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Novel insights into the marine phase and river fidelity of anadromous twaite shad Alosa fallax in the UK and Ireland

Davies, Peter; Britton, Robert J.; Nunn, Andrew D.; Dodd, Jamie R.; Crundwell, Charles; Velterop, Randolph; Ó’Maoiléidigh, Niall; O’Neill, Ross; Sheehan, Emma; Stamp, Thomas; Bolland, Jonathan


Peter Davies

Robert J. Britton

Charles Crundwell

Randolph Velterop

Niall Ó’Maoiléidigh

Ross O’Neill

Emma Sheehan

Thomas Stamp


© 2020 The Authors. Most research on anadromous fishes has been invested in their freshwater life-phases, resulting in a relatively sparse understanding of their spatial ecology during marine life-phases. However, understanding the marine dispersal of anadromous fishes is essential to identify threats and to implement conservation measures that fully encompass their lifecycle. The twaite shad Alosa fallax is an anadromous fish increasingly imperilled across its range due to pollution, harvesting, and impediments to freshwater migration, but little is known about its distribution and movements during its marine life-phase. Here, the application of acoustic telemetry provided novel insights into the coastal dispersal of twaite shad in the UK and Ireland during 2018–2019, and the freshwater entry of individuals during the 2019 spawning season. Of 73 twaite shad acoustic-tagged during their upstream migration in the River Severn in May 2018, 58 emigrated from the river. Twelve were subsequently detected 200 km to the south-west at the Taw–Torridge Estuary between July 2018 and April 2019, where estuarine movements up to 5.8 km inland occurred in summer, winter, and spring. One was subsequently detected in the Munster Blackwater Estuary (Ireland) and then in the River Severn, indicating a minimum movement distance of 950 km. Thirty-four (59%) of the emigrating individuals from 2018 re-entered fresh water in the rivers Severn (n = 33) and Wye (n = 2) in April and May 2019. These results suggest year-round use of estuarine and nearshore habitats by at least a subset of the twaite shad population during their marine phase, providing evidence of potential range overlap between populations that spawn in different areas in the UK and Ireland, which may be facilitated by substantial dispersal. The results also highlight the potential of telemetry for estimating freshwater and marine mortality, and the benefits of sharing detection data across networks.


Davies, P., Britton, R. J., Nunn, A. D., Dodd, J. R., Crundwell, C., Velterop, R., …Bolland, J. (2020). Novel insights into the marine phase and river fidelity of anadromous twaite shad Alosa fallax in the UK and Ireland. Aquatic conservation : marine and freshwater ecosystems, 30(7), 1291-1298.

Journal Article Type Article
Acceptance Date Mar 18, 2020
Online Publication Date Jun 4, 2020
Publication Date 2020-07
Deposit Date Jun 5, 2020
Publicly Available Date Jun 5, 2020
Journal Aquatic conservation : marine and freshwater ecosystems
Print ISSN 1052-7613
Electronic ISSN 1099-0755
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 30
Issue 7
Pages 1291-1298
Keywords Acoustic telemetry; Anadromous fish; Data sharing; Estuaries; Migration; Networks
Public URL
Publisher URL


Published article (803 Kb)

Copyright Statement
© 2020 The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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