"Behavioral Characterization of Downstream-Migrating Atlantic Salmon Smolts in the Estuary of the Penobscot River, Maine"

The estuary phase is critical in the Atlantic salmon, Salmo salar, downstream migration. This developmental stage is linked to behavioral and physiological changes that are adaptations for life at sea.  During migration, juveniles face novel predators and salinity changes that can increase risk of mortality.  While general patterns are well characterized, less attention has been paid to the individual behavior of the smolts moving through the estuary. In the Penobscot River, Maine, more than 2,000 Atlantic salmon juvenile fish have been acoustically tagged and released in the upper River in the last 10 years. Using an array of acoustic receivers throughout the estuary, we recorded individual fish movements through the estuary. We examined the times of movements, movement rate, and number of reversals. These patterns were analyzed in concert with environmental variables (temperature, flow and salinity) and individual covariates (e.g. size, developmental stage and physiological preparedness).  We used this data to characterize the behavior of downstream-migrating smolts in relation to survival probability in the Penobscot River.