Interspecific Aggression between Two Parrotfishes (Sparisoma, Scaridae) in the Florida Keys

When resources are economically defendable, interspecific aggression may occur when one species attempts to use the defended resources to the detriment of the defending species. In the Florida Keys, we investigated vigorous and frequently observed aggression between the Redband Parrotfish, Sparisoma aurofrenatum, and the Redtail Parrotfish, Sparisoma chrysopterum, along with microhabitat overlap and foraging overlap. Sparisoma chrysopterum home ranges extensively overlap S. aurofrenatum territories. Both parrotfishes are found over and feed upon Halimeda opuntia, a green calcareous alga, significantly more than all other microhabitats. Interspecific aggression by these parrotfishes is primarily directed toward confamilials. Extensive overlap in distributions combined with overlap in microhabitat and foraging behavior likely play a role in fostering the disproportionately high interspecific aggression observed between these two parrotfishes in the Florida Keys.

Fig. 1.

Mean frequency (%) of observed behaviors of Sparisoma aurofrenatum and Sparisoma chrysopterum TPs in selected activities. Vertical bars show + 1 SE. Both intra- and interspecific behaviors included chases, displays, and flights. White bars = S. aurofrenatum, striped bars = S. chrysopterum (n = 11). Differing numbers above bars indicate significant differences with Tukey's test (P < 0.05)

Fig. 2.

Feeding and microhabitat use behavior and percent cover of different microhabitats on Sparisoma aurofrenatum territories. Vertical bars show + 1 SD. Sample sizes = 11 for feeding and microhabitat observations and 10 for percent cover estimates

Fig. 3.

Feeding and microhabitat use behavior and percent cover of different microhabitats on Sparisoma chrysopterum home ranges. Vertical bars show + 1 SD. Sample sizes = 11 for feeding and microhabitat observations and 10 for percent cover estimates

Fig. 4.

(A) Mean number of aggressive encounters by Sparisoma aurofrenatum TPs during 15-min observations (n = 11). (B) Families of fishes encountered by S. aurofrenatum TPs during 15-min observations (n = 10). Vertical bars show + 1 SD. For (A) and (B), the categories S. aurofrenatum and Sparisoma chrysopterum refer to TPs. Initial phases of these species are included in the “other Scaridae” category, which also includes Sparisoma rubripinne, Sparisoma viride, Midnight Parrotfish, Scarus coelestinus, Rainbow Parrotfish, Scarus guacamaia, Striped Parrotfish, Scarus iserti, and Queen Parrotfish, Scarus vetula

Fig. 5.

(A) Mean number of aggressive encounters by Sparisoma chrysopterum TPs during 15-min observations (n = 11). (B) Families of fishes encountered by S. chrysopterum TPs during 15-min observations (n = 10). Vertical bars show + 1 SD. For (A) and (B), the categories Sparisoma aurofrenatum and S. chrysopterum refer to TPs. Initial phases of these species are included in the “other Scaridae” category, which also includes Sparisoma rubripinne, Sparisoma viride, Blue Parrotfish Scarus coeruleus, Scarus guacamaia, Scarus iserti, and Scarus vetula

Accepted: 06 Dec 1999