Effects of Light Intensity on Growth Performance and Physiological Responses in Juvenile Mandarin Fish (Siniperca chuatsi).

Light intensity, a crucial environmental factor, significantly affects the growth and physiological state of fish. This study investigated the effects of different light intensities (0, 150, 450, 650, and 1000 lx) on juvenile mandarin fish (Siniperca chuatsi) over a 66-day period. All groups achieved 100% survival, indicating that light intensity did not significantly affect survival. However, growth performance measured by specific growth rate (SGR) and weight gain rate (WGR) was highest at 150 lx. Nutritional analysis showed that crude protein and crude fat content were highest in the 150 lx group, while moisture was lowest under these conditions. Digestive enzyme activities in the liver, stomach, and intestine peaked under low-to-medium light intensities, with the highest values observed at 150 lx. Plasma cortisol levels were significantly lower at 150-450 lx than in other groups, indicating reduced stress under these conditions. In contrast, plasma melatonin levels declined with increasing light intensity and were lowest at 1000 lx. Overall, an illumination level of 150 lx was most beneficial for enhancing growth, reducing stress, and optimizing digestive enzyme activity in juvenile mandarin fish. These findings provide valuable insights for optimizing aquaculture practices and improving fish welfare and production efficiency.