Survival of Atlantic salmon and sea trout smolts in transitional waters

• Published in: Marine Ecology Progress Series
• Main Authors: Artero, Celine, Gregory, Stephen, Beaumont, William A., Josset, Quentin, Jeannot, Nicolas, Cole, Alan, Lamireau, Ludivine, Réveillac, Elodie, Lauridsen, Rasmus B.
• Other Authors: Game & Wildlife Conservation Trust, Faculty of Science and Technology, Bournemouth University Poole (BU), The Game and Wildlife Conservation Trust, Service conservation et gestion durable des espèces exploitées (OFB SEEX), OFB Direction de la recherche et de l’appui scientifique (OFB - DRAS), Office français de la biodiversité (OFB)-Office français de la biodiversité (OFB), Pôle OFB-INRAE-Institut Agro-UPPA pour la gestion des migrateurs amphihalins dans leur environnement (MIAME), Université de Pau et des Pays de l'Adour (UPPA)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Office français de la biodiversité (OFB)-Institut Agro Rennes Angers, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), Unité Expérimentale d'Ecologie et d'Ecotoxicologie Aquatique - U3E (Rennes, France) (U3E), Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Environment Agency, LIttoral ENvironnement et Sociétés (LIENSs), Institut national des sciences de l'Univers (INSU - CNRS)-La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: CCSD 2023
• Subjects: Acoustic telemetry; Cormack-Jolly-Seber model; CJS model; Migration speed; Early marine stage; [SDE]Environmental Sciences; Atlantic salmon; Salmo salar
• Online Access: https://hal.inrae.fr/hal-04127075; https://doi.org/10.3354/meps14278

International audience Monitoring the first seaward migration of juvenile salmonids, known as smolts, is challenging because there is limited tracking technology suited to their small size. Nevertheless, for their management and conservation purpose, it is critical to understand this phase of their life cycle when they adapt to increased salinity, novel predators and new prey. Smolts of 2 species, Atlantic salmon Salmo salar and brown trout Salmo trutta , were acoustically monitored at 4 study sites, together with biotic and abiotic parameters, to estimate and explain their survival during their estuarine migration to sea. The 2 species exhibited different levels of survival during this seaward migration, with a higher survival for trout smolts. For both species, survival was similar among 3 of the 4 sites. Migration speed and migratory distance influenced smolt estuarine survival, but body length, body condition, sex, age, and environmental parameters (temperature, salinity, dissolved oxygen) did not. Migration speed, potentially reflecting smolts’ capacity to avoid predators or escape dangerous areas, had a positive effect on their survival. Increased distance negatively influenced estuarine survival, which could lead to lower survival rate in the River Frome Estuary where orientation is more difficult for smolts due to widely separated environmental cues. Overall, smolt survival through estuaries was estimated between 51 and 97% among 4 populations, suggesting that estuaries are variably challenging environments for migrating smolts, accounting for non-negligible early marine survival. Understanding which estuaries have low survival and why is imperative to prioritise management actions.