Real-time glucose monitoring biosensor system assesses the effects of different environmental light colors on Nile tilapia stress response

Nile tilapia Oreochromis niloticus is an important aquaculture species worldwide, and understanding its behavior and growth performance under variable culture conditions is essential for optimizing culture. Light as an environmental factor profoundly affects fish development, growth, food consumption, hormone secretion, and other life processes. This study investigated the effects of different light colors (blue, green, and red) on the stress response of individually reared Nile tilapia using a wireless biosensor system for real-time glucose monitoring. The biosensor system effectively measured glucose concentration (stress indicator) by enzymatic oxidation, allowing continuous monitoring of fish eyeball interstitial sclera fluid (EISF), providing longer and more accurate data. Air exposure and ammonia exposure were used as stressors, and stress responses were monitored under different light colors. Nile tilapia exhibited lower quiescent blood glucose levels, lower blood glucose elevations, and faster stress recovery under blue light. Green light induced more significant glucose elevations during acute physical stress, but showed similar fluctuations to blue light during chronic chemical stress, indicating potential benefits for fish welfare. In contrast, whether exposed to air or ammonia, red light induced large fluctuations in blood glucose levels, which may be detrimental to the fish. The study highlights the importance of light color in influencing stress responses and recovery in Nile tilapia, providing valuable insights for improving aquaculture practices and promoting fish welfare.