Interspecific aggression between two parrotfishes (Sparisoma, Scaridae) inthe Florida Keys

When resources are economically defendable, interspecific aggression may oc cur when one species attempts to use the defended resources to the detrimen t of the defending species. In the Florida Keys, we investigated vigorous a nd frequently observed aggression between the Redband Parrotfish, Sparisoma aurofrenatum, and the Redtail Parrotfish, Sparisoma chrysopterum, along wi th microhabitat overlap and foraging overlap. Sparisoma chrysopterum home r anges extensively overlap S. aurofrenatum territories. Both parrotfishes ar e found over and feed upon Halimeda opuntia, a green calcareous alg a, sign ificantly more than all other microhabitats. Interspecific aggression by th ese parrotfishes is primarily directed toward confamilials. Extensive overl ap in distributions combined with overlap in microhabitat and foraging beha vior likely play a role in fostering the disproportionately high interspeci fic aggression observed between these two parrotfishes in the Florida Keys.