The ontogeny of schooling behaviour in the striped jack

The ontogeny of schooling behaviour was investigated in laboratory-reared striped jack Pseudocaranx dentex larvae and juveniles. Mean separation angle between nearest individuals averaged 78 and 82 degrees in 10- and 12-mm fish, respectively, and decreased to 57 degrees in 16-mm fish. In addition, interindividual distance decreased from three times body length in 12-mm fish to twice the body length in 16-mm individuals; this value continued to decrease gradually to 1.3 at 19 mm to 0.79 at 30 mm. Mutual attraction due to visual recognition was observed in 12-mm fish and increased with total length. The optokinetic response (R-o, the ability of a fish to keep station with moving patterns) first appeared in 4-6-mm larvae. In spite of the traditional emphasis of the importance of R-o in schooling behaviour, the onset of R-o was insufficient to result in school formation. The emergence of mutual attraction seems essential for the ontogeny of schooling. (C) 1998 The Fisheries Society of the British Isles.