Assessing Efficacy of Non-Lethal Harassment of Double-Crested Cormorants to Improve Atlantic Salmon Smolt Survival

Abstract Salmo salar (Atlantic Salmon) smolts are exposed to predation pressure as they migrate from freshwater into the estuary and near-shore marine environment. In particular, Phalacrocorax auritus (Double-crested Cormorants) are a predator of Atlantic salmon smolts during their estuary and near-shore migration. National Oceanic and Atmospheric Administration's (NOAA) National Marine Fisheries Services’ (NMFS) telemetry data collected prior to this study (1997–2003), suggest that smolts are being removed from the Narraguagus River on their downstream out-migration. This removal may be the result of Cormorant predation. We investigated whether smolt survival could be improved by disrupting normal Cormorant foraging activity by integrating passive smolt tracking and active harassment techniques. Smolt movement and usage of various portions of the estuary according to light condition and tidal stage were explored along with concurrent avian harassment. Although harassment only occurred in approximately 33...