A beaugregory damselfish(Eupomacentrus leucostictus)population in Jamaica, W.I., was censured and revealed continuous changes in numbers of individuals for all size classes. The smallest size class, juveniles, was most abundant on the loose sand substratum while adults were common only in areas with numerous pieces of small rubble. The change in habitat from juvenile to adult is attributed to both selected mortality and active movement of the juveniles.