Settlement patterns and presettlement behavior of the naked goby,Gobiosoma bosci,a temperate oyster reef fish

Dispersion, distribution, development and feeding incidence of larvae of the naked goby,Gobiosoma bosci (Lacepéde), were examined for linkages between larval behavior while near the reef surface and later patterns of settlement and recruitment. Field sampling and experiments were conducted during the summers of 1988 and 1989 in the Flag Pond oyster reef along the western shore of the Chesapeake Bay near Camp Conoy, Maryland, USA. Results indicated that prior to settlement most demersal larvae aggregate in shoals and exhibit distinct microhabitat preferences on the reef. In a field experiment, larvae settled both during the day and at night. Dispersion at settlement was aggregated, suggesting that demersal shoaling influences settlement patterns in this species. The distribution of demersal larvae also indicated that larval swimming behavior is sufficiently strong to permit active control of position on reefs. Large demersal larvae settled rapidly when brought to the laboratory, but small larvae in demersal shoals appeared to require additional growth and morphological development prior to settlement. Development of the pelvic fins, used by juveniles and adults for perching on the substrate, may be a good indicator of competence to settle in this species. The adaptive significance of demersal shoaling by small larvae of the naked goby, and the fate of these larvae, remains perplexing because the low feeding rates found for larvae shoaling near the reef surface should slow or prevent the growth and development required prior to settlement. Observations made by other authors indicate that demersal shoaling and the use of water directly overlying reefs may be common behaviors of temperate and tropical reef fishes.