Many surprises from tagging Atlantic salmon with pop-up satellite tags. Further north and east than we thought, more use of oceanic fronts, deeper dives and staying in colder water.
Left: Migrations of Atlantic salmon tagged in eight different geographic areas. Release locations post-tagging are shown by squares (from 11 northeast Atlantic river catchments and at-sea at Western Greenland). Crosses show the pop-up location of the tags. Right: Area use during the ocean migration of tagged Atlantic salmon, shown with lines and shades with colours representing salmon from seven different areas. Photo: Audun H. Rikardsen.
We attached 204 pop-up satellite archival tags to post-spawned salmon when they migrated to the ocean from seven European areas and maiden North American salmon captured at sea at West Greenland.
The study extended the known geographic area used by salmon during their migration in the North Atlantic Ocean and Barents Sea as reported by earlier studies based on conventional tagging and sampling surveys.
Individuals migrated further north and east than previously reported. The northernmost recordings were from the west of Svalbard at latitudes of nearly 80°. Individuals experienced temperatures down to 0 °C, or even slightly colder.
The salmon performed deep dives of several hundred meters. The deepest dive was to 870 m depth.
IMPORTANCE OF THE POLAR FRONTS
Salmon from different areas used different migration routes and ocean areas. Still, they consistently migrated to and aggregated in assumed highly productive areas at the boundaries between large-scale frontal water masses where branches of the North Atlantic current lie adjacent to cold polar water.
Individuals displayed increased diving activity near oceanographic fronts, emphasizing the importance of these regions as feeding areas.
SIMILARITIES AND DIFFERENCES AMONG POPULATIONS
The oceanic distribution differed among individuals and populations, but overlapped more between geographically proximate than distant populations. Dissimilarities in distribution likely contribute to variation in growth and survival within and among populations due to spatio-temporal differences in environmental conditions.
Climate-induced changes in oceanographic conditions will alter the location of frontal areas and may have stock-specific effects on Atlantic salmon population dynamics, likely having the largest impacts on southern populations.
This study was a result of an extensive collaboration between scientists from many institutes and countries; UiT The Arctic University of Norway, CEFAS UK, NINA Norway, Inland Fisheries Ireland, NOAA Fisheries Service USA, Laxfiskar Iceland, Servicio de Conservación de la Naturaleza de Pontevedra Spain, Technical University of Denmark, and NTNU Norway.
THE PUBLICATION IS OPEN ACCESS, AND CAN BE ACCESSED HERE:
Rikardsen, A.H., Righton, D., Strøm, J.F., Thorstad, E.B., Gargan, P., Sheehan, T., Økland, F., Chittenden, C.M., Hedger, R.H., Næsje, T.F., Renkawitz, M., Sturlaugsson, J., Javierre, P.C., Baktoft, H., Davidsen, J.G., Halttunen, E., Wright, S., Finstad, B. & Aarestrup, K. 2021. Redefining the oceanic distribution of Atlantic salmon. Scientific Reports 11: 12266.