Harem structure of the protogynous angelfish, Centropyge ferrugatus (Pomacanthidae)

Social structure of the protogynous angelfish, Centropyge ferrugatus, was examined on the coral reefs of Sesoko Island, Okinawa, Japan. Each individual male monopolized a harem of 1-6 females. Harems could be categorized as linear-type or branching-type based upon spatial and dominance relationships among the females. A linear harem consisted of different-sized females whose home ranges overlapped each other with a linear dominance order based on body size. Branching harems were composed of two linear sub-groups dividing a male's territory. Females of similar size did not have overlapping home ranges, which resulted in branching harems. These two systems appear to be a result of competition for opportunities of sex change, as only the largest fish of a harem (or a sub-group) can become a male. Comparison of the harem structures of some reef fishes suggests that the two harem structures may occur broadly in protogynous haremic fishes.c/o Prof. T. Kuwamura