Amphihaline migratory species: back upstream?

Amphihaline migratory species: back upstream?

What migratory fish will recolonise the upper reaches of the Sélune, which have been inaccessible until now? Where will they go, and how quickly will this recolonisation take place?

Restoring the continuity of the Sélune river will profoundly change the distribution of fish species in its watershed. In particular, amphihaline migratory fish (which migrate between the ocean and the river during their lives) will once again be able to swim through the Selune. These species never really left the Selune after the dams were built a century ago. But they were confined to the downstream part of the river, right up to the foot of the dams. Restoring ecological continuity should enable them to recolonise the Selune and its tributaries upstream in the watershed.

The Selune is home to a number of amphihaline fish, including sea lamprey, river lamprey, sea trout, Atlantic salmon and European eel. There are also thinlip mullet and European flounder, two marine species found only in the downstream section of the Selune.

Migratory fish species of the Selune river

Surveys using electrofishing and monitoring of spawning grounds (fish nests) are used to track their progress upstream since the removal of the dams.

Inventory by electrofishing (Photo: M.Druet), sea lamprey spawning ground (Photo: P.Vrchovsky), sampling of scales from an Atlantic salmon (Photo: M.Druet)

Modification date : 17 August 2023 | Publication date : 31 July 2023 | Redactor : L'équipe Sélune