FISH MOVEMENT BEHAVIOR - VARIABILITY WITHIN AND BETWEEN GROUPS

The movement behaviour of mullet, Mugil cephalus (Linnaeus), an obligate schooling fish species, was recorded for individuals in small groups. Mean speeds and mean turning frequencies both declined significantly with increasing group size. Significant differences between groups were attributed to individual variation. However, within groups the movements of individuals were highly coordinated. As the size of fish schools increases, behavioural convergence mediated by the monitoring of companions rapidly masks individual variation and leads to the characteristic uniformity of such aggregations.