Brood size does not influence the behaviour or density of larval and juvenile smallmouth bass under parental care

We used fine scale observations of individual broods of smallmouth bass (Mi cropterus dolomieu) to ask whether brood size had an effect on feeding beha viour, agonistic behaviour, nearest-neighbour distance or brood density of larvae and juveniles. Developmental phase, and not brood size, provided the only significant effect on individual behaviour. The dispersion of broods in the nearshore zone of the lake increased throughout the parental care pe riod in response to both developmental phase and brood size. The density of fish in broods (number of fish/m(2) of lake surface/brood) declined sharpl y before metamorphosis and remained relatively constant throughout the rema ining parental care period. However, at any particular developmental phase, the density of fish in broods was unrelated to the total numbers of fish i n a brood. The observation of increasing dispersion of broods during parent al care while, at any developmental phase, the density of fish remains inde pendent of brood size has important implications for the ecology of young-o f-year smallmouth bass. The possible mechanisms governing this phenomenon m ay be similar to those proposed for schooling fish and the movements of lar ge migratory mammals.