The development of schooling behaviour in Atlantic herring Clupea harengus

The timing of the development of schooling behaviour in Atlantic herring Clupea harengus and the quantitative and qualitative evolution of such behaviour in the larval and post‐metamorphic stages were investigated with a simulation model and experimental observations of laboratory‐reared fish. Herring larvae started to develop schooling behaviour between the lengths of 35 and 40 mm. This coincided with the beginning of metamorphosis, characterized by ontogenetic changes which require a switch to a different antipredator strategy from that employed by early larvae, while providing the sensory and anatomical mechanisms necessary for the formation of schools. Schooling behaviour was established at the end of metamorphosis (50–55 mm) and its characteristics continued to evolve throughout the early juvenile stage. A critical period in terms of vulnerability to predation is expected between the end of the larval and beginning of the juvenile stages, before schooling behaviour is fully developed. The implications of some of the results for the methodology of future studies are also discussed.