A simulation model of collective motion of a fish group was presented to investigate the role of allelomimesis of fish individual in emergence of dynamically stable schooling behaviors.The present model was formulated based on the individual decision-making approach. Allelomimesis doing what your neighbors do was considered as the essential tactic of decision-making by which coherent collective behaviors such as schooling are generated. Besides the allelomimetic actions of individuals the collision avoidance actions are also another essential tactic. As a measure of the tactic of decision-making the ratio of contributions of allelomimetic and avoidance actions is adopted. It was investigated changing systematically value of the contribution ratio how and to what extent fish individuals mimic their neighbors so that the fish group shows the schooling behaviors. It was shown that the schooling behaviors generated using the optimal values of the ratio correspond to a self-organized critical state. The main purpose of the present modeling is to investigate whether the tactic of individual decision-making suited to generate good schooling behaviors works well also in maintaining dynamical stability of the fish school under emergent affairs. Emergent splitting of a school into two groups and flash expansion of a school were used as the emergent affairs. The extent of dynamical stability of a school was evaluated using two kinds of measures the recovery time period and the critical distance of splitting or expansion.It was found that the tactic suitable for schooling generates the dynamically stable response of the school to emergent affairs."

A simulation model of collective motion of a fish group was presented to investigate the role of allelomimesis of fish individual in emergence of dynamically stable schooling behaviors.The present model was formulated based on the individual decision-making approach. Allelomimesis, doing what your neighbors do, was considered as the essential tactic of decision-making by which coherent collective behaviors such as schooling are generated. Besides the allelomimetic actions of individuals, the collision avoidance actions are also another essential tactic. As a measure of the tactic of decision-making, the ratio of contributions of allelomimetic and avoidance actions is adopted. It was investigated changing systematically value of the contribution ratio how and to what extent fish individuals mimic their neighbors so that the fish group shows the schooling behaviors. It was shown that the schooling behaviors generated using the optimal values of the ratio correspond to a self-organized critical state. The main purpose of the present modeling is to investigate whether the tactic of individual decision-making suited to generate good schooling behaviors works well also in maintaining dynamical stability of the fish school under emergent affairs. Emergent splitting of a school into two groups and flash expansion of a school were used as the emergent affairs. The extent of dynamical stability of a school was evaluated using two kinds of measures the recovery time period and the critical distance of splitting or expansion.It was found that the tactic suitable for schooling generates the dynamically stable response of the school to emergent affairs."