Effect of decreasing reef complexity on damselfish territory size

Widespread disease, recurring cold events, and severe storms have largely reduced the once expansive branching coral communities to areas of relatively featureless rubble.  It is still unclear how overall complexity loss in Dry Tortugas National Park (DTNP), one of the least disturbed coral reef systems in North America, may affect fish density, behavior, and territory. Our study evaluated differences in density, chase encounters, and territory size of dusky, beaugregory, and three spot damselfish on coral rubble and nearby patch reefs within DTNP.  Damselfish populations were encountered on both patch reef and coral rubble sites, with differences in distribution and abundance found between species and habitat types. For all three species, the greater density occurred on the patch reef. Increased density on patch reef accounted for a larger number of chase encounters; however, no significant difference was found due to habitat type or species. Although all three damselfish species defended a larger territory size on coral rubble than patch reef, significant differences were only detected among dusky damselfish.  Damselfish influence on reef structure and ecology suggests that our data can provide for interpretations of how changing habitat complexity has affected damselfish behavior, activity, and interspecific competition in DTNP.