CHAPTER 5 – The Ecological Context of Reproductive Behavior

This chapter focuses on the reproductive behavior of coral reef fishes. Over the past 20 years, population-level studies of coral reef fishes have shifted from simple comparisons between coral reefs and terrestrial systems, to the patterns unique to marine and coral reef communities. This shift in attention of coral reef ecologists is reflected in the development of marine ecological theory that currently emphasizes the dynamics of open populations and the sources of recruitment fluctuations, including the possibility of recruitment limitation on population size. Coral reef fishes add some interesting variations and confirmations to the basic rules of mating systems as there can be dramatic differences within species from place to place because of changes in resource distribution and population density, and individuals often have the option of changing sex or sexual allocation over the course of their lives. One of the first generalizations to come out of studies in behavioral ecology of reef fishes was the importance of local density in determining mating systems. It demonstrated the importance of density in spawning site defense by individual males, and the switch from monogamous to more polygynous mating systems with increasing density. Population density also appears to interact with female spawning locations, especially whether females migrate to spawn or spawn within feeding territories. For small reef fishes that free-spawn (release pelagic eggs), two general patterns emerge. For many species, individuals migrate daily to the downcurrent edge of the reef to spawn for a limited time, determined by tide, time of day, or both. For some species, especially on patch reefs, if the number of individuals is relatively small, this group operates as a harem, with one dominant male and a group of females. Moreover, in families capable of hermaphroditism, protogyny—sex change from female to male—is often observed.