Release during night enhances survival of wild Atlantic salmon smolts

• Published in: Fisheries Management and Ecology
• Main Authors: Vollset, K. W., Barlaup, B. T., Normann, E. S.
• Other Authors: Norges Forskningsråd
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2017
• Subjects: Norway; Atlantic salmon; Salmo salar
• Online Access: http://dx.doi.org/10.1111/fme.12230; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Ffme.12230; https://onlinelibrary.wiley.com/doi/pdf/10.1111/fme.12230

Abstract The effect of nocturnal and diurnal releases on survival and migration of wild and hatchery‐reared Atlantic salmon, Salmo salar, L., smolts ( n = 82) was investigated by releasing acoustically tagged smolts at the lower end of the River Vosso, Norway. Hatchery smolts was registered in the estuary within hours of their release, whereas wild smolts migrated over a prolonged period. The time of estuary exit was affected by river discharge but not by time of release. Progression rates were slow through the estuary (0.25 BL /s ± 0.18 SD ) and fast through the fjord (1.80 BL /s ± 0.69 SD ), and they were not affected by the time of release or origin. Survival to the fjord was low (0%–15%). Survival was not affected by body length but was lower for wild smolts than for hatchery smolts, and survival of the former was lower when the fish were released in daylight.