The aim of this operation is to ensure the sustainability of the monitoring of aloses in the medium Loire and aims to obtain information on the migrant population of shades (species, height, weight, sex, age, migration schedule) on a barrier-free range and for juveniles to obtain data on the period of grading by combining regular sampling monitoring and environmental DNA sampling, their biological characteristics and to know the habitats frequented during this migration phase. This operation is submitted under Action 12 of the ERDF Loire POI.