Since 2021, Andromède océanologie has been studying the breeding colonies of picarels (Spicara smaris) in Corsica. According to our observations, these breeding areas are home to thousands of individuals and cover several hectares, forming temporary ecosystems where many species come to feed, including species classified as critically endangered by the IUCN, such as the common angel shark (Squatina squatina). Due to the enormous concentration of individuals (in space and time) that they generate, the breeding colonies of picarels, which are mainly plankton-eating fish, could be an essential but unknown in the trophic network, transferring organic matter from the open water (plankton) to predatory species in shallow waters and the open sea. Gaining a deeper understanding of this phenomenon and its timing is all the more important considering their high sensitivity to abrasion: the entire reproductive effort of a population can be destroyed all at once by trawling. Acoustic telemetry is part of a project to characterize more precisely the dynamics of breeding colonies.