Recording fish schools by multi-beam sonar: potential for validating and supplementing echo integration recordings of schooling fish

A method for comparing recordings of fish schooling near surface by a conventional echo integration unit and a multi-beam sonar system is outlined. The sonar system consists of a 95 kHz SIMRAD SA950 multi-beam sonar connected to a work station with software fur reading the echo telegrams of the sonar, printing echograms, automatic detection and measurement of schools, and logging of the sonar data. This method has been employed to map sardine in False Bay, South Africa, and the abundance estimates obtained by conventional echo integration were compared to that obtained by sonar. It is concluded that the sonar method may be used to validate the recordings obtained by conventional echo integration, and also provide more precise mapping and abundance estimates of pelagic fish stocks in schools near the surface. (C) 2000 Elsevier Science B.V. All rights reserved.