Guillard J. auteur aut IRD Lebourges Dhaussy Anne auteur aut IRD Brehmer Patrice auteur aut IRD text journalArticle eng text/pdf reformatted digital access 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. POISSON D'EAU DOUCE ESTIMATION DE STOCK PROSPECTION ACOUSTIQUE SONAR DISTRIBUTION SPATIALE VARIATION JOURNALIERE METHODE D'ANALYSE ETUDE COMPARATIVE FRANCE 040PECHE03 61 2 267-273 2004 1054-3139 https://www.documentation.ird.fr/hor/fdi:010033843 10.1016/j.icesjms.2003.11.007 1054-3139 [F B010033843] https://www.documentation.ird.fr/hor/fdi:010033843 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/2024-01/010033843.pdf IRD - Base Horizon / Pleins textes 2004-09-01 2024-01-08 fdi:010033843 fre