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Habitat use by amphihaline fish - Stage 1: Telemetric study of migratory fish movements in the Sélune before dam removal

Coordinator(s)

Emilien Lasne

Scientific context

One of the major challenges in restoring ecological continuity in the Selune basin is the recolonisation, by migratory fish, of the sectors located upstream of the dams, which offer significant habitat potential. The assumption of a relatively rapid and massive recolonisation of these areas was a strong argument in favour of removing the dams, given the problems of conserving fish populations.

Subject(s) of study

The project focuses on Atlantic salmon (Salmo salar) as a model migratory fish on the Selune.

Objectives

In order to characterise the movements and identify the habitats used by salmon in the Selune basin after the removal of the dams, this project proposes to set up a radio telemetry protocol. The aim of the project is twofold:

1. Implementation of the telemetric monitoring methodology. The telemetry protocols are generally well mastered, whether it be the installation of a detection network or the marking of fish, and the main obstacle concerns the protocol for capturing salmon in the Selune estuary, which needs to be developed.
2. The production of initial data on the characterisation of the use of downstream pre-damming habitats.

Methods

Salmon spawners are captured in the Selune estuary during their anadromous migration (in spring and summer) and fitted with radio transmitters, coupled with temperature sensors and an accelerometer. Once equipped, these fish can be tracked over time and space using telemetry to understand their movements and identify their habitat or spawning grounds. To do this, radio detection antennae are installed in the Selune basin at the entrances to the main tributaries and along the main course, and others are also installed downstream of the other tributaries in the Bay of Mont Saint Michel to identify any movements between tributaries. Monitoring using mobile detection antennae is also carried out after the marking period and over the following months until after the spawning period.

Laboratories involved

• DECOD - UMR Ecosystem Dynamics and Sustainability: from source to ocean, INRAE/Institut Agro/Ifremer, Rennes
• MNHN - Museum National d'Histoire Naturelle, Dinard Marine Station
• BOREA - UMR Biology of Aquatic Organisms and Ecosystems, Dinard