<![CDATA[Light is a fundamental environmental factor shaping animal behavior, yet its role in structuring behavioral regimes across intensity gradients remains poorly understood. This study investigated the effects of light intensity on locomotor activity and behavioral fragmentation in Danio rerio under controlled experimental conditions. Behavioral responses were quantified using swimming speed and stop frequency, representing locomotor intensity and behavioral fragmentation, respectively. Data were analyzed using linear mixed-effects models, generalized linear mixed models, polynomial regression, and random forest classification. All light treatments significantly increased swimming speed relative to the control (p < 0.001), with the strongest response observed under white LED illumination. At the same time, stop frequency decreased significantly under illuminated conditions, particularly under red light (p < 0.01). Polynomial regression revealed a strong non-linear relationship between light intensity and swimming speed (R² = 0.57, p < 0.001), whereas stop frequency showed no significant intensity-dependent trend. Random forest analysis identified light intensity as the most influential predictor of behavioral state. Behavioral classification further revealed distinct hypoactive, efficient, hyperactive, and fragmented regimes across the light-intensity gradient. These findings demonstrate that light intensity structures discrete non-linear behavioral regimes rather than simple linear responses in zebrafish]]>
