How do social hierarchies emerge from physical interactions? We address this through high-resolution 3D tracking of zebrafish aggressive behavior by tracking the head, pectoral fin, and tail of each fish throughout 5-hours recordings. Wild-type zebrafish pairs exhibit a clear temporal progression in social behavior. During initial interactions (first 50 minutes), fish engage in mutual aggressive displays with symmetric gaze patterns; both fish orient toward each other with similar frequency. As dominance relationships stabilize, gaze asymmetry emerges: the subordinate fish consistently orients toward the dominant individual, while the dominant fish shows reduced attention to its subordinate. In contrast, mecp2 mutant pairs fail to establish this characteristic asymmetry, maintaining symmetric gaze patterns throughout the recording period. This suggests that normal dominance establishment requires intact mecp2 function, and that gaze asymmetry serves as a quantitative behavioral signature of hierarchy formation in zebrafish social interactions.