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Monitoring of migratory fluxes of fish and fish-like species on the Selune using a hydroacoustic method

Coordinator(s)

Aurélie Daroux, François Martignac

Scientific context

Restoring continuity to the Selune by removing its dams will bring back many species of migratory fish. The presence and abundance of these migratory fish are indicators of the good ecological status of an aquatic ecosystem. The management of migratory fish requires a good knowledge of their abundance and their level of colonisation, both of which are linked to the ecology of the species and to environmental factors. As part of the project to restore continuity to the Selune valley, it is planned to monitor changes in the biological characteristics of these migratory fish. The first step will be to assess the state of their populations.

Subject(s) of study

This project focuses on the migration activity of fish on the Selune, particularly the Atlantic salmon. The monitoring carried out by the hydroacoustic camera also takes into account environmental (temperature, river flow) and biological conditions (life cycle, nycthemeral rhythm, biometry).

Objectives

The aim of this research project is to develop and apply a method for monitoring migratory fish flows in the Selune. Various monitoring methods exist, but they cannot be adapted to all rivers. For example, video-counting stations are limited when turbidity is too high, and trapping stations require considerable human and material investment. For these reasons, a hydroacoustic method, which avoids or limits these constraints, has been chosen to monitor populations in the Selune. This project aims at monitoring and understanding migratory flows and at proposing a monitoring protocol using a hydroacoustic method.

Methods

A DIDSON hydroacoustic camera has been installed since 2013 immediately upstream of the old Ducey bridge. This site is located 10 km upstream of the mouth of the Selune and 8.5 km downstream from the first dam (La Roche Qui Boit). The camera records continuously at high frequency. The voluminous data recorded is collected every week. Analysis of the images and videos from this camera provides a quantitative and qualitative description of the migratory fish populations in the Selune.

A current meter and two temperature sensors are also installed to continuously measure environmental parameters at the study site. Spot monitoring by fishing and experimental tests were used to calibrate and validate the methods for analysing images from the hydroacoustic camera.

New research has improved the methods for analysing images and processing their outcomes. The previously visual analysis of images is now carried out automatically, using IT tools. This helps, among other things, to extend monitoring to other migratory species.

Laboratories involved

• ESE - UMR Ecosystems Health and Ecology, INRA, Agrocampus Ouest, Rennes
• ASCONIT Consultant, West Agency
• CARRTEL - UMR Alpine Research Centre for Trophic Networks and Limnic Ecosystems, INRA, Université de Savoie, Grenoble