Authia and its tributaries are a fragile and complex ecosystem. This coastal river is frequented by many migratory fish species that need to move along streams in order to establish their life cycle. This migration is constrained by a large number of impassable dams for most of these species. The development operations provided for in this project concern works which impede the free movement of fish. The Interdepartmental Institution requests financial support from the ERDF in connection with the development of three dams located on the communes of Vitz-sur-Authie (80)/Le Ponchel (62), Willencourt (62) and Doullens (80). This work consists mainly of the dismantling of the vannages and the creation of rock-rock ramps. The procedure authorising the derogation from a financial intervention by the ERDF Nord Pas-de-Calais on investments made in the department of Somme is being prepared by the managing authority. At the end of this operation, the areas of restored natural habitats are estimated at 20.58 ha in the Pas-de-Calais territory and 19.14 ha in the territory of the Somme, for a total of 39.72 ha. The total eligible cost of this operation is EUR 281,556.00 VAT, with a ERDF grant of EUR 123 000 at a rate of 43.69 % of aid.