Effects of light intensity and photoperiod on the growth and stress response of juvenile Nile tilapia (Oreochromis niloticus) in a recirculating aquaculture system

Light is an essential natural factor of fish growth and development. A light regime in indoor aquaculture is critical for sustainable fish production. This research aimed to investigate the effect of light intensity and photoperiod on the growth performance and stress response of Nile tilapia (Oreochromis niloticus), which is an important commercial species, in a recirculating aquaculture system (RAS). Fingerlings with an average weight of 5 ± 0.9 g were randomly assigned to nine 1.5 m3 tanks with 145 fish in each tank, cultured under different light intensities (1000, 2000, and 3000 lx) and photoperiods (12L:12D, 18L:6D, 24L:0D), and fed to apparent satiation twice a day for 160 days. The growth of tilapia subjected to 2000 lx was significantly better than that exposed to 1000 and 3000 lx (P < 0.05) as indicated by the final weight (351.17 ± 10.59 g), growth efficiency (0.77 ± 0.26), specific growth rate (2.65% ± 0.21% per day) and feed conversion coefficient ratio (1.30 ± 0.36). No significant difference was observed in the growth rate among different photoperiod groups (P > 0.05). Light intensity and photoperiod manipulation did not cause a significant chronic stress response in tilapia. This study demonstrated that light intensity, especially at 2000 lx, and photoperiod manipulation could stimulate the growth of tilapia in the RAS and significantly affect economic profitability. This study also served as an important reference for tilapia indoor aquaculture.