Effects of LED spectrum on feeding, growth and energy distribution of juvenile Dicentrarchus labrax

Dicentrarchus labrax is an important economic fish in aquaculture in China. In the process of industrialized recirculating aquaculture, different spectral environments have important implications for the effects of feeding and growth. In this study, five different LED spectral processing groups of white light (λ_{400-780 nm}), red light (λ_{630 nm}), yellow light (λ_{595 nm}), green light (λ_{530 nm}) and blue light (λ_{455 nm}) were set in the seawater circulating aquaculture experimental system. The effects of five different LED spectra on feeding, growth and energy distribution of juveniles (29.91±0.39) g, (13.78±0.35 cm)) were studied. The results showed that the effects of different LED spectra on the feeding, growth and energy distribution of juveniles were significantly different. The red light group had the best growth of the juveniles (41.09±5.70) g, and the blue group had the poorest growth of the juveniles (36.02±4.18) g; the DGC (daily growth coefficient) of the blue group was significantly lower than the other groups, and the difference between the other groups was not significant; there were significant differences in the feeding rate of the three groups of LED spectrum treatment groups, and the red light group had the highest feeding rate. The results of insulin-like growth factor IGF-1 and IGF-2 showed that the expression of IGF-1 mRNA was highest in the white light group; the mRNA expression level of IGF-2 was highest in the yellow light group. In terms of energy distribution, the red light group has lower fecal energy and metabolizable energy, and has the highest feeding energy and growth energy; the blue light group has the highest fecal energy, lower feeding energy and metabolic energy, and the lowest growth energy. The ratio of RNA/DNA in the muscle and liver of juvenile fish showed that the RNA/DNA ratio of the liver in the blue light group was significantly higher than that in the other groups; the RNA/DNA ratio in the muscles of the blue light group and the white light group displayed significant difference and no significant differences existed among the other groups. The results showed that the red light Eurasian larvae had better feeding and growth performance, and the blue-spectrum larvae had poor feeding and growth performance, and the red-spectrum larvae had higher feeding energy and growth energy. Therefore, the red spectrum has a better promoting effect on the growth of juveniles , and the blue spectrum has an adverse effect on the feeding growth of juveniles. This study provides a reference for the ground-based industrialized recirculating aquaculture of the D. labrax, creating a suitable spectral environment for growth.