Migration of Atlantic salmon (Salmo salar) smolts in a large hydropower reservoir

Migration rates, delay, timing, and success of acoustic-tagged Atlantic salmon (Salmo salar) presmolts (n = 120) and smolts (n = 57) are reported as they moved through the large Mactaquac Generating Station (MGS) reservoir and subsequently the lower Saint John River (SJR). The potential relationship between fish movements and the MGS operations was examined directly and via a hydrodynamic model. Migration rates were 15.4-29.3 km.day(-1) within the river sections and 5.0-13.3 km.day(-1) through the reservoir, a significant reduction of 32%-57%. Migratory timing was temporally mismatched with dam operations such that only a few (n = 3) smolts had the option of dam passage via spill. Migration success estimated as apparent survival was high through the reservoir (81%-100%), declined by 8%-32% during passage at the MGS, and additional losses (27%-55%) occurred during the migration to the lower SJR, such that overall survival to the estuary for the groups tagged as autumn presmolts was 61%-65%, and survival for those tagged as spring smolts was 6%-10%.