Abstract. The role of prolactin (PRL) in the neuroendocrine control of schooling behaviour and activity in the demoiselle Chromis viridis is analysed by administration of a prolactin‐releasing drug, metoclopramide (Paspertin®). In addition, the dependence of the activity state, schooling time, and colour changes on the administration of an epiphysial hormone, melatonin, is examined. Each substance tested affects schooling behaviour and activity by a different mechanism.