In open populations, larval settlement dynamics may be an important determinant of subsequent distribution and abundance of juveniles and adults. A correlative and experimental study of larval settlement in the domino damselfish Dascyllus albisella Gill onto coral reefs off Oahu, Hawaii, was conducted by considering settlement patterns and the extent of larval habitat choice. Conspecific groups live in transient groups on small, branching coral heads and do not interact with adults. By repeatedly censusing a natural patch reef over two summers, and employing a multifactorial experiment on a grid of isolated coral heads, I identified conspecific juvenile density as a major factor influencing settlement. A series of field and laboratory binary choice experiments confirmed that larvae preferred to settle with larger groups of conspecific juveniles than with single conspecifics, empty coral heads or confamilial groups. The laboratory experiment also indicated that preferences may have been established through visual cues, suggesting that vision may supplement chemical cues in facilitating larval settlement preferences. On a larger spatial scale, patterns of settlement at five sites covering 25 km of Oahu's coastline suggested that two distinct peaks of larval settlement occurred in the summer of 1989 and that settlement was synchronous among these sites. It appears that settlement patterns of a small (within-reef) scale are influenced by larval habitat preferences, while settlement on a larger scale (several reefs) may be synchronized as a result of oceanographic factors or spawning patterns.
