Growth Trends in Two Sea Winter Atlantic Salmon in Maine's Downeast Rivers over 50 Years

The status of endangered Atlantic Salmon in the United States is dismal, with populations in many rivers being entirely or functionally extinct. In the southern extent of their range in North America, Atlantic Salmon stocks consist predominantly of fish that spend two years at sea (2SW). While abundance of one sea winter (1SW) spawners has oscillated and declined in recent decades, declines have been much more severe among 2SW spawners. Since the 1950s, both anglers and Maine's state agencies have collected Atlantic Salmon scales from returning individuals to monitor populations in the Dennys, Narraguagus, Machias, East Machias, and Pleasant Rivers. Scale samples from over 1000 adults were measured and proportional back-calculation methods were used to estimate smolt size, first sea year growth, and second sea year growth. In addition to characterization of age composition, we examined changes in smolt size and ocean growth, specifically during the second year at sea, from the 1950s to the mid-1990s in 2SW Atlantic Salmon from Maine's Downeast region. Intercirculi distances were used to assess seasonal ocean growth in relation to changing environmental conditions over the time series.