Effect of LED spectrum on the vision, appetite, and growth of red seabream (Pagrus major)

Fish perceive different types of light, and the optimal light regime (intensity, spectrum, photoperiod) for growth, development, or reproduction varies across different species. Physiologically, the retina of the eye converts light into electrical signals and sent to the brain, with the hypothalamus producing endocrine hormones stimulating responses such as feeding behavior and appetite suppression or incitement. In the current study, the effects of various LED spectrum on the vision, appetite, and growth of red seabream (Pagrus major) were investigated. Cylindrical tanks equipped with LED covers emitting red (660 nm), green (518 nm), blue (450 nm), and white (full spectrum) light (all under 150 lx illumination) were used for the experimental groups. Photoperiod was set at 12 L: 12D cycle. Initially, red seabream (P. major) weighed 123.07 ± 15.25 g. After 12 weeks, fish reared under blue LED light weighed the most at 336.61 ± 63.11 g, followed by green (318.95 ± 62.06 g), white (308.16 ± 47.13 g), and red (271.32 ± 45.15 g). Changes in the retinal structure indicated that the red LED experimental group developed thinner retinas, whereas the blue LED group had the thickest retinas (P < 0.05). Rh1, Rh2A, Rh2B, and LWS mRNA expressions were highest in the red experimental group, while SWS2 was highest in the blue experimental group (P < 0.05). The blue experimental group exhibited significantly higher levels of appetite-promoting peptides, whereas the red experimental group had higher levels of appetite-suppressing peptides (P < 0.05). Gene expressions of HSP70 and SOD expressions, related to oxidative stress, were elevated in the red experimental group (P < 0.05). These results suggest that blue light enhances appetite and growth without causing retinal damage, while exposure to red light had the opposite effect. Thus, the findings illustrated that blue light can be used as a controlled lighting strategy for enhanced red seabream (P. major) aquaculture production.