Effect on traits of European eel and European flounder

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


Eric Feunteun (UMR BOREA) and Nils Teichert (MNHN)

Context and issues

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.

Objectives of the project

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. In this project, the relationships between life history traits of individuals (age, length, weight, fat content, condition, growth rate …) will be analyzed in association with their life history (growth habitat, estuary dependence), trophic position (delta 13C and delta 15N) and the health status. This later component will be evaluated by classic condition indices, but also by the study of intestinal microbiome and parasite communities.

Laboratories involved

Muséum national d’histoire naturelle, Station marine de Dinard

Unité BOREA – Biologie des Organismes et Ecosystèmes Aquatiques

Université Rennes 1, ECOBIO – Ecosystèmes, Biodiversité, Evolution