The role of habitat preferences and social organization in determining spatial distributions has been a much debated topic in ecology. To determine whether and how individual behavior and social organization influence spatial distributions of arc-eye hawkfish (Paracirrhites arcatus) on both local and lagoon-wide scales, a series of reef surveys and field experiments were conducted. Reef surveys revealed P. arcatus display strong preferences for branching corals in the genus Pocillopora and more specifically for certain morphological attributes within the group of Pocillopora species. These habitat preferences explained ~62% of the variation in abundance of this species on a lagoon-wide scale. This derived relationship between the numbers of hawkfish and Pocillopora predicted 86% of the spatial variation in abundance of hawkfish at other locations during the subsequent year. Individual behavior and social organization were also found to have significant impacts on hawkfish distributions. A colonization experiment was established to explore preferences of hawkfish for different types of Pocillopora in the absence of established social structures; all colonizers resided on the highly favored corals. While this experiment revealed strong preference for certain Pocillopora corals, surveys illustrate that the majority of hawkfish do not reside on these preferred corals. To address this, another experiment tested the impact of social organization on hawkfish distribution. When highly preferred corals were added to areas occupied by established harems, hawkfish significantly modified the amount of time spent as well as the number of aggressive acts and prey attacks made from these corals. These results illustrate the critical need to investigate more thoroughly the impacts of individual behavior and social organization on spatial distributions.
Thesis or Dissertation
Department of Ecology, Evolution and Marine Biology, UC Santa Barbara