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Marine Ecology Progress Series

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MEPS 709:91-108 (2023)  -  DOI:

Survival of Atlantic salmon and sea trout smolts in transitional waters

Céline Artero1,*, Stephen D. Gregory1,2,9, William A. Beaumont1, Quentin Josset3,4, Nicolas Jeannot4,5, Alan Cole6, Ludivine Lamireau7, Elodie Réveillac8, Rasmus B. Lauridsen1

1Game & Wildlife Conservation Trust, River Laboratory, East Stoke, Wareham BH20 6BB, UK
2Centre for Conservation Ecology and Environmental Sciences, Faculty of Science and Technology, Bournemouth University, Talbot Campus, Poole, Dorset, BH12 5BB, UK
3Office Français pour la Biodiversité, Direction Recherche et Appui Scientifique, Service Conservation et Gestion Durable des Espèces Exploitées, rue des Fontaines, 76260 Eu, France
4MIAME - Management of Diadromous Fish in their Environment, OFB, INRAE, Institut Agro, Université de Pau & Pays Adour / E2S UPPA, 35042 Rennes Cedex, France
5Institut national de recherche pour l’agriculture, l’alimentation et l’environnement, moulin des Princes, 56179 Pont-Scorff, France
6Environment Agency, Horizon House, Deanery Road, Bristol BS1 5AH, UK
7Institut national de recherche pour l’agriculture, l’alimentation et l’environnement, 65 rue de Saint Brieuc, 35042 Rennes Cedex, France
8UMR 7266 LIENSs CNRS-LRU, La Rochelle Université, Institut du Littoral et de l’Environnement, 2 rue Olympe de Gouges, 17000 La Rochelle, France
9Present address: Cefas, Barrack Road, Weymouth, Dorset DT4 8UB, UK
*Corresponding author:

ABSTRACT: 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.

KEY WORDS: Acoustic telemetry · Cormack-Jolly-Seber model · CJS model · Migration speed · Early marine stage

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Cite this article as: Artero C, Gregory SD, Beaumont WA, Josset Q and others (2023) Survival of Atlantic salmon and sea trout smolts in transitional waters. Mar Ecol Prog Ser 709:91-108.

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