Seawater growth and maturation of Atlantic salmon (Salmo salar) transferred to sea at different times during the year
2002
Duncan, N.J. | Thrush, M.A. | Elliott, J.A.K. | Bromage, N.R.
The use of photoperiod manipulation to alter the timing of seawater transfer of groups of salmon is a now common farming practice in Scotland. The present study was undertaken to examine and compare the seawater performance of out-of-season smolts with in-season smolts. A total of 12 groups were transferred to three different sea sites during May, June (three controls), January, March, October and November (nine out-of-season groups). At the two commercial sites, production times were similar ranging from 16 to 19 months to produce market-sized fish ranging from 2.3 to 3.8 kg. Different growth profiles were observed between groups and it was considered that this may be the result of the different photoperiod and temperature profiles experienced by the fish when transferred from the hatchery to the sea site. Percentage maturation in the different groups ranged from 9.2% to 98%. Maturation clearly increased with increasing growing period prior to the completion of maturation and two sites exhibited regressions (coefficient of determination R2 = 0.64 and 0.98) between percentage maturation and days from transfer to completion of maturation. The data from this study show the performance of out-of-season smolts with emphasis on growth and maturation. Overall growth is similar to natural smolts and maturation can be reduced or increased depending on transfer date. This information provides the salmon industry the opportunity to produce a year round supply of marketable fish of consistent size and quality.
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