Variability in Recruitment of Coral Reef Fishes: The Importance of Habitat at Two Spatial Scales

Abstract

We investigated spatial and temporal variability in recruitment of coral reef fishes to ST. Croix, U.S. Virgin Islands, with the goal of assessing the importance of habitat and physical oceanogrpahic processes in determining patterns of distribution at two spatial scales. Recruitment was monitored visually each month, using SCUBA, at sites spaced equally around the island and on transects within each site. Spatial patterns of distribution were consistent within seasons and between years at both spatial scales. Although recruitment showed a seasonal pattern, there were few inter—annual differences at any spatial scale. At the largest scale, recruitment varied significantly among sites around the island, and a unique pattern of distribution was observed. On the windward shore, recruitment ranged from hig on the eastern (upcurrent) end to low on western end of the island. Recruitment showed the opposite pattern on the leeward shore, ranging from low on the eastern end to high on the western end. At the transect scale, certain features of the habitat significantly predicted recruitment density. None of the microhabitat features that prerdicted recruitment at the small scale could explain patterns of recruitment observed at the large scale. In contrast, physical process affecting larval availability or transport were more important than habitat in determining the spatial patterns of recruitment at this scale. Thus, physical oceanographic processes appeared to be responsible for patterns of recruitment to the two shores of St. Croix, and to sites along those shores. Despite consistent patterns of recruitment to sites, habitat selection did not appear to be important at the site scale. Once delivered to a site, however, settlers or new recruits distributed themselves based on habitat preferences.