Influences of light intensity and photoperiod on moulting and growth of Penaeus merguiensis cultured under laboratory conditions

The effects of light intensity (1, 750 and 75 1x) and photoperiod (P, 12L/12D and X/5D) on moulting and growth of Penaeus merguiensis were investigated over 12 weeks under laboratory conditions. Both light intensity and photoperiod significantly (P<0.05) influenced the percentage weight gain (PWG), but did not influence moult frequency or moult interval. Mean PWG of prawns cultured at 750 1x was 198.4%, significantly (P<0.01) higher than those cultured at 75 1x (168.1%). Imposing two light/dark cycles (7L/5D) in 24 h resulted in a significantly higher growth of prawns (P<0.05) than the normal photoperiod (12L/12D). Prawns cultured at 750 Ix had a lower food conversion ratio (FCR, 1.485) than those cultured at 75 1x (1.590, P<0.05). The effect of light intensity on prawn growth was found to be stronger and more immediate than that of photoperiod. There was no interaction between light intensity and photoperiod. Although not significantly different (P>0.05), prawns cultured at 750 1x tended to moult more frequently. Sexual dimorphism was not observed within the range of tested prawns. (C) 2003 Elsevier Science B.V. All rights reserved.