Evidence of long-distance coastal sea migration of Atlantic salmon, Salmo salar, smolts from northwest England (River Derwent)

Amy Green,Richard Kennedy,Philip Ramsden,Niall O’Maoiléidigh,Brian Shields,Peter Klimley,William Roche,Hannele M Honkanen,James Barry,Diego Del Villar-Guerra,Fred Whoriskey,Melanie Fletcher,Colin E Adams,Silas Walton,Robert Rosell

doi:10.1186/s40317-022-00274-2

Abstract

BackgroundCombining data from multiple acoustic telemetry studies has revealed that west coast England Atlantic salmon (Salmo salar L.) smolts used a northward migration pathway through the Irish Sea to reach their feeding grounds. Hundred Atlantic salmon smolts were captured and tagged in May 2020 in the River Derwent, northwest England as part of an Environment Agency/Natural England funded project.ResultsThree tagged smolts were detected on marine acoustic receivers distributed across two separate arrays from different projects in the Irish Sea. One fish had migrated approximately 262 km in 10 days from the river mouth at Workington Harbour, Cumbria to the northernmost receiver array operated by the SeaMonitor project; this is the longest tracked marine migration of an Atlantic salmon smolt migrating from the United Kingdom. This migrating fish displayed behaviours which resulted in fast northward migration. The remaining two fish were detected on a receiver array operated by a third project: the Collaborative Oceanography and Monitoring for Protected Areas and Species (COMPASS).ConclusionThese detections further provide evidence that migration to reach marine feeding grounds of at least a proportion of salmon smolts from rivers draining into the Irish Sea is northerly, though without a southern marine array it is impossible to conclude that this is the only route. The pattern of these detections would not have been possible without the collaborative efforts of three distinct and separately funded projects to share data. Further work is required to fully understand migration trajectories in this species on the west coast of the British Isles.

Highlights

Combining data from multiple acoustic telemetry studies has revealed that west coast England Atlan‐ tic salmon (Salmo salar L.) smolts used a northward migration pathway through the Irish Sea to reach their feeding grounds
We show that Atlantic salmon smolts once entering the Irish Sea took a northern pathway suggesting a northern trajectory towards the North Channel, giving them access to the more open North Atlantic
In total, 100 Atlantic salmon smolts were captured using in the upper reaches of the River Derwent, northwest England

Summary

Introduction

Combining data from multiple acoustic telemetry studies has revealed that west coast England Atlan‐ tic salmon (Salmo salar L.) smolts used a northward migration pathway through the Irish Sea to reach their feeding grounds. The former study approach can provide important, spatially explicit, but point source data on the presence of migrating salmon [17,18,19] This approach has shown us that salmon emanating from rivers in southern Europe migrate north to marine feeding grounds in the Norwegian Sea and/or to the north-west Atlantic, to the seas off west Greenland [1, 3, 20]. Typically using fixed position, continuous monitoring acoustic receivers and fish tagged with acoustic transmitters, have rapidly become a common method to investigate fish migration patterns (large and small), site fidelity and diel and seasonal movements [17,18,19] through both freshwater and marine environments This technique has the advantage that it can provide highly precise spatial information and more precise migration pathways. Collaboration amongst global and regional projects, often with differing primary aims, allow for fish migration information in the spatially extensive marine environments to be obtained in a more cost-effective way [21, 22]

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