The benefits of merging passive and active tracking approaches: new insights into riverine migration by salmonid smolts

Chavarie, L., Honkanen, H., Newton, M., Lilly, J. M., Greetham, H. R. and Adams, C. E. (2022) The benefits of merging passive and active tracking approaches: new insights into riverine migration by salmonid smolts. Ecosphere, 13(5), e4045. (doi: 10.1002/ecs2.4045)

Abstract

The process of smolting is a critical phase in the life cycle of anadromous salmonids, and it has been associated with substantial rates of mortality. Survival during freshwater and marine migration is known to have population-level effects; thus, an understanding of the patterns of mortality has the potential to yield important insights into population bottlenecks. Despite important advancements in tracking techniques, the specifics of mortality events in anadromous salmonids during their initial migration to sea remain somewhat elusive. Here, we develop a framework combining spatial and temporal detections of smolt riverine migration from two tracking techniques, which enable inferences to be made about mortality locations, causes, and rates. In this study, we demonstrate that during their initial riverine transitional phase, smolts were particularly vulnerable to predators. Specifically, avian predation appeared to be the main cause of mortality (42%), although piscine predation events were not trivial (14%). Our results suggested some direct and indirect tagging-induced mortality (e.g., through increased predation vulnerability), which highlights the importance of determining tagging mortality in a telemetry study to ensure adequate interpretation of migration success. Overall, by estimating migration loss and its variability, our study framework should help to guide management actions to mitigate the widespread population declines these species are currently facing.

• Item Type: Articles
• Additional Information: This work was part of the SeaMonitor project funded by the European Union INTERREG VA Programme award number IVA5060.
• Keywords: Acoustic tags, anadromous, Atlantic salmon, mortality, predation, river, sea trout, small‐scale behavior, telemetry.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Honkanen, Dr Hannele and Lilly, Jessie Marie and Adams, Professor Colin and Greetham, Ms Hannah and Chavarie, Dr Louise and Newton, Dr Matthew
• Authors: Chavarie, L., Honkanen, H., Newton, M., Lilly, J. M., Greetham, H. R., and Adams, C. E.
• College/School: College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
• Journal Name: Ecosphere
• Publisher: Wiley
• ISSN: 2150-8925
• Published Online: 12 May 2022
• Copyright Holders: Copyright © 2022 The Authors
• First Published: First published in Ecosphere 13(5): e4045
• Publisher Policy: Reproduced under a Creative Commons License