A novel automatic release cage increases survival of Atlantic salmon (Salmo salar) smolts released at night

AbstractTrap‐and‐transport of migratory fish is commonly used to bypass in‐river obstructions. On the River Conon in Scotland, Atlantic salmon (Salmo salar) smolts are transported around two hydropower facilities. Smolt release occurs during daylight, when predation rates can be high. A novel automatic release cage (ARC) was designed to release smolts at night. Smolts were fitted with acoustic tags (n = 99) to compare survival. High post‐release mortality was identified in the day‐release group, with night‐release survival >40% higher. ARCs can provide fishery managers with a cost‐effective and reliable method of improving smolt survival.