Successful recruitment in reef fish requires the supply of larvae to appropriate settlement sites and survival through various juvenile stages. This project examined the habitat use of the white grunt, Haemulon plumieri, in southwest Puerto Rico, identified settlement sites, and used visual censuses over small temporal and spatial scales to document variability in recruitment to a Thalassia-Acropora cervicornis habitat. Newly-settled white grunts (≤1.5 cm TL) recruited from December to September with peaks in January, May, and July-September. The French grunt, H. flavolineatum, showed similar recruitment peaks in May and July-September. Settlement peaks persist as increases in mean densities over a period of months. Experimental manipulations altered conditions of similar settlement sites: a) A. cervicornis with small juveniles, b) unoccupied A. cervicornis, c) A. cervicornis from which residents had been recently removed, and d) coral colonies occupied by older juveniles. Out of 1496 white grunts, significantly more (85.7%) recruited to coral colonies with early stage juveniles than to (b) 4.5%, (c) 8.2%, or (d) 0% (ANOVA, P<0.0001). Recruitment of all newly settled haemulids (4610 total) followed the same pattern: 87.4% to A. cervicornis with young resident juveniles. Interestingly, habitat selection by newly settled white grunts showed density dependence, resulting in significantly greater dispersion to other juvenile habitats during recruitment peaks. In March (low recruitment) 92.5% recruited to A. cervicornis coral colonies with resident juveniles compared to months with high recruitment, such as May (54.1%), July (44.2%), and August (51.1%). These results support the hypotheses that 1) settlement of white grunts and other haemulids is facilitated rather than inhibited by the presence of earlier settlers; 2) capacity of the habitat is limited and additional settlers are displaced to sub-optimal habitats; this displacement was also documented during disturbance that reduced the amount of optimal habitat; 3) settlement of white grunts in La Parguera occurs December through September with peaks that can be traced into sequential size classes; 4) within months (~3) post-settlement processes (mortality or ontogenetic migration) modify the patterns of white grunt distributions that were set at settlement.

email: ron.hill@noaa.gov