Photoperiodic manipulation and its use in the all year round production of Atlantic salmon, Salmo salar

• Main Author: Duncan, Neil
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of Stirling 1996
• Subjects: Atlantic salmon; Photoperiodism; Fishery management; Salmo salar
• Online Access: http://hdl.handle.net/1893/21632; http://dspace.stir.ac.uk/bitstream/1893/21632/1/Duncan-thesis.pdf

The Atlantic salmon tSalmo safar) has two developmental processes which are clearly seasonal; smoltification is restricted to the spring and maturation to late autumn. In the farming industry the seasonality of juvenile production is primarily responsible for the seasonal production in market-sized fish. Both smoltification and maturation appear to be controlled by mechanisms timed by photoperiod. This thesis investigates the effects of photoperiod on smoltification and maturation. The performance of both out-of-season eggs and particularly smolts are closely examined and the possible application of photoperiod techniques in the industry discussed. Both potential SI and S2 parr were subjected to natural photoperiods or a range of artificial photoperiods under constant and ambient temperature conditions. S I and S2 smolts reared under natural photoperiods were transferred to sea water during April and May. A 2-3 month period of short days followed by a period of long days was observed to advance smoltification; 0+ and 1+ smolts were transferred to sea during December (4 month advance) and October (6 month advance), respectively. A 12 month seasonal photocycle delayed by 3 months delayed smoltification by 2 months. Out-of-season smolts were produced in January, March, April, May, June, July, October, November and December. All groups of out-of-season smolts exhibited the same growth potential as natural smolts. The different transfer date of out-of-season smolts therefore resulted in different harvest periods compared to natural smolts. The age at maturity of out-of-season smolts was positively related to the length of the seawater growing period prior to the completion of maturation. Out-of-season smolts exhibited increased maturation in association with an increased size (compared to natural smolts) for a particular time of year. These large maturing fish were generally harvested as superior salmon prior to flesh deterioration. Mortality during the first month in sea water was significantly higher in a number of ...