How much piranhas are there in a pack?

Piranhas are social fish and typically live in groups called shoals or schools. The size of these groups can vary widely, from as few as six to as many as hundreds of individuals. Piranhas exhibit complex social behaviours within their groups, such as cooperation, coordinated hunting, defence against predators, and the establishment of a dominance hierarchy. The composition of these groups may also vary over time, particularly as a result of competition for resources, predator avoidance, or seasonal factors.