Study on the Adaptive Regulation of Light on the Stress Response of Mandarin Fish (Siniperca chuatsi) with Re-Feeding after Starvation

SIMPLE SUMMARY: Environmental factors have a significant impact on the feeding behavior, yield, and quality of Siniperca chuatsi. Previous studies of potential correlations between light and fish behaviors have mainly focused on phototaxis, changes to circadian rhythms, and growth and development. In the present study, at 11.15 ± 2.01 lx, S. chuatsi sustained relatively lower stress in response to re-feeding after starvation and digestive enzyme activities in the intestine were the highest, indicating that the light intensity was most suitable for re-feeding of S. chuatsi after starvation. Under light conditions, S. chuatsi only preys on fish, but it also preys on shrimp under dark conditions, due to weak light reducing the accuracy of hunting. Thus, under weak light, S. chuatsi is most likely to consume compound feed. Moreover, reducing the light intensity can increase the activity of digestive enzymes in the intestine while alleviating the stress response and facilitate successful domestication of S. chuatsi. Collectively, the results of the present study suggest that the suitable light intensity can accelerate the adaptation of S. chuatsi to stress caused by re-feeding. ABSTRACT: Light influences the stress response to environmental stimuli and feeding behaviors of Siniperca chuatsi and, thus, is an important regulator of normal growth and development. In this study, we first explored the important role of light on the digestive and stress capacity of S. chuatsi by studying the changes in physiological and biochemical indicators of S. chuatsi, taking the re-feeding after starvation as the constant environmental stimulus and the light intensity as the adjustable environmental stimulus. The activity of protease and lipase was generally higher in the stomach tissues than in the intestinal tissues, especially lipase, which was higher in stomach tissues under all light conditions, and the protease and lipase activity peaked in the stomach tissues of S. chuatsi at a light intensity of 18.44 ± 3.00 lx and in intestinal tissues at 11.15 ± 2.01 lx, respectively, indicating that greater light intensity increased the digestive capacity of stomach tissues, whereas lower light intensity facilitated the digestive capacity of intestinal tissues. The tissues of the gill, stomach, and intestine had relatively high activity of stress-related enzymes, whereas the tissues of the brain, kidney, liver, and plasma samples had relatively low activity of enzymes. Collectively, the results show that light intensity at 11.15 ± 2.01 lx promoted digestive capacity in the intestine and enhanced the anti-stress ability of S. chuatsi in response to stress induced by re-feeding after starvation. These findings should prove useful for artificial breeding of S. chuatsi.