Habitat distribution patterns of the redtail parrotfish Sparisoma chrysopterum in the Northern US Virgin Islands

Abstract

Coral reef fishes often undergo ontogenetic shifts in habitat, migrating from nearshore, non-coral reef habitats as juveniles to coral reef environments as adults. Parrotfishes fill essential ecological roles in coral reef ecosystems and are an important component of commercial and recreational fisheries in the US Caribbean, where redtail parrotfish are frequently landed. Little is known about abundance and distribution patterns of juvenile redtail parrotfish in most of their range. This study conducted underwater surveys around St. Thomas using random stratified sampling of 3 habitat types: seagrass fringe, hardbottom, and rocky reef. Surveys assessed redtail parrotfish density and habitat characteristics, including biological substrate cover, topographic complexity, and depth. Overall, juvenile redtail parrotfish had the highest density in hardbottom, followed by rocky reef, then seagrass fringe. Topographic complexity significantly differed between the habitat types and was found to be a significant predictor of redtail parrotfish density. Hardbottom and rocky reef were dominated by turf algae and Dictyota spp., though hardbottom had significantly higher Dictyota spp. cover and lower turf algae cover than rocky reef. When data from all habitat types were pooled, the presence of Dictyota spp. was found to be a significant predictor of redtail parrotfish density. Trends found across the three habitats surveyed indicate that an ontogenetic habitat shift from nearshore non-coral reef habitats to coral reefs occurs in redtail parrotfish. The results of this study provide an enhanced understanding of habitat selection by juvenile redtail parrotfish, highlighting the importance of considering non-reef habitat types in future fishery management plans.