LAUSR

Aim: The investigation evaluated the impact of varying photoperiods on the physiological regulation of stress pathway and the biochemical concentration of metabolites in hillstream trout, Opsarius bendelisis. Methodology: Different light phases were used in the present study to quantify their weight and chronic stress marker cortisol using enzyme-linked immunosorbent assay (ELISA). The behavior of the fish was investigated using the highly sophisticated software Ethovision XT 13 with a frame rate of 25 per sec. The fish’s lipid profiles were measured using gas chromatography-mass spectrometry (GC-MS). Results: The chronic marker of stress cortisol showed a relevant difference among the various regimes of photoperiod at P≤0.0046.The different observed behavior profiles, such as velocity distance traveled, also showed a significant difference at P<0.0001 in the different light-exposed durations. The 9-octadecenoic acid, methyl ester, (E)- (I), and hexadecanoic acid, methyl ester also showed a significant difference at P<0.05. Interpretation: Extended photoperiod lowers stress levels and influences fish behavior. The results of this investigation will offer fresh perspectives on cognitive-behavioral tests. Key words: Cortisol, ELISA, Opsarius bendelisis, Photoperiods, Stress behavior