Synchrony in marine growth among Atlantic salmon (Salmo salar) populations

More synchronous growth was observed between close, than more distantly separated populations of Atlantic salmon (Salmo salar), during both the first and the second year at sea. The marine growth of seven Norwegian populations, located between 60°N and 70°N, were correlated with sea surface temperatures (SSTs) in the Barents Sea, the Norwegian Sea, and the North Sea, and it was found that growth correlated best with the water temperatures in the area located closest to their home river. Growth was also compared with three broad-scale climate indices (North Atlantic Oscillation (NAO), Atlantic Multidecadal Oscillation, and subpolar gyre), with the strongest relationship occurring with the NAO index. However, SSTs explained more of the variability than the climatic indices did. Growth increment for the first year, but not the second year, was higher for southern than northern populations, mainly because of later smolt migration to sea in the north, and hence, a shorter growth season. For multi-sea-winter fish, all populations except one had a negative trend in growth with years for both the first and the second year at sea. For the second year at sea, this was most pronounced after the beginning of the 1980s. This is in accordance with the negative trend in pre-fishery abundance of adult salmon during the same period. On observe plus de croissance synchronisee entre les populations adjacentes que plus eeloigneees chez le saumon atlantique (Salmo salar), tant durant la premiere que la seconde annee en mer. Nous avons mis en correlation la croissance en mer de sept populations norvegiennes, etablies entre 60°Net 70°N, et les temperatures de surface de la mer (SST) dans la mer de Barents, la mer de Norvege et la mer du Nord; la croissance est le mieux correlee avec les temperatures des sites situes le plus pres de leur riviere natale. Nous avons aussi compare; la croissance avec trois indices climatiques a grande echelle (l'oscillation nord-atlantique (NAO), l'oscillation atlantique multideecennale et le tourbillon subpolaire) et la relation la plus forte s'etablit avec l'indice NAO. Cependant, les SST expliquent une plus grande partie de la variabilite que les indices climatiques. L'increment de la croissance pour la premiere annee, mais non pour la seconde, est plus eleve pour les populations du sud que pour celles du nord, surtout a cause de la migration plus tardive des saumoneaux vers la mer dans le nord et ainsi, de la periode de croissance plus courte. Chez les poissons qui passent plusieurs hivers en mer, toutes les populations, sauf une, affichent une tendance negative de la croissance en fonction des annees, tant pour la premiere que pour la deuxieme annee en mer. Pour la deuxieme annee en mer, la tendance est plus prononceee apresle debut des annees 1980. Cela concorde avec la tendance negative dans l'abondance des saumons adultes pendant la meme periode. [Traduit par la Redaction]
Introduction Spatial synchrony in animal population fluctuations across space has puzzled biologists for centuries (Moran 1953; Ranta et al. 1997; Ripa and Ranta 2007). Such synchrony may arise from exogenous [...]