Leadership and collective motion in black neon tetra schools: does the task matter?

Many fish schools are regarded as leaderless, where any individual can guide the direction of group motion at any given moment. We conditioned a fish school of black neon tetra (Hyphessobrycon herbertaxelrodi) to find food in aparticular location, while another group swam freely with no particular goal. Groups were composed of similar individuals in terms of body size, task knowledge and hunger level. Our hypothesis was that leadership would be less stable when fish were conditioned than when they were not. Although stability tended to be greater in the conditioned group, the hypothesis was not confirmed, as both groups showed asimilar degree of leadership stability. Leadership was not entirely random and some individuals took the lead more often than others. Leaders tended to be at the front of the school and their tendency to lead was loosely related to higher swimming speeds, and not related to task knowledge.