4.10. Light Dark Box Assay

The light–dark preference test was performed based on a protocol modified from a previous study [43]. The light-and-dark box test was performed in a water tank with inner dimensions measuring 21 × 10 × 7.5 cm. In this experiment, half of the mating tank was taped with black tape and the other half was illuminated. Video recordings started after an acclimation time of 5 min, for the tester fish to explore the tank. Videos were recorded from the top viewpoint of the tank for 6 min. The frequency entering into the light zone and the total freezing time in the light zone were quantified.