Advancing smolting to autumn in age 0+ Atlantic salmon by photoperiod, and long-term performance in sea water

摘要: Abstract Smolting in autumn age 0+ Salmo salar was improved by 2 months of short photoperiod an otherwise constant long regime. Four groups fry were reared under either constantlong (LD 17:7), or LD17:7 interrupted LD7:17 for one (1mo-short; July 27–September 1) (2mo-short; June 30–September 1), simulated natural day length (LDN). Bimodality size-frequency developed all August. Probability individual entering the upper-modal group (UMG) related positively to fork late June. The LDN regime had highest proportion both lower-modal fish (46% vs. 25–27%), and sexually mature males four (26% 10–12%). Smolt development 2mo-short group, but inferior normal spring smolts, as judged hypoosmoregulatory ability gill Na + K ATPase activity. Following transfer UMG a sea-cage November, exhibited best survival growth over winter. From onwards grew well, reaching harvest size (3–4 kg) August after 20 sea water. Mortality water 24% 28% 2mo- 1mo-short groups, 54% 67% constant-long groups. study indicated feasibility stabilising undesirable seasonal fluctuation commercial salmon production producing ‘off-season’ smolts 6 out-of-phase from regular smolts.