The opening of the dams will have a significant impact on the Atlantic salmon populations swimming up the Sélune River and its tributaries. Restoring the river's ecological continuity will modify population flows, allowing atlantic salmons to migrate further upstream and downstream of the dams. The atlantic salmons population is monitored at a network of stations covering the entire Sélune basin, using an abundance index carried out every 2 years. Field campaigns comply with the fishing protocol developed by INRAE and OFB. The aim of this method is to estimate the abundance of juvenile Atlantic salmon (Salmo salar) at a station (or sector). This protocol targets juveniles of the year (aged 0+) whose abundance reflects the renewal of generations within the population (or recruitment) and survival after the embryonic development phases under gravel and the first months of life in the open environment. Field campaigns are carried out by INRAE and the Fédération de la Manche et d'Ille-et-Vilaine pour la Pêche et la Protection du Milieu Aquatique (FDAPPMA35). This layer shows the locations of these study sectors by year of study: 2012, 2013, 2014, 2015, 2018, 2019, 2020, 2021, 2022, 2023 and 2024.

The removal of the dams on the Sélune River is the subject of a scientific program launched in 2012, in which environmental parameters are monitored in order to provide real feedback on this restoration operation. In 2019, a data observatory was set up to collect and process these parameters (biotic and abiotic). The data acquired from 2012 and at least until 2027 will be centralized through an information system (IS) called SISelune. SISelune aims to assist scientists associated with the Sélune program and make the data accessible to all. This layer shows the study area, based on hydrographic sub-basins for the continental part and the transitional water body for the Bay of Mont St-Michel.

The restoration of the Sélune river continuum after the dams were demolished will allow colonization of the upper reaches of the basin, which were previously inaccessible to eels. Before the demolition, two main tributaries were used by amphihaline fish for reproduction, in addition to the main river: the Beuvron and the Oir. The eel population of the Sélune was monitored in the pre-demolition phase by abundance index campaigns carried out in 2013, 2015, 2019, and then every year since 2021, on a network of stations covering the entire Sélune river system. These data make it possible to estimate changes in eel abundance along the Sélune and its tributaries and their size structure before and after the destruction of the dams. The inventory is carried out in early September, every other year, then every year since 2021, using electric fishing equipment and landing nets. Thirty fishing points are carried out for a minimum of 30 seconds. A fishing station covers approximately 100 meters of river. All eels caught are anesthetized and undergo biometric measurements (weight, length, horizontal and vertical eye diameter, determination of yellow or silver stage). All eels are released directly at the fishing site. This sheet refers to two layers, one showing only the study areas and their location, and the other specifying the concept of capture sessions.

The opening of the dams will have a considerable impact on the functioning of trout populations in the Sélune. Restoring the river's ecological continuity will modify population flows, allowing amphihaline sea trout to migrate further upstream, and native trout to move upstream and downstream of the dams. The trout population is monitored at a network of stations covering the entire Sélune basin, using an abundance index carried out every 2 years. Field campaigns follow the Vigitruite® fishing protocol, developed at INRAE for use throughout France. This index of abundance, related to the surface area of favorable habitats on the watercourse, makes it possible to evaluate the quantity of trout present in the river, resulting from natural reproduction in previous years. Field campaigns are carried out by INRAE and the Fédération d'Ille-et-Vilaine pour la Pêche et la Protection du Milieu Aquatique (FDAPPMA35). This layer shows the locations of these study sectors by year of study: 2012, 2014, 2018, 2020, 2022 and 2024.

The restoration of the Sélune river continuum after the dams were demolished will allow colonization of the upper reaches of the basin, which were previously inaccessible to eels. Before the demolition, two main tributaries were used by amphihaline fish for reproduction, in addition to the main river: the Beuvron and the Oir. The eel population of the Sélune was monitored in the pre-demolition phase by abundance index campaigns carried out in 2013, 2015, 2019, 2021, and 2023 on a network of stations covering the entire Sélune river system. These data make it possible to estimate changes in eel abundance along the Sélune and its tributaries and their size structure before and after the destruction of the dams. The inventory is carried out in early September, every other year, using electric fishing equipment and landing nets. Thirty fishing points are carried out for a minimum of 30 seconds each. A fishing station covers approximately 100 meters of river. All eels caught are anesthetized and undergo biometric measurements (weight, length, horizontal and vertical eye diameter, determination of yellow or silver stage). All eels are released directly at the fishing site. This layer contains individual data on the eels caught.

Dams cause significant changes to the hydrological regime, water temperature, and biological and biogeochemical flows. This is the case for the Vezins and La Roche qui Boit dams, located on the main course of the Sélune River, which resulted in the existence of two reservoirs between 1919 and 2022 for La Roche qui Boit and between 1932 and 2019 for Vezins. Since the end of the last emptying of the La Roche qui Boit dam at the end of 2022, these two lakes no longer exist in the valley landscape. This layer represents the two reservoirs as they were referenced in 2017, i.e. before the start of the dismantling work on the two hydroelectric dams on the Sélune. Among the attribute data associated with these two entities, the length is based on a calculation made by the Sélune project team using the reference points established across the entire watershed (and therefore across the entire course of the Sélune) and their knowledge of the areas of influence of the lakes/natural watercourse.

In 2020, scientific plots were set up, marked out on the ground with colored stakes. These plots are intended to facilitate scientific monitoring, particularly of renaturation. These plots represent privileged areas for scientists, where no sediment or vegetation disturbance is planned until the end of the Sélune program.

The re-establishment of the river continuum on the Sélune after the dams have been levelled will enable colonization of the upper reaches of the basin, which were previously inaccessible to eels. Before the dams were levelled, two main tributaries were used by amphihaline fish for reproduction, in addition to the main river: the Beuvron and the Oir. The eel population of the Sélune was monitored in the pre-flushing phase by abundance index campaigns carried out in 2013, 2015, 2019 on a network of stations covering the entire Sélune hydrographic network. Since 2021, this network of stations has evolved to monitor changes in the part of the watershed accessible following the dismantling of the 2 dams. These data enable us to estimate changes in eel abundance along the Sélune and its tributaries, as well as their size structure before and after the removal of the dams. The inventory is carried out in early September, every other year between 2013 and 2019, then every year since, using an electric fishing device and dip nets. Thirty thirty-second fishing stations are set up. A fishing station comprises approximately 100 meters of river. All eels caught are anaesthetized and biometric measurements are taken (weight, length, horizontal and vertical eye diameter, determination of yellow or silver stage). All eels are released directly at the fishing site. This layer provides station abundances by fishing session.

The removal of the dams of the Sélune is the subject of a scientific programme initiated in 2012 in which environmental parameters are monitored in order to provide real feedback on this restoration operation. In 2019, a data observatory was set up to ensure the collection and processing of these parameters (biotic and abiotic). The data acquired from 2012 and at least until 2027 will be centralized through an information system (IS), called SISelune. SISelune aims to help scientists involved in the Sélune programme and make data accessible to all. The Sélune scientific programme has a reference system, composed of points. These points can be used by all program actors to more easily identify any location within the study area. The points are created along the rivers, with an approach "Point kilométrique" (every 100m, going from upstream to downstream). Each of these points has a unique code, corresponding to the association of the watercourse (designated by a short code) and the distance to the source or confluence. Since 2025, each of these points has also been characterized by its position in the watershed (downstream, upstream, ...) in relation to the zone determined by the former dams and their reservoirs, as well as their distance from the sea in 2 forms (LTM: Limite Transversale à la mer / Transverse Sea Limit and LSE: Limite Salure des eaux / Water salinity limit).

The removal of the dams on the Sélune River is the subject of a scientific program launched in 2012, in which environmental parameters are monitored in order to provide real feedback on this restoration operation. In 2019, a data observatory was set up to collect and process these parameters (biotic and abiotic). The data acquired from 2012 and at least until 2027 will be centralized using an information system (IS) called SISelune. SISelune aims to assist scientists associated with the Sélune program and make the data accessible to all. Watercourses are linear hydrographic entities, linked to a main place name and broken down into hydrographic sections. These watercourses are extracted from the Topage database covering the study area. Codes that can be used within the Sélune program have been added, as well as codes from the former hydrographic reference system (Carthage database).