1) The food and space utilization of 36 tropical reef fishes belonging to six families: Pomacentridae, Scaridae, Acanthuridae, Siganidae, Labridae, and Mullidae has been studied, Underwater observations and samplings of these reef fishes were carried out at Honmura and Nishiura reefs of Kucllierabu Island (30°28N', 130°10'E), Kagoshima prefecture, Japan.
2) In the Honmura reef area, the 36 studies species are all common fishes in the bottom layer.
3) The areas of rock and dead corals covered by small algae are utilized as feeding ground by these fishes. These habitats widely distribute over a large area of Honmura reef and are abundant in amall algae as well as small animals such as amphipods, copopods, isopods, decapods, polychaetes, and gastropods.
4) The main food of the pomacentrids, scarids, acanthurids, and siganids are small algae. Main preys of labrids and mullids are small ani~nalss uch as amphipods, copepods, decapods, polychaetes, and gastropods.
5) A fish of the pomacentrids occupies a territorial area which overlaps that of other individuals of the same family. Fishes of the other five families wander about over the reef area.
6) The pomacentrids fishes feed solitary, but those of the other five families feed in a mixed- or single-species group.
7) The pomacentrid fishes defend their territories against intruders which are potential foocl competitors such as pomacentrids, scarids, acanthurids, and siganids. Fishes of scarids, acanthurids, and siganids intrude, forming a group, to get food into the territories of pomacentrids. Fishes of labrids and mullids accompany with scarids and acanthuridst o feed on small animals uncovered from thier hiding habitat by the benefit of stirring caused by the algae feeding of other members in tile same group.
8) Each one of the 36 species feeds on different organisms in different feeding behavior to other ones, corresponding with the abundance and distribution of the food organisms in their feeding ground. In such manner of life, these fishes coexist competiting or associating with one another for food organisms.