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

Trap-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.

Automated summary

Trap-and-transport is commonly used for migratory fish to bypass river obstructions. The study conducted on the River Conon in Scotland found that the survival rate of Atlantic salmon smolts released at night using the novel automatic release cage (ARC) was over 40% higher than those released during daylight. This suggests that ARCs can be a cost-effective and reliable method for fishery managers to improve smolt survival.