Light Color and Intensity-Dependent Modulation of Phototactic Behavior Mediating Orientation Guidance in Schizothoracine Fishes

Visual cues are critical for orientation and migration in riverine fishes, providing potential mechanisms for behavioral guidance. This study investigated how light spectrum and intensity interact to modulate phototactic responses in two schizothoracine fishes from the upper Yalong River. Results showed Schizopygopsis malacanthus preferred blue light and avoided red light, with preferences shifting with flow intensity; Schizothorax kozlovi favored green light and avoided light-red light, with minimal flow impact. We propose that engineers build fishway entrances or ideal habitat attractors that prioritize low-intensity blue light (10 lx) and medium-intensity green light (50 lx), supplemented by medium-intensity blue light (50 lx). This study provides scientific evidence and application value for restoring fish habitats, fish passages, and fisheries.