Effect of Photoperiod on Growth of Trout (Oncorhynchus mykiss) in Cold Ambient Sea Water

Abstract

The effects of four photoperiod regimes on growth performance of the rainbow trout (Oncorhynchus mykiss W.) in cold ambient seawater conditions were compared in indoor seawater tanks (salinity 18 g/l; 6-8 degrees C) in January-February. The photoperiods were the natural photoperiod (10 h light: 14 h dark), 20 h light:4 h dark, 16 h light:8 h dark, and 0 h light:24 h dark. Fish were fed a diet consisting of 47% protein, 20% fat, 11% ash, and 8.5% moisture. At the end of eight weeks, the relative growth rate and feed intake were significantly higher in fish exposed to 20L/4D than in other photoregimes. Total protein intake (g), protein retention (%), and N content in fish (%) significantly improved with the increase of light hours, indicating that optimal growth in the study conditions is obtained in extended light regimes (20L/4D) or 16L/8D).