An Updated Ecology of Atlantic Salmon ( Salmo salar ) at Sea

ABSTRACT Atlantic salmon have had a key role in European and North American oceans and human societies. Salmon are exploited and observed in rivers and along coasts, but there has always been great interest in knowing where salmon are going when they are at sea. Advances in electronic tagging and tracking, isotopic methods, and genetics have helped unravel a new understanding of salmon at sea. Ocean warming and changes to the Atlantic and Arctic food webs appear to be having an impact on the condition of salmon and their growth, survival, and age at maturity. Ultimately, salmon are threatened during their marine phase as the marine migration and major shifts in ocean currents, sea ice, and isotherms are apparently altering the distribution and abundance of their predators and prey at sea. However, there is still a paucity of knowledge about the relative importance of the different threats to Atlantic salmon at sea, particularly when comparing different regions and life stages (i.e. post‐smolts, sub‐adults, kelts). We argue that these knowledge gaps continue to limit effective management to curtail declining marine survival, and conclude with a series of key questions for the species in its marine phase.