Schematic overview of the methodological framework used to track the dynamics of Hemimysis anomala winter swarms in Lake Geneva. The central panel (A) shows the study area near Amphion-les-Bains and Thonon-les-Bains. Triangle indicates the site of instrument deployment (acoustic and infrared cameras), while red points indicate perch stomach sampling sites (littoral and deeper offshore locations). The study combined four complementary approaches: (B) high-frequency acoustic camera to quantify mysid swarm dynamics; (C) visible-infrared video recordings to monitor perch (Perca fluviatilis) presence with direct observation of predation events; (D) direct underwater observations of mysid swarms by scientific and recreational divers; and (E) analysis of perch stomach contents using environmental DNA approaches (metabarcoding, ddPCR) and visual identification.