Migration patterns and navigation cues of Atlantic salmon post‐smolts migrating from 12 rivers through the coastal zones around the Irish Sea

• Published in: Journal of Fish Biology
• Main Authors: Lilly, Jessie Marie, Honkanen, Hannele H., Rodger, Jessica R., del Villar, Diego, Boylan, Patrick, Green, Amy, Pereiro, Diego, Wilkie, Lorna, Kennedy, Richard, Barkley, Andrea, Rosell, Robert, Ó Maoiléidigh, Niall, O’Neill, Ross, Waters, Catherine, Cotter, Deirdre, Bailey, David, Roche, William, McGill, Ross, Barry, James, Beck, Samantha V., Henderson, Jim, Parke, Debbie, Whoriskey, Frederick G., Shields, Brian, Ramsden, Philip, Walton, Silas, Fletcher, Melanie, Whelan, Ken, Bean, Colin W., Elliott, Sophie, Bowman, Adrian, Adams, Colin E.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2023
• Subjects: Atlantic salmon; North Atlantic; Salmo salar
• Online Access: https://eprints.gla.ac.uk/308951/; https://eprints.gla.ac.uk/308951/1/308951.pdf

The freshwater phase of the first seaward migration of juvenile Atlantic salmon (Salmo salar) is relatively well understood when compared with our understanding of the marine phase of their migration. In 2021, 1008 wild and 60 ranched Atlantic salmon smolts were tagged with acoustic transmitters in 12 rivers in England, Scotland, Northern Ireland and Ireland. Large marine receiver arrays were deployed in the Irish Sea at two locations: at the transition of the Irish Sea into the North Atlantic between Ireland and Scotland, and between southern Scotland and Northern Ireland, to examine the early phase of the marine migration of Atlantic salmon smolts. After leaving their natal rivers’ post-smolt migration through the Irish Sea was rapid with minimum speeds ranging from 14.03 to 38.56 km.day-1 for Atlantic salmon smolts that entered the Irish Sea directly from their natal river, to 9.69 to 39.94 km.day-1 for Atlantic salmon smolts that entered the Irish Sea directly from their natal estuary. Population minimum migration success through the study area was strongly correlated with the distance of travel, populations further away from the point of entry to the open North Atlantic exhibited lower migration success. Post-smolts from different populations experienced different water temperatures on entering the North Atlantic. This was largely driven by the timing of their migration and may have significant consequences for feeding and ultimately survivorship. The influence of water currents on post-smolt movement was investigated using data from previously constructed numerical hydrodynamic models. Modelled water current data in the northern Irish Sea showed that post-smolts had a strong preference for migrating when the current direction was at around 283° (west-north-west) but did not migrate when exposed to strong currents in other directions. This is the most favourable direction for onward passage from the Irish Sea to the continental shelf edge current, a known accumulation point for migrating post-smolts. These ...