-11, Vol.11 (6), p.361-365
• Main Authors: Hamano, Akira, Nakamura, Takeshi, Maeda, Hiroshi
• Format: Article
• Language: English
• Subjects: anchovy school; Engraulis japonica; Marine; quantitative echo sounder; school-size estimates; sector-scanning sonar; three-dimensional image
• ISSN: 1054-6006; 1365-2419
• DOI: 10.1046/j.1365-2419.2002.00212.x

School‐size estimates based on information from a sector‐scanning sonar were compared with those based on information from an echo sounder. Three pairs of size estimates of anchovy schools in the coastal waters, off Fukuoka Prefecture were shown as examples. They included the possibility of improving the size estimates by using information from sector‐scanning sonar to consider the size in the transverse direction. In these examples, the thickness and extent of the school varied in the transverse direction. A large difference was found between the estimates from the sounder information and those from the sector‐scanning sonar information, although whether or not the estimated size decreased differed according to each case. Also, whether the thickness information or the extent information is influential differed according to each case. The size information from the sector‐scanning sonar in the transverse direction caused a change in the estimated size from 66 to 16 (×103 m3, mainly by different extent), 305 to 146 (×103 m3, thickness increased but extent decreased), and 819 to 746 (×103 m3, three seemingly separated schools fused into one).