Simultaneous Sv and TS measurements on Young-of-the-Year (YOY) freshwater fish using three frequencies

• Published in: ICES journal of marine science Vol. 61; no. 2; pp. 267 - 273
• Main Authors: Guillard, J, Lebourges-Dhaussy, A, Brehmer, P
• Format: Journal Article
• Language: English
• Published: Oxford University Press 2004
• Subjects: Animal biology; dual beam; Environmental Sciences; Freshwater; lake; Life Sciences; multi-frequency; Perca fluviatilis; Physics; split beam; target strength; France, Rhone-Alpes, Annecy L; multi-frequency; freshwater; split beam; target strength; lake; dual beam; ETUDE COMPARATIVE; PROSPECTION ACOUSTIQUE; METHODE D'ANALYSE; VARIATION JOURNALIERE; SONAR; Perca fluviatilis; POISSON D'EAU DOUCE; DISTRIBUTION SPATIALE
• ISSN: 1054-3139; 1095-9289
• DOI: 10.1016/j.icesjms.2003.11.007

In autumn, the fish population above the thermocline in Lake Annecy mainly comprises young perch (Perca fluviatilis) of the year. The fish are distributed in schools during the day and as scattered individual fish targets at night. Measurements of volume-backscattering strength and target strengths (TS) were carried out in a synchronous way using three echosounders operating at three frequencies (70, 120, and 129 kHz), with different characteristics (split beam, dual beam, beam shape, pulse length, etc.). Target-strength values show variability from one elementary sampling unit to another and from one device to another, but the mean global TS values are similar, independently of the frequency. The volume-backscattering strengths measured on precise schools by the three acoustic devices give significantly similar results. Acoustic measurements on YOY perch are completely independent of the frequency and the characteristics of the echosounders.