David V. auteur aut IRD Mouget Anne auteur aut IRD Perrot Yannick auteur aut IRD Le Goff L. auteur aut IRD Thiriet P. auteur aut IRD Diogoul N. auteur aut IRD Feunteun E. auteur aut IRD Acou A. auteur aut IRD Brehmer Patrice auteur aut IRD text journalArticle eng text/pdf born digital access Surveying pelagic fish population dynamics in ultra-shallow waters (<20m) is often limited by research vessel size, which not usually navigate in shallow waters. Here, we use a multibeam echosounder to detect fish shoals and assess their characteristics (acoustic density and 3-D morphology) in ultra-shallow waters to follow European Marine Strategy Framework Directive (MSFD) request. Surveys were made in two coastal areas in French Brittany during different seasons (spring, summer, autumn) in 2020. Our surveying methodology applying portable multibeam echosounder on small vessels allowed us to successfully survey pelagic fish spatio-temporal distributions in ultra-shallow waters. Numerous shoals have been observed which could account for important biomass and they were significantly denser and larger in ultra-shallow waters compared to shoals in deeper areas for both study sites. Shoal surfaces and volumes were also significantly lower in autumn compared to spring and summer. In addition, Atlantic mackerels (Scomber scombrus) were observed in ultra-shallow waters areas during summer in both study sites. Consequently, the multibeam echosounder is a workable and relevant tool for setting up long-term surveying of pelagic fish in ultra-shallow waters (coastal and estuarine ecosystems) as required by the MSFD to better assess pelagic fish ecological status. specialized Pelagic fish Multibeam Echosounder Ultra-shallow waters Coastal ecosystems FRANCE ATLANTIQUE BRETAGNE 036 020 264 107705 [11 ] 2022 0272-7714 https://www.documentation.ird.fr/hor/fdi:010085116 10.1016/j.ecss.2021.107705 0272-7714 [F B010085116] https://www.documentation.ird.fr/hor/fdi:010085116 https://www.documentation.ird.fr/intranet/publi/2022-07/010085116.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2022-07-01 2025-02-24 fdi:010085116 fre