Comparative resource use by juvenile parrotfishes in the Florida Keys

Many parrotfishes (Scaridae) co-occur in mixed-species aggregations as juve niles, but diverge in resource use and social structure as adults. Focal ob servations of 3 juvenile parrotfishes (Scarus coeruleus, Sparisoma aurofren atum, Sparisoma viride) were conducted on inshore patch reefs in the Florid a Keys to examine feeding rates, food type, habitat use, and aggressive int eractions. All species overlapped extensively in their use of space and foo d. Home ranges physically overlapped, and the proportion of microhabitats p resent within home ranges was similar for all species. Home range size incr eased with body size for S. coeruleus and S, aurofrenatum. Diets of all spe cies were extremely similar. All fed selectively from the available foods a nd fed primarily (>50% total bites) on the calcareous macroalga Halimeda op untia despite its potentially high energetic costs of procurement. low food value. and predicted avoidance. Focal individuals interacted aggressively with conspecifics, other juvenile parrotfishes, damselfishes, and occasiona lly grunts and wrasses. S. aurofrenatum and S, viride were most aggressive toward conspecifics. Aggressive interactions with adult parrotfishes were r are. Both Sparisoma spp, were chased more often by damselfishes than any ot her species. These findings support the growing body of evidence that herbi vorous fish do not feed randomly from all potential foods. The aggressive i nteractions observed among juvenile parrotfishes are likely affecting their use of resources and may act as a precursor to subsequent territoriality a s adults.