Basin-scale phenology and effects of climate variability on global timing of initial seaward migration of Atlantic salmon (Salmo salar)

• Published in: Global Change Biology
• Main Authors: Otero, Jaime, L'Abee-Lund, Jan Henning, Castro-Santos, Ted, Leonardsson, Kjell, Storvik, Geir O., Jonsson, Bror, Dempson, Brian, Russell, Ian C., Jensen, Arne J., Baglinière, Jean-Luc, Dionne, Melanie, Armstrong, John D., Romakkaniemi, Atso, Letcher, Benjamin H., Kocik, John F., Erkinaro, Jaakko, Poole, Russell, Rogan, Ger, Lundqvist, Hans, Maclean, Julian C., Jokikokko, Erkki, Arnekleiv, Jo Vegar, Kennedy, Richard J., Niemela, Eero, Caballero, Pablo, Music, Paul A., Antonsson, Thorolfur, Gudjonsson, Sigurdur, Veselov, Alexey E., Lamberg, Anders, Groom, Steve, Taylor, Benjamin H., Taberner, Malcolm, Dillane, Mary, Arnason, Fridthjofur, Horton, Gregg, Hvidsten, Nils A., Jonsson, Ingi R., Jonsson, Nina, Mckelvey, Simon, Naesje, Tor F., Skaala, Oystein, Smith, Gordon W., Saegrov, Harald, Stenseth, Nils C., Vollestad, Leif Asbjorn
• Other Authors: Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences Oslo, Faculty of Mathematics and Natural Sciences Oslo, University of Oslo (UiO)-University of Oslo (UiO)-Faculty of Mathematics and Natural Sciences Oslo, University of Oslo (UiO)-University of Oslo (UiO), Norwegian Water Resources and Energy Directorate (NVE), Silvio O. Conte Anadromous Fish Research Center, United States Geological Survey Reston (USGS), Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences = Sveriges lantbruksuniversitet (SLU), Department of Mathematics Oslo, Norwegian Institute for Nature Research (NINA), Fisheries and Oceans Canada (DFO), Centre for Environment, Fisheries and Aquaculture Science Lowestoft (CEFAS), Écologie et santé des écosystèmes (ESE), Institut National de la Recherche Agronomique (INRA)-AGROCAMPUS OUEST, Direction de la Faune Aquatique, Ministère du Développement Durable, de l'Environnement, de la Faune et des Parcs du Québec, Freshwater Laboratory Pitlochry, Marine Scotland, Finnish Game and Fisheries Research Institute, University of Oulu, National Marine Fisheries Service, Northeast Fisheries Science Center, Fisheries Ecosystem Advisory Services, Marine Institute, Marine Research Institute, Freshwater Laboratory Field Station, Bothnian Bay Fisheries Research Station, Section of Natural History, Museum of Natural History and Archaeology, Norwegian University of Science and Technology Trondheim (NTNU), Norwegian University of Science and Technology (NTNU)-Norwegian University of Science and Technology (NTNU), Agri Food and Biosciences Institute, Sección de Biodiversidade, Servizo de Conservación da Natureza de Pontevedra, Consellería de Medio Rural-Xunta de Galicia, Institute of Freshwater Fisheries, Institute of Biology, Russian Academy of Sciences Moscow (RAS), Vilt og fiskeinfo AS, Remote Sensing Group, Plymouth Marine Laboratory, Cromarty Firth Fisheries Trust, Institute of Marine Research, Radgivende Biologer AS, Flødevigen Research Station (IMR), Institute of Marine Research Bergen (IMR), University of Bergen (UiB)-University of Bergen (UiB), Norwegian Research Council 183989/S30, Norwegian Water and Energy Directorate (NVE)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2014
• Subjects: Atlantic salmon; freshwater conditions; North Atlantic; phenology; sea surface temperature; smolt emigration; [SDV]Life Sciences [q-bio]; Salmo salar
• Online Access: https://hal.science/hal-01210202; https://doi.org/10.1111/gcb.12363

Migrations between different habitats are key events in the lives of many organisms. Such movements involve annually recurring travel over long distances usually triggered by seasonal changes in the environment. Often, the migration is associated with travel to or from reproduction areas to regions of growth. Young anadromous Atlantic salmon (Salmo salar) emigrate from freshwater nursery areas during spring and early summer to feed and grow in the North Atlantic Ocean. The transition from the freshwater (parr') stage to the migratory stage where they descend streams and enter salt water (smolt') is characterized by morphological, physiological and behavioural changes where the timing of this parr-smolt transition is cued by photoperiod and water temperature. Environmental conditions in the freshwater habitat control the downstream migration and contribute to within- and among-river variation in migratory timing. Moreover, the timing of the freshwater emigration has likely evolved to meet environmental conditions in the ocean as these affect growth and survival of the post-smolts. Using generalized additive mixed-effects modelling, we analysed spatio-temporal variations in the dates of downstream smolt migration in 67 rivers throughout the North Atlantic during the last five decades and found that migrations were earlier in populations in the east than the west. After accounting for this spatial effect, the initiation of the downstream migration among rivers was positively associated with freshwater temperatures, up to about 10 degrees C and levelling off at higher values, and with sea-surface temperatures. Earlier migration occurred when river discharge levels were low but increasing. On average, the initiation of the smolt seaward migration has occurred 2.5days earlier per decade throughout the basin of the North Atlantic. This shift in phenology matches changes in air, river, and ocean temperatures, suggesting that Atlantic salmon emigration is responding to the current global climate changes.