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Herbivore distribution can impact community structure and ecosystem function. On coral reefs, herbivores are thought to play an important role in promoting coral dominance, but how they are distributed relative to algae is not well known. Here, we evaluated whether the distribution, behavior, and condition of herbivorous fishes correlated with algal resource availability at six sites in the back reef environment of Moorea, French Polynesia. Specifically, we tested the hypotheses that increased algal turf availability would coincide with (1) increased biomass, (2) altered foraging behavior, and (3) increased energy reserves of herbivorous fishes. Fish biomass and algal cover were visually estimated along underwater transects; behavior of herbivorous fishes was quantified by observations of focal individuals; fish were collected to assess their condition; and algal turf production rates were measured on standardized tiles. The best predictor of herbivorous fish biomass was algal turf production, with fish biomass increasing with algal production. Biomass of herbivorous fishes was also negatively related to sea urchin density, suggesting competition for limited resources. Regression models including both algal turf production and urchin density explained 94 % of the variation in herbivorous fish biomass among sites spread over ~20 km. Behavioral observations of the parrotfish Chlorurus sordidus revealed that foraging area increased as algal turf cover decreased. Additionally, energy reserves increased with algal turf production, but declined with herbivorous fish density, implying that algal turf is a limited resource for this species. Our findings support the hypothesis that herbivorous fishes can spatially track algal resources on coral reefs.

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Abstract.-Size can play an important role in determining reproductive success through the establishment of dominance hierarchies and mate selection. We explored the relationship between size of individuals and courtship success in the kelp perch, Brachyistius frenatus, off the coast of southern California at Santa Catalina Island. Courtship displays were timed and the length of the interaction was used as a proxy for courtship success. In addition, we observed how much of their time individuals spent performing different activities throughout the day in two adjacent habitats dominated by different macroalgae. We found that body size played a significant role in determining the success of courtship. Large males were slightly more successful than small males, but the male: female size ratio was the best predictor of mating success of male B. frenatus, with males that were large relative to the female they were courting being most successful. Time allocated to different activities varied significantly with time of day and habitat. A greater proportion of time was spent on foraging in the morning than in the afternoon, and females spent more of their time foraging than did males. Behaviors other than foraging were only observed in one habitat type (understory algae) and courtship behavior was only observed during the afternoon. Smaller males tended to spend more time searching for receptive females than did larger males.