Direct Evidence of a Biophysical Retention Mechanism for Coral Reef Fish Larvae

We examine the hypothesis that reef fish larvae have some direct influence on
their own dispersal and ability to recruit to their natal reef by tracking
cohorts of bicolor damselfish (Stegastes partitus) from hatching to settlement
onto the reef, about 30d later. We conducted high-resolution sampling during
two consecutive years in a small area (15 km x 20 km) off the west coast of
Barbados, extending from depths of 0 to 100 m. Observations of discrete
stage-specific larval patches of mean size of 29.4 and 13.2 km^2 for preflexion
(1-5-d old) and flexion/postflexion (>5-d old) stages extending ca. 30 m in the
vertical indicated that larvae initially dispersing as patches tend to stay in
coherent patches throughout their pelagic duration. Highest concentrations of
preflexion larvae within a patch were in the upper 20 m, while those of older
larvae were always deeper. Downward migration of about 60 m throughout ontogeny
within stratified currents represented a retention mechanism for locally
spawned larvae. Most of the variability in estimated retention rates between
daily cohorts occurred during the earliest stages as a result of the dynamic
nature of surface currents experienced by larvae prior to the onset of vertical
migration. Differences in residence time between experiments were consistent
with observed intermonthly variability in recruitment strength, implying that
pelagic processes can explain recruitment rates. These results provide
empirical evidence for larval retention of coral reef fishes and stress the
role of active behavior in larval transport. "Our main objective was to
investigate the mechanism by which coral reef fish larvae may maximize their
return to the settlement habitat of the natal population. For this purpose, we
needed to determine the role of larval behavior in controlling dispersal and
horizontal advection and it relationship to the island-scale flow patterns."

Spatial Data Organization Information - Indirect Spatial Reference: Barbados,
West Indies, the Lesser Antilles, vertical layers in the water column at 20-m
intervals from 0-100 m.
Direct Spatial Reference: Raster Raster Object

Type: Point Spatial Reference Information - Horizontal Coordinate System
Definition - Geodetic Model: