The development of shoaling behaviour in the European minnow, Phoxinus phoxinus

The effects of development and disturbance on schooling and shoaling were observed in laboratory‐raised minnows. Both behaviours were present at the onset of free swimming. Shoaling increased to become the most important behaviour by 3 weeks after emergence from gravel, while the main increase in schooling behaviour occurred at 4 weeks. These changes were accompanied by rises in elective group size and in the number of following responses, and by a decrease in nearest neighbour distance. The increases in social behaviour were observed at an earlier stage in the same minnows threatened by a standard net chase. The main increase in schooling in disturbed minnows took place between 3 and 4 weeks after emergence; after this time schooling became the dominant behaviour. Disturbed fish were also more likely to follow another minnow during an encounter.