Comparative resource use by juvenile parrotfishes in the Florida keys

Abstract

Many parrotfishes (Scaridae) co-occur in mixed-species aggregations as juveniles, but diverge in resource use and social structure as adults. Focal observations of 3 juvenile parrotfishes (Scarus coeruleus, Sparisoma aurofrenatum, Sparisoma viride) were conducted on inshore patch reefs in the Florida Keys to examine feeding rates, food type, habitat use, and aggressive interactions. All species overlapped extensively in their use of space and food. Home ranges physically overlapped, and the proportion of microhabitats present within home ranges was similar for all species. Home range size increased with body size for S. coeruleus and S. aurofrenatum. Diets of all species were extremely similar. All fed selectively from the available foods and fed primarily (>50 % total bites) on the calcareous macroalga Halimeda opuntia 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 occasionally grunts and wrasses. S, aurofrenatum and S. viride were most aggressive toward conspecifics. Aggressive interactions with adult parrotfishes were rare. Both Sparisoma spp. were chased more often by damselfishes than any other species. These findings support the growing body of evidence that herbivorous fish do not feed randomly from all potential foods. The aggressive interactions observed among juvenile parrotfishes are likely affecting their use of resources and may act as a precursor to subsequent territoriality as adults.