Does climate during embryonic development influence parr growth and age of seaward migration in Atlantic salmon (Salmo salar)?

Climatic conditions experienced by Atlantic salmon (Salmo salar) in their early development appear to affect parr size at the end of the first growth season and age at emigration from the nursery river. North Atlantic Oscillation indices (NAOIs) correlated positively with water temperature (degree-days) and discharge in the River Imsa during winter (January-April) 1976-2002, indicating a significant oceanic influence on the winter conditions in the river. Specific growth rate of Atlantic salmon parr during the first year of life and the proportion of one-year-old smolts correlated positively with water temperature, flow, and NAOI during February-April during the winter of egg incubation, but only NAOI was significant when cross-correlating the two series using a time difference of 1 year. Water temperature correlated significantly with the proportion of salmon cohorts smolting and migrating to sea at age-1. Such long-term effects of climate during early development may be more important than generally recognized.