Yearly and inter-island variation in the recruitment dynamics of the bluehead wrasse ( Thalassoma bifasciatum, Bloch)

Abstract

The summer spawning and settlement patterns of Thalassoma bifasciatum (Bloch) in the Virgin Islands were back-calculated using daily increments of otoliths from recruits. Recruits were collected in July of each year of 1991–1993 from two sites on St. Croix, one on St. John, and one on Virgin Gorda. Spawning and settlement of T. bifasciatum exhibited slight lunar periodicity, with a tendency for more spawning around the last lunar quarter and higher settlement around the first lunar quarter. Settlement patterns failed to exhibit the brief episodes of intense settlement previously reported for this species, although weak pulses of settlement spread over several days were evident. Only in 1993 were settlement pulses coincident among sites, and this synchronous settlement was probably driven by a patch of water > 650 km 2 which was rich in larvae. In contrast to studies of this species at other sites, very few individuals recruiting to the Virgin Islands delayed metamorphosis. We conclude that settlement of this species in the Virgin Islands is patterned by the interaction of a relatively fixed larval duration with unpredictable oceanographic processes acting to transport larvae.