EFFECTS OF PHOTOPERIOD AND LIGHT INTENSITY ON THE GROWTH, MUSCLE NUTRITION AND ECONOMIC PERFORMANCE OF MURRAY COD (MACCULLOCHELLA PEELII) IN THE RECIRCULATING AQUACULTURE SYSTEM

Light is an important environmental factor that affects fish growth, while there is limited research in recirculating aquaculture system. This study investigated the growth, muscle nutrition and economic performance of murray cod in the recirculating aquaculture system with different photoperiods (12L﹕12D, 15L﹕9D, 18L﹕6D, 21L﹕3D) and light intensities (1200 lx, 1500 lx, 1800 lx, natural light). The results showed that: (1) The final weight, daily weight gain and specific growth rate of 15L﹕9D group were significantly higher than those of other treatments (P<0.05), and the feed conversion ratio was significantly lower than the 12L﹕12D and 21L﹕3D groups (P<0.05). The final weight, daily weight gain and specific growth rate of 1500 lx group were significantly higher than those of other groups (P<0.05), and the feed conversion ratio was significantly lower than that of other groups (P<0.05). (2) The content of crude fat, total amino acids, and total essential amino acids of 15L﹕9D group were the highest. 1500 lx group had the highest content of crude fat and ash and the lowest content of moisture and crude protein. On the contrary, natural light group had the highest content of moisture and crude protein and the lowest content of crude fat and ash. (3) Although the 15L﹕9D and the 1500 lx group have invested relatively high costs, due to the fast growth and high output of the two groups, the total benefits, total net benefits, and benefit-cost ratios of the two groups significantly higher than other groups (P<0.05). In general, 15L﹕9D and 1500 lx are the best light condition for Murray cod in the RAS system, which provides a reference for the application of artificial lighting aquaculture.