Migration pathways, speed and mortality of Atlantic salmon (Salmo salar) smolts in a Scottish river and the near-shore coastal marine environment

Lothian, A. J., Newton, M., Barry, J., Walters, M., Miller, R. C. and Adams, C. E. (2018) Migration pathways, speed and mortality of Atlantic salmon (Salmo salar) smolts in a Scottish river and the near-shore coastal marine environment. Ecology of Freshwater Fish, 27(2), pp. 549-558. (doi: 10.1111/eff.12369)

Abstract

Long-distance migration of Atlantic salmon (Salmo salar) is known to result in high levels of mortality. For a species experiencing global population decline, it is thus vital to better understand migration behaviour, both in the river and marine stages. Atlantic salmon smolts (n = 50) were tracked using acoustic telemetry in the River Deveron, Scotland, and adjacent coastal area. Higher rates of mortality were observed in the river (0.77% per km) than the early marine stage of migration (0.0% per km). Mortality likely resulted from predation. Higher swim speeds were recorded in the early marine stage compared with the river (marine = 7.37 ± 28.20 km/day; river = 5.03 ± 1.73 km/day [mean ± SD]), a potential predator avoidance behaviour. The majority of smolts leaving the river did so in darkness and on a flooding tide. Overall river and marine migration success were linked to nights of lower lunar brightness. Marine migration speed decreased with increasing environmental noise levels, a finding with implications for fisheries management. The migration pathway in the early marine environment did not follow obvious geographical features, such as the coastline. Thus, we suggest that early marine environment pathways are more influenced by complex water currents. These findings highlight factors that influence smolt migration survival and behaviour, areas on which future research should focus.

• Item Type: Articles
• Additional Information: This project was funded by The River Deveron Salmon Fishery Board, The Deveron, Bogie and Isla Rivers Charitable Trust, and Muiresk Fishings.
• Keywords: Ecology, aquatic science, ecology, evolution, behavior and systematics.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Barry, Dr James and Adams, Professor Colin and Newton, Dr Matthew
• Authors: Lothian, A. J., Newton, M., Barry, J., Walters, M., Miller, R. C., and Adams, C. E.
• College/School: College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
• Journal Name: Ecology of Freshwater Fish
• Publisher: Wiley
• ISSN: 0906-6691
• ISSN (Online): 1600-0633
• Published Online: 28 June 2017