Description of larval development of the red hind, Epinephelus guttatus, and the spatio-temporal distributions of ichthyoplankton during a red hind spawning aggregation off La Parguera, Puerto Rico.

摘要

Coral reef fishes exist as open populations, with connections among areas maintained by pelagic larval dispersal. Key questions are the extent and variability of these connections and at what scale are local populations self-recruiting. The discrete spawning behavior of the red hind was used to address these questions off southwest Puerto Rico. Laboratory larval-rearing indicated the conditions under which development may occur, the timeframe for interpreting the extent of larval swimming and feeding, and descriptions to aid identification of field-caught individuals. At 26.2–25°C, red hind eggs (0.95mm) hatched in 24 hr. Early free embryos were positively buoyant. At 45 hr (2.28mm TL) they could change and maintain vertical position. Larvae at 70 hrs (2.48mm TL) had well-developed pectoral fins, a broadened caudal finfold, and a fully-functional mouth and digestive system. Larvae were capable of swimming and searching for food. Larvae (2.91 mm TL) showed no sign of urostyle flexion at 82 hr, when the last specimens died. Spatio-temporal variations in egg abundance indicated red hind spawning in 1997 occurred around full moon in February, when the mixed layer showed minimum temperatures (25.5–26°C) and highest chlorophyll-a concentrations over the outer shelf, where spawning occurs. Larval abundance of all taxa declined offshore (out to 22 km) and no advanced Epinephelinae larvae were recorded. Rather, a strong westward current resulting from strong winds and far-field mesoscale eddies impinging on the coast is thought to have rapidly dispersed eggs and larvae to the west, but also to have kept larvae near the shelfedge for potential retention at sites along the west coast. During late March/early April there was a period of calm currents followed by a current reversal as smaller eddies were set up along the southwest coast. At this time there were large increases in the number of pre- and especially post-flexion larvae encountered across all taxa, suggesting these currents enhanced larval retention of species spawning at this time. Larval data and current flows indicate that recruitment should be variable depending upon immediate conditions and that retention within Puerto Rico could be both local or up to 60km downstream, with some further transport possible.