2019 to 2021
Program type
Regional - National
Scientific cooperation

Effect of dam removal on the history traits of diadromous species: the case of the catadromous European eel and European flounder on the Sélune River


The dam removal on the Sélune River is expected to promote recolonization of the upstream catchment by fish, especially migratory fish. This project aims to investigate this process by describing changes in biological traits of diadromous fish, such as age, size, weight or growth rate, as well as following the dynamics of migratory populations. Habitat changes during the life history of these species will also be examined, from estuarine areas to upper river reaches. Accordingly, the observed modifications will help to quantify the influence of dam removal on fish stocks, such as that of the eel, and to draw lessons to guide future restoration measures of the ecological continuity.

The objective of this project is to describe the life history traits of European eels and flounder, two diadromous species that grow in rivers and reproduce at sea, before the removal of dams on the Sélune River. Such restoration of river continuity is expected to yield two effects on these populations: 1) The recolonization of upstream habitats should induce a decrease of intra-specific competition, as well as change in life history traits and sanitary conditions, particularly for eels. 2) Sediment and nutrient fluxes will be modified, resulting in modification of habitat quality, especially in the estuary, with a potential impact on nursery function for flounder juveniles. The complementary study of flounder and eel provides a relatively inclusive view of the effects of dam removal. Indeed, the flounder is mainly sensitive to the modification of downstream areas at the sea-river interface (estuarine nursery), whereas the eel will be responsive to changes in accessibility and quality of habitats distributed in the whole watershed.


  • Agence de l’Eau Seine Normandie
  • Agence Française pour la biodiversité


  • Muséum national d’histoire naturelle, Station marine de Dinard
  • Laboratoire BOREA – Biologie des Organismes et Ecosystèmes Aquatiques
  • Université Rennes 1, ECOBIO – Ecosystèmes, Biodiversité, Evolution