Atlantic Salmon Migration and Survival Dynamics

Atlantic salmon undertake a complex diadromous life cycle that links freshwater, estuarine and marine environments. Beginning as juveniles in natal rivers, smolts undergo physiological transformations that prepare them for the transition to saline waters. During estuarine passage, survival is influenced by flow regimes, temperature and physiological condition. Once at sea, post-smolts and adults disperse widely, exhibiting individual variation in horizontal and vertical movements as they exploit feeding grounds and avoid predation. Survival dynamics are shaped by size-selective mortality, predation by fish and marine mammals, oceanographic conditions such as fronts and mixed-layer depth, and anthropogenic pressures including dams, climate change and aquaculture interactions. Returning adults must navigate back to their river of origin, where cumulative mortality at sea and in coastal corridors contributes to population declines. Advances in acoustic and satellite telemetry have illuminated migration pathways, refined survival estimates and identified critical bottlenecks, informing conservation and management strategies across the North Atlantic range.

Research from Nature Portfolio

Recent studies using pop-up satellite archival tags have revealed spatially structured mortality patterns in adult salmon, with higher predation and total mortality rates recorded among southern populations compared with northern stocks. Endothermic fish emerged as the principal predators in key feeding areas, notably the Gulf of St. Lawrence and the Bay of Biscay–Irish Shelf region. Variability in ocean survival corresponds with ongoing declines in southern populations, emphasising the need for region-specific management interventions. Complementary work tracking post-spawners has extended the known oceanic range of Atlantic salmon, highlighting frequent visits to oceanographic fronts north and east of traditional routes. Individual fidelity to frontal zones during winter underscores their importance as feeding habitats, while inter-population differences in distribution point to stock-specific exposure to changing ocean conditions. These findings stress the potential impact of climate-driven shifts in frontal locations on the growth, survival and recruitment of distinct salmon populations.

Atlantic Salmon Migration and Survival Dynamics publication trend

The graph below shows the total number of articles in atlantic salmon migration and survival dynamics across all publications each year (not limited to Nature Index journals).

Technical terms

Smolt: A juvenile salmon undergoing physiological changes, including increased gill Na⁺,K⁺-ATPase activity, that enable osmoregulation in seawater.

Post-smolt: A salmon that has successfully transitioned to the marine environment and enters the early oceanic growth phase.

Pop-up satellite archival tag (PSAT): A device attached to fish that records depth, temperature and light data and detaches to transmit information via satellite.

Estuary: The transitional zone where freshwater from rivers mixes with saltwater, presenting unique hydrodynamic and physiological challenges.

Telemetry: The remote measurement and transmission of data on animal movements and behaviour, typically using acoustic or satellite-based tags.

References

1. A Synthesis of Tagging Studies Examining the Behaviour and Survival of Anadromous Salmonids in Marine Environments. PLOS ONE (2012).
2. Linking Behavior, Physiology, and Survival of Atlantic Salmon Smolts During Estuary Migration. Marine and Coastal Fisheries (2015).
3. Ocean predation and mortality of adult Atlantic salmon. Scientific Reports (2019).
4. Redefining the oceanic distribution of Atlantic salmon. Scientific Reports (2021).
5. Acoustic telemetry predation sensors reveal the tribulations of Atlantic salmon (Salmo salar) smolts migrating through lakes. Ecology Of Freshwater Fish (2021).
6. Counterintuitive active directional swimming behaviour by Atlantic salmon during seaward migration in the coastal zone. ICES Journal of Marine Science (2021).