French diadromous fish facing climate change : evolution of numbers and modification of migratory phenology

• Main Author: Hoffmann Legrand, Marion
• Other Authors: Laboratoire Ecologie Fonctionnelle et Environnement (LEFE), Institut Ecologie et Environnement - CNRS Ecologie et Environnement (INEE-CNRS), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT), Institut National Polytechnique de Toulouse - INPT, Pascal Lafaille
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2021
• Subjects: Diadromous fish; Phenology; Climate change; Migration; Poissons amphihalins; Phénologie; Changement climatique; [SDV.SA]Life Sciences [q-bio]/Agricultural sciences; French River; Anguilla anguilla; Salmo salar
• Online Access: https://theses.hal.science/tel-04170626; https://theses.hal.science/tel-04170626/document; https://theses.hal.science/tel-04170626/file/Hoffmann-Legrand_Marion.pdf

Diadromous fish are in decline in France and in the world. Living alternately in fresh and saltwater, they are faced with many pressures to which is added the ongoing climate change that leads mainly to three major modifications : (I) change in the area of distribution of species, (ii) modification of the timing of key moments in life cycles (e.g. migration, reproduction), and (iii) modification of the spatial synchrony of populations. Emblematic species of our rivers with high economic value, diadromous fish are the subject of management plans throughout France, mainly at the basin scale, with few perspectives on the state of these populations at the national scale. The objective of this work is to help to fill this gap by analysing data in all French river basins. These data were never pooled to date, nor valued at this spatial scale. We collected the data of 46 counting stations with a history of at least 10 years and about 5 diadromous taxa: Alosa spp. (gathering A. fallax and A. alosa), Anguilla anguilla, Petromyzon marinus, Salmo salar and Salmo trutta. Based on this dataset, we asked 3 questions : (i) how the counts of diadromous fish have evolved in France over the last 30 years, (ii) have these taxa modified their timing of migration during this period of study, and what are the explanatory parameters, and finally (iii) is there a spatial synchrony in the dynamics and timing of migration of these populations, and what are the explanatory parameters. We show that the evolution of counts is contrasted between species and basins, with taxa decreasing at the French scale (Alosa spp. and Petromyzon marinus) while others are increasing slightly or in stagnation. Alosa spp. is both the taxon showing the greatest decrease in its counts at the French scale and the least contrast between the basins, attesting to a fairly general decline in France. Analysis of the timing of migration has shown an overall advance in median migration dates for all taxa (except for glass eels), on average -2.3 days per decade (min= ...