Different reproductive strategies in a sex-changing coral reef fish Centropyge bicolor (Pomacanthidae)

Abstract

A model is developed which evaluates the reproductive advantage of staying female or changing sex and becoming a male, using field data for the angelfish C. bicolor. Changing sex can lead immediately to taking over a territory and mating with a harem, or it may involve a period of time as a bachelor which waits for a territory vacancy. Bachelor males carry an initial cost of little or no reproduction but on the death of a dominant male have a better chance than females of acquiring territories and haremmating success. The model predicts that to be a bachelor is better than to stay female up to a certain density of bachelors. The predicted frequency of bachelors agrees with their natural density in the area in which they occur. The model also predicts that under some conditions there will be no advantage in becoming a bachelor; this agrees with observations at three study sites.