Effect of fluctuating light intensity on molting frequency and growth of Litopenaeus vannamei

Experiments were conducted to investigate the effect of rhythmic fluctuation of light intensity on the molting and growth of Litopenaeus vannamei. Molting, growth performance, feeding and body composition of the shrimps were tested in one constant light intensity treatment (2700 lx, “CL”) and four rhythmic fluctuating light intensity treatments (2700 ± 600 lx, “FL1”; 2700 ± 1200 lx, “FL2”; 2700 ± 1800 lx, “FL3”; 2700 ± 2400 lx, “FL4”). The initial wet body weight of shrimp was 2.74 ± 0.00 g (mean ± S.E.). After a 45-day experiment, the weight gain (WG) and the specific growth rate (SGRd) of shrimps in FL3 treatment were significantly higher than those in other treatments (P < 0.05), which might be caused by high feed intake (FId) and food conversion efficiency (FCEd). Another reason for the better growth in FL3 was that the energy allocation for respiration was lowest and the energy allocation for growth was highest. These results suggest that suitable fluctuation of light intensity could promote the growth of L. vannamei. There was no significant difference in molting frequency (MF) between constant light intensity and four fluctuating light intensity treatments (P > 0.05). The value of crude lipid in FL1-4 treatments decreased compared with that in the constant light intensity treatment, because of the effect of the fluctuating light intensity.

► Growth of Litopenaeus vannamei in five light intensity treatments was tested.
► Suitable rhythmic fluctuation of light intensity could promote the growth.
► High FId and FCEd was one reason for the better growth.
► Higher energy allocation for growth was another reason for the better growth.